Induction of antibodies by Staphylococcus aureus nasal colonization in young children

Abstract In order to develop novel anti-staphylococcal strategies, understanding the determinants of carriage and how humans respond to Staphylococcus aureus exposure is essential. Here, the primary S. aureus-specific humoral immune response and its association with nasal colonization was studied in young children. Sera of fifty-seven (non) colonized children serially collected at birth, 6, 14 and 24 months, were analyzed for IgG, IgA and IgM binding to 19 staphylococcal proteins using flow-cytometry based technology. The antibody responses showed extensive inter-individual variability. On average, the levels of anti-staphylococcal IgA and IgM increased from birth until the age of two years (P<0.05), whereas the levels of IgG decreased (P<0.001). Placentally transferred maternal IgG did not protect against colonization. In colonized children, IgG and IgA levels to a number of proteins were higher than in non-colonized children. At both 14 and 24 months, IgG levels to Chemotaxis Inhibitory Protein of S. aureus (at 24 months, Median fluorescence intensity; 4928 vs. 13, P<0.01), Extracellular fibrinogen-binding protein (987 vs. 440, P<0.01), Clumping factor B (63 vs. 2, P<0.05) and Iron-surface determinant H (100 vs. 3, P<0.01) were significantly higher in colonized children. Therefore, these proteins seem to play a role in nasal colonization of young children.

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