Acellular Vaccine Research Articles

Development of a targeted nanoLC-MS/MS method for quantitation of residual toxins from Bordetella pertussis

Whooping cough is a highly contagious respiratory disease caused by Bordetella pertussis (B. pertussis) infection. Pertussis pathogenesis is driven by cell-surface adhesion proteins and secreted toxins; some of which have been harnessed for their immunogenic properties as purified antigen components in acellular vaccines. Two of these virulence factors, adenylate cyclase toxin (ACT) and dermonecrotic toxin (DNT), are protein toxins with potential for co-purification, and therefore must be monitored as process-related impurities during the development of acellular Pertussis vaccine candidates. Here we describe the development of a targeted nanoLC-MS/MS method for absolute quantitation of ACT and DNT in process intermediates from acellular Pertussis antigen purification. Starting from an in silico digest of the toxin sequences, a synthetic peptide screening approach was applied to systematically evaluate candidate sequences as surrogates for protein quantitation. Following refinement to a subset of sequences, absolutely quantified heavy-labelled (AQUA) peptides were implemented in a parallel reaction monitoring (PRM) workflow with limits of detection (LOD) and quantitation (LOQ) in the 12.5–25 amol (2−4 ng/mL) range on-column. In this work, we highlight a ‘standards-driven’ approach to surrogate peptide selection for protein quantitation. This strategy can be broadly applied in the absence of purified reference material and accelerate quantitative LC–MS method development across multiple sample matrices.

Evaluation of Poly(I:C) and combination of CpG ODN plus Montanide ISA adjuvants to enhance the efficacy of outer membrane vesicles as an acellular vaccine against Brucella melitensis infection in mice

Brucellosis is the most common zoonotic disease worldwide and still there is no vaccine for human use. The commercial animal vaccines also have major problems that limit their use. Therefore, there is a need for an effective Brucella vaccine which is multivalent and produces a good protective immunity with minimal disadvantages. Due to their heterogeneous composition and diverse functions, OMVs are promising acellular vaccine candidates against brucellosis. In the present study, the potential of Poly(I:C) or CpG ODN 1826+ Montanide ISA 70 VG adjuvant formulations were evaluated to enhance the immunity and protection levels conferred by OMVs against Brucella challenge in mice. The results indicated that both vaccine regimens were able to induce strong Th1-biased responses and confer protective levels significantly higher than REV.1 live vaccine. With regard to the results, it is concluded that OMVs in either adjuvant can be introduced as a new vaccine candidate against B. melitensis infection.

Combined RNAseq and ChIPseq Analyses of the BvgA Virulence Regulator of Bordetella pertussis.

Bordetella pertussis regulates the production of its virulence factors by the two-component system BvgAS. In the virulence phase, BvgS phosphorylates BvgA, which then activates the transcription of virulence-activated genes (vags). In the avirulence phase, such as during growth in the presence of MgSO4, BvgA is not phosphorylated and the vags are not expressed. Instead, a set of virulence-repressed genes (vrgs) is expressed. Here, we performed transcriptome sequencing (RNAseq) analyses on B. pertussis cultivated with or without MgSO4 and on a BvgA-deficient Tohama I derivative. We observed that 146 genes were less expressed under modulating conditions or in the BvgA-deficient strain than under the nonmodulating condition, while 130 genes were more expressed. Some of the genes code for proteins with regulatory functions, suggesting a BvgA/S regulation cascade. To determine which genes are directly regulated by BvgA, we performed chromatin immunoprecipitation sequencing (ChIPseq) analyses. We identified 148 BvgA-binding sites, 91 within putative promoter regions, 52 within open reading frames, and 5 in noncoding regions. Among the former, 32 are in BvgA-regulated putative promoter regions. Some vags, such as dnt and fhaL, contain no BvgA-binding site, suggesting indirect BvgA regulation. Unexpectedly, BvgA also bound to some vrg putative promoter regions. Together, these observations indicate an unrecognized complexity of BvgA/S biology.IMPORTANCE Bordetella pertussis, the etiological agent of whooping cough, remains a major global health problem. Despite the global usage of whole-cell vaccines since the 1950s and of acellular vaccines in the 1990s, it still is one of the most prevalent vaccine-preventable diseases in industrialized countries. Virulence of B. pertussis is controlled by BvgA/S, a two-component system responsible for upregulation of virulence-activated genes (vags) and downregulation of virulence-repressed genes (vrgs). By transcriptome sequencing (RNAseq) analyses, we identified more than 270 vags or vrgs, and chromatin immunoprecipitation sequencing (ChIPseq) analyses revealed 148 BvgA-binding sites, 91 within putative promoter regions, 52 within open reading frames, and 5 in noncoding regions. Some vags, such as dnt and fhaL, do not contain a BvgA-binding site, suggesting indirect regulation. In contrast, several vrgs and some genes not identified by RNAseq analyses under laboratory conditions contain strong BvgA-binding sites, indicating previously unappreciated complexities of BvgA/S biology.

Pertussis in the Voronezh Region: Epidemiology and Vaccination

Relevance. In recent years, the increase in the incidence of pertussis has been observed in many countries despite high vaccination coverage of the child population.Purpose: was to study the epidemiological features of whooping cough in the Voronezh region for the period from 2008 to 2018 years.Methods. The research material was data the annual form No. 2, 5, 6 of Rosstat for 2008 through 2018. Statistical data processing was performed using Microsoft Excel 2007.Results. The epidemiological features of pertussis in the Voronezh region for the period from 2008 to 2018 have been studied. Despite the high coverage of preventive vaccinations in children of the first years of life, in recent years, the incidence of pertussis increased the average Russian rates by 3,5 times. In the age structure of the diseased there was a tendency to increase the proportion of schoolchildren and adults. Analysis of the reports showed that half of the cases were vaccinated at the prescribed age, but the interval after vaccination before the illness was an average of 9 years.Conclusions. In recent years, there has been a tendency to an increase in the incidence of whooping cough in the Voronezh region. The incidence of vaccinated indicates the natural extinction of post-vaccination immunity to school age and requires a decision on the introduction of revaccination of schoolchildren with actual acellular vaccines.

Pertussis in the Voronezh Region: Epidemiology and Vaccination

Relevance. In recent years, the increase in the incidence of pertussis has been observed in many countries despite high vaccination coverage of the child population.Purpose: was to study the epidemiological features of whooping cough in the Voronezh region for the period from 2008 to 2018 years.Methods. The research material was data the annual form No. 2, 5, 6 of Rosstat for 2008 through 2018. Statistical data processing was performed using Microsoft Excel 2007.Results. The epidemiological features of pertussis in the Voronezh region for the period from 2008 to 2018 have been studied. Despite the high coverage of preventive vaccinations in children of the first years of life, in recent years, the incidence of pertussis increased the average Russian rates by 3,5 times. In the age structure of the diseased there was a tendency to increase the proportion of schoolchildren and adults. Analysis of the reports showed that half of the cases were vaccinated at the prescribed age, but the interval after vaccination before the illness was an average of 9 years.Conclusions. In recent years, there has been a tendency to an increase in the incidence of whooping cough in the Voronezh region. The incidence of vaccinated indicates the natural extinction of post-vaccination immunity to school age and requires a decision on the introduction of revaccination of schoolchildren with actual acellular vaccines.

Uncovering Distinct Primary Vaccination-Dependent Profiles in Human Bordetella Pertussis Specific CD4+ T-Cell Responses Using a Novel Whole Blood Assay.

To advance research and development of improved pertussis vaccines, new immunoassays are needed to qualify the outcome of Bordetella pertussis (Bp) specific CD4+ T-cell differentiation. Here, we applied a recently developed whole blood assay to evaluate Bp specific CD4+ T-cell responses. The assay is based on intracellular cytokine detection after overnight in vitro Bp antigen stimulation of diluted whole blood. We show for the first time that CD4+ T-cell memory of Th1, Th2, and Th17 lineages can be identified simultaneously in whole blood. Participants ranging from 7 to 70 years of age with different priming backgrounds of whole-cell pertussis (wP) and acellular pertussis (aP) vaccination were analyzed around an acellular booster vaccination. The assay allowed detection of low frequent antigen-specific CD4+ T-cells and revealed significantly elevated numbers of activated and cytokine-producing CD4+ T-cells, with a significant tendency to segregate recall responses based on primary vaccination background. A stronger Th2 response hallmarked an aP primed cohort compared to a wP primed cohort. In conclusion, analysis of Bp specific CD4+ T-cell responses in whole blood showed separation based on vaccination background and provides a promising tool to assess the quantity and quality of CD4+ T-cell responses induced by vaccine candidates.

Seroprevalence of antibodies against diphtheria, tetanus, and pertussis among healthy Thai adolescents

ObjectiveTo determine the seroprevalence of antibodies against of diphtheria, tetanus, and pertussis among Thai adolescents. MethodsA cross-sectional study was conducted among Thai adolescents aged 11–20 years who had completed five doses of diphtheria, tetanus, and pertussis (DTP)-containing vaccine during childhood, either diphtheria toxoid, tetanus toxoid, whole-cell pertussis (DTwP) or diphtheria toxoid, tetanus toxoid, acellular pertussis (DTaP) vaccine. Protective antibodies against diphtheria, tetanus, and pertussis were defined as anti-diphtheria toxoid IgG ≥0.1 IU/ml, anti-tetanus toxoid IgG ≥0.1 IU/ml, and anti-Bordetella pertussis toxin IgG ≥5 IU/ml, respectively. ResultsOf 220 adolescents (median age 16 years), 45% had received a tetanus toxoid, reduced diphtheria toxoid (Td) booster vaccine during adolescence, and none (0%) had received a tetanus toxoid, reduced diphtheria toxoid, acellular pertussis (Tdap) booster vaccine. Overall, 50%, 99%, and 57% of adolescents demonstrated protective antibodies against diphtheria, tetanus, and pertussis, respectively. The geometric mean concentrations (GMCs) of antibodies against diphtheria (p = 0.06) and tetanus (p < 0.001) were higher among adolescents who had received Td vaccine. Nevertheless, the antibody levels against both diseases waned over time, regardless of Td booster vaccination. Likewise, pertussis antibody levels gradually declined after the fifth childhood dose of DTwP/DTaP vaccine. ConclusionsApproximately half of these healthy Thai adolescents had not maintained protective antibodies against diphtheria and pertussis. A booster vaccination with diphtheria toxoid and/or acellular pertussis-containing vaccines is a crucial strategy to prevent such diseases in this population.

Neonatal Deficiencies in NK cell-Activating Cytokines in the Context of Bordetella pertussis Infection

Abstract Whooping cough, caused by Bordetella pertussis, has seen a resurgence in recent years, in part due to the switch from the whole cell to acellular vaccine. Although both adults and infants can suffer from severe paroxysmal cough, infants can experience a fatal health decline. Disease progression in infant and adult mouse models show some parallels to human disease. Adult mice exhibit severe lung pathology, but overcome infection, while infant mice experience mild lung pathology, develop leukocytosis, bacterial dissemination, and succumb to infection. We hypothesize that this discrepancy in response to infection is due to a deficiency in neonatal Interferon gamma (IFN-y) production by Natural Killer (NK) cells, which can activate protective T-helper 1 (Th1) cells. We further hypothesize that this deficiency is in part due to the inability of neonatal antigen presenting cells to produce the NK cell-activating cytokines Interleukin (IL) 12 and IL18 when exposed to B. pertussis. To test this hypothesis, we isolated splenocytes from infected and uninfected infant and adult mice, incubated with heat killed B. pertussis, and analyzed for mRNA expression of cytokines via qRT-PCR. While adult splenocytes responded robustly with upregulated expression of IL12 and TNF-α, infant splenocytes failed to upregulate expression of these cytokines in response to bacterial stimulation. Moreover, analysis of lung tissue from infected mice revealed robust upregulation of IL12, IL18 and TNF-α in adult mice but not in infant mice. These results indicate that infant mouse cells fail to upregulate expression of NK cell-activating cytokines in response to B. pertussis infection, leading to a lack of protective IFN-y responses.

A qPCR assay for Bordetella pertussis cells that enumerates both live and dead bacteria.

Bordetella pertussis is the causative agent of whooping cough, commonly referred to as pertussis. Although the incidence of pertussis was reduced through vaccination, during the last thirty years it has returned to high levels in a number of countries. This resurgence has been linked to the switch from the use of whole-cell to acellular vaccines. Protection afforded by acellular vaccines appears to be short-lived compared to that afforded by whole cell vaccines. In order to inform future vaccine improvement by identifying immune correlates of protection, a human challenge model of B. pertussis colonisation has been developed. Accurate measurement of colonisation status in this model has required development of a qPCR-based assay to enumerate B. pertussis in samples that distinguishes between viable and dead bacteria. Here we report the development of this assay and its performance in the quantification of B. pertussis from human challenge model samples. This assay has future utility in diagnostic labs and in research where a quantitative measure of both B. pertussis number and viability is required.

Factors Affecting the Implementation Process of Pertussis [Tdap] Immunization in Pregnant Women in an Italian Region: A Qualitative Study.

Whooping cough (pertussis) represents one of the most prevalent vaccine-preventable diseases in Western countries, capable of causing disease in infants, with a high risk of severe complications. To protect new-borns from pertussis, many countries have introduced the acellular pertussis adult vaccine in combination with tetanus and diphtheria toxoids for women in the third trimester of pregnancy. Thanks to the approval of the new National Immunization Prevention Plan 2017–2019: Italy is among those countries. The Italian health-care system is a regionally based National Health Service, therefore, regions organize and implement new vaccination strategy on their own. This study focuses on Tuscany's experience in implementing the maternal pertussis vaccination. The present study had a qualitative design: we obtained information about the implementation process through interviews with relevant stakeholders involved in the planning or implementation of vaccination programme at different levels. We noticed heterogeneous implementation's status between Tuscan Health Care Departments. The most frequently reported barriers influencing the success of the implementation process of this prevention strategy included: lack of accountability, lack of enabling instruments, financial constraints, logistics barriers, training deficiencies, attitudes of health care workers, and lack of communication experts. The implementation of new vaccination programs is complex and challenging. Often the importance of education and information activities targeting health professionals are underestimated and underfunded. These elements would need to be carefully considered and adequate provisions should be made to address them when designing and implementing effective vaccine interventions.

In silico identification and modification of T cell epitopes in pertussis antigens associated with tolerance

ABSTRACTThe resurgence of whooping cough since the introduction of acellular (protein) vaccines has led to a renewed interest in the development of improved pertussis vaccines; Outer Membrane Vesicles (OMVs) carrying pertussis antigens have emerged as viable candidates. An in silico immunogenicity screen was carried out on 49 well-known Bordetella pertussis proteins in order to better understand their potential role toward the efficacy of pertussis OMVs for vaccine design; seven proteins were identified as being good candidates for including in optimized cellular and acellular pertussis vaccines. We then screened these antigens for putative tolerance-inducing sequences, as proteins with reduced tolerogenicity have improved vaccine potency in preclinical models. We used specialized homology tools (JanusMatrix) to identify peptides in the proteins that were cross-reactive with human sequences. Four of the 19 identified cross-reactive peptides were detolerized in silico using a separate tool, OptiMatrix, which disrupted the potential of these peptides to bind to human HLA and murine MHC. Four selected cross-reactive peptides and their detolerized variants were synthesized and their binding to a set of eight common HLA class II alleles was assessed in vitro. Reduced binding affinity to HLA class II was observed for the detolerized variants compared to the wild-type peptides, highlighting the potential of this approach for designing more efficacious pertussis vaccines.

Differences in epitope-specific antibodies to pertussis toxin after infection and acellular vaccinations.

ObjectivesPertussis toxin (PT) is a component of all acellular pertussis vaccines. PT must be detoxified to be included in acellular vaccines, which results in conformational changes in the functional epitopes of PTs. Therefore, induced epitope‐specific antibodies to PT may vary after vaccinations or natural infections, and this information could reveal biomarkers implicated for protection and successful immunisation.MethodsPertussis toxin epitope‐specific antibodies in sera from 152 vaccinated children and 72 serologically confirmed patients were tested with a blocking ELISA, based on monoclonal antibodies that target protective PT epitopes.ResultsAll study groups induced considerable antibody titres to subunit 1 (S1). Of interest, S3 7E10‐specific antibodies were present in patients, but not after vaccinations (P < 0.001). The impact of glutaraldehyde treatment of PT was visible on epitope 1D7 (S1), whereas epitopes 1B7 (S1) and 10D (S1) were more preserved. Antibodies to these epitopes were higher after three primary vaccine doses than after a single booster dose.ConclusionThe high amount of 7E10‐specific antibodies in patients suggests this epitope might be functionally relevant in protection. The overall characteristics of epitope‐specific antibodies are influenced by infection or vaccination background, by the used detoxification method of PT and by the amount of the toxin used in immunisation.

Causes Of Pertussis Incidence Increase

Abstract Bordetella pertussis is an etiological factor of whooping cough. Despite global vaccination programs, this disease remains endemic in many countries and is still recognized as a significant public health problem. It is estimated that in 2014, around 24 million people worldwide contracted pertussis, of whom 160,700 children under the age of 5 died. Two types of pertussis vaccines are available: suspensions based on whole, killed, B. pertussis cells and acellular pertussis vaccines containing highly purified bacterial antigens. Due to concerns of potential neurological side effects of the whole-cell vaccines, less reactogenic acellular vaccines are now more commonly used. In recent years, many developed countries have reported a resurgence of pertussis disease despite of the high vaccine coverage. Several causes have been suggested for the re-emergence of pertussis including waning immunity and bacterial adaptation resulting from the selection pressure of the used vaccinations. 1. Introduction. 2. Virulence factors of Bordetella pertussis. 3. Pathogenesis of pertussis infection. 4. Clinical symptoms of pertussis. 5. Epidemiology. 6. Genetic variation in Bordetella pertussis. 7. Whole-cell pertussis vaccines. 8. Acellular pertussis vaccines. 9. Future pertussis vaccines. 10. Summary

Proteomic Analysis of Membrane Blebs of Brucella abortus 2308 and RB51 and Their Evaluation as an Acellular Vaccine.

Membrane blebs are released from Gram-negative bacteria, however, little is known about Brucella blebs. This work pursued two objectives, the first was to determine and identify the proteins in the membrane blebs by proteomics and in silico analysis. The second aim was to evaluate the use of membrane blebs of Brucella abortus 2308 and B. abortus RB51 as an acellular vaccine in vivo and in vitro. To achieve these aims, membrane blebs from B. abortus 2308 and RB51 were obtained and then analyzed by liquid chromatography coupled to mass spectrometry. Brucella membrane blebs were used as a “vaccine” to induce an immune response in BALB/c mice, using the strain B. abortus RB51 as a positive vaccine control. After subsequent challenge with B. abortus 2308, CFUs in spleens were determined; and immunoglobulins IgG1 and IgG2a were measured in murine serum by ELISA. Also, activation and costimulatory molecules induced by membrane blebs were analyzed in splenocytes by flow cytometry. Two hundred and twenty eight proteins were identified in 2308 membrane blebs and 171 in RB51 blebs, some of them are well-known Brucella immunogens such as SodC, Omp2b, Omp2a, Omp10, Omp16, and Omp19. Mice immunized with membrane blebs from rough or smooth B. abortus induced similar protective immune responses as well as the vaccine B. abortus RB51 after the challenge with virulent strain B. abortus 2308 (P < 0.05). The levels of IgG2a in mice vaccinated with 2308 membrane blebs were higher than those vaccinated with RB51 membrane blebs or B. abortus RB51 post-boosting. Moreover, mice immunized with 2308 blebs increased the percentage of activated B cells (CD19+CD69+) in vitro. Therefore, membrane blebs are potential candidates for the development of an acellular vaccine against brucellosis, especially those derived from the rough strains so that serological diagnostic is not affected.

Surfaceome analysis of Australian epidemic Bordetella pertussis reveals potential vaccine antigens

Since acellular vaccines (ACV) were introduced in Australia, epidemic Bordetella pertussis strains changed from single nucleotide polymorphism (SNP) cluster II to SNP cluster I. Our previous proteomic analysis identified potential proteomic adaptations in the whole cell and secretome of SNP cluster I. Additionally, current ACVs were shown to be less efficacious against cluster I in mice models and there is a pressing need to discover new antigens to improve the ACV. One important source of novel antigens is the surfaceome. Therefore, in this study we established surface shaving in B. pertussis to compare the surfaceome of SNP cluster I (L1423) and II (L1191), and identify novel surface antigens for vaccine development. Surface shaving using 1 μg of trypsin for 5 min identified 126 proteins with the most abundant being virulence-associated and known outer membrane proteins. Cell viability counts showed minimal lysis from shaving. The proportion of immunogenic proteins was higher in the surfaceome than in the whole cell and secretome. Key differences in the surfaceome were identified between SNP cluster I and II, consistent with those identified in the whole cell proteome and secretome. These differences include unique transport proteins and decreased immunogenic proteins in L1423, and provides further evidence of proteomic adaptation in SNP cluster I. Finally, a comparison of proteins in each sub-proteome identified 22 common proteins. These included 11 virulence proteins (Prn, PtxA, FhaB, CyaA, TcfA, SphB1, Vag8, BrkA, BopD, Bsp22 and BipA) and 11 housekeeping proteins (TuF, CtpA, TsF, OmpH, GltA, SucC, SucD, FusA, GroEL, BP3330 and BP3561) which were immunogenic, essential and consistently expressed thus demonstrating their potential as future targets. This study established surface shaving in B. pertussis, confirmed key expression differences and identified unknown surface proteins which may be potential vaccine antigens.

Rare Detection of Bordetella pertussis Pertactin-Deficient Strains in Argentina.

Pertussis resurgence had been attributed to waning vaccine immunity and Bordetella pertussis adaptation to escape vaccine-induced immunity. Circulating bacteria differ genotypically from strains used in production of pertussis vaccine. Pertactin-deficient strains are highly prevalent in countries that use acellular vaccine (aP), suggesting strong aP-imposed selection of circulating bacteria. To corroborate this hypothesis, systematic studies on pertactin prevalence of infection in countries using whole-cell vaccine are needed. We provide pertussis epidemiologic data and molecular characterization of B. pertussis isolates from Buenos Aires, Argentina, during 2000–2017. This area used primary vaccination with whole-cell vaccine. Since 2002, pertussis case incidences increased at regular 4-year outbreaks; most cases were in infants <1 year of age. Of the B. pertussis isolates analyzed, 90.6% (317/350) contained the ptxP3-ptxA1-prn2-fim3-2 allelic profile. Immunoblotting and sequencing techniques detected only the 2 pertactin-deficient isolates. The low prevalence of pertactin-deficient strains in Argentina suggests that loss of pertactin gene expression might be driven by aP vaccine.

Papel del estado de portador en el control de enfermedades infecciosas y su relación con la vacunación

El reservorio natural de Streptococcus pneumoniae, Neisseria meningitidis y Bordetella pertussis es el ser humano. De este modo, en caso de disponer de vacunas efectivas que impidieran la colonización por estas bacterias se podría interrumpir su transmisión. La respuesta inmune frente a los antígenos capsulares de Streptococcus pneumoniae condiciona el estado de portador de los diferentes serotipos. La vacuna neumocócica polisacárida 23 valente (PPV23) induce una respuesta inmune T independiente que es de corta duración y no previene la colonización. Por el contrario las vacunas conjugadas 10 valente (PCV10V) y 13 valente (PCV13) generan una inmunidad T dependiente que si reduce la colonización por los serotipos incluidos en su composición. Por este motivo las vacunas conjugadas proporcionan inmunidad de grupo. La vacunación de adolescentes frente a Neisseria menigintidis puede modificar el patrón de transmisión de la infección con una reducción de la incidencia en niños. En la actualidad se dispone de vacunas conjugadas frente a meningococo C, conjugadas tetravalantes frente a los serogrupos ACWY y de proteínas recombinantes frente a meningococo B. La inmunidad de grupo generada por vacunas conjugadas ha sido demostrada para Neisseria menigintidis C. Desafortunadamente existe escasa evidencia del impacto de las vacunas frente a meningococo B en la reducción del estado de portador entre adultos jóvenes. La infección natural por Bordetella pertussis estimula la producción de linfocitos T de memoria e induce una intensa respuesta de IgA secretora en la nasofaringe. En contraste con la infección natural y con las vacunas de células completas las actuales vacunas acelulares, no generan inmunidad en mucosas y no otorgan inmunidad de grupo. En un intento de resolver este problema se están desarrollando vacunas alternativas frente a Bordetella pertussis como las nuevas de células completas y las vivas atenuadas.

Genome characteristics of Bordetella pertussis isolates from Tunisia.

The recent increase in pertussis cases observed in some countries may have several causes, including the evolution of Bordetella pertussis populations towards escape of vaccine-induced immunity. Most genomic studies of B. pertussis isolates performed so far are from countries that use acellular vaccines. The objective was to analyse genomic sequences of isolates collected during the 2014 whooping cough epidemic in Tunisia, a country where whole-cell vaccines are used. Ten Tunisian isolates and four vaccine strains were sequenced and compared to 169 isolates from countries where acellular vaccines are used. Phylogenetic analysis showed that Tunisian isolates are diverse, demonstrating a multi-strain 2014 epidemic peak, and are intermixed with those circulating in other world regions, showing inter-country transmission. Consistently, Tunisian isolates have antigen variant composition observed in other world regions. No pertactin-deficient strain was observed. The Tunisian B. pertussis population appears to be largely connected with populations from other countries.

Phase 1 trial of a 20-valent pneumococcal conjugate vaccine in healthy adults

IntroductionStreptococcus pneumoniae is a leading cause of bacteremia, bacterial pneumonia, and meningitis, and is associated with substantial morbidity and mortality, particularly in those under 2 years of age and those over 65 years of age. While significant progress against S. pneumoniae-related disease has been made as a result of the introduction of pneumococcal conjugate vaccines (PCV7, PCV10 and PCV13), there remains value in further expanding pneumococcal vaccine serotype coverage. Here we present the first report of a 20-valent pneumococcal conjugate vaccine (PCV20) containing capsular polysaccharide conjugates present in PCV13 as well as 7 new serotypes (8, 10A, 11A, 12F, 15B, 22F, and 33F) which are important contributors to pneumococcal disease. MethodsThis Phase I first-in-human study was a randomized, controlled, observer-blinded study with a two-arm parallel design to assess the safety, tolerability, and immunogenicity of PCV20 in adults. A total of 66 healthy adults 18–49 years of age with no history of pneumococcal vaccination were enrolled and randomized to receive a single dose of PCV20 or a licensed tetanus, diphtheria, acellular pertussis combination vaccine (Tdap) control. Local injection site reactions, select systemic symptoms, laboratory studies, and adverse events were assessed. Opsonophagocytic activity (OPA) titers and IgG concentrations were measured in sera collected prior to, and approximately one month (28–35 days) after vaccination. ResultsVaccination with PCV20 elicited substantial IgG and functional bactericidal immune responses as demonstrated by increases in IgG geometric mean concentrations (GMCs) and OPA geometric mean titers (GMTs) to the 20 vaccine serotypes. The overall safety profile of PCV20 was similar to Tdap, and generally consistent with that observed after PCV13 administration. ConclusionsVaccination with PCV20 was well tolerated and induced substantial functional (OPA) and IgG responses to all vaccine serotypes. There were no safety issues identified in this Phase 1 study, and the data supported further evaluation of PCV20.

Effectiveness of Acellular Pertussis Vaccine in Older Adults: Nested Matched Case-control Study

Despite recommendations that older adults receive acellular pertussis vaccines, data on direct effectiveness in adults aged over 50 years are sparse. A case-control study nested within an adult cohort. Cases were identified from linked pertussis notifications and each matched to 3 controls on age, sex, and cohort recruitment date. Cases and controls were invited to complete a questionnaire, with verification of vaccination status by their primary care provider. Vaccine effectiveness (VE) was estimated by conditional logistic regression, with adjustment for reported contact with children and area of residence. Of 1112 notified cases in the cohort, we had complete data for 333 cases and 506 controls. Among 172 PCR-diagnosed cases (mean age, 61 years), 11.2% versus 19.5% of controls had provider-verified pertussis vaccination, on average, 3.2 years earlier. Adjusted VE against PCR-diagnosed pertussis was 52% (95% CI, 15-73%), nonsignificantly higher if vaccinated within 2 years (63%; -5-87%). Adjusted VE was similar in adults born before 1950, presumed primed by natural infection (51%; -8-77%) versus those born 1950 or later who may have received whole-cell pertussis vaccine (53%; -11-80%) (P-heterogeneity = 0.9). Among 156 cases identified by single-point serology, adjusted VE was -55% (-177-13%). We found modest protection against PCR-confirmed pertussis among older adults (mean age, 61 years; range, 46-81 years) within 5 years after acellular vaccine. The most likely explanation for the markedly divergent VE estimate from cases identified by single-titer serology is misclassification arising from limited diagnostic specificity in our setting.