Abstract

Neisseria meningitidis serogroup B outer membrane vesicle (OMV) was revealed to be an efficient carrier for polysaccharide antigens such as capsular antigens. Also, OMV of N. meningitidis was shown to be able to induce high levels of antibodies when applied as an adjuvant for T-independent antigens. In this study OMV was used as an adjuvant with group A meningococcal capsular polysaccharide (GAMP) and tested in New zealand white rabbits to evaluate bactericidal antibody response and opsonophagocytosis activity against serogroup A meningococci. Non-covalent combination of OMV and GAMP and three controls including GAMP, OMV and normal saline were injected intramuscularly into groups of four female New Zealand rabbits with boosters on days 14 and 28 after primary immunization. The serum samples were collected on days 0, 14, 28 and 42 and tested by complement mediated bactericidal assay and opsonophagocytosis activity against serogroup A meningococci according to the world health organization protocol. The results indicate that the combination of OMV with GAMP, in noncovalent form, would be able to induce a high level of bactericidal antibody and opsonophagocytosis activity response in comparison with GAMP alone after 42 days (P< 0.05).  The OMV of N. meningitidis showed to be a potent carrier protein in the induction of immune system but in this article the role of OMV is studied as an adjuvant to promote immune system in non-covalent form and without any conjugation process in order to induce immune response against three prevalent serogroups of N. meningitidis.

Key words: OMV, Adjuvant, Neisseria meningitidis serogroup A, Bactericidal activity.