Construction and evaluation of Bordetella pertussis live attenuated vaccine strain BPZE1 producing Fim3

Pertussis or whooping cough is currently the most prevalent vaccine-preventable childhood disease despite >85% global vaccination coverage. In recent years incidence has greatly increased in several high-income countries that have switched from the first-generation, whole-cell vaccine to the newer acellular vaccines, calling for improved vaccination strategies with better vaccines. We have developed a live attenuated pertussis vaccine candidate, called BPZE1, which is currently in clinical development. Unlike other pertussis vaccines, BPZE1 has been shown to provide strong protection against infection by the causative agent of pertussis, Bordetella pertussis, in non-human primates. BPZE1 is a derivative of the B. pertussis strain Tohama I, which produces serotype 2 (Fim2) but not serotype 3 fimbriae (Fim3). As immune responses to fimbriae are likely to contribute to protection, we constructed a BPZE1 derivative, called BPZE1f3, that produces both serotypes of fimbriae. Whereas nasal vaccination of mice with BPZE1 induced antibodies to Fim2 but not to Fim3, vaccination with BPZE1f3 elicited antibodies to both Fim2 and Fim3 at approximately the same level. In mice, both BPZE1 and BPZE1f3 provided equal levels of protection against clinical isolates that either produce Fim2 alone, both Fim2 and Fim3, or no fimbriae. However, vaccination with BPZE1f3 provided significantly stronger protection against Fim3-only producing B. pertussis than vaccination with BPZE1, indicating that immune responses to fimbriae contribute to serotype-specific protection against B. pertussis infection.     

Long-term immunity against pertussis induced by a single nasal administration of live attenuated B. pertussis BPZE1

Duration of vaccine-induced immunity plays a key role in the epidemiology and in the pattern of transmission of a vaccine-preventable disease. In the case of whooping cough, its re-emergence has been attributed, at least partly, to the waning of immunity conferred by current pertussis vaccines. We have recently developed a highly attenuated live vaccine, named BPZE1, which has been shown to be safe and to induce strong protective immunity against Bordetella pertussis infection in mice. In this study, we evaluated the long-term immunogenicity and protective efficacy induced by a single intranasal dose of BPZE1. Up to 1 year after immunization, BPZE1 showed significantly higher efficacy to protect adult and infant mice against B. pertussis infection than two administrations of an acellular pertussis vaccine (aPV). B. pertussis-specific antibodies were induced by live BPZE1 and by aPV, with increasing amounts during the first 6 months post-immunization before a progressive decline. Cell-mediated immunity was also measured 1 year after immunization and showed the presence of memory T cells in the spleen of BPZE1-immunized mice. Both cell-mediated and humoral immune responses were involved in the long-lasting protection induced by BPZE1, as demonstrated by adoptive transfer experiments to SCID mice. These data highlight the potential of the live attenuated BPZE1 candidate vaccine as part of a strategy to solve the problem of waning protective immunity against B. pertussis observed with the current aPV vaccines.     

Construction and evaluation of a pertactin-deficient live attenuated pertussis vaccine candidate BPZE1 derivative

Pertussis, mainly caused by Bordetella pertussis, is a severe respiratory disease that can be fatal, especially in young infants. Vaccines, massively implemented since the middle of the last century, have substantially reduced the pertussis incidence, but have not been able to fully control the disease. One of the shortcomings of current pertussis vaccines is their inability to prevent infection by and transmission of B. pertussis, in contrast to immunity following natural infection. We have developed the live attenuated nasal vaccine BPZE1 and have shown that it prevents both disease and B. pertussis infection in preclinical models. This vaccine is now in clinical development. However, the initial clinical studies have suggested that vaccine take is hampered by pre-existing antibodies to pertactin. Here, we have constructed a pertactin-deficient BPZE1 derivative called BPZE1P in order to overcome this limitation. BPZE1P colonized the murine respiratory tract as efficiently as BPZE1 and induced antibodies at levels similar to those elicited by BPZE1. In the presence of pre-existing antibodies induced by acellular pertussis vaccination, BPZE1P colonized the mouse respiratory tract more efficiently than BPZE1. Both vaccines protected equally well the murine lungs and noses from challenge with laboratory and clinical strains of B. pertussis, including pertactin-deficient strains, against which current acellular pertussis vaccines are less efficient. BPZE1P may thus be an interesting alternative to BPZE1 to overcome vaccine take limitations due to pre-existing antibodies to pertactin.     

Impact of maternally derived pertussis antibody titers on infant whole-cell pertussis vaccine response in a low income setting

BackgroundMaternal vaccines against pertussis are not yet recommended in the developing world. Besides unclear burden estimates, another concern is that transplacental transfer of maternal pertussis antibodies could result in attenuation of the immune response to whole cell pertussis (DTwP) primary vaccination series in infants. This study was taken up to determine whether higher levels of maternal pertussis antibodies attenuate immune response of infants to DTwP vaccination series given at 6–10–14 weeks of age.MethodologyA total of 261 pregnant women and their infants from four low-income settlements in Karachi, Pakistan were enrolled in this study. The study endpoints were infant antibody titers for Pertussis toxin (PTx), Filamentous hemagglutinin antigen (FHA), Pertactin (PRN) and Fimbriae type 2/3 (FIM) – from birth through 18 weeks of age. Cord blood or pre-vaccine pertussis antibody titers indicate the concentration of maternal antibodies transferred to infants. Linear regression models were used to determine the association between higher maternal antibody titers and infant immune response to DTwP vaccine. Geometric Mean Ratio (GMR) was calculated as the ratio of infant antibody titers at specified time points against the maternal antibody titers at the time of delivery.ResultsAt eighteen weeks of age, the adjusted β regression coefficient for PTx was 0.06 (95% CI: -0.49-0.61), FHA 0.02 (95% CI: -0.26 -0.29), PRN 0.02 (95%CI -0.38- 0.43), and FIM 0.17 (95%CI: -0.21-0.54). Among infants who received at least two doses of DTwP vaccine, higher maternal antibody titers did not have any attenuating effect on infant post-immunization antibody titers against all four pertussis antigens.ConclusionMaternal pertussis antibodies did not attenuate infant’s immune response to pertussis antigens in DTwP primary vaccine given at 6–10–14 weeks of age.     

Heterologous prime-boost immunization with live attenuated B. pertussis BPZE1 followed by acellular pertussis vaccine in mice

Pertussis is a severe and life-threatening infectious disease. Two successive generations of vaccines have strongly reduced its incidence over the last 70 years. However, despite excellent global vaccine coverage, it is still not under control and constitutes today the most frequent vaccine-preventable childhood disease. New vaccination approaches are therefore needed. Here, we provide preclinical proof of concept for a heterologous prime-boost strategy, using the live attenuated Bordetella pertussis vaccine candidate BPZE1 to prime infant and neonatal mice intranasally and a currently available acellular pertussis vaccine (aPV) as a booster. Intranasal vaccination with BPZE1 provided strong protection against challenge in neonatal mice, which could be boosted with a single dose of aPV. Furthermore, BPZE1 priming induced a strong Th1/Th17 response, which was maintained after repeated aPV administrations, in contrast to non-primed mice, in which aPV administrations resulted in Th2 skewing. In addition to T cell responses, intranasal administration of BPZE1 to infant or neonatal mice also primed antibody responses to B. pertussis antigens, with a strong preference of the IgG2a over the IgG1 isotypes, which was not seen in non-primed animals. Finally, neonatal BPZE1 priming strongly enhanced aPV-induced protection against B. pertussis challenge. These results lend support for a heterologous prime-boost strategy to control pertussis by using BPZE1 early in life and considering the current aPV administrations as booster vaccinations, thereby bridging the gap from birth to the first aPV immunizations and avoiding aPV-mediated Th2 skewing. A first-in-man clinical trial on BPZE1 has recently been successfully completed, which provides hope that these findings may be translated into human applications in the future.     

Characterization of the key antigenic components of pertussis vaccine based on outer membrane vesicles

Pertussis has resurged during the last two decades in different countries. In particular in the 2010–2013 period large outbreaks were detected in US, Australia, UK and The Netherlands with significant mortality in infants. The epidemiological situation of pertussis points out the need to develop new vaccines and in this regard we previously developed a new vaccine based on outer membrane vesicles (OMVs) which have been shown to be safe and to induce protection in mice. Here we have further investigated the properties of OMVs vaccines; in particular we studied the contribution of pertussis toxin (PTx) and pertactin (Prn) in OMVs-mediated protection against pertussis. PTx-deficient OMVs and Prn-deficient OMVs were obtained from defective Bordetella pertussis mutants. The absence of PTx or Prn did compromise the protective capacity of the OMVs formulated as Tdap vaccine. Whereas the protective efficacy of the PTx-deficient OMVs in mice was comparable to Prn-deficient OMVs, the protective capacity of both of them was significantly impaired when it was compared with the wild type OMVs. Interestingly, using OMVs obtained from a B. pertussis strain which does not express any of the virulence factors but expresses the avirulent phenotype; we observed that the protective ability of such OMVs was lower than that of OMVs obtained from virulent B. pertussis phase. However, it was surprising that although the protective capacity of avirulent OMVs was lower, they were still protective in the used mice model. These results allow us to hypothesize that OMVs from avirulent phase shares protective components with all OMVs assayed. Using an immune proteomic strategy we identified some common components that could play an important role in protection against pertussis.     

Characterization of the immune response induced by pertussis OMVs-based vaccine

For the development of a third generation of pertussis vaccine that could improve the control of the disease, it was proposed that the immune responses induced by the classic whole cell vaccine (wP) or after infection should be used as a reference point. We have recently identified a vaccine candidate based on outer membrane vesicles (OMVs) derived from the disease etiologic agent that have been shown to be safe and protective in mice model of infection. Here we characterized OMVs-mediated immunity and the safety of our new candidate. We also deepen the knowledge of the induced humoral response contribution in pertussis protection. Regarding the safety of the OMVs based vaccine (Tdap_OMVsBp,) the in vitro whole blood human assay here performed, showed that the low toxicity of OMVs-based vaccine previously detected in mice could be extended to human samples.Stimulation of splenocytes from immunized mice evidenced the presence of IFN-γ and IL-17-producing cells, indicated that OMVs induces both Th1 and Th17 response. Interestingly Tdap_OMVsBp-raised antibodies such as those induced by wP and commercial acellular vaccines (aP) which contribute to induce protection against Bordetella pertussis infection. As occurs with wP-induced antibodies, the TdapOMVsBp-induced serum antibodies efficiently opsonized B. pertussis. All the data here obtained shows that OMVs based vaccine is able to induce Th1/Th17 and Th2 mixed profile with robust humoral response involved in protection, positioning this candidate among the different possibilities to constitute the third generation of anti-pertussis vaccines.     

Bordetella pertussis iron regulated proteins as potential vaccine components

Bordetella pertussis is the etiologic agent of whooping cough, an illness whose incidence has been increasing over the last decades. Pertussis reemergence despite high vaccination coverage, together with the recent isolation of circulating strains deficient in some of the vaccine antigens, highlight the need for new vaccines. Proteins induced under physiological conditions, such as those required for nutrient acquisition during infection, might represent good targets for better preventive strategies. By mean of serological proteome analysis we identified two novel antigens of B. pertussis potentially involved in iron acquisition during host colonization. We had previously demonstrated that one of them, designated IRP1-3, is protective against pertussis infection in mice. In the present study, we show that the other antigen, named AfuA (BP1605), is a highly antigenic protein, exposed on the bacterial surface, conserved among clinical isolates and expressed during infection. Immunization of mice with the recombinant AfuA induced opsonophagocytic antibodies which could explain the protection against B. pertussis infection conferred by mice immunization with rAfuA. Importantly, we found that the addition of rAfuA and rIRP1-3 proteins to the commercial three pertussis components acellular vaccine significantly increased its protective activity. Taken together, our results point at these two antigens as potential components of a new generation of acellular vaccines     

Immunization with PCEP microparticles containing pertussis toxoid, CpG ODN and a synthetic innate defense regulator peptide induces protective immunity against pertussis

We investigated the efficacy of a novel microparticle (MP) based vaccine formulation consisting of pertussis toxoid (PTd), polyphosphazene (PCEP), CpG ODN 10101 and synthetic cationic innate defense regulator peptide 1002 (IDR) against Bordetella pertussis in mice. We studied whether encapsulation of these IDR-CpG ODN complexes into polyphosphazene-based microparticles further enhanced their immunomodulatory activity compared to soluble formulations containing PCEP (SOL), or without PCEP (AQ). In vitro stimulation of murine macrophages showed MP induced significantly higher levels of pro-inflammatory cytokines. When assessed in a B. pertussis infection challenge model, a single immunization with MP formulation led to significantly lower bacterial loads compared to other formulations and non-vaccinated animals. ELISPOT of splenocytes showed that MP group mice had significantly higher number of antigen-specific IL-17 secreting cells. The cytokine profile in lung homogenates of MP group mice after challenge showed significantly higher amounts of MCP-1, TNF-α, IFN-γ, IL-12 and IL-17 and significantly lowered IL-10 levels suggesting a strong Th1 shift. Protection was observed against challenge infection with B. pertussis. On the other hand protective immune responses elicited in Quadracel^® immunized mice were Th2 skewed. Hence, we conclude that formulation of PTd, PCEP, CpG ODN and IDR into MP generates a protective immune response in mice against pertussis emphasizing the potential of MP as a delivery vehicle for the potential development of single-shot vaccines.     

Adaptive immune response to whole cell pertussis vaccine reflects vaccine quality: A possible complementation to the Pertussis Serological Potency test

Whole cell Bordetella pertussis (wP) vaccines are still used in many countries to protect against the respiratory disease pertussis. The potency of whole-cell pertussis vaccine lots is determined by an intracerebral challenge test (the Kendrick test). This test is criticized due to lack of immunological relevance of the read-out after an intracerebral challenge with B. pertussis. The alternative in vivo test, which assesses specific antibody levels in serum after wP vaccination, is the Pertussis Serological Potency test (PSPT). Although the PSPT focuses on a parameter that contributes to protection, the protective immune mechanisms after wP vaccination includes more elements than specific antibody responses only. In this study, additional parameters were investigated, i.e. circulating pro-inflammatory cytokines, antibody specificity and T helper cell responses and it was evaluated whether they can be used as complementary readout parameters in the PSPT to assess wP lot quality. By deliberate manipulation of the vaccine preparation procedure, a panel of high, intermediate and low quality wP vaccines were made. The results revealed that these vaccines induced similar IL-6 and IP10 levels in serum 4 h after vaccination (innate responses) and similar antibody levels directed against the entire bacterium. In contrast, the induced antibody specificity to distinct wP antigens differed after vaccination with high, intermediate and low quality wP vaccines. In addition, the magnitude of wP-induced Th cell responses (Th17, Th1 and Th2) was reduced after vaccination with a wP vaccine of low quality. T cell responses and antibody specificity are therefore correlates of qualitative differences in the investigated vaccines, while the current parameter of the PSPT alone was not sensitive enough to distinguish between vaccines of different qualities. This study demonstrates that assessment of the magnitude of Th cell responses and the antigen specificity of antibodies induced by wP vaccination could form valuable complementary parameters to the PSPT.     

Will we have new pertussis vaccines?

Despite wide vaccination coverage with efficacious vaccines, pertussis is still not under control in any country. Two types of vaccines are available for the primary vaccination series, diphtheria/tetanus/whole-cell pertussis and diphtheria/tetanus/acellular pertussis vaccines, in addition to reduced antigen content vaccines recommended for booster vaccination. Using these vaccines, several strategies are being explored to counter the current pertussis problems, including repeated vaccination, cocoon vaccination and maternal immunization. With the exception of the latter, none have proven their effectiveness, and even maternal vaccination is not expected to ultimately control pertussis. Therefore, new pertussis vaccines are needed, and several candidates are in early pre-clinical development. They include whole-cell vaccines with low endotoxin content, outer membrane vesicles, new formulations, acellular vaccines with new adjuvants or additional antigens and live attenuated vaccines. The most advanced is the live attenuated nasal vaccine BPZE1. It provides strong protection in mice and non-human primates, is safe, even in immune compromised animals, and genetically stable after in vitro and in vivo passages. It also has interesting immunoregulatory properties without being immunosuppressive. It has successfully completed a first-in-man clinical trial, where it was found to be safe, able to transiently colonize the human respiratory tract and to induce immune responses in the colonized subjects. It is now undergoing further clinical development. As it is designed to reduce carriage and transmission of Bordetella pertussis, it may hopefully contribute to the ultimate control of pertussis.     

Effectiveness of the whole-cell pertussis vaccine produced in Poland against different Bordetella parapertussis isolates in the mouse intranasal challenge model

The aim of the study was to evaluate the effectiveness of the whole-cell pertussis vaccine produced locally and routinely used in Poland in the elimination of Bordetella parapertussis strains from the lungs and trachea of a mouse model. We found that the average protective effect against B. parapertussis in the lungs of mice immunized with the whole-cell pertussis vaccine (DTwP) was significantly higher than in animals immunized with the acellular pertussis vaccine (DTaP). The effectiveness of B. parapertussis elimination rates from the lungs of DTwP-immunized mice, depending on the strain used as a challenge, was found to be 1.2-3.0 times or 3.1-7.0 times lower than against Bordetella. pertussis Tohama I or vaccine B. pertussis 606/67 isolates, respectively. Our results show that the locally produced DTwP vaccine is able to protect against B. parapertussis isolates; however, the level of protection and course of B. parapertussis infection in the lungs and trachea seems to be strain specific.     

Pertussis vaccination during pregnancy in Belgium: Results of a prospective controlled cohort study

Vaccination during pregnancy has been recommended in some countries as a means to protect young infants from severe infection. Nevertheless, many aspects are still unknown and possible blunting of the infant's immune responses by maternal antibodies, is one of the concerns with maternal vaccination. We report the first prospective controlled cohort study in women and infants on the effects of using Boostrix^®, a combined tetanus, diphtheria and acellular pertussis vaccine, during pregnancy. The primary aim was to measure the influence of this booster dose on the titer and duration of the presence of maternal antibodies in the infants and assess possible interference with infant immune responses.In a controlled cohort study, 57 pregnant women were vaccinated with Tdap vaccine (Tetanus Diphtheria acellular Pertussis, Boostrix, GSK Biologicals), at a mean gestational age of 28.6 weeks. A control group of pregnant women (N = 42) received no vaccine. Antibody geometric mean concentrations (GMCs) against tetanus (TT), diphtheria (DT), pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (Prn) were measured with commercial ELISA tests in samples taken preceding maternal vaccination and one month afterwards, at delivery and from the cord blood, and in infants before and 1 month after the primary series of 3 pertussis containing hexavalent vaccines.Infants born to vaccinated women had significantly higher GMC at birth and during the first 2 months of life for all vaccine antigens compared to the offspring of unvaccinated women, thereby closing the susceptibility gap for pertussis in infants. However, blunting was noticed for infant diphtheria and pertussis toxin vaccine responses (p < 0.001) in the infants from vaccinated women after the primary vaccination schedule (weeks 8,12 and 16).Since pertussis vaccination has been recommended during pregnancy already, the results of this study support that recommendation and provide additional scientific evidence to document possible interference by maternal antibodies.     

Efficiency of placental transfer of vaccine-elicited antibodies relative to prenatal Tdap vaccination status

Administration of vaccines during pregnancy provides maternal protection against infectious diseases. This protection is extended to their infants during the first months of life, as pathogen-specific antibodies formed in response to maternal vaccination are transferred across the placenta to the fetus. Notably, Tdap (tetanus-diphtheria-acellular pertussis) vaccination booster is routinely administered to pregnant women both to prevent neonatal tetanus and to ensure that infants have protective levels of pertussis antibodies until they are able to establish their own vaccine-induced levels. Whether infant protection through maternal immunization is merely due to an increase in maternal antibody levels or whether maternal immunization enhances the transfer of vaccine-specific antibodies is unclear. Moreover, the potential impact of prenatal vaccinations on the transplacental transfer of other antibodies, such as antibodies raised as a result of infections or other vaccines administered prior to pregnancy, has not been studied.The goal of this study was to define the impact of maternal vaccination on IgG transplacental transfer efficiency. We analyzed antigen-specific antibody populations and IgG subclass distribution in maternal and cord blood samples from 58 mother-infant pairs. All women received the seasonal inactivated influenza vaccine during pregnancy and 25 women received the Tdap vaccine during the second or third trimester of gestation. Prenatal Tdap vaccination did not impact the efficiency of IgG transplacental transfer; however, it was associated with higher maternal and infant vaccine-elicited Tdap-specific antibody levels, and with a higher proportion of infants with protective levels of antibodies, especially against diphtheria. There was also no difference in the IgG transplacental transfer rate of antibodies against non-Tdap vaccines between the two groups of women. Our results confirm previous reports demonstrating the benefits of prenatal Tdap immunization and indicate that this strategy does not impede the transplacental transfer of other antibodies that are also important for infant protection.     

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

BackgroundMaternal 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.MethodsMothers 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).FindingsPost 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.InterpretationMaternal 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.FundingThe Dutch Ministry of Health, Welfare and Sport.     

CpG 1018® adjuvant enhances Tdap immune responses against Bordetella pertussis in mice

Bordetella pertussis is the causative agent of whooping cough (pertussis), a severe respiratory disease that can be fatal, particularly in infants. Despite high vaccine coverage, pertussis remains a problem because the currently used DTaP and Tdap vaccines do not completely prevent infection or transmission. It is well established that the alum adjuvant is a potential weakness of the acellular vaccines because the immunity provided by it is short-term. We aimed to evaluate the potential of CpG 1018® adjuvant to improve antibody responses and enhance protection against B. pertussis challenge in a murine model. A titrated range of Tdap vaccine doses were evaluated in order to best identify the adjuvant capability of CpG 1018. Antibody responses to pertussis toxin (PT), filamentous hemagglutinin (FHA), or the whole bacterium were increased due to the inclusion of CpG 1018. In B. pertussis intranasal challenge studies, we observed improved protection and bacterial clearance from the lower respiratory tract due to adding CpG 1018 to 1/20th the human dose of Tdap. Further, we determined that Tdap and Tdap + CpG 1018 were both capable of facilitating clearance of strains that do not express pertactin (PRN^-), which are rising in prevalence. Functional phenotyping of antibodies revealed that the inclusion of CpG 1018 induced more bacterial opsonization and antibodies of the Th1 phenotype (IgG2a and IgG2b). This study demonstrates the potential of adding CpG 1018 to Tdap to improve immunogenicity and protection against B. pertussis compared to the conventional, alum-only adjuvanted Tdap vaccine.     

Induction of Bordetella pertussis-specific immune memory by DTPa vaccines

Several vaccines are available against pertussis, differing by the number of Bordetella pertussis antigens that they contain as well as their formulation. The GlaxoSmithKline Biologicals (GSK Bio) tricomponent DTPa vaccine (DTPa3, Infanrix™), and the Sanofi-Pasteur (SP) five-component formulation (DTPa5, Pediacel™) were shown to have comparable short-term efficacy in clinical trials. However, potential differences in long-term protection were recently suggested, which might reflect the elicitation of different specific immune memory by the two vaccines. Therefore, the purpose of the present study was to investigate in mice the immune responses against B. pertussis, and particularly the establishment of specific B cell memory after immunization with DTPa3 and DTPa5 vaccines. Whereas intranasal challenge experiments showed similar protection with both vaccines, DTPa3 induced higher antibody levels to FHA and PRN than DTPa5. Further, the frequency of memory B cells was investigated by B cell ELISPOT. Higher frequencies of PT- and PRN-specific memory B cells were evidenced after vaccination with DTPa3, compared with DTPa5. Although the origin of such difference is unclear, the use of two different adjuvants (aluminum phosphate versus hydroxide) is proposed as a possible explanation. In conclusion, this study proposes that the induction of higher levels of B. pertussis antigen-specific memory B cells with DTPa3 participate to the suggested longer persistence of protection observed with this vaccine, as compared with DTPa5.     

Trivalent pneumococcal protein recombinant vaccine protects against lethal Streptococcus pneumoniae pneumonia and correlates with phagocytosis by neutrophils during early pathogenesis

ObjectiveDue to the fact that current polysaccharide-based pneumococcal vaccines have limited serotype coverage, protein-based vaccine candidates have been sought for over a decade to replace or complement current vaccines. We previously reported that a trivalent Pneumococcal Protein recombinant Vaccine (PPrV), showed protection against pneumonia and sepsis in an infant murine model. Here we investigated immunological correlates of protection of PPrV in the same model.MethodsC57BL/6J infant mice were intramuscularly vaccinated at age 1–3 weeks with 3 doses of PPrV, containing pneumococcal histidine triad protein D (PhtD), pneumococcal choline binding protein A (PcpA), and detoxified pneumolysin mutant PlyD1. 3–4 weeks after last vaccination, serum and lung antibody levels to PPrV components were measured, and mice were intranasally challenged with a lethal dose of Streptococcus pneumoniae (Spn) serotype 6A. Lung Spn bacterial burden, number of neutrophils and alveolar macrophages, phagocytosed Spn by granulocytes, and levels of cytokines and chemokines were determined at 6, 12, 24, and 48 h after challenge.ResultsPPrV vaccination conferred 83% protection against Spn challenge. Vaccinated mice had significantly elevated serum and lung antibody levels to three PPrV components. In the first stage of pathogenesis of Spn induced pneumonia (6–24 h after challenge), vaccinated mice had lower Spn bacterial lung burdens and more phagocytosed Spn in the granulocytes. PPrV vaccination led to lower levels of pro-inflammatory cytokines IL-6, IL-1β, and TFN-α, and other cytokines and chemokines (IL-12, IL-17, IFN-γ, MIP-1b, MIP-2 and KC, and G-CSF), presumably due to a lower lung bacterial burden.ConclusionTrivalent PPrV vaccination results in increased serum and lung antibody levels to the vaccine components, a reduction in Spn induced lethality, enhanced early clearance of Spn in lungs due to more rapid and thorough phagocytosis of Spn by neutrophils, and correspondingly a reduction in lung inflammation and tissue damage.     

Influenza subtype-specific maternal antibodies protect offspring against infection but inhibit vaccine-induced immunity and protection in mice

Following influenza A virus (IAV) infection or vaccination during pregnancy, maternal antibodies are transferred to offspring in utero and during lactation. The age and sex of offspring may differentially impact the transfer and effects of maternal immunity on offspring. To evaluate the effects of maternal IAV infection on immunity in offspring, we intranasally inoculated pregnant mice with sublethal doses of mouse-adapted (ma) H1N1, maH3N2, or media (mock) at embryonic day 10. In offspring of IAV-infected dams, maternal subtype-specific antibodies peaked at postnatal day (PND) 23, remained detectable through PND 50, and were undetectable by PND 105 in both sexes. When offspring were challenged with homologous IAV at PND 23, both male and female offspring had greater clearance of pulmonary virus and less morbidity and mortality than offspring from mock-inoculated dams. Inactivated influenza vaccination (IIV) against homologous IAV at PND 23 caused lower vaccine-induced antibody responses and protection following live virus challenge in offspring from IAV than mock-infected dams, with this effect being more pronounced among female than male offspring. At PND 105, there was no impact of maternal infection status, but vaccination induced greater antibody responses and protection against challenge in female than male offspring of both IAV-infected and mock-inoculated dams. To determine if maternal antibody or infection interfered with vaccine-induced immunity and protection in early life, offspring were vaccinated and challenged against a heterosubtypic IAV (i.e., different IAV group than dam) at PND 23 or 105. Heterosubtypic IAV maternal immunity did not affect antibody responses after IIV or protection after live IAV challenge of vaccinated offspring at either age. Subtype-specific maternal IAV antibodies, therefore, provide protection independent of offspring sex but interfere with vaccine-induced immunity and protection in offspring with more pronounced effects among females than males.     

Assessing the reactogenicity of Tdap vaccine administered during pregnancy and antibodies to Bordetella pertussis antigens in maternal and cord sera of Thai women

IntroductionPregnant Thai women have low antibody titers against B. pertussis antigens, which coincide with an increasing incidence of pertussis among Thai infants. Thus, there exists a potential benefit of a booster dose of tetanus- diphtheria-acellular pertussis (Tdap) vaccine administered during pregnancy. Here, we report the vaccine reactogenicity profile and birth outcomes in Tdap-vaccinated pregnant women who have or have not had prior immunization with tetanus vaccine, and the IgG levels to B. pertussis antigens in maternal and cord sera at delivery.Materials and methodsPregnant women (N = 370) aged 18–40 years were administered the Tdap vaccine (Boostrix®, GlaxoSmithKline, Rixensart, Belgium) at 26–36 weeks gestation. Adverse events following vaccination were identified by follow-up telephone call and medical record review. IgG against pertussis toxin (anti-PT), filamentous hemagglutinin (anti-FHA) and pertactin (anti-PRN) in both maternal and umbilical cord blood obtained at delivery were quantitatively evaluated using enzyme-linked immunosorbent assay (EUROIMMUN®, Lübeck, Germany).ResultsThere was no reported increase in the severity or duration of adverse events associated with the administration of an extra tetanus-containing vaccine within the previous five years (N = 181) or multiple doses of tetanus-containing vaccines during the current pregnancy (N = 98). Vaccination at least eight weeks prior to delivery resulted in high antibody titers to all B. pertussis antigens studied.ConclusionsThe reactogenicity of Tdap vaccine administered during pregnancy was not affected by prior tetanus toxoid immunization. High transplacental antibody against B. pertussis antigens in the cord blood provides evidence of antibody transfer and should thus help to protect newborns from pertussis during early life.