Hyaluronate capsule prevents attachment of group A streptococci to mouse peritoneal macrophages

The antiphagocytic properties of the streptococcal hyaluronic acid capsule were explored in a system in which binding of the organism to the phagocyte, but not ingestion, could occur. The capsule was found to be highly effective in preventing attachment of two strains of group A streptococci to mouse peritoneal macrophages. Variation in attachment with phase of growth in broth culture (low in early log phase, high in late-log phase and thereafter) could be accounted for by production and subsequent loss of capsule. Hyaluronidase treatment removed the capsule and increased adherence; treatment with proteolytic enzymes removed M protein and decreased resistance to phagocytosis in whole human blood but did not remove the capsule or increase adherence to the mouse peritoneal macrophages.