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Objective: To determine the impact of pre-vaccination nutritional status on vaccine responses in Venezuelan Warao Amerindian children vaccinated with the 13-valent pneumococcal conjugate vaccine (PCV13) and to investigate whether saliva can be used as read-out for these vaccine responses., Methods: A cross-sectional cohort of 504 Venezuelan Warao children aged 6 weeks - 59 months residing in nine geographically isolated Warao communities were vaccinated with a primary series of PCV13 according to Centers for Disease Control and Prevention (CDC)-recommended age-related schedules. Post-vaccination antibody concentrations in serum and saliva of 411 children were measured by multiplex immunoassay. The influence of malnutrition present upon vaccination on post-vaccination antibody levels was assessed by univariate and multivariable generalized estimating equations linear regression analysis., Results: In both stunted (38%) and non-stunted (62%) children, salivary antibody concentrations correlated well with serum levels for all serotypes with coefficients varying from 0.61 for serotype 3-0.80 for serotypes 5, 6A and 23F (all p < 0.01). Surprisingly, higher serum and salivary antibody levels were observed with increasing levels of stunting in children for all serotypes. This was statistically significant for 5/13 and 11/13 serotype-specific serum and saliva IgG concentrations respectively., Conclusion: Stunted Amerindian children showed generally higher antibody concentrations than well-nourished children following PCV13 vaccination, indicating that chronic malnutrition influences vaccine response. Saliva samples might be useful to monitor serotype-specific antibody levels induced by PCV vaccination. This would greatly facilitate studies of vaccine efficacy in rural settings, since participant resistance generally hampers blood drawing., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Purpose: The introduction of a 7-valent conjugate pneumococcal vaccine (PCV7) in children largely affected the prevalence of adult pneumococcal pneumonia. In this study we investigated whether the clinical severity of adult bacteremic pneumococcal pneumonia has also altered following the introduction of pediatric PCV7 vaccination., Methods: Adults hospitalized with bacteremic pneumococcal pneumonia between 2001 and June 2011 at two Dutch hospitals were included retrospectively. Clinical data on patient characteristics, comorbidities and severity of disease were obtained and pneumococcal serotypes were determined., Results: Among 343 patients investigated, those infected with PCV7 serotypes had a higher PSI score (p=0.0072) and mortality rate (p=0.0083) compared with the remainder of the cohort. Since the introduction of PCV7 the proportion of pneumococcal pneumonias caused by serotypes 1 and 7F (p-values 0.037 and 0.025) increased, as well as the rate of pleural effusion and empyema (p-values 0.011 and 0.049). Whilst de proportion of adults infected with PCV7 serotypes decreased after the introduction of PCV7 (p=0.015), PSI scores in these patients remained higher (p=0.030), although mortality rates between PCV7 and non PCV7 types equalized. After the introduction of PCV7 a marked shortening in hospital stay was observed only among patients infected with non PCV7 serotypes (p=0.019)., Conclusions: The introduction of pediatric PCV7 vaccination was accompanied by subtle changes in clinical severity of adult bacteremic pneumococcal pneumonia. Expansion of serotypes covered by pneumococcal vaccination may again influence the clinical presentation of disease., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background and Aims: We evaluated the immunogenicity of the 7-valent pneumococcal conjugate vaccine (PCV7), and its impact on pneumococcal carriage in Venezuelan children at high risk for invasive pneumococcal disease (IPD)., Methods: 82 children (age 2-59 months) with sickle cell anemia (n=22), chronic heart disease (n=19), HIV infection (n=12), immune-suppressive therapy (n=11) and other IPD-predisposing conditions (n=18) were vaccinated with PCV7 according to CDC-recommended age-related immunization schedules. Blood samples were taken to determine the concentration of IgG antibody, and nasopharyngeal swabs were obtained to isolate Streptococcus pneumoniae, before the first vaccine dose and 1 month after completion of the vaccination schedule., Results: Pneumococcal carriage prior to the first immunization was 27% (n=22), with the most frequently carried serotypes being vaccine serotypes 6B (22%) and 14 (13%). One month after completion of the vaccination scheme pneumococcal carriage was 22% (n=17), dominated by non-vaccine serotypes 19A (24%) and 7F (12%). Before immunization, 65% of the subjects had IgG antibody titers >0.35 μg/mL for five serotypes tested. Post-vaccination, 100% of the subjects showed titers >1.0 μg/mL for all PCV7 serotypes with geometric mean concentrations (GMC) ranging from 1.75 μg/mL (serotype 23F) to 17.16 μg/mL (serotype 14). Children previously colonized with serotype 6B had a significantly lower GMC to this serotype following immunization than children not carrying 6B prior to the first PCV dose (p<0.05)., Conclusions: PCV7 is highly immunogenic in Venezuelan children at high-risk for IPD. Vaccination was associated with an immediate shift in nasopharyngeal carriage toward non-PCV7 serotypes. Finally, we observed serotype-specific hyporesponsiveness to immunization after natural carriage with the same serotype in high-risk children., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

We report the development of a novel protein-based nasal vaccine against Streptococcus pneumoniae, in which three pneumococcal proteins were displayed on the surface of a non-recombinant, killed Lactococcus lactis-derived delivery system, called Gram-positive Enhancer Matrix (GEM). The GEM particles induced the production of the proinflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) by macrophages as well as the maturation of dendritic cells. The pneumococcal proteins IgA1 protease (IgA1p), putative proteinase maturation protein A (PpmA) and streptococcal lipoprotein A (SlrA) were anchored in trans to the surface of the GEM particles after recombinant production of the antigens in L. lactis as hybrids with a lactococcal cell wall binding domain, named Protein Anchor domain (PA). Intranasal immunisation with the SlrA-IgA1p or trivalent vaccine combinations without additional adjuvants showed significant protection against fatal pneumococcal pneumonia in mice. The GEM-based trivalent vaccine is a potential pneumococcal vaccine candidate that is expected to be easy to administer, safe and affordable to produce.

The present work reports the use of non-living non-recombinant bacteria as a delivery system for mucosal vaccination. Antigens are bound to the cell-wall of pretreated Lactococcus lactis, designated as Gram-positive enhancer matrix (GEM), by means of a peptidoglycan binding domain. The influence of the GEM particles on the antigen-specific serum antibody response was studied. Following nasal immunization with the GEM-based vaccines, antibody responses were induced at systemic and local levels. Furthermore, different GEM-based vaccines could be used consecutively in the same mice without adverse effects or loss of activity. Taken together, the results evidence the adjuvant properties of the GEM particles and indicate that GEM-based vaccines can be used repeatedly and are particularly suitable for nasal immunization purposes.

Apart from the use of oral rehydration solution, there are currently no treatment modalities for rotavirus induced diarrhoea, which is particularly relevant to developing countries. Fragments derived from llama heavy chain antibodies were previously shown to be highly stable, efficiently produced in yeast and exhibiting high epitope specific affinity. We now aim to demonstrate that these antibody fragments are capable of reducing morbidity of rotavirus induced diarrhoea. Here we show the isolation of rotavirus specific antibody fragments and their capability of reducing the morbidity of rotavirus induced diarrhoea in vivo in mice. They could provide a treatment modality for the moderation of human rotavirus infections having a significant impact on the course of an often fatal childhood disease.

Aim: In a prospective controlled study in young children with a history of recurrent acute otitis media, we analyzed the salivary IgA and IgG antibody titers upon vaccination with a 7-valent pneumococcal conjugate vaccine (PCV) given once or twice, followed by a 23-valent polysaccharide booster vaccination., Methods: Salivary IgA and IgG antibody concentrations to vaccine serotype 6B, 14, 18C and 19F were measured by enzyme immunoassay in 38 samples of children vaccinated with PCV and 45 control samples. In the PCV group, 12 samples were taken prior to vaccination, 12 samples 4 weeks after the polysaccharide booster (8 months after the first conjugate vaccination) and 14 samples 7 months after the last vaccination (14 months after the first conjugate vaccination). In the control group 15 children were sampled at each of these three time points., Results: We observed an increase in salivary IgG antibody concentrations against serotype 6B, 14, and 18C 14 months after the primary vaccination in children vaccinated with PCV twice, although this was significant for serotype 14 only. There was no increase in salivary IgG antibody in children vaccinate with PCV once nor in control children. IgA antibody titers increased significantly after 8 and after 14 months in both the pneumococcal vaccine recipients and the controls. However, the observed increase in mean antibody titers was significantly higher in control children compared to the PCV group., Conclusion: We suggest that repeated pneumococcal conjugate vaccination is necessary to induce an increase in salivary IgG antibodies and effectuate clearance of S. pneumoniae from the nasopharyngeal mucosa of children with recurrent acute otitis media. We hypothesize that the increase in salivary IgA is caused by the local boosting of the mucosal immune response by carriage and recurrent infections, which occurs less often in the PCV group compared to the control children.

Pneumococcal conjugate vaccination is highly efficacious against invasive diseases in young children. Since host protection is mainly mediated by opsonin-dependent phagocytosis, the in vitro measurement of opsonophagocytic activity of the anti-capsular antibodies is assumed to be a reliable correlate of protection to monitor vaccine efficacy. Unfortunately, the methods used so far are all tedious to perform and material-consuming. Therefore, we modified the multi-specificity opsonophagocytosis killing assay (MSOPKA) into a high-throughput method, which simultaneously measures the opsonophagocytosis against the seven serotypes covered by the current conjugate vaccine in a single assay. In the so-called multiplex opsonophagocytosis assay (MOPA), a mixture containing equal numbers of colony forming units (CFUs) of chloramphenicol-resistant serotype 4, spectinomycin-resistant serotype 6B, streptomycin-resistant serotype 9V, erythromycin-resistant serotype 14, rifampicin-resistant serotype 18C, tetracycline-resistant serotype 19F, and trimethoprim-resistant serotype 23F pneumococci was used as a target mixture and incubated with serial dilutions of test serum. After opsonophagocytosis by differentiated HL-60 cells in the presence of complement, the samples were spotted onto different blood agar plates containing the seven selective antibiotics, respectively. Opsonophagocytosis was calculated as the highest serum dilution resulting in 90% or more reduction in CFUs. The data obtained by this assay correlated well with the data obtained by the MSOPKA. In conclusion, the MOPA simultaneously measures opsonophagocytosis capacity of serum against the capsular serotypes included in the 7-valent pneumococcal conjugate vaccine in a high-throughput fashion, requiring low volumes of patient sera.

Surface associated pneumococcal proteins alpha-enolase (Eno), immunoglobulin A1 protease (Iga), streptococcal lipoprotein rotamase A (SlrA), and putative proteinase maturation protein A (PpmA) have potential as candidates for future protein-based anti-pneumococcal vaccines. The immunogenicity of these proteins were studied in a cohort of 329 children during their first two years of life. During the first recorded episode of otitis media, acute and convalescent phase sera were available from 151 children. Concentrations of antibodies against Eno, Iga, SlrA and PpmA were measured by EIA and detected in 99% (300/302), 95% (288/302), 95% (288/302), and 83% (251/302) of the sera, respectively. There were no statistically significant differences between the groups of children with and without a history of pneumococcal contact or with respect to the type of pneumococcal contact. Despite a mean overall decrease in the antibody titers in the convalescent sera following AOM, several children were able to respond with a more than twofold increase in antibody titer in response to AOM. The majority of the children with increased antibody concentrations appeared in the groups, which were colonized with pneumococci at the time of serum collection, but were recorded as having no prior contact with pneumococci. In conclusion, SlrA, PpmA, Eno and Iga are immunogenic proteins that elicit antibody responses early in life. No significant correlation between antibody titers to these proteins and pneumococcal carriage or infection was found. Presumably, this results from the presence of cross-reactive epitopes on commensal bacteria.

Streptococcus pneumoniae is a major cause of morbidity and mortality in infants, children and the elderly. Despite the availability of excellent antimicrobial therapy and adequate health care systems, respiratory diseases and invasive infections caused by pneumococci still comprise a major health problem. The emerging resistance to penicillin and other commonly used antibiotics underscores the importance of the development of novel vaccine strategies to combat pneumococcal disease. Although the 23-valent polysaccharide (PS) vaccine is immunogenic and protective in most adults and children over 5 years of age, they fail to protect children under 2 years of age. Fortunately, the recent conjugate vaccines have shown to be highly efficacious in preventing invasive diseases in this risk group. Moreover, promising results regarding prevention of pneumonia and acute otitis media have been published. Unfortunately, protection is raised against a limited number of pneumococcal serotypes, and serotype replacement and subsequent vaccine failure have become a serious concern. Currently, several pneumococcal surface proteins are considered as alternative vaccine candidates because of their serotype-independence. Thus far, pneumococcal surface adhesin A (PsaA) has proven to be highly protective against colonization in animal models. Moreover, pneumococcal surface protein A (PspA) and pneumolysin have shown to elicit protection against invasive diseases. Future research will elucidate their true potential in protecting humans. In this paper we discuss the present knowledge on pneumococcal vaccines and the current status of novel vaccine strategies.