Optimization and application of a multiplex bead-based assay to quantify serotype-specific IgG against Streptococcus pneumoniae polysaccharides: response to the booster vaccine after immunization with the pneumococcal 7-valent conjugate vaccine

Multiple vaccine comparison in the same adults reveals vaccine-specific and age-related humoral response patterns: an open phase IV trial

Vaccine responsiveness is often reduced in older adults. Yet, our lack of understanding of low vaccine responsiveness hampers the development of effective vaccination strategies to reduce the impact of infectious diseases in the ageing population. Young-adult (25-49 y), middle-aged (50-64 y) and older-adult ( ≥ 65 y) participants of the VITAL clinical trials (n = 315, age-range: 28-98 y), were vaccinated with an annual (2019-2020) quadrivalent influenza (QIV) booster vaccine, followed by a primary 13-valent pneumococcal-conjugate (PCV13) vaccine (summer/autumn 2020) and a primary series of two SARS-CoV-2 mRNA-1273 vaccines (spring 2021). This unique setup allowed investigation of humoral responsiveness towards multiple vaccines within the same individuals over the adult age-range. Booster QIV vaccination induced comparable H3N2 hemagglutination inhibition (HI) titers in all age groups, whereas primary PCV13 and mRNA-1273 vaccination induced lower antibody concentrations in older as compared to younger adults (primary endpoint). The persistence of humoral responses, towards the 6 months timepoint, was shorter in older adults for all vaccines (secondary endpoint). Interestingly, highly variable vaccine responder profiles overarching multiple vaccines were observed. Yet, approximately 10% of participants, mainly comprising of older male adults, were classified as low responders to multiple vaccines. This study aids the identification of risk groups for low vaccine responsiveness and hence supports targeted vaccination strategies. Trial number: NL69701.041.19, EudraCT: 2019-000836-24.

Evaluating patient immunocompetence through antibody response to pneumococcal polysaccharide vaccine using a newly developed 23 serotype multiplexed assay

Assessing T-cell independent antibody response to polysaccharide vaccines is crucial for diagnosing humoral immune deficiencies. However, immunocompetence criteria based on S. pneumoniae vaccination remain unclear. We evaluated IgG antibody vaccine response in healthy individuals to establish interpretive criteria. Pre- and 4-week post-vaccination sera were collected from 79 adults. Antibody concentrations to PNEUMOVAX 23 serotypes were measured using a multiplexed platform. Immunocompetence was determined by fold increase in post-vaccination response, percentage of serotypes achieving 4- or 2-fold antibody ratio, and post-vaccination concentration ≥ 1.3 μg/mL. Immunogenicity varied widely across the 23 serotypes (26.6% to 94.9% for ≥4-fold increase, 51.9% to 98.7% for ≥2-fold increase). Immunocompetence based on historic criteria of ≥4-fold increase in antibody ratio to ≥70% of serotypes was low (72.2%), but increased to 98.7% with criteria of at least a 2-fold increase and/or post-vaccination concentration ≥ 1.3 μg/mL. Current criteria for assessing immunocompetence may be overly stringent and require updating.

Combined deficient response to polysaccharide-based and protein-based vaccines predicts a severe clinical phenotype

OBJECTIVES

Antibody response on polysaccharide- and protein-based vaccines is useful to test B cell functionality. As only few studies have explored the value of studying immune response to both vaccines, we evaluated the clinical value of anti-polysaccharide and anti-protein Luminex-based multiplex assays in context of primary immunodeficiency (PID) diagnosis.

METHODS

A 10-plex Luminex-based assay detecting antibodies to ten pneumococcal polysaccharide (PnPS) serotypes [present in unconjugated Pneumovax, not in 13-valent pneumococcal conjugated vaccine (PCV)] and a 5-plex assay detecting antibodies to five protein antigens (present in DTap/Tdap) were clinically validated in healthy individuals (n=99) and in retrospective (n=399) and prospective (n=108) patient cohorts. Clinical features of individuals with impaired response to PnPS and/or proteins were compared to those with normal response.

RESULTS

Antigen-specific antibody thresholds were determined in healthy individuals. Individuals with impaired anti-PnPS responses and deficient immunoglobulin levels suffered more from autoimmune diseases and had lower B cell levels compared to individuals with impaired anti-PnPS response with normal immunoglobulin levels. Individuals with combined impaired response to PnPS and proteins showed more severe clinical manifestations compared to individuals with isolated impaired response to PnPS or proteins. Eight of the 11 individuals with severely impaired responses to both PnPS and proteins had common variable immunodeficiency. Evaluation of the anti-PnPS response to four serotypes not contained in 20-valent PCV was comparable to evaluation to ten serotypes not contained in 13-valent PCV.

CONCLUSIONS

Multiplexed assessment of anti-PnPS and anti-protein responses combined with immunoglobulin quantification provides useful clinical information to support PID diagnosis.

Mode of delivery modulates the intestinal microbiota and impacts the response to vaccination

The gut microbiota in early life, when critical immune maturation takes place, may influence the immunogenicity of childhood vaccinations. Here we assess the association between mode of delivery, gut microbiota development in the first year of life, and mucosal antigen-specific antibody responses against pneumococcal vaccination in 101 infants at age 12 months and against meningococcal vaccination in 66 infants at age 18 months. Birth by vaginal delivery is associated with higher antibody responses against both vaccines. Relative abundances of vaginal birth-associated Bifidobacterium and Escherichia coli in the first weeks of life are positively associated with anti-pneumococcal antibody responses, and relative abundance of E. coli in the same period is also positively associated with anti-meningococcal antibody responses. In this study, we show that mode of delivery-induced microbiota profiles of the gut are associated with subsequent antibody responses to routine childhood vaccines.

Kinetics of pneumococcal antibodies among HIV-exposed, uninfected infants in Botswana

BACKGROUND

Streptococcus pneumoniae is a leading cause of severe infections among children. Despite vaccination, HIV-exposed, uninfected (HEU) children have a higher incidence of invasive pneumococcal disease than HIV-unexposed, uninfected (HUU) children. We sought to compare the immunogenicity of 13-valent pneumococcal conjugate vaccine (PCV-13) in HEU and HUU infants.

METHODS

We conducted a prospective cohort study of 134 mother-infant dyads in Botswana. Infants received PCV-13 doses at 2, 3, and 4 months through routine clinical care. We measured IgG antibodies specific to vaccine serotypes in sera collected from infants at 0, 5, and 12 months of age. We calculated the proportion of infants with protective IgG levels (≥0.35 µg/mL) to specific pneumococcal serotypes.

RESULTS

At birth, fewer than half of infants had protective IgG levels to serotypes 1 (38%), 3 (46%), 4 (33%), 5 (23%), 6B (40%), 7F (44%), 9 V (44%), and 23F (46%). Compared to HUU infants (n = 97), HEU infants (n = 37) had lower antibody concentrations at birth to serotypes 5 (p = 0.046) and 19A (p = 0.008) after adjustment for maternal age and infant birth weight. More than 80% of HEU and HUU infants developed protective antibody levels to each of the 13 vaccine serotypes following PCV-13 vaccination. Median concentrations of antibodies to pneumococcal serotypes declined by 55-93% between 5 and 12 months of age, with fewer than half of infants having protective antibody levels to serotypes 1 (47%), 3 (28%), 9 V (44%), 18C (24%), and 23F (49%) at 12 months of age.

CONCLUSIONS

Both HEU and HUU infants developed protective antibody responses to PCV-13 administered in a 3 + 0 schedule. However, antibody concentrations to many pneumococcal serotypes waned substantially by 12 months of age, suggesting that a PCV-13 booster dose in the second year of life may be needed to maintain protective pneumococcal antibody levels in older infants and young children.

Salivary antibody responses to ten-valent pneumococcal conjugate vaccination following two different immunization schedules in a healthy birth cohort

Pneumococcal conjugate vaccines reduce pneumococcal colonization via serotype-specific immunoglobulin G (IgG) at mucosal surfaces. The infant immunization schedule with the ten-valent pneumococcal conjugate vaccine (PCV10) changed from a 3 + 1 schedule (2-3-4-11 months) to a 2 + 1 schedule (2-4-11 months) in The Netherlands in 2013. We compared anti-pneumococcal IgG concentrations in saliva between the schedules. IgG was measured using a fluorescent bead-based multiplex immunoassay at the ages of 6 (post-primary) and 12 (post-booster) months in 51 infants receiving the 3 + 1 schedule and 68 infants receiving the 2 + 1 schedule. Post-primary IgG geometric mean concentrations (GMCs) were comparable between schedules for all vaccine serotypes. Post-booster IgG GMCs were significantly lower after the 2 + 1 schedule for serotypes 4 (p = 0.035), 7F (p = 0.048) and 23F (p = 0.0056). This study shows small differences in mucosal IgG responses between a 3 + 1 and a 2 + 1 PCV10 schedule. Future studies should establish correlates of protection against pneumococcal colonization for mucosal antibodies.

Predictive factors for vaccine failure to guide vaccination in allogeneic hematopoietic stem cell transplant recipients

Vaccination after hematopoietic stem cell transplantation (HSCT) is essential to protect high-risk patients against potentially lethal infections. Though multiple studies have evaluated vaccine specific responses, no comprehensive analysis of a complete vaccination schedule post-HSCT has been performed and little is known about predictors for vaccine failure. In this context, allogeneic HSCT (alloHSCT) patients were included and vaccinated starting one year post-transplantation. Antibody responses were measured by Multiplex Immuno Assay for pneumococcal (PCV13), meningococcal C, diphtheria, pertussis, tetanus and Haemophilus influenza type b one month after the last vaccination and correlated to clinical and immunological parameters. Vaccine failure was defined as antibody response above vaccine-specific cut-off values for less than four out of six vaccines. Ninety-six patients were included of which 27.1% was found to have vaccine failure. Only 40.6% of all patients responded adequately to all six vaccines. In multivariate analysis, viral reactivation post-HSCT (OR 6.53; P = 0.03), B-cells <135 per mm³ (OR 7.24; P = 0.00) and NK-cells <170 per mm³ (OR 11.06; P = 0.00) were identified as predictors for vaccine failure for vaccination at one year post-alloHSCT. Measurement of antibody responses and an individualized approach for revaccination guided by clinical status and immune reconstitution of B-cells and NK-cells may improve vaccine responses.

Nasopharyngeal Microbiota Profiles in Rural Venezuelan Children Are Associated With Respiratory and Gastrointestinal Infections

Background

Recent research suggests that the microbiota affects susceptibility to both respiratory tract infections (RTIs) and gastrointestinal infections (GIIs). In order to optimize global treatment options, it is important to characterize microbiota profiles across different niches and geographic/socioeconomic areas where RTI and GII prevalences are high.

Methods

We performed 16S sequencing of nasopharyngeal swabs from 209 Venezuelan Amerindian children aged 6 weeks–59 months who were participating in a 13-valent pneumococcal conjugate vaccine (PCV13) study. Using random forest models, differential abundance testing, and regression analysis, we determined whether specific bacteria were associated with RTIs or GIIs and variation in PCV13 response.

Results

Microbiota compositions differed between children with or without RTIs (P = .018) or GIIs (P = .001). Several species were associated with the absence of infections. Some of these health-associated bacteria are also observed in developed regions, such as Corynebacterium (log2(fold change [FC]) = 3.30 for RTIs and log2(FC) = 1.71 for GIIs), while others are not commonly observed in developed regions, such as Acinetobacter (log2(FC) = 2.82 and log2(FC) = 5.06, respectively). Klebsiella spp. presence was associated with both RTIs (log2(FC) = 5.48) and GIIs (log2(FC) = 7.20).

Conclusions

The nasopharyngeal microbiota of rural Venezuelan children included several bacteria that thrive in tropical humid climates. Interestingly, nasopharyngeal microbiota composition not only differed in children with an RTI but also in those with a GII, which suggests a reciprocal interplay between the 2 environments. Knowledge of region-specific microbiota patterns enables tailoring of preventive and therapeutic approaches.

Correlation of Vaccine Responses

Introduction

The humoral response to vaccinations varies widely between individuals. There is no data available on the correlation between responses to different vaccines. In this study, we investigated the correlation of antibody responses between routine vaccine antigens in infants.

Methods

One and seven months after the 6-month vaccinations and one month after the 12-month vaccinations, antibody concentrations to diphtheria, tetanus, pertussis, polio (serotypes 1-3), Haemophilus influenzae type b (Hib), pneumococcus (13 serotypes), meningococcus C, measles, mumps and rubella were measured using fluorescent bead-based multiplex immune-assays. For the correlation of antibody responses, Spearman's rank correlation coefficients (ρ) with 95% confidence intervals (CI) were calculated between responses to each vaccine antigen.

Results

The correlation between concentrations of antibodies to the vaccinations ending at 6 months of age was higher one month compared to seven months after vaccination. The strongest correlations at both time points were observed between antibody responses to different polio serotypes, certain pneumococcal serotypes and between responses to diphtheria and pneumococcal (conjugated to a diphtheria toxoid) vaccine antigens. Correlation between responses to tetanus, Hib, pertussis, polio and other vaccine antigens were weak. The correlation between antibody responses to the 12-month vaccine antigens was weaker than to the 6-month vaccine antigens and there was a negative correlation between responses to measles, mumps, rubella vaccine and non-live vaccine antigens (meningococcus C, tetanus and Hib). There was only weak correlation between antibody responses to vaccines of the same type (e.g. conjugated polysaccharide or toxoid vaccines).

Conclusion

Correlation between antibody responses to similar antigens in the same vaccine (such as different serotypes of a bacteria or virus), as well as responses to antigens conjugated to similar carrier proteins, are strong. In contrast, correlation between responses to other vaccines are weak. Measuring antibody responses to one or a few vaccine antigens therefore does not offer a reliable surrogate marker of responses to unrelated vaccines.

Association of Routine Infant Vaccinations With Antibody Levels Among Preterm Infants

IMPORTANCE

The standard schedule of national immunization programs for infants may not be sufficient to protect extremely and very preterm infants.

OBJECTIVE

To evaluate the immunogenicity of routine vaccinations administered to preterm infants.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, prospective, observational cohort study of preterm infants stratified according to gestational age recruited from 8 hospitals across the Netherlands between October 2015 and October 2017, with follow-up until 12 months of age (October 2018). In total, 296 premature infants were enrolled and compared with a control group of 66 healthy term infants from a 2011 study, immunized according to the same schedule with the same vaccines.

EXPOSURES

Three primary doses of the diphtheria-tetanus toxoids-acellular pertussis-inactivated poliomyelitis-Haemophilus influenza type b-hepatitis B combination vaccine were given at 2, 3, and 4 months after birth followed by a booster at 11 months and a 10-valent pneumococcal conjugate vaccine at 2, 4, and 11 months after birth.

MAIN OUTCOMES AND MEASURES

Primary end points were (1) proportion of preterm infants who achieved IgG antibody against vaccine antigens at concentrations above the internationally defined threshold for protection after the primary series and booster dose and (2) serum IgG geometric mean concentrations after the primary series and booster vaccination. Proportions and geometric mean concentrations were compared in preterm infants and the control group of term infants.

RESULTS

Of 296 preterm infants (56.1% male; mean gestational age, 30 weeks), complete samples before vaccination, 1 month after the primary series, and 1 month after the booster were obtained from 220 preterm infants (74.3%). After the primary series, the proportion of preterm infants across all gestational age groups who achieved protective IgG antibody levels against pertussis toxin, diphtheria, tetanus and 6 of 10 pneumococcal serotypes varied between 83.0% and 100%, Haemophilus influenzae type b between 34.7% and 46.2% (40.6% among all preterm infants overall), and pneumococcal serotypes 4, 6B, 18C, and 23F between 45.8% and 75.1%. After the booster dose, protective antibody levels were achieved in more than 95% of all preterm groups, except for Haemophilus influenzae type b (88.1%). In general, geometric mean concentrations of all vaccine-induced antibodies were significantly lower in all preterm infants vs term infants, except for pertussis toxin and pneumococcal serotypes 4 and 19F after the primary series and booster vaccination.

CONCLUSIONS AND RELEVANCE

Among preterm infants, administration of routine vaccinations during the first year of life was associated with protective antibody levels against most antigens in the majority of infants after the primary series and booster, except for Haemophilus influenzae type b. However, antibody concentrations were generally lower among preterm infants compared with historical controls.

Isolating polysaccharide IgG pneumococcal antibody responses by pre-adsorption of conjugate vaccine serotypes: A modified approach for the conjugate vaccine era

BACKGROUND

Assessment of pure polysaccharide response to the 23-valent pneumococcal polysaccharide vaccine (PPV23) can be biased by previous exposure to the conjugate vaccine (PCV). We applied pre-analytical modification to the existing ELISA by pre-incubating serum with PCV.

METHODS

PCV-adsorbed and non-adsorbed sera were prepared before measuring the concentration of anti-pneumococcal capsular polysaccharide (PCP) IgG antibodies by the whole pneumococcal ELISA. Paired pre and post-pneumococcal vaccination sera from 73 subjects were analyzed and the baseline anti-PCP IgG for each sample was subtracted from the post-vaccination value to measure vaccine responses. Absolute change in titers and fold changes were then compared between both methods.

RESULTS

In the PCV-vaccinated group (n = 28), pre-adsorption with PCV significantly reduced the vaccine responses compared to non-adsorbed sera [median increase in anti-PCP titers: 27.55 mg/l and 45.98 mg/l, respectively]. In addition, the median fold change dropped significantly from 3.026 to 2.313. In PPV23-vaccinated immunocompetent subjects (n = 28) there was a significant difference in anti-PCP responses with PCV adsorption [median values: 73.71 mg/l without and 51.04 mg/l with adsorption]. All the antibody deficiency patients (n = 17) displayed poor PPV23 responses. Although PPV23 responsiveness was not statistically different between both methods, we have observed a trend for lower anti-PCP IgG titers in PCV-adsorbed sera compared to non-adsorbed ones. Serotype-specific IgG analysis using a multiplexed bead-based immunoassay performed on 10 paired samples confirmed that the adsorption observed is specific to PCV serotypes.

CONCLUSION

Pre-analytical modification to the conventional ELISA by removing the PCV-specific serotypes may differentiate true polysaccharide response from recall response induced by previous PCV vaccination.

Diagnosis and management of Specific Antibody Deficiency

Specific antibody deficiency is a primary immunodeficiency disease recognized by the International Union of Immunology Societies and defined by recurrent respiratory infections with normal immunoglobulins, but diminished antibody responses to polysaccharide antigens after vaccination with the 23 valent pneumococcal polysaccharide vaccine. Clinical immunologists struggle with diagnosis and treatment, because the definition of an adequate response to immunization remains controversial. Specific antibody deficiency is managed clinically with close follow-up and prompt treatment of infections, antibiotic prophylaxis, or immune globulin therapy. Treatment is individualized using clinical judgment and existing practice guidelines, which will likely evolve as more studies become available.

Pneumococcal Conjugate Vaccination Followed by Pneumococcal Polysaccharide Vaccination in Lung Transplant Candidates and Recipients

Background

Pneumococcal conjugate vaccination as well as pneumococcal polysaccharide vaccination are recommended for lung transplant candidates and recipients, but the combination of these vaccines has not been extensively studied in these specific populations.

Methods

Lung transplant candidates and recipients were vaccinated with a 13-valent pneumococcal conjugate vaccine, followed 8 weeks later by a pneumococcal polysaccharide vaccine. Pneumococcal antibody levels against 13 pneumococcal serotypes were measured and followed up after 1 year in the transplant recipients. These values were compared with a historical control group vaccinated with the polysaccharide vaccine alone.

Results

Twenty-five lung transplant candidates and 23 lung transplant recipients were included. For the majority of serotypes, there was no significant increase in antibody levels after additional vaccination with the polysaccharide vaccine in both patient groups. When compared with the historical control group, the antibody response in lung transplant recipients 1 year after vaccination did not seem to have improved by vaccination with both vaccines instead of the polysaccharide vaccine alone.

Conclusions

Serologic vaccination responses in lung transplant candidates and recipients were not improved by giving a 23-valent pneumococcal polysaccharide vaccine after a 13-valent pneumococcal conjugate vaccine. The benefit of this vaccination schedule in lung transplant recipients seems to differ from other immunocompromised populations. The optimal vaccination schedule for lung transplant candidates and recipients remains to be determined.

Infant antibody levels following 10-valent pneumococcal-protein D conjugate and DTaP-Hib vaccinations in the first year of life after maternal Tdap vaccination: An open-label, parallel, randomised controlled trial

BACKGROUND

Maternal antibody levels after Tdap vaccination during pregnancy may affect infant primary antibody responses to pertussis, Tetanus toxoid (TT), Diphtheria toxoid (DT) vaccinations and pneumococcal vaccines with diphtheria toxin mutants like CRM197 as carrier protein.

METHODS

Mothers were recruited in an open label randomised parallel controlled trial in 2014-2016 through midwifes. They received Tdap [Boostrix] at 30-32 weeks of pregnancy (n = 58) or within 48 h after delivery (n = 60). Infants received DTaP-IPV-Hib-HepB [Infanrix Hexa] and 10-valent protein D conjugated pneumococcal conjugate vaccine (PHiD-CV10 [Synflorix]) at age 3, 5 and 11 months. We now report on infant specific IgG levels towards DT, TT, Haemophilus influenzae type b polyribosylribitol phosphate (Hib PRP) and PHiD-CV10 before and after primary- and booster vaccination as secondary study endpoints; pertussis antibodies were the primary endpoint of the study. This trial is registered in clinicaltrialsregister.eu (EudraCT 2012-004006-9) and trialregister.nl (NTR number NTR4314).

FINDINGS

Post primary vaccinations, antibody levels to DT, but not TT, were significantly lower after Tdap vaccination during pregnancy compared to controls (GMC ratio 0.4, 95% CI 0.3-0.6 and 0.9, 95% CI 0.6-1.2, respectively). Antibodies to serotype 19F were significantly lower in the maternal Tdap group, whereas there were no differences in antibody levels to Hib PRP and the other 9 pneumococcal serotypes. Post booster vaccinations, no significant differences were observed, except for DT.

INTERPRETATION

Maternal Tdap vaccination results in significant interference with infants responses not only to DT but also to conjugated pneumococcal vaccines containing DT mutants as carrier proteins. These interactions after maternal Tdap vaccination need to be taken into account when designing infants' national immunization schedules and choice of vaccines.

FUNDING

The Dutch Ministry of Health, Welfare and Sport.

Initiation of Antiretroviral Therapy Before Pregnancy Reduces the Risk of Infection-related Hospitalization in Human Immunodeficiency Virus-exposed Uninfected Infants Born in a High-income Country

BACKGROUND

Epidemiological studies conducted in low- and high-income countries showed that infants exposed to maternal human immunodeficiency virus (HIV) have a high risk of severe infections. Immune alterations during fetal life have been proposed as a possible mechanism.

METHODS

This prospective study assessed the relative risk of hospitalization for infection in HIV-exposed uninfected (HEU) infants as compared to HIV-unexposed (HU) infants born in a high-income country (HIC). Markers of monocyte activation and levels of pathogen-specific antibodies were measured at birth to identify correlates of infant susceptibility.

RESULTS

There were 27 of 132 HEU infants and 14 of 123 HU infants hospitalized for infection during the first year of life (adjusted hazard ratio [aHR] 2.33, 95% confidence interval [CI] 1.10-4.97). Most of this increased risk was associated with the time of initiation of maternal antiretroviral therapy (ART). As compared to HU infants, the risk of hospitalization for infection of HEU infants was 4-fold higher when mothers initiated ART during pregnancy (aHR 3.84, 95% CI 1.69-8.71) and was not significantly increased when ART was initiated before pregnancy (aHR 1.42, 95% CI 0.58-3.48). The activation of newborn monocytes and the reduced transfer of maternal antibodies were most intense following ART initiation during pregnancy, and predicted the risk of infant hospitalization.

CONCLUSIONS

These observations indicate that initiation of maternal ART before pregnancy reduces the susceptibility of HEU infants born in a HIC to severe infections, and that this effect could be related to the prevention of immune alterations during fetal life.

Multilaboratory Comparison of Pneumococcal Multiplex Immunoassays Used in Immunosurveillance of Streptococcus pneumoniae across Europe

Serology of Streptococcus pneumoniae is challenging due to existence of multiple clinically relevant serotypes and the introduction of multivalent vaccines in national immunization programs. Multiplex immunoassays (MIAs) are applied as high-throughput cost-effective methods for serosurveillance, and yet laboratories use their own protocols. The aims of this study were to assess the agreement of results generated by MIAs in different laboratories within the EU Pneumo Multiplex Assay Consortium, to analyze factors contributing to differences in outcome, and to create a harmonized protocol. The study demonstrated good agreement of results of MIAs performed by laboratories using controlled assays for determination of levels of vaccine-induced pneumococcal antibodies. The EU Pneumo Multiplex Assay Consortium is open to everyone working in public health services, and it aims to facilitate efforts by participants to run and maintain a cost-effective, reproducible, high-quality MIA platform.

Surveillance studies are required to estimate the impact of pneumococcal vaccination in both children and the elderly across Europe. The World Health Organization (WHO) recommends use of enzyme immunoassays (EIAs) as standard methods for immune surveillance of pneumococcal antibodies. However, as levels of antibodies to multiple serotypes are monitored in thousands of samples, a need for a less laborious and more flexible method has evolved. Fluorescent-bead-based multiplex immunoassays (MIAs) are suitable for this purpose. An increasing number of public health and diagnostic laboratories use MIAs, although the method is not standardized and no international quality assessment scheme exists. The EU Pneumo Multiplex Assay Consortium was initiated in 2013 to advance harmonization of MIAs and to create an international quality assessment scheme. In a multilaboratory comparison organized by the consortium, agreement among nine laboratories that used their own optimized MIA was assessed on a panel of 15 reference sera for 13 pneumococcal serotypes with the new WHO standard 007sp. Agreement was assessed in terms of assay accuracy, reproducibility, repeatability, precision, and bias. The results indicate that the evaluated MIAs are robust and reproducible for measurement of vaccine-induced antibody responses. However, some serotype-specific variability in the results was observed in comparisons of polysaccharides from different sources and of different conjugation methods, especially for serotype 4. On the basis of the results, the consortium has contributed to the harmonization of MIA protocols to improve reliability of immune surveillance of Streptococcus pneumoniae.

IMPORTANCE Serology of Streptococcus pneumoniae is challenging due to existence of multiple clinically relevant serotypes and the introduction of multivalent vaccines in national immunization programs. Multiplex immunoassays (MIAs) are applied as high-throughput cost-effective methods for serosurveillance, and yet laboratories use their own protocols. The aims of this study were to assess the agreement of results generated by MIAs in different laboratories within the EU Pneumo Multiplex Assay Consortium, to analyze factors contributing to differences in outcome, and to create a harmonized protocol. The study demonstrated good agreement of results of MIAs performed by laboratories using controlled assays for determination of levels of vaccine-induced pneumococcal antibodies. The EU Pneumo Multiplex Assay Consortium is open to everyone working in public health services, and it aims to facilitate efforts by participants to run and maintain a cost-effective, reproducible, high-quality MIA platform.

The Effect of Maternal Immunisation During Pregnancy on Infant Vaccine Responses

INTRODUCTION

Immunisation during pregnancy to protect infants against tetanus, pertussis and influenza is recommended in many countries. However, maternal antibodies can interfere with infant vaccine responses. We investigated the effect of antenatal diphtheria-tetanus-acellular pertussis (dTpa) and trivalent inactivated influenza (TIV) immunisation on specific and heterologous antibody responses to routine immunisations given in the first year of life.

METHODS

In total, 471 healthy infants were included. At 7 and 13 months of age, antibodies to the primary course of routine vaccines given at 6 weeks, 4 and 6 months of age (pertussis (pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN)), polio (type 1, 2, 3), Haemophilus influenzae type b (Hib), pneumococcus (serotype 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F)) were measured, and at 13 months of age, antibodies to the 12-month routine vaccines (Hib, meningococcus C, measles, mumps and rubella). The seroprotection rates for each vaccine and the geometric mean concentrations (GMC) of antibodies were compared between infants whose mothers did or did not receive dTpa or TIV immunisation during pregnancy.

RESULTS

A total of 369 infants were included in the final analysis. Maternal dTpa immunisation was associated with reduced antibody responses to both specific (diphtheria and pertussis) and heterologous (polio and pneumococcus) vaccine antigens. This effect was stronger for persistence of antibodies at 13 months of age than it was at 7 months of age. At 7 months of age, adjusted average antibody concentrations were significantly lower for diphtheria, pertussis (PT, FHA, PRN) and polio type 2, and at 13 months of age, for diphtheria, pertussis (PT, FHA, PRN), polio type 1-3 and pneumococcal serotypes 1, 4, 5, 6A, 6B, 7F, 18C and 23F. Additionally, at 13 months of age, seroprotection rates for diphtheria, PT, pneumococcal serotype 1, 6A and 6B were significantly lower in infants after maternal dTpa immunisation. In contrast, for Hib, in infants with maternal dTpa immunisation, the adjusted average antibody concentration and the seroprotection rate were higher, particularly at 7 months of age. Maternal TIV immunisation had minimal effect on infant vaccine responses.

CONCLUSION

Whilst maternal immunisation protects infants in the first few months of life, it might interfere with both specific and heterologous (unrelated) vaccines responses in infants.

RESEARCH IN CONTEXT

Evidence before this study: Maternal immunisation during pregnancy helps to protect infants during the period before they complete their primary immunisations. It has been proven to be safe and beneficial. However, pre-existing maternal antibodies can influence antibody responses following infant immunisation, an effect called 'blunting'. Previous studies have investigated the influence of dTpa but not influenza immunisation during pregnancy on infant vaccine responses. The majority of studies investigated antibody concentrations only to the specific vaccine antigens included in the maternal immunisation, and there is scarce data available on heterologous vaccine responses, particularly pneumococcal responses.Added value of this study: In this study, we have shown that maternal dTpa immunisation during pregnancy is associated with reduced antibody responses to both specific (diphtheria and pertussis) and heterologous (polio and pneumococcus) vaccine antigens. This effect is stronger for persistence of antibodies at 13 months of age than after primary immunisation at 7 months of age. In contrast, for Hib, in infants with maternal dTpa immunisation, antibody concentrations are higher, particularly at 7 months of age. Maternal TIV immunisation has minimal effect on infant vaccine responses.Implications of all the available evidence: Whilst maternal immunisation protects infants in the first few months of life, it might interfere with both specific and heterologous (unrelated) vaccines responses in infants. As most vaccines induce very high antibody responses, small differences in antibody concentrations may not be of clinical significance. However, since maternal immunisation during pregnancy also influences seroprotection rates, strategies, such as additional booster doses in the second year of life, particularly for pertussis and pneumococcus, might need to be considered to address this.

The influence of neonatal Bacille Calmette-Guérin (BCG) immunisation on heterologous vaccine responses in infants

INTRODUCTION

Bacillus Calmette-Guérin vaccine (BCG), one of the most widely used vaccines, does not only provide protection against tuberculosis and other mycobacterial infections, but also has non-specific (heterologous) immunomodulatory effects. In participants in a randomised trial, we investigated the effect of neonatal BCG immunisation on antibody responses to routine infant vaccines given in the first year of life.

METHODS

Antibodies against antigens in the diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type b (Hib), and the 13-valent pneumococcal conjugate vaccines were measured in 91 (45 BCG-vaccinated, 46 BCG-naïve) infants one month after, and in 310 (169 BCG-vaccinated, 141 BCG-naïve) infants seven months after immunisation at 6 weeks, 4 and 6 months of age. In addition, antibodies against meningococcus C, Hib, measles, mumps, and rubella were measured in 147 (78 BCG-vaccinated, 69 BCG-naïve) infants one month after immunisation at 12 months of age. The seroprotection rates for each vaccine and the geometric mean concentrations (GMC) of antibodies were compared in BCG-vaccinated and BCG-naïve infants.

RESULTS

At 7 months of age, seroprotection rates were high in both BCG-vaccinated and BCG-naïve infants. At 13 months of age, seroprotection rates were lower than at 7 months of age, particularly for pertussis and a number of pneumococcal antigens, with generally higher rates for the latter in BCG-vaccinated infants. Although not statistically significant, antibody responses in BCG-vaccinated infants were consistently higher against diphtheria, tetanus, and pneumococcal antigens at both 7 and 13 months of age, and against measles and mumps at 13 months of age, but were lower against Hib one month after immunisation at both 7 and 13 months of age.

CONCLUSION

The immunomodulatory effect of BCG on antibody responses to heterologous vaccines adds to the evidence that BCG immunisation at birth has broad heterologous effects on the infant immune system.

The immunomodulatory effects of measles-mumps-rubella vaccination on persistence of heterologous vaccine responses

It is proposed that measles-containing vaccines have immunomodulatory effects which include a reduction in all-cause childhood mortality. The antibody response to heterologous vaccines provides a means to explore these immunomodulatory effects. This is the first study to investigate the influence of measles-mumps-rubella (MMR) vaccine on the persistence of antibodies to a broad range of heterologous infant vaccinations given in the first year of life. In total, 319 children were included in the study. All infants received routine vaccinations at 6 weeks, 4 and 6 months of age. At 12 months of age, 212 children were vaccinated with MMR and Haemophilus influenzae type b-meningococcus C (Hib-MenC) vaccines while the remaining 99 children had not yet received these vaccines. In the MMR/Hib-MenC-vaccinated group, blood was taken 28 ± 14 days after receiving these vaccines. Antibodies against diphtheria, tetanus, pertussis [pertussis toxin (PT), filamentous hemagglutinin, pertactin], poliomyelitis (type 1, 2, 3) and 13 pneumococcal serotypes were measured. Seroprotection rates and geometric mean antibody concentrations were compared between MMR/MenC-Hib-vaccinated and MMR/MenC-Hib-naïve participants. In the final analysis, 311 children were included. Seroprotection rates were lower in MMR/Hib-MenC-vaccinated children against PT and pneumococcal serotype 19A. After adjustment for prespecified factors, MMR/Hib-MenC-vaccinated infants had significantly higher antibody concentrations against tetanus (likely explained by a boosting effect of the carrier protein, a tetanus toxoid), while for the other vaccine antigens there was no difference in antibody concentrations between the two groups. MMR vaccination given at 12 months of age in a developed country does not significantly influence antibody concentrations to heterologous vaccines received in the first year of life.

Antibody responses to Bordetella pertussis and other childhood vaccines in infants born to mothers who received pertussis vaccine in pregnancy - a prospective, observational cohort study from the United Kingdom

The maternal Tdap (tetanus, diphtheria and acellular pertussis) vaccination programme in the United Kingdom has successfully reduced cases of pertussis in young infants. In addition to prevention of pertussis cases, it is also important to investigate the persistence of maternal antibodies during infancy and the possible interference of maternal antibodies with infant responses to vaccines. We recruited mother–infant pairs from vaccinated and unvaccinated pregnancies and measured concentrations of immunoglobulin (Ig)G against pertussis toxin (PTx), filamentous haemagglutinin (FHA), pertactin (Prn), diphtheria toxin (DTx), tetanus toxoid (TTx) Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae in mothers and infants at birth, and in infants at 7 weeks and at 5 months. Thirty‐one mother–infant pairs were tested. Tdap‐vaccinated women had significantly higher antibody against Tdap antigens, compared to unvaccinated women (DTx, P = 0·01; PTx, FHA, Prn and TTx, P < 0·001). All antibodies were actively transferred to the infants (transfer ratio  > 1) with higher transfer of DTx (P = 0·04) and TTx (P = 0·02) antibody in Tdap‐vaccinated pregnancies compared to unvaccinated pregnancies. Infants from Tdap‐vaccinated pregnancies had significantly elevated antibodies to all antigens at birth (P < 0.001) and at 7 weeks (FHA, Prn, TTx, P < 0·001; DTx, P = 0.01; PTx, P = 0·004) compared to infants from unvaccinated pregnancies. Infants from Tdap‐vaccinated and ‐unvaccinated pregnancies had comparable antibody concentrations following primary pertussis immunization (PTx, P = 0·77; FHA, P = 0·58; Prn, P = 0·60; DTx, P = 0·09; TTx, P = 0·88). These results support maternal immunization as a method of protecting vulnerable infants during their first weeks of life.

Effect of Antibiotic-Mediated Microbiome Modulation on Rotavirus Vaccine Immunogenicity: A Human, Randomized-Control Proof-of-Concept Trial

Rotavirus vaccines (RVV) protect against childhood gastroenteritis caused by rotavirus (RV) but have decreased effectiveness in low- and middle-income settings. This proof-of-concept, randomized-controlled, open-label trial tested if microbiome modulation can improve RVV immunogenicity. Healthy adults were randomized and administered broad-spectrum (oral vancomycin, ciprofloxacin, metronidazole), narrow-spectrum (vancomycin), or no antibiotics and then vaccinated with RVV, 21 per group per protocol. Baseline anti-RV IgA was high in all subjects. Although antibiotics did not alter absolute anti-RV IgA titers, RVV immunogenicity was boosted at 7 days in the narrow-spectrum group. Further, antibiotics increased fecal shedding of RV while also rapidly altering gut bacterial beta diversity. Beta diversity associated with RVV immunogenicity boosting at day 7 and specific bacterial taxa that distinguish RVV boosters and RV shedders were identified. Despite the negative primary endpoint, this study demonstrates that microbiota modification alters the immune response to RVV and supports further exploration of microbiome manipulation to improve RVV immunogenicity.

Serotype-Specific IgG Antibody Waning after Pneumococcal Conjugate Primary Series Vaccinations with either the 10-Valent or the 13-Valent Vaccine

The two currently available ten- and thirteen-valent pneumococcal conjugate vaccines (PCV10 and PCV13) both induce serotype-specific IgG anti-polysaccharide antibodies and are effective in preventing vaccine serotype induced invasive pneumococcal disease (IPD) as well as in reducing overall vaccine-serotype carriage and transmission and thereby inducing herd protection in the whole population. IgG levels decline after vaccination and could become too low to prevent carriage acquisition and/or pneumococcal disease. We compared the levels of 10-valent (PCV10) and 13-valent (PCV13) pneumococcal vaccine induced serum IgG antibodies at multiple time points after primary vaccinations. Data from two separate studies both performed in the Netherlands in infants vaccinated at 2, 3, and 4 months of age with either PCV10 or PCV13 were compared. Antibody levels were measured at 5, 8, and 11 months of age, during the interval between the primary immunization series and the 11-months booster dose. Serotype-specific IgG levels were determined by multiplex immunoassay. Although antibody kinetics showed significant variation between serotypes and between vaccines for the majority of the 10 shared serotypes, i.e., 1, 5, 7F, 9V, 14, 18C, and 23F, antibody concentrations were sufficiently high for both vaccines, immediately after the primary series and throughout the whole period until the booster dose. In contrast, for serotypes 4 and 19F in the PCV10 group and for serotypes 4 and 6B in the PCV13 group, IgG antibody concentrations already come within reach of the frequently used seroprotection level of 0.35 μg/mL immediately after the primary series at the five month time point and/or at eight months. This paper addresses the importance of revealing differences in serotype-specific and pneumococcal vaccine-dependent IgG antibody patterns during the interval between the primary series and the booster dose, an age period with a high IPD incidence. Trial registration: www.trialregister.nl NTR3069 and NTR2316.

Development and Validation of 13-plex Luminex-Based Assay for Measuring Human Serum Antibodies to Streptococcus pneumoniae Capsular Polysaccharides

The pneumococcal enzyme-linked immunosorbent assay (ELISA) measures IgG antibodies in human serum, and it is an important assay that supports licensure of pneumococcal vaccines. The immune correlate of protection, 0.35 µg/ml of IgG antibodies, was determined by the ELISA method. Pfizer has developed a new Luminex-based assay platform to replace the ELISA. These papers describe the important work of (i) validating the Luminex-based assay and (ii) bridging the immune correlate of protection (0.35 µg/ml IgG) to equivalent values reported by the Luminex platform.

A Luminex-based direct immunoassay (dLIA) platform has been developed to replace the standardized pneumococcal enzyme-linked immunosorbent assay platform. The multiplex dLIA simultaneously measures the concentration of serum immunoglobulin G (IgG) antibodies specific for pneumococcal capsular polysaccharide (PnPS) serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F. The assay uses poly-l-lysine (PLL)-conjugated PnPS, chemically coupled to spectrally distinct Luminex microspheres. Assay validation experiments were performed using residual human serum samples obtained from 13-valent pneumococcal conjugate vaccine (13vPnC) clinical studies. Assay results are expressed as IgG antibody concentrations in micrograms per milliliter using the international reference serum, 007sp. The lower limit of quantitation (LLOQ) for all serotypes covered in the 13-plex dLIA fell within the range of 0.002 to 0.038 µg/ml serum IgG. The difference between the lower limit and upper limit of the assay range was >500-fold for all serotypes, and assay variability was <20% relative standard deviation (RSD) for all serotypes. IgG antibody measurements were shown to be serotype-specific (some cross-reactivity was observed only between the structurally related serotypes 6A and 6B as well as 19A and 19F), and no interference was observed between the serotypes when the assay was performed in the 13-plex format compared to the singleplex assays. The 13-plex dLIA platform developed by Pfizer Inc. generates up to 143 test results in a single 96-well plate and is a suitable replacement of the enzyme-linked immunosorbent assay (ELISA) platform for evaluating vaccine clinical trials.

IMPORTANCE The pneumococcal enzyme-linked immunosorbent assay (ELISA) measures IgG antibodies in human serum, and it is an important assay that supports licensure of pneumococcal vaccines. The immune correlate of protection, 0.35 µg/ml of IgG antibodies, was determined by the ELISA method. Pfizer has developed a new Luminex-based assay platform to replace the ELISA. These papers describe the important work of (i) validating the Luminex-based assay and (ii) bridging the immune correlate of protection (0.35 µg/ml IgG) to equivalent values reported by the Luminex platform.

Socioeconomic Status Is Associated With Antibody Levels Against Vaccine Preventable Diseases in the Netherlands

Background: We investigated whether low socioeconomic status (SES), which is associated with reduced health and life expectancy, might play a role in increased risk for infectious diseases. Therefore, we explored the association between SES and immunoglobulin G (IgG) levels against various pathogens.

Methods: We analyzed the association between SES [educational level and net household income (NHI)] and serum IgG concentration against measles, mumps, rubella, varicella, Haemophilus influenzae type B (HiB), pneumococcus, meningococcus serogroup C (MenC), and cytomegalovirus (CMV) collected within a national cross-sectional serosurvey (2006/2007) using linear regression analyses among non-vaccinated individuals.

Results: Higher educational level was associated with higher IgG concentrations against measles (GMC ratio 1.34, 95% CI 1.18–1.53) and rubella (1.13, 1.02–1.25) compared to low education level. In contrast, higher education level was associated with lower IgG concentrations against pneumococcus (0.78, 0.70–0.88), MenC (0.54, 0.44–0.68), and CMV (0.23, 0.18–0.31) compared to low education level. This pattern was also evident when NHI was used as SES indicator.

Conclusion: Our study suggests that socioeconomic status is associated with antibody levels in a pathogen-dependent manner. The results suggest that differences in serological response upon infection or differences in exposure might be involved in the variation in IgG levels between SES groups.

Development of an Extended-Specificity Multiplex Immunoassay for Detection of Streptococcus pneumoniae Serotype-Specific Antigen in Urine by Use of Human Monoclonal Antibodies

Current pneumococcal vaccines cover the 10 to 23 most common serotypes of the 92 presently described. However, with the increased usage of pneumococcal-serotype-based vaccines, the risk of serotype replacement and an increase in disease caused by nonvaccine serotypes remains. Serotype surveillance of pneumococcal infections relies heavily on culture techniques, which are known to be insensitive, particularly in cases of noninvasive disease. Pneumococcal-serotype-specific urine assays offer an alternative method of serotyping for both invasive and noninvasive disease. However, the assays described previously cover mainly conjugate vaccine serotypes, give little information about circulating nonvaccine serotypes, and are currently available only in one or two specialist laboratories. Our laboratory has developed a Luminex-based extended-range antigen capture assay to detect pneumococcal-serotype-specific antigens in urine samples. The assay targets 24 distinct serotypes/serogroups plus the cell wall polysaccharide (CWP) and some cross-reactive serotypes. We report that the assay is capable of detecting all the targeted serotypes and the CWP at 0.1 ng/ml, while some serotypes are detected at concentrations as low as 0.3 pg/ml. The analytical serotype specificity was determined to be 98.4% using a panel of polysaccharide-negative urine specimens spiked with nonpneumococcal bacterial antigens. We also report clinical sensitivities of 96.2% and specificities of 89.9% established using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease. This assay can be extended for testing other clinical samples and has the potential to greatly improve serotype-specific surveillance in the many cases of pneumococcal disease in which a culture is never obtained.

Safety and Immunogenicity of Malaria Vectored Vaccines Given with Routine Expanded Program on Immunization Vaccines in Gambian Infants and Neonates: A Randomized Controlled Trial

BACKGROUND

Heterologous prime-boost vaccination with chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) encoding multiple epitope string thrombospondin-related adhesion protein (ME-TRAP) has shown acceptable safety and promising immunogenicity in African adult and pediatric populations. If licensed, this vaccine could be given to infants receiving routine childhood immunizations. We therefore evaluated responses to ChAd63 MVA ME-TRAP when co-administered with routine Expanded Program on Immunization (EPI) vaccines.

METHODS

We enrolled 65 Gambian infants and neonates, aged 16, 8, or 1 week at first vaccination and randomized them to receive either ME-TRAP and EPI vaccines or EPI vaccines only. Safety was assessed by the description of vaccine-related adverse events (AEs). Immunogenicity was evaluated using IFNγ enzyme-linked immunospot, whole-blood flow cytometry, and anti-TRAP IgG ELISA. Serology was performed to confirm all infants achieved protective titers to EPI vaccines.

RESULTS

The vaccines were well tolerated in all age groups with no vaccine-related serious AEs. High-level TRAP-specific IgG and T cell responses were generated after boosting with MVA. CD8+ T cell responses, previously found to correlate with protection, were induced in all groups. Antibody responses to EPI vaccines were not altered significantly.

CONCLUSION

Malaria vectored prime-boost vaccines co-administered with routine childhood immunizations were well tolerated. Potent humoral and cellular immunity induced by ChAd63 MVA ME-TRAP did not reduce the immunogenicity of co-administered EPI vaccines, supporting further evaluation of this regimen in infant populations.

CLINICAL TRIAL REGISTRATION

The clinical trial was registered on http://Clinicaltrials.gov (NCT02083887) and the Pan-African Clinical Trials Registry (PACTR201402000749217).

Long-term Follow-up of Humoral Immune Status in Adult Lung Transplant Recipients

BACKGROUND

Lung transplant recipients have an increased risk for infections in the posttransplant period due to immunosuppressive therapy. Protection against infections can be achieved through vaccination, but the optimal vaccination schedule in lung transplant recipients is unknown. Data on long-term immunological follow up and vaccination responses after lung transplantation are scarce.

METHODS

Here we present long-term immunological follow up of a cohort of 55 lung transplant recipients. This includes detailed antibody responses after 23-valent pneumococcal polysaccharide vaccination (23vPPV).

RESULTS

All patients were vaccinated with 23vPPV before transplantation. Median follow-up after transplantation was 6.6 years (379 patient-years). After transplantation, there is a significant decrease of all immunoglobulins, IgG subclasses and pneumococcal polysaccharide antibodies. After the first year posttransplantation, there is a gradual increase of all immunoglobulins and IgG subclasses, but values were always significantly lower than in the pretransplant period. After a median of 4.4 years posttransplantation, patients were revaccinated with 23vPPV. The pneumococcal polysaccharide antibody response was impaired in 87% of patients (ie, antibody titer above cutoff and twofold increase between pre and postvaccination values for <70% of serotypes).

CONCLUSIONS

We found that impairment of humoral immunity was most outspoken in the first year after lung transplantation. Immunoglobulin levels remain decreased several years after transplantation and the response to pneumococcal polysaccharide vaccine was significantly lower posttransplantation compared to the pretransplantation response. However, most patients did show a partial response to vaccination. Based on our results, revaccination with pneumococcal vaccines after transplantation should be considered 1 year after transplantation.

IgG subclass deficiencies in children: Facts and fiction

The chance to analyse the four IgG subclasses arose with the publication of Terry and Fahey¹ . Since then, a lot of new information on the role of subclasses and their deficiency states in humans has been obtained. This review tries to analyse critically our current knowledge of subclass deficiencies in children.

Specific Antibody Deficiency: Controversies in Diagnosis and Management

Specific antibody deficiency (SAD) is a primary immunodeficiency disease characterized by normal immunoglobulins (Igs), IgA, IgM, total IgG, and IgG subclass levels, but with recurrent infection and diminished antibody responses to polysaccharide antigens following vaccination. There is a lack of consensus regarding the diagnosis and treatment of SAD, and its clinical significance is not well understood. Here, we discuss current evidence and challenges regarding the diagnosis and treatment of SAD. SAD is normally diagnosed by determining protective titers in response to the 23-valent pneumococcal polysaccharide vaccine. However, the definition of an adequate response to immunization remains controversial, including the magnitude of response and number of pneumococcal serotypes needed to determine a normal response. Confounding these issues, anti-polysaccharide antibody responses are age- and probably serotype dependent. Therapeutic strategies and options for patients with SAD are often based on clinical experience due to the lack of focused studies and absence of a robust case definition. The mainstay of therapy for patients with SAD is antibiotic prophylaxis. However, there is no consensus regarding the frequency and severity of infections warranting antibiotic prophylaxis and no standardized regimens and no studies of efficacy. Published expert guidelines and opinions have recommended IgG therapy, which are supported by observations from retrospective studies, although definitive data are lacking. In summary, there is currently a lack of evidence regarding the efficacy of therapeutic strategies for patients with SAD. We believe that it is best to approach each patient as an individual and progress through diagnostic and therapeutic interventions together with existing practice guidelines.

Long-term Clinical Outcome of Antibody Replacement Therapy in Humoral Immunodeficient Adults With Respiratory Tract Infections

In severe humoral immunodeficiency the indication for antibody replacement therapy (ART) is clear, and supported by several large studies. However, for milder forms of humoral immunodeficiency, the indication for ART is less clear. This is a retrospective cohort study of 87 adults with recurrent respiratory tract infections who received ART. The patients had severe or mild humoral immunodeficiency, and were followed up for a median of 62months. Infection frequency, pharmacy-registered antibiotics use and hospital admissions significantly decreased under ART compared to the year prior to starting ART (median 5.50 (anamnestically)-0.82 (physician-confirmed) infections/year, p<0.001; median 4.00-2.05antibioticscourses/year, p<0.001; mean 0.75-0.44hospitaladmissions/year, p=0.009). These beneficial effects of ART were seen in both severe and mild immunodeficiency. Bronchiectasis was present in 27 patients when ART was started, but was not associated with clinical outcomes. An increase in hospital admissions under ART, observed in some patients, was significantly associated with pulmonary emphysema and current smoking. In conclusion, this study shows that ART is a long-term effective therapy in adults with recurrent respiratory tract infections with severe as well as with milder forms of humoral immunodeficiency.

Hilaire AJ, Gerson DF. Novel polysaccharide-protein conjugates provide an immunogenic 13-valent pneumococcal conjugate vaccine for S. pneumoniae

Pneumonia remains the single leading cause of childhood death worldwide. Despite the commercial availability of multiple pneumococcal conjugate vaccines (PCVs), high dosage cost and supply shortages prevent PCV delivery to much of the developing world. The current work presents high-yield pneumococcal conjugates that are immunogenic in animals and suitable for use in human vaccine development. The 13-valent pneumococcal conjugate vaccine (PCV-13) investigated in this research incorporated serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F. Pneumococcal polysaccharides (PnPSs) and CRM₁₉₇ carrier protein were produced and purified in-house, and used to prepare PnPS-CRM conjugates using unique, cyanide-free, in vacuo glycation conjugation methods. In vitro characterization confirmed the generation of higher molecular weight PnPS-CRM conjugates low in free protein. In vivo animal studies were performed to compare PnuVax's PCV-13 to the commercially available PCV-13, Prevnar^®13 (Pfizer, USA). A boost dose was provided to all groups post-dose 1 at t = 14 days. Post-dose 2 results at t = 28 days showed that all 13 serotypes in PnuVax's PCV-13 were boostable. Per serotype IgG GMCs demonstrated that PnuVax's PCV-13 is immunogenic for all 13 serotypes, with 10 of the 13 serotypes statistically the same or higher than Prevnar^®13 post-dose 2. As a result, the novel polysaccharide-protein conjugates developed in this work are highly promising for use in human PCV development. The in vacuo conjugation technique applied in this work could also be readily adapted to develop many other conjugate vaccines.

Evaluation and Optimization of an ELISA Procedure to Quantify Antibodies Against Pneumococcal Polysaccharides Included in the 13-Valent Conjugate Vaccine

The 13-valent pneumococcal conjugate vaccine (PCV-13) is recommended for HIV-infected people, although its effectiveness in this population remains under evaluation. In this study, we describe the development, optimization, and analytical validation of an ELISA procedure to measure specific antibodies for the pneumococcal polysaccharide serotypes included in PCV13 vaccine, testing sera obtained from HIV-infected outpatients (n = 30) who received the vaccine. The protocol followed the last version of WHO guidelines, based on the new standard 007sp, with the modification of employing Statens Serum Institut (SSI) antigens. We supplied the assay performance validation in terms of sensitivity, reproducibility, precision and accuracy. In addition we detailed optimal antigen-coating concentrations and ELISA conditions common to all 13 serotypes, suitable for laboratories performing these assays in order to standardize the method. Our procedure showed reproducibility and reliability, making it a valid alternative for evaluating the response to pneumococcal serotypes included in PCV13 vaccine.

Serological Monitoring Is Key To Sustain Progress of the Maternal and Neonatal Tetanus Elimination Initiative

In this issue of Clinical and Vaccine Immunology, Scobie and colleagues (H. M. Scobie et al., Clin Vaccine Immunol 23:546-554, 2016, http://dx.doi.org/10.1128/CVI.00052-16) report a nationwide serosurvey of tetanus immunity in >2,000 Cambodian women of child-bearing age to monitor progress toward maternal and neonatal tetanus elimination. This commentary discusses vaccines as interventions for disease control, elimination, and eradication and emphasizes the importance of the tools needed to monitor the effectiveness of initiatives that deliver the vaccines programmatically.

The Challenge of Immunoglobulin-G Subclass Deficiency and Specific Polysaccharide Antibody Deficiency--a Dutch Pediatric Cohort Study

PURPOSE

Immunoglobulin(Ig)G-subclass deficiency and specific polysaccharide antibody deficiency (SPAD) are among the most frequent causes of recurrent respiratory infections in children. Little is known about their prevalence, clinical presentation and prognosis. No study has been published in a Western-European nor in a mainly non-tertiary cohort until now. Therefore, we performed this observational cohort study in children recruited from secondary and tertiary pediatric practices all over The Netherlands.

METHODS

Dutch pediatricians were monthly asked to report patients with IgG-subclass deficiency and/or SPAD. Demographic, clinical and laboratory characteristics were collected. Separate informed consent was asked from parents and children (≥ 12 years of age) for annual update of the medical status.

RESULTS

49 children with confirmed IgG-subclass deficiency and/or SPAD were included. The majority of children (69%) was reported by four (out of 12) secondary hospitals with a pediatric immunologist in the staff. 45 children had ≥ 1 low IgG-subclass level and 11 had SPAD. IgG2 deficiency was the most prevalent IgG-subclass deficiency (37/49;76%). 10% of these children already showed bronchiectasis. Two-thirds were male (33/49;67%, p = 0.015). From 10 years of age, only boys were left and only boys showed progressive immunodeficiency during follow-up (11/24; 46%).

CONCLUSIONS

This is the first Western-European mainly non-tertiary cohort of children with IgG-subclass deficiency and/or SPAD. The disease course is not always benign, especially in boys. Most children were reported and managed in secondary hospitals with a pediatric immunologist in the staff. To identify more patients, the awareness of these diseases among general pediatricians should increase.

Dynamics and Determinants of Pneumococcal Antibodies Specific against 13 Vaccine Serotypes in the Pre-Vaccination Era

Introduction

Introduction of pneumococcal conjugate vaccines (PCVs) for infants decreased overall invasive pneumococcal disease (IPD), while non-vaccine serotype IPD increased. To fully understand this serotype replacement, knowledge about serotype dynamics in the pre-vaccine era is needed. In addition to IPD surveillance and carriage studies, the serotype replacement can be investigated by serosurveillance studies. The current study compared the results of two Dutch serosurveillance studies conducted in 1995–1996 (PIENTER1) and 2006–2007 (PIENTER2).

Methods

Participants in these studies donated a blood sample and completed a questionnaire. Pneumococcal antibodies of serotypes included in PCV13 were measured with a fluorescent-bead based multiplex immunoassay. Geometric mean antibody concentrations (GMCs) and determinants of pneumococcal antibody levels were investigated.

Results

GMCs were higher in PIENTER2 for serotypes 1, 6A, 6B, 9V, 18C, 19F and 23F and lower for 3 and 5. Age, day care attendance, household size, vaccination coverage, and urbanisation rate were associated with pneumococcal antibodies in children. Education level, ethnicity, age, low vaccination coverage sample, urbanisation rate, and asthma/COPD were associated with pneumococcal antibodies in elderly. The determinants significantly associated with pneumococcal IgG were slightly different for the elderly in PIENTER1 compared to the elderly in PIENTER2.

Conclusion

Although most of the serotype antibody levels remained stable, some of the serotype-specific antibody levels varied during the pre-vaccine era, indicating that exposure of certain serotypes changes without interference of PCVs.

Direct Comparison of Immunogenicity Induced by 10- or 13-Valent Pneumococcal Conjugate Vaccine around the 11-Month Booster in Dutch Infants

BACKGROUND & AIMS

Since 2009/10, a 10- and a 13-valent pneumococcal conjugate vaccine (PCV) are available, but only the 10-valent vaccine is now being used for the children in the Netherlands. As the vaccines differ in number of serotypes, antigen concentration, and carrier proteins this study was designed to directly compare quantity and quality of the antibody responses induced by PCV10 and PCV13 before and after the 11-month booster.

METHODS

Dutch infants (n = 132) were immunized with either PCV10 or PCV13 and DTaP-IPV-Hib-HepB at the age of 2, 3, 4 and 11 months. Blood samples were collected pre-booster and post-booster at one week and one month post-booster for quantitative and qualitative immunogenicity against 13 pneumococcal serotypes, as well as quantitative immunogenicity against diphtheria, tetanus, pertussis and Haemophilus influenzae type b. We compared immunogenicity induced by PCV13 and PCV10 for their ten shared serotypes.

RESULTS

One month post-booster, pneumococcal serotype-specific IgG geometric mean concentrations (GMCs) for the PCV13 group were higher compared with the PCV10 group for six serotypes, although avidity was lower. Serotype 19F showed the most distinct difference in IgG and, in contrast to other serotypes, its avidity was higher in the PCV13 group. One week post-booster, opsonophagocytosis for serotype 19F did not differ significantly between the PCV10- and the PCV13 group.

CONCLUSION

Both PCV10 and PCV13 were immunogenic and induced a booster response. Compared to the PCV10 group, the PCV13 group showed higher levels for serotype 19F GMCs and avidity, pre- as well as post-booster, although opsonophagocytosis did not differ significantly between groups. In our study, avidity is not correlated to opsonophagocytotic activity (OPA) and correlations between IgG and OPA differ per serotype. Therefore, besides assays to determine IgG GMCs, assays to detect opsonophagocytotic activity, i.e., the actual killing of the pneumococcus, are important for PCV evaluation. How differences between the two vaccines relate to long-term protection requires further investigation.

TRIAL REGISTRATION

www.trialregister.nl NTR3069.

Immune Dysfunction in Children with CHARGE Syndrome: A Cross-Sectional Study

CHARGE syndrome is a variable, multiple congenital malformation syndrome. Patients with CHARGE syndrome have frequent infections that are presumed to be due to anatomical anomalies of the craniofacial region and upper airway, and cranial nerve problems resulting in swallowing difficulties and aspiration. The possible contribution of immunological abnormalities to these infections has not been systematically studied even though immune deficiencies have been described in patients with 22q11.2 deletion syndrome, a condition which shares remarkable clinical overlap with CHARGE syndrome. We assessed the frequency and nature of immune dysfunction in 24 children with genetically proven CHARGE syndrome. All patients, or their parents, completed a questionnaire on infectious history. Their immune system was extensively assessed through full blood counts, immunoglobulin levels, lymphocyte subpopulations, peripheral B- and T-cell differentiation, T-receptor excision circle (TREC) analysis, T-cell function, and vaccination responses. All CHARGE patients had a history of infections (often frequent), mainly otitis media and pneumonia, leading to frequent use of antibiotics and to hospital admissions. Decreased T-cell numbers were found in 12 (50%) patients, presumably caused by insufficient thymic output since TREC amounts were also diminished in CHARGE patients. Despite normal peripheral B-cell differentiation and immunoglobulin production in all patients, 83% of patients had insufficient antibody titers to one or more early childhood vaccinations. Based on our results, we recommend immunological evaluation of CHARGE patients with recurrent infections.

Response on Pneumococcal Vaccine in Preterm Infants After Neutral and Acidic Oligosaccharides Supplementation

BACKGROUND

Supplementation of oligosaccharides in premature infants was shown to influence the immune system. We determined the effect of combined short-chain galacto-oligosaccharides (scGOS), long-chain fructo-oligosaccharides (lcFOS) and pectin-derived acidic oligosaccharides (pAOS) on antibody concentrations after pneumococcal conjugate vaccination in very preterm infants.

METHODS

Very preterm infants with gestational age <32 weeks and/or birth weight <1500 g were randomized to receive enteral supplementation with scGOS/lcFOS/pAOS or placebo between days 3 and 30 of life. Blood samples were collected at birth, 5 and 12 months of age and compared with term samples from a Dutch cross-sectional population-based serosurveillance study. IgG antibody levels to pneumococcal capsular polysaccharides were determined by multiplex immunoassay.

RESULTS

In total, 113 preterm infants were included with similar baseline and nutritional characteristics in both groups. After 3 primary pneumococcal vaccinations, the scGOS/lcFOS/pAOS-group had lower GMC antibody concentrations (µg/mL; serotype 4: 1.53, 6B:0.25, 9V: 1.19, 14: 2.39, 18C: 1.88, 19F: 7.42, 23F: 0.72) than the placebo group (serotype 4: 3.29, 6B: 0.79, 9V:2.64, 14: 4.52, 18C: 3.13, 19F: 14.64, 23F: 1.88; all P < 0.05), but comparable with those in the term control group (serotype 4: 0.97, 6B: 0.32, 9V: 1.67, 14: 3.24, 18C: 2.03, 19F: 5.06, 23F: 0.59; all P > 0.05). After the booster vaccination at 11 months, antibody levels were no longer different between the two preterm groups.

CONCLUSION

Enteral supplementation of scGOS/lcFOS/pAOS has a regulatory effect on the response to conjugated polysaccharide pneumococcal vaccine with normalization of the enhanced responses in preterm infants toward levels similar to healthy term infants.

Differential B-cell memory around the 11-month booster in children vaccinated with a 10- or 13-valent pneumococcal conjugate vaccine

Infants vaccinated with the 10- or 13-valent pneumococcal conjugate vaccine at 2, 3, 4, and 11 months had similar serotype-specific immunoglobulin G levels and plasma cell frequencies against 4 shared serotypes around these boosters, but higher memory B-cell frequencies in the PCV13 group.

Background. Both the 10- and 13-valent pneumococcal conjugate vaccines (PCV10 and PCV13) induce immunological memory against Streptococcus pneumoniae infections caused by vaccine serotypes. In addition to comparing serum antibody levels, we investigated frequencies of serotype-specific plasma cells (PCs) and memory B-cells (Bmems) as potential predictors of long-term immunity around the booster vaccination at 11 months of age.

Methods. Infants were immunized with PCV10 or PCV13 at 2, 3, 4, and 11 months of age. Blood was collected before the 11-month booster or 7–9 days afterward. Serotype-specific immunoglobulin G (IgG) levels were determined in serum samples by multiplex immunoassay. Circulating specific PCs and Bmems against shared serotypes 1, 6B, 7F, and 19F and against PCV13 serotypes 6A and 19A were measured in peripheral blood mononuclear cells by enzyme-linked immunospot assay.

Results. No major differences in IgG levels and PC frequencies between groups were found for the 4 shared serotypes. Notably, PCV13 vaccination resulted in higher frequencies of Bmems than PCV10 vaccination, both before and after the booster dose, for all 4 shared serotypes except for serotype 1 postbooster. For PCV13-specific serotypes 6A and 19A, the IgG levels and frequencies of PCs and Bmems were higher in the PCV13 group, pre- and postbooster, except for PC frequencies prebooster.

Conclusions. Both PCVs are immunogenic and induce measurable IgG, PC, and Bmem booster responses at 11 months. Compared to PCV10, vaccination with PCV13 was associated with overall similar IgG levels and PC frequencies but with higher Bmem frequencies before and after the 11-month booster. The clinical implications of these results need further follow-up.

Clinical Trials Registration. NTR3069.

Infections in infants fed formula supplemented with bovine milk fat globule membranes

OBJECTIVES

Observational studies have shown that even in high-income countries formula-fed infants have a higher incidence of acute otitis media (AOM), and gastrointestinal and respiratory tract infections during the first year of life compared with breast-fed infants. We hypothesized that components of the milk fat globule membrane (MFGM) may be responsible for some of these differences and that supplementation with bovine MFGM would decrease the infectious morbidity in formula-fed infants.

METHODS

In a double-blind randomized controlled trial, 160 formula-fed infants received experimental formula (EF) supplemented with bovine MFGM (EF) or unsupplemented standard formula (SF) from <2 months until 6 months of age. A breast-fed reference group consisted of 80 infants. Disease symptoms, health care contacts, and medication were recorded by the parents until 12 months of age. Serum immunoglobulin G for 10 pneumococcal serotypes was analyzed at 6 months of age.

RESULTS

The cumulative incidence of AOM during the intervention was lower in the EF group than in the SF group (1% vs 9%, P = 0.034), and did not differ from the breast-fed reference group (0%, P = 1.0). The incidence (25% vs 43%, P = 0.021) and longitudinal prevalence (P = 0.012) of antipyretic use were significantly lower in the EF group than in the SF group. Serum immunoglobulin G concentrations against pneumococcal serotypes 1, 5, and 14 were lower in the EF group than in the SF group.

CONCLUSIONS

Supplementation of formula with bovine MFGM reduces the risk of AOM, decreases antipyretics use in formula-fed infants, and has immunomodulatory effects on humoral response against pneumococcus vaccine.

Detection and serotyping of pneumococci in community acquired pneumonia patients without culture using blood and urine samples

Background

Treatment of community acquired pneumonia (CAP) patients with antibiotics before laboratory-confirmed diagnosis leads to loss of knowledge on the causative bacterial pathogen. Therefore, an increasing number of pneumococcal infections is identified using non-culture based techniques. However, methods for serotyping directly on the clinical specimen remain scarce. Here we present three approaches for detection and serotyping of pneumococci using samples from patients with CAP.

Methods

The first approach is quantitative PCR (qPCR) analysis on blood samples (n = 211) followed by capsular sequence typing (CST) to identify the serotype. The second approach, a urinary antigen assay (n = 223), designated as inhibition multiplex immunoassay (IMIA), is based on Luminex technology targeting 14 serotypes. The third approach is a multiplex immunoassay (MIA) (n = 171) also based on Luminex technology which detects serologic antibody responses against 14 serotypes. The three alternative assays were performed on samples obtained from 309 adult hospitalized CAP patients in 2007–2010 and the results were compared with those obtained from conventional laboratory methods to detect pneumococcal CAP, i.e. blood cultures, sputum cultures and BinaxNOW® urinary antigen tests.

Results

Using qPCR, MIA and IMIA, we were able to detect the pneumococcus in samples of 56% more patients compared to conventional methods. Furthermore, we were able to assign a serotype to the infecting pneumococcus from samples of 25% of all CAP patients, using any of the three serotyping methods (CST, IMIA and MIA).

Conclusion

This study indicates the usefulness of additional molecular methods to conventional laboratory methods for the detection of pneumococcal pneumonia. Direct detection and subsequent serotyping on clinical samples will improve the accuracy of pneumococcal surveillance to monitor vaccine effectiveness.

Longitudinal evaluation of enteric protozoa in Haitian children by stool exam and multiplex serologic assay

Haitian children were monitored longitudinally in a filariasis study. Included were stool samples examined for Giardia intestinalis and Entamoeba histolytica cysts, and serum specimens analyzed for immunoglobulin G (IgG) responses to eight recombinant antigens from G. intestinalis (variant-specific surface protein [VSP1-VSP5]), E. histolytica (lectin adhesion molecule [LecA]), and Cryptosporidium parvum (17- and 27-kDa) using a multiplex bead assay. The IgG responses to VSP antigens peaked at 2 years of age and then diminished and were significantly lower (P < 0.002) in children > 4.5 years than in children < 4.5 years. The IgG responses to Cryptosporidium tended to increase with age. The IgG responses to LecA and VSP antigens and the prevalence of stools positive for cysts were significantly higher (P < 0.037 and P < 0.035, respectively) in the rainy season than in the dry season. The multiplex bead assay provides a powerful tool for analyzing serologic responses to multiple pathogens.

Specific antibody in IV immunoglobulin for postsplenectomy sepsis

OBJECTIVE

Overwhelming postsplenectomy infection progresses rapidly and shows unacceptably high mortality even when treated with optimal antibiotics. Recent reports have described beneficial effects of intravenous immunoglobulin in sepsis. However, the underlying mechanisms, especially the roles of the pathogen-specific antibody fraction in intravenous immunoglobulin, remain unclear. We investigated the effects of intravenous immunoglobulin on overwhelming postsplenectomy infection and the role of pathogen-specific antibody.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

University laboratory.

SUBJECTS

Male C57BL/6JJcl mice.

INTERVENTIONS

Mice underwent splenectomy or a sham operation at 8 weeks old. At 4 weeks after the operation, mice were injected intravenously with 106 colony-forming units pneumococcus. Intraperitoneal injection of 300 mg/kg IV immunoglobulins was conducted simultaneously with infection. Specific antibody-depleted IV immunoglobulin prepared using immunoprecipitation was also injected into the animals.

MEASUREMENTS AND MAIN RESULTS

IV immunoglobulin markedly improved splenectomized mice survival. Removal of pneumococcus-specific antibody canceled it completely. Fluorescence microscopy results indicated significantly increased phagocytosis of antibody-bound bacteria in the livers of splenectomized mice treated with intact IV immunoglobulins. Immunomodulation, including suppression of marginal zone B-cell activation, was induced by IV immunoglobulin.

CONCLUSIONS

IV immunoglobulin showed a significantly protective effect on overwhelming postsplenectomy infection via enhancement of specific antibody-mediated phagocytosis in the liver. Specific antibody, more than immunological modulation, is crucial for effects of IV immunoglobulin on overwhelming postsplenectomy infection.

Impact of analytical variability on clinical interpretation of multiplex pneumococcal serology assays

The response to pneumococcal vaccination can be used to assess a patient's humoral immune response to polysaccharide antigens. Multiplex assays measuring serotype-specific levels of pneumococcal antibodies are often used for this purpose, and clinical algorithms have been published to assist in the definition of an adequate immune response. We evaluated whether interlaboratory variability in multiplex pneumococcal serology assays would affect the clinical classification of the immune response. Specimens from 57 patients were analyzed at three reference laboratories with different multiplex assays to measure pneumococcal serology. Analytical correlation and clinical agreement in the classification of a patient's vaccination status by the three methods were compared. Although substantial variation in the quantitative antibody levels measured by different laboratories was seen, the qualitative classification of individual serologic results showed a high degree of agreement between labs and the ultimate classification of a patient as "protected" or "nonprotected" was the same for most patients. The majority of discordant classifications were driven by a systematic bias in results from one of the assays rather than by random error. These data suggest that the use of integrated assessments based on multiple serotypes can compensate for much of the analytical variability seen between laboratories. Knowledge of the analytical performance characteristics of a particular assay is most important when evaluating patients with results near clinical cut points.

No evidence for xenotropic murine leukemia-related virus infection in Sweden using internally controlled multiepitope suspension array serology

Many syndromes have a large number of differential diagnoses, a situation which calls for multiplex diagnostic systems. Myalgic encephalomyelitis (ME), also named chronic fatigue syndrome (CFS), is a common disease of unknown etiology. A mouse retrovirus, xenotropic murine leukemia-related virus (XMRV), was found in ME/CFS patients and blood donors, but this was not corroborated. However, the paucity of serological investigations on XMRV in humans prompted us to develop a serological assay which cover many aspects of XMRV antigenicity. It is a novel suspension array method, using a multiplex IgG assay with nine recombinant proteins from the env and gag genes of XMRV and 38 peptides based on known epitopes of vertebrate gammaretroviruses. IgG antibodies were sought in 520 blood donors and 85 ME/CFS patients and in positive- and negative-control sera from animals. We found no differences in seroreactivity between blood donors and ME/CFS patients for any of the antigens. This did not support an association between ME/CFS and XMRV infection. The multiplex serological system had several advantages: (i) biotinylated protein G allowed us to run both human and animal sera, which is essential because of a lack of XMRV-positive humans; (ii) a novel quality control was a pan-peptide positive-control rabbit serum; and (iii) synthetic XMRV Gag peptides with degenerate positions covering most of the variation of murine leukemia-like viruses did not give higher background than nondegenerate analogs. The principle may be used for creation of variant tolerant peptide serologies. Thus, our system allows rational large-scale serological assays with built-in quality control.

Development and characterization of a multiplex bead-based immunoassay to quantify pneumococcal capsular polysaccharide-specific antibodies

Enzyme-linked immunosorbent assay (ELISA), the traditional antibody quantification technique, has several limitations, especially when used to evaluate multivalent and/or infant vaccines. We have developed a multiplex bead-based antibody quantification assay (MBIA) to measure antibody response to multiple pneumococcal (Pn) serotypes (St) in a single assay. MBIA was compared with the WHO ELISA using a WHO panel of 12 international calibration sera for 7 Pn Sts. An agreement of 75 to 92% was obtained for all 7 Sts. MBIA exhibited good robustness, with the assay variability at ≤ 16%. A major contributor to MBIA variability was the cell wall polysaccharide (CWPs) content in Pn St-specific capsular Ps. This necessitated careful CWPs (20 μg/ml) preadsorption of sera. MBIA is specific, robust, and reproducible and offers high throughput. The use of MBIA will greatly reduce the cost and time required to evaluate the immune response to multiple Pn Sts and could help promote the licensure of future Pn and other multivalent vaccines.

Measurement of antibodies to pneumococcal, meningococcal and haemophilus polysaccharides, and tetanus and diphtheria toxoids using a 19-plexed assay

The measurement of antibody responses to vaccination is useful in the assessment of immune status in suspected immune deficiency. Previous reliance on enzyme-linked immunoabsorbent assays (ELISA) has been cumbersome, time-consuming and expensive. The availability of flow cytometry systems has led to the development of multiplexed assays enabling simultaneous measurement of antibodies to several antigens. We optimized a flow cytometric bead-based assay to measure IgG and IgM concentrations in serum to 19 antigens contained in groups of bacterial subunit vaccines: pneumococcal vaccines, meningococcal vaccines, Haemophilus influenzae b (Hib), and tetanus and diphtheria toxoid vaccines. 89-SF was employed as the standard serum. The assay was used to determine specific antibody levels in serum from 193 healthy adult donors. IgG and pneumococcal IgM antibody concentrations were measurable across 3 log10 ranges encompassing the threshold protective IgG antibody levels for each antigen. There was little interference between antibody measurements by the 19-plexed assay compared with monoplexed assays, and a lack of cross-reactive IgG antibody, but evidence for cross-reacting IgM antibody for 3/19 pneumococcal antigens. 90th centile values for 15/19 IgG concentrations and 12/12 IgM concentrations of the 193 adult sera were within these ranges and percentages of sera containing protective IgG antibody levels varied from 4% to 95% depending on antigen. This multiplexed assay can simultaneously measure antibody levels to 19 bacterial vaccine antigens. It is suitable for use in standard clinical practice to assess the in vivo immune response to test vaccinations and measure absolute antibody levels to these antigens.