Cross-reactivity evaluation of Neisseria meningitidis serogroups A and B outer membrane vesicles as a method to induce cross-immunity against both serogroups

Abstract number: P2014

Sharifat Salmani A., Siadat S.D., Aghasadeghi M.R., Parivar K., Sadat S.M., Amini S., Razavi M.

Objective: Outer membrane vesicle (OMV) of Neisseria meningitidis is an immunogenic structure and would promote specific and long-lasting serologic responses against the organism. All the serogroups of N. meningitidis poses this outer membrane structure which is released from the cell surface during growth of the organism.

Method: OMV of N. meningitidis serogroups A and B purified through Classen method. Serogroup B OMV injected intramuscularly to animal model (rabbit). Booster doses injected 2 and 4 weeks after the first immunization. Serum samples of immunized animals collected two weeks after any injection. Two different ELISA kits designed with serogroup A and B OMV as the solid phase antigen to assay total IgG titer against Serogroup A and B OMV. Optimized concentration of OMV determined by checkerboard and coated. The probable cross-reactivity between these two antigens was evaluated by measurement of anti-serogroup A OMV IgG in the animals immunized by the serogroup B OMV.

Results: OMV of N. meningitidis serogroup B elicited high titer of specific antibody. The produced antibody against serogroup B OMV was highly cross-reactive with serogroup A OMV. The elicited titer against Serogroup A OMV was close to the titer of anti-serogroup B OMV.

Conclusion: OMV of N. meningitidis serogroup B has efficiently promoted the synthesis of anti-OMV IgM and IgG.Sera of immunized animals with serogroup B OMV reacted with serogroup A OMV and high titers of anti-serogroup A OMV detected in the sera of serogroup B OMV-immunized animals. The detected titer of anti-serogroup A OMV in the sera of animals immunized against serogroup B OMV reveals the cross-reactivity between OMV of A and B serogroups. Since OMV consists of different outer membrane proteins, anti-OMV antibodies may be protective against Meningococci. The protective antigen of available vaccine for Meningococcal meningitis is a capsular polysaccharide. Immune responses against polysaccharides mostly lacks memory, isotype switching and affinity maturation of antibodies that may leads to weak opsinization of the microorganism and increase of microorganism chance to survive. Opsonophagocytic activity of anti-OMV antibodies would be studied to determine the cytolytic activity of these antibodies and the probability of the OMV application as the protective antigen in a new meningococcal meningitis candidate vaccine to overcome drawbacks of the available vaccine and induce cross-immunity against both of serogroups A and B.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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