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Background: To evaluate the influence of previous physical activity (PA) during childhood, adolescence, and current PA practice on the production of antibodies and inflammatory response between the first and second doses of the COVID-19 vaccine. Methods: Fifty-nine men and 56 women were evaluated before the first vaccine, and 12 weeks later, blood samples were taken to quantify production of anti-severe acute respiratory syndrome coronavirus-2 immunoglobulin G antibodies and cytokines. Previous PA during childhood and adolescence was self-referred, and current PA was assessed using the International Physical Activity Questionnaire. Results: A positive and significant association was observed only between PA practice during adolescence and an increase in antibody production in adulthood (β = 2012.077, 95% confidence interval, 257.7953–3766.358, P =.025). Individuals who practiced PA during adolescence showed higher production of antibodies between the first and second vaccine dose compared to nonpractitioners (P =.025) and those that accumulated ≥150 minutes per week of current moderate–vigorous PA (MVPA), and presented higher antibody production in relation to who did <150 minutes per week of MVPA (P =.046). Individuals that were practitioners during childhood produced higher G-CSF (P =.047), and those that accumulated ≥150 minutes per week of current MVPA demonstrated lower IP-10 levels (P =.033). However, PA practitioners during adolescence presented higher G-CSF (P =.025), IL-17 (P =.038), IL-1RA (P =.005), IL-1β (P =.020), and IL-2 (P =.026) levels. Conclusion: Our results suggest that adults that accumulated at least 150 minutes of MVPA per week or practiced PA during adolescence developed an improved immune and inflammatory response against COVID-19 vaccination. [ABSTRACT FROM AUTHOR]

Chinese hamster ovary (CHO) cells represent the most preferential host cell system for therapeutic monoclonal antibody (mAb) production. Enhancing mAb production in CHO cells can be achieved by adding chemical compounds that regulate the cell cycle and cell survival pathways. This study investigated the impact of ectoine supplementation on mAb production in CHO cells. The results showed that adding ectoine at a concentration of 100 mM on the 3rd day of cultivation improved mAb production by improving cell viability and extending the culture duration. RNA sequencing analysis revealed differentially expressed genes associated with cell cycle regulation, cell proliferation, and cellular homeostasis, in particular promotion of cell cycle arrest, which was then confirmed by flow cytometry analysis. Ectoine-treated CHO cells exhibited an increase in the number of cells in the G0/G1 phase. In addition, the cell diameter was also increased. These findings support the hypothesis that ectoine enhances mAb production in CHO cells through mechanisms involving cell cycle arrest and cellular homeostasis. Overall, this study highlights the potential of ectoine as a promising supplementation strategy to enhance mAb production not only in CHO cells but also in other cell lines. [Display omitted] • Ectoine improved mAb production in CHO cells. • Ectoine improved cell viability and extended the culture duration of CHO cells. • Ectoine increased the number of CHO cells in the G0/G1 phase. • Enhanced mAb production involved cell cycle arrest and cellular homeostasis. • Ectoine is a promising supplement to enhance mAb production in cell lines. [ABSTRACT FROM AUTHOR]

Cultivations of Chinese Hamster Ovary (CHO) cells in a perfusion setup were conducted in the presence of super physiological concentrations of L-Arginine to investigate the impact on transmission through the perfusion filter for production of a recombinant domain antibody. Our study revealed that the presence of L-Arginine within the range of 30–50 mM had a positive impact on transmission. However, the higher concentrations were found to have a negative correlation with cell viability, and an optimal concentration of approximately 40 mM was identified. The supplementation of L-Arginine improved overall cultivation performance and enhanced product quality attributes. As a result, our findings demonstrate that the supplementation of L-Arginine to mammalian perfusion cultivations stands as an effective method to address transmission issues, exerting a broad impact on process and production of recombinant proteins. • Mammalian cell cultivations with high L-Arginine assessed impact on transmission for domain antibody production. • 30–50 mM L-Arginine positively affected transmission, while excessive concentrations impacted viability. • Optimal 40 mM improved transmission, positively influencing performance and product quality. • L-Arginine in perfusion cultivations offers a method for resolving transmission issues. • Findings suggest general applicability of L-Arginine in improving recombinant protein production. [ABSTRACT FROM AUTHOR]

In this article, a cytokine-enhanced viral infection model with cytotoxic T lymphocytes (CTLs) immune response and antibody immune response is proposed and analyzed. The model contains six compartments: uninfected CD4+T cells, infected CD4+T cells, inflammatory cytokines, viruses, CTLs and antibodies. Different from the previous works, this model not only considers virus-to-cell transmission and cell-to-cell transmission, but also includes a new infection mode, namely cytokine-enhanced viral infection. The incidence rates of the healthy CD4+T cells with viruses, infected cells and inflammatory cytokines are given by general functions. Moreover, the production/proliferation and removal/death rates of all compartments are represented by general functions. Firstly, we prove that all the solutions of the model are nonnegative and uniformly bounded. Then, five key parameters with strong biological significance, namely the virus basic reproduction number R0, CTLs immune response reproduction number R1, antibody immune response reproductive number R2, CTLs immune competitive reproductive number R3 and antibody immune competitive reproductive number R4 are derived. Then, by using Lyapunov's method and LaSalle's invariance principle, we have shown the global stability of each equilibrium. In addition, the numerical simulation results also show that the theoretical results are correct. Finally, we formulate an optimal control problem and solve it using Pontryagins Maximum Principle and an efficient iterative numerical methods. The results of our numerical simulation show that it is very important to control the infection between viruses and cells and between cells and inflammatory cytokines for controlling HIV. [ABSTRACT FROM AUTHOR]

Antigen-specific antibodies are generated by antibody-secreting cells (ASCs). How RNA post-transcriptional modification affects antibody homeostasis remains unclear. Here, we found that mRNA polyadenylations and N6-methyladenosine (m6A) modifications maintain IgG1 antibody production in ASCs. IgG heavy-chain transcripts (Ighg) possessed a long 3′ UTR with m6A sites, targeted by the m6A reader YTHDF1. B cell-specific deficiency of YTHDF1 impaired IgG production upon antigen immunization through reducing Ighg1 mRNA abundance in IgG1+ ASCs. Disrupting either the m6A modification of a nuclear-localized splicing intermediate Ighg1 or the nuclear localization of YTHDF1 reduced Ighg1 transcript stability. Single-cell RNA sequencing identified an ASC subset with excessive YTHDF1 expression in systemic lupus erythematosus patients, which was decreased upon therapy with immunosuppressive drugs. In a lupus mouse model, inhibiting YTHDF1-m6A interactions alleviated symptoms. Thus, we highlight a mechanism in ASCs to sustain the homeostasis of IgG antibody transcripts by integrating Ighg1 mRNA polyadenylation and m6A modification. [Display omitted] • m6A-modified Ighg1 RNA acts as a precursor for secretory Ighg1 • Loss of YTHDF1 in B cells decreases IgG response by reducing IgG transcript life in ASCs • YTHDF1 and Ighg1 mRNA form nuclear granules for Ighg1 stability in ASCs • YTHDF1 accumulation in ASCs promotes the pathogenesis of SLE IgG antibody production must be tightly maintained for appropriate antibody immunity. Wang et al. reveal a mechanism to sustain the homeostasis of IgG antibody transcripts by integrating Ighg1 mRNA polyadenylation and m6A modification in antibody-secreting cells (ASCs). Data from individuals with SLE and from a lupus mouse model highlight the clinical relevance of the mechanism. [ABSTRACT FROM AUTHOR]

Swine acute diarrhoea syndrome coronavirus (SADS-CoV) causes vomiting, severe diarrhoea and death in newborn piglets. The spike (S) protein plays a crucial role in promoting virus invasion and inducing neutralizing antibody production. In this study, the extracellular region of the S protein was used as an immunogen to immunize BALB/c mice. After immunization, B cells were collected, fused with SP2/0 myeloma cells, cultured and subcloned, and a cell line capable of secreting neutralizing antibodies was obtained and named as 5D6. Additionally, it was determined that the 5D6 mAb could be used as the primary antibody for western blotting and indirect immunofluorescence assay (IFA) to detect SADS-CoV. Further studies indicated that the 5D6 mAb binds to the 136STSHAAD142 motif, which located in the N-terminal domain (NTD) of the spike protein. This result suggested that the NTD of the S protein can induce the production of neutralizing antibodies. Amino acid sequence alignment revealed that the epitope of the 5D6 mAb was conserved among SADS-CoV strains. This study helps elucidate the S protein function of SADS-CoV, and the 5D6 mAb may be used to develop diagnostic and treatment tools for detecting SADS-CoV infection. [ABSTRACT FROM AUTHOR]

Avian influenza viruses (AIVs) are a major economic burden to the poultry industry and pose serious zoonotic risks, with human infections being reported every year. To date, the vaccination of birds remains the most important method for the prevention and control of AIV outbreaks. Most national vaccination strategies against AIV infection use whole virus-inactivated vaccines, which predominantly trigger a systemic antibody-mediated immune response. There are currently no studies that have examined the antibody repertoire of birds that were infected with and/or vaccinated against AIV. To this end, we evaluate the changes in the H9N2-specific IgM and IgY repertoires in chickens subjected to vaccination(s) and/or infectious challenge. We show that a large proportion of the IgM and IgY clones were shared across multiple individuals, and these public clonal responses are dependent on both the immunisation status of the birds and the specific tissue that was examined. Furthermore, the analysis revealed specific clonal expansions that are restricted to particular H9N2 immunisation regimes. These results indicate that both the nature and number of immunisations are important drivers of the antibody responses and repertoire profiles in chickens following H9N2 antigenic stimulation. We discuss how the repertoire biology of avian B-cell responses may affect the success of AIV vaccination in chickens, in particular the implications of public versus private clonal selection. [ABSTRACT FROM AUTHOR]

The present study aimed to determine the dynamics of influenza A virus (IAV) infection in two endemically infected farms (F1 and F2), where a longitudinal follow-up of piglets was performed from birth to 8–12 weeks of age. During the study, a highly virulent isolate of porcine reproductive and respiratory syndrome virus (PRRSV) was introduced on both farms. This allowed us to examine the impact of such introduction on the patterns of infection, disease, and the antibody response of pigs to IAV infection. The introduction of the new PRRSV strain coincided with a change in the dynamics of IAV infection on both farms. In F1, the cumulative incidence of IAV increased from 20% before the outbreak to 67.5%, together with the existence of animals that tested positive for IAV (RT‒qPCR) in nasal swabs for two or more consecutive samples. In F2, the cumulative incidence of IAV increased from 50% before the PRRSV outbreak to 70%, and the proportion of prolonged IAV shedders increased sharply. Additionally, some animals were infected with the same IAV twice during the observation period. In contrast to previous reports, our study revealed that prolonged shedding was not related to the titres of maternally derived antibodies at the time of infection but was significantly (p < 0.05) related to PRRSV infection status. Notably, both before and after the PRRSV outbreak, a high proportion of IAV-infected piglets did not seroconvert, which was significantly (p < 0.05) related to the hemagglutination inhibition titres against IAV when infected. [ABSTRACT FROM AUTHOR]

Endophilin A2, the sole endophilin A family member expressed in hematopoietic cells, regulates various aspects of membrane dynamics, including autophagy and endocytosis. Recent studies in rodents highlight the essential role of endophilin A2 in modulating immune responses. Here we report a homozygous frameshift variant in the SH3GL1 gene (NM_003025.3:c.427delC; p.Leu143Serfs*9), detected by whole exome sequencing in a 14-year-old boy with predominantly antibody deficiency. The patient who is issued from a consanguineous Lebanese family, presents since the age of 18 months with recurrent respiratory tract infections, low peripheral B cell counts and pan-hypogammaglobulinemia, with no history of opportunistic infections. This defect is associated with decrease in switched memory B cells development, impaired in-vitro B cell proliferation and diminished in-vitro IgG production. The detected variant in SH3GL1 segregates with the disease in the family. It significantly decreases the expression of the protein in the patient's peripheral blood compared to healthy controls, thus confirming its pathogenicity. Interestingly, endophilin A2-deficient Sh3gl1−/− mice have been reported to present defects in germinal center B cell responses and in the production of high-affinity IgG. Our data suggests that endophilin A2 deficiency impairs antibody production in humans. Reporting further cases with mutations in SH3GL1 is needed to better characterize the inborn error of immunity linked to this gene. [ABSTRACT FROM AUTHOR]

An effective vaccine against hepatitis C virus (HCV) should elicit both humoral and cellular immune responses. Previously, we characterized a bivalent vaccine candidate against hepatitis B (HBV) and HCV using chimeric HBV-HCV virus-like particles (VLP), in which the highly conserved epitope of HCV E2 glycoprotein (residues 412–425) was inserted into the hydrophilic loop of HBV small surface antigen (sHBsAg). While sHBsAg_412–425 elicited cross-neutralizing antibodies, it did not trigger a T-cell response against HCV. Thus, this study aimed to develop a vaccine candidate engaging both arms of adaptive immune response, potentially offering stronger protection against HCV. We evaluated the immunogenicity of minicircle (MC) DNA vaccines encoding sHBsAg_412–425 and HCV nonstructural (NS) proteins in BALB/c mice. Co-administration of sHBsAg_412–425 and NS induced a potent T-cell response, especially against NS3 and high titers of antibodies specific to HCV E2. Additionally, these antibodies recognized native HCV envelope glycoprotein heterodimers (E1E2) across multiple HCV genotypes and showed binding profiles to E1E2 alanine mutants comparable to the broadly neutralizing AP33 antibody. Overall, the findings demonstrate that MC DNA vaccine incorporating both sHBsAg_412–425 and HCV NS protein sequences induces robust, T-cell and AP33-like antibody responses, highlighting its potential as pan-genotypic prophylactic vaccine against HCV. [ABSTRACT FROM AUTHOR]

Background Aim Methods Results Conclusion The role of autoimmune IgE responses in atopic dermatitis (AD) is highly debated. While IgE targeting self‐proteins has been extensively studied, IgE responses induced by human‐homologous exogenous molecular allergens (HEMAs) remains less understood.To investigate whether IgE antibody responses to HEMAs are associated with AD, its severity, and response to dupilumab.We enrolled 3325 participants with a history of allergic diseases, including 577 (17.3%) diagnosed with AD. Serum IgE antibodies against 183 exogenous allergenic molecules were measured using the IgE microarray (Allergy Explorer‐ALEX‐2®, MADX, Vienna). Based on international classification criteria, participants were stratified by AD severity and clinical phenotypes. For each patient, we developed an ‘IgE molecular‐mimicry index’ (IgE‐MMI), calculated from IgE reactivity to a panel of five HEMA protein families: arginine kinase, enolase (ENO), cyclophilin (CYP), lipocalin, and MnSOD. Logistic regression was employed to assess the association between IgE to HEMAs or IgE‐MMI and AD, its severity, and response to dupilumab.IgE sensitization to most HEMAs (32/48, 67%), but only to a small fraction of non‐HEMAs (3/135, 2.2%), was significantly more common in patients with severe AD compared to other patient groups. The IgE‐MMI was positive in 295/2748 (10.7%) of allergic patients without AD, and in 58/283 (20%), 52/134 (39%), and 86/160 (54%) of patients with remitting, moderate, or severe AD, respectively. It was strongly associated with specific phenotypes, such as flexural dermatitis (OR 8.4, 95% CI: 6.3–11.2), head and neck dermatitis (OR: 16.5, 95% CI: 7.4–37.2), and generalized eczema (OR: 8.6, 95% CI: 4.9–15.6). Poor response to dupilumab was associated with IgE antibodies to ENO (OR: 22.7, 95% CI: 1.7–302.9), but inversely associated with IgE antibodies to MnSOD (OR: 0.1, 95% CI: 0.02–0.8) and NPC‐2 from dust mites (OR: 0.1, 95% CI: 0.01–0.9).IgE microarrays are useful for broadly assessing IgE to HEMAs in allergic patients. IgE reactivity to HEMAs and a positive IgE‐MMI may serve as valuable biomarkers for severe AD, its clinical phenotypes, and the response to dupilumab. [ABSTRACT FROM AUTHOR]

Vaccine development targeting rapidly evolving pathogens such as HIV-1 requires induction of broadly neutralizing antibodies (bnAbs) with conserved paratopes and mutations, and in some cases, the same Ig-heavy chains. The current trial-and-error search for immunogen modifications that improve selection for specific bnAb mutations is imprecise. Here, to precisely engineer bnAb boosting immunogens, we use molecular dynamics simulations to examine encounter states that form when antibodies collide with the HIV-1 Envelope (Env). By mapping how bnAbs use encounter states to find their bound states, we identify Env mutations predicted to select for specific antibody mutations in two HIV-1 bnAb B cell lineages. The Env mutations encode antibody affinity gains and select for desired antibody mutations in vivo. These results demonstrate proof-of-concept that Env immunogens can be designed to directly select for specific antibody mutations at residue-level precision by vaccination, thus demonstrating the feasibility of sequential bnAb-inducing HIV-1 vaccine design. In this work, researchers engineer HIV-1 immunogens using molecular dynamics simulations to enhance vaccine designs that select for specific antibody mutations. Their approach improved the selection of mutations crucial for broadly neutralizing antibody responses, offering a promising strategy for HIV vaccine development. [ABSTRACT FROM AUTHOR]

Ehrlichia canis is the primary etiologic agent of canine monocytic ehrlichiosis, a serious and sometimes fatal hemorrhagic disease of dogs. Diagnosis of E. canis infection is often retrospectively confirmed by serologic detection of antibodies by immunofluorescent microscopy. Our laboratory previously identified numerous major immunoreactive proteins with species-specific linear antibody epitopes that are useful for immunodiagnosis of CME. More recently, we have defined the entire antibody-reactive immunome of E. canis , substantially increasing the number of major immunoreactive proteins known to exist. In this study, we analyzed and compared seven recently identified antibody reactive E. canis proteins with established diagnostic antigens including tandem repeat proteins TRP19, TRP36 and TRP140 and observed comparable immunoreactivity. Many of these proteins were conserved in different E. canis strains. Multiple linear antibody epitopes were mapped in a highly conserved TRP (Ecaj_0126), including within the tandem repeat domain. Temporal antibody responses were examined, and multiple proteins reacted with antibodies in sera as early as 21 days post experimental infection. Host-specific expression of the proteins was examined which revealed that some proteins exhibited higher expression in mammalian cells, while others in tick cells. This study has identified new immunodiagnostic candidates that exhibit different host expression patterns, information which may be useful for developing ultrasensitive immunodiagnostics and effective vaccines for CME. [ABSTRACT FROM AUTHOR]

Although a fourth dose of SARS-CoV-2 vaccine was shown to be effective, the immunogenicity of a fifth dose in immunocompetent individuals had not been well described. This was a prospective observational cohort study of previously vaccinated healthcare workers at a single tertiary hospital in Israel. Individuals were administered up to three booster doses of the BNT162b2 mRNA vaccine (i.e., up to five overall doses), during the period between July 2021 and January 2023. Immunogenicity was assessed using the SARS-CoV-2 IgG (sCOVG) semi-quantitative assay, performed at several time points. The cohort consisted of 162 individuals (median age 69 years, 62% female). Of these, 104 (64%) received four doses and 58 (36%) received five doses. Anti-SARS-CoV-2 antibody levels increased in all cases, regardless of the baseline levels. The fold-change increase in the mean sCOVG index was 29.2 (SD 2.6) after the third vaccine, 3.8 (SD 2.4) after the fourth vaccine, and 3.6 (SD 3.0) after the fifth vaccine. A waning effect over time was seen in 78% and 43% of participants for the third and fourth doses, respectively. Adverse events following the fifth dose were limited and mild. Similar to previous booster vaccines, a fifth dose of BNT162b2 is immunogenic and safe in healthy individuals, although the clinical implications remain unclear. [ABSTRACT FROM AUTHOR]

The beneficial effects of polyethylene glycol (PEG)-conjugated therapeutics, such as increased half-life, solubility, stability, and decreased immunogenicity, have been well described. There have been concerns, however, about adverse outcomes with their use, but understanding of those adverse outcomes is still relatively limited. The present study aimed to characterize adverse outcomes associated with PEGylation of protein-based therapeutics on immunogenicity, pharmacologic properties, and safety. A targeted review of English language articles published from 1990 to September 29, 2023, was conducted. Of the 29 studies included in this review, 18 reported adverse safety outcomes such as hematologic complications, hepatic toxicity, injection site reactions, arthralgia, nausea, infections, grade 3 or 4 adverse events (AEs), and AE-related discontinuations and dose modifications. Fifteen studies reported immunogenicity-related outcomes, such as the prevalence of pre-existing antibodies to PEG, treatment-emergent antibody response, and hypersensitivity reactions to PEGylated drugs. Seven studies reported pharmacological outcomes such as increased clearance and reduced activity in response to PEGylated drugs. This review aims to contribute to a balanced view of PEGylated therapies by summarizing the adverse outcomes or lack of benefit associated with PEGylated therapeutics reported in the literature. We identified several studies characterizing adverse outcomes, pharmacological effects, and immunogenicity associated with the use of PEGylated therapeutics. Our findings suggest that using PEGylated therapeutics may require careful monitoring for adverse safety outcomes, including screening and monitoring for pre-existing antibodies and those induced in response to PEGylated therapy, as well as monitoring and adjusting the dosing of PEGylated therapeutics. [ABSTRACT FROM AUTHOR]

Coevolution of parasites with their hosts may lead to balancing selection on genes involved in determining the specificity of host–parasite interactions, but examples of such specific interactions in wild vertebrates are scarce. Here, we investigated whether the polymorphic outer surface protein C (OspC), used by the Lyme disease agent, Borrelia afzelii, to manipulate vertebrate host innate immunity, interacts with polymorphic major histocompatibility genes (MHC), while concurrently eliciting a strong antibody response, in one of its main hosts in Europe, the bank vole. We found signals of balancing selection acting on OspC, resulting in little differentiation in OspC variant frequencies between years. Neither MHC alleles nor their inferred functional groupings (supertypes) significantly predicted the specificity of infection with strains carrying different OspC variants. However, we found that MHC alleles, but not supertypes, significantly predicted the level of IgG antibodies against two common OspC variants among seropositive individuals. Our results thus indicate that MHC alleles differ in their ability to induce antibody responses against specific OspC variants, which may contribute to selection of OspC polymorphism by the vole immune system. [ABSTRACT FROM AUTHOR]

Allergy is a complex array of diseases influenced by innate and adaptive immunity, genetic polymorphisms, and environmental triggers. Atopic dermatitis is a chronic inflammatory skin disease characterized by barrier defects and immune dysregulation, sometimes leading to asthma and food allergies because of the atopic march. During atopic skin inflammation, Langerhans cells and dendritic cells (DCs) in the skin capture and deliver allergen information to local lymph nodes. DCs are essential immune sensors coordinating immune reactions by capturing and presenting antigens to T cells. In the context of allergic responses, DCs play a crucial role in instructing two types of helper T cells—type 2 helper T (Th2) cells and follicular helper T (TFH) cells—in allergic responses and IgE antibody responses. In skin sensitization, the differentiation and function of Th2 cells and TFH cells are influenced by skin-derived factors, including epithelial cytokines, chemokines, and signalling pathways to modify the function of migratory DCs and conventional DCs. In this review, we aim to understand the specific mechanisms involving DCs in allergic responses to provide insights into the pathogenesis of allergic diseases and potential therapeutic strategies. [ABSTRACT FROM AUTHOR]

Malaria blood‐stage parasite is a critical pathogenic stage responsible for serious adverse outcomes in pregnant women and their neonates. Immunoglobulin G (IgG) antibody responses specific to various asexual blood‐stage antigens were well reported in non‐pregnant individuals. However, little is still known during placental malaria. To assess the antibody responses specific to Plasmodium falciparum‐derived MSP3 and UB05 malaria vaccine candidates in mother‐neonate couples, mother's peripheral blood and neonate's cord blood samples were collected at delivery. After malaria diagnostic, plasma levels of IgG and IgG subclass responses specific to UB05, MSP3 and UB05‐MSP3 were determined using ELISA. As outcomes, both mothers and neonates had significantly higher IgG responses to UB05 and UB05‐MSP3 compared to anti‐MSP3 IgG (p < 0.05), irrespective of malaria status. Significant negative correlations were observed between IgG levels specific to the three antigens and parasitaemia (p < 0.01). Anti‐UB05 and anti‐UB05‐MSP3 IgG levels in neonates showed a significant positive correlation with the corresponding mothers' antibodies (rs = 0.25 with p = 0.04; rs = 0.31 with p = 0.01, respectively). UB05MSP3‐specific IgG3 and IgG1 subclass responses were significantly higher than the IgG4 subclass (p < 0.01). The neonates IgG1 and IgG3 levels positively correlated with the corresponding antibody subclasses of mothers. These findings suggest an association between UB05 and UB05‐MSP3‐specific antibody responses and malaria control during pregnancy. Maternal–foetal transfer of MSP3 and UB05‐specific IgG occurs during pregnancy, suggesting the interest in the future malaria vaccination strategies in pregnant women to generate early protective immunity in baby against malaria. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a systemic autoimmune disease driven by highly active autoantibody‐producing B cells. Activation of B cells is maintained within ectopic germinal centres found in affected joints. Fibroblast‐like synoviocytes (FLS) present in inflamed joints support B‐cell survival, activation, and differentiation. CD27+ memory B cells and naive B cells show very different responses to activation, particularly by CD40 ligand (CD40L). We show that FLS‐dependent activation of human B cells is dependent on interleukin‐6 (IL‐6) and CD40L. FLS have been shown to activate both naive and memory B cells. Whether the activating potential of FLS is different for naive and memory B cells has not been investigated. Our results suggest that FLS‐induced activation of B cells is dependent on IL‐6 and CD40L. While FLS are able to induce plasma cell differentiation, isotype switching, and antibody production in memory B cells, the ability of FLS to activate naive B cells is significantly lower. [ABSTRACT FROM AUTHOR]

In immuno-oncology, the focus has traditionally been on αβ T cells, and immune checkpoint inhibitors that primarily target PD-1 or CTLA4 in these lymphocytes have revolutionized the management of multiple human malignancies. However, recent research highlights the crucial role of B cells and the antibodies they produce in antagonizing malignant progression, offering new avenues for immunotherapy. Our group has demonstrated that dimeric Immunoglobulin A can penetrate tumor cells, neutralize oncogenic drivers in endosomes, and expel them from the cytosol. This mechanistic insight suggests that engineered antibodies targeting this pathway may effectively reach previously inaccessible targets. Investigating antibody production within intratumoral germinal centers and understanding the impact of different immunoglobulins on malignant progression could furnish new tools for the therapeutic arsenal, including the development of tumor-penetrating antibodies. This review aims to elucidate the nature of humoral adaptive immune responses in human cancer and explore how they could herald a new era of immunotherapeutic modalities. By expanding the scope of antitumor immunotherapies, these approaches have the potential to benefit a broader range of cancer patients, particularly through the utilization of tumor cell–penetrating antibodies. [ABSTRACT FROM AUTHOR]

Background: Plasmodium vivax is the dominant Plasmodium spp. causing malaria throughout tropical and sub-tropical countries. Humoral immunity is induced during P. vivax infection. However, data on longevity of antibody and memory B cell (MBC) responses is lacking. Follicular helper T cells (Tfh) are drivers of high-affinity and long-lived antibody responses. Understanding of Tfh-mediated immunity against malaria is valuable for vaccine development. Methodology/Principal findings: We enrolled 31 acutely infected P. vivax patients in low malaria transmission areas of Thailand to detect frequencies, phenotypes and kinetics of different subsets of circulating Tfh (cTfh) and MBCs, and to evaluate their association with humoral immunity following natural P. vivax infection. Expansion of cTfh2 cells, activated and atypical MBCs were shown during acute malaria. To relate increased cTfh2 cells to humoral immunity, P. vivax-specific MBCs and antibodies were assessed. High anti-PvCSP and -PvDBPII seropositivity was detected and most subjects produced MBCs specific to these antigens. The increased cTfh2 cells were positively related to atypical MBCs, plasmablasts/plasma cells, and anti-PvDBPII IgM and IgG levels. Distributions of memory cTfh cell subsets were altered from central memory (CM) to effector memory (EM) during infection. The highest ratios of cTfh-EM/cTfh-CM were represented in cTfh2 cells. Positive correlation of cTfh17-EM with activated and atypical MBCs was observed, while cTfh2-CM and cTfh17-CM cells were positively related to PvDBPII-specific MBCs and IgM levels. Conclusions/Significance: Present study demonstrated that P. vivax infection induced cTfh polarization into cTfh2 subset, and alteration of memory cTfh2 phenotype from CM to EM phase. These P. vivax-induced cTfh responses significantly associated with generation of MBCs and antibody responses. Therefore, cTfh2 cells might possibly influence humoral immunity by inducing expansion of activated and atypical MBCs, and by generating P. vivax-specific MBCs and antibody responses following natural infection. Author summary: Naturally acquired immunity to malaria relies on the development of MBCs and long-lived plasma cells that serve as the source of antibody responses that inhibit parasite invasion. To date, information is limited regarding the role of Tfh cells in supporting development of MBCs and antibodies against P. vivax infection, particularly in the context of natural malaria exposure. Here, we identified subsets of cTfh cells that involved in the generation of P. vivax-specific MBC and antibody responses. We found that P. vivax infection induced an expansion of cTfh2 cells. The cTfh2 cell responses were positively related to an increased frequency of activated and atypical MBCs, and plasma cells, as well as P. vivax-specific antibody levels. Moreover, phenotype of memory cTfh2 cells was changed from CM to EM phase during infection. The alteration of cTfh17-EM cells was significantly related to expansion of activated and atypical MBCs, while the presence of cTfh2-CM and cTfh17-CM cells was positively related to P. vivax-specific MBCs and IgM responses. Data from this study suggests a role of cTfh2 cells in contribution to the development of P. vivax-specific MBCs and antibody responses. [ABSTRACT FROM AUTHOR]

Plasma RNAemia, delayed antibody responses and inflammation predict COVID-19 outcomes, but the mechanisms underlying these immunovirological patterns are poorly understood. We profile 782 longitudinal plasma samples from 318 hospitalized patients with COVID-19. Integrated analysis using k-means reveals four patient clusters in a discovery cohort: mechanically ventilated critically-ill cases are subdivided into good prognosis and high-fatality clusters (reproduced in a validation cohort), while non-critical survivors segregate into high and low early antibody responders. Only the high-fatality cluster is enriched for transcriptomic signatures associated with COVID-19 severity, and each cluster has distinct RBD-specific antibody elicitation kinetics. Both critical and non-critical clusters with delayed antibody responses exhibit sustained IFN signatures, which negatively correlate with contemporaneous RBD-specific IgG levels and absolute SARS-CoV-2-specific B and CD4+ T cell frequencies. These data suggest that the "Interferon paradox" previously described in murine LCMV models is operative in COVID-19, with excessive IFN signaling delaying development of adaptive virus-specific immunity. The role of IFN signaling in SARS-CoV-2 infection and outcome is still debated. Here, the authors longitudinally profiled plasma samples from hospitalized patients and show that a persistent inflammatory response is linked to delayed generation of adaptive immunity and increased risk of death when coupled with severe infection. [ABSTRACT FROM AUTHOR]

Introduction: Systemic sclerosis (SSc) is an autoimmune disease characterized by antinuclear antibody production, which has been linked to an excess of apoptotic cells, normally eliminated by macrophages through efferocytosis. Additionally, circulating levels of CXCL4, a novel SSc biomarker, correlate with more severe fibrotic manifestations of the disease. Considering the defective efferocytosis of macrophages in SSc and the CXCL4-related M4 macrophage phenotype, we hypothesized that CXCL4 could be involved in the alteration of phagocytic functions of macrophages in SSc, including LC3-associated phagocytosis (LAP), another phagocytic process requiring autophagy proteins and contributing to immune silencing. Methods: In this study, CXCL4 levels were measured by ELISA in vitro in the serum of SSc patients, and also in vivo in the serum and lungs of C57BL/6J SSc mice induced by intradermal injections of hypochloric acid (HOCl) or Bleomycin (BLM), with evaluation of M4 markers. Circulating monocytes from healthy donors were also differentiated in vitro into M4 monocytes-derived macrophages (MDMs) in the presence of recombinant CXCL4. In M4-MDMs, phagocytosis of fluorescent beads and expression level of efferocytic receptors were evaluated by flow cytometry in vitro, while efferocytosis of pHrodo-stained apoptotic Jurkat cells was evaluated by real-time fluorescence microscopy. LAP quantification was made by fluorescence microscopy in M4-MDMs exposed to IgG-coated beads as well as apoptotic Jurkat cells. Results: Our results demonstrated that efferocytosis was significantly reduced in M0-MDMs from healthy donors exposed to the CXCL4-rich plasma of SSc patients. In vivo, CXCL4 expression was increased in the lungs of both SScmouse models, along with elevated M4 markers, while efferocytosis of BLM-mice alveolar macrophages was decreased. In vitro, M4-MDMs exhibited reduced efferocytosis compared to M0-MDMs, notably attributable to lower CD36 receptor expression and impaired phagocytosis capacities, despite enhanced LAP. Autophagic gene expression was increased both in vitro in SSc MDMs and in vivo in BLM mice, thus acting as a potential compensatory mechanism. Discussion: Altogether, our results support the role of CXCL4 on the impaired efferocytosis capacities of human macrophages from SSc patients and in SSc mice. [ABSTRACT FROM AUTHOR]

Plasmodium vivax malaria causes significant public health problems in endemic regions. Considering the rapid spread of drug-resistant parasite strains and the development of hypnozoites in the liver with potential for relapse, development of a safe and effective vaccine for preventing, controlling, and eliminating the infection is critical. Immunity to malaria is mediated by antibodies that inhibit sporozoite or merozoite invasion into host cells and protect against clinical disease. Epidemiologic data from malaria endemic regions show the presence of naturally acquired antibodies to P. vivax antigens during and following infection. But data on the persistence of these antibodies, development of P. vivax-specific memory B cells (MBCs), and their relation to reduction of malaria severity and risk is limited. This review provides an overview of the acquisition and persistence of naturally acquired humoral immunity to P. vivax infection. Also, we summarize and discuss current progress in assessment of immune responses to candidate vaccine antigens in P. vivax patients from different transmission settings. Longitudinal studies of MBC and antibody responses to these antigens will open new avenues for developing vaccines against malaria infection and its transmission. Author summary: Despite the Plasmodium vivax parasite causing a large proportion of the global malaria burden, it has been neglected by much of the research world. Vaccines that can effectively induce strong and long-lasting antibody and memory B cell (MBC) responses are necessary for disease control and elimination, as they are crucial for blocking subsequent infection. The development and longevity of antibodies and MBC responses against different stages of P. vivax have been studied in various transmission settings. Some candidate antigens have been investigated in clinical trials with promising results. Previous reports have provided evidence of antibody acquisition to representative candidate P. vivax antigens from pre-erythrocytic, blood and transmission stages. However, evidence of durable antibody responses and development of P. vivax-specific MBCs is still lacking. Recently, expansion of atypical MBCs along with up-regulation of inhibitory receptors and reduced BCR signaling has been demonstrated and associated with short-lived antibody responses, culminating in impaired humoral immunity. Collectively, the capacity of P. vivax antigens to induce naturally acquired humoral immunity has been addressed. The results allow optimization of vaccine design to enhance immune responses to the parasite and protect against disease. [ABSTRACT FROM AUTHOR]

Background: Dexamethasone is currently administered for Coronavirus disease 2019(COVID-19); however, there are concerns about its effect on specific antibodies' production. The aim of this study was to evaluate whether specific antibodies were affected by COVID-19 severity and corticosteroid treatment. Methods: Of 251 confirmed COVID-19 patients admitted to our hospital between January 26 and August 10, 2020, the early period of the pandemic, 75 patients with sera within 1 month of onset and 1 month or longer were included in the research. A total of 253 serum samples from these patients were collected. The levels of specific antibodies for severe acute respiratory syndrome coronavirus 2(SARS-CoV-2), immunoglobulin G (IgG) and M (IgM), were measured retrospectively. The results were compared separately of each COVID-19 severity, and with or without corticosteroid treatment. Results: Among the 75 patients, 47, 18, and 10 had mild, moderate, and severe disease, respectively. The median age was 53.0 years and 22 (29%) were women. The most common comorbidities were hypertension and dyslipidemia. Corticosteroids were administered to 20 (27%) and 10 (53%), patients with moderate and severe disease, respectively. The positivity rates IgM increased first, and IgG was almost always positive after day 16, regardless of the severity of COVID-19. On days 6–10, both IgG and IgM positivity rates were higher in patients with moderate disease than in those with mild or severe disease. In patients with moderate disease, IgG positivity was similar over time, regardless of corticosteroid treatment. Conclusions: In COVID-19 patients, specific IgG is positive and maintained for a long period of time, even after corticosteroid treatment. The effect of corticosteroid treatment in a COVID-19 epidemiological study using specific IgG antibodies was considered minor. COVID-19 patients were more likely to receive oxygen if IgM was positive 1 week after onset, but not mechanical ventilation. IgM measurement 1 week after onset may predict COVID-19 severity. [ABSTRACT FROM AUTHOR]

Despite annual vaccination, influenza B viruses (IBV) continue to cause significant morbidity and mortality in humans. We have found that IBV infection resulted in a weaker innate and adaptive immune response than influenza A viruses (IAV) in ferrets. To understand and overcome the weak immune responses to IBV in ferrets, we administered type-I or type-III interferon (IFN) to ferrets following infection or vaccination and evaluated their effects on the immune response. IFN signaling following viral infection plays an important role in the initial innate immune response and affects subsequent adaptive immune responses. In the respiratory tract, IFN lambda (IFNL) has regulatory effects on adaptive immunity indirectly through thymic stromal lymphopoietin (TSLP), which then acts on immune cells to stimulate the adaptive response. Following IBV infection or vaccination, IFN treatment (IFN-Tx) upregulated gene expression of early inflammatory responses in the upper respiratory tract and robust IFN, TSLP, and inflammatory responses in peripheral blood cells. These responses were sustained following challenge or vaccination in IFN-Tx animals. Serum IFNL and TSLP levels were enhanced in IFN-Tx animals following challenge/rechallenge over mock-Tx; however, this difference was not observed following vaccination. Antibody responses in serum of IFN-Tx animals following IBV infection or vaccination increased more quickly and to higher titers and were sustained longer than mock-Tx animals over 3 months. Following rechallenge of infected animals 3 months post treatment, antibody levels remained higher than mock-Tx. However, IFN-Tx did not have an effect on antibody responses following challenge of vaccinated animals. A strong direct correlation was found between TSLP levels and antibody responses following challenge-rechallenge and vaccination-challenge indicating it as a useful tool for predicting adaptive immune responses following IBV infection or vaccination. The effects of IFN on strengthening both innate and adaptive responses to IBV may aid in development of more effective treatments following infection and improved influenza vaccines. [ABSTRACT FROM AUTHOR]

Malaria represents a challenging global public health task, with Plasmodium vivax being the predominant parasite in Brazil and the most widely distributed species throughout the world. Developing a vaccine against P. vivax malaria demands innovative strategies, and targeting gametocyte antigens shows promise for blocking transmission prevention. Among these antigens, Pvs47, expressed in gametocytes, has shown remarkable efficacy in transmission blocking. However, remains underexplored in vaccine formulations. This study employed in silico methods to comprehensively characterize the physicochemical properties, structural attributes, epitope presence, and conservation profile of Pvs47. Additionally, we assessed its antigenicity in individuals exposed to malaria in endemic Brazilian regions. Recombinant protein expression occurred in a eukaryotic system, and antigenicity was evaluated using immunoenzymatic assays. The responses of naturally acquired IgM, total IgG, and IgG subclasses were analyzed in three groups of samples from Amazon region. Notably, all samples exhibited anti-Pvs47 IgM and IgG antibodies, with IgG3 predominating. Asymptomatic patients demonstrated stronger IgG responses and more diverse subclass responses. Anti-Pvs47 IgM and IgG responses in symptomatic individuals decrease over time. Furthermore, we observed a negative correlation between anti-Pvs47 IgM response and gametocytemia in samples of symptomatic patients, indicating a gametocyte-specific response. Additionally, negative correlation was observed among anti-Pvs47 antibody response and hematocrit levels. Furthermore, comparative analysis with widely characterized blood antigens, PvAMA1 and PvMSP119, revealed that Pvs47 was equally or more recognized than both proteins. In addition, there is positive correlation between P. vivax blood asexual and sexual stage immune responses. In summary, our study unveils a significant prevalence of anti-Pvs47 antibodies in diverse Amazonian samples and the importance of IgM response for gametocytes depuration. These findings regarding the in silico characterization and antigenicity of Pvs47 provide crucial insights for potential integration into P. vivax vaccine formulations. [ABSTRACT FROM AUTHOR]

The serine/threonine-specific protein kinases (STKs) are important for cell survival, proliferation, differentiation, and apoptosis. In B cells, these kinases play indispensable roles in regulating important cellular functions. Multiple studies on human and other animal cells have shown that multiple STKs are involved in different stages of B cell development and antibody production. However, how STKs affect B cell development and function is still not completely understood. Considering that B cells are clinically important in immunity and diseases, our understanding of STKs' roles in B cells is in great need of investigation with current technologies. Investigating serine/threonine kinases will not only deepen our insight into B cell-related disorders but also facilitate the identification of more effective drug targets for conditions like lymphoma and systemic lupus erythematosus. [ABSTRACT FROM AUTHOR]

Current COVID-19 vaccines provide robust protection against severe disease but minimal protection against acquisition of infection. Intramuscularly administered COVID-19 vaccines induce robust serum neutralizing antibodies (NAbs), but their ability to boost mucosal immune responses remains to be determined. In this study, we show that the XBB.1.5 messenger RNA (mRNA) boosters result in increased serum neutralization to multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants in humans, including the dominant circulating variant JN.1. In contrast, we found that the XBB.1.5 mRNA booster did not augment mucosal NAbs or mucosal IgA responses, although acute SARS-CoV-2 XBB infection substantially increased mucosal antibody responses. These data demonstrate that current XBB.1.5 mRNA boosters substantially enhance peripheral antibody responses but do not robustly increase mucosal antibody responses. Our data highlight a separation between the peripheral and mucosal immune systems in humans and emphasize the importance of developing next-generation vaccines to augment mucosal immunity to protect against respiratory virus infections. Editor's summary: mRNA vaccines for SARS-CoV-2 elicit robust antibody responses in the circulation, which aid in protection from severe disease. However, the extent to which mRNA vaccines, which are delivered intramuscularly, can elicit mucosal immune responses is unclear. In a pair of papers, Declercq et al. and Lasrado et al. come to distinct conclusions. Using human nasal swab samples in both studies, Declercq et al. show that repeated vaccination for SARS-CoV-2 promotes neutralizing antibodies in the nose, whereas Lasrado et al. observed no obvious increase in neutralizing antibody titers after booster vaccination. These differing results may be due to the number of SARS-CoV-2 vaccinations or exposures, time since last exposure, and experimental approaches, but this pair of papers underscores the need to better understand the mucosal immune response in humans. —Courtney Malo [ABSTRACT FROM AUTHOR]

To prevent infection by respiratory viruses and consequently limit virus circulation, vaccines need to promote mucosal immunity. The extent to which the currently used messenger RNA (mRNA)–based COVID-19 vaccines induce mucosal immunity remains poorly characterized. We evaluated mucosal neutralizing antibody responses in a cohort of 183 individuals. Participants were sampled at several time points after primary adenovirus vector–based or mRNA-based COVID-19 vaccination and after mRNA-based booster vaccinations. Our findings revealed that repeated vaccination with mRNA boosters promoted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies in nasal secretions. Nasal and serum neutralizing antibody titers of both IgG and IgA isotypes correlated to one another. We investigated the source of these mucosal antibodies in a mouse model wherein mice received repeated mRNA vaccines for SARS-CoV-2. These experiments indicated that neutralizing antibody–producing cells reside in the spleen and bone marrow, whereas no proof of tissue homing to the respiratory mucosa was observed, despite the detection of mucosal antibodies. Serum transfer experiments confirmed that circulating antibodies were able to migrate to the respiratory mucosa. Collectively, these results demonstrate that, especially upon repeated vaccination, the currently used COVID-19 mRNA vaccines can elicit mucosal neutralizing antibodies and that vaccination might also stimulate mucosal immunity induced by previous SARS-CoV-2 infection. Moreover, migration of circulating antibodies to the respiratory mucosa might be a main mechanism. These findings advance our understanding of mRNA vaccine–induced immunity and have implications for the design of vaccine strategies to combat respiratory infections. Editor's summary: mRNA vaccines for SARS-CoV-2 elicit robust antibody responses in the circulation, which aid in protection from severe disease. However, the extent to which mRNA vaccines, which are delivered intramuscularly, can elicit mucosal immune responses is unclear. In a pair of papers, Declercq et al. and Lasrado et al. come to distinct conclusions. Using human nasal swab samples in both studies, Declercq et al. show that repeated vaccination for SARS-CoV-2 promotes neutralizing antibodies in the nose, whereas Lasrado et al. observed no obvious increase in neutralizing antibody titers after booster vaccination. These differing results may be due to the number of SARS-CoV-2 vaccinations or exposures, time since last exposure, and experimental approaches, but this pair of papers underscores the need to better understand the mucosal immune response in humans. —Courtney Malo [ABSTRACT FROM AUTHOR]

The influenza neuraminidase (NA) is a potential target for the development of a next-generation influenza vaccine, but its antigenicity is not well understood. Here, we isolate an anti-N6 human monoclonal antibody, named 18_14D, from an H5N6 avian influenza virus (AIV) infected patient. The antibody weakly inhibits enzymatic activity but confers protection in female mice, mainly via ADCC function. The cryo-EM structure shows that 18_14D binds to a unique epitope on the lateral surface of the N6 tetramer, preventing the formation of tightly closed NA tetramers. These findings contribute to the molecular understanding of protective immune responses to NA of AIVs in humans and open an avenue for the rational design of NA-based vaccines. Understanding the antibody response to influenza neuraminidase (NA) can identify protective epitopes. Here, the authors isolate an antibody from an H5N6 infected patient, characterize the epitope on the N6 tetramer, and show that it's protective in female mice. [ABSTRACT FROM AUTHOR]

Current cancer treatment strategies continue to face significant challenges, primarily due to tumor relapse, drug resistance, and low treatment efficiency. These issues arise because certain tumor cells adapt to the host immune microenvironment and evade the immune system. This study presents a new cancer immunotherapy strategy using serum-based antibodies from mice exposed to mouse cutaneous squamous cell carcinoma (mCSCC). The experiment was conducted in three stages. In the first stage, mCSCC cells were isolated and expanded cultured from DMBA/TPA-induced mCSCC. In the second stage, these expanded tumor cells were injected into healthy mice to stimulate the production of anti-tumor antibodies. In the final stage, therapeutic serum was extracted from these healthy mice and reintroduced into the tumor-bearing mice. An ELISA assay was utilized to analyze the levels of p53, Bcl-xL, NF-κB, and Bax. The results showed that the serum treatment not only reduced tumor volume but also reversed changes in p53, Bcl-xL, NF-κB, and Bax. In conclusion, this study developed a new immunotherapeutic strategy for treating mCSCC. However, further research is needed to fully comprehend the mechanism of this serum treatment. [ABSTRACT FROM AUTHOR]

Background The kinetics and durability of T-cell responses to SARS-CoV-2 in children are not well characterized. We studied a cohort of children aged 6 months to 20 years with COVID-19 in whom peripheral blood mononuclear cells and sera were archived at approximately 1, 6, and 12 months after symptom onset. Methods We compared antibody responses (n = 85) and T-cell responses (n = 30) to nucleocapsid (N) and spike (S) glycoprotein over time across 4 age strata: 6 months to 5 years and 5–9, 10–14, and 15–20 years. Results N-specific antibody responses declined over time, becoming undetectable in 26 (81%) of 32 children by approximately 1 year postinfection. Functional breadth of anti-N CD4+ T-cell responses also declined over time and were positively correlated with N-antibody responses (Pearson r =.31, P =.008). CD4+ T-cell responses to S displayed greater functional breadth than N in unvaccinated children and, with neutralization titers, were stable over time and similar across age strata. Functional profiles of CD4+ T-cell responses against S were not significantly modulated by vaccination. Conclusions Our data reveal durable age-independent T-cell immunity to SARS-CoV-2 structural proteins in children over time following COVID-19 infection as well as S-antibody responses in comparison with declining antibody responses to N. [ABSTRACT FROM AUTHOR]

Background Rapidly evolving RNA viruses, such as human norovirus, generate extraordinary sequence diversity, posing a significant challenge to vaccine design. This diversity, coupled with short-lasting natural immunity, leads to reinfection throughout one's lifetime. How reexposure shapes humoral immunity to future norovirus strains remains incompletely understood. Methods We profiled the antibody responses following 2 community gastroenteritis outbreaks with GII.2 and GII.6 noroviruses in 1971. Using diverse virus-like particles (VLPs), enzyme-linked immunosorbent assay (ELISA), and carbohydrate-blocking assays (surrogate for neutralization), we examined the antibody response at acute and convalescent timepoints following GII.6 infection. Results Convalescent sera displayed strong homologous blocking, demonstrating a 5-fold increase in GII.6 carbohydrate blockade over acute samples, and broad blocking of diverse archival and modern GII.6 noroviruses. Convalescent sera displayed limited carbohydrate blocking of heterotypic VLPs, despite high ELISA binding titers. Select individuals developed broad cross-genotype blockade, but this response was established before the second outbreak. Finally, we applied a novel competitive carbohydrate-blocking assay to demonstrate the epitope specificity and discrete compartments of the neutralizing response. Conclusions Our data show that infection generates narrow, focused immunity directed toward the infecting genotype. We did detect broad cross-blocking in specific individuals, but these responses could be attributed to diverse, genotype-specific antibodies predating GII.6 infection. [ABSTRACT FROM AUTHOR]

Rapid and efficient cell line development (CLD) process is essential to expedite therapeutic protein development. However, the performance of widely used glutamine‐based selection systems is limited by low selection efficiency, stringency, and the inability to select multiple genes. Therefore, an AND‐gate synthetic selection system is rationally designed using split intein‐mediated protein ligation of glutamine synthetase (GS) (SiMPl‐GS). Split sites of the GS are selected using a computational approach and validated with GS‐knockout Chinese hamster ovary cells for their potential to enable cell survival in a glutamine‐free medium. In CLD, SiMPl‐GS outperforms the wild‐type GS by selectively enriching high producers. Unlike wild‐type GS, SiMPl‐GS results in cell pools in which most cells produce high levels of therapeutic proteins. Harnessing orthogonal split intein pairs further enables the selection of four plasmids with a single selection, streamlining multispecific antibody‐producing CLD. Taken together, SiMPl‐GS is a simple yet effective means to expedite CLD for therapeutic protein production. [ABSTRACT FROM AUTHOR]

Background: Older persons elicit heterogeneous antibody responses to vaccinations that generally are lower than those in younger, healthier individuals. As older age and certain comorbidities can influence these responses we aimed to identify health-related variables associated with antibody responses after repeated SARS-CoV-2 vaccinations and their persistence thereafter in SARS-CoV-2 infection-naïve and previously infected older persons. Method: In a large longitudinal study of older persons of the general population 50 years and over, a sub-cohort of the longitudinal Doetinchem cohort study (n = 1374), we measured IgG antibody concentrations in serum to SARS-CoV-2 Spike protein (S1) and Nucleoprotein (N). Samples were taken following primary vaccination with BNT162b2 or AZD1222, pre- and post-vaccination with a third and fourth BNT162b2 or mRNA-1273 (Wuhan), and up to a year after a fifth BNT162b2 bivalent (Wuhan/Omicron BA.1) vaccine. Associations between persistence of antibody concentrations over time and age, sex, health characteristics including cardiometabolic and inflammatory diseases as well as a frailty index were tested using univariable and multivariable models. Results: The booster doses substantially increased anti-SARS-CoV-2 Spike S1 (S1) antibody concentrations in older persons against both the Wuhan and Omicron strains. Older age was associated with decreased antibody persistence both after the primary vaccination series and up to 1 year after the fifth vaccine dose. In infection-naïve persons the presence of inflammatory diseases was associated with an increased antibody response to the third vaccine dose (Beta = 1.53) but was also associated with reduced persistence over the 12 months following the fifth (bivalent) vaccine dose (Beta = -1.7). The presence of cardiometabolic disease was associated with reduced antibody persistence following the primary vaccination series (Beta = -1.11), but this was no longer observed after bivalent vaccination. Conclusion: Although older persons with comorbidities such as inflammatory and cardiometabolic diseases responded well to SARS-CoV-2 booster vaccinations, they showed a reduced persistence of these responses. This might indicate that especially these more vulnerable older persons could benefit from repeated booster vaccinations. [ABSTRACT FROM AUTHOR]

Neutralising antibodies against the SARS-CoV-2 spike (S) protein are major determinants of protective immunity, though insufficient antibody responses may cause the emergence of escape mutants. We studied the humoral immune response causing intra-host evolution in a B-cell depleted, haemato-oncologic patient experiencing clinically severe, prolonged SARS-CoV-2 infection with a virus of lineage B.1.177.81. Following bamlanivimab treatment at an early stage of infection, the patient developed a bamlanivimab-resistant mutation, S:S494P. After five weeks of apparent genetic stability, the emergence of additional substitutions and deletions within the N-terminal domain (NTD) and the receptor binding domain (RBD) of S was observed. Notably, the composition and frequency of escape mutations changed in a short period with an unprecedented dynamic. The triple mutant S:Delta141-4 E484K S494P became dominant until virus elimination. Routine serology revealed no evidence of an antibody response in the patient. A detailed analysis of the variant-specific immune response by pseudotyped virus neutralisation test, surrogate virus neutralisation test, and immunoglobulin-capture enzyme immunoassay showed that the onset of an IgM-dominated antibody response coincided with the appearance of escape mutations. The formation of neutralising antibodies against S:Delta141-4 E484K S494P correlated with virus elimination. One year later, the patient experienced clinically mild re-infection with Omicron BA.1.18, which was treated with sotrovimab and resulted in an increase in Omicron-reactive antibodies. In conclusion, the onset of an IgM-dominated endogenous immune response in an immunocompromised patient coincided with the appearance of additional mutations in the NTD and RBD of S in a bamlanivimab-resistant virus. Although virus elimination was ultimately achieved, this humoral immune response escaped detection by routine diagnosis and created a situation temporarily favouring the rapid emergence of various antibody escape mutants with known epidemiological relevance. Author summary: In the immunocompromised host, prolonged infection and insufficient antibody responses favour the emergence of highly mutated SARS-CoV-2 variants. To better understand the selective pressure exerted by antiviral antibodies, we characterised the variant-specific humoral immune response and resulting intra-host evolution of SARS-CoV-2 in a B-lymphocyte-depleted patient experiencing severe infection. Treatment with a monoclonal antibody early in infection led to the selection and outgrowth of resistant virus. As their B-cell function recovered, the patient mounted an IgM-dominated antiviral antibody response, the onset of which closely correlated with the appearance of additional escape mutations within the spike protein. The strength and breadth of this antibody response gradually increased, resulting in the selection of a variant carrying several escape mutations within spike. The formation of neutralising antibodies against this variant resulted in virus elimination. Our study provides new insights into the selection process of viral escape mutants in immunocompromised patients. The resuming humoral immunity against SARS-CoV-2 can be dominated by IgM. This immune response is poorly detectable with routine diagnostic procedures yet may trigger and drive substantial viral intra-host evolution. Determination of antiviral antibody responses and correlating them with intra-host evolution may provide a better picture of the adaptability of currently circulating SARS-CoV-2 variants. [ABSTRACT FROM AUTHOR]

During the production of bispecific antibodies (bsAbs), nonspecific pairing results in low yields of target bsAb molecules, an issue known as the "mispairing problem." Several antibody engineering techniques have been developed to overcome mispairing issues. Here, we introduce "bsAb by external pairing and excision" (BAPE), a novel chain pairing method that induces specific chain pairing by fusing external SpyCatcher/Tag and SnoopCatcher/Tag units. These tags are then removed via protease cleavage. In this study, we applied this method to force the correct pairings of heavy and light chains while the heavy-chain pairing was achieved by the Knobs-into-Holes mutation. We then confirmed the formation of interchain bridges with covalent isopeptide bonds. Both anti-CD3/anti-Her2 and anti-CD3/anti-EGFR bsAbs displayed satisfactory target binding activities and in vitro cell-killing activity with activated T-cells. [ABSTRACT FROM AUTHOR]

Epstein–Barr virus (EBV) is an oncogenic virus associated with various malignancies, including classical Hodgkin lymphoma (cHL). Despite its known association, the specific role of humoral immune response to EBV remains poorly characterized in cHL. To address this, we conducted a study using a custom protein microarray to measure the antibody responses in cHL patients and matched healthy controls recruited from an East‐Asian hospital‐based case–control study. We identified 16 IgG antibodies significantly elevated in EBV‐positive cHL compared with controls, defining an "East‐Asian antibody signature of EBV‐positive cHL." We evaluated responses against these 16 antibodies in a distinct European population, leveraging data from our previous European cHL case–control study from the UK, Denmark, and Sweden. A subset of antibodies (14/16, 87.5%) from the "East‐Asian antibody signature of EBV‐positive cHL" exhibited significant associations with cHL in the European population. Conversely, we assessed the "European antibody signature of EBV‐positive cHL" identified in our prior study which consisted of 18 EBV antibodies (2 IgA, 16 IgG), in the East‐Asian population. A subset of these antibodies (15/18, 83.3%) maintained significant associations with cHL in the East‐Asian population. This cross‐comparison of antibody signatures underscores the robust generalizability of EBV antibodies across populations. Five anti‐EBV IgG antibodies (LMP‐1, TK, BALF2, BDLF3, and BBLF1), found in both population‐specific antibody signatures, represent a "core signature of EBV‐positive cHL." Our findings suggest that the antibody responses targeting these core EBV proteins reflect a specific EBV gene expression pattern, serving as potential biomarkers for EBV‐positive cHL independent of population‐specific factors. [ABSTRACT FROM AUTHOR]

Nasopharyngeal carcinoma (NPC) risk prediction models based on Epstein–Barr virus (EBV)‐antibody testing have shown potential for screening of NPC; however, the long‐term stability is unclear. Here, we investigated the kinetics of two EBV‐antibody NPC risk scores within the Taiwan NPC Multiplex Family Study. Among 545 participants with multiple blood samples, we evaluated the stability of a 2‐marker enzyme‐linked immunosorbent assay score and 13‐marker multiplex serology score using the intra‐class correlation coefficient (ICC) by fitting a linear mixed model that accounted for the clustering effect of multiple measurements per subject and age. We also estimated the clustering of positive tests using Fleiss's kappa statistic. Over an average 20‐year follow‐up, the 2‐marker score showed high stability over time, whereas the 13‐marker score was more variable (p <.05). Case–control status is associated with the kinetics of the antibody response, with higher ICCs among cases. Positive tests were more likely to cluster within the same individual for the 2‐marker score than the 13‐marker score (p <.05). The 2‐marker score had an increase in specificity from ~90% for single measurement to ~96% with repeat testing. The 13‐marker score had a specificity of ~73% for a single measurement that increased to ~92% with repeat testing. Among individuals who developed NPC, none experienced score reversion. Our findings suggest that repeated testing could improve the specificity of NPC screening in high‐risk NPC multiplex families. Further studies are required to determine the impact on sensitivity, establish optimal screening intervals, and generalize these findings to general population settings in high‐risk regions. [ABSTRACT FROM AUTHOR]

Current influenza vaccines are strain-specific and require frequent updates to combat new strains, making a broadly protective influenza vaccine (BPIV) highly desirable. A promising strategy is to induce T-cell responses against internal proteins conserved across influenza strains. In this study, pH1N1 pre-exposed pigs were immunized by aerosol using viral vectored vaccines (ChAdOx2 and MVA) expressing matrix (M1) and nucleoprotein (NP). Following H3N2 challenge, all immunizations (M1, NP or NPM1) reduced lung pathology, but M1 alone offered the greatest protection. NP or NPM1 immunization induced both T-cell and antibody responses. M1 immunization generated no detectable antibodies but elicited M1-specific T-cell responses, suggesting T cell-mediated protection. Additionally, a single aerosol immunization with the ChAdOx vaccine encoding M1, NP and neuraminidase reduced lung pathology. These findings provide insights into BPIV development using a relevant large natural host, the pig. [ABSTRACT FROM AUTHOR]

Background: Endemic to Central Africa, loiasis, caused by the vector-borne worm Loa loa, affects approximately 10 million individuals. Clinical manifestations include transient angioedema (Calabar swellings), migration of the adult worm under the eye conjunctiva (eye worm) and less specific general symptoms. Loiasis presents a significant public health challenge because L. loa-infected individuals can develop serious adverse events after taking ivermectin, the drug used to combat onchocerciasis. In this context, alternative interventions and rigorous diagnostic approaches are needed. Diagnosing loiasis is challenging because its main clinical manifestations are sporadic and non-specific. The definitive diagnosis relies on identifying adult worms migrating beneath the conjunctiva, or microfilariae (pre-larvae) in blood smears. However, "occult loiasis" (infection without blood microfilariae) is frequent. Serological rapid antibody diagnostic tests (ARTs) can provide an alternative diagnostic method. We compared a novel ART simultaneously targeting onchocerciasis (IgG4 to Ov-16 and OvOC3261, test line 1) and loiasis (IgG4 to L1-SXP-1, test line 2), called IgG4-SXP-1 biplex test) to the already established Loa-ART (all IgG isotypes to Ll-SXP-1, called pan-IgG-SXP-1 test). Methodology: Blood samples underwent both ARTs, read qualitatively and semi-quantitatively. Additionally, blood smears, skin snips, Kato-Katz method for soil-transmitted helminthiases identification and eosinophilia measurements were performed. Questionnaires gathered demographic details and loiasis-related signs. ARTs performance was compared using specific loiasis-related signs and microfilaremia as references. Discordances between the two ARTs were investigated using logistic regression models. Principal findings: Out of 971 participants, 35.4% had L. loa microfilaremia, 71.9% had already experienced loiasis-related signs, 85.1% were positive in the pan-IgG-SXP-1 test and 79.4% were positive in the IgG4-SXP-1 biplex test. In the microfilariae-positive population, the sensitivity of the rapid tests was 87.4% for the pan-IgG-SXP-1 test and 88.6% for the prototype IgG4-SXP-1 biplex test. Sensitivity was similar for both ARTs when using eye worm or Calabar swelling as references, but diagnostic performance varied based on microfilaremia levels and occult loiasis. Overall, IgG4-SXP-1 biplex test demonstrated a sensitivity of 84.1% and specificity of 47.6% for loiasis compared to the pan-IgG-SXP-1 test, leading to a Kappa coefficient estimated at 0.27 ± 0.03 for the qualitative results of the 2 ARTs. In the group that tested positive with the Pan-IgG test but negative with the IgG4-specific test, there was a lower prevalence of STH infection (p = 0.008) and elevated eosinophilia (p<0.001) compared to the general tested population. Conclusion/Significance: The sensitivity of each test was good (84–85%) but the diagnostic agreement between the two ARTs was poor, suggesting that IgG and IgG4 antibody responses should be interpreted differently. The assessment of the innovative rapid diagnostic IgG4-SXP-1 biplex test, designed for onchocerciasis and loiasis, shows encouraging sensitivity but underlines the necessity for further in vitro assessment. Author summary: Loiasis, a disease caused by the parasite Loa loa impacting approximately 10 million people in Central Africa, causes transient angioedemas called Calabar swellings and eye worm episodes. Treatment is challenging, particularly in regions where onchocerciasis, another type of filariasis, is also prevalent. We tested a new kind of test that can detect both diseases at once and compared its performance with a previously available test for loiasis. We took blood samples from 971 people living in an area of Congo where loiasis is endemic. Out of the participants, 35.4% had L. loa pre-larvae in the blood–known as microfilariae, and 72.0% had experienced loiasis-related signs. The new test demonstrated promise in detecting the disease, albeit with some likelihood of false positives. Additionally, its performance varied according to the density of microfilariae in the blood. While the results exceeded expectations, further testing is essential to ensure its reliability. If validated, this test could prove instrumental in diagnosing both loiasis and onchocerciasis, offering a valuable tool for public health interventions in affected regions. [ABSTRACT FROM AUTHOR]

B cells play a key role in humoral immune responses by producing antibodies. Although there are numerous research on memory B cells definition markers and cytokines on B cell development, different studies have yielded contradictory conclusions due to species studied, the different cells and stimulating agents used. In the current study, we conducted a detailed characterization of B cells in human CBMCs, PBMCs and tonsil, including expression of Igs, activation and memory markers. Furthermore, we found that considerable amounts of IgA and IgG were expressed by CD27− B cells. These "Atypical" memory B cells corresponded to approximately 50% of IgG+ and IgA+B cells in blood, this proportion even reached 90% in tonsil. In addition, we investigated the effect of IL-21 and TGF-β1 on the membrane-bound form and secreted form of Igs using PBMCs and purified blood B cells. There were actual differences between the effect of cytokines on Igs secretion and surface expression. Our study will be helpful to advance the knowledge and understanding of humoral memory. [ABSTRACT FROM AUTHOR]

Residents in nursing homes face heightened COVID-19 risks. We aimed to assess the adverse events (AEs) rates and antibody responses after the first to the fifth dose of COVID-19 mRNA vaccination in a nursing home cohort. Ninety-five SARS-CoV-2 naïve participants consisted of 26 staff (median age, 51 years) and 69 residents (median age, 88 years). Life-threatening AEs were reported in neither residents nor staff. The severity of non-life-threatening AEs was graded, and severe AEs were reported only in staff. The AEs rates were considerably lower in residents, compared to those in staff. Anti-RBD IgG and the neutralizing titers (NTs) against Wuhan and Omicron BA.4/BA.5 did not differ significantly between those with 'any AE' and 'no AE' among both staff and residents two months after the second, third and fifth doses, while the anti-RBD IgG significantly differed between two groups after third dose in residents. These findings suggest that the anti-RBD IgG and the NTs increase regardless of the occurrence of AEs. Our study underscores a robust antibody response in both in staff and residents, and fewer AEs following COVID-19 vaccination in SARS-CoV-2 naïve residents than staff, supporting the recommendation for mRNA booster doses in older adults at high-risk care facilities. [ABSTRACT FROM AUTHOR]

In canine leishmaniosis endemic areas, Leishmania infantum may occur in sympatry with the non-pathogenic Leishmania tarentolae, which is associated to reptiles. The potential infectivity of L. tarentolae for mammals raises questions about the interactions between the two Leishmania species, and the potential cross-immune protection in dogs. This study aimed to assess the outcome of experimental L. tarentolae infection in dogs, determining: i) the anti-L. tarentolae antibody production, ii) the duration of the immunity and cytokine expression, and iii) the possible pathogenic effect in the canine host. Twelve purpose-bred beagle dogs were randomly allocated to three groups (intravenous inoculation, G1; intradermal inoculation, G2; negative control, G3). G1 and G2 dogs were inoculated twice (day 0, day 28) with 108 promastigotes of L. tarentolae strain (RTAR/IT/21/RI-325) isolated from a Tarentola mauritanica gecko. The animals were followed until day 206. Blood, serum, conjunctival swabs and lymph node aspirate samples were collected monthly and bone marrow, liver and spleen biopsies on day 91. Hematological and biochemical parameters were assessed monthly, as well as serology (IFAT and ELISA) and molecular identification of L. tarentolae. Mononuclear cells (PBMC) were obtained to assess the cytokine expression through in vitro stimulation or (re-) infection. Data from this study demonstrated that DNA from L. tarentolae is detectable up to 3 months post-infection, with seroconversion after day 28. Moreover, the non-pathogenic nature of L. tarentolae was confirmed, with a neutral Th1/Th2 polarization, and a possible shift to Th1 phenotype after derived macrophages (re-) infection, as demonstrated by the expression of IFN-gamma. Therefore, L. tarentolae demonstrated a great potential as a surrogate pathogen and/or immune-prophylaxis/immune-therapy against Leishmania infections in dogs and humans. Author summary: The reptilian-associated Leishmania tarentolae may be infective for mammals, which raises questions about a potential cross-immune protection towards Leishmania infantum in dogs. This study aimed to assess the outcome of experimental L. tarentolae infection in the canine host. Twelve purpose-bred beagle dogs were allocated into three groups (intravenous inoculation, G1; intradermal inoculation, G2; negative control, G3). The first two groups were inoculated twice (day 0, day 28) with 108 promastigotes of L. tarentolae, and were followed until day 206. Hematological and biochemical parameters were assessed, as well as serology (IFAT and ELISA), molecular identification and cytokine expression. Results demonstrated that DNA from L. tarentolae is detectable up to 3 months post-infection, with seroconversion after day 28. Moreover, the non-pathogenic nature of L. tarentolae was confirmed, with a neutral Th1/Th2 polarization, and a possible shift to Th1 phenotype (i.e., expression of IFN-gamma). These results suggest that L. tarentolae could be a potential candidate for developing immune strategies, opening new avenues for the prevention of the canine leishmaniasis. [ABSTRACT FROM AUTHOR]

The antibody response to vaccination and infection is a key component of the immune response to pathogens. Sequencing of peripheral B cells may not represent the complete B cell receptor repertoire. Here we present a method for sequencing human plasma-derived polyclonal IgG using a combination of mass spectrometry and B-cell sequencing. We investigate the IgG response to the Moderna Spikevax COVID-19 vaccine. From the sequencing data of the natural polyclonal response to vaccination, we generate 12 recombinant antibodies. Six derived recombinant antibodies, including four generated with de novo protein sequencing, exhibit similar or higher binding affinities than the original natural polyclonal antibody. Neutralization tests reveal that the six antibodies possess neutralizing capabilities against the target antigen. This research provides insights into sequencing polyclonal IgG antibodies and the potential of our approach in generating recombinant antibodies with robust binding affinity and neutralization capabilities. Directly examining the circulating IgG pool is crucial due to potential misrepresentations by B-cell analysis alone. The antibody response to infection and vaccination is an essential component of the anti-infective immune response. Here the authors present a de novo protein sequencing method for antibody discovery from polyclonal IgG from human plasma and characterise the antibody response to the Moderna Spikevax COVID-19 vaccine. [ABSTRACT FROM AUTHOR]

Despite decades of antibody research, it remains challenging to predict the specificity of an antibody solely based on its sequence. Two major obstacles are the lack of appropriate models and the inaccessibility of datasets for model training. In this study, we curated >5,000 influenza hemagglutinin (HA) antibodies by mining research publications and patents, which revealed many distinct sequence features between antibodies to HA head and stem domains. We then leveraged this dataset to develop a lightweight memory B cell language model (mBLM) for sequence-based antibody specificity prediction. Model explainability analysis showed that mBLM could identify key sequence features of HA stem antibodies. Additionally, by applying mBLM to HA antibodies with unknown epitopes, we discovered and experimentally validated many HA stem antibodies. Overall, this study not only advances our molecular understanding of the antibody response to the influenza virus but also provides a valuable resource for applying deep learning to antibody research. • Assembled a dataset of 5,561 published antibodies to influenza HA from 132 donors • Antibodies to HA head and stem domains have distinct convergent sequence features • Developed a lightweight language model (mBLM) for antibody specificity prediction • Discovered HA stem antibodies and key somatic hypermutations using mBLM Predicting antibody specificity based solely on sequence has remained an obstacle in humoral research. Leveraging a curated dataset of >5,000 influenza hemagglutinin (HA) antibodies, Wang et al. develop a lightweight memory B cell language model for antibody specificity prediction. This model identifies unique HA stem antibodies and key antibody sequence features. [ABSTRACT FROM AUTHOR]

BACKGROUND: Serum sickness is an immune complex-mediated type III hypersensitivity caused by the presence of a heterologous or chimeric protein leading to antibody formation and subsequent immune complexes. Patients typically present 1 to 2 weeks after exposure to the offending agent with fever, fatigue, and arthralgias accompanied by a pruritic rash. Postmarketing case reports have detailed serum sickness in response to rituximab, a chimeric mouse/human anti-CD20 monoclonal antibody for the treatment of hematologic malignancies, such as non-Hodgkin lymphomas, as well as nonmalignant disease states. DISCUSSION: We present the case of a 68-year-old man with follicular lymphoma who received the biosimilar rituximab-arrx (Riabni) and bendamustine. Eleven days after treatment, the patient had serum sickness syndrome in response to receiving rituximab-arrx, but he tolerated subsequent therapy with obinutuzumab, a humanized anti-CD20 monoclonal antibody. Scant literature supported treatment with rituximab-arrx rechallenge, and few case reports supported substitution with obinutuzumab. Fully humanized monoclonal antibodies are less immunogenic and therefore have a lower risk for immune complex formation than the chimeric rituximab-based monoclonals. Rituximab also has higher complement-dependent cytotoxicity than obinutuzumab, which influences the mechanism of type III hypersensitivity reactions. For these reasons, obinutuzumab has an overall lower risk for serum sickness and was tolerated after the previous presence of serum sickness in this case. CONCLUSION: Our patient tolerated 5 full cycles of obinutuzumab without the recurrence of serum sickness, despite having a reaction to a rituximab biosimilar. This case adds to the limited literature supporting the transition from rituximab-based drugs to obinutuzumab when type III hypersensitivity reactions are encountered. [ABSTRACT FROM AUTHOR]

Background: Omicron variants have rapidly diversified into sublineages with mutations that enhance immune evasion, posing challenges for vaccination and antibody responses. This study aimed to compare serum cross‐neutralizing antibody responses against various SARS‐CoV‐2 Omicron sublineages (BA.1, BA.5, XBB.1.17.1, FK.1.1, and JN.1) in recipients of monovalent COVID‐19 boosters, bivalent booster recipients, and individuals who had recovered from Omicron BA.5 infections. Methods: We conducted a micro‐neutralization assay on serum samples from monovalent BNT162b2 booster recipients (N = 54), bivalent BNT162b2 booster recipients (N = 24), and SARS‐CoV‐2 Omicron BA.5‐recovered individuals (N = 13). The history of SARS‐CoV‐2 Omicron infection was assessed using ELISA against the SARS‐CoV‐2 NP protein. Results: Bivalent booster recipients exhibited significantly enhanced neutralization efficacy against Omicron sublineages compared to those who had received monovalent booster vaccinations. Omicron BA.5‐recovered individuals displayed similar neutralizing antibodies (NAbs) to the bivalent booster recipients. Despite the improved neutralization in bivalent recipients and BA.5‐recovered individuals, there were limitations in neutralization against the recently emerged Omicron subvariants: XBB.1.17.1 FK.1.1, and JN.1. In both monovalent and bivalent booster recipients, a history of Omicron breakthrough infection was associated with relatively higher geometric mean titers of NAbs against Omicron BA.1, BA.5, and XBB.1.17.1 variants. Conclusion: This study underscores the intricate interplay between vaccination strategies, immune imprinting, and the dynamic landscape of SARS‐CoV‐2 variants. Although bivalent boosters enhance neutralization, addressing the challenge of emerging sublineages like XBB.1.17.1, FK.1.1, and JN.1 may necessitate the development of tailored vaccines, underscoring the need for ongoing adaptation to effectively combat this highly mutable virus. [ABSTRACT FROM AUTHOR]

Recurrent pregnancy loss (RPL), defined as two or more pregnancy losses before the 24th week of gestation, affects 1%–3% of women worldwide. Approximately, 40% of RPL cases are secondary RPL (sRPL), where women have given birth before facing pregnancy losses. The underlying causes of RPL remain unclear, but immune‐related factors may play a role. Previously, a randomised controlled trial using immunoglobulin (IVIG) in sRPL women with a history of four pregnancy losses performed in our RPL unit did not show significant effects of IVIG treatment overall. Yet, some evidence suggests potential benefits for a subset of sRPL patients. In the cohort used for the randomised controlled trial, we examined the role of maternal HLA class II‐presented fetal HLA‐derived epitopes in sRPL using the predicted indirectly recognisable HLA epitopes (PIRCHE‐II) algorithm. In the placebo group, sRPL mothers with an anti‐HLA antibody response had higher PIRCHE‐II scores when having a live birth compared with sRPL women who experienced another pregnancy loss. This difference was not observed in the IVIG‐treated group. Furthermore, as a proxy for T‐cell memory, the number of overlapping peptides between the two paternal haplotypes in couples having live births without treatment displayed a larger number of overlapping peptides. This effect was primarily driven by class II‐derived peptides. These results suggest that specific combinations of sRPL mothers and fathers, particularly those with an anti‐HLA antibody response, may generate higher PIRCHE‐II scores, which could contribute to successful live births. Understanding these immune interactions may provide insights for personalised diagnostic and therapeutic strategies in sRPL. [ABSTRACT FROM AUTHOR]