Correlates of protection induced by vaccination

Glycan heterogeneity as a cause of the persistent fraction in HIV-1 neutralization

Neutralizing antibodies (NAbs) to multiple epitopes on the HIV-1-envelope glycoprotein (Env) have been isolated from infected persons. The potency of NAbs is measured more often than the size of the persistent fraction of infectivity at maximum neutralization, which may also influence preventive efficacy of active or passive immunization and the therapeutic outcome of the latter. Many NAbs neutralize HIV-1 CZA97.012, a clone of a Clade-C isolate, to ~100%. But here NAb PGT151, directed to a fusion-peptide epitope, left a persistent fraction of 15%. NAb PGT145, ligating the Env-trimer apex, left no detectable persistent fraction. The divergence in persistent fractions was further analyzed by depletion of pseudoviral populations of the most PGT151- and PGT145-reactive virions. Thereby, neutralization by the non-depleting NAb increased, whereas neutralization by the depleting NAb decreased. Furthermore, depletion by PGT151 increased sensitivity to autologous neutralization by sera from rabbits immunized with soluble native-like CZA97.012 trimer: substantial persistent fractions were reduced. NAbs in these sera target epitopes comprising residue D411 at the V4-β19 transition in a defect of the glycan shield on CZA97.012 Env. NAb binding to affinity-fractionated soluble native-like CZA97.012 trimer differed commensurately with neutralization in analyses by ELISA and surface plasmon resonance. Glycan differences between PGT151- and PGT145-purified trimer fractions were then demonstrated by mass spectrometry, providing one explanation for the differential antigenicity. These differences were interpreted in relation to a new structure at 3.4-Å resolution of the soluble CZA97.012 trimer determined by cryo-electron microscopy. The trimer adopted a closed conformation, refuting apex opening as the cause of reduced PGT145 binding to the PGT151-purified form. The evidence suggests that differences in binding and neutralization after trimer purification or pseudovirus depletion with PGT145 or PGT151 are caused by variation in glycosylation, and that some glycan variants affect antigenicity through direct effects on antibody contacts, whereas others act allosterically.

Nanovaccines to Combat Aeromonas hydrophila Infections in Warm-Water Aquaculture: Opportunities and Challenges

The application of nanotechnology in aquaculture for developing efficient vaccines has shown great potential in recent years. Nanovaccination, which involves encapsulating antigens of fish pathogens in various polymeric materials and nanoparticles, can afford protection to the antigens and a sustained release of the molecule. Oral administration of nanoparticles would be a convenient and cost-effective method for delivering vaccines in aquaculture while eliminating the need for stressful, labour-intensive injectables. The small size of nanoparticles allows them to overcome the degradative digestive enzymes and help deliver antigens to the target site of the fish more effectively. This targeted-delivery approach would help trigger cellular and humoral immune responses more efficiently, thereby enhancing the protective efficacy of vaccines. This is particularly relevant for combating diseases caused by pathogens like Aeromonas hydrophila, a major fish pathogen responsible for significant morbidity and mortality in the aquaculture sector. While the use of nanoparticle-based vaccines in aquaculture has shown promise, concerns exist about the potential toxicity associated with certain types of nanoparticles. Some nanoparticles have been found to exhibit varying degrees of toxicity, and their safety profiles need to be thoroughly assessed before widespread application. The introduction of nanovaccines has opened new vistas for improving aquaculture healthcare, but must be evaluated for potential toxicity before aquaculture applications. Details of nanovaccines and their mode of action, with a focus on protecting fish from infections and outbreaks caused by the ubiquitous opportunistic pathogen A. hydrophila, are reviewed here.

Clinical Course, Immunogenicity, and Efficacy of BNT162b2 mRNA Vaccination Against SARS-CoV-2 Infection in Liver Transplant Recipients

Background

Immunocompromised individuals have been excluded from landmark studies of messenger RNA vaccinations for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). In such patients, the response to vaccination may be blunted and may wane more quickly compared with immunocompetent patients. We studied the factors associated with decreased antibody response to SARS-CoV-2 vaccination and risk factors for subsequent breakthrough infections in liver transplant (LT) patients undergoing coronavirus disease 2019 vaccination with at least 2 doses of messenger RNA vaccine from April 28, 2021, to April 28, 2022.

Methods

All LT recipients received at least 2 doses of the BNT162b2 (Pfizer BioNTech) vaccine 21 d apart. We measured the antibody response against the SARS-CoV-2 spike protein using the Roche Elecsys immunoassay to the receptor-binding domain of the SARS-CoV-2 spike protein, and the presence of neutralizing antibodies was measured by the surrogate virus neutralization test (cPass) before first and second doses of vaccination and also between 2 and 3 mo after the second dose of vaccination.

Results

Ninety-three LT recipients who received 2 doses of BNT162b2 were included in the analysis. The mean time from LT was 110 ± 154 mo. After 2-dose vaccination, 38.7% of LT recipients (36/93) were vaccine nonresponders on the cPass assay compared with 20.4% (19/93) on the Roche S assay. On multivariable analysis, increased age and increased tacrolimus trough were found to be associated with poor neutralizing antibody response (P = 0.038 and 0.022, respectively). The use of antimetabolite therapy in conjunction with tacrolimus approached statistical significance (odds ratio 0.21; 95% confidence interval, 0.180-3.72; P = 0.062). Breakthrough infection occurred in 18 of 88 LT recipients (20.4%). Female gender was independently associated with breakthrough infections (P < 0.001).

Conclusions

Among LT recipients, older age and higher tacrolimus trough levels were associated with poorer immune response to 2-dose SARS-CoV-2 vaccination. Further studies are needed to assess variables associated with breakthrough infections and, hence, who should be prioritized for booster vaccination.

Correlation between pseudotyped virus and authentic virus neutralisation assays, a systematic review and meta-analysis of the literature

Background

The virus neutralization assay is a principal method to assess the efficacy of antibodies in blocking viral entry. Due to biosafety handling requirements of viruses classified as hazard group 3 or 4, pseudotyped viruses can be used as a safer alternative. However, it is often queried how well the results derived from pseudotyped viruses correlate with authentic virus. This systematic review and meta-analysis was designed to comprehensively evaluate the correlation between the two assays.

Methods

Using PubMed and Google Scholar, reports that incorporated neutralisation assays with both pseudotyped virus, authentic virus, and the application of a mathematical formula to assess the relationship between the results, were selected for review. Our searches identified 67 reports, of which 22 underwent a three-level meta-analysis.

Results

The three-level meta-analysis revealed a high level of correlation between pseudotyped viruses and authentic viruses when used in an neutralisation assay. Reports that were not included in the meta-analysis also showed a high degree of correlation, with the exception of lentiviral-based pseudotyped Ebola viruses.

Conclusion

Pseudotyped viruses identified in this report can be used as a surrogate for authentic virus, though care must be taken in considering which pseudotype core to use when generating new uncharacterised pseudotyped viruses.

Serum concentration of antigen-specific IgG can substantially bias interpretation of antibody-dependent phagocytosis assay readout

Because virus neutralization cannot solely explain vaccine-induced, antibody-mediated protection, antibody effector functions are being considered as a potential correlate of protection (CoP). However, measuring effector functions at a fixed serum dilution for high throughput purposes makes it difficult to distinguish between the effect of serum antibody concentration and antibody properties such as epitopes, subclass, and glycosylation. To address this issue, we evaluated antibody-dependent cellular phagocytosis (ADCP) assay against SARS-CoV-2 spike. Adjustment of serum samples to the same concentration of antigen-specific IgG prior to the ADCP assay revealed concentration-independent differences in ADCP after mRNA vaccination in subjects with and without prior SARS-CoV-2 infection not detectable in assay performed with fixed serum dilution. Phagocytosis measured at different concentrations of spike-specific IgG strongly correlated with the area under the curve (AUC) indicating that ADCP assay can be performed at a standardized antibody concentration for the high throughput necessary for vaccine trial analyses.

Application of the SLAPNAP statistical learning tool to broadly neutralizing antibody HIV prevention research

Combination monoclonal broadly neutralizing antibody (bnAb) regimens are in clinical development for HIV prevention, necessitating additional knowledge of bnAb neutralization potency/breadth against circulating viruses. Williamson et al. (2021) described a software tool, Super LeArner Prediction of NAb Panels (SLAPNAP), with application to any HIV bnAb regimen with sufficient neutralization data against a set of viruses in the Los Alamos National Laboratory's Compile, Neutralize, and Tally Nab Panels repository. SLAPNAP produces a proteomic antibody resistance (PAR) score for Env sequences based on predicted neutralization resistance and estimates variable importance of Env amino acid features. We apply SLAPNAP to compare HIV bnAb regimens undergoing clinical testing, finding improved power for downstream sieve analyses and increased precision for comparing neutralization potency/breadth of bnAb regimens due to the inclusion of PAR scores of Env sequences with much larger sample sizes available than for neutralization outcomes. SLAPNAP substantially improves bnAb regimen characterization, ranking, and down-selection.

Computational design of a multi-epitope vaccine candidate against Langya henipavirus using surface proteins

In July 2022, Langya henipavirus (LayV) was identified in febrile patients in China. There is currently no approved vaccine against this virus. Therefore, this research aimed to design a multi-epitope vaccine against LayV using reverse vaccinology. The best epitopes were selected from LayV's fusion protein (F) and glycoprotein (G), and a multi-epitope vaccine was designed using these epitopes, adjuvant, and appropriate linkers. The physicochemical properties, antigenicity, allergenicity, toxicity, and solubility of the vaccine were evaluated. The vaccine's secondary and 3D structures were predicted, and molecular docking and molecular dynamics (MD) simulations were used to assess the vaccine's interaction and stability with toll-like receptor 4 (TLR4). Immune simulation, codon optimization, and in silico cloning of the vaccine were also performed. The vaccine candidate showed good physicochemical properties, as well as being antigenic, non-allergenic, and non-toxic, with acceptable solubility. Molecular docking and MD simulation revealed that the vaccine and TLR4 have stable interactions. Furthermore, immunological simulation of the vaccine indicated its ability to elicit immune responses against LayV. The vaccine's increased expression was also ensured using codon optimization. This study's findings were encouraging, but in vitro and in vivo tests are needed to confirm the vaccine's protective effect.Communicated by Ramaswamy H. Sarma.

Seroprevalence Study of Conserved Enterotoxigenic Escherichia coli Antigens in Globally Diverse Populations

Enterotoxigenic Escherichia coli (ETEC) are common causes of infectious diarrhea among young children of low-and middle-income countries (LMICs) and travelers to these regions. Despite their significant contributions to the morbidity and mortality associated with childhood and traveler's diarrhea, no licensed vaccines are available. Current vaccine strategies may benefit from the inclusion of additional conserved antigens, which may contribute to broader coverage and enhanced efficacy, given their key roles in facilitating intestinal colonization and effective enterotoxin delivery. EatA and EtpA are widely conserved in diverse populations of ETEC, but their immunogenicity has only been studied in controlled human infection models and a population of children in Bangladesh. Here, we compared serologic responses to EatA, EtpA and heat-labile toxin in populations from endemic regions including Haitian children and subjects residing in Egypt, Cameroon, and Peru to US children and adults where ETEC infections are sporadic. We observed elevated IgG and IgA responses in individuals from endemic regions to each of the antigens studied. In a cohort of Haitian children, we observed increased immune responses following exposure to each of the profiled antigens. These findings reflect the wide distribution of ETEC infections across multiple endemic regions and support further evaluation of EatA and EtpA as candidate ETEC vaccine antigens.

Long-term immunoprotection after live attenuated measles-mumps-rubella booster vaccination in children with juvenile idiopathic arthritis

INTRODUCTION

Vaccines, especially live attenuated vaccines, in children with JIA pose a great challenge due to both potential lower immunogenicity and safety as a result of immunosuppressive treatment. For many years, in the Netherlands, JIA patients receive a measles-mumps-rubella (MMR) booster vaccine at the age of nine years as part of the national immunization program.

OBJECTIVES

To study long-term humoral immunoprotection in a large cohort of JIA patients who received the MMR booster vaccine while being treated with immunomodulatory therapies at the Wilhelmina Children's Hospital in Utrecht, the Netherlands.

METHODS

MMR-specific IgG antibody concentrations in stored serum samples of vaccinated JIA patients were determined with chemiluminescent microparticle immunoassays (CMIA). Samples were analyzed five years after MMR booster vaccination and at last available follow-up visit using both crude and adjusted analyses. Additional clinical data were collected from electronic medical records.

RESULTS

In total, 236 samples from 182 patients were analyzed, including 67 samples that were available five years post-vaccination, and an additional 169 samples available from last visits with a median duration after vaccination of 6.9 years (IQR: 2.8-8.8). Twenty-eight patients were using biologic disease-modifying antirheumatic drugs (bDMARDS) of whom 96% anti-TNF agents and 4% tocilizumab. Percentages of protective antibody levels against measles after five years were significantly lower for patients who used bDMARD therapy at vaccination compared to patients who did not: 60% versus 86% (P = 0.03). For mumps (80% versus 94%) and rubella (60% versus 83%) this difference did not reach statistical significance (P = 0.11 and P = 0.07, respectively). Antibody levels post-vaccination decreased over time, albeit not significantly different between bDMARD users and non-bDMARD users.

CONCLUSION

The MMR booster vaccine demonstrated long-term immunogenicity in the majority of children with JIA from a large cohort, although lower percentages of protective measles antibody levels were observed in bDMARD users. Hence, it might be indicated to measure antibody levels at least five years after MMR booster vaccination in the latter group and advice an extra booster accordingly.

Emerging vaccine strategies against the incessant pneumococcal disease

The incidence of invasive pneumococcal disease (IPD) caused by infection with the pathogen Streptococcus pneumoniae (Spn) has been on a downward trend for decades due to worldwide vaccination programs. Despite the clinical successes observed, the Center for Disease Control (CDC) reports that the continued global burden of S. pneumoniae will be in the millions each year, with a case-fatality rate hovering around 5%. Thus, it is a top priority to continue developing new Spn vaccination strategies to harness immunological insight and increase the magnitude of protection provided. As emphasized by the World Health Organization (WHO), it is also crucial to broaden the implementation of vaccines that are already obtainable in the clinical setting. This review focuses on the immune mechanisms triggered by existing pneumococcal vaccines and provides an overview of the current and upcoming clinical strategies being employed. We highlight the associated challenges of serotype selectivity and using pneumococcal-derived proteins as alternative vaccine antigens.

A Multicenter, Controlled Human Infection Study of Influenza A(H1N1)pdm09 in Healthy Adults

BACKGROUND

We evaluated the associations between baseline influenza virus-specific hemagglutination inhibition (HAI) and microneutralization (MN) titers and subsequent symptomatic influenza virus infection in a controlled human infection study.

METHODS

We inoculated unvaccinated healthy adults aged 18-49 years with an influenza A/California/04/2009/H1N1pdm-like virus (NCT04044352). We collected serial safety labs, serum for HAI and MN, and nasopharyngeal swabs for reverse-transcription polymerase chain reaction (RT-PCR) testing. Analyses used the putative seroprotective titer of ≥40 for HAI and MN. The primary clinical outcome was mild-to-moderate influenza disease (MMID), defined as ≥1 postchallenge positive qualitative RT-PCR test with a qualifying symptom/clinical finding.

RESULTS

Of 76 participants given influenza virus challenge, 54 (71.1%) experienced MMID. Clinical illness was generally very mild. MMID attack rates among participants with baseline titers ≥40 by HAI and MN were 64.9% and 67.9%, respectively, while MMID attack rates among participants with baseline titers <40 by HAI and MN were 76.9% and 78.3%, respectively. The estimated odds of developing MMID decreased by 19% (odds ratio, 0.81 [95% confidence interval, .62-1.06]; P = .126) for every 2-fold increase in baseline HAI. There were no significant adverse events.

CONCLUSIONS

We achieved a 71.1% attack rate of MMID. High baseline HAI and MN were associated with protection from illness. Clinical Trials Registration. NCT04044352.

Safety and Clinical Benefits of Adacel® and Adacel®-Polio Vaccination in Pregnancy: A Structured Literature Review

Vaccination in pregnancy using a tetanus toxoid, reduced dose diphtheria toxoid, and reduced dose acellular pertussis (Tdap) vaccine is important for prevention of severe pertussis disease in young infants. The objectives of this systematic literature review were to search for original research studies evaluating the vaccine effectiveness, immunogenicity, and safety of Adacel®/Adacel-Polio® used during pregnancy to prevent pertussis disease in young infants. Medical databases used included EMBASE, BIOSIS Previews, and Chemical Abstracts, with search terms related to pregnancy, vaccines/immunization, safety, pertussis, effectiveness/efficacy, and immune response; other potentially eligible reports were included where applicable. Search results were restricted to literature published from 1 January 1995 to 26 July 2021. A total of 2021 articles and 4 other reports were identified for primary review. A total of 49 publications qualified for inclusion after primary and secondary reviews. Effectiveness studies of Adacel or Adacel-Polio given in pregnancy consistently showed high levels of protection from pertussis disease in the newborn (vaccine effectiveness: 91-93%). In immunogenicity studies, the response in pregnant women was consistent with that of non-pregnant women. Infants of mothers vaccinated with Adacel or Adacel-Polio in pregnancy had higher anti-pertussis antibody levels at birth and at 2 months of age compared to infants born to women vaccinated with comparator vaccines, placebo, or those not vaccinated during pregnancy. There was evidence of a slightly decreased response to primary pertussis vaccination in infants of mothers vaccinated with Adacel or Adacel-Polio, but this was not thought to be clinically significant. In safety studies, Adacel or Adacel-Polio vaccination was well tolerated by pregnant woman and not associated with pregnancy, postpartum, or neonatal complications. In conclusion, Adacel or Adacel-Polio vaccination in pregnancy is highly effective in protecting young infants from pertussis disease, with a favorable safety profile for both pregnant women and their infants.

When does humoral memory enhance infection?

Antibodies and humoral memory are key components of the adaptive immune system. We consider and computationally model mechanisms by which humoral memory present at baseline might increase rather than decrease infection load; we refer to this effect as EI-HM (enhancement of infection by humoral memory). We first consider antibody dependent enhancement (ADE) in which antibody enhances the growth of the pathogen, typically a virus, and typically at intermediate 'Goldilocks' levels of antibody. Our ADE model reproduces ADE in vitro and enhancement of infection in vivo from passive antibody transfer. But notably the simplest implementation of our ADE model never results in EI-HM. Adding complexity, by making the cross-reactive antibody much less neutralizing than the de novo generated antibody or by including a sufficiently strong non-antibody immune response, allows for ADE-mediated EI-HM. We next consider the possibility that cross-reactive memory causes EI-HM by crowding out a possibly superior de novo immune response. We show that, even without ADE, EI-HM can occur when the cross-reactive response is both less potent and 'directly' (i.e. independently of infection load) suppressive with regard to the de novo response. In this case adding a non-antibody immune response to our computational model greatly reduces or completely eliminates EI-HM, which suggests that 'crowding out' is unlikely to cause substantial EI-HM. Hence, our results provide examples in which simple models give qualitatively opposite results compared to models with plausible complexity. Our results may be helpful in interpreting and reconciling disparate experimental findings, especially from dengue, and for vaccination.

Correlates of protection for booster doses of the SARS-CoV-2 vaccine BNT162b2

Vaccination, especially with multiple doses, provides substantial population-level protection against COVID-19, but emerging variants of concern (VOC) and waning immunity represent significant risks at the individual level. Here we identify correlates of protection (COP) in a multicenter prospective study following 607 healthy individuals who received three doses of the Pfizer-BNT162b2 vaccine approximately six months prior to enrollment. We compared 242 individuals who received a fourth dose to 365 who did not. Within 90 days of enrollment, 239 individuals contracted COVID-19, 45% of the 3-dose group and 30% of the four-dose group. The fourth dose elicited a significant rise in antibody binding and neutralizing titers against multiple VOCs reducing the risk of symptomatic infection by 37% [95%CI, 15%-54%]. However, a group of individuals, characterized by low baseline titers of binding antibodies, remained susceptible to infection despite significantly increased neutralizing antibody titers upon boosting. A combination of reduced IgG levels to RBD mutants and reduced VOC-recognizing IgA antibodies represented the strongest COP in both the 3-dose group (HR = 6.34, p = 0.008) and four-dose group (HR = 8.14, p = 0.018). We validated our findings in an independent second cohort. In summary combination IgA and IgG baseline binding antibody levels may identify individuals most at risk from future infections.

A Single Oral Immunization with a Replication-Competent Adenovirus-Vectored Vaccine Protects Mice from Influenza Respiratory Infection

The development of effective and flexible vaccine platforms is a major public health challenge, especially in the context of influenza vaccines that have to be renewed every year. Adenoviruses (AdVs) are easy to produce and have a good safety and efficacy profile when administered orally, as demonstrated by the long-term use of oral AdV-4 and -7 vaccines in the U.S. military. These viruses therefore appear to be the ideal backbone for the development of oral replicating vector vaccines. However, research into these vaccines is limited by the ineffectiveness of human AdV replication in laboratory animals. The use of mouse AdV type 1 (MAV-1) in its natural host allows infection to be studied under replicating conditions. Here, we orally vaccinated mice with a MAV-1 vector expressing influenza hemagglutinin (HA) to assess the protection conferred against an intranasal challenge of influenza. We showed that a single oral immunization with this vaccine generates influenza-specific and -neutralizing antibodies and completely protects mice against clinical signs and viral replication, similar to traditional inactivated vaccines. IMPORTANCE Given the constant threat of pandemics and the need for annual vaccination against influenza and possibly emerging agents such as SARS-CoV-2, new types of vaccines that are easier to administer and therefore more widely accepted are a critical public health need. Here, using a relevant animal model, we have shown that replicative oral AdV vaccine vectors can help make vaccination against major respiratory diseases more available, better accepted, and therefore more effective. These results could be of major importance in the coming years in the fight against seasonal or emerging respiratory diseases such as COVID-19.

Potential for Maternally Administered Vaccine for Infant Group B Streptococcus

BACKGROUND

Natural history studies have correlated serotype-specific anti-capsular polysaccharide (CPS) IgG in newborns with a reduced risk of group B streptococcal disease. A hexavalent CPS-cross-reactive material 197 glycoconjugate vaccine (GBS6) is being developed as a maternal vaccine to prevent invasive group B streptococcus in young infants.

METHODS

In an ongoing phase 2, placebo-controlled trial involving pregnant women, we assessed the safety and immunogenicity of a single dose of various GBS6 formulations and analyzed maternally transferred anti-CPS antibodies. In a parallel seroepidemiologic study that was conducted in the same population, we assessed serotype-specific anti-CPS IgG concentrations that were associated with a reduced risk of invasive disease among newborns through 89 days of age to define putative protective thresholds.

RESULTS

Naturally acquired anti-CPS IgG concentrations were associated with a reduced risk of disease among infants in the seroepidemiologic study. IgG thresholds that were determined to be associated with 75 to 95% reductions in the risk of disease were 0.184 to 0.827 μg per milliliter. No GBS6-associated safety signals were observed among the mothers or infants. The incidence of adverse events and of serious adverse events were similar across the trial groups for both mothers and infants; more local reactions were observed in the groups that received GBS6 containing aluminum phosphate. Among the infants, the most common serious adverse events were minor congenital anomalies (umbilical hernia and congenital dermal melanocytosis). GBS6 induced maternal antibody responses to all serotypes, with maternal-to-infant antibody ratios of approximately 0.4 to 1.3, depending on the dose. The percentage of infants with anti-CPS IgG concentrations above 0.184 μg per milliliter varied according to serotype and formulation, with 57 to 97% of the infants having a seroresponse to the most immunogenic formulation.

CONCLUSIONS

GBS6 elicited anti-CPS antibodies against group B streptococcus in pregnant women that were transferred to infants at levels associated with a reduced risk of invasive group B streptococcal disease. (Funded by Pfizer and the Bill and Melinda Gates Foundation; C1091002 ClinicalTrials.gov number, NCT03765073.).

B-cell immunity and vaccine induced antibody protection reveal the inefficacy of current vaccination schedule in infants with perinatal HIV-infection in Mozambique, Africa

BACKGROUND

Despite antiretroviral treatment (ART), immune dysfunction persists in children with perinatal HIV infection (HEI). Here we investigated the impact of HIV status on maternal antibody (Ab) passage, long-term vaccine induced immunity and B-cell maturation.

METHODS

46 HIV Exposed Uninfected (HEU), 43 HEI, and 15 HIV unexposed uninfected (HUU) infants were vaccinated with 3 doses of DTaP-HepB-Hib-PCV10-OP at 2, 3, and 4 months at Matola Provincial Hospital, Maputo, Mozambique. Tetanus toxoid specific (TT) IgG, HIV Ab and B-cell phenotype characteristics were evaluated at entry, pre-ART, 5, 10, and 18 months in this longitudinal cohort study.

FINDINGS

Baseline (maternal) plasma TT Ab levels were significantly lower in HEI compared to both HEU and HUU and a faster decay of TT Ab was observed in HEI compared to HEU with significantly lower TT Ab levels at 10 and 18 months of age. TT unprotected (UP) (≤0.1 IU/mL) HEI showed higher HIV-RNA at entry and higher longitudinal HIV viremia (Area Under the Curve) compared to TT protected (P) HEI. A distinct HIV-Ab profile was found at entry in HEI compared to HEU. B-cell phenotype showed a B-cell perturbation in HEI vs HEU infants at entry (mean age 40.8 days) with lower transitional CD10+CD19+ B-cells and IgD+CD27- naive B-cells and an overall higher frequency of IgD-CD27- double negative B-cell subsets in HEI.

INTERPRETATION

B-cell perturbation, presenting with higher double negative IgD-CD27- B-cells was observed in neonatal age and may play a major role in the B-cell exhaustion in HEI. The ability to maintain TT protective Ab titers over time is impaired in HEI with uncontrolled viral replication and the current vaccination schedule is insufficient to provide long-term protection against tetanus.

FUNDING

This work was supported by: NIH grant to SP (5R01AI127347-05); Children's Hospital Bambino Gesú (Ricerca corrente 2019) to NC, and Associazione Volontari Bambino Gesù to PP.

Immunoglobulin repertoire restriction characterizes the serological responses of patients with predominantly antibody deficiency

BACKGROUND

Predominantly antibody deficiency (PAD) is the most common category of inborn errors of immunity and is underpinned by impaired generation of appropriate antibody diversity and quantity. In the clinic, responses are interrogated by assessment of vaccination responses, which is central to many PAD diagnoses. However, the composition of the generated antibody repertoire is concealed from traditional quantitative measures of serological responses. Leveraging modern mass spectrometry-based proteomics (MS-proteomics), it is possible to elaborate the molecular features of specific antibody repertoires, which may address current limitations of diagnostic vaccinology.

OBJECTIVES

We sought to evaluate serum antibody responses in patients with PAD following vaccination with a neo-antigen (severe acute respiratory syndrome coronavirus-2 vaccination) using MS-proteomics.

METHODS

Following severe acute respiratory syndrome coronavirus-2 vaccination, serological responses in individuals with PAD and healthy controls (HCs) were assessed by anti-S1 subunit ELISA and neutralization assays. Purified anti-S1 subunit IgG and IgM was profiled by MS-proteomics for IGHV subfamily usage and somatic hypermutation analysis.

RESULTS

Twelve patients with PAD who were vaccine-responsive were recruited with 11 matched vaccinated HCs. Neutralization and end point anti-S1 titers were lower in PAD. All subjects with PAD demonstrated restricted anti-S1 IgG antibody repertoires, with usage of <5 IGHV subfamilies (median: 3; range 2-4), compared to ≥5 for the 11 HC subjects (P < .001). IGHV3-7 utilization was far less common in patients with PAD than in HCs (2 of 12 vs 10 of 11; P = .001). Amino acid substitutions due to somatic hypermutation per subfamily did not differ between groups. Anti-S1 IgM was present in 64% and 50% of HC and PAD cohorts, respectively, and did not differ significantly between HCs and patients with PAD.

CONCLUSIONS

This study demonstrates the breadth of anti-S1 antibodies elicited by vaccination at the proteome level and identifies stereotypical restriction of IGHV utilization in the IgG repertoire in patients with PAD compared with HC subjects. Despite uniformly pauci-clonal antibody repertoires some patients with PAD generated potent serological responses, highlighting a possible limitation of traditional serological techniques. These findings suggest that IgG repertoire restriction is a key feature of antibody repertoires in PAD.

ECTRIMS/EAN consensus on vaccination in people with multiple sclerosis: Improving immunization strategies in the era of highly active immunotherapeutic drugs

BACKGROUND

With the new highly active drugs available for people with multiple sclerosis (pwMS), vaccination becomes an essential part of the risk management strategy.

OBJECTIVE

To develop a European evidence-based consensus for the vaccination strategy of pwMS who are candidates for disease-modifying therapies (DMTs).

METHODS

This work was conducted by a multidisciplinary working group using formal consensus methodology. Clinical questions (defined as population, interventions, and outcomes) considered all authorized DMTs and vaccines. A systematic literature search was conducted and quality of evidence was defined according to the Oxford Centre for Evidence-Based Medicine Levels of Evidence. The recommendations were formulated based on the quality of evidence and the risk-benefit balance.

RESULTS

Seven questions, encompassing vaccine safety, vaccine effectiveness, global vaccination strategy and vaccination in sub-populations (pediatric, pregnant women, elderly and international travelers) were considered. A narrative description of the evidence considering published studies, guidelines, and position statements is presented. A total of 53 recommendations were agreed by the working group after three rounds of consensus.

CONCLUSION

This first European consensus on vaccination in pwMS proposes the best vaccination strategy according to current evidence and expert knowledge, with the goal of homogenizing the immunization practices in pwMS.

Risk of COVID-19 in people with multiple sclerosis who are seronegative following vaccination

BACKGROUND

People with multiple sclerosis (pwMS) treated with certain disease-modifying therapies (DMTs) have attenuated IgG response following COVID-19 vaccination; however, the clinical consequences remain unclear.

OBJECTIVE

To report COVID-19 rates in pwMS according to vaccine serology.

METHODS

PwMS with available (1) serology 2-12 weeks following COVID-19 vaccine 2 and/or vaccine 3 and (2) clinical data on COVID-19 infection/hospitalisation were included. Logistic regression was performed to examine whether seroconversion following vaccination predicted risk of subsequent COVID-19 infection after adjusting for potential confounders. Rates of severe COVID-19 (requiring hospitalisation) were also calculated.

RESULTS

A total of 647 pwMS were included (mean age 48 years, 500 (77%) female, median Expanded Disability Status Scale (EDSS) 3.5% and 524 (81%) exposed to DMT at the time of vaccine 1). Overall, 472 out of 588 (73%) were seropositive after vaccines 1 and 2 and 222 out of 305 (73%) after vaccine 3. Seronegative status after vaccine 2 was associated with significantly higher odds of subsequent COVID-19 infection (odds ratio (OR): 2.35, 95% confidence interval (CI): 1.34-4.12, p = 0.0029), whereas seronegative status after vaccine 3 was not (OR: 1.05, 95% CI: 0.57-1.91). Five people (0.8%) experienced severe COVID-19, all of whom were seronegative after most recent vaccination.

CONCLUSION

Attenuated humoral response to initial COVID-19 vaccination predicts increased risk of COVID-19 in pwMS, but overall low rates of severe COVID-19 were seen.

Polyfunctional antibodies: a path towards precision vaccines for vulnerable populations

Vaccine efficacy determined within the controlled environment of a clinical trial is usually substantially greater than real-world vaccine effectiveness. Typically, this results from reduced protection of immunologically vulnerable populations, such as children, elderly individuals and people with chronic comorbidities. Consequently, these high-risk groups are frequently recommended tailored immunisation schedules to boost responses. In addition, diverse groups of healthy adults may also be variably protected by the same vaccine regimen. Current population-based vaccination strategies that consider basic clinical parameters offer a glimpse into what may be achievable if more nuanced aspects of the immune response are considered in vaccine design. To date, vaccine development has been largely empirical. However, next-generation approaches require more rational strategies. We foresee a generation of precision vaccines that consider the mechanistic basis of vaccine response variations associated with both immunogenetic and baseline health differences. Recent efforts have highlighted the importance of balanced and diverse extra-neutralising antibody functions for vaccine-induced protection. However, in immunologically vulnerable populations, significant modulation of polyfunctional antibody responses that mediate both neutralisation and effector functions has been observed. Here, we review the current understanding of key genetic and inflammatory modulators of antibody polyfunctionality that affect vaccination outcomes and consider how this knowledge may be harnessed to tailor vaccine design for improved public health.

Delaying the third dose of Japanese aluminum-free hepatitis A vaccine Aimmugen elicits effective immune responses against hepatitis A in adults

Inactivated aluminum-adsorbed hepatitis A vaccines such as Havrix, Vaqta, and Avaxim are commonly used worldwide. These vaccines are typically administered in a two-dose series (at 0 and 6-12 months). However, a lyophilized inactivated aluminum-free hepatitis A vaccine, Aimmugen, which is approved in Japan, is typically administered in a three-dose series (at 0, 2-4, and 24 weeks). Hence, individuals visiting endemic hepatitis A areas receive the primary two doses of Aimmugen before traveling and the third booster dose much later. It is currently uncertain whether boosting with a delayed third dose of Aimmugen is effective, or whether a new vaccination schedule should instead be initiated. Therefore, we investigated the anti-hepatitis-A viral immune response of adult travelers who received the third dose of Aimmugen more than 24 weeks after the first dose. Participants were vaccinated with the third dose of Aimmugen more than 2 years after the first two doses. Antibody titers were measured at Day 0 (prevaccination) and at 28-42 days after the third dose of Aimmugen. Twenty-nine adult participants were enrolled in the study (14 men and 15 women; mean age ± standard deviation age, 36.2 ± 8.1 years). The interval between the first two doses and the third dose was 3-14 years. The seroprotection rate (i.e., the percentage of participants with anti-hepatitis A virus antibody titers ≥ 10 mIU/mL) was 96.6 % (28/29) at Day 0 and increased to 100 % (29/29) at Days 28-42. Geometric mean concentration increased from 105 to 4,013 mIU/mL. We demonstrated that delaying the third dose of Aimmugen still elicited effective immune responses after priming with two doses of the vaccine. Trial registration: UMIN Clinical Trials Registry (UMIN-CTR): MIN000013624. Registered 03 April 2014. https://center6.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000015906.

Impact of pregnancy on polyfunctional IgG and memory B cell responses to Tdap immunization

BACKGROUND

Maternal pertussis immunization using Tdap vaccine is recommended in many countries to protect newborns from severe post-natal infection. Immunological changes during pregnancy may influence the response to vaccines. The quality of IgG and memory B cell responses to Tdap immunization in pregnant women has not yet been described.

METHODS

The impact of pregnancy on the response to Tdap vaccination was assessed by comparing humoral immune responses in 42 pregnant and 39 non-pregnant women. The levels of serum pertussis antigens and tetanus toxoid-specific IgG, IgG subclasses, IgG Fc-mediated effector functions, as well as memory B cell frequencies were assessed before and at several time points after vaccination.

RESULTS

Tdap immunization induced similar levels of pertussis and tetanus-specific IgG and IgG subclasses in pregnant and non-pregnant women. Pregnant women produced IgG promoting complement deposition, and neutrophils and macrophages phagocytosis at levels comparable to non-pregnant women. They were also able to expand pertussis and tetanus-specific memory B cells at similar frequencies as non-pregnant women, suggesting equivalent "boostability". Higher levels of vaccine-specific IgG, IgG subclasses, and IgG Fc-mediated effector functions were detected in cord blood as compared to maternal blood, indicating efficient transport across the placenta.

CONCLUSIONS

This study demonstrates that pregnancy does not affect the quality of effector IgG and memory B cell responses to Tdap immunization and that polyfunctional IgG are efficiently transferred across the placenta.

REGISTRY'S URL AND THE TRIAL'S REGISTRATION NUMBER

ClinicalTrials.Gov (NCT03519373).

Intranasal immunization with outer membrane vesicles (OMV) protects against airway colonization and systemic infection with Acinetobacter baumannii

OBJECTIVES

The multidrug-resistant bacteria Acinetobacter baumannii is a major cause of hospital-associated infection; a vaccine could significantly reduce this burden. The aim was to develop a clinically relevant model of A. baumannii respiratory tract infection and to test the impact of different immunization routes on protective immunity provided by an outer membrane vesicle (OMV) vaccine.

METHODS

BALB/c mice were intranasally challenged with isolates of oxa23-positive global clone GC2 A. baumannii from the lungs of patients with ventilator-associated pneumonia. Mice were immunized with OMVs by the intramuscular, subcutaneous or intranasal routes; protection was determined by measuring local and systemic bacterial load.

RESULTS

Infection with A. baumannii clinical isolates led to a more disseminated infection than the prototype A. baumannii strain ATCC17978; with bacteria detectable in upper and lower airways and the spleen. Intramuscular immunization induced an antibody response but did not protect against bacterial infection. However, intranasal immunization significantly reduced airway colonization and prevented systemic bacterial dissemination.

CONCLUSIONS

Use of clinically relevant isolates of A. baumannii provides stringent model for vaccine development. Intranasal immunization with OMVs was an effective route for providing protection, demonstrating that local immunity is important in preventing A. baumannii infection.

Conformational antigenic heterogeneity as a cause of the persistent fraction in HIV-1 neutralization

BACKGROUND

Neutralizing antibodies (NAbs) protect against HIV-1 acquisition in animal models and show promise in treatment of infection. They act by binding to the viral envelope glycoprotein (Env), thereby blocking its receptor interactions and fusogenic function. The potency of neutralization is largely determined by affinity. Less well explained is the persistent fraction, the plateau of remaining infectivity at the highest antibody concentrations.

RESULTS

We observed different persistent fractions for neutralization of pseudovirus derived from two Tier-2 isolates of HIV-1, BG505 (Clade A) and B41 (Clade B): it was pronounced for B41 but not BG505 neutralization by NAb PGT151, directed to the interface between the outer and transmembrane subunits of Env, and negligible for either virus by NAb PGT145 to an apical epitope. Autologous neutralization by poly- and monoclonal NAbs from rabbits immunized with soluble native-like B41 trimer also left substantial persistent fractions. These NAbs largely target a cluster of epitopes lining a hole in the dense glycan shield of Env around residue 289. We partially depleted B41-virion populations by incubating them with PGT145- or PGT151-conjugated beads. Each depletion reduced the sensitivity to the depleting NAb and enhanced it to the other. Autologous neutralization by the rabbit NAbs was decreased for PGT145-depleted and enhanced for PGT151-depleted B41 pseudovirus. Those changes in sensitivity encompassed both potency and the persistent fraction. We then compared soluble native-like BG505 and B41 Env trimers affinity-purified by each of three NAbs: 2G12, PGT145, or PGT151. Surface plasmon resonance showed differences among the fractions in antigenicity, including kinetics and stoichiometry, congruently with the differential neutralization. The large persistent fraction after PGT151 neutralization of B41 was attributable to low stoichiometry, which we explained structurally by clashes that the conformational plasticity of B41 Env causes.

CONCLUSION

Distinct antigenic forms even of clonal HIV-1 Env, detectable among soluble native-like trimer molecules, are distributed over virions and may profoundly mold neutralization of certain isolates by certain NAbs. Affinity purifications with some antibodies may yield immunogens that preferentially expose epitopes for broadly active NAbs, shielding less cross-reactive ones. NAbs reactive with multiple conformers will together reduce the persistent fraction after passive and active immunization.

Bridging the immunogenicity of a tetravalent dengue vaccine (TAK-003) from children and adolescents to adults

Immunobridging is an important methodology that can be used to extrapolate vaccine efficacy estimates to populations not evaluated in clinical studies, and that has been successfully used in developing many vaccines. Dengue, caused by a mosquito-transmitted flavivirus endemic to many tropical and subtropical regions, is traditionally thought of as a pediatric disease but is now a global threat to both children and adults. We bridged immunogenicity data from a phase 3 efficacy study of a tetravalent dengue vaccine (TAK-003), performed in children and adolescents living in endemic areas, with an immunogenicity study in adults in non-endemic areas. Neutralizing antibody responses were comparable in both studies following receipt of a two-dose TAK-003 schedule (months 0 and 3). Similar immune responses were observed across exploratory assessments of additional humoral responses. These data support the potential for clinical efficacy of TAK-003 in adults.

Impact of aging on immunity in the context of COVID-19, HIV, and tuberculosis

Knowledge of aging biology needs to be expanded due to the continuously growing number of elderly people worldwide. Aging induces changes that affect all systems of the body. The risk of cardiovascular disease and cancer increases with age. In particular, the age-induced adaptation of the immune system causes a greater susceptibility to infections and contributes to the inability to control pathogen growth and immune-mediated tissue damage. Since the impact of aging on immune function, is still to be fully elucidated, this review addresses some of the recent understanding of age-related changes affecting key components of immunity. The emphasis is on immunosenescence and inflammaging that are impacted by common infectious diseases that are characterized by a high mortality, and includes COVID-19, HIV and tuberculosis.

Vaccine Preventable Disease Seroprevalence in a Nationwide Assessment of Timor-Leste (VASINA-TL): study protocol for a population-representative cross-sectional serosurvey

INTRODUCTION

Historic disruption in health infrastructure combined with data from a recent vaccine coverage survey suggests there are likely significant immunity gaps to vaccine preventable diseases and high risk of outbreaks in Timor-Leste. Community-based serological surveillance is an important tool to augment understanding of population-level immunity achieved through vaccine coverage and/or derived from prior infection.

METHODS AND ANALYSIS

This national population-representative serosurvey will take a three-stage cluster sample and aims to include 5600 individuals above 1 year of age. Serum samples will be collected by phlebotomy and analysed for measles IgG, rubella IgG, SARS-CoV-2 antispike protein IgG, hepatitis B surface antibody and hepatitis B core antigen using commercially available chemiluminescent immunoassays or ELISA. In addition to crude prevalence estimates and to account for differences in Timor-Leste's age structure, stratified age-standardised prevalence estimates will be calculated, using Asia in 2013 as the standard population. Additionally, this survey will derive a national asset of serum and dried blood spot samples which can be used for further investigation of infectious disease seroepidemiology and/or validation of existing and novel serological assays for infectious diseases.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Research Ethics and Technical Committee of the Instituto Nacional da Saúde, Timor-Leste and the Human Research Ethics Committee of the Northern Territory Department of Health and Menzies School of Health Research, Australia. Co-designing this study with Timor-Leste's Ministry-of-Health and other relevant partner organisations will allow immediate translation of findings into public health policy, which may include changes to routine immunisation service delivery and/or plans for supplementary immunisation activities.

Role of nanotechnology in the prolonged release of drugs by the subcutaneous route

INTRODUCTION

Subcutaneous physiology is distinct from other parenteral routes that benefit the administration of prolonged-release formulations. A prolonged-release effect is particularly convenient for treating chronic diseases because it is associated with complex and often prolonged posologies. Therefore, drug-delivery systems focused on nanotechnology are proposed as alternatives that can overcome the limitations of current therapeutic regimens and improve therapeutic efficacy.

AREAS COVERED

This review presents an updated systematization of nanosystems, focusing on their applications in highly prevalent chronic diseases. Subcutaneous-delivered nanosystem-based therapies comprehensively summarize nanosystems, drugs, and diseases and their advantages, limitations, and strategies to increase their translation into clinical applications. An outline of the potential contribution of quality-by-design (QbD) and artificial intelligence (AI) to the pharmaceutical development of nanosystems is presented.

EXPERT OPINION

Although recent academic research and development (R&D) advances in the subcutaneous delivery of nanosystems have exhibited promising results, pharmaceutical industries and regulatory agencies need to catch up. The lack of standardized methodologies for analyzing in vitro data from nanosystems for subcutaneous administration and subsequent in vivo correlation limits their access to clinical trials. There is an urgent need for regulatory agencies to develop methods that faithfully mimic subcutaneous administration and specific guidelines for evaluating nanosystems.

Evaluation of Cellular Immune Response to Adeno-Associated Virus-Based Gene Therapy

The number of approved or investigational late phase viral vector gene therapies (GTx) has been rapidly growing. The adeno-associated virus vector (AAV) technology continues to be the most used GTx platform of choice. The presence of pre-existing anti-AAV immunity has been firmly established and is broadly viewed as a potential deterrent for successful AAV transduction with a possibility of negative impact on clinical efficacy and a connection to adverse events. Recommendations for the evaluation of humoral, including neutralizing and total antibody based, anti-AAV immune response have been presented elsewhere. This manuscript aims to cover considerations related to the assessment of anti-AAV cellular immune response, including review of correlations between humoral and cellular responses, potential value of cellular immunogenicity assessment, and commonly used analytical methodologies and parameters critical for monitoring assay performance. This manuscript was authored by a group of scientists involved in GTx development who represent several pharma and contract research organizations. It is our intent to provide recommendations and guidance to the industry sponsors, academic laboratories, and regulatory agencies working on AAV-based GTx viral vector modalities with the goal of achieving a more consistent approach to anti-AAV cellular immune response assessment.

Second monovalent SARS-CoV-2 mRNA booster restores Omicron-specific neutralizing activity in both nursing home residents and health care workers

We examined whether the second monovalent SARS-CoV-2 mRNA booster increased antibody levels and their neutralizing activity to Omicron variants in nursing home residents (NH) residents and healthcare workers (HCW). We sampled 376 NH residents and 63 HCW after primary mRNA vaccination, first and second boosters, for antibody response and pseudovirus neutralization assay against SARS-CoV-2 wild-type (WT) (Wuhan-Hu-1) strain, Omicron BA.1 and BA.5 variants. Antibody levels and neutralizing activity progressively increased with each booster but subsequently waned over 3-6 months. NH residents, both those without and with prior infection, had a robust geometric mean fold rise (GMFR) of 8.1 (95% CI 4.4, 14.8) and 7.8 (95% CI 4.8, 12.9) respectively in Omicron-BA.1 subvariant specific neutralizing antibody levels following the second booster vaccination (p < 0.001). These results support the ongoing efforts to ensure that both NH residents and HCW are up-to-date on recommended SARS-CoV-2 vaccine booster doses.

Cholera toxin B scaffolded, focused SIV V2 epitope elicits antibodies that influence the risk of SIVmac251 acquisition in macaques

Introduction

An efficacious HIV vaccine will need to elicit a complex package of innate, humoral, and cellular immune responses. This complex package of responses to vaccine candidates has been studied and yielded important results, yet it has been a recurring challenge to determine the magnitude and protective effect of specific in vivo immune responses in isolation. We therefore designed a single, viral-spike-apical, epitope-focused V2 loop immunogen to reveal individual vaccine-elicited immune factors that contribute to protection against HIV/SIV.

Method

We generated a novel vaccine by incorporating the V2 loop B-cell epitope in the cholera toxin B (CTB) scaffold and compared two new immunization regimens to a historically protective 'standard' vaccine regimen (SVR) consisting of 2xDNA prime boosted with 2xALVAC-SIV and 1xΔV1gp120. We immunized a cohort of macaques with 5xCTB-V2c vaccine+alum intramuscularly simultaneously with topical intrarectal vaccination of CTB-V2c vaccine without alum (5xCTB-V2/alum). In a second group, we tested a modified version of the SVR consisting of 2xDNA prime and boosted with 1xALVAC-SIV and 2xALVAC-SIV+CTB-V2/alum, (DA/CTB-V2c/alum).

Results

In the absence of any other anti-viral antibodies, V2c epitope was highly immunogenic when incorporated in the CTB scaffold and generated highly functional anti-V2c antibodies in the vaccinated animals. 5xCTB-V2c/alum vaccination mediated non-neutralizing ADCC activity and efferocytosis, but produced low avidity, trogocytosis, and no neutralization of tier 1 virus. Furthermore, DA/CTB-V2c/alum vaccination also generated lower total ADCC activity, avidity, and neutralization compared to the SVR. These data suggest that the ΔV1gp120 boost in the SVR yielded more favorable immune responses than its CTB-V2c counterpart. Vaccination with the SVR generates CCR5- α4β7+CD4+ Th1, Th2, and Th17 cells, which are less likely to be infected by SIV/HIV and likely contributed to the protection afforded in this regimen. The 5xCTB-V2c/alum regimen likewise elicited higher circulating CCR5- α4β7+ CD4+ T cells and mucosal α4β7+ CD4+ T cells compared to the DA/CTB-V2c/alum regimen, whereas the first cell type was associated with reduced risk of viral acquisition.

Conclusion

Taken together, these data suggest that individual viral spike B-cell epitopes can be highly immunogenic and functional as isolated immunogens, although they might not be sufficient on their own to provide full protection against HIV/SIV infection.

Comparing antibody assays as correlates of protection against COVID-19 in the COVE mRNA-1273 vaccine efficacy trial

The best assay or marker to define mRNA-1273 vaccine-induced antibodies as a correlate of protection (CoP) is unclear. In the COVE trial, participants received two doses of the mRNA-1273 COVID-19 vaccine or placebo. We previously assessed IgG binding antibodies to the spike protein (spike IgG) or receptor binding domain (RBD IgG) and pseudovirus neutralizing antibody 50 or 80% inhibitory dilution titer measured on day 29 or day 57, as correlates of risk (CoRs) and CoPs against symptomatic COVID-19 over 4 months after dose. Here, we assessed a new marker, live virus 50% microneutralization titer (LV-MN50), and compared and combined markers in multivariable analyses. LV-MN50 was an inverse CoR, with a hazard ratio of 0.39 (95% confidence interval, 0.19 to 0.83) at day 29 and 0.51 (95% confidence interval, 0.25 to 1.04) at day 57 per 10-fold increase. In multivariable analyses, pseudovirus neutralization titers and anti-spike binding antibodies performed best as CoRs; combining antibody markers did not improve correlates. Pseudovirus neutralization titer was the strongest independent correlate in a multivariable model. Overall, these results supported pseudovirus neutralizing and binding antibody assays as CoRs and CoPs, with the live virus assay as a weaker correlate in this sample set. Day 29 markers performed as well as day 57 markers as CoPs, which could accelerate immunogenicity and immunobridging studies.

Mouse models in COVID-19 research: analyzing the adaptive immune response

The emergence of SARS-CoV-2, the severe acute respiratory syndrome coronavirus type 2 causing the COVID-19 pandemic, resulted in a major necessity for scientific countermeasures. Investigations revealing the exact mechanisms of the SARS-CoV-2 pathogenesis provide the basis for the development of therapeutic measures and protective vaccines against COVID-19. Animal models are inevitable for infection and pre-clinical vaccination studies as well as therapeutic testing. A well-suited animal model, mimicking the pathology seen in human COVID-19 patients, is an important basis for these investigations. Several animal models were already used during SARS-CoV-2 studies with different clinical outcomes after SARS-CoV-2 infection. Here, we give an overview of different animal models used in SARS-CoV-2 infection studies with a focus on the mouse model. Mice provide a well-established animal model for laboratory use and several different mouse models have been generated and are being used in SARS-CoV-2 studies. Furthermore, the analysis of SARS-CoV-2-specific T cells during infection and in vaccination studies in mice is highlighted.

Antibody-mediated protection against symptomatic COVID-19 can be achieved at low serum neutralizing titers

Multiple studies of vaccinated and convalescent cohorts have demonstrated that serum neutralizing antibody (nAb) titers correlate with protection against coronavirus disease 2019 (COVID-19). However, the induction of multiple layers of immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure has complicated the establishment of nAbs as a mechanistic correlate of protection (CoP) and hindered the definition of a protective nAb threshold. Here, we show that a half-life-extended monoclonal antibody (adintrevimab) provides about 50% protection against symptomatic COVID-19 in SARS-CoV-2-naïve adults at serum nAb titers on the order of 1:30. Vaccine modeling results support a similar 50% protective nAb threshold, suggesting that low titers of serum nAbs protect in both passive antibody prophylaxis and vaccination settings. Extrapolation of adintrevimab pharmacokinetic data suggests that protection against susceptible variants could be maintained for about 3 years. The results provide a benchmark for the selection of next-generation vaccine candidates and support the use of broad, long-acting monoclonal antibodies as alternatives or supplements to vaccination in high-risk populations.

B cell class switch recombination is regulated by DYRK1A through MSH6 phosphorylation

Protection from viral infections depends on immunoglobulin isotype switching, which endows antibodies with effector functions. Here, we find that the protein kinase DYRK1A is essential for B cell-mediated protection from viral infection and effective vaccination through regulation of class switch recombination (CSR). Dyrk1a-deficient B cells are impaired in CSR activity in vivo and in vitro. Phosphoproteomic screens and kinase-activity assays identify MSH6, a DNA mismatch repair protein, as a direct substrate for DYRK1A, and deletion of a single phosphorylation site impaired CSR. After CSR and germinal center (GC) seeding, DYRK1A is required for attenuation of B cell proliferation. These findings demonstrate DYRK1A-mediated biological mechanisms of B cell immune responses that may be used for therapeutic manipulation in antibody-mediated autoimmunity.

Heterologous prime-boost immunisation with mRNA- and AdC68-based 2019-nCoV variant vaccines induces broad-spectrum immune responses in mice

The ongoing evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or 2019-nCoV) variants has been associated with the transmission and pathogenicity of COVID-19. Therefore, exploring the optimal immunisation strategy to improve the broad-spectrum cross-protection ability of COVID-19 vaccines is of great significance. Herein, we assessed different heterologous prime-boost strategies with chimpanzee adenovirus vector-based COVID-19 vaccines plus Wuhan-Hu-1 (WH-1) strain (AdW) and Beta variant (AdB) and mRNA-based COVID-19 vaccines plus WH-1 strain (ARW) and Omicron (B.1.1.529) variant (ARO) in 6-week-old female BALB/c mice. AdW and AdB were administered intramuscularly or intranasally, while ARW and ARO were administered intramuscularly. Intranasal or intramuscular vaccination with AdB followed by ARO booster exhibited the highest levels of cross-reactive IgG, pseudovirus-neutralising antibody (PNAb) responses, and angiotensin-converting enzyme-2 (ACE2)-binding inhibition rates against different 2019-nCoV variants among all vaccination groups. Moreover, intranasal AdB vaccination followed by ARO induced higher levels of IgA and neutralising antibody responses against live 2019-nCoV than intramuscular AdB vaccination followed by ARO. A single dose of AdB administered intranasally or intramuscularly induced broader cross-NAb responses than AdW. Th1-biased cellular immune response was induced in all vaccination groups. Intramuscular vaccination-only groups exhibited higher levels of Th1 cytokines than intranasal vaccination-only and intranasal vaccination-containing groups. However, no obvious differences were found in the levels of Th2 cytokines between the control and all vaccination groups. Our findings provide a basis for exploring vaccination strategies against different 2019-nCoV variants to achieve high broad-spectrum immune efficacy.

Human immunoglobulin gene allelic variation impacts germline-targeting vaccine priming

Vaccine priming immunogens that activate germline precursors for broadly neutralizing antibodies (bnAbs) have promise for development of precision vaccines against major human pathogens. In a clinical trial of the eOD-GT8 60mer germline-targeting immunogen, higher frequencies of vaccine-induced VRC01-class bnAb-precursor B cells were observed in the high dose compared to the low dose group. Through immunoglobulin heavy chain variable (IGHV) genotyping, statistical modeling, quantification of IGHV1-2 allele usage and B cell frequencies in the naive repertoire for each trial participant, and antibody affinity analyses, we found that the difference between dose groups in VRC01-class response frequency was best explained by IGHV1-2 genotype rather than dose and was most likely due to differences in IGHV1-2 B cell frequencies for different genotypes. The results demonstrate the need to define population-level immunoglobulin allelic variations when designing germline-targeting immunogens and evaluating them in clinical trials.

One-Sentence Summary

Human genetic variation can modulate the strength of vaccine-induced broadly neutralizing antibody precursor B cell responses.

Indirect Dispersion of SARS-CoV-2 Live-Attenuated Vaccine and Its Contribution to Herd Immunity

It has been 34 months since the beginning of the SARS-CoV-2 coronavirus pandemic, which causes the COVID-19 disease. In several countries, immunization has reached a proportion near what is required to reach herd immunity. Nevertheless, infections and re-infections have been observed even in vaccinated persons. That is because protection conferred by vaccines is not entirely effective against new virus variants. It is unknown how often booster vaccines will be necessary to maintain a good level of protective immunity. Furthermore, many individuals refuse vaccination, and in developing countries, a large proportion of the population has not yet been vaccinated. Some live-attenuated vaccines against SARS-CoV-2 are being developed. Here, we analyze the indirect dispersion of a live-attenuated virus from vaccinated individuals to their contacts and the contribution that this phenomenon could have to reaching Herd Immunity.

Immune correlates analysis of a phase 3 trial of the AZD1222 (ChAdOx1 nCoV-19) vaccine

In the phase 3 trial of the AZD1222 (ChAdOx1 nCoV-19) vaccine conducted in the U.S., Chile, and Peru, anti-spike binding IgG concentration (spike IgG) and pseudovirus 50% neutralizing antibody titer (nAb ID50) measured four weeks after two doses were assessed as correlates of risk and protection against PCR-confirmed symptomatic SARS-CoV-2 infection (COVID-19). These analyses of SARS-CoV-2 negative participants were based on case-cohort sampling of vaccine recipients (33 COVID-19 cases by 4 months post dose two, 463 non-cases). The adjusted hazard ratio of COVID-19 was 0.32 (95% CI: 0.14, 0.76) per 10-fold increase in spike IgG concentration and 0.28 (0.10, 0.77) per 10-fold increase in nAb ID50 titer. At nAb ID50 below the limit of detection (< 2.612 IU50/ml), 10, 100, and 270 IU50/ml, vaccine efficacy was -5.8% (-651%, 75.6%), 64.9% (56.4%, 86.9%), 90.0% (55.8%, 97.6%) and 94.2% (69.4%, 99.1%). These findings provide further evidence towards defining an immune marker correlate of protection to help guide regulatory/approval decisions for COVID-19 vaccines.

An experimental medicine decipher of a minimum correlate of cellular immunity: Study protocol for a double-blind randomized controlled trial

Vaccination induces an adaptive immune response that protects against infectious diseases. A defined magnitude of adaptive immune response that correlates with protection from the disease of interest, or correlates of protection (CoP), is useful for guiding vaccine development. Despite mounting evidence for the protective role of cellular immunity against viral diseases, studies on CoP have almost exclusively focused on humoral immune responses. Moreover, although studies have measured cellular immunity following vaccination, no study has defined if a “threshold” of T cells, both in frequency and functionality, is needed to reduce infection burden. We will thus conduct a double-blind, randomized clinical trial in 56 healthy adult volunteers, using the licensed live-attenuated yellow fever (YF17D) and chimeric Japanese encephalitis-YF17D (JE-YF17D) vaccines. These vaccines share the entire non-structural and capsid proteome where the majority of the T cell epitopes reside. The neutralizing antibody epitopes, in contrast, are found on the structural proteins which are not shared between the two vaccines and are thus distinct from one another. Study participants will receive JE-YF17D vaccination followed by YF17D challenge, or YF17D vaccination followed by JE-YF17D challenge. A separate cohort of 14 healthy adults will receive the inactivated Japanese Encephalitis virus (JEV) vaccine followed by YF17D challenge that controls for the effect of cross-reactive flaviviral antibodies. We hypothesize that a strong T cell response induced by YF17D vaccination will reduce JE-YF17D RNAemia upon challenge, as compared to JE-YF17D vaccination followed by YF17D challenge. The expected gradient of YF17D-specific T cell abundance and functionality would also allow us to gain insight into a T cell threshold for controlling acute viral infections. The knowledge gleaned from this study could guide the assessment of cellular immunity and vaccine development.

Clinical trial registration

Clinicaltrials.gov, NCT05568953.

Development and Evaluation of Recombinant B-Cell Multi-Epitopes of PDHA1 and GAPDH as Subunit Vaccines against Streptococcus iniae Infection in Flounder (Paralichthys olivaceus)

Streptococcus iniae is a severe Gram-positive pathogen that can infect a wide range of freshwater and marine fish species. In continuation of our earlier studies on the development of S. iniae vaccine candidates, pyruvate dehydrogenase E1 subunit alpha (PDHA1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were highly efficacious in protecting flounder (Paralichthys olivaceus) against S. iniae. In the present study, to investigate the potential of multi-epitope vaccination strategy to prevent flounder against S. iniae infection, the liner B-cell epitopes of PDHA1 and GAPDH proteins were predicted using a bioinformatics approach and were identified by immunoassay, and recombinant B-cell multi-epitopes of PDHA1 and GAPDH (rMEPIP and rMEPIG) containing immunodominant epitope-concentrated domains were expressed in Escherichia coli BL21 (DE3) and were used as a subunit vaccine to immunize healthy flounder, while recombinant PDHA1 (rPDHA1), GAPDH (rGAPDH) and formalin-inactivated S. iniae (FKC) served as controls. Then, the immunoprotection efficacy of rMEPIP and rMEPIG was evaluated by determining the percentages of CD4-1+, CD4-2+, CD8β+ T lymphocytes and surface-IgM-positive (sIgM+) lymphocytes in peripheral blood leucocytes (PBLs), spleen leucocytes (SPLs) and head kidney leucocytes (HKLs), as well as total IgM, specific IgM, and relative percentage survival (RPS) post immunization, respectively. It was found that fish immunized with rPDHA1, rGAPDH, rMEPIP, rMEPIG and FKC showed significant increases in sIgM+, CD4-1+, CD4-2+, and CD8β+ lymphocytes and production of total IgM and specific IgM against S. iniae or recombinant proteins rPDHA1 and rGAPDH, which indicated the activation of humoral and cellular immune responses after vaccination. Moreover, RPS rate of the multi-epitope vaccine rMEPIP and rMEPIG groups reached 74.07% and 77.78%, higher than that of rPDHA1 and rGAPDH (62.96% and 66.67%) and KFC (48.15%). These results demonstrated that B-cell multi-epitope protein vaccination, rMEPIP and rMEPIG, could give a better protective effect against S. iniae infection, which provided a promising strategy to design the efficient vaccine in teleost fish.

Systems serology-based comparison of antibody effector functions induced by adjuvanted vaccines to guide vaccine design

The mechanisms by which antibodies confer protection vary across vaccines, ranging from simple neutralization to functions requiring innate immune recruitment via Fc-dependent mechanisms. The role of adjuvants in shaping the maturation of antibody-effector functions remains under investigated. Using systems serology, we compared adjuvants in licensed vaccines (AS01_B/AS01_E/AS03/AS04/Alum) combined with a model antigen. Antigen-naive adults received two adjuvanted immunizations followed by late revaccination with fractional-dosed non-adjuvanted antigen ( NCT00805389 ). A dichotomy in response quantities/qualities emerged post-dose 2 between AS01_B/AS01_E/AS03 and AS04/Alum, based on four features related to immunoglobulin titers or Fc-effector functions. AS01_B/E and AS03 induced similar robust responses that were boosted upon revaccination, suggesting that memory B-cell programming by the adjuvanted vaccinations dictated responses post non-adjuvanted boost. AS04 and Alum induced weaker responses, that were dissimilar with enhanced functionalities for AS04. Distinct adjuvant classes can be leveraged to tune antibody-effector functions, where selective vaccine formulation using adjuvants with different immunological properties may direct antigen-specific antibody functions.

Testable Candidate Immune Correlates of Protection for Porcine Reproductive and Respiratory Syndrome Virus Vaccination

Porcine reproductive and respiratory syndrome virus (PRRSV) is an on-going problem for the worldwide pig industry. Commercial and experimental vaccinations often demonstrate reduced pathology and improved growth performance; however, specific immune correlates of protection (CoP) for PRRSV vaccination have not been quantified or even definitively postulated: proposing CoP for evaluation during vaccination and challenge studies will benefit our collective efforts towards achieving protective immunity. Applying the breadth of work on human diseases and CoP to PRRSV research, we advocate four hypotheses for peer review and evaluation as appropriate testable CoP: (i) effective class-switching to systemic IgG and mucosal IgA neutralizing antibodies is required for protective immunity; (ii) vaccination should induce virus-specific peripheral blood CD4+ T-cell proliferation and IFN-γ production with central memory and effector memory phenotypes; cytotoxic T-lymphocytes (CTL) proliferation and IFN-γ production with a CCR7- phenotype that should migrate to the lung; (iii) nursery, finishing, and adult pigs will have different CoP; (iv) neutralizing antibodies provide protection and are rather strain specific; T cells confer disease prevention/reduction and possess greater heterologous recognition. We believe proposing these four CoP for PRRSV can direct future vaccine design and improve vaccine candidate evaluation.

Immunogenicity and safety of concomitant and sequential administration of yellow fever YF-17D vaccine and tetravalent dengue vaccine candidate TAK-003: A phase 3 randomized, controlled study

BACKGROUND

Yellow fever (YF) vaccination is often mandatory for travelers to YF-endemic areas. The areas with risk of YF partially overlap with those of dengue, for which there is currently no recommended vaccine available for dengue-naïve individuals. This phase 3 study assessed the immunogenicity and safety of concomitant and sequential administration of YF (YF-17D) and tetravalent dengue (TAK-003) vaccines in healthy adults aged 18-60 years living in areas of the US non-endemic for either virus.

METHODS

Participants were randomized 1:1:1 to receive the following vaccinations at Months 0, 3, and 6, respectively: YF-17D+placebo, TAK-003, and TAK-003 (Group 1); TAK-003+placebo, TAK-003, and YF-17D (Group 2); or YF-17D+TAK-003, TAK-003, and placebo (Group 3). The primary objective was to demonstrate non-inferiority (upper bound of 95% confidence interval [UB95%CI] of difference <5%) of YF seroprotection rate one month following concomitant administration of YF-17D and TAK-003 (Group 3) compared with YF-17D plus placebo (Group 1). The secondary objectives included demonstration of non-inferiority of YF and dengue geometric mean titers (GMTs) (UB95%CI for GMT ratio <2.0), and safety.

RESULTS

900 adults were randomized. YF seroprotection rates one month post-YF-17D (Month 1) were 99.5% and 99.1% in Group 1 and 3, respectively, and non-inferiority was demonstrated (UB95%CI = 2.69% i.e. <5%). Non-inferiority was also demonstrated for GMTs against YF one month post-YF-17D, and against DENV-2, -3, and -4 (UB95%CI <2), but not DENV-1 (UB95%CI: 2.22), one month post-second TAK-003 vaccination. Adverse event rates following TAK-003 were consistent with previous results, and no important safety risks were identified.

CONCLUSIONS

In this study, YF-17D vaccine and TAK-003 were immunogenic and well tolerated when sequentially or concomitantly administered. The non-inferiority of immune responses to YF-17D and TAK-003 was demonstrated for concomitant administration of the 2 vaccines compared to separate vaccination, except against DENV-1 but with GMTs similar to those observed in other TAK-003 trials.

TRIAL REGISTRATION

ClinicalTrials.gov identified: NCT03342898.

Vaccines for the Prevention of Coronavirus Disease 2019 in Older Adults

Institutionalized and community-dwelling older adults have been greatly impacted by the coronavirus disease 2019 (COVID-19) pandemic with increased morbidity and mortality. The advent of vaccines and their widespread use in this population has brought about a dramatic turnaround in COVID-19 outcomes. The immunogenicity and effectiveness of the various vaccine options worldwide are discussed. Optimization of vaccine usage will still be important to maximize protection due to reduced initial immunity, development of variant strains, and fading of immunity over time. There are also lessons learned specific to older populations for future pandemics of novel pathogens.