Background: Candidate Group A Streptococcal (GAS) vaccines based on the J8 peptide have demonstrated promising immunogenicity in mice. Bridging assessment of the likely protective efficacy of vaccine-induced antibodies requires a more robust understanding of their role in the human immune response to GAS infection. We investigated the age-specific profile of J8 antibodies and the association between infection exposures and related antibody responses in a series of complementary studies conducted in the Central Division of Fiji.
Methods: Three complementary studies were undertaken in the Fijian population: 1) Cross sectional population serosurvey of 424 individuals without GAS infection; 2) Paired serum collection for assessment of M-specific and J8 antibody responses in 53 GAS-infected schoolchildren; 3) Longitudinal assessment of GAS infection (6 measurements) and immunity (3 measurements) in a cohort of 459 schoolchildren over a 10 month period.
Results: Median J8 antibody levels reached their peak in the 5–14 year age group, decreasing with age thereafter. Elevated antibody levels were observed in the 20–30 year age group, consistent with child/parent exposure. While M-specific antibody increases confirmed antigenically significant exposures, similar increases were not observed for J8 antibodies. Neither J8 antibody responses nor current J8 antibody levels varied by the time since last skin infection or the number of infections experienced.
Conclusion: Our results suggest that natural skin infection does not induce significant J8 antibodies, and that J8 antibodies have a very short half-life following infection. Further investigation is warranted to better understand differences between J8 responses following infection and vaccination.