ANTI-HSP65 ANTIBODIES RECOGNIZE M-PROTEINS OF GROUP-A STREPTOCOCCI

Group A streptococcal M protein and the mycobacterial heat shock prote in, hsp65, are strong bacterial immunogens that have been linked to ar thritis and autoimmunity. Recent evidence has shown that streptococcal arthritis and adjuvant arthritis may be related to epitopes shared be tween group A streptococci and hsp65. We investigated the possibility that immunological similarities were shared between streptococcal M pr otein and hsp65. Antibodies against the 65-kDa heat shock protein of M ycobacterium tuberculosis were tested for reactivity with group A stre ptococci and purified recombinant M proteins (rM5 and rM6). Rabbit pol yclonal anti-hsp65 serum was highly reactive with M type 5 Streptococc us pyrogenes and rM5 and rM6 proteins in an enzyme-linked immunosorben t assay (ELISA). A mouse anti-hsp65 monoclonal antibody (MAb), IIC8, r eacted with streptococcal M types 5, 6, 19, 24, and 49 in an ELISA but showed no reactivity with an isogenic streptococcal mutant which did not express M protein. Anti-hsp65 MAb IIC8 recognized rM5 and rM6 prot eins in the ELISA, and MAbs IIC8 and IIH9 reacted strongly with rM6 pr otein in Western immunoblots. The binding of M protein by anti-hsp65 M Abs was shown to be inhibited by both hsp65 and M protein. These data show that anti-hsp65 antibodies recognize streptococcal M proteins.