IMMUNOCHEMISTRY OF GONOCOCCAL LIPOOLIGOSACCHARIDE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project continues studies of how liooligosaccharide (LOS) mimicry of human glycosphingolipids (GSL) enables the transmission of Neisseria gonorrhoeae in order to find ways to prevent it. LOW are outer membrane glycolipids that have a glycose moiety that consists of proximal Basal Region and three short distal chains, termed _, _, and _. Many _ chain oligosaccharides are structurally identical to those of lacto- (Lac-R), globo- (P_(Gb3) and P1), paraglobo- (lacto-N-neotetraose (LNnT)), and gangliosyl (GalNAc_1-LNnT) series GSL. LOS are involved in attachment to and invasion of epithelial cells, and in evasion of immune clearance mechanisms. Gonococci shed during gonorrhoea make larger LOS. The higher M_ LOS made by MS1lmkC -- a strain used in human experimentation -- have polylactosamine structures. Polylactosaminylation explains the higher M_ molecules of this variant, but not those of others. Some serum resistant (ser_) gonococcal strains extend the LOS _ chain to form an _-lactose that is parallel to the _-lactose of the a chain, and meningococci can extend the _ chain. We are structuring higher M_ LOS made by clinical isolates: LOS made by ser_ strains, and LOS that appear to have higher order (Gb4 and P-1) globosyl oligosaccharides that are isobaric with paraglobosyl and gangliosyl LOS, respectively. We particularly want to know whether higher M_ LOS have parallel GSL-like antennae that could crosslink epithelial cell receptors. We will continue to rely on mass spectrometric techniques, but will also utilize high pH anion exchange chromatographic analyses. We know little about the lipoidal moieties of gonococcal LOS. This information is needed because the lipoidal moiety influences the conformation of the glycose moiety in ways that affect the latter's ability to bind glycoproteins, including antibodies. Available structural information from degraded LOS leaves unexplored the known O-acyl lipoidal moiety heterogeneity. We will profile gonococcal lipoidal moiety heterogeneity among strains, and perform more complete structural analysis on the lipoidal groups from select strains. Mabs have been used extensively in studies of gonococcal pathogenesis as surrogates for glycose structures. However, we do not have mAbs that discriminate among known glycose structures, much less for those that have yet to be found. We plan to expand our library of mAbs to include additional specificities. These mAbs will be necessary for complete studies of the role of LOS in pathogenesis.