Nasopharyngeal sampling is used for detecting bacteria commonly involved in upper respiratory tract infections, but it requires training and may not always be well tolerated. We sampled children (n = 66) of ages 0 to 4 years, with rhinorrhea, by using a nasopharyngeal swab, a nasal swab, and nose blowing/wiping into a paper tissue. Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus were cultured at similar rates across methods with high concordance (80 to 97%), indicating that they are reliably detected by alternative means.
Immunization with acellular pertussis vaccine (aP) induces higher specific antibody levels and fewer adverse reactions than does immunization with the whole-cell vaccine (wP). However, antibody levels in infants induced by both types of pertussis vaccines wane already after 1 year. Therefore, long-term T-cell responses upon vaccination might play a role in protection against pertussis. In a cross-sectional study (ISRCTN65428640), we investigated T-helper (Th) cell immune responses in wP- or aP-vaccinated children before and after an aP low-dose or high-dose preschool booster at 4 years of age in The Netherlands. T cells were stimulated with pertussis vaccine antigens. The numbers of gamma interferon-producing cells and Th1, Th2, Th17, and interleukin-10 (IL-10) cytokine concentrations were determined. In addition, pertussis-specific IgE levels were measured in plasma. Children being vaccinated with aP vaccinations at 2, 3, 4, and 11 months of age still showed higher pertussis-specific T-cell responses at 4 years of age than did wP-vaccinated children. These T-cell responses failed to show a typical increase in cytokine production after a fifth aP vaccination but remained high after a low-dose booster and seemed to decline even after a high-dose booster. Importantly, elevated IgE levels were induced after this booster vaccination. In contrast, wP-vaccinated children had only low prebooster T-cell responses, and these children showed a clear postbooster T-cell memory response even after a low-dose booster vaccine. Four high-dose aP vaccinations in infancy induce high T-cell responses still present even 3 years after vaccination and enhanced IgE responses after preschool booster vaccination. Therefore, studies of changes in vaccine dosage, timing of pertussis (booster) vaccinations, and the possible association with local side effects are necessary.
Knowledge of the immunological correlates of Staphylococcus aureus and Streptococcus pneumoniae colonization is required for the search for future protein vaccines. We evaluated natural antibody levels against pneumococcal and staphylococcal proteins in relation to previous bacterial colonization with both pathogens. In a randomized controlled trial, nasopharyngeal samples were obtained from children at 1.5, 6, 12, 18, and 24 months and cultured for S. aureus and S. pneumoniae. Approximately 50% of the children were PCV7 vaccinated. Serum IgG against 18 pneumococcal and 40 staphylococcal proteins was semiquantified by Luminex technology from 111 12 month olds and 158 24 month olds. Previous culture-proven S. aureus colonization was associated with higher IgG levels against 6/40 staphylococcal proteins (ClfB, ClfA, Efb, CHIPS, LukD, and LukF [P ≤ 0.001]) compared to noncarriers. Previous pneumococcal colonization was associated with increased IgG levels against 12/18 pneumococcal proteins compared to noncarriers (P ≤ 0.003). Increasing age was associated with higher levels of antibodies to most pneumococcal proteins and lower levels of antibodies to over half the staphylococcal proteins, reflecting natural colonization dynamics. Anti-S. pneumoniae and anti-S. aureus protein antibodies at the age of 12 months were not negatively correlated with subsequent colonization with the homologous species in the following year and did not differ between PCV7-vaccinated and nonvaccinated children. Colonization with S. aureus and S. pneumoniae induces serum IgG against many proteins, predominantly proteins with immune-modulating functions, irrespective of PCV7 vaccination. None of them appeared to be protective against new acquisition with both pathogens, possibly due to the polymorphic nature of those proteins in the circulating bacterial population.
To understand the role of human microbiota in health and disease, we need to study effects of environmental and other epidemiological variables on the composition of microbial communities. The composition of a microbial community may depend on multiple factors simultaneously. Therefore we need multivariate methods for detecting, analyzing and visualizing the interactions between environmental variables and microbial communities. We provide two different approaches for multivariate analysis of these complex combined datasets: (i) We select variables that correlate with overall microbiota composition and microbiota members that correlate with the metadata using canonical correlation analysis, determine independency of the observed correlations in a multivariate regression analysis, and visualize the effect size and direction of the observed correlations using heatmaps; (ii) We select variables and microbiota members using univariate or bivariate regression analysis, followed by multivariate regression analysis, and visualize the effect size and direction of the observed correlations using heatmaps. We illustrate the results of both approaches using a dataset containing respiratory microbiota composition and accompanying metadata. The two different approaches provide slightly different results; with approach (i) using canonical correlation analysis to select determinants and microbiota members detecting fewer and stronger correlations only and approach (ii) using univariate or bivariate analyses to select determinants and microbiota members detecting a similar but broader pattern of correlations. The proposed approaches both detect and visualize independent correlations between multiple environmental variables and members of the microbial community. Depending on the size of the datasets and the hypothesis tested one can select the method of preference.
The CRM197-conjugated 7-valent pneumococcal vaccine (PCV7) is protective against vaccine serotype disease and nasopharyngeal carriage. Data on PCV7-induced mucosal antibodies in relation to systemic or natural anticapsular antibodies are scarce.
In a randomized controlled setting, children received PCV7 at age 2 and 4 months (2-dose group), at age 2, 4 and 11 months (2+1-dose group) or no PCV7 (control group). From 188 children paired saliva samples were collected at 12 and 24 months of age. From a subgroup of 15 immunized children also serum samples were collected. IgG and IgA antibody-levels were measured by multiplex immunoassay.
At 12 months, both vaccine groups showed higher serum and saliva IgG-levels against vaccine serotypes compared with controls which sustained until 24 months for most serotypes. Salivary IgG-levels were 10–20-fold lower compared to serum IgG, however, serum and saliva IgG-levels were highly correlated. Serum and salivary IgA-levels were higher in both vaccine groups at 12 months compared with controls, except for serotype 19F. Higher salivary IgA levels remained present for most serotypes in the 2+1-dose group until 24 months, but not in the 2-dose group. Salivary IgA more than IgG, increased after documented carriage of serotypes 6B, 19F and 23F In contrast to IgG, salivary IgA-levels were comparable with serum, suggesting local IgA-production.
PCV7 vaccination results in significant increases in salivary IgG and IgA-levels, which are more pronounced for IgG when compared to controls. In contrast, salivary anticapsular IgA-levels seemed to respond more to natural boosting. Salivary IgG and IgA-levels correlate well with systemic antibodies, suggesting saliva might be useful as potential future surveillance tool.
Accurate analyses of microbiota composition of low-density communities (103–104 bacteria/sample) can be challenging. Background DNA from chemicals and consumables, extraction biases as well as differences in PCR efficiency can significantly interfere with microbiota assessment. This study was aiming to establish protocols for accurate microbiota analysis at low microbial density.
To examine possible effects of bacterial density on microbiota analyses we compared microbiota profiles of serial diluted saliva and low (nares, nasopharynx) and high-density (oropharynx) upper airway communities in four healthy individuals. DNA was extracted with four different extraction methods (Epicentre Masterpure, Qiagen DNeasy, Mobio Powersoil and a phenol bead-beating protocol combined with Agowa-Mag-mini). Bacterial DNA recovery was analysed by 16S qPCR and microbiota profiles through GS-FLX-Titanium-Sequencing of 16S rRNA gene amplicons spanning the V5–V7 regions.
Lower template concentrations significantly impacted microbiota profiling results. With higher dilutions, low abundant species were overrepresented. In samples of <105 bacteria per ml, e.g. DNA <1 pg/µl, microbiota profiling deviated from the original sample and other dilutions showing a significant increase in the taxa Proteobacteria and decrease in Bacteroidetes. In similar low density samples, DNA extraction method determined if DNA levels were below or above 1 pg/µl and, together with lysis preferences per method, had profound impact on microbiota analyses in both relative abundance as well as representation of species.
This study aimed to interpret microbiota analyses of low-density communities. Bacterial density seemed to interfere with microbiota analyses at < than 106 bacteria per ml or DNA <1 pg/µl. We therefore recommend this threshold for working with low density materials. This study underlines that bias reduction is crucial for adequate profiling of especially low-density bacterial communities.
CD27 is a lymphocyte co-stimulatory molecule that regulates T, NK B, and plasma cell function, survival and differentiation. Based on its function and expression pattern we considered CD27 as a candidate gene in patients with hypogammaglobulinemia.
Description of the clinical and immunological phenotype of patients having genetic CD27 deficiency.
A molecular and extended immunological analysis was performed on two patients lacking CD27 expression.
We identified two brothers with a homozygous mutation in CD27 leading to absence of CD27 expression. Both patients suffered from persistent symptomatic EBV viremia. The index patient was hypogammaglobulinemic and immunoglobulin replacement therapy was initiated. His brother developed aplastic anemia in the course of his EBV infection and died from fulminant Gram positive bacterial sepsis. Immunologically, lack of CD27 expression was associated with impaired T-cell dependent B-cell responses and T-cell dysfunction.
Our findings identify a role for CD27 in humans and suggest that this deficiency can explain particular cases of persistent symptomatic EBV viremia with hypogammaglobulinemia and impaired T cell dependent antibody generation.
EBV; viremia; hypogammaglobulinemia; CD27; immunodeficiency; T cell; B cell; NK cell; phenotype
Disease incidence and case fatality rates declined 4 years after introduction of the vaccine.
invasive pneumococcal disease; Streptococcus pneumoniae; epidemiology; 7-valent pneumococcal conjugate vaccine; PCV7; age-specific rates; surveillance; herd immunity; the Netherlands; bacteria; vaccines
In this study the reliability and validity of generic and disease-specific questionnaires has been assessed focusing on responsiveness. This is part of a study on the effects of recurrent acute otitis media (rAOM) on functional health status (FHS) and health-related quality of life (HRQoL) in 383 children with rAOM participating in a randomized clinical trial. The following generic questionnaires were studied: 1. RAND general health rating index, 2. Functional Status Questionnaire (FSQ Generic and FSQ Specific), 3. TNO-AZL Infant Quality of Life (TAIQOL), and the following disease-specific questionnaires: 1. Otitis Media-6 (OM-6), 2. Numerical rating scales (NRS) for child and caregiver (NRS Child and NRS Caregiver), and 3. a new Family Functioning Questionnaire (FFQ). Reliability was good to excellent (Cronbach’s α range 0.80–0.90, intraclass correlation coefficient range 0.76–0.93). Moderate to strong correlations were found between the questionnaires as well as between questionnaires and relevant clinical indicators (r = 0.29–0.49), demonstrating construct validity. Discriminant validity for children with few versus frequent episodes of acute otitis media per year was good for most questionnaires (P < 0.004) but poor for the otitis media-related subscales of the TAIQOL (P = 0.10–0.97) and both NRS (P = 0.22 and 0.48). Except for the TAIQOL subscales, change scores were significant (P < 0.003) for generic and disease-specific questionnaires. Effect sizes were somewhat higher for disease-specific compared to generic questionnaires (0.55–0.95 versus 0.32–0.60) except for the TAIQOL subscales, which showed very poor sensitivity to change. Anchor-based methods resulted in a somewhat larger range of estimates of MCID than distribution-based methods. Combining distribution-based and anchor-based methods resulted in similar ranges for the minimally clinical important differences for generic and disease-specific questionnaires: 2–15 points on a 0–100 scale. Apart from the generic TAIQOL subscales, both generic and disease-specific questionnaires used in this study showed good psychometric qualities and responsiveness for use in clinical studies on children with rAOM.
Childhood infection; Acute otitis media; Functional health status; Quality of life; Reliability; Validity; Responsiveness
The 92 capsular serotypes of Streptococcus pneumoniae differ greatly in nasopharyngeal carriage prevalence, invasiveness and disease incidence. There has been some debate, though, as to whether serotype independently affects the outcome of invasive pneumococcal disease (IPD). Published studies have shown variable results with regards to case-fatality ratios for specific serotypes and the role of host factors in affecting these relationships. We evaluated whether risk of death from IPD is a stable serotype-associated property across studies, and then compared the pooled effect estimates with epidemiologic and biological correlates.
We performed a systematic review and meta-analysis of serotype-specific disease outcome for pneumonia and meningitis cases. Study-specific estimates of risk of death (risk ratio, RR) were pooled from 9 studies that provided serotype-specific data on pneumonia and meningitis using a random-effects method with serotype 14 as the reference. Pooled RRs were compared to RRs from adult cases with low co-morbidity scores to evaluate potential confounding by host factors.
There were significant differences in the RR estimates between serotypes among bacteremic pneumonia cases. Overall, types 1, 7F and 8 were associated with decreased RRs and types 3, 6A, 6B, 9N and 19F were associated with increased RRs. Outcomes among meningitis cases did not differ significantly between types. Serotypes with increased RRs tended to have a high carriage prevalence, low invasiveness, and were more heavily encapsulated in vitro. These results suggest that IPD outcome, like other epidemiologic measures, is a stable serotype-associated property.
Serotype; pneumococcus; case-fatality ratio; mortality; capsule; meta-analysis
To evaluate the effectiveness of the 7-valent pneumococcal conjugate vaccine (PCV7) program, we conducted a cross-sectional observational study on nasopharyngeal carriage of Streptococcus pneumoniae 3 years after implementation of the program in the Netherlands. We compared pneumococcal serotypes in 329 prebooster 11-month-old children, 330 fully vaccinated 24-month-old children, and 324 parents with age-matched pre-PCV7 (unvaccinated) controls (ages 12 and 24 months, n = 319 and n = 321, respectively) and 296 of their parents. PCV7 serotype prevalences before and after PCV7 implementation, respectively, were 38% and 8% among 11-month-old children, 36% and 4% among 24-month-old children, and 8% and 1% among parents. Non-PCV7 serotype prevalences were 29% and 39% among 11-month-old children, 30% and 45% among 24-month-old children, and 8% and 15% among parents, respectively; serotypes 11A and 19A were most frequently isolated. PCV7 serotypes were largely replaced by non-PCV7 serotypes. Disappearance of PCV7 serotypes in parents suggests strong transmission reduction through vaccination.
Streptococcus pneumoniae; nasopharyngeal colonization; heptavalent pneumococcal conjugate vaccine; infectious disease transmission; herd immunity; parents; infants; bacteria; research
Vaccine-serotype disease decreased, but non–vaccine-serotype disease increased.
In the Netherlands, the 7-valent pneumococcal conjugate vaccine (PCV-7) was implemented in a 3+1-dose schedule in the national immunization program for infants born after April 1, 2006. To assess the vaccine’s effectiveness, we compared disease incidence before and after vaccine implementation (June 2004–June 2006 and June 2006–June 2008, respectively). We serotyped 2,552 invasive pneumococcal isolates from throughout the Netherlands, covering 25% of the country’s population. Clinical characteristics were extracted from hospital records. After June 2006, vaccine-serotype invasive pneumococcal disease (IPD) decreased 90% (95% confidence interval [CI] 68%–97%) in children age eligible for PCV-7; simultaneously, however, non–vaccine-serotype IPD increased by 71% (not significant), resulting in a 44% total net IPD reduction (95% CI 7%–66%). IPD rates did not change for other age groups. In the Netherlands, PCV-7 offered high protection against vaccine-serotype IPD in vaccinated children, but increases of non–vaccine-serotype IPD reduced net vaccine benefits.
Heptavalent pneumococcal conjugate vaccine; pneumococcal vaccines; pneumococcal infections; surveillance; bacteria; research
The human nasopharynx is the main reservoir for Streptococcus pneumoniae. We applied conventional and molecular methods to determine the prevalence of S. pneumoniae nasopharyngeal colonization in adults. Paired trans-orally and trans-nasally obtained nasopharyngeal samples from 268 parents of 24-month-old children were assessed for pneumococcal presence. Parents were classified as colonized when live pneumococci were recovered from either sample cultured on medium selective for S. pneumoniae. Of the 52 (19%) colonized parents 49 (18%) were culture-positive in trans-nasal and 10 (4%) in trans-oral samples. Bacterial growth was harvested from these cultures, DNA isolated and tested by quantitative-PCR (qPCR) targeting lytA and piaA genes specific for S. pneumoniae. A sample was considered positive if signals for both genes were detected. Altogether 105 (39%) individuals were classified as positive for pneumococcus by qPCR including 50 (19%) in trans-nasal and 94 (35%) in trans-oral settings. Although significantly more trans-nasal compared to trans-oral samples were culture-positive for S. pneumoniae at the primary diagnostic step (p<0.001) the opposite was observed in qPCR results (p<0.001). To confirm the presence of live pneumococcus in samples positive by qPCR but negative at the initial diagnostic step, we serially-diluted cell harvests, re-cultured and carefully examined for S. pneumoniae presence. Live pneumococci were recovered from an additional 43 parents including 42 positive in trans-oral and 4 in trans-nasal samples increasing the number of individuals culture- and qPCR-positive to 93 (35%) and positive by either of two methods to 107 (40%). There were significantly more trans-oral than trans-nasal samples positive for pneumococcus by both culture and qPCR (n = 71; 27%; vs. n = 50; 19%; p<0.05). Our data suggest that pneumococcal colonization is more common in adults than previously estimated and point towards the superiority of a trans-oral over a trans-nasal approach when testing adults for colonization with S. pneumoniae.
Respiratory infectious diseases are mainly caused by viruses or bacteria that often interact with one another. Although their presence is a prerequisite for subsequent infections, viruses and bacteria may be present in the nasopharynx without causing any respiratory symptoms. The upper respiratory tract hosts a vast range of commensals and potential pathogenic bacteria, which form a complex microbial community. This community is assumed to be constantly subject to synergistic and competitive interspecies interactions. Disturbances in the equilibrium, for instance due to the acquisition of new bacteria or viruses, may lead to overgrowth and invasion. A better understanding of the dynamics between commensals and pathogens in the upper respiratory tract may provide better insight into the pathogenesis of respiratory diseases. Here we review the current knowledge regarding specific bacterial–bacterial and viral–bacterial interactions that occur in the upper respiratory niche, and discuss mechanisms by which these interactions might be mediated. Finally, we propose a theoretical model to summarize and illustrate these mechanisms.
Meningococci produce a penta-acylated instead of hexa-acylated lipid A when their lpxL1 gene is inactivated. Meningococcal strains with such lipid A endotoxin variants have been found previously in adult meningitis patients, where they caused less blood coagulopathy because of decreased TLR4 activation.
A cohort of 448 isolates from patients with invasive meningococcal disease in the Netherlands were screened for the ability to induce IL-6 in monocytic cell Mono Mac 6 cells. The lpxL1 gene was sequenced of isolates, which show poor capacity to induce IL-6.. Clinical characteristics of patients were retrieved from hospital records.
Of 448 patients, 29 (6.5%) were infected with meningococci expressing a lipid A variant strain. Lipid A variation was not associated with a specific serogroup or genotype. Infections with lipid A variants were associated with older age (19.3 vs. 5.9 (median) years, p = 0.007) and higher prevalence of underlying comorbidities (39% vs. 17%; p = 0.004) compared to wild-type strains. Patients infected with lipid A variant strains had less severe infections like meningitis or shock (OR 0.23; 95%CI 0.09–0.58) and were less often admitted to intensive care (OR 0.21; 95%CI 0.07–0.60) compared to wild-type strains, independent of age, underlying comorbidities or strain characteristics.
In adults with meningococcal disease lipid A variation is rather common. Infection with penta-acylated lipid A variant meningococci is associated with a less severe disease course.
This study evaluated effects of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D-conjugate vaccine (PHiDCV) compared with the 7-valent vaccine on nasopharyngeal bacterial colonization, specifically nontypeable Haemophilus influenzae (NTHi). PHiD-CV had no differential effect on nasopharyngeal NTHi colonization.
Background. This study evaluated the effects of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D–conjugate vaccine (PHiD-CV) on nasopharyngeal bacterial colonization compared with the 7-valent pneumococcal conjugate vaccine (7vCRM) in young children.
Methods. A randomized controlled trial in the Netherlands, initiated 2 years after 7vCRM introduction, was conducted between 1 April 2008 and 1 December 2010. Infants (N = 780) received either PHiD-CV or 7vCRM (2:1) at 2, 3, 4, and 11–13 months of age. Nasopharyngeal samples taken at 5, 11, 14, 18, and 24 months of age were cultured to detect Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, and Staphylococcus aureus. Polymerase chain reaction assays quantified H. influenzae and S. pneumoniae and confirmed H. influenzae as nontypeable (NTHi). Primary outcome measure was vaccine efficacy (VE) against NTHi colonization.
Results. In both groups, NTHi colonization increased with age from 33% in 5-month-olds to 65% in 24-month-olds. Three months postbooster, VE against colonization was 0.5% (95% confidence interval [CI], −21.8% to 18.4%) and VE against acquisition 10.9% (95% CI, −31.3% to 38.9%). At each sampling moment, no differences between groups in either NTHi prevalence or H. influenzae density were detected. Streptococcus pneumoniae (range, 39%–57%), M. catarrhalis (range, 63%–69%), and S. aureus (range, 9%–30%) colonization patterns were similar between groups.
Conclusions. PHiD-CV had no differential effect on nasopharyngeal NTHi colonization or H. influenzae density in healthy Dutch children up to 2 years of age, implying that herd effects for NTHi are not to be expected. Other bacterial colonization patterns were also similar.
Clinical Trials Registration NCT00652951.
pneumococcal conjugate vaccination; nasopharyngeal bacterial colonization; carriage; nontypeable Haemophilus influenza; Streptococcus pneumonia
High rates of potentially pathogenic bacteria and respiratory viruses can be detected in the upper respiratory tract of healthy children. Investigating presence of and associations between these pathogens in healthy individuals is still a rather unexplored field of research, but may have implications for interpreting findings during disease.
We selected 986 nasopharyngeal samples from 433 6- to 24-month-old healthy children that had participated in a randomized controlled trial. We determined the presence of 20 common respiratory viruses using real-time PCR. Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus were identified by conventional culture methods. Information on risk factors was obtained by questionnaires. We performed multivariate logistic regression analyses followed by partial correlation analysis to identify the overall pattern of associations. S. pneumoniae colonization was positively associated with the presence of H. influenzae (adjusted odds ratio 1.60, 95% confidence interval 1.18–2.16), M. catarrhalis (1.78, 1.29–2.47), human rhinoviruses (1.63, 1.19–2.22) and enteroviruses (1.97, 1.26–3.10), and negatively associated with S. aureus presence (0.59, 0.35–0.98). H. influenzae was positively associated with human rhinoviruses (1.63, 1.22–2.18) and respiratory syncytial viruses (2.78, 1.06–7.28). M. catarrhalis colonization was positively associated with coronaviruses (1.99, 1.01–3.93) and adenoviruses (3.69, 1.29–10.56), and negatively with S. aureus carriage (0.42, 0.25–0.69). We observed a strong positive association between S. aureus and influenza viruses (4.87, 1.59–14.89). In addition, human rhinoviruses and enteroviruses were positively correlated (2.40, 1.66–3.47), as were enteroviruses and human bocavirus, WU polyomavirus, parainfluenza viruses, and human parechovirus. A negative association was observed between human rhinoviruses and coronaviruses.
Our data revealed high viral and bacterial prevalence rates and distinct bacterial-bacterial, viral-bacterial and viral-viral associations in healthy children, hinting towards the complexity and potential dynamics of microbial communities in the upper respiratory tract. This warrants careful consideration when associating microbial presence with specific respiratory diseases.
Shifts in pneumococcal serotypes following introduction of 7-valent pneumococcal conjugate vaccine (PCV-7) may alter the presence of other bacterial pathogens co-inhabiting the same nasopharyngeal niche.
Nasopharyngeal prevalence rates of S. pneumoniae, S. aureus, H. influenzae and M. catarrhalis were investigated before, 3 and 4.5 years after introduction of PCV-7 in the national immunisation program in children at 11 and 24 months of age, and parents of 24-month-old children (n≈330/group) using conventional culture methods. Despite a virtual disappearance of PCV-7 serotypes over time, similar overall pneumococcal rates were observed in all age groups, except for a significant reduction in the 11-month-old group (adjusted Odds Ratio after 4.5 years 0.48, 95% Confidence Interval 0.34–0.67). Before, 3 and 4.5 years after PCV-7 implementation, prevalence rates of S. aureus were 5%, 9% and 14% at 11 months of age (3.59, 1.90–6.79) and 20%, 32% and 34% in parents (1.96, 1.36–2.83), but remained similar at 24 months of age, respectively. Prevalence rates of H. influenzae were 46%, 65% and 65% at 11 months (2.22, 1.58–3.13), 52%, 73% and 76% at 24 months of age (2.68, 1.88–3.82) and 23%, 30% and 40% in parents (2.26, 1.58–3.33), respectively. No consistent changes in M. catarrhalis carriage rates were observed over time.
In addition to large shifts in pneumococcal serotypes, persistently higher nasopharyngeal prevalence rates of S. aureus and H. influenzae were observed among young children and their parents after PCV-7 implementation. These findings may have implications for disease incidence and antibiotic treatment in the post-PCV era.
Whooping cough is a respiratory disease caused by Bordetella pertussis, which induces mucosal IgA antibodies that appear to be relevant in protection. Serum IgA responses are measured after pertussis infection and might provide an additional role in pertussis diagnostics. However, the possible interfering role for pertussis vaccinations in the induction of serum IgA antibodies is largely unknown.
We compared serum IgA responses in healthy vaccinated children between 1 and 10 years of age with those in children who despite vaccinations recently were infected with Bordetella pertussis. All children have been vaccinated at 2, 3, 4 and 11 months of age with either the Dutch whole-cell pertussis (wP) vaccine or an acellular pertussis (aP) vaccine and additionally received an aP booster vaccination at 4 years of age. Serum IgA responses to pertussis toxin (PT), filamentous heamagglutinin (FHA) and pertactin (Prn) were measured with a fluorescent multiplex bead-based immuno-assay. An ELISPOT-assay was used for the detection of IgA-memory B-cells specific to these antigens. Serum IgA levels to all pertussis vaccine antigens were significantly higher in infected children compared with healthy children. High correlations between anti-PT, anti-FHA or anti-Prn IgA and IgG levels were found in infected children and to some degree in wP primed children, but not at all in aP primed children. Highest numbers of IgA-pertussis-specific memory B-cells were observed after infection and generally comparable numbers were found after wP and aP vaccination.
This study provides new insight in the diagnostic role for serum IgA responses against PT in vaccinated children. Since aP vaccines induce high serum IgG levels that interfere with pertussis diagnostics, serum IgA-PT levels will provide an additional diagnostic role. High levels of serum IgA for PT proved specific for recent pertussis infection with reasonable sensitivity, whereas the role for IgA levels against FHA and Prn in diagnosing pertussis remains controversial.
All children and adolescents between 1 and 19 years of age in The Netherlands received a single meningococcal serogroup C conjugate (MenCC) vaccine in 2002. During follow-up 4–5 years later, the persistence of MenC polysaccharide-specific IgG was found to be dependent on age of vaccination with higher IgG levels in the oldest immunized age categories.
Methods and Findings
Two cross-sectional population-based serum banks, collected in 1995/1996 and in 2006/2007, were used for this study. We measured MenC polysaccharide-specific IgM, the IgG1 and IgG2 subclasses and determined the avidity of the IgG antibodies. We report that the age-related persistence of IgG after immunization with the MenCC vaccine seemed to result from an increase of IgG2 levels with age, while IgG1 levels remained stable throughout the different age-cohorts. Furthermore, an age-related increase in IgM levels was observed, correlating with the persistence of IgG antibodies with age. It is noteworthy that the increase in IgG2 correlated with a reduced IgG-avidity with age.
These date indicate that the classical characteristics of a T-cell-dependent antibody response as elicited by protein based vaccines might not be completely applicable when conjugate vaccines are administered to older children and adolescents up to 18 years of age. The response elicited by the MenCC vaccine seemed to be more a mixture of both T cell dependent and T cell independent responses in terms of humoral immunological characteristics.
Heptavalent pneumococcal conjugate vaccine (PCV7) shifts nasopharyngeal colonisation with vaccine serotype pneumococci towards nonvaccine serotypes. Because of the reported negative association of vaccine serotype pneumococci and Staphylococcus aureus in the nasopharynx, we explored the effect of PCV7 on nasopharyngeal colonisation with S. aureus in children and parents.
This study was part of a randomised controlled trial on the effect of PCV7 on pneumococcal carriage, enrolling healthy newborns who were randomly assigned (1∶1∶1) to receive PCV7 (1) at 2 and 4 months of age (2) at 2, 4 and 11 months or (3) no PCV7 (controls). Nasopharyngeal colonisation of S. aureus was a planned secondary outcome. Nasopharyngeal swabs were obtained from all children over a 2-year period with 6-months interval and from one parent at the child's age of 12 and 24 months and cultured for Streptococcus pneumoniae and S. aureus. Between July 2005 and February 2006, 1005 children were enrolled and received either 2-doses of PCV7 (n = 336), 2+1-doses (336) or no dose (n = 333) before PCV7 implementation in the Dutch national immunization program. S. aureus colonisation had doubled in children in the 2+1-dose group at 12 months of age compared with unvaccinated controls (10.1% versus 5.0%; p = 0.019). A negative association for co-colonisation of S. pneumoniae and S. aureus was observed for both vaccine serotype (adjusted odds ratio (aOR) 0.53, 95% confidence interval (CI) 0.38–0.74) and nonvaccine serotype pneumococci (aOR 0.67, 95% CI 0.52–0.88).
PCV7 induces a temporary increase in S. aureus colonisation in children around 12 months of age after a 2+1-dose PCV7 schedule. The potential clinical consequences are unknown and monitoring is warranted.
In 2002 a Meningococcal serogroup C (MenC) conjugate vaccine, with tetanus toxoid as carrier protein, was introduced in the Netherlands as a single-dose at 14 months of age. A catch-up campaign was performed targeting all individuals aged 14 months to 18 years. We determined the MenC-specific immunity before and after introduction of the MenC conjugate (MenCC) vaccine.
Methods and Findings
Two cross-sectional population-based serum banks, collected in 1995/1996 (n = 8539) and in 2006/2007 (n = 6386), were used for this study. The main outcome measurements were the levels of MenC polysaccharide(PS)-specific IgG and serum bactericidal antibodies (SBA) after routine immunization, 4–5 years after catch-up immunization or by natural immunity. There was an increasing persistence of PS-specific IgG and SBA with age in the catch-up immunized cohorts 4–5 years after their MenCC immunization (MenC PS-specific IgG, 0.25 µg/ml (95%CI: 0.19–0.31 µg/ml) at age 6 years, gradually increasing to 2.34 µg/ml,(95%CI: 1.70–3.32 µg/ml) at age 21–22 years). A comparable pattern was found for antibodies against the carrier protein in children immunized above 9 years of age. In case of vaccination before the age of 5 years, PS-specific IgG was rapidly lost. For all age-cohorts together, SBA seroprevalence (≥8) increased from 19.7% to 43.0% in the pre- and post-MenC introduction eras, respectively. In non-immunized adults the SBA seroprevalence was not significantly different between the pre- and post-MenC introduction periods, whereas PS-specific IgG was significantly lower in the post-MenC vaccination (GMT, age ≥25 years, 0.10 µg/ml) era compared to the pre-vaccination (GMT, age ≥25 years, 0.43 µg/ml) era.
MenCC vaccination administered above 5 years of age induced high IgG levels compared to natural exposure, increasing with age. In children below 14 months of age and non-immunized cohorts lower IgG levels were observed compared to the pre-vaccination era, whereas functional levels remained similar in adults. Whether the lower IgG poses individuals at increased risk for MenC disease should be carefully monitored. Large-scale introduction of a MenCC vaccine has led to improved protection in adolescents, but in infants a single-dose schedule may not provide sufficient protection on the long-term and therefore a booster-dose early in adolescence should be considered.