Pre-existing antibody levels negatively correlate with antibody titers after a single dose of BBV152 vaccination

Safety and immunogenicity of Ad26.COV2.S in adolescents: Phase 2 randomized clinical trial

We conducted a randomized, Phase 2 trial to assess the safety and humoral immunogenicity of reduced doses/dose volume of the standard dose of Ad26.COV2.S COVID-19 vaccine (5 × 1010 viral particles [vp]) in healthy adolescents aged 12-17 years. Participants were randomly assigned to receive Ad26.COV2.S at reduced dose levels of 0.625 × 1010 (0.5 mL), 1.25 × 1010 (0.5 mL) or 2.5 × 1010 (0.5 mL or low volume 0.25 mL) vp in a 1- or 2-dose (56-day interval) primary schedule. Adolescents who received a 1-dose primary schedule received a 2.5 × 1010 vp booster dose 6 months later. Safety and humoral immunogenicity were assessed up to 6 months post-last vaccination. All regimens were well tolerated, with no safety concerns identified. Local and systemic solicited AEs in adolescents were consistent with the known safety profile in adults. All 1- and 2-dose Ad26.COV2.S primary schedules elicited robust peak Spike-binding antibody responses and virus neutralizing titers against the reference strain, in participants with and without preexisting SARS-CoV-2 immunity. Immune responses were durable for at least 6 months. Spike-binding antibody responses were comparable to those elicited in young adults aged 18-25 years who received a standard dose of Ad26.COV2.S in Phase 3 efficacy studies Reduced doses/dose volume of Ad26.COV2.S had an acceptable safety profile and elicited robust humoral immune responses in adolescents aged 12-17 years. All 1- and 2-dose schedules elicited Spike-binding antibody responses that were comparable to an adult population in whom efficacy has been demonstrated using a higher vaccine dose. (clinicaltrials.gov NCT05007080).

Adults with low opsonic natural antibody levels against Streptococcus pneumoniae show enhanced response to PPSV23 vaccination

BACKGROUND

Pneumococcal diseases pose a significant public health concern globally, particularly among young children and the elderly. Vaccination plays a crucial role in their prevention. This study evaluated the functional immune responses to Pneumococcal polysaccharide vaccine serotypes in healthy Indian adults before and after administering a single dose of PPSV23 immunization.

METHODS

A total of 125 healthy participants aged 18-65 received the PPSV23 vaccine, and their pre- and post-immunization sera were analyzed by MOPA. Opsonic Index, Geometric mean OPA titers and fold increase for each serotype was calculated.

RESULTS

The highest baseline OPA GMTs were observed for serotypes 33F,17F,9N,20, and 6B. The lowest OPA GMTs were noted against types 1 and 12F. OPA GMTs post-vaccination increased significantly for all serotypes, with geometric mean fold rise (GMFR) ranging from 4.3 to 267.5. Participants with low pre-immunization OPA titers (<8 & <64) showed significant increases in OI fold raise across all tested serotypes post-vaccination. This robust immune response was consistent across serotypes, indicating highly effective seroconversion in individuals with low baseline antibody levels.

CONCLUSION

The PPSV23 vaccine elicits a strong immunogenic response in individuals with low pre-immunization OPA titers, achieving substantial increases in opsonic index fold raise across various serotypes.

Antibody dynamics for heterologous boosters with aerosolized Ad5-nCoV following inactivated COVID-19 vaccines

The COVID-19 pandemic has underscored vaccination as a crucial strategy for reducing disease severity and preventing hospitalizations. Heterologous boosters using aerosolized Ad5-nCoV following two doses of inactivated vaccine have demonstrated superior antibody responses. However, the comprehensive dynamics of this antibody boost and the optimal timing for heterologous boosters are still not fully understood. In this study, we investigated the dynamics of neutralizing antibody (nAb) responses in recipients of heterologous booster vaccinations with aerosolized Ad5-nCoV following either two (I-I-A) or three (I-I-I-A) doses of COVID-19 inactivated vaccines. The findings indicate that a booster dose of aerosolized Ad5-nCoV vaccine induced robust and durable nAb responses comparable to those elicited in BA.5 breakthrough infections with similar doses of inactivated vaccine. Notably, group I-I-A showed higher peak nAb titers against the WT strain, BA.5, and XBB.1 variants compared to group I-I-I-A, inversely correlating with the prior nAb levels. This suggesting the possible efficacy of the heterologous aerosolized Ad5-nCoV booster and indicates that pre-boost antibody levels may be related to the outcomes of booster vaccination.

A novel orf virus vector-based COVID-19 booster vaccine shows cross-neutralizing activity in the absence of anti-vector neutralizing immunity

Next-generation COVID-19 vaccines are being developed to expand the breadth of coverage against existing and future variants and to extend the duration of protection. Prime-2-CoV_Beta is an orf virus (ORFV) based multi-antigen COVID-19 vaccine that co-expresses Spike (S) and Nucleocapsid (N) antigens. The safety and immunogenicity of Prime-2-CoV_Beta is investigated in a phase 1 first-in-human (FIH) dose-finding trial (ORFEUS study, ClinicalTrials.gov: NCT05367843). Participants of two age groups (18-55 and 65-85 years) who previously completed at least two doses of mRNA vaccines were enrolled and sequentially assigned to different dose groups to receive one intramuscular dose of 3 × 105, 3 × 106, 1.5 × 107, or 3 × 107 plaque-forming units (PFU) of Prime-2-CoV_Beta on day 1 and a second dose on day 29. Here, we report safety and immunogenicity data collected up to 6 months after the first study vaccination. Prime-2-CoV_Beta is safe and well tolerated and elicits immune responses at higher dose levels in participants aged 18-55. A single dose of 3 × 107 PFU boosted binding and cross-neutralizing antibody responses that are maintained through 6 months after the first booster vaccination. Polyfunctional S-specific CD4+ and CD8+ T cell responses are observed after vaccination. No pre-existing or vaccine-induced neutralizing anti-vector antibodies are detected. Our findings highlight the potential of the ORFV vector as a safe platform for future vaccine design, which provides the ability to deliver multiple antigens and allows for repeat immunization.

The Effective Inhibitory Concentration of Interferon-β Correlates with Infectivity and Replication Fitness of SARS-CoV-2 Variants

India saw a spike in COVID-19 cases in early 2023, and this wave of infection was attributed to XBB sublineages of SARS-CoV-2 Omicron variant. The impact of XBB wave was significantly shorter with low burden of severe cases or hospitalization as compared with previous SARS-CoV-2 variants of concern. Although a combination of old and new mutations in the spike region of XBB.1.16 variant led to a drastic reduction in the ability of antibodies from prior immunity to neutralize this virus, additional nonspike mutations suggested a possible change in its ability to suppress innate immune responses. In this study, we tested the sensitivity of Delta, BA.2.75, and XBB.1.16 variants to interferon-β (IFN-β) treatment and found that XBB.1.16 variant was most sensitive to IFN-β. We next tested the ability of serum antibodies from healthy individuals to neutralize XBB.1.16. We showed that most of the individuals with hybrid immunity maintained a low but significant level of neutralizing antibodies to XBB.1.16 variant. Therefore, our observations indicated that both hybrid immunity because of natural infection and enhanced sensitivity to IFNs may have contributed to the low impact of XBB.1.16 infections in India.

Novel Multi-Antigen Orf-Virus-Derived Vaccine Elicits Protective Anti-SARS-CoV-2 Response in Monovalent and Bivalent Formats

Prime-2-CoV_Beta is a novel Orf virus (ORFV)-based COVID-19 vaccine candidate expressing both the nucleocapsid and spike proteins of SARS-CoV-2 with the receptor-binding domain (RBD) of the Beta strain. This candidate was shown to be safe and immunogenic in a first-in-human Phase I clinical trial. With the shift in the immune landscape toward the Omicron variant and the widespread vaccine- and/or infection-derived immunity, further pre-clinical research was needed to characterize Prime-2-CoV. Here, we quantified the humoral and cellular response to Prime-2-CoV_Beta in pre-immunized mice and compared the protective efficacy of mono- and bivalent variant-based Prime-2-CoV vaccine candidates in hamsters. Prime-2-CoV_Beta induced robust humoral and cellular immune responses in naïve animals but did not further boost antibody titers in the tested setting when given as repeat booster at short interval. We furthermore showed that Prime-2-CoV_Beta-based mono- and bivalent immunization strategies produced comparable immunogenicity and protection from infection. Our results highlight the potential of the Orf virus as a vaccine platform against SARS-CoV-2 and potentially other infectious viruses.

MVA-based vaccine candidates encoding the native or prefusion-stabilized SARS-CoV-2 spike reveal differential immunogenicity in humans

In response to the COVID-19 pandemic, multiple vaccines were developed using platforms such as viral vectors and mRNA technology. Here, we report humoral and cellular immunogenicity data from human phase 1 clinical trials investigating two recombinant Modified Vaccinia virus Ankara vaccine candidates, MVA-SARS-2-S and MVA-SARS-2-ST, encoding the native and the prefusion-stabilized SARS-CoV-2 spike protein, respectively. MVA-SARS-2-ST was more immunogenic than MVA-SARS-2-S, but both were less immunogenic compared to licensed mRNA- and ChAd-based vaccines in SARS-CoV-2 naïve individuals. In heterologous vaccination, previous MVA-SARS-2-S vaccination enhanced T cell functionality and MVA-SARS-2-ST boosted the frequency of T cells and S1-specific IgG levels when used as a third vaccination. While the vaccine candidate containing the prefusion-stabilized spike elicited predominantly S1-specific responses, immunity to the candidate with the native spike was skewed towards S2-specific responses. These data demonstrate how the spike antigen conformation, using the same viral vector, directly affects vaccine immunogenicity in humans.

Reinfection rates, change in antibody titers and adverse events after COVID-19 vaccination among patients previously infected with COVID-19 in Metro Manila, Philippines: a secondary analysis of a completed cohort study

BACKGROUND

Variation in immune response to COVID-19 vaccines is observed among different ethnicities. We aimed to describe the reinfection rates, change in antibody titers, and adverse events among Filipinos.

METHODS

This is a secondary analysis of a cohort study of 307 participants within one year of having COVID-19 infection. We measured COVID-19 antibody levels at pre-determined timepoints (Days 21, 90, 180, 270, and 360 from initial infection). We monitored for COVID-19 symptoms and obtained details on COVID-19 vaccination. An adjudication committee classified the participants as probable, possible, or unlikely COVID-19 reinfection. We determined the probable reinfection rate, adverse events, and the geometric mean titer (GMT) ratio of pre- and post-vaccination antibody levels according to type and brand of COVID-19 vaccine.

RESULTS

At the end of the follow-up period, 287 (93.5%) out of 307 study participants were fully vaccinated, 1 was partially vaccinated (0.3%), and 19 were unvaccinated (6.2%). Among the fully vaccinated participants, those given mRNA vaccines had the lowest reinfection rate (19.2 cases/100 person-years, 95% CI 9.6, 38.4), followed by viral vector vaccines (29.8 cases/100 person-years, 95% CI 16.9, 52.4). We observed the highest reinfection rate among those given inactivated virus vaccines (32.7 cases/100 person-years, 95% CI 23.6, 45.3). The reinfection rate was 8.6 cases/100 person-years (95% CI 4.1, 17.9) for unvaccinated participants and 3.6 cases/100 person-years (95% CI 0.5, 25.3) for partially vaccinated participants. We observed the largest rise in antibody titers among those given mRNA vaccines (GMT ratio 288.5), and the smallest rise among those given inactivated virus vaccines (GMT ratio 16.7). We observed the highest percentage of adverse events following immunization with viral vector vaccines (63.8%), followed by mRNA vaccines (62.7%), and the lowest for inactivated virus vaccines (34.7%). No serious adverse events were reported.

CONCLUSION

Vaccinees given the mRNA vaccines had the lowest reinfection rate and the highest rise in antibody titers. Vaccinees given inactivated virus vaccines had the highest reinfection rate, smallest rise in antibody titers, and lowest percentage of adverse events. The small sample size and imbalanced distribution of the type of vaccines received limits the external generalizability of our results.

STUDY REGISTRATION

The cohort study was registered at the Philippine Health Research Registry on December 14, 2020 (PHRR201214-003199).

Neutralizing antibodies from prior exposure to dengue virus negatively correlate with viremia on re-infection

BACKGROUND

India is hyperendemic to dengue and over 50% of adults are seropositive. There is limited information on the association between neutralizing antibody profiles from prior exposure and viral RNA levels during subsequent infection.

METHODS

Samples collected from patients with febrile illness was used to assess seropositivity by indirect ELISA. Dengue virus (DENV) RNA copy numbers were estimated by quantitative RT-PCR and serotype of the infecting DENV was determined by nested PCR. Focus reduction neutralizing antibody titer (FRNT) assay was established using Indian isolates to measure the levels of neutralizing antibodies and also to assess the cross-reactivity to related flaviviruses namely Zika virus (ZIKV), Japanese encephalitis virus (JEV) and West Nile virus (WNV).

RESULTS

In this cross-sectional study, we show that dengue seropositivity increased from 52% in the 0-15 years group to 89% in >45 years group. Antibody levels negatively correlate with dengue RNAemia on the day of sample collection and higher RNAemia is observed in primary dengue as compared to secondary dengue. The geometric mean FRNT50 titers for DENV-2 is significantly higher as compared to the other three DENV serotypes. We observe cross-reactivity with ZIKV and significantly lower or no neutralizing antibodies against JEV and WNV. The FRNT50 values for international isolates of DENV-1, DENV-3 and DENV-4 is significantly lower as compared to Indian isolates.

CONCLUSIONS

Majority of the adult population in India have neutralizing antibodies to all the four DENV serotypes which correlates with reduced RNAemia during subsequent infection suggesting that antibodies can be considered as a good correlate of protection.

Targeting DPP4-RBD interactions by sitagliptin and linagliptin delivers a potential host-directed therapy against pan-SARS-CoV-2 infections

Highly mutated SARS-CoV-2 is known aetiological factor for COVID-19. Here, we have demonstrated that the receptor binding domain (RBD) of the spike protein can interact with human dipeptidyl peptidase 4 (DPP4) to facilitate virus entry, in addition to the usual route of ACE2-RBD binding. Significant number of residues of RBD makes hydrogen bonds and hydrophobic interactions with α/β-hydrolase domain of DPP4. With this observation, we created a strategy to combat COVID-19 by circumventing the catalytic activity of DPP4 using its inhibitors. Sitagliptin, linagliptin or in combination disavowed RBD to establish a heterodimer complex with both DPP4 and ACE2 which is requisite strategy for virus entry into the cells. Both gliptins not only impede DPP4 activity, but also prevent ACE2-RBD interaction, crucial for virus growth. Sitagliptin, and linagliptin alone or in combination have avidity to impede the growth of pan-SARS-CoV-2 variants including original SARS-CoV-2, alpha, beta, delta, and kappa in a dose dependent manner. However, these drugs were unable to alter enzymatic activity of PLpro and Mpro. We conclude that viruses hijack DPP4 for cell invasion via RBD binding. Impeding RBD interaction with both DPP4 and ACE2 selectively by sitagliptin and linagliptin is an potential strategy for efficiently preventing viral replication.

Anti-spike Antibody Status in Pre-vaccinated Healthy Participants and Rheumatoid Arthritis Patients During the Third Wave of COVID-19

Introduction Anti-spike severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies produced after infection with the coronavirus disease of 2019 (COVID-19) will offer protection and prevent re-infection for a few months. Seroprevalence studies measuring the SARS‑CoV-2 immunoglobulin G (IgG) levels will be helpful to know the herd immunity level that prevents community transmission. Very few studies have addressed the antibody titer among healthy participants and rheumatoid arthritis (RA) patients. The present study was conducted to determine the anti-spike SARS-CoV-2 antibody (Ab) status before COVID-19 vaccination in healthy participants and RA patients. Methodology A cross-sectional study was conducted at a tertiary care hospital to estimate the serum anti-spike antibody levels against COVID-19 among the pre-vaccinated healthy participants and patients with RA during the third wave of COVID-19. After receiving written informed consent, participants were recruited as per the inclusion and exclusion criteria. Demographic details, co-morbid status, and medication details were collected. Five milliliters of blood samples were collected, and anti-spike antibodies were estimated. The SARS-CoV-2 Ab positivity rate was expressed in percentage and was correlated with gender and age groups. Ab-positive participants were classified into three categories based on the neutralizing antibody titers (NAT). Results A total of 58 participants (49 healthy volunteers and nine RA patients) were recruited. Out of 58 participants, 40 were males, nine were females among healthy participants, and one male and eight females in the RA group were enrolled. Among the RA patients, one participant was found to have the chronic obstructive pulmonary disease (COPD), and two participants with hypothyroidism. Antibody positivity was found to be 83.6% among the healthy volunteers and 100% in the RA patients. About 48% had NAT between 50 and 90%. There was no significant difference for age and gender-specific positivity for SARS-CoV-2 neutralizing antibodies and neutralizing antibody titers among healthy participants. Conclusion Our study showed 84% positivity for anti-spike SARS-CoV-2 antibodies around the third wave (between November 2021 and February 2022). The majority had high neutralizing antibody titers. The probable reason for the SARS-CoV-2 antibody positivity before vaccination was either asymptomatic infection or herd immunity.

Tracking of activated cTfh cells following sequential influenza vaccinations reveals transcriptional profile of clonotypes driving a vaccine-induced immune response

Introduction

A vaccine against influenza is available seasonally but is not 100% effective. A predictor of successful seroconversion in adults is an increase in activated circulating T follicular helper (cTfh) cells after vaccination. However, the impact of repeated annual vaccinations on long-term protection and seasonal vaccine efficacy remains unclear.

Methods

In this study, we examined the T cell receptor (TCR) repertoire and transcriptional profile of vaccine-induced expanded cTfh cells in individuals who received sequential seasonal influenza vaccines. We measured the magnitude of cTfh and plasmablast cell activation from day 0 (d0) to d7 post-vaccination as an indicator of a vaccine response. To assess TCR diversity and T cell expansion we sorted activated and resting cTfh cells at d0 and d7 post-vaccination and performed TCR sequencing. We also single cell sorted activated and resting cTfh cells for TCR analysis and transcriptome sequencing.

Results and discussion

The percent of activated cTfh cells significantly increased from d0 to d7 in each of the 2016-17 (p < 0.0001) and 2017-18 (p = 0.015) vaccine seasons with the magnitude of cTfh activation increase positively correlated with the frequency of circulating plasmablast cells in the 2016-17 (p = 0.0001) and 2017-18 (p = 0.003) seasons. At d7 post-vaccination, higher magnitudes of cTfh activation were associated with increased clonality of cTfh TCR repertoire. The TCRs from vaccine-expanded clonotypes were identified and tracked longitudinally with several TCRs found to be present in both years. The transcriptomic profile of these expanded cTfh cells at the single cell level demonstrated overrepresentation of transcripts of genes involved in the type-I interferon pathway, pathways involved in gene expression, and antigen presentation and recognition. These results identify the expansion and transcriptomic profile of vaccine-induced cTfh cells important for B cell help.

BA.1, BA.2 and BA.2.75 variants show comparable replication kinetics, reduced impact on epithelial barrier and elicit cross-neutralizing antibodies

The Omicron variant of SARS-CoV-2 is capable of infecting unvaccinated, vaccinated and previously-infected individuals due to its ability to evade neutralization by antibodies. With multiple sub-lineages of Omicron emerging in the last 12 months, there is inadequate information on the quantitative antibody response generated upon natural infection with Omicron variant and whether these antibodies offer cross-protection against other sub-lineages of Omicron variant. In this study, we characterized the growth kinetics of Kappa, Delta and Omicron variants of SARS-CoV-2 in Calu-3 cells. Relatively higher amounts infectious virus titers, cytopathic effect and disruption of epithelial barrier functions was observed with Delta variant whereas infection with Omicron sub-lineages led to a more robust induction of interferon pathway, lower level of virus replication and mild effect on epithelial barrier. The replication kinetics of BA.1, BA.2 and BA.2.75 sub-lineages of the Omicron variant were comparable in cell culture and natural infection in a subset of individuals led to a significant increase in binding and neutralizing antibodies to the Delta variant and all the three sub-lineages of Omicron but the level of neutralizing antibodies were lowest against the BA.2.75 variant. Finally, we show that Cu2+, Zn2+ and Fe2+ salts inhibited in vitro RdRp activity but only Cu2+ and Fe2+ inhibited both the Delta and Omicron variants in cell culture. Thus, our results suggest that high levels of interferons induced upon infection with Omicron variant may counter virus replication and spread. Waning neutralizing antibody titers rendered subjects susceptible to infection by Omicron variants and natural Omicron infection elicits neutralizing antibodies that can cross-react with other sub-lineages of Omicron and other variants of concern.

Novel coronavirus mutations: Vaccine development and challenges

The ongoing global pandemic of novel coronavirus pneumonia (COVID-19) caused by the SARS-CoV-2 has a significant impact on global health and economy system. In this context, there have been some landmark advances in vaccine development. Over 100 new coronavirus vaccine candidates have been approved for clinical trials, with ten WHO-approved vaccines including four inactivated virus vaccines, two mRNA vaccines, three recombinant viral vectored vaccines and one protein subunit vaccine on the "Emergency Use Listing". Although the SARS-CoV-2 has an internal proofreading mechanism, there have been a number of mutations emerged in the pandemic affecting its transmissibility, pathogenicity and immunogenicity. Of these, mutations in the spike (S) protein and the resultant mutant variants have posed new challenges for vaccine development and application. In this review article, we present an overview of vaccine development, the prevalence of new coronavirus variants and their impact on protective efficacy of existing vaccines and possible immunization strategies coping with the viral mutation and diversity.

Anti-drug Antibody Sample Testing and Reporting Harmonization

A clear scientific and operational need exists for harmonized bioanalytical immunogenicity study reporting to facilitate communication of immunogenicity findings and expedient review by industry and health authorities. To address these key bioanalytical reporting gaps and provide a report structure for documenting immunogenicity results, this cross-industry group was formed to establish harmonized recommendations and a develop a submission template to facilitate agency filings. Provided here are recommendations for reporting clinical anti-drug antibody (ADA) assay results using ligand-binding assay technologies. This publication describes the essential bioanalytical report (BAR) elements such as the method, critical reagents and equipment, study samples, results, and data analysis, and provides a template for a suggested structure for the ADA BAR. This publication focuses on the content and presentation of the bioanalytical ADA sample analysis report. The interpretation of immunogenicity data, including the evaluation of the impact of ADA on safety, exposure, and efficacy, is out of scope of this publication.

Antibody Response to SARS-CoV-2 among COVID-19 Confirmed Cases and Correlates with Neutralizing Assay in a Subgroup of Patients in Delhi National Capital Region, India

Background: The plaque reduction neutralization test (PRNT) is the gold standard to detect the neutralizing capacity of serum antibodies. Neutralizing antibodies confer protection against further infection. The present study measured the antibody level against SARS-CoV-2 among laboratory-confirmed COVID-19 cases and evaluated whether the presence of anti-SARS-CoV-2 antibodies indicates virus neutralizing capacity. Methods: One hundred COVID-19 confirmed cases were recruited. Their sociodemographic details and history of COVID-19 vaccination, contact with positive COVID-19 cases, and symptoms were ascertained using a self-developed semi-structured interview schedule. Serum samples of the participants were collected within three months from the date of the positive report of COVID-19. The presence of anti-SARS-CoV-2 antibodies (IgA, IgG and IgM antibodies), receptor binding domain antibodies (anti-RBD), and neutralizing antibodies were measured. Findings: Almost all the participants had anti-SARS-CoV-2 antibodies (IgA, IgG and IgM) (99%) and anti-RBD IgG antibodies (97%). However, only 69% had neutralizing antibodies against SARS-CoV-2. Anti-RBD antibody levels were significantly higher among participants having neutralizing antibodies compared with those who did not. Interpretation: The present study highlights that the presence of antibodies against SARS-CoV-2, or the presence of anti-RBD antibodies does not necessarily imply the presence of neutralizing antibodies.