Studies on the role of outer membrane proteins in the virulence of Neisseria gonorrhoeae

Abstract

The role of surface proteins of Neisseria gonorrhoeae in the pathogenesis of gonorrhoea has been investigated, using colonial opacity variants having different combinations of outer membrane proteins.
The association of variants with leucocytes showed significant differences. In particular a variant containing one protein IIb (molecular weight 28,000) showed reduced association whereas another containing protein Ila (molecular weight 28,5OO) was greatly increased. Since variants containing protein Ila are also resistant to complement mediated serum killing and show enhanced attachment to epithelial cells, variant P9-13 (containing protein Ila as the only variable protein) was used in further attempts to determine the molecular mechanism involved in attachment.
Initially the major outer membrane protein (protein I, molecular weight 36,000) and protein Ila were isolated from outer membranes by an improved method in an antigenically reactive form. These could not however, be used in attachment experiments because it proved impossible to remove the detergent used in their extraction while retaining biological activity. As an alternative an attachment system was devised using intact outer membranes. Outer membranes of variants P9-13 (containing proteins I + Ila) and P9-1 (containing protein I only) were compared in a series of attachment experiments.
It was found that the presence of protein IIa on the surface of variant P9-13 played a significant role in increasing attachment. The surface of variant P9-13 was found to be both more hydrophobic and less negatively charged than that of variant P9-1, which would favour attachment. Evidence of a specific attachment mechanism was also found, involving protein Ila and a carbohydrate structure on the surface of buccal epithelial cells. The implications of these and other findings are discussed.

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