Outer membrane vesicle ofNeisseria meningitidis serogroup B as an adjuvant to induce specific antibody response against the lipopolysaccharide ofBrucella abortus S99

Brucellosis is a worldwide zoonosis and represents one of the most important public health problems in many countries, especially around the Mediterranean basin, Middle East, India and Central and South America. Currently subunit vaccines are being considered to develop effective vaccines for human which has been evidenced by vaccines currently available against the infections such as meningococcal diseases and influenza. The application of new adjuvants of microbial origins is also underway to design subunit vaccines promoting the immune responses to the antigenic determinant(s) of the vaccine. In order to explore the efficacy of Brucella abortus lipopolysaccharide (LPS) combined with different adjuvants and proteins (as a vaccine candidate) in the induction of immune response as an effective and long-lasting immunity against Brucella , we evaluated the outer membrane vesicle of Neisseria meningitidis serogroup B (GBMOMV) as a subcutaneous adjuvant and a part of a brucellosis candidate vaccine to induce high titres of specific anti- Brucella abortus S99 LPS in animal model (mice). The obtained results were compared with complete and incomplete Freund’s adjuvants (CFA and IFA). LPS+GBMOMV was the most immunogenic compound that stimulated following the first injection and increase in IgG titre of about 3.90, 3.18 and 1.58 fold higher than that produced against LPS, LPS+IFA and LPS+CFA, respectively. The highest anti-LPS IgG titre was detected two weeks after the third injection (the day 42) of LPS+GBMOMV. Purified GBMOMV can be considered as a safe subcutaneous adjuvant and a part of a candidate vaccine when combined with lipopolysaccharide of Brucella abortus S99.