A high Mr factor in human blood which confers serum resistance on gonococci: some properties and synergism with CMP-NANA

Regulation of gonococcal sialyltransferase, lipooligosaccharide, and serum resistance by glucose, pyruvate, and lactate

Strain F62 of Neisseria gonorrhoeae gonococci (GC) is sensitive to normal human serum unless CMP-N-acetylneuraminic acid (CMP-NANA) is present. NANA is transferred primarily to a 4.5-kDa lipooligosaccharide (LOS) structure by a GC sialyltransferase (Stase). We investigated LOS and Stase expression and serum resistance in strain F62 grown in different carbon sources and growth conditions. Pyruvate-grown GC expressed 1.9- to 5.6-fold more Stase activity than did glucose-grown GC, whereas lactate-grown GC generally expressed intermediate Stase activities. Broth-grown GC expressed two- to fourfold more Stase activity than did plate-grown GC in all carbon sources. Pyruvate- or lactate-grown GC expressed significantly more of the sialylateable 4.5-kDa LOS species than did glucose-grown GC. Anaerobically, the 4.5-kDa LOS species was expressed in greater quantity than the 4.9-kDa N-acetyl galactosamine-terminating species in all carbon sources. Pyruvate-grown GC also incorporated up to threefold more radiolabelled CMP-NANA onto the 4.5-kDa LOS species than did glucose-grown GC. In serum resistance studies, pyruvate-grown GC were 6.5- to 16.1-fold more serum resistant than glucose-grown GC at limiting CMP-NANA concentrations (1.56 to 12.50 microg/ml). Taken together, these results indicate that gonococcal expression of Stase activity is up-regulated by growth in pyruvate or lactate, which correlates with enhanced expression of the sialylateable 4.5-kDa LOS and, for growth in pyruvate, correlates with enhanced sialylation of gonococcal LOS and greater serum resistance. In different in vivo niches, gonococcal LOS sialylation, serum resistance, and interaction with host cells can be highly regulated.

Anaerobic growth and cytidine 5'-monophospho-N-acetylneuraminic acid act synergistically to induce high-level serum resistance in Neisseria gonorrhoeae

In vivo, gonococci encounter a myriad of conditions not present in vitro. At some stages of infection and disease, gonococci may grow anaerobically, probably by using sodium nitrite as a terminal electron acceptor. Also, gonococci sialylate their lipooligosaccharide (LOS) in vivo, by using low concentrations of cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) present in host tissue. This sialylation is responsible for the acquired resistance of gonococci to both normal and immune human serum. Given that gonococci grown in the absence of oxygen or in the presence of CMP-NANA probably more closely resemble gonococci grown inside a human host, we studied the serum resistance of gonococci cultivated under these conditions. In the absence of CMP-NANA, anaerobically grown (anaerobic) gonococci were somewhat less sensitive to serum killing than were aerobically grown (aerobic) gonococci. However, anaerobic gonococci grown with 6 micrograms of CMP-NANA per ml exhibited almost complete serum resistance, while aerobic gonococci required 16-fold-higher CMP-NANA concentrations to achieve significant serum resistance. Anaerobic gonococci incubated in CMP-NANA converted to serum resistance two to three times faster than did similarly treated aerobic gonococci and incorporated up to six times as much sialic acid into their LOS. Gonococci can express several different LOS molecules. Anaerobic gonococci expressed the LOS molecule that acts as an acceptor for sialic acid from CMP-NANA in greater quantity than aerobic gonococci did. Finally, Triton X-100 extracts of anaerobic gonococci contained about four times more sialyltransferase activity than did extracts of aerobic gonococci. Sialyltransferase activity in these extracts was not inhibited by oxygen or enhanced by anaerobiosis. These data indicate that anaerobic conditions lead to altered LOS biosynthesis and to induction of sialyltransferase activity in gonococci. In vivo, where decreased oxygen levels and relevant concentrations of CMP-NANA are found, gonococci could readily become resistant to killing by normal and immune human serum.