Abstract
The factors contributing to the development of AGN following infection with a nephritogenic GAS are not well understood. To test the hypothesis that lysogeny with a temperate bacteriophage might confer nephritogenicity, 283 sera from 69 children were examined for presence of IgG and IgM antibodies to M 49 GAS BHase using an enzyme immunoassay (ELISA). Patients were classified as follows: 1) NAGN, 21 patients without AGN, non-nephritogenic GAS infection; 2) NAGN-M49, 31 patients without AGN. nephritogenic M 49 GAS infection; 3) AGN-M49, 15 patients with AGN, M 49 GAS infection; 4) AGN-M57, 2 patients with AGN, M 57 infection. The maximum IgG titer change (log10) was greatest in AGN-M49 (0.71), and was significantly higher than in NAGN-M49 (0.45, p=0.016) or NAGN (0.15, p<0.001). NAGN-M49 also had significantly greater titer changes than NAGN (p<0.001). Both AGN-M49 (0.25) and NAGN-M49 (0.21) had significantly greater maximum IgM titer changes than NAGN (0.10, p=0.004, p<0.001 respectively), but were not different from each other (p=0.46). Magnitude of antibody titer change (≥p.3 log change) differed significantly between individuals infected with M 49 GAS versus other GAS sero-types whether or not AGN was present; highest antibody titer changes (≥0.7 logs), however, were seen following AGN. It was concluded that, despite significant rises in IgG and IgM antibody to BHase, antibody response could not be used to investigate the relationship between lysogeny and AGN due to its presence in both patients with and without AGN following M 49 GAS infection.
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