Antibodies elicited by immunization with cyclic synthetic peptides comprising the entire sequence of meningococcal PorA loop 1 subtype P1.19 recognize the outer membranes of Neisseria meningitidis

The possibility was studied of eliciting antibodies that are able to recognize Neisseria meningitidis outer membranes by immunizing with synthetic peptides containing the sequence of the exposed loop 1 (variable region 1 or VR1) subtype P1.19 from meningococcal PorA protein. It has been shown that the antibodies elicited by immunization with a cyclic synthetic peptide containing the apex amino acids of the PorA P1.19, fail to recognize the native PorA protein. In the current study we tested a cyclic synthetic peptide containing the complete sequence of meningococ- cal PorA VR1 P1.19. Specific anti-PorA antibodies were induced by the immunization of Balb/C mice with unconjugated and BSA-conjugated peptides. The elicited antibodies were able to react with the native PorA protein as presented in the meningococcal outer membrane vesicles. These results highlight the importance of presenting the VR1 to the immune system as close as possible to the natural conditions in order to obtain an adequate immune response.