Induction of antibodies by Staphylococcus aureus nasal colonization in young children

P>In order to develop novel antistaphylococcal 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 from 57 colonized or non-colonized children, serially collected at birth and at 6, 14 and 24 months, were analysed 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 antistaphylococcal IgA and IgM increased from birth until the age of 2 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 for a number of proteins were higher than in non-colonized children. At both 14 and 24 months, the levels of IgG against chemotaxis inhibitory protein of S. aureus (at 24 months; median fluorescence intensity, 4928 vs. 24, p < 0.05), extracellular fibrinogen-binding protein (987 vs. 604, p < 0.05), and iron-responsive surface determinant H (62 vs. 5, p < 0.05) were significantly higher in colonized children. The levels of IgA against CHIPS, IsdH and IsdA were higher (p < 0.05). Therefore, CHIPS, Efb, IsdA and IsdH seem to play a role in nasal colonization of young children.