Correlation of saliva and serum antibody titre response to pneumococcal capsular polysaccharides

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Madimabe, Metsekae Richard
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Vaal University of Technology
Background: Infants and young children under the age of 2 years are vulnerable to Streptococcus pneumoniae infections, especially those who are born in developing countries. Antibiotic therapy was an effective treatment until resistance to antibiotics emerged, and then vaccines were developed to assistant with the treatment. The first successful conjugate vaccine was the 7-valent pneumococcal conjugate which resulted in a decrease in vaccine serotype IPD in infants and children below the age of two years. Objectives: The main aim of this study was to assess the saliva and serum antibody concentration response to pneumococcal capsular polysaccharides in children vaccinated and unvaccinated. Design: This is a sub-study within a retrospective analysis of a prospective cohort study on the safety and immunogenicity of 7-valent pneumococcal polysaccharide-protein conjugate vaccine (PncCV) and the immunogenicity of a H. influenzae type b conjugate vaccine (HibCV). Setting and participation: Infants aged between ≥ 4 and ≤ 10 weeks were enrolled, who only received BCG and Polio vaccine following birth. Infants were enrolled according to HIV status during routine antenatal screening in the obstetrics wards of the two hospitals, in Johannesburg and Cape Town. Measurements: Saliva IgG and IgA concentrations against pneumococcal capsular polysaccharides serotype 4, 6B, 7F, 9V, 14, 18C, 19F and 23F were quantified a by multiplex bead-based assay using the Luminex technology. Serum IgG against polysaccharides serotype 4, 6B, 7F, 9V, 14, 18C, 19F and 23F were measured by a competitive Enzyme Linked Immuno-Sorbent Assay (ELISA). Results: Post three primary vaccine doses, both serum IgG and saliva IgG and IgA antibody concentrations to vaccine serotypes were protective in children who received the vaccine. The antibody concentration in children whom did not receive the vaccine was much lower in comparison to the vaccine group in both serum and saliva to vaccine serotypes (P = 0.0001). And also high positive correlation (>0.6) was observed of IgG in serum and in saliva following vaccination. Conclusion: Pneumococcal conjugate vaccines induce pneumococcal capsular polysaccharide specific antibodies in both serum and saliva. However, there are differences between the vaccines’ ability to induce mucosal immune response and there are also serotype specific differences in the antibody concentrations and in the proportion of positive samples after a series of vaccinations. The pneumococcal conjugate vaccine in this study was able to induce mucosal immune memory: the anti-pneumococcal IgA concentrations also increased with age in the saliva of unvaccinated children.
M. Tech. (Biotechnology, Faculty of Applied and Computer Sciences)|, Vaal University of Technology.