Development of natural antibodies to pneumococcal surface protein A, pneumococcal surface adhesin A and pneumolysin in Filipino pregnant women and their infants in relation to pneumococcal carriage.

For vaccine development it is important to know how antibodies develop after natural pneumococcal contacts. This work was done to receive information about the development of natural antibodies to pneumococcal surface protein A (PspA), pneumococcal surface adhesin A (PsaA) and pneumolysin (Ply), in early infancy and to receive information on how nasopharyngeal carriage of Streptococcus pneumoniae in infants affects the antibody concentrations. The antibody concentrations to PspA, PsaA and Ply were measured by EIA in serum samples of 51 pregnant women, in six consecutive serum samples of 173 infants (samples from 7 to 48 weeks of age), as well as in 39 cord bloods. Nasopharyngeal swabs were also collected from the infants and cultured for pneumococci. The geometric mean concentration (GMC) of anti-PspA and -Ply decreased until 18 weeks of age and started to increase thereafter, but was still at 48 weeks lower than in the mothers. The GMC of anti-PsaA in the infants increased significantly by age and reached the GMC of the mothers already at 14 weeks of age. The increase in antibody concentration in the infants was associated with pneumococcal carriage, but followed the different kinetics depending on the antigen. High maternal anti-Ply antibodies were negatively associated with the risk of pneumococcal carriage (OR 0.78, 0.61-0.99). This indicates that high maternal anti-Ply could be associated with lower pneumococcal carriage acquisition in infants.