Role of humoral immune response to group A streptococcal pyrogenic exotoxins in rheumatic fever.

Group A streptococci (GAS) are known to be responsible for a wide range of human diseases. GAS pathogenesis is caused by several virulence factors including several pyrogenic exotoxins (Spes) such as SpeA, SpeB, SpeF, and SpeC. Spes are members of the superantigen (SAg) family that induces massive secretion of inflammatory cytokines. So far no direct evidence-has been reported on the participation of GAS proteins in the pathogenesis of acute rheumatic fever (ARF). In the present study the presence of neutralizing antibodies and total ELISA anti Spes antibodies were determined in plasma of 45 ARF patients in order to clarify the role of GAS SpeA, SpeB, SpeC and SpeF in Egyptian ARF patients. No difference was recognized in the level of total ELISA anti-Spes antibodies between ARF patients and healthy controls. On the other hand, percent inhibition to SpeA, by neutralizing antibodies, was significantly higher in plasma of ARF patients with arthritis than with carditis, while no SpeA neutralizing antibodies were recognized in plasma of healthy controls. It is concluded that antibody response to GAS Spes seems to have no direct role in the pathogenesis of RF/RHD. However, detection of neutralizing antibodies might help in identifying the Spes causing RF in a specific population.