EXPRESSION OF SIALYLTRANSFERASE IS NOT REQUIRED FOR INTERACTION OF NEISSERIA-GONORRHOEAE WITH HUMAN EPITHELIAL-CELLS AND HUMAN NEUTROPHILS

Sialyltransferase (Stase) in Neisseria gonorrhoeae organisms (gonococc i [GC]) transfers sialic acid (N-acetylneuraminic acid [NANA]) from cy tidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) mainly to the terminal galactose (Gal) residue in the Gal beta-1,4 N-acetylglucosam ine (Gal-GlcNAc)-R lipooligosaccharide (LOS) structure, Sialylated GC resist killing by normal human serum, sometimes show reduced invasion of epithelial cells, and have reduced adhesion to and stimulation of h uman neutrophils, We questioned whether Stase itself modulates the int eractions of GC with human epithelial cells and neutrophils in the abs ence of exogenous CMP-NANA, To that end, we treated strain F62 with et hyl methanesulfonate and grew similar to 175,000 colonies on CMP-NANA plates, and screened them with monoclonal antibody 1B2-1B7 (MAb 1B2), MAb 1B2 is specific for Gal-GlcNAc and reacts only with asialylated GC , We isolated 13 MAb 1B2-reactive mutants, including five null mutants , that had Stase activities ranging from barely detectable to fivefold less than that of wild-type (WT) F62, The LOS phenotype of Stase null mutants was identical to that of WT F62, yet the mutants could not si alylate their LOS when grown with CMP-NANA. The Stase null phenotype w as rescuable to Stase(+) by transformation,vith chromosomal DNA from W T F62, Stase null mutants remained serum sensitive even when grown wit h CMP-NANA, One Stase null mutant, ST94A, adhered to and invaded the h uman cervical epithelial cell line ME-180 at levels indistinguishable from that of WT F62 in the absence of CMP-NANA. In human neutrophil st udies, ST94A stimulated the oxidative burst in and adhered to human ne utrophils at levels similar to those of WT F62, ST94A and WT F62 were also phagocytically killed by neutrophils at similar levels, These res ults indicate that expression of Stase activity is not required for in teraction of GC with human cells.