ESPID Education. Prevaes S. 06/10/11; 7709
Ms. S.M.P.J. Prevaes
Ms. S.M.P.J. Prevaes

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Introduction: Immunological correlates associated with bacterial colonization with S. pneumoniae and S. aureus may provide knowledge for new preventive strategies. We studied natural humoral responses against 18 pneumococcal and 40 staphylococcal proteins in relation to bacterial carriage in PCV-7 immunized and non-immunized children.
Methods: In a randomized controlled trial (NCT00189020), nasopharyngeal samples at 6 weeks, 6, 12, 18 and 24 months were collected for bacterial culture. Serum IgG antibodies against 40 staphylococcal and 18 pneumococcal proteins were analyzed by multiplex flow-cytometry from 116 PCV-7 vaccinated and 91 controls at age 12 and 24 months. IgG levels were related to bacterial colonization with S. pneumoniae and S. aureus.
Results: IgG levels were higher against 6 out of 40 S. aureus proteins (CllfB, ClfA, Efb, CHIPS, LukD and LukE (p<0.001)) in children previously colonized with S. aureus versus non-colonized children. In children previously colonized with pneumococci, IgG levels were higher against 13/18 pneumococcal proteins when compared to non-colonized individuals (p<0.002). Increasing age was associated with higher responses against most pneumococcal proteins (p<0.002) and lower responses against over half of the staphylococcal proteins (p<0.001), reflecting increasing pneumococcal and decreasing staphylococcal carriage between 6 weeks and 24 months of age. Higher antibodies to S. aureus and S. pneumoniae proteins at 12 months were not correlated with protection against colonization with the homologous or heterologous pathogen in the following year. There were no differences in IgG levels between vaccinated and non-vaccinated children.
Conclusions: Colonization with staphylococcus or pneumococcus elicits short lived IgG serum antibodies to many species-specific protein antigens, but none of them appeared protective against colonization with the respective pathogens. No effect of PCV-7 was observed on natural immunity against both pathogens in this RCT setting.
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