Vaccination against gonorrhoea: the potential protective effect of immunization with a synthetic peptide containing a conserved epitope of gonococcal outer membrane protein IB.

Monoclonal antibody SM24 recognizes a protective, highly conserved but non-immunogenic epitope on outer membrane protein PIB of Neisseria gonorrhoeae. A series of overlapping synthetic peptides, spanning the deduced amino acid sequence of PIB from strain R10, have been synthesized on solid phase supports. Monoclonal antibody SM24 reacted with two adjacent decapeptides corresponding to residues 191-200 and 196-205, containing the common sequence TYSIP. Following localization of the epitope recognized, a peptide was synthesized corresponding to residues 193-204. The peptide was coupled to a carrier protein (KLH) and both the free peptide and peptide-KLH conjugate were used for immunization of rabbits. The resulting antisera reacted with the immunizing peptide, with denatured PIB on Western blots and, in addition, with native PIB in outer membranes of both the homologous and a heterologous strain. In the presence of human complement the sera were bactericidal for both the homologous and the heterologous strain. Thus synthetic peptides may be used to induce a protective polyclonal immune response against epitopes on gonococcal PI which are normally only weakly or non-immunogenic.