Serotype-specific IgG Research Articles

Serotype-Specific Dengue Virus IgG Assay Using EDIII-Based Recombinant Proteins and Its Application in an Endemic Population in Northeast Brazil.

Dengue is the most prevalent arboviral disease globally, with Brazil currently experiencing a significant rise in cases. Dengue virus (DENV) typically co-circulates with other clinically and antigenically similar flaviviruses, such as Zika virus (ZIKV). The clinical diagnosis is difficult and accurate serological analysis represents an unmet challenge. Traditionally, serological analysis of DENV infection focuses on the acute phase via detection of NS1 or IgM. Developing IgG DENV-specific assays has been defiant due to the co-circulation of four antigenically distinct serotypes and a strong cross-reactivity with other arboviruses, particularly with ZIKV. The goal of this study was to produce recombinant domain III of the Envelope (EDIII) proteins of each DENV serotype and ZIKV and evaluate the ability to detect specific IgG antibodies. The antigens were tested on the ELISA platform to measure DENV-specific IgG in mice and patients infected with ZIKV and DENV. The assay differentiated serotype-specific IgG responses in susceptible mice (AG129) experimentally infected with DENV or ZIKV. In addition, the test demonstrated a robust performance achieving 87.8% sensitivity and 91.4% specificity when tested against 648 well-characterized sera collected from humans infected with DENV and/or ZIKV. The test was further applied to serum samples collected from 318 healthy individuals from an endemic region in Northwest/Central Brazil, without a previous diagnosis of DENV, and revealed that 65% of the samples reacted with at least one DENV serotype antigen, including 123 monotypic samples (88 for DENV-1) and 90 samples reacting with multiple antigens. Collectively, these results indicate that the IgG DENV-EDIII ELISA is a valuable tool for assessing the serological status of populations in endemic areas, particularly in regions where other flaviviruses, particularly ZIKV, co-circulate and offer support to establish public health policies against the disease.

Development of a Shigella conjugate vaccine targeting Shigella flexneri 6 that is immunogenic and provides protection against virulent challenge

Immunity protective against shigella infection targets the bacterial O-specific polysaccharide (OSP) component of lipopolysaccharide. A multivalent shigella vaccine would ideally target the most common global Shigella species and serotypes such as Shigella flexneri 2a, S. flexneri 3a, S. flexneri 6, and S. sonnei. We previously reported development of shigella conjugate vaccines (SCVs) targeting S. flexneri 2a (SCV-Sf2a) and 3a (SCV-Sf3a) using a platform squaric acid chemistry conjugation approach and carrier protein rTTHc, a 52 kDa recombinant protein fragment of the heavy chain of tetanus toxoid. Here we report development of a SCV targeting S. flexneri 6 (SCV-Sf6) using the same platform approach. We demonstrated that SCV-Sf6 was recognized by serotype-specific monoclonal antibodies and convalescent sera of humans recovering from shigellosis in Bangladesh, suggesting correct immunological display of OSP. We vaccinated mice and found induction of serotype-specific OSP and LPS IgG and IgM responses, as well as rTTHc-specific IgG responses. Immune responses were increased when administered with aluminum phosphate adjuvant. Vaccination induced bactericidal antibody responses against S. flexneri 6, and vaccinated animals were protected against lethal challenge with virulent S. flexneri 6. Our results assist in the development of a multivalent vaccine protective against shigellosis.

Persistence of immunity in children aged 2 months and 7 months – 5 years old after primary immunization with 13-valent pneumococcal conjugate vaccine

Background: Pneumococcus is a common cause of pneumonia, meningitis, and other serious infections in children. The previous study has proved that the 13-valent pneumococcal conjugate vaccine (PCV13) has sufficient immunogenicity in children. The data on long-term persistence of immunity will help the follow-up development work of pneumococcal vaccines.Methods: Children who received the full vaccination course of the tested PCV13 in the previous clinical trial were enrolled again, and these who received other pneumococcal vaccines, or were infected with one or more serotypes of S. pneumoniae corresponding to PCV13 before enrollment were excluded. Participants were divided into four groups by age which is same as that of previous trial. The study lasted for 5 years, during which we measured pneumococcal antibodies of 13 serotypes included in PCV13 at particular points in time. Geometric mean concentrations (GMCs) and seropositive rates (the rate of IgG concentration ≥0.35 μg/mL) of antibodies against 13 serotypes were calculated.Results: For the participants aged 2 months, five years after primary vaccination, except for serotypes 3 and 4, seropositive rates were 100%. GMCs of IgG antibodies against 13 serotypes ranged from 0.733 to 15.160 μg/mL. All of the participants aged 7–11 months had the serotype-specific IgG concentration ≥0.35 μg/mL four years after primary vaccination with the exception of serotypes 3, 4, 6 A and 9 V. IgG GMCs were 0.753–11.031 μg/mL. All participants aged 12–23 months and 2–5 years old had the serotype-specific IgG concentration ≥0.35 μg/mL three or two years after primary vaccination respectively, except for serotype 3. IgG GMCs ranged from 0.815 to 13.111 μg/mL, and 0.684 to 12.282 μg/mL respectively.Conclusion: PCV13 was applied to the population aged 2 months and 7 months - 5 years old with a good immune persistence, providing more extensive evidence of long-term efficacy for that vaccine.Trial Registration: The trial was registered with ClinicalTrials.gov, number NCT06210737.

A Phase 3 Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of V116 in Pneumococcal Vaccine-Experienced Adults 50 Years of Age or Older (Stride-6).

Pneumococcal diseases (PD) cause considerable morbidity and mortality in adults. V116 is an investigational 21-valent pneumococcal conjugate vaccine (PCV) specifically designed to protect adults from pneumococcal serotypes responsible for the majority of residual PD. This phase 3 study evaluated safety, tolerability, and immunogenicity of V116 in pneumococcal vaccine-experienced adults ≥50 years. A total of 717 adults were enrolled to receive a single dose of pneumococcal vaccine as follows: Cohort 1 (n=350) previously received PPSV23 and were randomized 2:1 to receive V116 or PCV15, respectively; Cohort 2 (n=261) previously received PCV13 and were randomized 2:1 to receive V116 or PPSV23, respectively; Cohort 3 (n=106) previously received PPSV23+PCV13, PCV13+PPSV23, PCV15+PPSV23, or PCV15 and all received open-label V116. Immunogenicity was evaluated 30 days postvaccination using opsonophagocytic activity (OPA) geometric mean titers (GMTs) and IgG geometric mean concentrations (GMCs) for all V116 serotypes. Safety was evaluated as the proportion of participants with adverse events (AEs). V116 was immunogenic across all 3 cohorts as assessed by serotype-specific OPA GMTs and IgG GMCs postvaccination for all 21 serotypes. V116 elicited comparable immune responses to serotypes shared with PCV15 (Cohort 1) or PPSV23 (Cohort 2), and higher immune responses to serotypes unique to V116. The proportions of participants with solicited AEs were generally comparable across cohorts. V116 is well tolerated with a safety profile comparable to currently licensed pneumococcal vaccines and generates IgG and functional immune responses to all V116 serotypes, regardless of prior pneumococcal vaccine received.

Safety, tolerability, and immunogenicity of an adult pneumococcal conjugate vaccine, V116 (STRIDE-3): a randomised, double-blind, active comparator controlled, international phase 3 trial

The same pneumococcal conjugate vaccines (PCVs) have been used in adults and children in many settings. Differences in the epidemiology of pneumococcal disease between populations necessitates an adult-specific PCV. We aimed to assess the safety, tolerability, and immunogenicity of V116, an investigational 21-valent PCV designed for adults. This randomised, double-blind, active comparator controlled, international phase 3 trial enrolled adults with or without stable chronic medical conditions at 112 clinical sites in 11 countries or territories. Random assignment was performed using a central electronic interactive response technology system. Cohort 1 (≥50 years) was stratified by age (50-64, 65-74, 75-84, and ≥85 years) and randomised 1:1 to receive one intramuscular dose of V116, or the active comparator, PCV20. Cohort 2 (18-49 years) was randomised 2:1 to receive one intramuscular dose of V116 or PCV20. Pneumococcal serotype-specific opsonophagocytic activity (OPA) and IgG responses were measured before (day 1) and after vaccination (day 30). Four primary immunogenicity outcomes were assessed per-protocol. First, in cohort 1, non-inferiority of V116 to PCV20 was tested using serotype-specific OPA geometric mean titres (GMT) ratios for serotypes common to both vaccines; the lower bound of the 95% CI had to be greater than 0·5 for non-inferiority. Second, superiority of V116 to PCV20 was tested for OPA GMT ratios for the serotypes unique to V116; the lower bound of the 95% CI had to be greater than 2·0 for superiority. Third, superiority of V116 to PCV20 was evaluated by the proportions of participants with a four-fold or greater rise from day 1 to day 30 for serotypes unique to V116; the lower bound of the 95% CI of the differences in proportions (V116 - PCV20) had to be greater than 10% for superiority. Finally, in cohort 2, immunobridging was assessed for all 21 serotypes in V116 for adults aged 18-49 years to 50-64 years; the lower bound of the 95% CI for the OPA GMTs had to be greater than 0·5 for non-inferiority. The safety analysis included all randomly assigned participants who received study vaccine. The primary safety outcome was the proportion of participants with solicited injection site and solicited systemic adverse events until day 5 and vaccine-related serious adverse events up to 6 months after vaccination. This trial is registered at ClinicalTrials.gov (NCT05425732). Between July 13, and Nov 22, 2022, 2754 individuals were screened and 2663 participants were randomly assigned. 2656 individuals were vaccinated (1179 in V116 cohort 1; 1177 in PCV20 cohort 1; 200 in V116 cohort 2; and 100 in PCV20 cohort 2). V116 met non-inferiority criteria compared with PCV20 for the ten serotypes common to both vaccines at day 30 in cohort 1 (p<0·0001 for each common serotype). V116 met superiority criteria compared with PCV20 in cohort 1 for ten of the 11 serotypes unique to V116 at day 30 (OPA GMT ratio: p<0·0001 for all unique serotypes except 15C, which was p=0·41; four-fold or greater rise in OPA from day 1-30: p<0·0001 for all serotypes except 15C, which was p=0·67). Immune responses in V116 participants aged 18-49 years were non-inferior compared with V116 participants aged 50-64 years for all V116 serotypes (p<0·0001 for all V116 serotypes). In cohort 1, 685 (58·2%) of participants in V116, and 778 (66·2%) of participants in PCV20 reported one or more adverse event. In cohort 2, 164 (82·0%) participants in V116 and 79 participants (79·0%) in PCV20 reported one or more adverse event. Six deaths were reported, all in cohort 1, none of which were considered vaccine-related (in V116: one due to sepsis, one due to cerebrovascular accident, one due to myocardial infarction, and one due to hepatic cirrhosis and hepatic encephalopathy; in PCV20: one due to cardiac arrest and one due to abdominal abscess). There were no vaccine-related serious adverse events. V116 was non-inferior to PCV20 for the ten serotypes common to both vaccines and superior to PCV20 for all serotypes unique to V116, except for 15C. Immune responses successfully immunobridged between younger and older adults for all serotypes in V116. V116 was generally well tolerated with safety profile similar to PCV20. Merck Sharp & Dohme, subsidiary of Merck & Co, Rahway, NJ, USA (MSD).

Safety and Immunogenicity of a 4-Component Generalized Modules for Membrane Antigens Shigella Vaccine in Healthy European Adults: Randomized, Phase 1/2 Study.

We report data from stage 1 of an ongoing 2-staged, phase 1/2 randomized clinical trial with a 4-component generalized modules for membrane antigens-based vaccine against Shigella sonnei and Shigella flexneri 1b, 2a, and 3a (altSonflex1-2-3; GSK). Europeans aged 18-50 years (N = 102) were randomized (2:1) to receive 2 injections of altSonflex1-2-3 or placebo at 3- or 6-month interval. Safety and immunogenicity were assessed at prespecified time points. The most common solicited administration-site event (until 7 days after each injection) and unsolicited adverse event (until 28 days after each injection) were pain (altSonflex1-2-3, 97.1%; placebo, 58.8%) and headache (32.4%; 23.5%), respectively. All serotype-specific functional IgG antibodies peaked 14-28 days after injection 1 and remained substantially higher than prevaccination at 3 or 6 months postvaccination; the second injection did not boost but restored the initial immune response. The highest seroresponse rates (≥4-fold increase in titers over baseline) were obtained against S. flexneri 2a (enzyme-linked immunosorbent assay [ELISA] after injection 1, 91.0%; after injection 2 [day 113; day 197], 100%; 97.0% and serum bactericidal activity [SBA] after injection 1, 94.4%; after injection 2, 85.7%; 88.9%) followed by S. sonnei (ELISA after injection 1, 77.6%; after injection 2, 84.6%; 78.8% and SBA after injection 1, 83.3%; after injection 2, 71.4%; 88.9%). Immune responses against S. flexneri 1b and S. flexneri 3a, as measured by both ELISA and SBA, were numerically lower compared to those against S. sonnei and S. flexneri 2a. No safety signals or concerns were identified. altSonflex1-2-3 induced functional serotype-specific immune responses, allowing further clinical development in the target population. Clinical Trials Registration . NCT05073003.

Development and validation of a 6-plex Luminex-based assay for measuring human serum antibodies to group B streptococcus capsular polysaccharides

ABSTRACT Six serotypes (Ia, Ib, II, III, IV, and V) cause nearly all group B streptococcal (GBS) disease globally. Capsular polysaccharide (CPS) conjugate vaccines aim to prevent GBS disease, however, licensure of a vaccine would depend on a standardized serological assay for measuring anti-CPS IgG responses. A multiplex direct Luminex-based immunoassay (dLIA) has been developed to simultaneously measure the concentration of serum IgG specific for the six prevalent GBS CPS serotypes. Assay validation was performed using serum samples obtained from human subjects vaccinated with an investigational 6-valent GBS CPS conjugate vaccine. Results for the assay are expressed as IgG concentrations (µg/mL) using a human serum reference standard composed of pooled sera from vaccinated subjects. The lower limits of quantitation (LLOQ) for all serotypes covered in the 6-plex GBS IgG dLIA fell within the range of 0.002-0.022 µg/mL IgG. Taken together, the 6-plex GBS IgG dLIA platform is specific for the six GBS serotypes included in Pfizer’s investigational vaccine, has a wide dilution adjusted assay range, and is precise (<18.5% relative standard deviation) for all serotypes, and, therefore, is suitable for quantitatively measuring vaccine-induced or naturally acquired serotype-specific anti-CPS IgG responses against GBS.

A Phase 3, Single-arm Trial to Evaluate the Safety and Immunogenicity of a 20-Valent Pneumococcal Conjugate Vaccine in Healthy Children 15 Months Through

A 20-valent pneumococcal conjugate vaccine (PCV20), containing 13-valent PCV (PCV13) components and 7 additional polysaccharide conjugates, was developed to extend protection for pneumococcal disease. This phase 3 study assessed the safety and immunogenicity of PCV20 in children. In this single-arm study, children (≥15 months-<18 years of age) received 1 dose of PCV20. Children <5 years of age had ≥3 prior doses of PCV13; children ≥5 years were recruited regardless of previous PCV receipt. Serotype-specific IgG concentrations and opsonophagocytic activity (OPA) titers were measured before and 1 month after PCV20. Local reactions and systemic events, adverse events (AEs), serious AEs, and newly diagnosed chronic medical conditions were collected. Of 839 enrolled participants, 831 (>99%) were vaccinated, and 819 (>97%) completed all study visits. Local reactions and systemic events were mostly mild to moderate in severity. No serious AEs were considered PCV20-related. IgG geometric mean fold rises (GMFRs) from before to 1 month after PCV20 ranged from 27.9-1847.7 (7 additional serotypes) and 2.9-44.9 (PCV13 serotypes) in children <5 years of age, and 10.5-187.7 (7 additional serotypes) and 4.3-127.9 (PCV13 serotypes) in children ≥5 years old. OPA GMFRs from before to 1 month after PCV20 ranged from 12.4-983.6 to 2.8-52.9 in children <5 years of age and from 11.5-499.0 to 5.3-147.9 in children ≥5 years of age. Among children ≥15 months through <18 years of age, PCV20 was well tolerated and induced robust responses to all 20 serotypes, supporting the use of PCV20 in children.

Validation and comprehensive analysis of Streptococcus pneumoniae IgG WHO enzyme-linked immunosorbent assay in an Indian reference laboratory.

Monitoring serotype-specific IgG levels againstpneumococci is crucial for assessing immunity, vaccine efficacy, and evaluating vaccination programs. The WHO ELISA for pneumococci is a standardized assay ensuring consistency in testing and comparability of results across laboratories. It involves a rigorous testing process to confirm accurate, precise and reliable detection of antibodies. We validated the protocol for 13 pneumococcal serotypes by assessing its specificity, reproducibility (coefficient of variation ≤15%), repeatability (coefficient of variation ≤20%), accuracy, lower limit of quantification, stability, and robustness. We found these parameters were within acceptable ranges and showed excellent performance. Our findings imply that the method employed is appropriate for evaluating 13 valent pneumococcal conjugate vaccine which is introduced in the national immunization program by comparing pre-and post-vaccination IgG response.

P21 A Phase 3 randomized, double-blind, active comparator-controlled study to evaluate the safety, tolerability and immunogenicity of a 21-valent PCV, V116, in pneumococcal vaccine-naive adults (STRIDE-3)

Abstract Background Pneumococcal disease (PD) prevention remains an unmet medical need in adults. V116 is an investigational pneumococcal conjugate vaccine (PCV) containing the most prevalent serotypes associated with PD in adults in regions with established paediatric vaccination programmes. This Phase 3 study evaluated safety, tolerability, and immunogenicity of V116 compared with PCV20 in adults. Methods Pneumococcal vaccine-naive adults ≥18 years were eligible. Cohort 1 (≥50 years, n=2362) was stratified by age (50–64, 65–74, 75–84 and ≥85) and randomized 1:1 to receive 1 dose of V116 or PCV20, and cohort 2 (18–49 years, n=301) was randomized 2:1 to receive 1 dose of V116 or PCV20. Pneumococcal serotype-specific opsonophagocytic activity (OPA) and IgG responses were measured at baseline (Day 1) and 30 days post vaccination (Day 30). Primary objectives included assessment of (i) non-inferiority of immune responses for the serotypes common to V116 and PCV20 in cohort 1; (ii) superiority of serotypes unique to V116 compared with PCV20 in cohort 1; and (iii) immunobridging from adults 18–49 to adults 50–64 for all 21 serotypes in V116. Safety was evaluated by the proportion of participants with adverse events (AEs). Results V116 is non-inferior to PCV20 for the 10 serotypes common to both vaccines as measured by serotype-specific OPA geometric mean titres (GMTs) at Day 30. V116 is superior to PCV20 for 10 of 11 unique serotypes as measured by OPA GMTs at Day 30 as well as based on the proportions of participants with a ≥4-fold rise in OPA from Day 1 to Day 30. V116 elicits comparable immune responses in participants 18–49 years compared with participants 50–64 years for the 21 serotypes in V116 as assessed by serotype-specific OPA GMTs at Day 30, successfully demonstrating immunobridging. In total, 61.7% and 67.2% of participants vaccinated with V116 and PCV20, respectively, had ≥1 AE. There were no vaccine-related serious AEs or vaccine-related deaths. Conclusions V116 elicits immune responses that are non-inferior to PCV20 for the common serotypes and superior to PCV20 for 10 of 11 unique serotypes in V116 and has a safety profile comparable to PCV20. This pivotal study supports V116 as a novel population-specific vaccine for the prevention of PD in adults.

Naturally acquired antibodies against 4 Streptococcus pneumoniae serotypes in Pakistani adults with type 2 diabetes mellitus.

Immune response elicited during pneumococcal carriage has been shown to protect against subsequent colonization and infection by Streptococcus pneumoniae. The study was designed to measure the baseline serotype-specific anti-capsular IgG concentration and opsonic titers elicited in response to asymptomatic carriage in adults with and without type 2-diabetes. Level of IgG to capsular polysaccharide was measured in a total of 176 samples (124 with type 2 diabetes and 52 without type 2 diabetes) against serotype 1, 19F, 9V, and 18C. From within 176 samples, a nested cohort of 39 samples was selected for measuring the functional capacity of antibodies by measuring opsonic titer to serotypes 19F, 9V, and 18C. Next, we measured levels of IgG to PspA in 90 samples from individuals with and without diabetes (22 non-diabetes and 68 diabetes). Our results demonstrated comparable IgG titers against all serotypes between those with and without type 2-diabetes. Overall, we observed higher opsonic titers in those without diabetes as compared to individuals with diabetes for serotypes 19F and 9V. The opsonic titers for 19F and 9V significantly negatively correlated with HbA1c. For 19F, 41.66% (n = 10) showed opsonic titers ≥ 1:8 in the diabetes group as compared to 66.66% (n = 10) in the non-diabetes group. The percentage was 29.6% (n = 7) vs 66.66% (n = 10) for 9V and 70.83% (n = 17) vs 80% (n = 12) for 18C in diabetes and non-diabetes groups respectively. A comparable anti-PspA IgG (p = 0.409) was observed in those with and without diabetes, indicating that response to protein antigen is likely to remain intact in those with diabetes. In conclusion, we demonstrated comparable IgG titers to both capsular polysaccharide and protein antigens in those with and without diabetes, however, the protective capacity of antibodies differed between the two groups.

Baseline Pneumococcal IgG Levels and Response to 23-Valent Pneumococcal Polysaccharide Vaccine among Adults from Beijing, China.

To investigate the baseline levels of serotype-specific IgG antibodies to Streptococcus pneumoniae (S. pneumoniae) and assess their impact on the assessment of vaccine immunogenicity. We used a subset of serum samples from a randomized controlled trial. The blood of 584 healthy participants was collected on day 0 before and day 28 after the 23-valent pneumococcal polysaccharide vaccine (PPSV23) vaccination. Serotype-specific IgG against PPSV23-covered serotypes were measured by the World Health Organization (WHO) reference enzyme-linked immunosorbent assay (ELISA). Vaccine immunogenicity was compared using conversion rates (proportion of participants with IgG levels following immunization that are 2-fold greater than the baseline) and geometric mean fold rises (GMFRs) between the two groups, which were grouped according to pre-vaccination (baseline) IgG antibody levels. Our data showed that over half of individuals have baseline IgG levels for 15 out of 23 serotypes above 1.3 µg/mL, and geometric mean concentrations (GMCs) were generally higher in the elderly group and the female group; significant differences were found in 15 serotypes for vaccine immunogenicity based on the seroconversion rate or GMFRs between individuals with baseline IgG ≥ 1.3 µg/mL and individuals with baseline IgG < 1.3 µg/mL. The seroconversion rate decreased with the increase of baseline IgG levels according to a linear regression model. The assessment of vaccine immunogenicity could be impacted by the fact that many adults had high baseline antibody levels. This study is registered in the Chinese Clinical Trial Registry, number NCT05298800.

Potential for Maternally Administered Vaccine for Infant Group B Streptococcus

BackgroundNatural 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.MethodsIn 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.ResultsNaturally 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.ConclusionsGBS6 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.)

Development of Shigella conjugate vaccines targeting Shigella flexneri 2a and S. flexneri 3a using a simple platform-approach conjugation by squaric acid chemistry

There is a need for vaccines effective against shigella infection in young children in resource-limited areas. Protective immunity against shigella infection targets the O-specific polysaccharide (OSP) component of lipopolysaccharide. Inducing immune responses to polysaccharides in young children can be problematic, but high level and durable responses can be induced by presenting polysaccharides conjugated to carrier proteins. An effective shigella vaccine will need to be multivalent, targeting the most common global species and serotypes such as Shigella flexneri 2a, S. flexneri 3a, S. flexneri 6, and S. sonnei. Here we report the development of shigella conjugate vaccines (SCV) targeting S. flexneri 2a (SCV-Sf2a) and 3a (SCV-Sf3a) using squaric acid chemistry to result in single point sun-burst type display of OSP from carrier protein rTTHc, a 52 kDa recombinant protein fragment of the heavy chain of tetanus toxoid. We confirmed structure and demonstrated that these conjugates were recognized by serotype-specific monoclonal antibodies and convalescent sera of humans recovering from shigellosis in Bangladesh, suggesting correct immunological display of OSP. We vaccinated mice and found induction of serotype-specific OSP and LPS IgG responses, as well as rTTHc-specific IgG responses. Vaccination induced serotype-specific bactericidal antibody responses against S. flexneri, and vaccinated animals were protected against keratoconjunctivitis (Sereny test) and intraperitoneal challenge with virulent S. flexneri 2a and 3a, respectively. Our results support further development of this platform conjugation technology in the development of shigella conjugate vaccines for use in resource-limited settings.

Immunogenicity and seroefficacy of 10-valent and 13-valent pneumococcal conjugate vaccines: a systematic review and network meta-analysis of individual participant data.

Vaccination of infants with pneumococcal conjugate vaccines (PCV) is recommended by the World Health Organization. Evidence is mixed regarding the differences in immunogenicity and efficacy of the different pneumococcal vaccines. In this systematic-review and network meta-analysis, we searched the Cochrane Library, Embase, Global Health, Medline, clinicaltrials.gov and trialsearch.who.int up to February 17, 2023 with no language restrictions. Studies were eligible if they presented data comparing the immunogenicity of either PCV7, PCV10 or PCV13 in head-to-head randomised trials of young children under 2 years of age, and provided immunogenicity data for at least one time point after the primary vaccination series or the booster dose. Publication bias was assessed via Cochrane's Risk Of Bias due to Missing Evidence tool and comparison-adjusted funnel plots with Egger's test. Individual participant level data were requested from publication authors and/or relevant vaccine manufacturers. Outcomes included the geometric mean ratio (GMR) of serotype-specific IgG and the relative risk (RR) of seroinfection. Seroinfection was defined for each individual as a rise in antibody between the post-primary vaccination series time point and the booster dose, evidence of presumed subclinical infection. Seroefficacy was defined as the RR of seroinfection. We also estimated the relationship between the GMR of IgG one month after priming and the RR of seroinfection by the time of the booster dose. The protocol is registered with PROSPERO, ID CRD42019124580. 47 studies were eligible from 38 countries across six continents. 28 and 12 studies with data available were included in immunogenicity and seroefficacy analyses, respectively. GMRs comparing PCV13 vs PCV10 favoured PCV13 for serotypes 4, 9V, and 23F at 1 month after primary vaccination series, with 1.14- to 1.54- fold significantly higher IgG responses with PCV13. Risk of seroinfection prior to the time of booster dose was lower for PCV13 for serotype 4, 6B, 9V, 18C and 23F than for PCV10. Significant heterogeneity and inconsistency were present for most serotypes and for both outcomes. Two-fold higher antibody after primary vaccination was associated with a 54% decrease in risk of seroinfection (RR 0.46, 95% CI 0.23-0.96). Serotype-specific differences were found in immunogenicity and seroefficacy between PCV13 and PCV10. Higher antibody response after vaccination was associated with a lower risk of subsequent infection. These findings could be used to compare PCVs and optimise vaccination strategies. The NIHR Health Technology Assessment Programme.

Calibration of a serum reference standard for Group B streptococcal polysaccharide conjugate vaccine development using surface plasmon resonance

Group B streptococcus (GBS) is a leading cause of neonatal morbidity and mortality worldwide. Development of a maternal vaccine to protect newborns through placentally transferred antibody is considered feasible based on the well-established relationship between anti-GBS capsular polysaccharide (CPS) IgG levels at birth and reduced risk of neonatal invasive GBS. An accurately calibrated serum reference standard that can be used to measure anti-CPS concentrations is critical for estimation of protective antibody levels across serotypes and potential vaccine performance. For this, precise weight-based measurement of anti-CPS IgG in sera is required. Here, we report an improved approach for determining serum anti-CPS IgG levels using surface plasmon resonance with monoclonal antibody standards, coupled with a direct Luminex-based immunoassay. This technique was used to quantify serotype-specific anti-CPS IgG levels in a human serum reference pool derived from subjects immunized with an investigational six-valent GBS glycoconjugate vaccine.

Pneumococcal carriage following PCV13 delivered as one primary and one booster dose (1+1) compared to two primary doses and a booster (2+1) in UK infants.

In January 2020 the UK changed from a 2+1 schedule for 13-valent pneumococcal conjugate vaccine (PCV13) to a 1+1 schedule (doses at 3 and 12months) based on a randomized immunogenicity trial comparing the two schedules. Carriage prevalence measured at the time of booster and 6months later in 191 of the 213 study infants was 57% (109/191) and 60% (114/190) respectively. There were eight episodes of vaccine-type (VT) or vaccine-related 6C carriage in the 2+1 and six in the 1+1 group; ≥4-fold rises in serotype-specific IgG in 71 children with paired post-booster and follow up blood samples at 21-33months of age were found in 20% (7/35) of the 2+1 and 15% (6/41) of the 1+1 group. VTs identified in carriage and inferred from serology were similar comprising 3, 19A and 19F. Dropping a priming dose from the 2+1 PCV 13 schedule did not increase VT carriage in the study cohort. Ongoing population level carriage studies will be important to confirm this.

Reduced quantity and function of pneumococcal antibodies are associated with exacerbations of COPD in SPIROMICS

While hypogammaglobulinemia is associated with COPD exacerbations, it is unknown whether frequent exacerbators have specific defects in antibody production/function. We hypothesized that reduced quantity/function of serum pneumococcal antibodies correlate with exacerbation risk in the SPIROMICS cohort.We measured total pneumococcal IgG in n = 764 previously vaccinated participants with COPD. In a propensity-matched subset of n = 200 with vaccination within five years (n = 50 without exacerbations in the previous year; n = 75 with one, n = 75 with ≥2), we measured pneumococcal IgG for 23 individual serotypes, and pneumococcal antibody function for 4 serotypes.Higher total pneumococcal IgG, serotype-specific IgG (17/23 serotypes), and antibody function (3/4 serotypes) were independently associated with fewer prior exacerbations. Higher pneumococcal IgG (5/23 serotypes) predicted lower exacerbation risk in the following year.Pneumococcal antibodies are inversely associated with exacerbations, supporting the presence of immune defects in frequent exacerbators. With further study, pneumococcal antibodies may be useful biomarkers for immune dysfunction in COPD.

P05 Safety, tolerability, and immunogenicity of V114 compared with PCV13 in preterm infants: a pooled subgroup analysis of four Phase III studies

Abstract Background Risk of invasive pneumococcal disease is 3-fold higher in preterm versus full-term infants, mainly due to underlying comorbidities and immunological immaturity. V114 is a 15-valent pneumococcal conjugate vaccine (PCV) containing the 13 serotypes in 13-valent PCV (PCV13) plus two additional serotypes, 22F and 33F. A pooled subgroup analysis was performed in preterm infants (&amp;lt;37 weeks gestational age) enrolled in 4 paediatric Phase III studies evaluating the safety and immunogenicity of different 4-dose regimens of V114 or PCV13. Methods Safety was evaluated as the proportion of participants with AEs following each vaccination. Serotype-specific anti-pneumococcal IgG GMCs, IgG response rates, and OPA GMTs were measured at 30 days post-primary series (PPS; post-dose 3 [PD3]), pre-toddler dose, and 30 days post-toddler dose (PTD; post-dose 4 [PD4]). Results 174 and 180 participants received V114 and PCV13, respectively. Mean gestational age was 35.4 weeks (range: 27–37 weeks). Proportions of participants with any AE were comparable between vaccination groups following each vaccination; most solicited AEs were transient (≤3 days) and of mild-to-moderate intensity. V114-elicited IgG GMCs (Figure 1), IgG response rates, and OPA GMTs were generally comparable to PCV13 for the 13 shared serotypes and higher for serotypes 22F and 33F at 30 days PPS (PD3) and PTD (PD4). Conclusions In preterm infants, vaccination with V114 has an acceptable safety profile, is well tolerated, and induces comparable immune responses to PCV13 for the 13 shared serotypes and higher immune responses to V114 serotypes 22F and 33F. Study results support use of V114 in preterm infants.

P09 A Phase 2, randomized, double-blind study to evaluate the safety, tolerability, and immunogenicity of a 21-valent pneumococcal conjugate vaccine (V116) in adults ≥50 years

Abstract Background V116 is an investigational 21-valent PCV containing the following pneumococcal polysaccharides: 3, 6A, 7F, 8, 9N, 10A, 11A,12F, 15A, 16F, 17F, 19A, 20, 22F, 23A, 23B, 24F, 31, 33F, 35B, and a de-O-acetylated 15B (deOAc15B). This phase 2 study evaluated the safety, tolerability, and immunogenicity of V116 in pneumococcal vaccine-naïve adults compared with a 23-valent pneumococcal vaccine (PPSV23). Methods Adults (n=508) ≥50 years were randomized 1:1 and received a single dose of V116 or PPSV23; randomization was stratified by age (50–64 years, 65–74 years, and ≥75 years). Adverse events (AEs) were collected following vaccination. Pneumococcal serotype-specific opsonophagocytic activity (OPA) and IgG were measured before and 30 days after vaccination (Day 30). Primary immunogenicity objectives were to assess the noninferiority of V116 to PPSV23 for the shared serotypes and the superiority of V116 to PPSV23 for the unique serotypes. Results There were no vaccine-related serious AEs or vaccine-related deaths. V116 met noninferiority criteria compared with PPSV23 for all shared serotypes [based on the lower bound of the 95% CIs for the estimated OPA GMT ratios (V116/PPSV23) being &amp;gt;0.33 at Day 30] and met superiority criteria for the unique serotypes [based on the lower bound of the 95% CIs for the estimated OPA GMT ratios (V116/PPSV23) being &amp;gt;1.0 at Day 30]. Conclusions In adults ≥50 years, V116 is well tolerated with a safety profile comparable to PPSV23, elicits an immune response that is noninferior to PPSV23 for the shared serotypes and superior to PPSV23 for the unique serotypes.