Capsular hyaluronic acid of Group A Streptococci hampers their invasion into human pharyngeal epithelial cells

Group A streptococci (GAS) cause various diseases, from uncomplicated nonin vasive, to severe invasive infections. Capsular hyaluronic acid (HA) is kno wn to resist phagocytosis, however, interaction between HA and epithelial c ells have not been clearly understood. In this study, both HA-producing wil d strains and HA-nonproducing mutants were employed to examine their invasi veness into confluent cultures of HEp-2, a nonphagocytic human epithelial c ell line. Invasion of HEp-2 cells by GAS strains increased over time. The h asA gene encoding hyaluronate synthase of GAS strains was inactivated by al lelic replacement. It was found that hasA-inactivated mutants were internal ized into HEp-2 cells more efficiently than their parent strains under vari ous conditions in terms of incubation time and inoculum size. Taken togethe r, these findings indicate that GAS can be internalized into HEp-2 cells wi th considerably high frequencies and that the presence of HA of GAS decreas ed the invasion efficiency. (C) 1999 Academic Press.