Shahid Beheshti University of Medical Sciences, Iran
Arfa Moshiri is Research and Teaching Assistant at Pasteur Institute of Iran. Experience in Research And Teaching Assistant. He also lived in Pasteur Institute of Iran, Pasteur institute of Iran
Objective: The outer membrane vesicle of Neisseria meningitidis serogroup B (OMV) is among the more studied components with microbial origin, which could be applied as an adjuvant. In the present study, OMV of N. meningitidis serogroup B was applied as an adjuvant co-administrated with the HBs Ag to evaluate the efficiency of this immunization strategy for the promotion of efficient humoral/cellular responses against Hepatitis B virus.
Methods: OMVs were prepared as previously described (Siadat et al., 2005). In brief, N. meningitidis serogroup B strain (CSBPI, G-245) was grown under controlled submerge cultural condition in a fermentor containing modified Frantz medium. The outer membrane vesicles (OMVs) were extracted in Tris-HCl buffer, containing EDTA and deoxycholate. Purification of the OMVs was done by sequential centrifugation at 20,000 followed by ultracentrifugation at 125,000. Purified recombinant Hepatitis B surface antigen (HBsAg) was prepared from the production and research complex of Pasteur Institute of Iran (Karaj ,Iran). Four animal groups were immunized by intranasal inoculation with HBs, HBs+OMV mixture, HBs+complete/incomplete Freund's adjuvant (C/IFA) and OMV. Two booster immunizations carried out three and six weeks after the first immunization. Indirect enzyme-linked immunosorbent assay (ELISA) was applied to assess total and subtype antibody responses against HBsAg.
Results & Conclusion: Analysis of anti-HBsAg responses elicited in immunized BALB/c mice following different immunization regimens indicated OMV+HBsAg as an immunopotent combination which significantly induced anti-HBsAg IgG with IgG2a dominancy. In accordance to previous study, evaluation of humoral responses following the immunization with HBsAg, HBsAg+C/IFA and HBsAg+OMV indicated the potency of HBsAg vaccine in all the administrated formulations to efficiently induce humoral responses against HBsAg. Although the highest level of antibodies was raised in HBsAg +C/IFA injected animals, however, the promoted response in HBsAg +OMV immunized group was comparable with HBsAg +C/IFA, indicating the capability of HBsAg +OMV immunogen for humoral response induction. All of these responses are TH1 oriented with IgG2a sub-type predominance. The highest IgG2a titer has been detected in the sera of mice immunized with HBsAg +C/IFA respectively followed by HBsAg +OMV and HBsAg. Although the most augmented anti-HBs humoral responses were detected in the sera of HBsAg +C/IFA-immunized mice, however, titer of total anti-HBs antibody and raised IgG2a was significantly increased by the application of OMV adjuvant and was comparable with the HBsAg +C/IFA regimen. Considering that OMV is a human-compatible adjuvant, this finding argues in support of probable application of OMV in HBsAg -based vaccine. According to our study, HBsAg combined with OMV seem to be a promising adjuvant in vaccine development against Hepatitis B virus.