Background: Neisseria meningitidis serogroup A Polysaccharides vaccines have been available for many years, but these vaccines have many disadvantages due to their induction of T-Cell independent responses. To overcome these problems, many researches have been focused on other parts of bacterial cell component such as OMV (Outer membrane vesicle). In this study, OMV containing PorA were extracted and evaluated by biological and immunological methods.
Materials and methods: OMV were extracted by siadat, et al method. Physicochemical properties of extracted OMV were analyzed by electron microscopy and SDS-page. The toxicity of LPS content in OMV was assayed by LAL test. The Presence of PorA was confirmed by western blot. Antibodies synthesis after immunization by OMV was evaluated using ELISA method.
Results: The content of extracted protein was 0.1 mg/ml. Size of OMV was between 50 and 150 nanometer. SDS-PAGE showed that PorA was located in 35-40 kDa. LAL test showed that the endotoxin activity was ranged in 126EU/ml which is safe for using. The ELISA test showed that the total IgG titer was elevated after first injection.
 Conclusion: The results showed that the conformation of extracted OMV was stable, and there were no progeny determinants in OMV. Also, OMV elicited high level of specific antibodies against Neisseria meningitidis serogroup A. These results indicate that the OMV can be used as a meningococcal vaccine after further investigations.
 Keywords: Outer membrane vesicle (OMV), PorA, Neisseria meningitidis serogroup A.