Development and validation of a robust multiplex serological assay to quantify antibodies specific to pertussis antigens

Determination of DTaP vaccine potency by multiplex immunogenicity testing using electrochemiluminescence

Lot release testing of diphtheria, tetanus and acellular pertussis vaccines traditionally relied on in vivo protection models involving challenge of laboratory animals with toxins. Meanwhile, many labs have switched to serological testing of these vaccines, which is often performed in separate in vivo assays, even if all components were formulated into one vaccine product. Here we describe the results of simultaneous serological potency determination of diphtheria (D), tetanus (T) and acellular pertussis (aP) antigens obtained following immunization of guinea pigs with multicomponent pediatric and booster vaccines from different manufacturers. The 4th World Health Organization (WHO) International Standard (IS) for diphtheria toxoid (No. 07/216) and the 4th WHO IS for tetanus toxoid (No. 08/218) were used as reference preparations. For aP, a pediatric vaccine batch containing the antigens pertussis toxoid, filamentous hemagglutinin, pertactin and fimbriae proteins type 2/3 was established as internal control. Quantification of IgG against D, T and aP antigens in guinea pig sera was performed using a hexaplex electrochemiluminescence immunoassay. We further provide proof-of-concept using experimental vaccine samples lacking or containing reduced amounts of diphtheria toxoid in the presence of full amounts of tetanus and pertussis antigens and alum adjuvant. Importantly, the assay confirmed dose-response relationships for all antigens tested and was able to detect diphtheria out-of-specification batches. The results confirmed the suitability of the protocol for combined serology batch release testing of DTaP combination vaccines as first measure towards implementation of full in vitro testing of DTaP vaccines. This report summarizes the data and the protocol used for validation prior to implementation of this method in routine batch release testing of DTaP vaccines, which led to replacement of in vivo challenge experiments in our laboratory following the 3 R (replace, reduce, refine) principle.

Quantitative analysis of pertussis, tetanus, and diphtheria antibodies in sera and breast milk from Tdap vaccinated women using a qualified multiplex assay

Pertussis (whooping cough) is a reemergent, highly contagious respiratory infection of public health concern. Infants prior to initiation of their primary vaccination series are the most vulnerable to severe infection, and even death. Vaccination during pregnancy is an efficacious means of reducing infection in infants. This approach relies on boosting maternal immunity and passive transfer of antibodies to the infant via placenta and breast milk. Similarly, maternal vaccination post-partum can enhance maternal-infant immunity. To support the analysis of pertussis immunity in the context of maternal-infant immunization, we developed a high throughput multiplex assay for simultaneous quantification of serum IgG antibodies against pertussis vaccine antigens: pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), and fimbriae (FIM2/3), and against tetanus (TT) and diphtheria toxoids (DT), using the Meso Scale Discovery (MSD) platform. The assay was qualified, and specificity, sensitivity, accuracy, precision, linearity, and robustness were demonstrated. The assay was subsequently adapted for quantification of IgG and IgA in breast milk. Applied to a serological survey of pregnant women living in the United States and sub-Saharan Africa, this method revealed differences in magnitude and breadth of antibody profile, consistent with history of vaccination. A longitudinal analysis of Tdap responses in women vaccinated post-partum demonstrated a rapid increase in serum IgG that remained elevated for up to 24 months. Likewise, high levels of vaccine-specific IgA and IgG antibodies were present in breast milk, although they exhibited faster decay. This multiplex MSD assay is a reliable and practical tool for quantification of pertussis, tetanus, and diphtheria antibodies in serum and breast milk in serosurveys or vaccine studies.

IMPORTANCE

Pertussis (whooping cough) has reemerged in recent years. Vaccination during pregnancy is an effective approach to prevent illness during the first months of life. We developed a multiplex assay for quantification of pertussis, tetanus, and diphtheria serum antibodies using the Meso Scale Discovery (MSD) platform; the method was qualified, and specificity, precision, accuracy, linearity, and limits of quantification were defined. It was also adapted for quantification of antibodies in breast milk. We successfully determined serostatus in women from different regions and with different vaccination histories, as well as responses to Tdap in blood and breast milk post-partum. This is the first description of a multiplex assay for the quantification of pertussis, tetanus, and diphtheria antibodies in breast milk.

Safety and immunogenicity of SIIPL Tdap, a new tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine, in healthy subjects 4-65 years of age: A Phase II/III randomized, observer-blinded, active controlled, multicenter clinical study in Germany

BACKGROUND

This study assessed the safety and immunogenicity of a new booster vaccine against tetanus, diphtheria, and pertussis manufactured by Serum Institute of India Pvt. Ltd (SIIPL Tdap).

METHODS

The Phase II/III trial was randomized (2:1), observer blinded and active controlled. Healthy subjects aged 4-65 years received a single dose of either SIIPL Tdap or comparator Tdap vaccine (Boostrix®, GlaxoSmithKline, Belgium), and were followed-up for 30 days. Blood samples for safety and immunogenicity assessments were collected pre-vaccination and on day 30 post-vaccination. The study assessed safety and reactogenicity of SIIPL Tdap compared to the comparator Tdap as well as the co-primary immunogenicity outcomes: (i) seroprotection rates against diphtheria toxoid (DT) and tetanus toxoid (TT) and (ii) the booster response rates against pertussis toxoid (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) 30 days post-vaccination in all study subjects. A margin of -10 % was used for non-inferiority testing. Secondary outcomes included the booster response rates against DT and TT, seropositivity rates against pertussis antigens, and antibody geometric mean concentrations (GMCs) for all vaccine components.

RESULTS

At Day 30 post-vaccination, SIIPL Tdap was assessed as non-inferior to the comparator Tdap in terms of: i) seroprotection rates against DT (94.4 % vs. 94.9 %) and TT (99.9 % vs. 100 %) and ii) pertussis booster response rates (93.8 % vs. 88.4 % anti-PT, 89.7 % vs. 90.9 % anti-FHA and 86.3 % vs. 84.4 % anti-PRN), for SIIPL Tdap versus comparator Tdap, respectively. GMCs for anti-PT and anti-PRN were higher in subjects vaccinated with SIIPL Tdap compared to comparator Tdap. All other secondary outcomes were comparable. The overall frequency of local and systemic solicited AEs was comparable; no treatment related SAEs were reported.

CONCLUSIONS

Booster vaccination with SIIPL Tdap was non-inferior to comparator Tdap with respect to the immunogenicity of the vaccine components and was equally well tolerated. EudraCT number: 2019-002706-46.

Multiplexed bead-based assay for the simultaneous quantification of human serum IgG antibodies to tetanus, diphtheria, pertussis toxin, filamentous hemagglutinin, and pertactin

Background

Luminex bead-based assays offer multiplexing to test antibodies against multiple antigens simultaneously; however, this requires validation using internationally certified reference standards. Therefore, there is an urgent need to characterize existing reference standards for the standardization of multiplex immunoassays (MIAs). Here, we report the development and validation of an MIA for the simultaneous estimation of levels of human serum immunoglobulin G (IgG) antibodies for pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), diphtheria toxoid (DT), and tetanus toxoid (TT).

Methods

The MIA was assessed using a panel of human serum samples and WHO reference standards. The WHO reference standards were also studied for suitability in the MIA. Purified antigens (PT, FHA, PRN, DT, and TT) were coupled to the spectrally unique magnetic carboxylated microspheres. The method was validated in accordance with the United States Food and Drug Administration (US FDA), European Medicines Agency (EMA), and the International Committee of Harmonization Multidisciplinary (ICH M10) guidelines, and parameters such as precision, accuracy, dilutional linearity, assay range, robustness, and stability were assessed. Method agreements with commercially available IgG enzyme-linked immunosorbent assay (ELISA) assays were also evaluated. In addition, the study assessed the level of correlation between the IgG levels estimated by the MIA and the cell-based neutralizing antibody assays for PT and DT.

Results

We identified that an equimix of WHO international standards (i.e., 06/142, 10/262, and TE-3) afforded the best dynamic range for all the antigens in the MIA. For all five antigens, we observed that the back-fitted recoveries using the four-parameter logistic (4-PL) regression fits ranged between 80% and 120% for all calibration levels, and the percentage coefficient of variation (% CV) was < 20%. In addition, the difference in mean fluorescence intensity (MFI) between the monoplex and multiplex format was < 10% for each antigen, indicating no crosstalk among the beads. The MIA also showed good agreement with conventional and commercially available assays, and a positive correlation (> 0.75) with toxin neutralization assays for PT and DT was observed.

Conclusion

The MIA that was calibrated in accordance with WHO reference standards demonstrated increased sensitivity, reproducibility, and high throughput capabilities, allowing for the design of robust studies that evaluate both natural and vaccine-induced immunity.

Maternal Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccination During Pregnancy: Impact on Infant Anti-Pertussis Antibody Concentrations by Maternal Pertussis Priming Series

BACKGROUND

Acellular pertussis (aP) vaccines replaced whole-cell pertussis (wP) vaccines for the US childhood primary series in 1997. As women primed with aP vaccines enter childbearing age, protection of infants through tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination during pregnancy may be impacted.

METHODS

Term infants born to women vaccinated with Tdap during pregnancy were included. Geometric mean concentrations (GMCs) of pertussis-specific immunoglobulin G antibodies (international units per milliliter) in cord blood of infants born to women born after 1997 (aP-primed) were compared with those born to women born before 1992 (wP-primed).

RESULTS

253 and 506 infants born to aP- and wP-primed women, respectively, were included. Compared with wP-primed women, aP-primed women were younger, more likely to be Hispanic or non-Hispanic Black, and had lower-birthweight infants (P < .01 for all). Antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) were lower among infants born to aP-primed vs wP-primed women (PT, 17.3 vs 36.4; GMC ratio, .475; 95% confidence interval [CI], .408-.552 and FHA, 104.6 vs 121.4; GMC ratio, 0.861; 95% CI, .776-.958). No differences were observed for anti-fimbriae or anti-pertactin antibodies.

CONCLUSIONS

Transplacental anti-pertussis antibody concentrations in infants of women vaccinated with Tdap during pregnancy differed by type of childhood vaccine the women received. Notably, anti-PT antibody levels, considered most important in preventing severe infant disease, were lower in infants born to aP-primed vs wP-primed women. Maternal Tdap vaccination may confer less protection against pertussis in infants born to aP-primed vs those born to wP-primed women.

Safety and immunogenicity of an indigenously developed tetanus toxoid, diphtheria toxoid, and acellular pertussis vaccine (Tdap) in adults, adolescents, and children in India

BACKGROUND

This study assessed safety and immunogenicity of Serum Institute of India Pvt Ltd (SIIPL)'s tetanus toxoid (TT), diphtheria toxoid (DT), and acellular pertussis booster vaccine (Tdap).

RESEARCH DESIGN AND METHODS

In this Phase II/III, multicenter, randomized, active-controlled, open-label study, 1500 healthy individuals, aged 4-65 years, were randomized to receive a single dose of SIIPL Tdap or comparator Tdap vaccine (Boostrix®; GlaxoSmithKlines, India). Adverse events (AEs) during initial 30 minutes, 7-day, 30-day post-vaccination were assessed. Blood samples were taken before and 30 days post-vaccination for immunogenicity assessment.

RESULTS

No significant differences in incidence of local and systemic solicited AEs were observed between the two groups; no vaccine-related serious AEs were reported. SIIPL Tdap was non-inferior to comparator Tdap in achieving booster responses to TT and DT in 75.2% and 70.8% of the participants, respectively, and to pertussis toxoid (PT), pertactin (PRN), and filamentous hemagglutinin (FHA) in 94.3%, 92.6%, and 95.0% of the participants, respectively. Anti-PT, anti-PRN, and anti-FHA antibody geometric mean titers in both the groups, were significantly higher post-vaccination compared to pre-vaccination.

CONCLUSIONS

Booster vaccination with SIIPL Tdap was non-inferior to comparator Tdap with respect to immunogenicity against tetanus, diphtheria, and pertussis and was well tolerated.

Safety and immunogenicity of live, attenuated intranasal Bordetella pertussis vaccine (BPZE1) in healthy adults

BACKGROUND

BPZE1 is a live, attenuated pertussis vaccine derived from B. pertussis strain Tohama I modified by genetic removal or inactivation of 3 B. pertussis toxins: pertussis toxin, dermonecrotic toxin, and tracheal cytotoxin. This Phase 2a study evaluated the safety and immunogenicity of liquid or lyophilized BPZE1 vaccine administered intranasally by needleless tuberculin syringe or mucosal atomization device (VaxINator^TM) at two dose levels.

METHODS

Fifty healthy male and non-pregnant female participants 18-49 years of age were enrolled. Participants were randomized 3:3:3:1 to a single lyophilized dose of 10⁷ colony forming units (CFU) BPZE1, 10⁹ CFU BPZE1, placebo via VaxINator device, or a single liquid dose of 10⁹ CFU BPZE1 via tuberculin syringe. Reactogenicity was assessed for 14 days. Blood was obtained pre-vaccination; on Day 8 (safety); and on Days 15, 29, and 181 (immunogenicity). Nasal wick and swab samples were obtained at baseline and on Days 29 and 181 for assessment of mucosal antibody responses and clearance of BPZE1.

RESULTS

Across all groups, 35/50 (70 %) experienced at least one local adverse event (AE) and 31/50 (62 %) experienced at least one systemic AE, with similar AE frequencies observed between the highest 10⁹ CFU BPZE1 and placebo groups. There were no severe or serious AEs during the study. At Day 29, seroconversion (≥2-fold rise from baseline in serum IgG or IgA) to at least 2 pertussis antigens was observed in 73 % in the 10⁹ CFU BPZE1 VaxINator group, 60 % in the 10⁹ CFU BPZE1 group delivered via tuberculin syringe, 27 % of participants in the 10⁷ CFU BPZE1 VaxINator group, and 20 % in the placebo VaxINator group. No participants were colonized with BPZE1 at Day 29 post vaccination.

DISCUSSION

Lyophilized BPZE1 vaccine was well tolerated and immunogenic at the highest dose (10⁹ CFU) delivered intranasally by VaxINator device and was not associated with any SAEs or prolonged shedding of BPZE1. Further evaluation of BPZE1 is warranted.

Effect of maternal Tdap on infant antibody response to a primary vaccination series with whole cell pertussis vaccine in São Paulo, Brazil

BACKGROUND

Maternal Tetanus, diphtheria, and acellular pertussis (Tdap) vaccination provides antibody transfer to newborn infants and may affect their antibody response to the primary vaccination series. This study aimed to assess the effect of Tdap vaccination during pregnancy on infant antibody response to the whole cell pertussis (DTwP) primary series.

METHODS

Plasma from 318 pregnant women (243 Tdap-vaccinated and 75 unvaccinated) and their infants (cord blood) was collected at delivery; infant blood was again collected at 2 and 7 months, before and after their primary DTwP series. Anti-pertussis toxin (PT), pertactin (PRN), filamentous hemagglutinin (FHA), fimbriae 2/3 (FIM) and adenylate cyclase toxin (ACT) IgG antibodies were quantified by a microsphere-based multiplex antibody capture assay and anti-PT neutralizing antibodies by the Real Time Cell analysis system.

RESULTS

Infant geometric mean concentrations (GMCs) of IgG anti-Tdap antigens were significantly higher (p < 0.001) among the Tdap-vaccinated (PT: 57.22 IU/mL; PRN: 464.86 IU/mL; FHA: 424.0 IU/mL), versus the unvaccinated group (4 IU/mL, 15.43 IU/mL, 31.99 IU/mL, respectively) at delivery. Anti-FIM and ACT GMCs were similar between the two groups. At 2 months of age, anti-PT, PRN, and FHA GMCs remained higher (p < 0.001) in the Tdap-vaccinated group (12.64 IU/mL; 108.76 IU/mL; 87.41 IU/mL, respectively) than the unvaccinated group (1.02 IU/mL; 4.46 IU/mL; 6.89 IU/mL). However, at 7 months, after receiving the third DTwP dose, the anti-PT GMC was higher (p = 0.016) in the unvaccinated group (7.91 IU/mL) compared to the vaccinated group (2.27 IU/mL), but without differences for anti-PRN, FHA, FIM and ACT GMCs.

CONCLUSION

Elevated antibody levels suggest that maternal Tdap vaccination might protect infants until 2 months of age. Reduced anti-PT levels at 7 months indicate potential blunting of immune response in infants. Surveillance would help determine if blunting alters vaccine immunity and impacts pertussis prevention in infants.

Kinetics of maternal pertussis-specific antibodies in infants of mothers vaccinated with tetanus, diphtheria and acellular pertussis (Tdap) during pregnancy

BACKGROUND

Kinetics of Tdap-induced maternally-derived antibodies in infants are poorly understood. Pre-Tdap era data suggest that maternal pertussis antibodies in infants have a half-life of approximately 5-6 weeks.

METHODS

34 mother-infant pairs had blood collected before maternal Tdap vaccination, 4 weeks later, at delivery (maternal and cord), and at infant ages 3 and 6 weeks from June 2014-March 2015. Immunoglobulin G (IgG) to pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbrial proteins (FIM) and pertactin (PRN) was quantified by multiplex luminex assay (IU/ml). Geometric mean concentrations (GMCs) with 95% confidence intervals (C.I.) and half-life of pertussis antibodies were calculated.

RESULTS

Tdap was administered to 34 women (mean age 31.1 years) at mean gestation 30.7 weeks (28-32.7). Mean neonatal gestation was 39.1 weeks (36-41.1) and mean birthweight was 3379 g (2580-4584). Four weeks post-Tdap vaccination, maternal pertussis-specific IgG GMCs increased ≥4-fold in 59%, 41%, 29% and 44% of women for PT, FHA, FIM and PRN, respectively, and then waned. The transplacental transport ratio of pertussis antibodies was 1.35 for PT, 1.41 for FHA, 1.31 for FIM and 1.36 for PRN. Between birth and age 6 weeks, infant serum GMC for PT-specific IgG decreased from 55.1 IU/mL (38.6-78.6) to 21.1 IU/ml (14.7-30.2), and the proportion of infants with PT levels ≥10 IU/ml fell from 97% to 67%. Half-life of pertussis-specific IgG in infants in days was 29.4 (95% CI 27.3-31.7) for PT, 29.8 (95% CI 27.7-32.2) for FHA, 31.2 (95% CI 28.9-33.7) for PRN, and 35.8 (95% CI 30.1-44.3) for FIM.

CONCLUSION

The half-life of pertussis-specific antibodies in infants induced by maternal Tdap vaccination (29-36 days) is shorter than previously reported. Understanding how the durability of passively-acquired antibodies impacts infant susceptibility to pertussis and response to primary vaccination is critical to refine prevention strategies.

Overcoming Waning Immunity in Pertussis Vaccines: Workshop of the National Institute of Allergy and Infectious Diseases

Despite high vaccine coverage in many parts of the world, pertussis is resurging in a number of areas in which acellular vaccines are the primary vaccine administered to infants and young children. This is attributed in part to the suboptimal and short-lived immunity elicited by acellular pertussis vaccines and to their inability to prevent nasal colonization and transmission of the etiologic agent Bordetella pertussis In response to this escalating public health concern, the National Institute of Allergy and Infectious Diseases held the workshop "Overcoming Waning Immunity in Pertussis Vaccines" in September 2019 to identify issues and possible solutions for the defects in immunity stimulated by acellular pertussis vaccines. Discussions covered aspects of the current problem, gaps in knowledge and possible paths forward. This review summarizes presentations and discussions of some of the key points that were raised by the workshop.

Multiplex Point-of-Care Tests for the Determination of Antibodies after Acellular Pertussis Vaccination

Most of the current serological diagnosis of pertussis is based on pertussis toxin (PT) IgG antibodies and does not differentiate between vaccination and infection-induced antibodies. PT is included in all of acellular pertussis vaccines available in the world. Multiplex testing of non-vaccine antigen-related antibodies has the potential to improve the diagnostic outcome of these assays. In this study, we developed a quantitatively spatial multiplex lateral flow immunoassay (LFIA) for the detection of IgG antibodies directed against PT, pertactin (PRN), and filamentous hemagglutinin (FHA). The assay was evaluated with serum samples with varying anti-PT, anti-PRN, and anti-FHA IgG levels and the result was compared to those obtained with standardized ELISA. The developed assay showed good specificity with PT and PRN antibodies and semiquantification throughout the antigen combinations. This exploratory study indicates that the multiplex LFIA is specific and sensitive, and a similar test platform with alternative antigens could be suitable for new type of pertussis serology.

A single immunogenicity assay for testing potency of combination DTaP vaccines: Simultaneous quantitation of anti-DT, anti-TT, anti-PTxd and anti-FHA antibodies in Guinea-pig serum with a Luminex®-xMAP® bead-based serological assay

The diphtheria toxoid (DT), tetanus toxoid (TT), and acellular pertussis (aP) single immunogenicity assay (DTaP SIA) is a Luminex®-xMAP®-bead-based multiplex immunoassay for estimating the potency of DTaP pediatric combination vaccines in guinea pigs. This manuscript describes the validation of this assay for the simultaneous quantitation of anti-diphtheria toxoid (anti-DT), anti-tetanus toxoid (anti-TT), anti-pertussis toxoid (anti-PTxd), and anti-filamentous hemagglutinin (anti-FHA) antibodies in guinea pig serum following injection of a DTaP vaccine formulation. The results were expressed in arbitrary units/mL (AU/mL) using reference serum for comparison. Specificity was demonstrated by ≥ 75% homologous and ≤25% heterologous inhibition for all the antigens. The results were linear for anti-DT, anti-TT, anti-PTxd and anti-FHA antibodies. Accuracy was demonstrated with recovery of between 80% and 120% for all four antibodies. The relative standard deviation of repeatability was ≤20%. The results demonstrate that this SIA can be used for the linear, accurate, and precise simultaneous detection of all four antibodies, based on both the ICH Q2 and the EMA guidelines on bioanalytical method validation.