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BackgroundDuring the last decade Ebola virus has caused several outbreaks in Africa. The recombinant vesicular stomatitis virus-vectored Zaire Ebola (rVSVΔG-ZEBOV-GP) vaccine has proved safe and immunogenic but is reactogenic. We previously identified the first innate plasma signature response after vaccination in Geneva as composed of five monocyte-related biomarkers peaking at day 1 post-immunization that correlates with adverse events, biological outcomes (haematological changes and viremia) and antibody titers. In this follow-up study, we sought to identify additional biomarkers in the same Geneva cohort and validate those identified markers in a US cohort.MethodsAdditional biomarkers were identified using multiplexed protein biomarker platform O-link and confirmed by Luminex. Principal component analysis (PCA) evaluated if these markers could explain a higher variability of the vaccine response (and thereby refined the initial signature). Multivariable and linear regression models evaluated the correlations of the main components with adverse events, biological outcomes, and antibody titers. External validation of the refined signature was conducted in a second cohort of US vaccinees (n=142).ResultsEleven additional biomarkers peaked at day 1 post-immunization: MCP2, MCP3, MCP4, CXCL10, OSM, CX3CL1, MCSF, CXCL11, TRAIL, RANKL and IL15. PCA analysis retained three principal components (PC) that accounted for 79% of the vaccine response variability. PC1 and PC2 were very robust and had different biomarkers that contributed to their variability. PC1 better discriminated different doses, better defined the risk of fever and myalgia, while PC2 better defined the risk of headache. We also found new biomarkers that correlated with reactogenicity, including transient arthritis (MCP-2, CXCL10, CXCL11, CX3CL1, MCSF, IL-15, OSM). Several innate biomarkers are associated with antibody levels one and six months after vaccination. Refined PC1 correlated strongly in both data sets (Geneva: r = 0.97, P < 0.001; US: r = 0.99, P< 0.001).ConclusionEleven additional biomarkers refined the previously found 5-biomarker Geneva signature. The refined signature better discriminated between different doses, was strongly associated with the risk of adverse events and with antibody responses and was validated in a separate cohort.

Summary: The vectored Ebola vaccine rVSVΔG-ZEBOV-GP elicits protection against Ebola Virus Disease (EVD). In a study of forty-eight healthy adult volunteers who received either the rVSVΔG-ZEBOV-GP vaccine or placebo, we profiled intracellular microRNAs (miRNAs) from whole blood cells (WB) and circulating miRNAs from serum-derived extracellular vesicles (EV) at baseline and longitudinally following vaccination. Further, we identified early miRNA signatures associated with ZEBOV-specific IgG antibody responses at baseline and up to one year post-vaccination, and pinpointed target mRNA transcripts and pathways correlated to miRNAs whose expression was altered after vaccination by using systems biology approaches.Several miRNAs were differentially expressed (DE) and miRNA signatures predicted high or low IgG ZEBOV-specific antibody levels with high classification performance. The top miRNA discriminators were WB-miR-6810, EV-miR-7151-3p, and EV-miR-4426. An eight-miRNA antibody predictive signature was associated with immune-related target mRNAs and pathways.These findings provide valuable insights into early blood biomarkers associated with rVSVΔG-ZEBOV-GP vaccine-induced IgG antibody responses.

IntroductionThe rVSVDG-ZEBOV-GP (Ervebo®) vaccine is both immunogenic and protective against Ebola. However, the vaccine can cause a broad range of transient adverse reactions, from headache to arthritis. Identifying baseline reactogenicity signatures can advance personalized vaccinology and increase our understanding of the molecular factors associated with such adverse events.MethodsIn this study, we developed a machine learning approach to integrate prevaccination gene expression data with adverse events that occurred within 14 days post-vaccination.Results and DiscussionWe analyzed the expression of 144 genes across 343 blood samples collected from participants of 4 phase I clinical trial cohorts: Switzerland, USA, Gabon, and Kenya. Our machine learning approach revealed 22 key genes associated with adverse events such as local reactions, fatigue, headache, myalgia, fever, chills, arthralgia, nausea, and arthritis, providing insights into potential biological mechanisms linked to vaccine reactogenicity.

Circadian rhythms have been shown to influence immune responses, but it is unclear whether this influences responses to vaccines. Here the authors show that dendritic cells migrate in a circadian rhythm meaning that interactions with T cells are altered leading to differential vaccine responses.

Emerging SARS-CoV-2 variants raise concerns on protective immunity. Here the authors show that convalescent sera from people infected with Alpha, Beta, Gamma or Delta show a significant drop of Omicron-BA.1 neutralization and that vaccine-breakthrough infections with Omicron-BA.1 or Delta result in robust neutralization for both Delta and Omicron-BA.1.

IntroductionC-type lectin receptor (CLR) agonists emerged as superior inducers of primary B cell responses in early life compared with Toll-like receptor (TLR) agonists, while both types of adjuvants are potent in adults.MethodsHere, we explored the mechanisms accounting for the differences in neonatal adjuvanticity between a CLR-based (CAF®01) and a TLR4-based (GLA-SE) adjuvant administered with influenza hemagglutinin (HA) in neonatal mice, by using transcriptomics and systems biology analyses.ResultsOn day 7 after immunization, HA/CAF01 increased IL6 and IL21 levels in the draining lymph nodes, while HA/GLA-SE increased IL10. CAF01 induced mixed Th1/Th17 neonatal responses while T cell responses induced by GLA-SE had a more pronounced Th2-profile. Only CAF01 induced T follicular helper (Tfh) cells expressing high levels of IL21 similar to levels induced in adult mice, which is essential for germinal center (GC) formation. Accordingly, only CAF01- induced neonatal Tfh cells activated adoptively transferred hen egg lysozyme (HEL)-specific B cells to form HEL+ GC B cells in neonatal mice upon vaccination with HEL-OVA.DiscussionCollectively, the data show that CLR-based adjuvants are promising neonatal and infant adjuvants due to their ability to harness Tfh responses in early life.

ObjectivesTo comprehensively analyze the quality of the antibody response between children with Multisystem inflammatory syndrome (MIS-C) and age-matched controls at one month after SARS-CoV-2 exposure, and infected in the same time-period.MethodsSerum from 20 MIS-C children at admission, and 14 control children were analyzed. Antigen specific antibody isotypes and subclasses directed against various antigens of SARS-CoV-2 as well as against human common coronavirus (HCoVs) and commensal or pathogenic microorganisms were assessed by a bead-based multiplexed serological assay and by ELISA. The functionality of these antibodies was also assessed using a plaque reduction neutralization test, a RBD-specific avidity assay, a complement deposition assay and an antibody-dependent neutrophil phagocytosis (ADNP) assay.ResultsChildren with MIS-C developed a stronger IgA antibody response in comparison to children with uncomplicated COVID-19, while IgG and IgM responses are largely similar in both groups. We found a typical class-switched antibody profile with high level of IgG and IgA titers and a measurable low IgM due to relatively recent SARS-CoV-2 infection (one month). SARS-CoV-2-specific IgG antibodies of MIS-C children had higher functional properties (higher neutralization activity, avidity and complement binding) as compared to children with uncomplicated COVID-19. There was no difference in the response to common endemic coronaviruses between both groups. However, MIS-C children had a moderate increase against mucosal commensal and pathogenic strains, reflecting a potential association between a disruption of the mucosal barrier with the disease.ConclusionEven if it is still unclear why some children develop a MIS-C, we show here that MIS-C children produce higher titers of IgA antibodies, and IgG antibodies with higher functionality, which could reflect the local gastro-intestinal mucosal inflammation potentially induced by a sustained SARS-CoV-2 gut infection leading to continuous release of SARS-CoV-2 antigens.

Summary: Background: A recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP) vaccine has been reported as safe, immunogenic, and highly protective in a ring vaccination trial. We aimed to identify transcriptomic immune response biomarker signatures induced by vaccination and associated signatures with its immunogenicity and reactogenicity to better understand the potential mechanisms of action of the vaccine. Methods: 354 healthy adult volunteers were vaccinated in randomised, double-blind, placebo-controlled trials in Europe (Geneva, Switzerland [November, 2014, to January, 2015]) and North America (USA [Dec 5, 2014, to June 23, 2015]), and dose-escalation trials in Africa (Lambaréné, Gabon [November, 2014, to January, 2015], and Kilifi, Kenya [December, 2014, to January, 2015]) using different doses of the recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP; 3 × 105 to 1 × 108 plaque-forming units [pfu]). Longitudinal transcriptomic responses (days 0, 1, 2, 3, 7, 14, and 28) were measured in whole blood using a targeted gene expression profiling platform (dual-colour reverse-transcriptase multiplex ligation-dependent probe amplification) focusing on 144 immune-related genes. The effect of time and dose on transcriptomic response was also assessed. Logistic regression with lasso regularisation was applied to identify host signatures with optimal discriminatory capability of vaccination at day 1 or day 7 versus baseline, whereas random-effects models and recursive feature elimination combined with regularised logistic regression were used to associate signatures with immunogenicity and reactogenicity. Findings: Our results indicated that perturbation of gene expression peaked on day 1 and returned to baseline levels between day 7 and day 28. The magnitude of the response was dose-dependent, with vaccinees receiving a high dose (≥9 × 106 pfu) of rVSVΔG-ZEBOV-GP exhibiting the largest amplitude. The most differentially expressed genes that were significantly upregulated following vaccination consisted of type I and II interferon-related genes and myeloid cell-associated markers, whereas T cell, natural killer cell, and cytotoxicity-associated genes were downregulated. A gene signature associated with immunogenicity (common to all four cohorts) was identified correlating gene expression profiles with ZEBOV-GP antibody titres and a gene signatures associated with reactogenicity (Geneva cohort) was identified correlating gene expression profiles with an adverse event (ie, arthritis). Interpretation: Collectively, our results identify and cross-validate immune-related transcriptomic signatures induced by rVSVΔG-ZEBOV-GP vaccination in four cohorts of adult participants from different genetic and geographical backgrounds. These signatures will aid in the rational development, testing, and evaluation of novel vaccines and will allow evaluation of the effect of host factors such as age, co-infection, and comorbidity on responses to vaccines. Funding: Innovative Medicines Initiative 2 Joint Undertaking.

ObjectiveTo comprehensively evaluate SARS-CoV-2 specific B-cell and antibody responses up to one year after mild COVID-19.MethodsIn 31 mildly symptomatic COVID-19 participants SARS-CoV-2-specific plasmablasts and antigen-specific memory B cells were measured by ELISpot. Binding antibodies directed against the proteins spike (S), domain S1, and nucleocapsid (N) were estimated using rIFA, ELISA, and commercially available assays, and avidity measured using thiocyanate washout. Neutralizing antibodies against variants of concern were measured using a surrogate-neutralization test.ResultsPlasmablast responses were assessed in all participants who gave sequential samples during the first two weeks after infection; they preceded the rise in antibodies and correlated with antibody titers measured at one month. S1 and N protein-specific IgG memory B-cell responses remained stable during the first year, whereas S1-specific IgA memory B-cell responses declined after 6 months. Antibody titers waned over time, whilst potent affinity maturation was observed for anti-RBD antibodies. Neutralizing antibodies against wild-type (WT) and variants decayed during the first 6 months but titers significantly increased for Alpha, Gamma and Delta between 6 months and one year. Therefore, near-similar titers were observed for WT and Alpha after one year, and only slightly lower antibody levels for the Delta variant compared to WT. Anti-RBD antibody responses correlated with the neutralizing antibody titers at all time points, however the predicted titers were 3-fold lower at one year compared to one month.ConclusionIn mild COVID-19, stable levels of SARS-CoV-2 specific memory B cells and antibodies neutralizing current variants of concern are observed up to one year post infection. Care should be taken when predicting neutralizing titers using commercial assays that measure binding antibodies.

Summary: SARS-CoV-2 infection in children is less severe than it is in adults. We perform a longitudinal analysis of the early innate responses in children and adults with mild infection within household clusters. Children display fewer symptoms than adults do, despite similar initial viral load, and mount a robust anti-viral immune signature typical of the SARS-CoV-2 infection and characterized by early interferon gene responses; increases in cytokines, such as CXCL10 and GM-CSF; and changes in blood cell numbers. When compared with adults, the antiviral response resolves faster (within a week of symptoms), monocytes and dendritic cells are more transiently activated, and genes associated with B cell activation appear earlier in children. Nonetheless, these differences do not have major effects on the quality of SARS-CoV-2-specific antibody responses. Our findings reveal that better early control of inflammation as observed in children may be key for rapidly controlling infection and limiting the disease course.

Introduction: The live-attenuated recombinant vesicular stomatitis virus vaccine expressing the glycoprotein (GP) of Zaire Ebola virus (rVSV-ZEBOV) has proven immunogenic in humans and effective in field studies. Yet long-term durability of vaccine responses is unknown. Areas covered: We survey the evidence available in the literature for the durability of human responses to rVSV-ZEBOV. We also review determinants of initial responses and of their persistence. Expert commentary: Persistence of EBOV-GP-specific antibody responses is strong at 2 years – currently the longest post-vaccination interval studied – after a single injection. Vaccine dose predicts persistence of seropositivity, though the magnitude of antibody responses at later time points becomes less dose-dependent. Vaccine-related arthritis is a significant predictor of both persistence and magnitude of the antibody response.

ABSTRACT Viral shedding patterns and their correlations with immune responses are still poorly characterized in mild coronavirus (CoV) disease 2019 (COVID-19). We monitored shedding of viral RNA and infectious virus and characterized the immune response kinetics of the first five patients quarantined in Geneva, Switzerland. High viral loads and infectious virus shedding were observed from the respiratory tract despite mild symptoms, with isolation of infectious virus and prolonged positivity by reverse transcriptase PCR (RT-PCR) until days 7 and 19 after symptom onset, respectively. Robust innate responses characterized by increases in activated CD14+ CD16+ monocytes and cytokine responses were observed as early as 2 days after symptom onset. Cellular and humoral severe acute respiratory syndrome (SARS)-CoV-2-specific adaptive responses were detectable in all patients. Infectious virus shedding was limited to the first week after symptom onset. A strong innate response, characterized by mobilization of activated monocytes during the first days of infection and SARS-CoV-2-specific antibodies, was detectable even in patients with mild disease. IMPORTANCE This work is particularly important because it simultaneously assessed the virology, immunology, and clinical presentation of the same subjects, whereas other studies assess these separately. We describe the detailed viral and immune profiles of the first five patients infected by SARS-CoV-2 and quarantined in Geneva, Switzerland. Viral loads peaked at the very beginning of the disease, and infectious virus was shed only during the early acute phase of disease. No infectious virus could be isolated by culture 7 days after onset of symptoms, while viral RNA was still detectable for a prolonged period. Importantly, we saw that all patients, even those with mild symptoms, mount an innate response sufficient for viral control (characterized by early activated cytokines and monocyte responses) and develop specific immunity as well as cellular and humoral SARS-CoV-2-specific adaptive responses, which already begin to decline a few months after the resolution of symptoms.

Novel adjuvants, such as Toll-like receptors (TLRs) agonists, are needed for the development of new formulations able to circumvent limitations of current vaccines. Among TLRs, TLR7/8 agonists represent promising candidates, as they are well described to enhance antigen-specific antibody responses and skew immunity toward T helper (TH) 1 responses. We find here that the incorporation of the synthetic TLR7/8 ligand 3M-052 in a cationic DOEPC-based liposome formulation shifts immunity toward TH1 responses and elicits strong and long-lasting germinal center and follicular T helper cell responses in adult mice. This reflects the prolonged recruitment of innate cells toward the site of immunization and homing of activated antigen-loaded monocytes and monocyte-derived dendritic cells toward draining lymph nodes. We further show that this adjuvanticity is independent of type I IFN but NF-κB-dependent. Overall, our data identify TLR7/8 agonists incorporated in liposomes as promising and effective adjuvants to enhance TH1 and germinal center responses.

Predicting vaccine efficacy remains a challenge. We used a systems vaccinology approach to identify early innate immune correlates of antibody induction in humans receiving the Ebola vaccine rVSV-ZEBOV. Blood samples from days 0, 1, 3, 7, and 14 were analyzed for changes in cytokine levels, innate immune cell subsets, and gene expression. Integrative statistical analyses with cross-validation identified a signature of 5 early innate markers correlating with antibody titers on day 28 and beyond. Among those, IP-10 on day 3 and MFI of CXCR6 on NK cells on day 1 were independent correlates. Consistently, we found an early gene expression signature linked to IP-10. This comprehensive characterization of early innate immune responses to the rVSV-ZEBOV vaccine in humans revealed immune signatures linked to IP-10. These results suggest correlates of vaccine-induced antibody induction and provide a rationale to explore strategies for augmenting the effectiveness of vaccines through manipulation of IP-10.

Background: The recent West African Ebola epidemic led to accelerated efforts to test Ebola vaccine candidates. As part of the World Health Organisation-led VSV Ebola Consortium (VEBCON), we performed a phase I clinical trial investigating rVSV-ZEBOV (a recombinant vesicular stomatitis virus-vectored Ebola vaccine), which has recently demonstrated protection from Ebola virus disease (EVD) in phase III clinical trials and is currently in advanced stages of licensing. So far, correlates of immune protection are incompletely understood and the role of cell-mediated immune responses has not been comprehensively investigated to date. Methods: We recruited 30 healthy subjects aged 18–55 into an open-label, dose-escalation phase I trial testing three doses of rVSV-ZEBOV (3 × 105 plaque-forming units (PFU), 3 × 106 PFU, 2 × 107 PFU) (ClinicalTrials.gov; NCT02283099). Main study objectives were safety and immunogenicity, while exploratory objectives included lymphocyte dynamics, cell-mediated immunity and cytokine networks, which were assessed using flow cytometry, ELISpot and LUMINEX assay. Findings: Immunization with rVSV-ZEBOV was well tolerated without serious vaccine-related adverse events. Ebola virus-specific neutralizing antibodies were induced in nearly all individuals. Additionally, vaccinees, particularly within the highest dose cohort, generated Ebola glycoprotein (GP)-specific T cells and initiated a cascade of signaling molecules following stimulation of peripheral blood mononuclear cells with Ebola GP peptides. Interpretation: In addition to a benign safety and robust humoral immunogenicity profile, subjects immunized with 2 × 107 PFU elicited higher cellular immune responses and stronger interlocked cytokine networks compared to lower dose groups. To our knowledge these data represent the first detailed cell-mediated immuneprofile of a clinical trial testing rVSV-ZEBOV, which is of particular interest in light of its potential upcoming licensure as the first Ebola vaccine. VEBCON trial Hamburg, Germany (NCT02283099).

Background: An acellular Pertussis (aP) vaccine containing recombinant genetically detoxified Pertussis Toxin (PTgen), Filamentous Hemagglutinin (FHA) and Pertactin (PRN) has been developed by BioNet-Asia (BioNet). We present here the results of the first clinical study of this recombinant aP vaccine formulated alone or in combination with tetanus and diphtheria toxoids (TdaP). Methods: A phase I/II, observer-blind, randomized controlled trial was conducted at Mahidol University in Bangkok, Thailand in healthy adult volunteers aged 18–35 y. The eligible volunteers were randomized to receive one dose of either BioNet's aP or Tetanus toxoid-reduced Diphtheria toxoid-acellular Pertussis (TdaP) vaccine, or the Tdap Adacel® vaccine in a 1:1:1 ratio. Safety follow-up was performed for one month. Immunogenicity was assessed at baseline, at 7 and 28 d after vaccination. Anti-PT, anti-FHA, anti-PRN, anti-tetanus and anti-diphtheria IgG antibodies were assessed by ELISA. Anti-PT neutralizing antibodies were assessed also by CHO cell assay. Results: A total of 60 subjects (20 per each vaccine group) were enrolled and included in the safety analysis. Safety laboratory parameters, incidence of local and systemic post-immunization reactions during 7 d after vaccination and incidence of adverse events during one month after vaccination were similar in the 3 vaccine groups. One month after vaccination, seroresponse rates of anti-PT, anti-FHA and anti-PRN IgG antibodies exceeded 78% in all vaccine groups. The anti-PT IgG, anti-FHA IgG, and anti-PT neutralizing antibody geometric mean titers (GMTs) were significantly higher following immunization with BioNet's aP and BioNet's TdaP than Adacel® (P< 0.05). The anti-PRN IgG, anti-tetanus and anti-diphtheria GMTs at one month after immunization were comparable in all vaccine groups. All subjects had seroprotective titers of anti-tetanus and anti-diphtheria antibodies at baseline. Conclusion: In this first clinical study, PTgen-based BioNet's aP and TdaP vaccines showed a similar tolerability and safety profile to Adacel® and elicited significantly higher immune responses to PT and FHA.

Summary: Maternal antibodies (MatAbs) protect offspring from infections but limit their responses to vaccination. The mechanisms of this inhibition are still debated. Using murine early-life immunization models mimicking the condition prevailing in humans, we observed the induction of CD4-T, T follicular helper, and germinal center (GC) B cell responses even when early-life antibody responses were abrogated by MatAbs. GC B cells induced in the presence of MatAbs form GC structures and exhibit canonical GC changes in gene expression but fail to differentiate into plasma cells and/or memory B cells in a MatAb titer-dependent manner. Furthermore, GC B cells elicited in the presence or absence of MatAbs use different VH and Vk genes and show differences in genes associated with B cell differentiation and isotype switching. Thus, MatAbs do not prevent B cell activation but control the output of the GC reaction both quantitatively and qualitatively, shaping the antigen-specific B cell repertoire. : Maternal antibodies (MatAbs) protect offspring from infections but limit their vaccine responses through still poorly known mechanisms. Vono et al. report that MatAbs do not prevent B cell activation or germinal center formation but control plasma cell and memory B cell differentiation, shaping the long-term antigen-specific B cell repertoire. Keywords: immunization, maternal antibodies, neonates, repertoire, germinal centers, epitope masking

T follicular helper (Tfh) cells have emerged as a critical limiting factor for controlling the magnitude of neonatal germinal center (GC) reactions and primary vaccine antibody responses. We compared the functional attributes of neonatal and adult Tfh cells at the transcriptomic level and demonstrated that the Tfh cell program is well-initiated in neonates although the Tfh gene-expression pattern (i.e., CXCR5, IL-21, BCL6, TBK1, STAT4, ASCL2, and c-MAF) is largely underrepresented as compared to adult Tfh cells. Importantly, we identified a TH2-bias of neonatal Tfh cells, with preferential differentiation toward short-lived pre-Tfh effector cells. Remarkably, adjuvantation with CpG-ODNs redirect neonatal pre-Tfh cells toward committed GC-Tfh cells, as illustrated by increased expression of Tfh signature genes and reduced expression of TH2-related genes.

Dendritic cells (DCs) that drain the gut and skin are known to favor the establishment of T cell populations that home to the original site of DC-antigen (Ag) encounter by providing soluble “imprinting” signals to T cells in the lymph node (LN). To study the induction of lung T cell-trafficking, we used a protein-adjuvant murine intranasal and intramuscular immunization model to compare in vivo-activated Ag+ DCs in the lung and muscle-draining LNs. Higher frequencies of Ag+ CD11b+ DCs were observed in lung-draining mediastinal LNs (MedLN) compared to muscle-draining inguinal LNs (ILN). Ag+ CD11b+ MedLN DCs were qualitatively superior at priming CD4+ T cells, which then expressed CD49a and CXCR3, and preferentially trafficked into the lung parenchyma. CD11b+ DCs from the MedLN expressed higher levels of surface podoplanin, Trem4, GL7, and the known co-stimulatory molecules CD80, CD86, and CD24. Blockade of specific MedLN DC molecules or the use of sorted DC and T cell co-cultures demonstrated that DC surface phenotype influences the ability to prime T cells that then home to the lung. Thus, the density of dLN Ag+ DCs, and DC surface molecule signatures are factors that can influence the output and differentiation of lung-homing CD4+ T cells.

Pertussis is still observed in many countries despite of high vaccine coverage. Acellular pertussis (aP) vaccination is widely implemented in many countries as primary series in infants and as boosters in school-entry/adolescents/adults (including pregnant women in some). One novel strategy to improve the reactivation of aP-vaccine primed immunity could be to include genetically- detoxified pertussis toxin and novel adjuvants in aP vaccine boosters. Their preclinical evaluation is not straightforward, as it requires mimicking the human situation where T and B memory cells may persist longer than vaccine-induced circulating antibodies. Toward this objective, we developed a novel murine model including two consecutive adoptive transfers of the memory cells induced by priming and boosting, respectively. Using this model, we assessed the capacity of three novel aP vaccine candidates including genetically-detoxified pertussis toxin, pertactin, filamentous hemagglutinin, and fimbriae adsorbed to aluminum hydroxide, supplemented—or not—with Toll-Like-Receptor 4 or 9 agonists (TLR4A, TLR9A), to reactivate aP vaccine-induced immune memory and protection, reflected by bacterial clearance. In the conventional murine immunization model, TLR4A- and TLR9A-containing aP formulations induced similar aP-specific IgG antibody responses and protection against bacterial lung colonization as current aP vaccines, despite IL-5 down-modulation by both TLR4A and TLR9A and IL-17 up-modulation by TLR4A. In the absence of serum antibodies at time of boosting or exposure, TLR4A- and TLR9A-containing formulations both enhanced vaccine antibody recall compared to current aP formulations. Unexpectedly, however, protection was only increased by the TLR9A-containing vaccine, through both earlier bacterial control and accelerated clearance. This suggests that TLR9A-containing aP vaccines may better reactivate aP vaccine-primed pertussis memory and enhance protection than current or TLR4A-adjuvanted aP vaccines.

Ebolavirus Disease (EVD) is a severe haemorrhagic fever that occurs in epidemic outbreaks, with a high fatality rate and no specific therapies available. rVSVΔG-ZEBOV-GP (Ervebo®), a live-attenuated recombinant vesicular stomatitis virus vector expressing the glycoprotein G of Zaire Ebolavirus, is the first vaccine approved for prevention of EVD. Both innate and adaptive responses are deemed to be involved in vaccine-induced protection, yet the mechanisms are not fully elucidated. A global transcriptomic approach was used to profile the blood host-response in 51 healthy volunteers enrolled in a phase 1/2 clinical trial. Signatures of the host responses were investigated assessing the enrichment in differentially expressed genes (DEGs) of specific “blood transcription modules” (BTM). Comparison of gene-expression levels showed that vaccination produces a peak of 5469 DEGs at day one, representing 38.6% of the expressed genes. Out of 346 BTMs, 144 were significantly affected by vaccination. Innate immunity pathways were induced from day 1 to day 14. At days 2 and 3, neutrophil modules were downregulated and complement-related modules upregulated. T-cell and cell-cycle associated modules were upregulated at days 7 and 14, while at day 28, no modules remained activated. At day 14, a direct correlation was observed between ZEBOV glycoprotein-specific antibody titres and activation of seven BTMs, including two related to B-cell activation and B cell receptor signalling. Transcriptomic analysis identified an rVSVΔG-ZEBOV-GP-induced signature and demonstrated a direct correlation of blood transcriptomic changes with ZEBOV glycoprotein-specific antibody titres.

Abstract The International Consortium for Prevention and Infection Control (ICPIC) organises a biannual conference (ICPIC) on various subjects related to infection prevention, treatment and control. During ICPIC 2015, held in Geneva in June 2015, a full one-day session focused on the 2014–2015 Ebola virus disease (EVD) outbreak in West Africa. This article is a non-exhaustive compilation of these discussions. It concentrates on lessons learned and imagining a way forward for the communities most affected by the epidemic. The reader can access video recordings of all lectures delivered during this one-day session, as referenced. Topics include the timeline of the international response, linkages between the dynamics of the epidemic and infection prevention and control, the importance of community engagement, and updates on virology, diagnosis, treatment and vaccination issues. The paper also includes discussions from public health, infectious diseases, critical care and infection control experts who cared for patients with EVD in Africa, in Europe, and in the United Sates and were involved in Ebola preparedness in both high- and low-resource settings and countries. This review concludes that too little is known about the pathogenesis and treatment of EVD, therefore basic and applied research in this area are urgently required. Furthermore, it is clear that epidemic preparedness needs to improve globally, in particular through the strengthening of health systems at local and national levels. There is a strong need for culturally sensitive approaches to public health which could be designed and delivered by social scientists and medical professionals working together. As of December 2015, this epidemic killed more than 11,000 people and infected more than 28,000; it has also generated more than 17,000 survivors and orphans, many of whom face somatic and psychological complications. The continued treatment and rehabilitation of these people is a public health priority, which also requires an integration of specific medical and social science approaches, not always available in West Africa.

Lower respiratory tract infections (LRTI) are often caused by Streptococcus pneumoniae (Spn) and can be recurrent in 8% of children older than 2 years of age. Spn is recognized by pattern-recognition receptors (PRRs) of the innate immune system, in particular toll-like receptors (TLRs) 2 and 4. To assess whether a defect somewhere along this TLR signaling pathway increases susceptibility to recurrent pneumococcal LRTI, we conducted a prospective case–control study with 88 healthy individuals and 45 children with recurrent LRTI aged 2–5 years old. We examined cell surface expression of TLR2 and TLR4, as well as eight genetic variants of these receptors or associated co-receptors TLR1 and TLR6. Interleukin-6 production was measured after whole blood stimulation assays with specific agonists and heat-killed Spn. Our findings reveal that single-nucleotide polymorphisms within toll-interleukin 1 receptor domain-containing adaptor protein (TIRAP) alone or in combination with TLR1 N248S, TLR1 I602S, or TLR6 S249P polymorphisms contributes to various degree of susceptibility to recurrent pneumococcal LRTI in children by modulating the inflammatory response. In that respect, carriage of the TIRAP S180L heterozygous trait increases the likelihood to protect against pneumococcal LRTI, whereas children carrying the mutant homozygous TIRAP 180L polymorphism might be more likely susceptible to recurrent pneumococcal LRTI.

Neonates and infants are more vulnerable to infections and show reduced responses to vaccination. Consequently, repeated immunizations are required to induce protection and early life vaccines against major pathogens such as influenza are yet unavailable. Formulating antigens with potent adjuvants, including immunostimulators and delivery systems, is a demonstrated approach to enhance vaccine efficacy. Yet, adjuvants effective in adults may not meet the specific requirements for activating the early life immune system. Here, we assessed the neonatal adjuvanticity of three novel adjuvants including TLR4 (glucopyranosyl lipid adjuvant-squalene emulsion), TLR9 (IC31®), and Mincle (CAF01) agonists, which all induce germinal centers (GCs) and potent antibody responses to influenza hemagglutinin (HA) in adult mice. In neonates, a single dose of HA formulated into each adjuvant induced T follicular helper (TFH) cells. However, only HA/CAF01 elicited significantly higher and sustained antibody responses, engaging neonatal B cells to differentiate into GCs already after a single dose. Although antibody titers remained lower than in adults, HA-specific responses induced by a single neonatal dose of HA/CAF01 were sufficient to confer protection against influenza viral challenge. Postulating that the neonatal adjuvanticity of CAF01 may result from the functionality of the C-type lectin receptor (CLR) Mincle in early life we asked whether other C-type lectin agonists would show a similar neonatal adjuvanticity. Replacing the Mincle agonist trehalose 6,6′-dibehenate by Curdlan, which binds to Dectin-1, enhanced antibody responses through the induction of similar levels of TFH, GCs and bone marrow high-affinity plasma cells. Thus, specific requirements of early life B cells may already be met after a single vaccine dose using CLR-activating agonists, identified here as promising B cell immunostimulators for early life vaccines when included into cationic liposomes.

Influenza is a major cause of respiratory disease leading to hospitalization in young children. However, seasonal trivalent influenza vaccines (TIVs) have been shown to be ineffective and poorly immunogenic in this population. The development of live-attenuated influenza vaccines and adjuvanted vaccines are important advances in the prevention of influenza in young children. The oil-in-water emulsions MF59 and adjuvant systems 03 (AS03) have been used as adjuvants in both seasonal adjuvanted trivalent influenza vaccines (ATIVs) and pandemic monovalent influenza vaccines. Compared with non-adjuvanted vaccine responses, these vaccines induce a more robust and persistent antibody response for both homologous and heterologous influenza strains in infants and young children. Evidence of a significant improvement in vaccine efficacy with these adjuvanted vaccines resulted in the use of the monovalent (A/H1N1) AS03-adjuvanted vaccine in children in the 2009 influenza pandemic and the licensure of the seasonal MF59 ATIV for children aged 6 months to 2 years in Canada. The mechanism of action of MF59 and AS03 remains unclear. Adjuvants such as MF59 induce proinflammatory cytokines and chemokines, including CXCL10, but independently of type-1 interferon. This proinflammatory response is associated with improved recruitment, activation and maturation of antigen presenting cells at the injection site. In young children MF59 ATIV produced more homogenous and robust transcriptional responses, more similar to adult-like patterns, than did TIV. Early gene signatures characteristic of the innate immune response, which correlated with antibody titers were also identified. Differences were detected when comparing child and adult responses including opposite trends in gene set enrichment at day 3 postvaccination and, unlike adult data, a lack of correlation between magnitude of plasmablast response at day 7 and antibody titers at day 28 in children. These insights show the utility of novel approaches in understanding new adjuvants and their importance for developing improved influenza vaccines for children.

The continued participation of volunteers in clinical trials is crucial to advances in healthcare. Few data are available regarding the satisfaction and impressions of healthy volunteers after participation in phase I trials, many of which lead to unexpected adverse events. We report feedback from over 100 adult volunteers who took part in a first-in-human trial conducted in a high-income country testing an experimental Ebola vaccine causing significant reactogenicity, as well as unexpected arthritis in one fifth of participants. The anonymous, internet-based satisfaction survey was sent by email to all participants upon their completion of this one-year trial; it asked 24 questions concerning volunteers' motivations, impressions of the trial experience, and overall satisfaction. Answers were summarized using descriptive statistics. Of the 115 trial participants, 103 (90%) filled out the survey. Fifty-five respondents (53%) were male. Thirty-five respondents (34%) were healthcare workers, many of whom would deploy to Ebola-affected countries. All respondents cited scientific advancement as their chief motivation for participation, while 100/103 (97%) and 61/103 (59%) reported additional "humanitarian reasons" and potential protection from Ebolavirus, respectively. Although investigators had documented adverse events in 97% of trial participants, only 74 of 103 respondents (72%) recalled experiencing an adverse event. All reported an overall positive experience, and 93/103 (90%) a willingness to participate in future trials. Given the high level of satisfaction, no significant associations could be detected between trial experiences and satisfaction, even among respondents reporting adverse events lasting weeks or months. Despite considerable reactogenicity and unexpected vaccine-related arthritis, all survey respondents reported overall satisfaction. While this trial's context was unique, the positive feedback is likely due at least in part to the intense communication of trial information to participants, which included both general findings and personalized results.

Arenaviruses such as Lassa virus (LASV) can cause severe hemorrhagic fever in humans. As a major impediment to vaccine development, delayed and weak neutralizing antibody (nAb) responses represent a unifying characteristic of both natural infection and all vaccine candidates tested to date. To investigate the mechanisms underlying arenavirus nAb evasion we engineered several arenavirus envelope-chimeric viruses and glycan-deficient variants thereof. We performed neutralization tests with sera from experimentally infected mice and from LASV-convalescent human patients. NAb response kinetics in mice correlated inversely with the N-linked glycan density in the arenavirus envelope protein's globular head. Additionally and most intriguingly, infection with fully glycosylated viruses elicited antibodies, which neutralized predominantly their glycan-deficient variants, both in mice and humans. Binding studies with monoclonal antibodies indicated that envelope glycans reduced nAb on-rate, occupancy and thereby counteracted virus neutralization. In infected mice, the envelope glycan shield promoted protracted viral infection by preventing its timely elimination by the ensuing antibody response. Thus, arenavirus envelope glycosylation impairs the protective efficacy rather than the induction of nAbs, and thereby prevents efficient antibody-mediated virus control. This immune evasion mechanism imposes limitations on antibody-based vaccination and convalescent serum therapy.

BACKGROUND: The number of individuals with autoimmune inflammatory rheumatic diseases (AIIRDs) treated with immunosuppressive drugs is increasing steadily. The variety of immunosuppressive drugs and, in particular, biological therapies is also rising. The immunosuppressants, as well as the AIIRD itself, increase the risk of infection in this population. Thus, preventing infections by means of vaccination is of utmost importance. New Swiss vaccination recommendations for AIIRD patients were initiated by the Swiss Federal Office of Public Health and prepared by a working group of the Federal Commission for Vaccination Issues as well as by consultation of international experts. METHODS: A literature search was performed in electronic databases (Cochrane, Medline, PubMed, Embase). In addition, unpublished literature was identified through a targeted website search of relevant organisations and international conferences dealing with vaccination, infectious diseases and rheumatology. RESULTS: Although data are scarce, the following main points were retrieved from the literature. Inactivated vaccines are safe, but their immunogenicity may be reduced in AIIRD patients, especially if they are under immunosuppressive therapy. Rituximab and abatacept appear to reduce significantly immune responses after vaccination. Live vaccines are generally contraindicated under immunosuppressive therapy owing to safety concerns. Specific exceptions, as well as time intervals for the administration of live vaccines after interruption of an immunosuppressive therapy, have been formulated in this article. CONCLUSION: More evidence regarding the immunogenicity and safety of vaccinations in AIIRD patients under various therapies is needed. Vaccination recommendations should be updated on a regular basis, as more scientific data will become available.

Bordetella holmesii, an emerging pathogen, can be misidentified as Bordetella pertussis by routine polymerase chain reaction (PCR). In some reports, up to 29% of the patients diagnosed with pertussis have in fact B. holmesii infection and invasive, non-respiratory B. holmesii infections have been reported worldwide. This misdiagnosis undermines the knowledge of pertussis' epidemiology, and may lead to misconceptions on pertussis vaccine's efficacy. Recently, the number of whooping cough cases has increased significantly in several countries. The aim of this retrospective study was to determine whether B. holmesii was contributing to the increase in laboratory-confirmed cases of B. pertussis in Switzerland. A multiplex species-specific quantitative PCR assay was performed on 196 nasopharyngeal samples from Swiss patients with PCR-confirmed Bordetella infection (median age: 6 years-old, minimum 21 days-old, maximum 86 years-old), formerly diagnosed as Bordetella pertussis (IS481+). No B. holmesii (IS481+, IS1001-, hIS1001+) was identified. We discuss whether laboratories should implement specific PCR to recognize different Bordetella species. We conclude that in Switzerland B. holmesii seems to be circulating less than in neighboring countries and that specific diagnostic procedures are not necessary routinely. However, as the epidemiological situation may change rapidly, periodic reevaluation is suggested.

Infant mortality from viral infection remains a major global health concern: viruses causing acute infections in immunologically mature hosts often follow a more severe course in early life, with prolonged or persistent viral replication. Similarly, the WE strain of lymphocytic choriomeningitis virus (LCMV-WE) causes acute self-limiting infection in adult mice but follows a protracted course in infant animals, in which LCMV-specific CD8⁺ T cells fail to expand and control infection. By disrupting type I IFNs signaling in adult mice or providing IFN-α supplementation to infant mice, we show here that the impaired early life T cell responses and viral control result from limited early type I IFN responses. We postulated that plasmacytoid dendritic cells (pDC), which have been identified as one major source of immediate-early IFN-I, may not exert adult-like function in vivo in the early life microenvironment. We tested this hypothesis by studying pDC functions in vivo during LCMV infection and identified a coordinated downregulation of infant pDC maturation, activation and function: despite an adult-like in vitro activation capacity of infant pDCs, the expression of the E2-2 pDC master regulator (and of critical downstream antiviral genes such as MyD88, TLR7/TLR9, NF-κB, IRF7 and IRF8) is downregulated in vivo at baseline and during LCMV infection. A similar pattern was observed in response to ssRNA polyU, a model ligand of the TLR7 viral sensor. This suggests that the limited T cell-mediated defense against early life viral infections is largely attributable to / regulated by infant pDC responses and provides incentives for novel strategies to supplement or stimulate immediate-early IFN-α responses.

Memory responses require immune competence. We assessed the influence of priming with AS03-adjuvanted pandemic vaccine (Pandemrix®) on memory responses of HIV patients, kidney recipients (SOT) and healthy controls (HC).Participants (HIV: 197, SOT: 53; HC: 156) were enrolled in a prospective study and 390/406 (96%) completed it. All had been primed in 2009/2010 with 1 (HC) or 2 (patients) doses of Pandemrix®, and were boosted with the 2010/2011 seasonal influenza vaccine. Geometric mean titres and seroprotection rates were measured 12 months after priming and 4 weeks after boosting. Primary and memory responses were directly compared in 191 participants (HCW: 69, HIV: 71, SOT: 51) followed during 2 consecutive seasons.Most participants (HC: 77.8%, HIV: 77.6%, SOT: 66%) remained seroprotected at 12 months post-priming. Persisting A/09/H1N1 titers were high in HIV (100.2) and HC (120.1), but lower in SOT (61.4) patients. Memory responses reached higher titers in HIV (507.8) than in HC (253.5) and SOT (136.9) patients. Increasing age and lack of HAART reduced persisting and memory responses, mainly influenced by residual antibody titers. Comparing 2009/2010 and 2010/2011 titers in 191 participants followed for 2 seasons indicated lower post-2010/2011 titers in HC (240.2 vs 313.9), but higher titers in HIV (435.7 vs 338.0) and SOT (136 vs 90.3) patients.Priming with 2 doses of Pandemrix® elicited persistent antibody responses and even stronger memory responses to non-adjuvanted seasonal vaccine in HIV patients than 1 dose in healthy subjects. Adjuvanted influenza vaccines may improve memory responses of immunocompromised patients.ClinicalTrials.gov NCT01022905.

Background Responses to influenza vaccines are poorly characterized in immunocompromised patients. The goal of this study was to assess the efficacy of the AS03-adjuvanted influenza H1N1/A/09 vaccine in allogeneic hematopoietic stem cell transplant recipients.Design and Methods We enrolled 65 patients and 138 controls in an open prospective study. Controls received one dose and patients 2 doses of the AS03-adjuvanted influenza H1N1/A/09 vaccine at a 3-week interval. Geometric mean titers and seroprotection/seroconversion rates were determined by hemagglutination inhibition before and four weeks after the last immunization. Clinical and biological markers, including immunoglobulins, CD3+, CD4+, CD8+ and naïve CD4+ T-cell counts were assessed in all patients.Results Baseline seroprotection rates were low in patients (6.6%) and controls (14.8%). After 2 doses, patients (n=57, 92.3%) achieved similar seroprotection rates (84% vs. 87%, P=0.65) and antibody titers (305 vs. 340, P=0.88) as controls (n=131, 93.9%) after one dose. In univariate analysis, transplant-to-vaccination interval less than 12 months, active graft-versus-host disease, immunosuppressive drugs, hemoglobin less than 12g/L, lymphopenia less than1G/L, IgG less than 4g/L, IgA less than 0.5g/L, IgM less than 0.5g/L and naive CD4+ T cells less than 150/μL were significantly associated with weaker responses. Multivariate analysis identified transplant-to-vaccination interval and active graft-versus-host disease as the most powerful negative predictors of antibody responses (P=0.04 and P=0.002, respectively). Vaccination was well tolerated in both cohorts.Conclusions In allogeneic hematopoietic stem cell transplant recipients, 2 doses of an adjuvanted influenza vaccine elicited comparable responses to a single dose in healthy individuals. However, vaccine responses remained poor in patients with ongoing graft-versus-host disease, supporting the need for additional strategies in this high-risk patient population. (ClinicalTrials.gov Identifier: NCT01022905)

CD8 T cells are recognized key players in control of persistent virus infections, but increasing evidence suggests that assistance from other immune mediators is also needed. Here, we investigated whether specific antibody responses contribute to control of lymphocytic choriomeningitis virus (LCMV), a prototypic mouse model of systemic persistent infection. Mice expressing transgenic B cell receptors of LCMV-unrelated specificity, and mice unable to produce soluble immunoglobulin M (IgM) exhibited protracted viremia or failed to resolve LCMV. Virus control depended on immunoglobulin class switch, but neither on complement cascades nor on Fc receptor gamma chain or Fc gamma receptor IIB. Cessation of viremia concurred with the emergence of viral envelope-specific antibodies, rather than with neutralizing serum activity, and even early nonneutralizing IgM impeded viral persistence. This important role for virus-specific antibodies may be similarly underappreciated in other primarily T cell-controlled infections such as HIV and hepatitis C virus, and we suggest this contribution of antibodies be given consideration in future strategies for vaccination and immunotherapy.

BACKGROUND: In the search for more potent and safer tuberculosis vaccines, CAF01 was identified as a remarkable formulation. Based on cationic liposomes and including a synthetic mycobacterial glycolipid as TLR-independent immunomodulator, it induces strong and protective T helper-1 and T helper-17 adult murine responses to Ag85B-ESAT-6, a major mycobacterial fusion protein. Here, we assessed whether these properties extend to early life and how CAF01 mediates its adjuvant properties in vivo. METHODS/FINDINGS: Following adult or neonatal murine immunization, Ag85B-ESAT-6/CAF01 similarly reduced the post-challenge bacterial growth of M. bovis BCG, whereas no protection was observed using Alum as control. This protection was mediated by the induction of similarly strong Th1 and Th17 responses in both age groups. Multifunctional Th1 cells were already elicited after a single vaccine dose and persisted at high levels for at least 6 months even after neonatal priming. Unexpectedly, this potent adjuvanticity was not mediated by a massive targeting/activation of dendritic cells: in contrast, very few DCs in the draining lymph nodes were bearing the labeled antigen/adjuvant. The increased expression of the CD40 and CD86 activation markers was restricted to the minute portion of adjuvant-bearing DCs. However, vaccine-associated activated DCs were recovered several days after immunization. CONCLUSION: The potent adult and neonatal adjuvanticity of CAF01 is associated in vivo with an exquisite but prolonged DC uptake and activation, fulfilling the preclinical requirements for novel tuberculosis vaccines to be used in early life.

BACKGROUND: With the exception of some live vaccines, e.g. BCG, subunit vaccines formulated with "classical" adjuvants do not induce similar responses in neonates as in adults. The usual neonatal profile is characterized by lower levels of TH1-associated biomarkers. This has hampered the development of new neonatal vaccines for diseases that require early protection. Tuberculosis is one of the major targets for neonatal immunization. In this study, we assessed the immunogenicity of a novel candidate vaccine comprising a mycobacterial fusion protein, Ag85B-ESAT-6, in a neonatal murine immunization model. METHODS/FINDINGS: The Ag85B-ESAT-6 fusion protein was formulated either with a classical alum based adjuvant or with the novel IC31 adjuvant. Following neonatal or adult immunization, 3 parameters were studied in vivo: (1) CD4(+) T cell responses, (2) vaccine targeting/activation of dendritic cells (DC) and (3) protection in a surrogate mycobacterial challenge model. Conversely to Alum, IC31 induced in both age groups strong Th1 and Th17 responses, characterized by multifunctional T cells expressing IL-2 and TNF-alpha with or without IFN-gamma. In the draining lymph nodes, a similarly small number of DC contained the adjuvant and/or the antigen following neonatal or adult immunization. Expression of CD40, CD80, CD86 and IL-12p40 production was focused on the minute adjuvant-bearing DC population. Again, DC targeting/activation was similar in adults and neonates. These DC/T cell responses resulted in an equivalent reduction of bacterial growth following infection with M. bovis BCG, whereas no protection was observed when Alum was used as adjuvant. CONCLUSION: Neonatal immunization with the IC31-adjuvanted Ag85B-ESAT-6 subunit vaccine elicited adult-like multifunctional protective anti-mycobacterial T cell responses through the induction of an adult pattern of in vivo DC activation.