Preparation of monoclonal antibodies agglutinating group A, type 4 streptococci

BALB/C mice were immunized with a partially purified M-protein fraction prepared from hot acid-extracts of a type 4, group A streptococcus, strain SS91. Two samples of monoclonal antibodies (MAb) were obtained from hybridoma cells of antibody producing spleen cells fused with NS-1 myeloma cells. Both MAb were of the subclass IgG1 having kappa-type light chains. The MAb agglutinated trypsin-digested cells of type 4 strains, but not of types 1, 2, 18, 28 and 41. This type 4-cell agglutination was inhibited by extracts of type 4 cells; strongly by hot acid-extract and partially by trypsin-extract. Hot acid-extract of type 41 cells had no inhibitory effect. Sandwich-enzyme-linked immunosorbent assay of the MAb and partially purified M-protein preparation combination against commercial T-typing sera showed that only T-type 4 antiserum reacted with the combination system. From these data, we thought that the MAb preparations were not directed to M-protein but to T-protein of type 4, group A streptococci.