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Bacterial mastitis in dairy cow is often caused by a combination of bacterial infections, such as Escherichia coli, Staphylococcus aureus, and Streptococcus agalactiae. Currently, there is no effective vaccine against the disease. Therefore, we constructed a recombinant subunit vaccine by fusing gene fragments of E. coli OMPA and OMPC, S. aureus EBPS, and S. agalactiae PGK, AP1, AP2, and FBSA. These gene fragments were combined into three fusion proteins: OMPAC, EBPSs, and PAPF. Mice were immunized with the three fusion proteins either alone or in combination. The test results showed that immunization with OMPAC, EBPSs, and PAPF individually or in combination could induce high titers of antibodies in the mice. Additionally, 21 days post-immunization, IFN-γ levels were significantly increased in all groups of mice, suggesting that immunization with OMPAC, EBPSs, and PAPF, whether alone or in combination, was effective in inducing antibody production. This indicates that OMPAC, EBPSs, and PAPF were effective in inducing both humoral and cellular immunity in mice. Furthermore, immunization with OMPAC, EBPSs, and PAPF individually or in combination were effective in protecting mice from E. coli, S. aureus, and S. agalactiae infections. Importantly, a mixture of the three fusion proteins was relatively safe for pregnant female mice. In conclusion, we successfully constructed and expressed recombinant subunit vaccines of OMPAC, EBPSs and PAPF and verified that these vaccines rapidly induced high levels of specific antibodies while reducing bacterial loads in the organs of mice. This lays the theoretical foundation and data support for the development of novel subunit vaccines against mastitis in dairy cows., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

Streptococcus suis (S. suis) is a major pathogen that poses a long-term threat to swine populations. Due to its foodborne transmission, this pathogen has recently emerged as a leading cause of meningitis in humans, presenting a significant public health challenge. Currently, no vaccine is available to combat this disease, particularly a universal vaccine capable of addressing multiple subtypes of S. suis. In this study, we developed a universal live vaccine candidate against multiple serotypes S. suis based on the polyvalent antigen protein SE6. A live Salmonella Choleraesuis (S. Choleraesuis) vector was employed for the production and in vivo delivery of the polyvalent antigen. The SE6 protein was efficiently expressed within the S. Choleraesuis vector and delivered to the host's lymphatic system. The antiserum of mice immunized with SE6-delivering S. Choleraesuis vector produced a broader and potent opsonophagocytic response against multiple serotypes of S. suis. Finally, the SE6-delivering S. Choleraesuis vector demonstrated high efficacy in providing protection against S. suis serotypes 2, 7, and 9 in vivo., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Group B Streptococcus (GBS) is a major cause of fetal and neonatal mortality worldwide. Many of the adverse effects of invasive GBS are associated with inflammation; therefore, understanding bacterial factors that promote inflammation is of critical importance. Membrane vesicles (MVs), which are produced by many bacteria, may modulate host inflammatory responses. While it is known that mice injected intra-amniotically with GBS MVs exhibit large-scale leukocyte infiltration, preterm birth, and subsequent fetal death, the immune effectors driving this response remain unclear. Here, we hypothesized that THP-1 macrophage-like cells respond to GBS-derived MVs by producing proinflammatory cytokines and are recognized through one or more pattern recognition receptors. We show that THP-1s produce high levels of neutrophil- and monocyte-specific chemokines in response to MVs derived from different clinical isolates of GBS. Using antibody microarrays and multiplex Luminex assays, we found that GBS MVs elicit significantly ( p < 0.05) higher levels of CCL1, CCL2, CCL20, CXCL1, CXCL10, and IL-1β relative to untreated THP-1s. Using chemical inhibitors in combination with caspase-1 activity assays and Luminex assays, we further demonstrate that GBS MVs upregulated IL-1β production in a caspase-1 and NLRP3-dependent manner, ultimately identifying NLRP3 as a sensor of GBS MVs. These data indicate that MVs contain one or more pathogen-associated molecular patterns that can be sensed by the immune system and show that the NLRP3 inflammasome is a novel sensor of GBS MVs. Our data additionally indicate that MVs may serve as immune effectors that can be targeted for immunotherapeutics.

Aquaculture industry frequently encounters disease outbreaks, high mortalities, as well as emergence of new pathogens due to its intensification. Streptococcus agalactiae (Lancefield's group B Streptococcus) is an important pathogen extensively causing infectious disease in tilapia resulting in huge economic loss and mortality. To date, vaccination has proved to be successful in defending against infectious diseases prevailing among farmed fish species. This study aimed to develop an S. agalactiae inactivated vaccine (SAIV) using molecular adjuvants, flagellin and tilapia interferon gamma (IFN-γ), and to assess the generated immune response and protective efficacy of the adjuvant incorporated vaccine against S. agalactiae infection in Nile tilapia. The fish were vaccinated with SAIV together with either flagellin or IFN-γ and both together by intraperitoneal injection. The vaccinated fish were challenged with a virulent strain of S. agalactiae on day 36 and monitored for 3 weeks to assess cumulative mortality. The results showed that the vaccine offered significant protection with relative percentage survival (RPS) of 59.37%, 71.87%, and 81.25% observed for bacterin vaccine adjuvanted with flagellin, IFN-γ and both, respectively, with an RPS of 15.62% for the unadjuvanted bacterin control group after challenge with S. agalactiae. The vaccine induced specific IgM antibodies against S. agalactiae in the vaccinated groups, and the antibody response was significantly increased following booster vaccination in the fishes administered with vaccine adjuvanted with flagellin, IFN-γ and both. Furthermore, after vaccination, MHC-II and IgM gene expression was found significantly upregulated in head kidney and spleen, in line with an elevated specific IgM titer. Innate immune parameters including catalase, lysozyme, superoxide dismutase, myeloperoxidase, and bactericidal activities were significantly increased in fishes immunized when compared with the unvaccinated controls (P < 0.05). Histopathological examinations of tissue sections of the head kidney, spleen, liver, kidney, gills, and brain were performed on vaccinated and non-vaccinated fish which showed mild infiltrations. In conclusion, flagellin and IFN-γ have shown potential for use as molecular adjuvants to enhance the efficacy of fish vaccines against S. agalactiae infections., Competing Interests: Declarations. Conflict of interest: The authors declare no competing interests., (© 2025. The Author(s), under exclusive licence to Springer Nature B.V.)

Background: Group B streptococcus (GBS) is a commensal bacterium of the digestive and genital tracts that can occasionally cause maternal and neonatal disease. GBS is particularly a burden in low-resource settings, where infections with HIV are also highly prevalent. This study investigates the impact of HIV status on GBS colonization and antibody levels., Methods: In Uganda, 90 nonpregnant women of childbearing age were followed for 3 months. Every 2 weeks, rectal and vaginal swabs were tested for GBS, and vaginal cups and blood were collected for measurement of GBS capsular polysaccharides (CPS) IgG using standardized assays., Results: Twenty-six of 90 women were living with HIV. Almost 51/90 women were GBS colonized at 1 or several visits. GBS colonization fluctuated in the rectal and vaginal sites. Most prevalent serotypes were Ia and III, with 33 individuals carrying different serotypes over time. Serum and vaginal CPS-IgG levels were stable over 12 weeks. In serum, for serotypes Ib-V, the geometric mean concentration (GMC) of CPS-IgG did not differ between HIV+ and HIV- participants. However, the GMC for serum CPS-Ia-IgG in the HIV+ group was 2.5 times lower than in the HIV- group (P = 0.038). Vaginal CPS-IgG was measurable in 5/26 (19%) HIV+ participants, and 32/64 (50%) HIV- participants., Conclusions: Despite fluctuating GBS colonization, antibody levels remained stable over 12 weeks. The level of CPS-Ia-specific IgG in serum was lower in women with HIV than in those without HIV. Vaginal CPS-specific IgG was not measurable in 81% of individuals with HIV., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Acanthopagrus latus (yellowfin seabream) is an economically important fish in the southeast coastal sea of China. Its slower growth rate makes it more prone to diseases in the cultivation period, leading to substantial economic losses. Epidemiological investigations have indicated that Streptococcus agalactiae is one of the most common Gram-positive pathogens, which have garnered increasing attention due to its high contagion and lethality rates in A. latus. In this work, an infection model of yellowfin seabream was established with an intraperitoneal injection of S. agalactiae. Clinical sign observations and various analyses, including histological examination, serum biochemical index assessment, immune-related enzyme level measurement, and transcriptome analysis of tissues (liver and intestine) with obvious clinical signs, were conducted for revealing the effects of S. agalactiae infection and immune response mechanisms in yellowfin seabream. The results indicate that evident clinical signs and multi-tissue damages with the notable changes in indices and significant increase in immune-related enzyme levels in the serum occurred in infected fish. RNA sequencing analysis identified 1130 differentially expressed genes (DEGs) in the liver and 1218 DEGs in the intestine, which were involved in multiple immune- and metabolism-related pathways via KEGG enrichment analysis. The transcriptomic results were further corroborated by quantitative real-time RT-PCR (qRT-PCR) tests of some specific immune-related genes. These findings provide new insights into the molecular immune mechanisms in yellowfin seabream following S. agalactiae infection and offer valuable reference data for disease prevention and molecular breeding (i.e., selective breeding through developing molecular markers of key genes)., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

Streptococcus suis serotype 2 (SS2) is an emerging zoonotic agent responsible for a variety of diseases. The septicemia caused by SS2 suggests that it can evade the bactericidal effects of innate immune cells. However, the mechanisms by which SS2 evades innate immunity remain largely unknown. Neutrophils are critical components of innate immunity for antimicrobial defense. In this study, we identified a cell surface protein (CSP) insertion mutant in an SS2 transposon mutant library that significantly induces neutrophil extracellular traps (NETs) and shows poor survival compared to the parent SS2 in the bloodstream. CSP deletion mutant (ΔCSP) was constructed and it exhibits a defective polysaccharide capsule and enhanced biofilm formation. Although ΔCSP induces increased NET release and ROS formation, its survival and proliferation within neutrophils and NETs are significantly reduced. Additionally, ΔCSP stimulates extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in neutrophils, which may enhance neutrophil bactericidal activity. Importantly, purified polysaccharide capsule from SS2 can inhibit neutrophil bactericidal effects. This study identifies bacterial virulence factors that prevent SS2 clearance by neutrophils, offering potential antigens or drug targets for the prevention and control of swine streptococcosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

Background: Streptococcus agalactiae poses a significant threat to neonatal health, causing morbidity and mortality when transmitted from the maternal vagina to the newborn's respiratory tract. Among its various strains, serotype III is predominant in severe neonatal infections in Asia. However, the mechanisms of pathogenesis and host responses underlying serotype-specific disease outcomes remain poorly understood., Methods: This study employed 2D airway epithelial organoids as a host model to investigate the progression of S. agalactiae respiratory tract infections across four serotypes. RNA and ATAC analyses were used to identify differentially expressed genes and related pathways., Results: S. agalactiae infection triggered inflammatory responses in differentiated airway epithelia, particularly increasing the expression of genes linked to innate immunity. Serotype III elicited stronger immune responses compared to other serotypes. The SLC2A3 gene demonstrated upregulated expression and increased chromatin accessibility specific to serotype III infection., Conclusions: Neonates predominantly clear S. agalactiae infections through immune detection and opsonophagocytosis. These findings highlight the importance of patient triage based on serotype variations. Developing therapeutic candidates targeting invasive serotypes to enhance OPK titers may be crucial. Furthermore, serotype III infection may induce apoptosis via Ferroptosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In recent years, increased numbers of severe Streptococcus dysgalactiae subsp. equisimilis (SDSE) infections, including necrotizing soft tissue infections (NSTIs), have been reported. One of the main virulence factors of SDSE is streptokinase (Ska). Ska promotes bacterial spread in the tissue through Ska-plasminogen interactions and subsequent activation of plasminogen to plasmin. In this study, the impact of streptokinase on SDSE infections of human monocyte-derived dendritic cells (moDCs) was investigated. MoDCs were infected with SDSE strain S118 and its isogenic mutant lacking streptokinase. All infections were performed with and without human serum to compare direct Ska-mediated as well as plasmin activity-related effects. Intracellular killing kinetics, moDC viability and maturation, as well as the release of pro-inflammatory cytokines were assessed. Irrespective of the strain and experimental conditions, the bacteria were equally phagocytosed and killed. MoDCs remained viable, readily matured and secreted equal amounts of cytokines in response to S118 as well as S118Δska infections. Our data demonstrate that moDCs response to SDSE infections is not affected by Ska or its respective plasminogen activating function., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Autophagy within macrophages serves as a vital mechanism for modulating inflammatory responses to central nervous system infections caused by Streptococcus suis in both humans and swine. However, the mechanism by which autophagy regulates inflammation during S. suis infection is unclear. This study investigated the mechanism by which autophagy serves as a defense against S. suis infection in mouse microglial cells (BV2). Initially, we examined how S. suis infection triggers the adenosine monophosphate-activated protein kinase (AMPK)/ mammalian target of rapamycin (mTOR) autophagic cascade and the nuclear factor kappa B (NF-κB) and, mitogen-activated protein kinase (MAPK) inflammatory signaling pathways using western blot within BV2 cells. We then demonstrated that treatment with autophagy inhibitors, inducers, and siRNA of autophagy genes changed the levels of C-C motif ligand 2 (CCL2), CCL3, CCL5, and tumor necrosis factor α (TNF-α), and p-p65, p-p38, p- c-Jun N-terminal kinase (JNK) and p-Extracellular signal-regulated kinase (ERK) activity within BV2 cells. We found that S. suis infection induced AMPK/mTOR autophagy pathway, NF-κB and MAPK pathway in BV2 cells. Further, Autophagy inhibits S. suis infection-induced NF-κB and MAPK signaling and subsequent inflammatory factors CCL2, CCL3, CCL5, and TNF-α. Collectively, these findings suggest that AMPK/mTOR-regulated autophagy has an inhibitory effect on pro-inflammatory cytokines and chemokines by regulating the NF-κB and MAPK pathways during S. suis infection.

Streptococcus agalactiae is a major causative agent of streptococcosis in Nile tilapia ( Oreochromis niloticus ) and understanding its etiology is important to ensure the sustainable development of global tilapia farming. Our research group recently observed contrasting disease patterns in animals infected with two different S. agalactiae serotypes (Ib and III). To better understand the basis for these divergent responses, we analyzed the brain transcriptome of Nile tilapia following bacterial exposure. Our findings revealed significant variation in the expression of genes involved in immune (e.g., CD209 antigen, granulin , C-X-C motif chemokine 10, prostacyclin synthase, and interleukins) and neuroendocrine (e.g., mmp13a , mmp9 , brain aromatase , and pmch ) pathways. The serotype Ib strain seems promptly recognized by the host, triggering a potent inflammatory response, whereas the serotype III strain elicited a less immediate response, resulting in more pronounced central nervous system (CNS) symptoms and behavioral effects. To the best of our knowledge, this is the first study to show serotype-specific immune responses to S. agalactiae in Nile tilapia. These findings are important for advancing disease management and control strategies in aquaculture. Identifying different immune reactions triggered by serotypes Ib and III may assist the development of more specific approaches for preventive measures, early detection, and effective treatment against streptococcosis., Competing Interests: RJ was employed by GenoMar Genetics AS. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 Appel, Siqueira, Konstantinidis, Martins, Joshi, Pretto-Giordano, Vilas-Boas and Fernandes.)

A new blood-brain barrier (BBB) in vitro model of tilapia (Oreochromis niloticus) was successfully established by co-culture with brain microvascular endothelial cell line TVEC-01 and brain astrocyte cell line TA-02 of tilapia. Experiments with the expression levels of BBB-related genes, TEER value detection and 4-h water-leaking test have shown that the BBB in vitro model has an excellent barrier effect. In bacterial penetration experiments, the pathogenic strain of Streptococcus agalactiae was able to pass through the BBB in vitro model and initiate a series of immune responses, among which TA-02 contributed to the expression of pro-inflammatory cytokines and TVEC-01 contributed to the expression of anti-inflammatory cytokines, providing an excellent research tool and theoretical basis for further study of meningitis. Moreover, the qRT-PCR and transmission electron microscopy revealed that the pathogenic strain of S. agalactiae effectively penetrated the BBB in vitro model of tilapia during early-stage infection without destroying tight junction integrity. This suggested that, in the initial phases of infection, the pathogenic strain of S. agalactiae may breach the BBB via a transcellular pathway rather than a paracellular pathway. Summarily, a novel BBB in vitro model of tilapia was successfully designed and evaluated for reproducing alterations in brain infecting., Competing Interests: Conflicts of interest The authors declare that no conflict of interest exists., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Exposure to Group A Streptococcus leads to a broad spectrum of disease and sequelae, as the bacterium employs a wide range of virulence factors to facilitate colonization of the host, propagation and onward transmission, disrupting both innate and adaptive immune responses. The protease SpyCEP has a crucial role in contributing to bacterial immune evasion by impairing neutrophil recruitment and killing of bacteria through the cleavage of interleukin-8 (IL-8). Given this critical function, SpyCEP represents a key vaccine antigen and quantifying functional anti-SpyCEP antibodies represents not only an important marker of vaccine efficacy, but also a tool to dissect the natural immune response. Here, we report the development and characterization of an IL-8 cleavage inhibition assay to measure the function of anti-SpyCEP antibodies in human sera. The assay was demonstrated to be sensitive, highly specific, linear and reproducible, and suitable for evaluating the function of anti-SpyCEP antibodies induced in humans in vaccine clinical trials and in observational studies of natural immunity., Competing Interests: Declaration of competing interest This work was performed with funds from CARB-X and co-sponsored by GlaxoSmithKline Biologicals SA. The work was also supported by funding from the New Zealand Ministry of Health (Manatū Hauora) as part of an initiative to accelerate Strep A vaccine development for Aotearoa New Zealand. The external funders had no role in the design of the study, in the collection, analyses or interpretation of data, in the writing of the manuscript, or in the decision to publish the results. GSK Vaccines Institute for Global Health Srl is an affiliate of GlaxoSmithKline Biologicals M.C., L.R., L.M, M.I, F.B.S., D.G.M. and O.R. are employees of the GSK group of companies. FBS, MI, DGM, MC, and OR report ownership of GSK shares/share options., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Zoonotic streptococci cause several invasive diseases with high mortality rates, especially meningitis. Numerous studies elucidated the meningitis pathogenesis of zoonotic streptococci, some specific to certain bacterial species. In contrast, others are shared among different bacterial species, involving colonization and invasion of mucosal barriers, survival in the bloodstream, breaching the blood-brain and/or blood-cerebrospinal fluid barrier to access the central nervous system, and triggering inflammation of the meninges. This review focuses on the recent advancements in comprehending the molecular and cellular events of five major zoonotic streptococci responsible for causing meningitis in humans or animals, including Streptococcus agalactiae, Streptococcus equi subspecies zooepidemicus, Streptococcus suis, Streptococcus dysgalactiae, and Streptococcus iniae. The underlying mechanism was summarized into four themes, including 1) bacterial survival in blood, 2) brain microvascular endothelial cell adhesion and invasion, 3) penetration of the blood-brain barrier, and 4) activation of the immune system and inflammatory reaction within the brain. This review may contribute to developing therapeutics to prevent or mitigate injury of streptococcal meningitis and improve risk stratification., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest. The figures were created with BioRender software., (Copyright © 2024 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Dental caries is a prevalent oral disease that mainly results from Streptococcus mutans . Susceptibility to S. mutans decreased rapidly after weaning in a well-known rat model. However, owing to the lack of time to establish protective immunity ahead of challenge, the weaning rat model is suboptimal for assessing prophylactic vaccines against S. mutans infection. In this study, we found that, in adult rats, S. mutans cultured under air-restricted conditions showed dramatically increased colonization efficacy and accelerated development of dental caries compared with those cultured under air-unrestricted conditions. We propose that S. mutans cultured under air-restricted conditions can be used to develop an optimal caries model, especially for the evaluation of prophylactic efficacy against S. mutans . Therefore, we used the anti-caries vaccine, KFD2-rPAc, to reevaluate the protection against the challenge of S. mutans . In immunized rats, rPAc-specific protective antibodies were robustly elicited by KFD2-rPAc before the challenge. In addition to inhibiting the initial and long-term colonization of S. mutans in vivo , KFD2-rPAc immunization showed an 83% inhibitory efficacy against the development of caries, similar to that previously evaluated in a weaning rat model. These results demonstrate that culturing under air-restricted conditions can promote S. mutans infection in adult rats, thereby helping establish a rat infection model to evaluate the prophylactic efficacy of vaccines and anti-caries drugs.

Knowledge gaps regarding human immunity to Streptococcus pyogenes have impeded vaccine development. To address these gaps and evaluate vaccine candidates, we established a human challenge model of S. pyogenes pharyngitis. Here, we analyse antibody responses in serum and saliva against 19 antigens to identify characteristics distinguishing 19 participants who developed pharyngitis and 6 who did not. We show that pharyngitis elicits serum IgG responses to key vaccine antigens and a muted mucosal IgA response, whereas IgG responses are minimal and IgA responses more pronounced in participants without pharyngitis. Serum IgG responses to pharyngitis in adult participants resemble those in children and are inversely correlated with the magnitude of pre-existing responses. While a straightforward correlate of protection is not evident, baseline antibody signatures distinguish clinical and immunological outcomes following experimental challenge. This highlights the influence of a complex humoral imprint from previous exposure, relevant for interpreting immunogenicity in forthcoming vaccine trials., Competing Interests: Competing interests: A.C.S. and J.R.C. are co-chairs of the Australian Strep A Vaccine Initiative (ASAVI), and A.C.S. co-chairs the Strep A Vaccine Global Consortium (SAVAC). N.J.M. is co-leader of Rapua te mea ngaro ka tau, a New Zealand-based S. pyogenes vaccine initiative. M.F.G., M.P., P.R.S. and M.J.W. are inventors of patents related to S. pyogenes vaccines. The remaining authors declare no competing interests., (© 2024. The Author(s).)

Chemokines play crucial roles in the regulation of immune cell migration and development. The CXCL12/CXCR4 axis has been extensively studied in mammals, but its regulatory mechanism in teleost fish remains unclear. In this study, we used Nile tilapia (Oreochromis niloticus) as a teleost model to investigate the mediation of the CXCL12/CXCR4 axis in IgM+ B cells. Our findings demonstrate that the CXCL12/CXCR4 axis exhibits chemotactic activity on IgM+ B cells and promotes the phagocytosis of IgM+ B cells. Blocking CXCR4 severely impairs the chemotaxis and phagocytosis of IgM+ B cells in vitro and reduces the percentages and numbers of IgM+ B cells that migrate to peripheral blood after pathogen infection in vivo. This reduction in migration leads to a decrease in the inflammatory response, an increase in tissue bacterial load, and a decrease in survival rate. We also discovered that the evolutionarily conserved PI3K-AKT signaling pathway and Girdin are involved in the immune response during Streptococcus agalactiae infection. Inhibitors of the PI3K-AKT signaling pathway prevent the chemotaxis and phagocytosis of IgM+ B cells, impair the expression and phosphorylation levels of related proteins in vitro, and prevent IgM+ B cells chemotaxis into the peripheral blood after pathogen infection in vivo. Furthermore, CXCR4 blocking significantly downregulates the expression of AKT and Girdin. Overall, our study reveals the regulatory mechanism of the CXCL12/CXCR4 axis on IgM+ B cells via the PI3K-AKT signaling pathway in tilapia, suggesting that the functions of the CXCL12/CXCR4 axis in B cells may be conserved between mammals and teleost fish., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Streptococcosis is the leading bacterial disease impacting Nile tilapia (Oreochromis niloticus) and causes substantial economic losses in China. This study assessed the resistance and tolerance of three Nile tilapia (88, 99, and NG) to Streptococcus agalactiae infection. Survival rates were monitored, and samples were collected from blood, liver, and spleen at 0, 1, 2, 5, 7, and 14 days post-infection. Serum biochemical parameters, hepatic antioxidant enzymes, and the expression of related antioxidant and immune genes were measured. Results showed that strain 88 had superior resistance, with the highest survival rate, reduced liver damage, and lower alanine aminotransferase and alkaline phosphatase levels at 1 and 5 days post-infection. This strain also had higher serum cholesterol and triglyceride levels between days 5 and 14. Antioxidant activities increased in all strains post-infection, with strain 88 showing significantly higher superoxide dismutase (SOD) activity and elevated catalase (CAT) and SOD gene expressions; this indicated enhanced control of reactive oxygen species and reduced tissue damage. Additionally, strain 88 exhibited lower levels of inflammatory markers (TNF-α, IL-1β, IL-10) with higher IgM levels and superior MHC-II expression during early infection, which demonstrated a strong immune response. These results indicate that strain 88 is a promising candidate for selective breeding to improve streptococcosis resistance in tilapia., Competing Interests: Declaration of competing interest All the authors do not have any possible conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Streptococcus suis ( S. suis ) is an important swine bacterial pathogen and causes human infections, leading to a wide range of diseases. However, the role of 5'-nucleotidases in its virulence remains to be fully elucidated. Herein, we identified four cell wall-anchored 5'-nucleotidases (Snts) within S. suis , named SntA, SntB, SntC, and SntD, each displaying similar domains yet exhibiting low sequence homology. The malachite green reagent and HPLC assays demonstrated that these recombinant enzymes are capable of hydrolysing ATP, ADP, and AMP into adenosine (Ado), with the hierarchy of catalytic efficiency being SntC>SntB>SntA>SntD. Moreover, comprehensive enzymatic activity assays illustrated slight variances in substrate specificity, pH tolerance, and metal ion requirements, yet highlighted a conserved substrate-binding pocket, His-Asp catalytic dyad, metal, and phosphate-binding sites across Snts, with the exception of SntA. Through bactericidal assays and murine infection assays involving in site-mutagenesis strains, it was demonstrated that SntB and SntC collaboratively enhance bacterial survivability within whole blood and polymorphonuclear leukocytes (PMNs) via the Ado-A2aR pathway in vitro , and within murine blood and organs in vivo . This suggests a direct correlation between enzymatic activity and enhancement of bacterial survival and virulence. Collectively, S. suis 5'-nucleotidases additively contribute to the generation of adenosine, influencing susceptibility within blood and PMNs, and enhancing survival within blood and organs in vivo . This elucidation of their integral functions in the pathogenic process of S. suis not only enhances our comprehension of bacterial virulence mechanisms, but also illuminates new avenues for therapeutic intervention aimed at curbing S. suis infections.

Streptococcus agalactiae is a common pathogenic bacterium caused of streptococcosis, which has a negative impact on Nile tilapia aquaculture. Numerous vaccines have been developed recently to combat this disease, which are key components of global health efforts to prevent disease outbreaks. MONTANIDE™ IMS 1312 is a micro-emulsion recommended for immersion of fish. However, the data on the effectiveness of those immersion vaccines containing this aqueous adjuvant in fish are limited. The objective of this research was to explore the potential of MONTANIDE™ IMS 1312, an adjuvant for immersion vaccination, administered with an S. agalactiae inactivated whole-cell vaccine (SAIV) in Nile tilapia. Fish were separated into three groups: 1) fish were vaccinated by immersion vaccination with PBS (CTRL), 2) fish were vaccinated by immersion vaccination with SAIV vaccine alone (SAIV), and 3) fish were vaccinated by immersion vaccination with SAIV containing MONTANIDE™ IMS 1312. We found that the activity of several innate immunity parameters was increased significantly (P < 0.05) following the immunization. As expected, the levels of specific IgM antibody were significantly increased post-vaccination, and the highest IgM antibody levels were found in the fish vaccinated with SAIV containing MONTANIDE™ IMS 1312. Analysis of the transcriptional expression of major pro-inflammatory cytokines, as well as the presence of IgM + B cells, revealed significant increases, suggesting that Nile tilapia were able to initiate cellular immune responses following vaccination. Taken together, our results indicate that using MONTANIDE™ IMS 1312 in combination with a SAIV can induce strong protection post S. agalactiae infection. Importantly, administration of an adjuvanted immersion vaccine is safe, no side effects were observed, and it does not negatively impact fish growth. In conclusion, MONTANIDE™ IMS 1312 has the potential to be used as adjuvants for immersion vaccines against streptococcosis in Nile tilapia., Competing Interests: Declaration of competing interest Authors declare that there were no known competing financial interests to influence the work reported in this study., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Group A Streptococcus (GAS) is a versatile pathogen that targets human lymphoid, decidual, skin, and soft tissues. Recent advancements have shed light on its airborne transmission, lymphatic spread, and interactions with neuronal systems. GAS promotes severe inflammation through mechanisms involving inflammasomes, IL-1β, and T-cell hyperactivation. Additionally, it secretes factors that directly induce skin necrosis via Gasdermin activation and sustains survival and replication in human blood through sophisticated immune evasion strategies. These include lysis of erythrocytes, using red cell membranes for camouflage, resisting antimicrobial peptides, evading phagocytosis, escaping from neutrophil extracellular traps (NETs), inactivating chemokines, and cleaving targeted antibodies. GAS also employs molecular mimicry to traverse connective tissues undetected and exploits the host's fibrinolytic system, which contributes to its stealth and potential for causing autoimmune conditions after repeated infections. Secreted toxins disrupt host cell membranes, enhancing intracellular survival and directly activating nociceptor neurons to induce pain. Remarkably, GAS possesses mechanisms for precise genome editing to defend against phages, and its fibrinolytic capabilities have found applications in medicine. Immune responses to GAS are paradoxical: robust responses to its virulence factors correlate with more severe disease, whereas recurrent infections often show diminished immune reactions. This review focuses on the multifaceted virulence of GAS and introduces novel concepts in understanding its pathogenicity.

The recent global resurgence of severe infections caused by the Group A streptococcus (GAS) pathogen, Streptococcus pyogenes , has focused attention on this microbial pathogen, which produces an array of virulence factors, such as the pore-forming toxin, streptolysin O (SOT). Importantly, the interactions of SOT with human neutrophils (PMN), are not well understood. The current study was designed to investigate the effects of pretreatment of isolated human PMN with purified SOT on several pro-inflammatory activities, including generation of reactive oxygen species (ROS), degranulation (elastase release), influx of extracellular calcium (Ca 2+ ) and release of extracellular DNA (NETosis), using chemiluminescence, spectrophotometric and fluorimetric procedures, respectively. Exposure of PMN to SOT alone caused modest production of ROS and elastase release, while pretreatment with the toxin caused significant augmentation of chemoattractant (fMLP)-activated ROS generation and release of elastase by activated PMN. These effects of treatment of PMN with SOT were associated with both a marked and sustained elevation of cytosolic Ca 2+ concentrations and significant increases in the concentrations of extracellular DNA, indicative of NETosis. The current study has identified a potential role for SOT in augmenting the Ca 2+ -dependent pro-inflammatory interactions of PMN, which, if operative in a clinical setting, may contribute to hyper-activation of PMN and GAS-mediated tissue injury.

In recent years, there has been a growing focus on using herbal extracts as immune enhancers for aquatic species, replacing antibiotics. In the present study, the effects of dietary supplementation of Hericium erinaceus extract (HE) on growth, feed utilization, hematology, expression of immunity-related genes, and immune responses in Nile tilapia infected by Streptococcus agalactiae were examined. A total of 240 Nile tilapia with an average body weight of 17.28 ± 0.01 g were fed diets enriched with different levels of HE: 0 (HE0), 0.1 (HE0.1), 1.0 (HE1.0), and 5.0 (HE5.0) g/kg. The results showed that growth parameters, feed conversion ratio, and organosomatic indexes were not linearly or quadratically affected by HE supplementation. Fish fed HE0.1 and HE1.0 increased protein efficiency ratio and protein productive values with significant linear and quadratic effects of HE enrichment. In addition, dietary supplementation of HE quadratically increased whole-body protein content. Red blood cell, white blood cell, and hematocrit were linearly and quadratically increased by HE supplementation. HE also linearly and quadratically decreased LDL cholesterol and linearly decreased the total cholesterol levels. Stress markers, serum glucose, and cortisol levels were linearly and/or quadratically decreased in HE-fed fish. The relative mRNA expression of tnf-α, il-1β, il-6, and il-10 were upregulated in the HE0.1 and HE1.0 groups, while dietary supplementation of HE significantly decreased hsp70cb1 mRNA expression in all groups. After feeding dietary HE supplementation for 10 weeks, fish were intraperitoneally injected with pathogenic S. agalactiae. A high survival after challenge was found in all HE supplementation groups with the highest percent survival observed in the HE1.0 and HE5.0 groups. Our findings represent that supplementation of 1 g/kg of HE (HE1.0) could obtain the greatest effects on immunity and survival of Nile tilapia. In addition, the present study also showed that dietary supplementation of HE can improve protein utilization, hematology, expression of genes related to immunity, stress markers, and resistance of Nile tilapia against pathogenic bacterial infection., Competing Interests: Declarations Ethics approval The protocol was also approved by the Naresuan University Animal Care and Use Committee (NUACUC), Naresuan University, Phitsanulok, Thailand (NUACUC No. AG-AQ0008/2564). Additionally, all procedures involving animals were also carried out following the guidelines and recommendations of the Institute of Animals for Scientific Purpose Development (IAD), the National Research Council of Thailand (NRCT), Bangkok, Thailand (License number U1/00704/2558). Competing interests The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Nile tilapia ( Oreochromis niloticus ) and European sea bass ( Dicentrarchus labrax ) are economically significant species in Mediterranean countries, serving essential roles in the aquaculture industry due to high market demand and nutritional value. They experience substantial losses from bacterial pathogens Vibrio anguillarum and Streptococcus iniae , particularly at the onset of the summer season. The immune mechanisms involved in fish infections by V. anguillarum and S. iniae remain poorly understood. This study investigated their impact through experiments with control and V. anguillarum - and S. iniae -infected groups for each species. Blood samples were collected at 1, 3, and 7 days post bacterial injection to assess biochemical and immunological parameters, including enzyme activities (AST and ALT), oxidative markers (SOD, GPX, CAT, and MDA), and leukocyte counts. Further analyses included phagocyte activity, lysozyme activity, IgM levels, and complement C3 and C4 levels. Muscle tissues were sampled at 1, 3, and 7 days post injection to assess mRNA expression levels of 18 immune-relevant genes. The focus was on cytokines and immune-related genes, including pro-inflammatory cytokines ( TNF-α , TNF-β , IL-2 , IL-6 , IL-8 , IL-12 , and IFN-γ ), major histocompatibility complex components ( MHC-IIα and MHC-IIβ ), cytokine receptors ( CXCL-10 and CD4-L2 ), antimicrobial peptides ( Pleurocidin and β-defensin ), immune regulatory peptides ( Thymosin β12 , Leap 2 , and Lysozyme g ), and Galectins ( Galectin-8 and Galectin-9 ). β-actin was used as the housekeeping gene for normalization. Significant species-specific responses were observed in N. Tilapia and E. Sea Bass when infected with V. anguillarum and S. iniae , highlighting differences in biochemical, immune, and gene expression profiles. Notably, in N. Tilapia, AST levels significantly increased by day 7 during S. iniae infection, reaching 45.00 ± 3.00 ( p < 0.05), indicating late-stage acute stress or tissue damage. Conversely, E. Sea Bass exhibited a significant rise in ALT levels by day 7 in the S. iniae group, peaking at 33.5 ± 3.20 ( p < 0.05), suggesting liver distress or a systemic inflammatory response. On the immunological front, N. Tilapia showed significant increases in respiratory burst activity on day 1 for both pathogens, with values of 0.28 ± 0.03 for V. anguillarum and 0.25 ± 0.02 for S. iniae ( p < 0.05), indicating robust initial immune activation. Finally, the gene expression analysis revealed a pronounced peak of TNF-α in E. Sea Bass by day 7 post V. anguillarum infection with a fold change of 6.120, suggesting a strong species-specific pro-inflammatory response strategy. Understanding these responses provides critical insights for enhancing disease management and productivity in aquaculture operations.

Background: Group A streptococci (Strep A) orStreptococcus pyogenes is a major human pathogen causing an estimated 500,000 deaths worldwide each year. Disease can range from mild pharyngitis to more severe infections, such as necrotizing fasciitis, septicemia, and toxic shock syndrome. Untreated, Strep A infection can lead to the serious post streptococcal pathologies of rheumatic fever/rheumatic heart disease and post-streptococcal glomerulonephritis. An effective vaccine against Strep A would have great benefits worldwide. Here, we test two products, J8 and p*17-both peptide derivatives of a highly conserved region in the M protein, in combination with the protein subunit K4S2 of SpyCEP, an IL-8 protease associated with neutrophil chemoattraction. Each peptide is individually conjugated to cross reacting material (CRM 197 ), and the conjugated peptide vaccines are abbreviated as J8-K4S2 or p*17-K4S2., Methods: This single-site phase I, two-stage clinical trial in Edmonton, Alberta, Canada, aims to recruit a total of 30 healthy volunteers, aged 18-45 years, without any evidence of pre-existing valvular heart disease. The trial is divided into the initial unblinded safety test dose stage (stage 1) and the randomized, double-blinded, controlled trial stage (stage 2). Stage 1 will recruit 10 volunteers-5 each to receive either J8-K4S2 or p*17-K4S2 in an unblinded, staggered fashion, whereby volunteers are dosed with intentional spacing of at least 2 days in between doses to monitor for any immediate side effects before dosing the next. Once all 5 volunteers have received 3 doses of the first test vaccine, a similar process will follow for the second test vaccine. Once safety is established in stage 1, we will proceed to stage 2, which will recruit 20 volunteers to our 3-arm randomized controlled trial (RCT), receiving either of the trial vaccines, J8-K4S2 or p*17-K4S2, or comparator (rabies) vaccine. All product dosing will be at 0, 3, and 6 weeks. The primary outcome is vaccine safety; the secondary outcome is immunogenicity and comparative analyses of the different vaccine regimens., Discussion: This Strep A vaccine clinical trial aims to investigate safety and immunogenicity of two novel conjugated peptide-based vaccines, J8-KS42 and p*17-K4S2. If one or both vaccine products demonstrate favorable primary and secondary outcomes, the product(s) will move into phase II and III studies., Trial Registration: ClinicalTrials.gov Identifier: NCT04882514. Registered on 2021-05-12, https://clinicaltrials.gov/study/NCT04882514 ., Competing Interests: Declarations Ethics approval and consent to participate {24} The University of Alberta Human Research Ethics Board (HREB) has assessed and approved this protocol as well as the consent form and all trial related documents—REB Pro00089919, ver 05Oct2023. Written, informed consent to participate will be obtained from all participants. Consent for publication {32} Not applicable. No identifying images or other personal or clinical details of participants are presented here or will be presented in reports of the trial results. The participant information materials and informed consent form are available from the corresponding author upon request. Competing interests {28} MG and MP are co-inventors on the patents related to the vaccine candidates in trial.The remaining authors declare that they have no competing interests., (© 2024. The Author(s).)

Introduction: Streptococcus suis serotype ( cps ) 2 is an important bacterial pathogen in piglet nurseries and an emerging zoonotic agent without effective vaccines available. Immunoglobulin (Ig)M plays an essential role in host defense against S. suis . In mice, non-conventional B-1 cells are a major source of protective IgM against encapsulated bacterial pathogens, such as S. pneumoniae . Two IgM + CD21 - B-1-like cell subpopulations, distinguishable by CD11R1 expression, were described in pigs, but their properties and functions are poorly understood. This study aimed at a first characterization of the porcine early IgM B cell response against S. suis cps 2., Methods: We analyzed the same healthy pigs, naturally colonized by different S. suis serotypes, including cps 2, at four and eight weeks of age serologically and determined the frequency of different peripheral B cell subpopulations by flow cytometry. Furthermore, we isolated conventional IgM + CD21 + B-2 cells as well as non-conventional B-1-like cell subpopulations from peripheral blood of eight-weeks-old pigs to evaluate their potential of IgM secretion in response to innate and adaptive stimuli in vitro ., Results: Between the fourth and eighth week of life, a characteristic increase of S. suis cps 2-binding serum IgM antibodies, restricting bacterial growth, was observed. Moreover, we show for the first time that the significant increase of anti- S. suis serum IgM is associated with a relative increase of peripheral non-conventional IgM + CD21 - B-1-like cells in vivo , particularly of the IgM + CD21 - CD11R1 - subpopulation. Noteworthy, sorted IgM + CD21 - CD11R1 - B-1-like cells from eight-weeks-old pigs spontaneously secreted IgM in vitro . In addition, both non-conventional IgM + CD21 - B cell subpopulations, in contrast to conventional IgM + CD21 + B-2 cells, produced anti- S. suis IgM upon toll-like receptor (TLR) stimulation underlining their innate-like characteristics. We furthermore observed that both B-1-like subpopulations secrete S. suis cps 2-binding IgM upon stimulation with T cell-associated factors with highest amounts in IgM + CD21 - CD11R1 - B-1-like cells even exceeding anti- S. suis IgM levels produced by B-2 cells., Conclusion: Porcine non-conventional B-1-like cells are a potent source of S. suis -binding IgM indicating a role in immunity during a critical phase of piglet rearing., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Seidel, Kauffold, Protschka, Baums, Alber and Eschke.)

Antibiotic resistance in bacterial pathogen infections is a growing global issue that occurs due to their adaptation to changing environmental conditions. Therefore, producing an efficient vaccine as an alternative approach can improve the immune system, eradicate related pathogens, and overcome this growing problem. Streptococcus agalactiae belongs to group B Streptococcus (GBS). Colonization of GBS during pregnancy is a significant risk factor for infants and young children. S. agalactiae infected population exhibits resistance to beta-lactams, including penicillin and the second-line antibiotics erythromycin and clindamycin. On the other hand, there are currently no commercial vaccines against this pathogen. Vaccination of pregnant women is a highly effective method to protect newborns and infants from S. agalactiae infection, and it has been identified as an urgent demand by the World Health Organization. This study employed various immunoinformatic tools to develop an effective vaccine that could trigger both humoral and cell-mediated immunity and prevent disease. For this purpose, three conserved antigenic proteins of the main pathogenic strains of S. agalactiae were utilized to predict CTL, HTL, and B-cell epitopes for producing an mRNA vaccine against different strains of S. agalactiae. The selected epitopes were fused using proper linkers. The Resuscitation promoting factor E (RpfE) sequence was incorporated in the designed vaccine construct as an adjuvant to boost its immune response. Different physicochemical characteristics of the final designed vaccine, modeling of the three-dimensional structure, molecular docking, molecular dynamics simulation, and immunological response simulation were screened following vaccine administration in an in vivo model. Computational immune simulation data identified that IgG1, IgM, INF γ, IL-2, T helper, and B-cell populations increased significantly after vaccination. These findings suggested that the vaccine candidate may provide good protection against S. agalactiae infection. However, experimental and animal model studies are required for additional validation and implementation in human vaccination programs., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Despite growing recognition, neuropsychiatric diseases associated with infections are a major unsolved problem worldwide. Group A streptococcal (GAS) infections can cause autoimmune sequelae characterized by movement disorders, such as Sydenham chorea, and neuropsychiatric disorders. The molecular mechanisms underlying these diseases are not fully understood. Our previous work demonstrates that autoantibodies (AAbs) can target dopaminergic neurons and increase dopamine D2 receptor (D2R) signaling. However, AAb influence on dopamine D1 receptor (D1R) activity is underexplored. We found evidence that suggests GAS-induced cross-reactive AAbs promote autoimmune encephalitis of the basal ganglia, a region of high dopamine receptor density. Here, we report a mechanism whereby neuropsychiatric syndromes are distinguished from movement disorders by differences in D1R and D2R AAb titers, signaling, receiver operating characteristic curves, and immunoreactivity with D1R and D2R autoreactive epitopes. D1R AAb signaling was observed through patient serum AAbs and novel patient-derived monoclonal antibodies (mAbs), which induced both D1R G protein- and β-arrestin-transduced signals. Furthermore, patient AAbs and mAbs enhanced D1R signaling mechanisms mediated by the neurotransmitter dopamine. Our findings suggest that AAb-mediated D1R signaling may contribute to the pathogenesis of neuropsychiatric sequelae and inform new options for diagnosis and treatment of GAS sequelae and related disorders.

Bacterial extracellular vesicles (BEVs) are nanoscale membrane-bound structures involved in intercellular communication and transport of bioactive molecules. In this study, we described the proteomic insight and anti-inflammatory activity of Streptococcus parauberis BEVs (SpEVs). Proteomics analysis of SpEVs identified 6209 distinct peptides and 1039 proteins. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated enrichment in pathways related to the biosynthesis of aminoacyl tRNA, amino acids, and secondary metabolites. Based on the predicted protein-protein interactions, we discovered key immunological proteins such as IL12A, IL12B, IL8, CD28, and NF-κB between SpEVs and human proteins. Functionally, SpEVs exhibit strong anti-inflammatory activity in LPS-stimulated Raw 264.7 cells by reducing the production of key inflammatory mediators. These include nitric oxide (NO), reactive oxygen species (ROS), inflammatory cytokines such as TNFα and IL6, as well as inflammation-related proteins like inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). qRT-PCR and immunoblotting results clearly indicate that SpEVs modulate the NF-κB and MAPK pathways to induce anti-inflammatory activity. Furthermore, in vivo experiments with zebrafish larvae demonstrated that SpEVs treatment reduced the NO and ROS production with minimal cell mortality. Finally, we validated the anti-inflammatory activity of SpEVs in vivo by systematically assessing the inhibition of NO production, reduction in ROS generation, prevention of cell death, and modulation of NF-κB and MAPK signaling pathways. In conclusion, SpEVs contain rich in unique proteins that play crucial roles in mediating anti-inflammatory effects., Competing Interests: Declaration of competing interest The authors declared that there are no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Nile tilapia (Oreochromis niloticus) is one of the important economic fish species cultured worldwide. However, Streptococcus agalactiae has emerged as a significant bacterial threat, severely impacting the economy of tilapia industry. The immune response underlying the resistance of tilapia to S. agalactiae are not well understood, hindering the reasonable evaluation of breeding and the formulation of effective strategies. In this study, we investigated the differences in T-cell immunity between S. agalactiae-resistant and -susceptible tilapia. Compared with susceptible tilapia, resistant tilapia exhibited a higher percentage of T cells and BrdU + T cells during infection, indicating a superior proliferative capacity. Whether infected or not, T cells from resistant fish demonstrated a greater ability to resist apoptosis. Additionally, T cell effector genes, including interleukin (IL)-2, interferon (IFN)-γ, perforin A, and granzyme B were expressed at higher levels in resistant tilapia after infection. Along with these T-cell immune responses, resistant fish showed more effective clearance of infection. Our study elucidates the T-cell immune responses in resistant tilapia, which may contribute to the high resistance of tilapia to S. agalactiae, and provide valuable theoretical references for the selection and evaluation of disease-resistant fish strains in the future., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

IgY is an immunoglobulin primarily found in the serum and egg yolk of birds, amphibians, and reptiles. Recent years, IgY is considered to have a good application prospect in the immunodiagnostics and passive immunotherapy of aquatic diseases. In this study, we prepared a specific IgY against Streptococcus agalactiae in tilapia after immunizing the hens for 4 times. The result of ELISA detection showed that the IgY titers in water-soluble fraction (WSF) after 6 weeks of immunization reached 1:51200 and last for 4 weeks. Western blot (WB) analysis data showed that the specific IgY could recognize the target band, the specific IgY showed a concentration-dependent inhibitory effect on the growth of S. agalactiae, altered cell wall structure and aggluted of S. agalactiae. The quantitative reverse transcription PCR (qRT-PCR) analysis data suggested that the specific IgY downregulated the expression of pro-inflammatory factors (IL-8, TNF-α), upregulated the anti-inflammatory factors (IL-10, TGF-β). In addition, the histopathological results showed that the specific IgY significantly decreased the pathological manifestations, dramatically improved the survival rates of tilapia in injection, feeding, and immersion experiments. Collectively, our findings demonstrated that the broad potential of specific IgY for the prevention and treatment of S. agalactiae infection in tilapia., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Streptococcosis caused by Streptococcus agalactiae 1a in Nile tilapia (Oreochromis niloticus) is a severe disease challenge for the global supply of tilapia. Currently, the extensive use of antibiotics is the primary curative tool used to minimize the impact of the disease. Vaccination is a prophylactic measure that has been shown to reduce antibiotic use in the aquaculture sector substantially. However, no commercially licensed vaccine against Streptococcus agalactiae 1a is currently available. This study aimed to investigate, through molecular and immunological methods, if Streptococcus agalactiae 1a isolates collected from North America (NAM), Central America (CAM), and Southeast Asia (SEA) were similarly suitable for the development of a potentially effective vaccine to serve the global tilapia farming industry. Our comparative data showed that the Streptococcus agalactiae 1a isolates from NAM, CAM and SEA had similar biochemical profiles, and genetic multi-locus sequence typing (MLST) analysis showed that the NAM and CAM isolates belonged to sequence type 7 (ST-7) and clonal complex 1, while isolates from SEA grouped into three sequence types (ST-1650, ST-500, and ST-7) and two distinct clonal complexes (CC1 and CC12). Isolates from NAM, CAM, and SEA displayed similar antigenic profiles determined by western blotting with polyclonal rabbit antisera, which was supported by in vivo cross-protection studies, showing that fish immunized with vaccines based on SEA and CAM isolates with different genetic MLST profiles were highly protected against cross-challenge using the same bacterial strains for challenge. Overall, the data obtained from our investigations provide strong indications that Streptococcus agalactiae 1a distributed in NAM, CAM, and SEA are serologically uniform pathogens, and vaccines based on isolates of Streptococcus agalactiae 1a from these regions may be suited for vaccination of tilapia worldwide., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) is characterized by the abrupt onset of significant obsessive-compulsive symptoms (OCS) and/or severe food restriction, together with other neuropsychiatric manifestations. An autoimmune pathogenesis triggered by infection has been proposed for at least a subset of PANS. The older diagnosis of Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus (PANDAS) describes rapid onset of OCD and/or tics associated with infection with Group A Streptococcus. The pathophysiology of PANS and PANDAS remains incompletely understood. We recently found serum antibodies from children with rigorously defined PANDAS to selectively bind to cholinergic interneurons (CINs) in the striatum. Here we examine this binding in children with relapsing and remitting PANS, a more heterogeneous condition, collected in a distinct clinical context from those examined in our previous work, from children with a clinical history of Streptococcus infection. IgG from PANS cases showed elevated binding to striatal CINs in both mouse and human brain. Patient plasma collected during symptom flare decreased a molecular marker of CIN activity, phospho-riboprotein S6, in ex vivo brain slices; control plasma did not. Neither elevated antibody binding to CINs nor diminished CIN activity was seen with plasma collected from the same children during remission. These findings replicate what we have seen previously in PANDAS and support the hypothesis that at least a subset of PANS cases have a neuroimmune pathogenesis. Given the critical role of CINs in modulating basal ganglia function, these findings confirm striatal CINs as a locus of interest in the pathophysiology of both PANS and PANDAS., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dr. Pittenger has served as a consultant and received research funding in the past year for Biohaven Pharmaceuticals, Transcend Therapeutics, Ceruvia Lifesciecnes, Freedom Biosciences, and Nobilis Therapeutics, and royalties from Oxford University Press, all for work unrelated to the current results. He is an inventor on a patent applications related to the use of neurofeedback and of psychedelic drugs for the treatment of OCD, also unrelated to this work. Dr. Che has received research funding from Duraviva Pharma for work unrealted to the current results. All other authors report no competing interests. The authors have declared that no conflict of interest exists., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Although naturally Streptococcus suis serotype 2 (SS2) causes meningitis resulting in death or sequela of neurological symptoms in pigs and humans, severely threatening public health in the world, it has been difficult to build up and confirm experimental meningitis mouse models with obvious neurological syndrome for about two decades, which strongly hampers the in-depth study on the control measures and mechanisms of SS2-induced meningitis. In this study, a typical meningitis mouse model of SS2 was successfully established, as confirmed by the behavioral indicators of balance beam test, suspension test, and gait analysis. With bacteria gathering in the brain, distinguishable unique features including meningeal thickening, vacuolization of the Nissl body, brain barrier damage, glial cell activation, and more infiltration of T cells, macrophages, and DCs are observed in SS2 meningitis mice with typical neurological signs. Some meningitis mice were also accompanied by identical nephritis, ophthalmia, and cochlearitis. Investigation of the metabolic features demonstrated the downregulated cholic acid and upregulated 2-hydroxyvaleric acid, tetrahydrocortisone, nicotinic acid, and lauric acid in blood serum of mice and piglets with meningitis. And feeding trials show that lauric acid can promote meningitis by promoting the infiltration of immune cells into brain. These findings demonstrated that infection of ICR (improved castle road) mice with SS2 was able to induce typical meningitis accompanied by immune cell infiltration and lauric acid upregulation. These data provide a basis for the deep study of SS2 meningitis., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Four-finger threadfin, Eleutheronema tetradactylum farming in southern Taiwan has been facing disease problems caused by Streptococcus iniae since 2018. The development of a vaccine against infectious S. iniae in the cultured threadfin industry is necessary. Thus, this study aimed to examine the efficacy of threadfin immunized formalin-killed cells (FKC) from S. iniae GSI-111 for 42 days post-vaccination (dpv) using two doses of FKC alone (a booster at 14 dpv) as group A, and FKC mixed with ISA763A adjuvant using a single dose as group B or double doses as group C. Immunoglobulin (Ig)-M was purified from threadfin, and rabbit anti-threadfin IgM polyclonal antibodies were used to detect antibody level in immunized fish; the vaccinated group A displayed higher levels at 3 dpv and all vaccinated treatments demonstrated high antibody levels between 14 and 42 dpv. All vaccine groups showed significantly higher values of lysozyme activity at 42 dpv compared with the control group; the vaccinated A group peaked at 14 dpv. The expression profiles of pro-inflammatory and immune-related genes, TNF-α, IL-12A, and C2 were upregulated at 3 dpv, while CD8A and chemokine receptor CXCR4 were upregulated at 42 dpv. Finally, the threadfins were challenged with S. iniae at 42 dpv. The average relative percent survival was 96% for vaccination A and B treatments, and 100% for vaccination C treatment. In summary, this study demonstrated that FKC vaccines whether formulated with an adjuvant could stimulate immune response and effective protect threadfins against S. iniae infection., (© 2024 John Wiley & Sons Ltd.)

Globally, streptococcal disease caused by Streptococcus agalactiae is known for its high mortality rate, which severely limits the development of the tilapia breeding industry. As a third-generation vaccine, DNA vaccines have shown great application prospects in the prevention and control of aquatic diseases, but their low immunogenicity limits their development. The combination of DNA vaccines and molecular adjuvants proved to be an effective method for inducing protective immunity. This study constructed recombinant plasmids encoding tilapia HSP70 and IL-1β genes (pcHSP70 and pcIL-1β) to verify their effectiveness as molecular adjuvants for S. agalactiae DNA vaccine (pcSIP) in the immunized tilapia model. The results revealed that serum-specific IgM production, enzyme activities, and immune-related gene expression in tilapia immunized with pcSIP plus pcHSP70 or pcIL-1β were significantly higher than those in tilapia immunized with pcSIP alone. It is worth noting that combination with molecular adjuvants improved the immune protection of DNA vaccines, with a relative percentage survival (RPS) of 51.72% (pcSIP plus pcHSP70) and 44.83% (pcSIP plus pcIL-1β), respectively, compared with that of pcSIP alone (24.14%). Thus, our study indicated that HSP70 and IL-1β in tilapia are promising molecular adjuvants of the DNA vaccine in controlling S. agalactiae infection., (© 2024 John Wiley & Sons Ltd.)

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus, SEZ) is an essential zoonotic bacterial pathogen that can cause various inflammation, such as meningitis, endocarditis, and pneumonia. UDP-glucose dehydrogenase (hasB) is indispensable in synthesizing SEZ virulence factor hyaluronan capsules. Our study investigated the infection of hasB on mice response to SEZ by employing a constructed capsule-deficient mutant strain designated as the ΔhasB strain. This deficiency was associated with a reduced SEZ bacterial load in the mice's blood and peritoneal lavage fluid (PLF) post-infection. Besides, the ΔhasB SEZ strain exhibited a higher propensity for neutrophil infiltration and release of cell-free DNA (cfDNA) in vivo compared to the wild-type (WT) SEZ strain. In vitro experiments further revealed that ΔhasB SEZ more effectively induced the formation of neutrophil extracellular traps (NETs) containing histone 3 (H3), neutrophil elastase (NE), and DNA, than its WT counterpart. Moreover, the release of NETs was determined to be gasdermin D (GSDMD)-dependent during the infection process. Taken together, these findings underscore that the deficiency of the hasB gene in SEZ leads to enhanced GSDMD-dependent NET release from neutrophils, thereby reducing SEZ's capacity to resist NETs-mediated eradication during infection. Our finding paves the way for the development of innovative therapeutic strategies against SEZ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Feed-based bivalent vaccine (FBBV) containing killed whole organism (KWO) of Streptococcus agalactiae and Aeromonas hydrophila with 10% palm oil was previously proved to improve red hybrid tilapia's (Oreochromis sp.) immunity against streptococcosis and Aeromonas infections. This study characterized the FBBV's stability following the preparatory process and storage. The FBBV was prepared, and the KWO's stability was determined microscopically and molecularly. The efficacy of FBBV stored at room temperature (25 ± 2 °C) for 0, 30 and 60 days was investigated in red hybrid tilapia. The results indicated the addition of palm oil was not affecting the KWO's structure and helping in the FBBV's pelletization. In 1 g of FBBV contained 1.5 × 10 9 CFU/g of S. agalactiae and 4.9 × 10 9 CFU/g of A. hydrophila, respectively, even after 60 days of storage at room temperature. The KWO's structure in FBBV was not affected following in vitro acidic tolerance analysis, as noted from light and electron microscopies. The FBBV's carbohydrate, energy, moisture, total protein and total ash contents remained stable at 95% after 60 days of storage at room temperature, while the KWO's concentration was slightly reduced to 83.3% for S. agalactiae (1.25 × 10 9 CFU/g) and 80.6% for A. hydrophila (3.85 × 10 9 CFU/g), respectively. Fish vaccinated with FBBV that was stored for 0, 30 and 60 days did not show any significant differences (p ≥ 0.05) in the relative percent survival when challenged with pathogenic Streptococcus spp. and Aeromonas spp. These findings suggested that the FBBV is a stable vaccine, which underscores its potential application as aquatic vaccines in aquaculture., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Streptococcus uberis is a member of the pyogenic cluster of Streptococcus commonly associated with intramammary infection and mastitis in dairy cattle. It is a poorly controlled globally endemic pathogen responsible for a significant cause of the disease worldwide. The ruminant mammary gland provides an atypical body niche in which immune cell surveillance occurs on both sides of the epithelial tissue. S. uberis does not cause disease in non-ruminant species and is an asymptomatic commensal in other body niches. S. uberis exploits the unusual niche of the mammary gland to initiate an innate response from bovine mammary macrophage (BMMO) present in the secretion (milk) in which it can resist the host immune responses. As a result - and unexpectedly - the host inflammatory response is a key step in the pathogenesis of S.uberis , without which colonisation is impaired. In contrast to other bacteria pathogenic to the bovine mammary gland, S. uberis does not elicit innate responses from epithelial tissues; initial recognition of infection is via macrophages within milk., Methods: We dissected the role of the bacterial protein SUB1154 in the inflammasome pathway using ex vivo bovine mammary macrophages isolated from milk, recombinant protein expression, and a panel of inhibitors, agonists, and antagonists. We combine this with reverse-transcription quantitative real-time PCR to investigate the mechanisms underlying SUB1154-mediated priming of the immune response., Results: Here, we show that SUB1154 is responsible for priming the NLRP3 inflammasome in macrophages found in the mammary gland. Without SUB1154, IL-1β is not produced, and we were able to restore IL-1β responses to a sub1154 deletion S. uberis mutant using recombinant SUB1154. Surprisingly, only by blocking internalisation, or the cytoplasmic TIR domain of TLR2 were we able to block SUB1154-mediated priming., Discussion: Together, our data unifies several contrasting past studies and provides new mechanistic understanding of potential early interactions between pyogenic streptococci and the host., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Hinds, Ward, Archer and Leigh.)

In Streptococcus pyogenes, the type II fatty acid (FA) synthesis pathway FASII is feedback-controlled by the FabT repressor bound to an acyl-Acyl carrier protein. Although FabT defects confer reduced virulence in animal models, spontaneous fabT mutants arise in vivo. We resolved this paradox by characterizing the conditions and mechanisms requiring FabT activity, and those promoting fabT mutant emergence. The fabT defect leads to energy dissipation, limiting mutant growth on human tissue products, which explains the FabT requirement during infection. Conversely, emerging fabT mutants show superior growth in biotopes rich in saturated FAs, where continued FASII activity limits their incorporation. We propose that membrane alterations and continued FASII synthesis are the primary causes for increased fabT mutant mortality in nutrient-limited biotopes, by failing to stop metabolic consumption. Our findings elucidate the rationale for emerging fabT mutants that improve bacterial survival in lipid-rich biotopes, but lead to a genetic impasse for infection., (© 2024. The Author(s).)

The Asian seabass (Lates calcarifer) faces significant disease threats, which are exacerbated by intensive farming practices and environmental changes. Therefore, understanding its immune system is crucial. The current study presents a comprehensive analysis of immune-related genes in Asian seabass peripheral blood leukocytes (PBLs) using Iso-seq technology, identifying 16 key pathways associated with 7857 immune-related genes, comprising 634 unique immune-related genes. The research marks the first comprehensive report on the entire immunoglobulin repertoire in Asian seabass, revealing specific characteristics of immunoglobulin heavy chain constant region transcripts, including IgM (Cμ, ighm), IgT (Cτ, ight), and IgD (Cδ, ighd). The study confirms the presence of membrane-bound form, ighm mb , ight mb , ighd mb of IgM, IgT and IgD and secreted form, ighm sc and ight sc of IgM and IgT, respectively, with similar structural patterns and conserved features in amino acids across immunoglobulin molecules, including cysteine residues crucial for structural integrity observed in other teleost species. In response to bacterial infections by Flavobacterium covae (formerly F. columnare genomovar II) and Streptococcus iniae, both secreted and membrane-bound forms of IgM (ighm mb and ighm sc ) and IgT (ight mb and ight sc ) show significant expression, indicating their roles in systemic and mucosal immunity. The expression of membrane-bound form IgD gene, ighd mb , predominantly exhibits targeted upregulation in PBLs, suggesting a regulatory role in B cell-mediated immunity. The findings underscore the dynamic and tissue-specific expression of immunoglobulin repertoires, ighm mb , ighm sc , ight mb , ight sc and ighd mb in Asian seabass, indicating a sophisticated immune response to bacterial pathogens. These findings have practical implications for fish aquaculture, and disease control strategies, serving as a valuable resource for advancing research in Asian seabass immunology., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

High mobility group protein B2 (HMGB2) is an abundant chromatin-associated protein with pivotal roles in transcription, cell proliferation, differentiation, inflammation, and tumorigenesis. However, its immune function in Nile tilapia (Oreochromis niloticus) remains unclear. In this study, we identified a homologue of HMGB2 from Nile tilapia (On-HMGB2) and investigated its functions in the immune response against streptococcus infection. The open reading frame (ORF) of On-HMGB2 spans 642 bp, encoding 213 amino acids, and contains two conserved HMG domains. On-HMGB2 shares over 80 % homology with other fish species and 74%-76 % homology with mammals. On-HMGB2 was widely distributed in various tissues, with its highest transcript levels in the liver and the lowest in the intestine. Knockdown of On-HMGB2 promoted the inflammatory response in Nile tilapia, increased the bacterial load in the tissues, and led to elevated mortality in Nile tilapia following Streptococcus agalactiae infection. Taken together, On-HMGB2 significantly influences the immune system of Nile tilapia in response to streptococcus infection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The complement system is the first defense line of the immune system. However, pathogens have evolved numerous strategies to evade complement attacks. Streptococcus suis is an important zoonotic bacterium, harmful to both the pig industry and human health. ApuA has been reported as a bifunctional amylopullulanase and also contributed to virulence of S. suis. Herein, we found that ApuA could activate both classical and alternative pathways of the complement system. Furthermore, by using bacterial two-hybrid, far-western blot and ELISA assays, it was confirmed that ApuA could interact with complement C3b. The interaction domain of ApuA with C3b was found to be its α-Amylase domain (ApuA&#95;N). After construction of an apuA mutant (ΔapuA) and its complementary strain, it was found that compared to the wild-type strain (WT), ΔapuA had significantly increased C3b deposition and membrane attack complex formation. Additionally, ΔapuA showed significantly lower survival rates in human serum and blood and was more susceptible to engulfment by neutrophils and macrophages. Mice infected with ΔapuA had significantly higher survival rates and lower bacterial loads in their blood, lung and brains, compared to those infected with WT. In summary, this study identified ApuA as a novel factor involved in the complement evasion of S. suis and suggested its multifunctional role in the pathogenesis of S. suis., Competing Interests: Declaration of Competing Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Group B Streptococcus (GBS) is a major cause of pneumonia, sepsis, and meningitis in infants younger than 3 months of age. Furthermore, GBS infection in pregnant women is associated with stillbirths and pre-term delivery. It also causes disease in immunocompromised adults and the elderly, but the highest incidence of the disease occurs in neonates and young infants. At this time, there are no licensed vaccines against GBS. Complete GBS genome sequencing has helped identify genetically conserved and immunogenic proteins, which could serve as vaccine immunogens. In this study, in silico reverse vaccinology method were used to evaluate the prevalence and conservation of GBS proteins in invasive and colonizing isolates from South African infants and women, respectively. Furthermore, this study aimed to predict potential GBS vaccine targets by evaluating metrics such as antigenicity, physico-chemical properties, subcellular localization, secondary and tertiary structures, and epitope prediction and conservation. A total of 648 invasive and 603 colonizing GBS isolate sequences were screened against a panel of 89 candidate GBS proteins. Ten of the 89 proteins were highly genetically conserved in invasive and colonizing GBS isolates, nine of which were computationally inferred proteins (gbs2106, SAN&#95;1577, SAN&#95;0356, SAN&#95;1808, SAN&#95;1685, SAN&#95;0413, SAN&#95;0990, SAN&#95;1040, SAN&#95;0226) and one was the surface Immunogenic Protein (SIP). Additionally, the nine proteins were predicted to be more antigenic than the SIP protein (antigenicity score of > 0.6498), highlighting their potential as GBS vaccine antigen targets., (© 2024. The Author(s).)

A global increase in the incidence of various infectious diseases has been observed since the end of the COVID‑19 pandemic. This may be due to 2 independent phenomena. One of them is impaired immunity of long‑COVID patients. The second (major) one is associated with long‑term isolation of many people during the global pandemic‑related lockdown, resulting in an extreme reduction of exposure to natural environmental human microbiota. This, in turn, led to a silencing state of the body's defense systems, including a decline of the prepandemic trained immunity (innate memory), which only persists for weeks to months after exposure to a pathogen. This decrease in the performance of trained immunity may be especially important for morbidity of infectious diseases without currently available vaccines, such as invasive group A Streptococcus pyogenes (GAS) infections, primarily streptococcal toxic shock syndrome. This review discusses data that support an important role of trained macrophages in host defense, and demonstrates the potential clinical implications of β‑glucan, the major inducer of trained macrophages, for prophylactic and therapeutic use in individuals with impaired personal innate immunity. Altogether, it might be speculated that trained innate immunity within an entire population can lead to the development of herd trained immunity (HTI), a newly‑coined medical term. HTI can supplement classic, antigen‑specific herd immunity (memory B and T cells), and it plays a key role in preventing the spread of various infectious diseases, including invasive GAS infections. Unfortunately, the global HTI has been overthrown during the COVID‑19 pandemic; however, it should be restored shortly.

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that induces an NLRP3-dependent cytokine storm. NLRP3 inflammasome activation triggers not only an inflammatory response but also pyroptosis. However, the exact mechanism underlying S. suis-induced macrophage pyroptosis is not clear. Our results showed that SS2 induced the expression of pyroptosis-associated factors, including lactate dehydrogenase (LDH) release, propidium iodide (PI) uptake and GSDMD-N expression, as well as NLRP3 inflammasome activation and IL-1β secretion. However, GSDMD deficiency and NLRP3 inhibition using MCC950 attenuated the SS2-induced expression of pyroptosis-associated factors, suggesting that SS2 induces NLRP3-GSDMD-dependent pyroptosis. Furthermore, RACK1 knockdown also reduced the expression of pyroptosis-associated factors. In addition, RACK1 knockdown downregulated the expression of NLRP3 and Pro-IL-1β as well as the phosphorylation of P65. Surprisingly, the interaction between RACK1 and P65 was detected by co-immunoprecipitation, indicating that RACK1 induces macrophage pyroptosis by mediating the phosphorylation of P65 to promote the transcription of NLRP3 and pro-IL-1β. Similarly, NEK7 knockdown decreased the expression of pyroptosis-associated factors and ASC oligomerization. Moreover, the results of co-immunoprecipitation revealed the interaction of NEK7-RACK1-NLRP3 during SS2 infection, demonstrating that NEK7 mediates SS2-induced pyroptosis via the regulation of NLRP3 inflammasome assembly and activation. These results demonstrate the important role of RACK1 and NEK7 in SS2-induced pyroptosis. Our study provides new insight into SS2-induced cell death., (© 2024. The Author(s).)

Streptococcus suis (S. suis) is one of the most important porcine pathogens, causing severe pathologies such as meningitis or polyarthritis. It is also a very successful colonizer of mucosal surfaces. The IgM-degrading enzyme of S. suis (Ide Ssuis ) specifically cleaves porcine IgM, which results in complement evasion. On the basis of our previous finding that Ide Ssuis also cleaves the IgM B cell receptor in vitro, we verified IgM B cell receptor cleavage ex vivo in whole regional lymph nodes and investigated the working hypothesis that this IgM B cell receptor cleavage results in a long-lasting impaired B cell function. The number of IgM-secreting cells was determined via ELISpot analysis after porcine peripheral blood mononuclear cells had initially been treated with different recombinant S. suis proteins and subsequently stimulated with interleukin-2 and the toll-like receptor 7/8 ligand R848. Compared with treatment with medium or recombinant muramidase-released protein, treatment with rIde Ssuis but also with a cleavage-deficient variant led to a reduction in the number of IgM-secreting cells as well as the level of secreted IgM. Flow cytometry analysis confirmed that the IgM B cell receptor was cleaved only by rIde Ssuis, and the receptor recovered to pretreatment levels on day 2 after treatment. Flow cytometry analysis of B and T cells incubated with fluorescein-labelled recombinant proteins revealed that different rIde Ssuis variants bind specifically to B cells, most prominently the cleavage-deficient variant. Our results indicate that in vitro interference of rIde Ssuis with the IgM B cell receptor results in long-lasting impaired IgM secretion by B cells after toll-like receptor activation. Further studies are warranted to prove that the modulation of B cell function by Ide Ssuis could play a role in vivo., (© 2024. The Author(s).)

Background: Group A Streptococcus (Strep A) causes both uncomplicated and severe invasive infections, as well as the post-infection complications acute rheumatic fever and rheumatic heart disease. Despite the high global burden of disease resulting from Strep A infections, there is not a licensed vaccine. A 30-valent M protein-based vaccine has previously been shown to be immunogenic in animal models and in a Phase I clinical trial (NCT02564237). Here, we assessed the immunogenicity of a 30-valent messenger (m)RNA vaccine designed to express the same M peptide targets as the 30-valent protein vaccine and compared it with the protein vaccine., Methods: Female New Zealand white rabbits were immunized with one of four vaccine formulations (3 doses of each formulation at days 1, 28, and 56): soluble mRNA (100 μg/animal), C-terminal transmembrane mRNA (100 μg/animal), protein vaccine (400 μg/animal), or a non-translatable RNA control (100 μg/animal). Serum was collected one day prior to the first dose and on days 42 and 70. Rabbit serum samples were assayed for antibody levels against synthetic M peptides by ELISA. HL-60 opsonophagocytic killing (OPK) assays were performed to assess functional antibody levels., Results: Serum IgG levels were similar for the mRNA and protein vaccines. The CtTM version of the mRNA vaccine elicited slightly higher antibody levels than the mRNA designed to express soluble proteins. OPK activity was similar for the mRNA and protein vaccines, regardless of M type., Conclusions: The total antibody responses and functional antibody levels elicited by the 30-valent mRNA Strep A vaccines were similar to those observed following immunization with the analogous protein vaccine. The mRNA vaccine platform provides potential advantages to protein-based vaccines including inherent adjuvant activity, increased production efficiency, lower cost, and the potential to rapidly change epitopes/peptides, all of which are important considerations related to multivalent Strep A vaccine development., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: MBF, COO, CD, and OP are employees of Moderna, Inc. and may hold stock or stock options. JBD is the inventor of certain technologies related to the development of group A streptococcal vaccines. The technology is owned by the University of Tennessee Research Foundation., (Copyright © 2024. Published by Elsevier Ltd.)

A wealth of research indicates that superficial gastritis (SG) and atrophic gastritis (AG) are precursors to gastric cancer (GC). While Helicobacter pylori (H. pylori) has long been recognized as a key player in GC development, recent findings by Fu et al. have identified Streptococcus anginosus (S. anginosus) as an emerging pathogen that can trigger SG, AG and GC. S. anginosus, a gram-positive coccus, leverages its surface protein T. pallidum membrane protein C (TMPC) to engage with the annexin A2 (ANXA2) receptor of gastric epithelial cells, facilitating its colonization and invasion in the gastric mucosa. This leads to an upregulation of proinflammatory chemokines Ccl20 and Ccl8, causing prolonged effects on gastric barrier function and microbiota homeostasis, leading to SG. Moreover, these bacteria activate the mitogen-activated protein kinase (MAPK) signaling pathway, which is associated with the development of AG and GC. Importantly, inhibiting TMPC or knocking down ANXA2 can reduce S. anginosus colonization and invasion, lowering the chances of SG, AG, and GC. This paper highlights the molecular mechanisms of S. anginosus in SG, AG and GC, emphasizing the importance of a multi-pathogen strategy in gastric disease management and the need for further investigation into the role of S. anginosus in GC progression.

Streptococcus pyogenes is a human pathogenic, gram positive bacterium that primarily leads to pharyngitis or soft tissue infections. Primary peritonitis caused by S. pyogenes infection is rare and there are only a few published cases worldwide. Primary peritonitis due to other pathogens occurs in immunosuppressed conditions such as HIV or other chronic diseases. However, younger, healthy women are more likely to be affected by S. pyogenes peritonitis. At present, the underlying molecular mechanisms can only be speculated on. One possibility is that, similar to the clinical picture of streptococcal toxic shock syndrome (STSS), a specific serotype of the M protein in combination with inhibition of the cell response of neutrophil granulocytes could play a role. In addition to peritonitis, the clinical picture may include other organ manifestations such as acute kidney damage or circulatory dysregulation. In terms of treatment, rapid pathogen-directed empirical antibiotic therapy is the treatment of choice. If there is no indication of secondary peritonitis, diagnostic laparoscopy can be dispensed with in the further diagnostic work-up., (© 2024. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)