Immune response to superoxide dismutase in group A streptococcal infection

Extracellular localisation of manganese-dependent superoxide dismutase (SodA) by group A streptococcus (GAS) may have a role in protection of this pathogenic bacterium from exogenously produced reactive oxygen species. In this study we show that SodA is found both in surface protein extracts and in culture supernatants of GAS. To investigate whether SodA is a possible vaccine candidate outbred Quackenbush mice were subcutaneously vaccinated with recombinant SodA. Strong antibody responses which were moderately opsonic were elicited. These antibodies were unable to protect mice from intraperitoneal challenge with M1 GAS. We also show that SodA and p145 (a conserved peptide from the M-protein) antibodies are present at significantly higher levels amongst patients with rheumatic heart disease than in control subjects from the same endemic region. The higher SodA antibody levels in patients may be indicative of a role for this protein in pathogenesis of rheumatic heart disease but are more likely to be a marker of recent or recurrent streptococcal infection.