Cécile A C M van Els

National Institute for Public Health and the Environment (RIVM), Utrecht, Utrecht, Netherlands

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Publications (38)144.16 Total impact

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    ABSTRACT: Bordetella pertussis circulates even in highly vaccinated countries affecting all age groups. Insight into the scale of concealed reinfections is important as they may contribute to transmission. We therefore investigated whether current single-point serodiagnostic methods are suitable to estimate the prevalence of pertussis reinfection. Two methods based on IgG-Ptx plasma levels alone were used to evaluate the proportion of renewed seroconversions in the past year in a cohort of retrospective pertussis cases ≥ 24 months after a proven earlier symptomatic infection. A Dutch population database was used as a baseline. Applying a classical 62.5 IU/ml IgG-Ptx cut-off, we calculated a seroprevalence of 15% in retrospective cases, higher than the 10% observed in the population baseline. However, this method could not discriminate between renewed seroconversion and waning of previously infection-enhanced IgG-Ptx levels. Two-component cluster analysis of the IgG-Ptx datasets of both pertussis cases and the general population revealed a continuum of intermediate IgG-Ptx levels, preventing the establishment of a positive population and the comparison of prevalence by this alternative method. Next, we investigated the complementary serodiagnostic value of IgA-Ptx levels. When modelling datasets including both convalescent and retrospective cases we obtained new cut-offs for both IgG-Ptx and IgA-Ptx that were optimized to evaluate renewed seroconversions in the ex-cases target population. Combining these cut-offs two-dimensionally, we calculated 8.0% reinfections in retrospective cases, being below the baseline seroprevalence. Our study for the first time revealed the shortcomings of using only IgG-Ptx data in conventional serodiagnostic methods to determine pertussis reinfections. Improved results can be obtained with two-dimensional serodiagnostic profiling. The proportion of reinfections thus established suggests a relatively increased period of protection to renewed infection after clinical pertussis.
    Full-text · Article · Feb 2016 · PLoS ONE

  • No preview · Article · Feb 2016
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    ABSTRACT: Comprehensive analysis of the complex nature of the Human Leukocyte Antigen (HLA) class II ligandome is of utmost importance to understand the basis for CD4+ T cell mediated immunity and tolerance. Here, we implemented important improvements in the analysis of the repertoire of HLA-DR-presented peptides, using hybrid mass spectrometry-based peptide fragmentation techniques on a ligandome sample isolated from matured human monocyte-derived dendritic cells (DC). The reported data set constitutes nearly 14 thousand unique high-confident peptides, i.e. the largest single inventory of human DC derived HLA-DR ligands to date. From a technical viewpoint the most prominent finding is that no single peptide fragmentation technique could elucidate the majority of HLA-DR ligands, due to the wide range of physical chemical properties displayed by the HLA-DR ligandome. Our in-depth profiling allowed us to reveal a strikingly poor correlation between the source proteins identified in the HLA class II ligandome and the DC cellular proteome. Important selective sieving from the sampled proteome to the ligandome, was evidenced by specificity in the sequences of the core regions both at their N- and C- termini, hence not only reflecting binding motifs but also dominant protease activity associated to the endolysosomal compartments. Moreover, we demonstrate that the HLA-DR ligandome reflects a surface representation of cell-compartments specific for biological events linked to the maturation of monocytes into antigen presenting cells. Our results present new perspectives into the complex nature of the HLA class II system and will aid future immunological studies in characterizing the full breadth of potential CD4+ T cell epitopes relevant in health and disease.
    Full-text · Article · Jan 2016 · Molecular & Cellular Proteomics
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    ABSTRACT: Immunity to infections with measles virus (MV) can involve vigorous human leukocyte antigen (HLA) class I-restricted CD8+ cytotoxic T cell (CTL) responses. MV, albeit regarded monotypic, is known to undergo molecular evolution across its RNA genome. To address which regions of the MV proteome are eligible for recognition by CD8+ CTLs and how different HLA class I loci contribute to the epitope display, we interrogated the naturally processed and presented MV peptidome extracted from cell lines expressing in total a broad panel of 16 different common HLA-A, -B, and -C molecules. The repertoire and abundance of MV peptides were bona fide identified by nanoHPLC–MS/MS. ­Eighty-nine MV peptides were discovered and assignment to an HLA-A, -B, or -C allele, based on HLA-peptide affinity prediction, was in most cases successful. Length variation and presentation by multiple HLA class I molecules was common in the MV peptidome. More than twice as many unique MV epitopes were found to be restricted by HLA-B than by HLA-A, while MV peptides with supra-abundant expression rates (>5,000 cc) were rather associated with HLA-A and HLA-C. In total, 59 regions across the whole MV proteome were identified as targeted by HLA class I. Sequence coverage by epitopes was highest for internal proteins transcribed from the MV-P/V/C and -M genes and for hemagglutinin. At the genome level, the majority of the HLA class I-selected MV epitopes represented codons having a higher non-synonymous mutation rate than silent mutation rate, as established by comparison of a set of 58 unique full length MV genomes. Interestingly, more molecular variation was seen for the epitopes expressed at rates ≥1,000 cc. These data for the first time indicate that HLA class I broadly samples the MV proteome and that CTL pressure may contribute to the genomic evolution of MV.
    Preview · Article · Nov 2015 · Frontiers in Immunology

  • No preview · Conference Paper · Nov 2015
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    ABSTRACT: The cytotoxic T cell (CTL) response is determined by the peptide repertoire presented by the HLA class I molecules of an individual. We performed an in-depth analysis of the peptide repertoire presented by a broad panel of common HLA class I molecules on four B lymphoblastoid cell-lines (BLCL). Peptide elution and mass spectrometry analysis were utilised to investigate the number and abundance of self-peptides. Altogether, 7897 unique self-peptides, derived of 4344 proteins, were eluted. After viral infection, the number of unique self-peptides eluted significantly decreased compared to uninfected cells, paralleled by a decrease in the number of source proteins. In the overall dataset, the total number of unique self-peptides eluted from HLA-B molecules was larger than from HLA-A molecules, and they were derived from a larger number of source proteins. These results in B cells suggest that HLA-B molecules possibly present a more diverse repertoire compared to their HLA-A counterparts, which may contribute to their immunodominance. This study provides a unique data set giving new insights into the complex system of antigen presentation for a broad panel of HLA molecules, many of which were never studied this extensively before.
    Preview · Article · Sep 2015 · PLoS ONE
  • Inonge van Twillert · Wanda G H Han · Cécile A.C.M. van Els
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    ABSTRACT: While it is clear that the maintenance of B. pertussis-specific immunity evoked both after vaccination and infection is insufficient, it is unknown at which pace waning occurs and which threshold levels of sustained functional memory B and T cells are required to provide long term protection. Longevity of human cellular immunity to B. pertussis has been studied less extensively than serology, but is suggested to be key for the observed differences between the duration of protection induced by acellular vaccination versus whole cell vaccination or infection. The induction and maintenance of levels of protective memory B and T cells may alter with age, associated with changes of the immune system throughout life and with accumulating exposures to circulating B. pertussis or vaccine doses. This is relevant since pertussis affects all age groups. This review summarizes current knowledge on the waning patterns of human cellular immune responses to B. pertussis as addressed in diverse vaccination and infection settings and in various age groups. Knowledge on the effectiveness and flaws in human B. pertussis-specific cellular immunity ultimately will advance the improvement of pertussis vaccination strategies.
    No preview · Article · Sep 2015 · Pathogens and Disease
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    ABSTRACT: Current acellular pertussis vaccines have various shortcomings, which may contribute to their sub-optimal efficacy and waning immunity in vaccinated populations. This calls for the development of new pertussis vaccines capable of inducing long-lived protective immunity. Immunization with whole cell pertussis vaccines and natural infection with Bordetella pertussis induce distinct and more protective immune responses when compared with immunization with acellular pertussis vaccines. Therefore, the immune responses induced with whole cell vaccine or after infection can be used as a benchmark for the development of third generation vaccines against pertussis. Here, we review the literature on the immunology of B. pertussis infection and vaccination and discuss the lessons learned that will help in the design of improved pertussis vaccines.
    Full-text · Article · Sep 2015 · Pathogens and Disease
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    Full-text · Dataset · Aug 2015
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    ABSTRACT: We report unexpected mass spectrometric observations of glycosylated human leukocyte antigen (HLA) class Ibound peptides. Complemented by molecular modeling, in vitro enzymatic assays, and oxonium ion patterns, we propose that the observed O-linked glycans carrying up to five monosaccharides are extended O-GlcNAc’s rather than GalNAc-initiated Oglycans. A cytosolic O-GlcNAc modification is normally terminal and does not extend to produce a polysaccharide, but O-GlcNAc on an HLA peptide presents a special case because the loaded HLA class I complex traffics through the endoplasmic reticulum and Golgi apparatus on its way to the cell membrane, and is hence exposed to glycosyltransferases. In addition we report for the first time natural HLA class I presentation of O- and N-linked glycopeptides derived from membrane proteins. HLA class I peptides with centrally located oligosaccharides have been shown to be immunogenic and may therefore be important targets for immunesurveillance.
    Full-text · Article · Aug 2015 · Journal of the American Chemical Society
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    ABSTRACT: Background. Both the 10- and 13-valent pneumococcal conjugate vaccines (PCV10 and PCV13) induce immunological memory against Streptococcus pneumoniae infections caused by vaccine serotypes. In addition to comparing serum antibody levels, we investigated frequencies of serotype-specific plasma cells (PCs) and memory B-cells (Bmems) as potential predictors of long-term immunity around the booster vaccination at 11 months of age. Methods. Infants were immunized with PCV10 or PCV13 at 2, 3, 4, and 11 months of age. Blood was collected before the 11-month booster or 7–9 days afterward. Serotype-specific immunoglobulin G (IgG) levels were determined in serum samples by multiplex immunoassay. Circulating specific PCs and Bmems against shared serotypes 1, 6B, 7F, and 19F and against PCV13 serotypes 6A and 19A were measured in peripheral blood mononuclear cells by enzyme-linked immunospot assay. Results. No major differences in IgG levels and PC frequencies between groups were found for the 4 shared serotypes. Notably, PCV13 vaccination resulted in higher frequencies of Bmems than PCV10 vaccination, both before and after the booster dose, for all 4 shared serotypes except for serotype 1 postbooster. For PCV13-specific serotypes 6A and 19A, the IgG levels and frequencies of PCs and Bmems were higher in the PCV13 group, pre- and postbooster, except for PC frequencies prebooster. Conclusions. Both PCVs are immunogenic and induce measurable IgG, PC, and Bmem booster responses at 11 months. Compared to PCV10, vaccination with PCV13 was associated with overall similar IgG levels and PC frequencies but with higher Bmem frequencies before and after the 11-month booster. The clinical implications of these results need further follow-up. Clinical Trials Registration. NTR3069.
    Full-text · Article · Jul 2015 · Clinical Infectious Diseases
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    ABSTRACT: Whooping cough remains a problem despite vaccination and worldwide resurging of pertussis is evident. Since cellular immunity plays a role in long-term protection against pertussis, we studied pertussis-specific T-cell responses. We compared T-cell memory responses in children, who have been primed during infancy with either a whole-cell-pertussis (wP) or an acellular-pertussis (aP) vaccine around the preschool aP booster dose at 4 years of age. PBMCs were isolated and stimulated with pertussis-vaccine antigens for 5 days. T-cells were characterized by flow-based analysis of CFSE dilution, and CD4, CD3, CD45RA, CCR7, IFN-γ and TNF-α expression. Before the aP preschool booster vaccination, both the proliferated PT-specific CD4(+) and CD8(+) T-cell fraction (CFSE(dim)) was higher in aP- compared to wP-primed children. Post-booster, more pertussis-specific CD4(+) effector memory cells (CD45RA(-)CCR7(-)) were induced in aP-primed children compared to those primed with wP. The booster vaccination did not appear to significantly affect the T-cell memory subsets and functionality neither in aP-primed nor in wP-primed children. Although the percentages of Th1 cytokine producing cells were alike in aP- and wP-primed children pre-booster, aP-primed children produced more Th1 cytokines due to higher numbers of proliferated pertussis-specific effector memory cells. At present infant vaccinations with four aP vaccines in the first year of life result in pertussis-specific CD4(+) and CD8(+) effector memory T-cell responses that persist in children until 4 years of age and are higher than in wP-primed children. The booster at 4 years of age is therefore questionable; this may be postponed to 6 years of age. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    No preview · Article · Mar 2015 · Clinical and vaccine Immunology: CVI
  • Wanda G.H. Han · Kina Helm · Martien M.C. Poelen · Henny G. Otten · Cécile A.C.M. van Els
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    ABSTRACT: Pertussis is occuring in highly vaccinated populations, suggesting insufficient protective memory CD4(+) T cells to Bordetella (B.) pertussis. P.69 Pertactin (P.69 Prn) is an important virulence factor of B. pertussis, and P.69 Prn7-24 is an immunodominant CD4(+) T cell epitope in mice and broadly recognized in humans. P.69 Prn7-24 peptide-MHC II tetramers (DRB4*0101/IVKT) were designed to ex vivo interrogate the presence and differentiation state of P.69 Prn7-24 specific CD4(+) T cells in six symptomatic pertussis cases. Cases with relatively more CD45RA(-)CCR7(+) central memory CD4(+)DRB4*0101/IVKT(+) T cells secreted Th1 cytokines, while cases with more CD45RA(-)CCR7(-) effector memory CD4(+)DRB4*0101/IVKT(+) T cells secreted both Th1 and Th2 cytokines upon peptide stimulation. CD45RA(+)CCR7(-) terminal differentiation pattern was associated with low or non-functionality based on cytokine secretion. This study provides proof of principle for further peptide-MHC II tetramer guided approaches in the elucidation of limited immunological memory to B. pertussis and the resurgence of pertussis. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Feb 2015 · Clinical Immunology
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    ABSTRACT: Whole cell pertussis (wP) vaccines are gradually being replaced by aluminum salt-adjuvanted acellular pertussis (aP) vaccines. These promote CD4(+) T cell responses with a non-protective Th2 component, while protective immune mechanisms to B. pertussis may rather involve long-lived Th1/Th17 type CD4(+) T cells. Here we asked whether addition of a non-toxic meningococcal LPS derivative, LpxL1, as adjuvant can favorably modulate the aP-induced pertussis-specific CD4(+) T cell response in mice. To assess the effect of TLR4 ligation, Th type, quantity, and memory potential of pertussis-specific CD4(+) T cells were determined at the single-cell level after aP and aP+LpxL1 vaccination using intracellular cytokine staining and MHC class II tetramers. Adding LpxL1 to the aP vaccine weakened the Th2 component and strengthened the Th1/Th17 component of the specific CD4(+) T cell response. Notably, LpxL1 addition also induced higher frequencies of tetramer positive CD4(+) T cells in draining lymph nodes or blood, depending on the phase after vaccination. Moreover, there was a net profit in the number of CD4(+) T cells with a central memory phenotype, preferred for long-term immunity. Thus, adding a TLR4 ligand as adjuvant to a current aP vaccine was associated with a more favorable pertussis-specific CD4(+) T cell response. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Feb 2015 · Vaccine
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    ABSTRACT: Bordetella pertussis is a Gram-negative bacterium and the causative agent of whooping cough. Despite high vaccination coverage, outbreaks are being increasingly reported worldwide. Possible explanations include adaptation of this pathogen, which may interfere with recognition by the innate immune system. Here, we describe innate immune recognition and responses to different B. pertussis clinical isolates. By using HEK-Blue cells transfected with different pattern recognition receptors, we found that 3 out of 19 clinical isolates fail to activate TLR4. These findings were confirmed using the monocytic MM6 cell line. Although incubation with high concentrations of these 3 strains resulted in significant activation of the MM6 cells, it was found to occur mainly through interaction with TLR2 and not through TLR4. When using live bacteria, these 3 strains also failed to activate TLR4 on HEK-Blue cells and activation of MM6 cells or human monocyte-derived dendritic cells was significantly less compared to activation with the other 16 strains. Mass spectrum analysis of the lipid A from these 3 strains indicated an altered structure of this molecule. Gene sequence analysis revealed mutations in genes involved in lipid A synthesis. Findings from this study indicate that B. pertussis isolates, that do not activate TLR4, occur naturally and that this phenotype may give this bacterium an advantage in tempering the innate immune response and establishing infection. Knowledge on the strategies used by this pathogen on evading the host immune response is essential for the improvement of current vaccines or for the development of new ones.
    Full-text · Article · Oct 2014 · Infection and Immunity
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    ABSTRACT: Background. Since 2009, various mumps outbreaks have occurred in the Netherlands, affecting mostly young adults vaccinated against mumps. In this retrospective study, we estimated attack rates for symptomatic and asymptomatic mumps virus infection based on mumps-specific immunoglobulin (Ig)G concentrations in paired blood samples obtained before and after the mumps outbreaks, collected in 2 university cities. We aimed to identify a serological correlate of immune protection and risk factors for mumps virus infection. Methods. Mumps-specific IgG levels were measured by Luminex technology in paired pre- and post-outbreak samples from students from Leiden (n = 135) and Utrecht (n = 619). Persons with a 4-fold increase in mumps IgG concentrations or mumps IgG concentrations >1500 RU/mL were assumed to have had a mumps virus infection. Results. Attack rates for symptomatic and asymptomatic mumps virus infection were 2.0% and 3.8%, respectively. Pre-outbreak mumps-specific IgG concentrations were lower among cases than among noncases (P = .005) despite vaccination history, but no serological cutoff for immune protection could be established. Mumps among housemates was significantly associated with serological evidence for mumps virus infection (odds ratio, 7.25 [95% confidence interval, 3.20–16.40]; P < .001). Conclusions. Symptomatic and asymptomatic mumps virus infections in vaccinated persons can be identified by retrospective assessment of mumps-specific IgG antibodies in blood samples. Keywords. asymptomatic infection; attack rates; correlate of protection; IgG antibodies; MMR vaccination; mumps virus; risk factors; serology.
    Full-text · Article · Oct 2014 · Open Forum Infectious Diseases
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    ABSTRACT: Worldwide resurgence of pertussis necessitates the need for improvement of pertussis vaccines and vaccination strategies. Since natural infections induce a longer-lasting immunity than vaccinations, detailed knowledge of the immune responses following natural infection can provide important clues for such improvement. The purpose was to elucidate the kinetics of the protective immune response evolving after experimental Bordetella pertussis (B. pertussis) infection in mice. Data were collected from (i) individual analyses, i.e. microarray, flow cytometry, multiplex immunoassays, and bacterial clearance; (ii) twelve time points during the infection; and (iii) different tissues involved in the immune responses, i.e. lungs, spleen and blood. Combined data revealed detailed insight in molecular and cellular sequence of events connecting different phases (innate, bridging and adaptive) of the immune response following the infection. We detected a prolonged acute phase response, broad pathogen recognition, and early gene signatures of subsequent T-cell recruitment in the lungs. Activation of particular transcription factors and specific cell markers provided insight into the time course of the transition from innate towards adaptive immune responses, which resulted in a broad spectrum of systemic antibody subclasses and splenic Th1/Th17 memory cells against B. pertussis. In addition, signatures preceding the local generation of Th1 and Th17 cells as well as IgA in the lungs, considered key elements in protection against B. pertussis, were established. In conclusion, molecular and cellular immunological processes in response to live B. pertussis infection were unraveled, which may provide guidance in selecting new vaccine candidates that should evoke local and prolonged protective immune responses.
    Full-text · Article · Aug 2014 · PLoS ONE
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    ABSTRACT: CD4(+) T cells are prominent effector cells in controlling Mycobacterium tuberculosis (Mtb) infection but may also contribute to immunopathology. Studies probing the CD4(+) T cell response from individuals latently infected with Mtb or patients with active tuberculosis using either small or proteome-wide antigen screens so far revealed a multi-antigenic, yet mostly invariable repertoire of immunogenic Mtb proteins. Recent developments in mass spectrometry-based proteomics have highlighted the occurrence of numerous types of post-translational modifications (PTMs) in proteomes of prokaryotes, including Mtb. The well-known PTMs in Mtb are glycosylation, lipidation, or phosphorylation, known regulators of protein function or compartmentalization. Other PTMs include methylation, acetylation, and pupylation, involved in protein stability. While all PTMs add variability to the Mtb proteome, relatively little is understood about their role in the anti-Mtb immune responses. Here, we review Mtb protein PTMs and methods to assess their role in protective immunity against Mtb.
    Full-text · Article · Aug 2014 · Frontiers in Immunology
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    ABSTRACT: The identification of peptides presented by human leukocyte antigen (HLA) class I is tremendously important for the understanding of antigen presentation mechanisms under healthy or diseased conditions. Currently, mass spectrometry-based methods represent the best methodology for the identification of HLA class I-associated peptides. However, the HLA class I peptide repertoire remains largely unexplored because the variable nature of endogenous peptides represents difficulties in conventional peptide fragmentation technology. Here, we substantially enhanced (about threefold) the identification success rate of peptides presented by HLA class I using combined electron-transfer/higher-energy collision dissociation (EThcD), reporting over 12,000 high-confident (false discovery rate <1%) peptides from a single human B-cell line. The direct importance of such an unprecedented large dataset is highlighted by the discovery of unique features in antigen presentation. The observation that a substantial part of proteins is sampled across different HLA alleles, and the common occurrence of HLA class I nested sets, suggest that the constraints of HLA class I to comprehensively present the health states of cells are not as tight as previously thought. Our dataset contains a substantial set of peptides bearing a variety of posttranslational modifications presented with marked allele-specific differences. We propose that EThcD should become the method of choice in analyzing HLA class I-presented peptides.
    No preview · Article · Mar 2014 · Proceedings of the National Academy of Sciences
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    ABSTRACT: Knowledge of naturally processed Bordetella pertussis (B. pertussis) specific T cell epitopes may help to better understand the basis of cell-mediated immune mechanisms to control this re-emerging pathogen. Here we for the first time elucidate dominant MHC class II-presented B. pertussis CD4(+) T cell epitopes, expressed on human monocyte-derived dendritic cells (MDDC) after processing of whole bacterial cells, using a platform immunoproteomics technology. Pertussis epitopes identified in the context of HLA-DR molecules were derived from two envelope proteins, i.e. putative periplasmic protein (PPP) and putative peptidoglycan-associated lipoprotein (PAL), and from two cytosolic proteins, i.e. 10 kDa chaporonin groES protein (groES) and adenylosuccinate synthetase (ASS). No epitopes were detectable from known virulence factors. CD4(+) T cell responsiveness in healthy adults against peptide pools representing epitope regions or full proteins confirmed immunogenicity of PAL, PPP, groES and ASS. Elevated lymphoproliferative activity to PPP, groES and ASS in subjects within a year after diagnosis of symptomatic pertussis suggested immunogenic exposure to these proteins during clinical infection. The PAL, PPP, groES and ASS specific responses were associated with secretion of functional Th1 (TNF-α and IFN-γ) and Th2 (IL-5 and Il-13) cytokines. Relative paucity in the natural B. pertussis epitope display of MDDC, not dominated by epitopes from known protective antigens, could interfere with effectiveness of immune recognition of B. pertussis. A more complete understanding of hallmarks in B. pertussis specific immunity may advance the design of novel immunological assays and prevention strategies.
    No preview · Article · Mar 2014 · Clinical and vaccine Immunology: CVI

Publication Stats

353 Citations
144.16 Total Impact Points

Institutions

  • 2003-2015
    • National Institute for Public Health and the Environment (RIVM)
      • • Centre for Infectious Disease Control (CIb)
      • • Vaccinology Unit
      Utrecht, Utrecht, Netherlands
  • 2014
    • Yale University
      New Haven, Connecticut, United States
  • 2004-2010
    • Netherlands Vaccine Institute (NVI)
      Utrecht, Utrecht, Netherlands