Neutralizing Antibody Responses Research Articles

Effect of vaccination against foot-and-mouth disease during mid-pregnancy on the neutralizing antibody response in the cow.

As pregnancy can adversely affect the immune response of vaccination against foot and mouth disease virus (FMDV) due to physiological immunosuppressive milieu, we tested the effect of FMDV vaccination during mid-gestation on the antibody response. Pregnant and non-pregnant cows of crossbred and indigenous breed (n=28/group) were vaccinated with inactivated FMD vaccine covering O, A, and Asia1 serotypes and the sera were harvested at weekly interval till day 42 post-vaccination. Virus neutralization test (VNT) was done and the analysis of log10 VN50 antibody titer by mixed model ANOVA indicated that pregnancy did not significantly affect the log10 VN50 titer for FMDV serotype O and Asia1. Though pregnancy significantly decreased the titer for FMDV serotype A, the effect size was small. The experiment was repeated in purebred HF cows (n=10/group) and the results were reproducible. It was concluded that mid-pregnancy would not hamper the herd immunity to FMD vaccination in the cow.

Comparison of neuraminidase inhibiting antibody responses elicited by egg- and cell-derived influenza vaccines.

An immunogenicity sub-study was performed within a clinical trial comparing the effectiveness of egg, cell, and recombinant hemagglutinin (HA)-derived influenza vaccines during the 2018-2019 and 2019-2020 influenza seasons. NAI and neutralizing antibody titers against the A(H1N1)pdm09 and A(H3N2) components of the vaccines were measured in pre- and post-vaccination sera. Responses to the N1 component of eIIV and cIIV were different in both study years 1 and 2 whereas response rate and antibody titers to the N2 component of egg and cell culture-derived vaccines were similar. For example, 43.5% of eIIV and no cIIV recipients had four-fold NAI titer increases in year 1. There was a weak positive correlation between responses to N1 and N2 for both vaccine types but no correlation between NAI and HA-specific neutralizing antibody responses. Recombinant HA vaccine that does not contain NA served as a specificity control; NAI antibody titers did not increase in recipients except in two individuals presumed to have subclinical infection. Antibody responses to NA following vaccination with eIIV and cIIV were not the same; although the responses to the N1 and N2 components of eIIV were similar, there were fewer responders to N1 than N2 of cIIV. Studies to determine the impact of NA immunity on influenza vaccine effectiveness are warranted.

CoviWall, a whole-virion-inactivated B.1.617.2 vaccine candidate, induces potent humoral and Th1 cell response in mice and protects against B.1.617.2 strain challenge in Syrian hamsters

Rapid development of coronavirus disease 2019 (COVID-19) vaccines and antiviral drugs have significantly reduced morbidity and mortality worldwide. Although most of the vaccines were developed initially with the ancestral Wuhan antigen, here, we report the development and immunological efficacy of a whole-virion–inactivated vaccine candidate (CoviWall) to combat the deadly B.1.617.2 (Delta strain) infection. In the current study, we demonstrate a consistent manufacturing process under Good Manufacturing Practice for the development of CoviWall and its characterization using various analytical methods as per regulatory compliance. In addition, we provide pre-clinical immunogenicity and protective efficacy data of the CoviWall vaccine. All the three test doses (i.e., low dose, mid dose, and high dose) immunized in C57BL/6 mice elicited a high titer of anti–receptor-binding domain antibody and neutralizing antibody response against severe acute respiratory syndrome coronavirus–2 (SARS-CoV-2) after second booster dose. In addition, CoviWall immunization also produced a significant T-cell response in the immunized animals. Our B.1.617.2 strain challenge data in Syrian hamsters indicate that immunized hamsters show attenuated clinical manifestations of COVID-19 with reduced lung viral load. Moreover, assessment of pulmonary histopathology revealed lower cellular injury, inflammation, and pneumonia in the vaccinated hamsters as compared to the unvaccinated animals. Such promising results augur well for the clinical phase I trial of the CoviWall vaccine and further development against contagious SARS-CoV-2 strains in the future.

The Long-Term Immunity of a Microneedle Array Patch of a SARS-CoV-2 S1 Protein Subunit Vaccine Irradiated by Gamma Rays in Mice.

COVID-19 vaccines effectively prevent severe disease, but unequal distribution, especially in low- and middle-income countries, has led to vaccine-resistant strains. This highlights the urgent need for alternative vaccine platforms that are safe, thermostable, and easy to distribute. This study evaluates the immunogenicity, stability, and scalability of a dissolved microneedle array patch (MAP) delivering the rS1RS09 subunit vaccine, comprising the SARS-CoV-2 S1 monomer and RS09, a TLR-4 agonist peptide. The rS1RS09 vaccine was administered via MAP or intramuscular injection in murine models. The immune responses of the MAP with and without gamma irradiation as terminal sterilization were assessed at doses of 5, 15, and 45 µg, alongside neutralizing antibody responses to Wuhan, Delta, and Omicron variants. The long-term storage stability was also evaluated through protein degradation analyses at varying temperatures. The rS1RS09 vaccine elicited stronger immune responses and ACE2-binding inhibition than S1 monomer alone or trimer. The MAP delivery induced sgnificantly higher and longer-lasting S1-specific IgG responses for up to 70 weeks compared to intramuscular injections. Robust Th2-prevalent immune responses were generated in all the groups vaccinated via the MAP and significant neutralizing antibodies were elicited at 15 and 45 µg, showing dose-sparing potential. The rS1RS09 in MAP has remained stable with minimal protein degradation for 19 months at room temperature or under refrigeration, regardless of gamma-irradiation. After an additional month of storage at 42 °C, cit showed less than 3% degradation, ompared to over 23% in liquid vaccines Conclusions: Gamma-irradiated MAP-rS1RS09 is a promising platform for stable, scalable vaccine production and distribution, eliminating cold chain logistics. These findings support its potential for mass vaccination efforts, particularly in resource-limited settings.

The Development of a Novel Broad-Spectrum Influenza Polypeptide Vaccine Based on Multi-Epitope Tandem Sequences.

Polypeptide vaccines have the potential to improve immune responses by targeting conserved and weakly immunogenic regions in antigens. This study aimed to identify and evaluate the efficacy of a novel influenza universal vaccine candidate consisting of multiple polypeptides derived from highly conserved regions of influenza virus proteins hemagglutinin (HA), neuraminidase (NA), and matrix protein 2 (M2). Immunoinformatics tools were used to screen conserved epitopes from different influenza virus subtypes (H1N1, H3N2, H5N1, H7N9, H9N2, and IBV). A polypeptide vaccine, P125-H, was constructed by linking multiple epitopes using Ii-Key technology. The immunogenicity of P125-H was assessed in mice using MF59-adjuvanted P125-H via intraperitoneal injection. Hemagglutination inhibition (HI) and neutralizing antibody responses were measured, along with IFN-γ levels in spleen lymphocytes. Protective efficacy was evaluated using viral challenge with lethal doses of H1N1 and H7N9. Mice immunized with P125-H generated high levels of HI and neutralizing antibodies against multiple influenza strains. IFN-γ production was significantly elevated in spleen lymphocytes upon stimulation with the vaccine. P125-H protected mice from influenza infection, reducing weight loss and the viral load in the lungs, mitigating lung pathology, and decreasing mortality. The P125-H vaccine induced broad cross-protection against multiple influenza strains and elicited robust immune responses. It demonstrates strong potential as a candidate for a universal influenza vaccine.

Anti-immune complex antibodies are elicited during repeated immunization with HIV Env immunogens.

Vaccination strategies against HIV-1 aim to elicit broadly neutralizing antibodies (bnAbs) using prime-boost regimens with HIV envelope (Env) immunogens. Epitope mapping has shown that early antibody responses are directed to easily accessible nonneutralizing epitopes on Env instead of bnAb epitopes. Autologously neutralizing antibody responses appear upon boosting, once immunodominant epitopes are saturated. Here, we use electron microscopy-based polyclonal epitope mapping (EMPEM) to elucidate how repeated immunization with HIV Env SOSIP immunogens results in the generation of Ab2α anti-idiotypic antibodies in rabbits and rhesus macaques. We present the structures of six anti-immune complex antibodies and find that they target idiotopes composed of framework regions of antibodies bound to Env. Examination of cryo-electron microscopy density enabled prediction of sequences for an anti-immune complex antibody, the paratope of which is enriched with aromatic amino acids. This work sheds light on current vaccine development efforts for HIV, as well as for other pathogens in which repeated exposure to antigen is required.

Distinct CD8+ T-cell types Associated with COVID-19 Severity in Unvaccinated HLA-A2+ Patients.

Although emerging data have revealed the critical role of memory CD8+ T cells in preventing and controlling SARS-CoV-2 infection, virus-specific CD8+ T-cell responses against SARS-CoV-2 and its memory and innate-like subsets in unvaccinated COVID-19 patients with various disease manifestations in an HLA-restricted fashion remain to be understood. Here, we show the strong association of protective cellular immunity with mild COVID-19 and unique cell types against SARS-CoV-2 virus in an HLA-A2 restricted manner. ELISpot assays reveal that SARS-CoV-2-specific CD8+ T-cell responses in mild COVID-19 patients are significantly higher than in severe patients, whereas neutralizing antibody responses against SARS-CoV-2 virus significantly correlate with disease severity. Single-cell analyses of HLA-A2-restricted CD8+ T cells, which recognize highly conserved immunodominant SARS-CoV-2-specific epitopes, demonstrate divergent profiles in unvaccinated patients with mild versus severe disease. CD8+ T-cell types including cytotoxic KLRB1 + CD8αα cells with innate-like T-cell signatures, IFNG hi ID3 hi memory cells and IL7R + proliferative stem cell-like memory cells are preferentially observed in mild COVID-19, whereas distinct terminally-differentiated T-cell subsets are predominantly detected in severe COVID-19: highly activated FASL hi T-cell subsets and early-terminated or dysfunctional IL4R + GATA3 + stem cell-like memory T-cell subset. In conclusion, our findings suggest that unique and contrasting SARS-CoV-2-specific CD8+ T-cell profiles may dictate COVID-19 severity.

Safety and Immunogenicity of SARS-CoV-2 Spike Receptor-Binding Domain andN-Terminal Domain mRNA Vaccine.

mRNA-1283 is an investigational COVID-19 mRNA vaccine encoding the receptor-binding and N-terminal domains of the SARS-CoV-2 spike protein in contrast to the original mRNA-1273, which encodes the full-length spike protein. A phase 2a, dose-ranging, observer-blind, randomized study (NCT05137236) conducted in adults (≥18 years) previously vaccinated with mRNA-1273 evaluated the safety and immunogenicity of a single dose of mRNA-1283 (2.5, 5, and 10 µg) and its bivalent formulation, mRNA-1283.211 (5 and 10 µg; encoding original SARS-CoV-2 and Beta) against the comparator mRNA-1273, 50 µg (Part A). A subsequent, open-label study part (Part B) evaluated the safety and immunogenicity of a monovalent Omicron BA.1 vaccine, mRNA-1283.529 (5 and 10 µg). A total of 340 participants were randomized in Part A, and 200 participants were enrolled in Part B. All dose levels of mRNA-1283 vaccines were well tolerated and increased the neutralizing antibody (nAb) responses at Day 29 compared to baseline against SARS-CoV-2 D614G and Beta. The nAb responses elicited by mRNA-1283 were higher than those elicited by mRNA-1273. mRNA-1283.529 (Part B) increased nAb at Day 29 against Omicron BA.1. Antibody responses remained detectable for a year post-vaccination. mRNA-1283 was well tolerated and exhibited improved immunogenicity compared to mRNA-1273.

A Broad Survey and Functional Analysis of Immunoglobulin Loci Variation in Rhesus Macaques.

Rhesus macaques (RMs) are vital models for studying human disease, and are invaluable to pre-clinical pipelines for vaccine discovery and testing. Particularly in this regard, they are often used to study infection and vaccine-associated broadly neutralizing antibody responses. This has resulted in an increasing demand for improved genetic resources for the immunoglobulin (IG) loci, which harbor antibody-encoding genes. However, the highly polymorphic and structurally variable nature of these loci have them historically challenging to sequence and characterize at the level of both the genome and expressed repertoire. To address these challenges, we have developed a novel integrated analysis workflow for conducting the combined processing of B cell receptor repertoire sequencing data with matched whole-genome and targeted long-read genomic sequencing data. Using this novel approach, we have assembled the largest collection of IG germline alleles reported to date, amassed from 106 Indian origin RMs. Using a conservative annotation approach, requiring sample-level internal validation from both genomic and expressed datasets, we created a comprehensive resource that captures extensive diversity of IG heavy and light chain variable (V), diversity (D), and joining (J) alleles, as well as leader, intronic, and recombination signal sequences (RSSs). This publicly available, continually updated database will advance vaccine research for infectious disease, and provide a robust foundation for immunogenomics and future translational research.

Host cell lectins ASGR1 and DC-SIGN jointly with TMEM106B confer ACE2 independence and imdevimab resistance to SARS-CoV-2 pseudovirus with spike mutation E484D.

The naturally occurring mutation E484D in the spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can render viral entry ACE2 independent and imdevimab resistant. Here, we investigated whether the cellular proteins ASGR1, DC-SIGN, and TMEM106B, which interact with the viral S protein, can contribute to these processes. Employing S protein-pseudotyped particles, we found that expression of ASGR1 or DC-SIGN jointly with TMEM106B allowed for robust entry of mutant E484D into otherwise non-susceptible cells, while this effect was not observed upon separate expression of the single proteins and upon infection with SARS-CoV-2 wild type (WT). Furthermore, expression of ASGR1 or DC-SIGN conferred ACE2 independence and imdevimab resistance to entry of mutant E484D but not WT, and entry under those conditions was dependent on endogenous TMEM106B. These results suggest that engagement of certain cellular lectins can direct SARS-CoV-2 mutant E484D to an ACE2-independent, TMEM106B-dependent entry pathway that is not inhibited by imdevimab.IMPORTANCEThe interaction of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein with the ACE2 receptor determines the viral cell tropism and is the key target of the neutralizing antibody response. Here, we show that SARS-CoV-2 with a single, naturally occurring mutation in the spike protein, E484D, can use the cellular lectins ASGR1 and DC-SIGN in conjunction with TMEM106B for ACE2-independent entry and evasion of therapeutic antibodies. These results suggest that engagement of cellular lectins might modulate target cell choice of SARS-CoV-2 and might allow evasion of certain neutralizing antibodies.

A self-assembled nanoparticle vaccine elicits effective neutralizing antibody response against EBV infection.

Epstein-Barr virus (EBV) is a significant global public health concern because of its association with various malignancies and autoimmune diseases. Over 90% of the global population is chronically infected with EBV, impacting numerous cancer-related cases annually. However, none of the effective prophylactic vaccines against EBV is approved at present. In this study, we developed a novel vaccine candidate based on epitope peptides from the receptor-binding domain of EBV-encoded gp350 glycoprotein to prevent EBV infection. These epitope peptides detected a binding capability with host cells were then fused by flexibility linkers and expressed in Escherichia coli to reduce the unnecessary glycan modifications to simulate their free-glycan status. The fused recombinant protein (L350) was displayed on the surface of ferritin-based nanoparticle. The immunogenicity of the L350-ferritin nanoparticle was evaluated in Balb/c mice, and the neutralizing titers of sera from immunized mice were detected by means of an infection blocking assay in an in vitro cell model. All the five epitope peptides could bind to AKATA cells, and their fused recombinant protein (L350) was successfully presented on the surface of self-assembled ferritin nanoparticles. Sera from the L350-ferritin nanoparticle-immunized mice showed high titers of both L350 protein-specific and gp350D123 protein-specific antibodies, and sera from gp350D123 protein-immunized mice could also recognize L350 protein well. Most importantly, the L350-ferritin nanoparticle induced efficient neutralizing antibodies to block EBV-GFP infection in AKATA cells and also constructed a strong antigen-specific B-cell memory in immunized mice. Moreover, histopathological changes of main tissues from all vaccinated mice were not observed. These data indicate that the L350-ferritin nanoparticle vaccine candidate has considerable potential application in preventing EBV infection and provides a promising basis for developing prophylactic EBV vaccines.

Self-assembling nanoparticle vaccine elicits a robust protective immune response against avian influenza H5N6 virus in chickens

The continuous circulation and evolution of the H5N6 subtype highly pathogenic avian influenza virus (HPAIV) challenge the development of the global poultry industry and human public health security. To address the potential threat of the H5N6 virus, a secure and efficacious vaccine is urgent. In our research, a self-assembling nanoparticle vaccine presenting the hemagglutinin of the H5N6 AIV was developed based on the ferritin antigen display platform. The results showed that a single-dose vaccination of this nanoparticle vaccine elicited potent hemagglutination inhibition (HI) antibody responses and neutralizing antibody responses in the chickens. Meanwhile, the fused HA-ferritin nanoparticle vaccine induced significantly higher levels of Th1/Th2 immune responses. After a lethal attack with the H5N6 virus, the fused HA-ferritin nanoparticle vaccine conferred chickens with 100 % (10/10) challenge protection. Importantly, the fused HA-ferritin nanoparticle with only 28 hemagglutination units (HAU) provided chickens with immune protection comparable to commercial inactivated vaccines and protected the chickens from severe lung pathological damage. These results in our study support the superiority of ferritin as an antigen display platform and suggest that self-assembled nanoparticle vaccines based on this platform possess the potential as an avian influenza candidate vaccine.

Immunogenicity and safety of a monovalent omicron XBB.1.5 SARS-CoV-2 recombinant spike protein vaccine as a heterologous booster dose in US adults: interim analysis of a single-arm phase 2/3 study.

Authorities globally recommended a monovalent omicron XBB.1.5-based COVID-19 vaccine for the 2023-24 season. The Novavax COVID-19 vaccine, NVX-CoV2601, contains XBB.1.5 recombinant spike protein, based on an authorised prototype vaccine (NVX-CoV2373) technology. We aimed to determine whether a single dose of NVX-CoV2601 versus NVX-CoV2373 (from a previous study [2019nCoV-311 part 2]) produced superior neutralising antibody (nAb) responses, and non-inferior seroresponse rates to XBB.1.5, after three or more previous mRNA-based COVID-19 vaccinations. In part 1 of this single-arm, phase 2/3 study (2019nCoV-313), participants aged 18 years or older who had been previously vaccinated with three or more doses of mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech) were enrolled across 30 US centres (research groups and universities) located across 20 states. Participants received one intramuscular injection of NVX-CoV2601 (5 μg XBB.1.5 spike plus 50 μg Matrix-M adjuvant). Coprimary endpoints were superiority of baseline-adjusted nAb geometric mean XBB.1.5 titres (adjusted GMTs), with superiority declared when the lower bound of the 95% CI for the GMT ratio (GMTR) was greater than 1, and non-inferiority of seroresponse rates, with non-inferiority declared when the lower bound of the 95% CI for the seroresponse rate difference was greater than -10%, on day 28; comparisons were made for NVX-CoV2601 administered in this study versus NVX-CoV2373 administered in part 2 (group G) of the 2019nCoV-311 study. Coprimary endpoints were assessed in the per-protocol immunogenicity set (ie, all participants who received study vaccine, underwent 28 days of follow-up, had day 0 and day 28 samples available, and had no major protocol deviations). Safety was a secondary endpoint and included assessments of solicited treatment-emergent adverse events up to 7 days and unsolicited treatment-emergent adverse events up to 28 days after vaccination in the safety analysis set (ie, all participants who received study vaccine). Here we report the prespecified interim analysis of immunogenicity and safety up to day 28. This study is registered with ClinicalTrials.gov, NCT05975060, and is now complete. Between Sept 7 and Sept 8, 2023, 380 individuals were screened, of whom 332 were enrolled and received study vaccine. At the 28-day interim analysis database lock (Jan 17, 2023), the per-protocol analysis sets included 309 (93%) of 332 NVX-CoV2601 recipients and 227 (90%) of 252 NVX-CoV2373 recipients. Mean age of NVX-CoV2601 recipients was 52·1 years (SD 16·1); 192 (62%) of 309 were female and 117 (38%) were male. Mean age of NVX-CoV2373 recipients was 42·2 years (13·4); 128 (56%) of 227 were female and 99 (44%) were male. At day 28, the baseline-adjusted nAb GMT for NVX-CoV2601 was 905·9 (95% CI 807·1-1016·8) and for NVX-CoV2373 was 156·6 (137·0-179·0); the between-group adjusted GMTR was 5·8 (95% CI 4·9-6·9). In the per-protocol immunogenicity set, seroresponse rates were 64% (196 of 305) among recipients of NVX-CoV2601 and 7% (16 of 227) among recipients of NVX-CoV2373, with a seroresponse rate difference of 57% (95% CI 51-63). In the NVX-CoV2601 group, within 7 days, solicited local treatment-emergent adverse events were reported in 189 (57%) of 332 participants (including one [<1%] grade 3 or worse event; tenderness) and solicited systemic treatment-emergent adverse events were reported in 158 (48%) participants (including four [1%] participants with one or more grade 3 events; malaise [n=3], headache [n=2], fatigue [n=1], and muscle pain [n=1]). The most common solicited treatment-emergent adverse events were tenderness (171 [52%]) and pain (98 [30%]) at the injection site, fatigue (97 [29%]), and muscle pain (97 [29%]). Up to day 28, unsolicited adverse events considered related to study vaccination in the NVX-CoV2601 group occurred in five (2%) participants (one for each of asthma, axillary pain, diarrhoea, hypertension [which was medically attended], and presyncope). No serious adverse events due to study product, adverse events of special interest, or deaths due to study product occurred, and no study discontinuations due to treatment-emergent adverse events occurred. The coprimary endpoints were met, and NVX-CoV2601 was well tolerated. These interim data support NVX-CoV2601 use per guidance for XBB.1.5-directed COVID-19 vaccines and demonstrate the adaptability of this vaccine platform for updated SARS-CoV-2 spike proteins. Novavax.

Concurrent but consecutive vaccination of modified live PRRSV-1 and PRRSV-2 provides better protection in nursery pigs.

Porcine reproductive and respiratory syndrome (PRRS) virus is a severe threat to the global swine industry. Modified live virus vaccines (MLVs) for two PRRSV species (PRRSV-1 and PRRSV-2) are the most widely used approach to control PRRSV-caused diseases. For swine herds influenced by PRRSV-1 and PRRSV-2, how to rationalize MLV immunization strategies for robust and cross-protective immune responses has been a long-lasting need. In this study, we found that the replication of PRRSV-1 is strongly suppressed by co-infection with PRRSV-2 in vitro, especially under concurrent co-infection conditions. We compared the adaptive immune responses between consecutive and concurrent vaccination methods in nursery pigs, vaccinated either 3 days apart (PRRSV-1 MLV followed by PRRSV-2 MLV, consecutive) or together on the same day (concurrent). PRRSV-1 RNAs were mainly detectable in the sera of consecutively vaccinated pigs. In contrast, PRRSV-2 RNAs in sera were not changed in both vaccination strategies. After the homologous PRRSV-1 or PRRSV-2 challenge, we found that consecutive vaccination slightly improved PRRSV-1 viremia clearance and did not attenuate the PRRSV-2 viremia clearance. Both vaccination strategies induced comparable T-helper cell responses against PRRSV-1 and PRRSV-2 in peripheral blood before and after the challenge. Interestingly, consecutive vaccination induced significantly higher PRRSV-1-specific post-challenge T-helper and cytotoxic T cells responses in the tracheobronchial lymph nodes than concurrent vaccination. Furthermore, consecutive vaccination significantly improved neutralizing antibody responses against PRRSV-1 and PRRSV-2 in comparison with concurrent vaccination. In conclusion, consecutive vaccination appears to be better for viral clearance and induction of adaptive immune response, and our study provides a preliminary rationale to optimize PRRS MLV immunization strategy for better dual protection.

Rapid Recovery From SARS-CoV-2 Infection Among Immunocompromised Children Despite Limited Neutralizing Antibody Response: A Virologic and Sero-Immunologic Analysis of a Single-Center Cohort

Rapid Recovery From SARS-CoV-2 Infection Among Immunocompromised Children Despite Limited Neutralizing Antibody Response: A Virologic and Sero-Immunologic Analysis of a Single-Center Cohort

Distinct Neutralising and Complement-Fixing Antibody Responses Can Be Induced to the Same Antigen in Haemodialysis Patients After Immunisation with Different Vaccine Platforms.

Background/Objectives: Generalised immune dysfunction in chronic kidney disease, especially in patients requiring haemodialysis (HD), significantly enhances the risk of severe infections. Vaccine-induced immunity is typically reduced in HD populations. The SARS-CoV-2 pandemic provided an opportunity to examine the magnitude and functionality of antibody responses in HD patients to a previously unencountered antigen-Spike (S)-glycoprotein-after vaccination with different vaccine platforms (viral vector (VV); mRNA (mRV)). Methods: We compared the total and functional anti-S antibody responses (cross-variant neutralisation and complement binding) in 187 HD patients and 43 healthy controls 21-28 days after serial immunisation. Results: After 2 doses of the same vaccine, HD patients had anti-S antibody levels and a complement binding capacity comparable to controls. However, 2 doses of mRV induced greater polyfunctional antibody responses than VV (defined by the presence of both complement binding and cross-variant neutralisation activity). Interestingly, an mRV boost after 2 doses of VV significantly enhanced antibody functionality in HD patients without a prior history of SARS-CoV-2 infection. Conclusions: HD patients can generate near-normal, functional antigen-specific antibody responses following serial vaccination to a novel antigen. Encouragingly, exploiting immunological memory by using mRNA vaccines and boosting may improve the success of vaccination strategies in this vulnerable patient population.

Human adenovirus species B knob proteins as immunogens for inducing cross-neutralizing antibody responses.

The re-emerging human adenovirus (HAdV) types 3, 7, 14, and 55 of species B have caused severe or even fatal acute respiratory disease. Therefore, the development of multivalent vaccines against HAdV types 3, 7, 14, and 55 remains an important goal. In our previous study, we identified a cross-neutralizing epitope that induced broadly reactive monoclonal neutralizing antibodies against the knob proteins of HAdV types 7, 11, 14, and 55. To study the immunogenicity of HAdV species B knob proteins, we evaluated humoral immune responses to the knob proteins in vivo and in vitro. We found that the knob proteins elicited robust binding and neutralizing antibody responses after three immunizations of mice. In addition, mouse antisera raised against the knob proteins exhibited cross-neutralizing activity against original species B members. Furthermore, immunization with a mix of HAdV-3, 7, and 55 knob proteins protected Chinese tree shrews against an experimental HAdV challenge. Our results provide insight into the immunogenicity of HAdV species B knob proteins.IMPORTANCEHuman adenovirus (HAdV) species B are common pathogens causing severe pneumonia in children, and there is currently no vaccine available. Because there are many HAdV species B types, developing broad-spectrum vaccines against HAdV species B is an important research goal. Our study revealed that immunization with recombinant HAdV species B knob proteins effectively elicited cross-neutralizing antibody responses against original species B members with protective immunity. This study provides a novel insight into the immunogenicity of HAdV species B knob proteins.

Multi-Component Protein Vaccine Induces a Strong and Long-Term Immune Response Against Monkeypox Virus.

Since 2022, outbreaks of monkeypox have raised widespread concern and have been declared a public health emergency of international concern by the World Health Organization. There is an urgent need to develop a safe and effective vaccine against the monkeypox virus (MPXV). Recombinant protein vaccines play a significant role in the prevention of infectious diseases due to their high safety and efficacy. We used the A29, E8, M1, A35, and B6 proteins of MPXV as candidate antigens to generate a panel of multi-component MPXV vaccine candidates, which were administered subcutaneously to immunize mice. The results showed that the vaccine candidates Mix-AEM, Mix-AEMA, Mix-AEMB, and Mix-AEMAB effectively elicited strong neutralizing antibody responses and demonstrated significant protection against vaccinia virus (VACV) infection in a murine model. The vaccine candidate Mix-AEM induced significantly higher levels of neutralizing antibodies, cellular immunity capacity, and virus clearance compared to the vaccine candidate Mix-AE (lacking M1). Single-component immunization showed that M1 induced higher levels of neutralizing antibodies than A29 and E8. These results indicated that M1 is a critical and essential antigen in the MPXV vaccine. The number of cells secreting IFN-γ was significantly increased in the Mix-AEMA and Mix-AEMAB groups compared to the A35-deficient vaccine candidates, demonstrating the important role of A35 in inducing IFN-γ secreting. In addition, the neutralizing antibodies induced by these multi-component vaccine candidates were maintained at high levels six months after the third immunization. In summary, this study lays the groundwork for combining antigens to develop multi-component subunit vaccines.

Discovery and engineering of the antibody response to a prominent skin commensal.

The ubiquitous skin colonist Staphylococcus epidermidis elicits a CD8+ T cell response pre-emptively, in the absence of an infection1. However, the scope and purpose of this anti-commensal immune program are not well defined, limiting our ability to harness it therapeutically. Here, we show that this colonist also induces a potent, durable, and specific antibody response that is conserved in humans and non-human primates. A series of S. epidermidis cell-wall mutants revealed that the cell surface protein Aap is a predominant target. By colonizing mice with a strain of S. epidermidis in which the parallel β-helix domain of Aap is replaced by tetanus toxin fragment C, we elicit a potent neutralizing antibody response that protects mice against a lethal challenge. A similar strain of S. epidermidis expressing an Aap-SpyCatcher chimera can be conjugated with recombinant immunogens; the resulting labeled commensal elicits high antibody titers under conditions of physiologic colonization, including a robust IgA response in the nasal and pulmonary mucosa. Thus, immunity to a common skin colonist involves a coordinated T and B cell response, the latter of which can be redirected against pathogens as a novel form of topical vaccination.

Epitope-focused immunogens targeting the hepatitis C virus glycoproteins induce broadly neutralizing antibodies.

Hepatitis C virus (HCV) infection causes ~290,000 annual human deaths despite the highly effective antiviral treatment available. Several viral immune evasion mechanisms have hampered the development of an effective vaccine against HCV, among them the remarkable conformational flexibility within neutralization epitopes in the HCV antigens. Here, we report the design of epitope-focused immunogens displaying two distinct HCV cross-neutralization epitopes. We show that these immunogens induce a pronounced, broadly neutralizing antibody response in laboratory and transgenic human antibody mice. Monoclonal human antibodies isolated from immunized human antibody mice specifically recognized the grafted epitopes and neutralized four diverse HCV strains. Our results highlight a promising strategy for developing HCV immunogens and provide an encouraging paradigm for targeting structurally flexible epitopes to improve the induction of neutralizing antibodies.