Promotion of fibronectin independent invasion by C5a peptidase into epithelial cells in group A Streptococcus.

BACKGROUND & OBJECTIVES Group A Streptococcus, causative agent of several clinical manifestations codes for multiple protein invasins which help the bacterium to enter non-phagocytic cells. C5a peptidase (SCPA) is a surface protein conserved among different serotypes of M1 strain. The present study was taken up to study SCPA promoted fibronectin independent entry of GAS into epithelial cells. METHODS An isogenic 90226 emm1deltaAB (M1(-)) mutant was constructed with thermosensitive pGhost vector. This isogenic M1(-) mutant expressed SCPA on the surface as determined by Western blotting and immunofluorescence. RESULTS On preincubation with anti-SCPA serum, the isogenic M1(-) strain exhibited 54 per cent decreased invasion as compared to the bacteria incubated with control serum. Also, purified recombinant SCPA proteins blocked internalization of M1(-) streptococci into HEp-2 cells. The M1(-) strain invaded at the same efficiency in the presence or absence of fibronectin. INTERPRETATION & CONCLUSION These results suggested that SCPA acted as a potential invasin of group A streptococcus and promoted invasion independent of fibronectin.