Construction and assessment of the immunogenicity and bactericidal activity of fusion protein porin A from Neisseria meningitidis serogroups A and B admixed with OMV adjuvant as a novel vaccine candidate

Objective(s): The porins A and B and also outer membrane vesicles (OMVs) of Neisseria meningitidis are used for vaccine purposes. In the present study, we aimed to design a new vaccine candidate based on a fusion of PorA of serogroups A and B of N. meningitidis admixed with OMV and evaluate it in an animal model. Materials and Methods: After bioinformatic studies, a fusion protein composed of porin A from both serogroups A and B of N. meningitidis was constructed, expressed, and purified by nickel resins. Extraction of OMV of N. meningitidis was performed using a chemical method. The mice were vaccinated subcutaneously in different groups with mixtures of PorA proteins, OMV, and Freund’s adjuvants. Then, the immune responses were measured using the ELISA method. Finally, serum bactericidal activity (SBA) procedure was applied to assay the activity of the immune responses in mice. Results: Mice received the PorA protein plus Freund’s adjuvant. Mice vaccinated with PorA fusion of serogroups A+B plus Freund’s adjuvant produced more IgG, IgG1, and IgG2a than combinations admixed with OMV. Furthermore, the vaccinated mice tended to direct the IgG responses toward IgG1. Sera of the mice that received PorA+Freund’s and those that received PorA+OMV produced higher bactericidal activity than the controls. Conclusion: Fusion protein porin A could be a valuable target for developing vaccines against N. meningitidis. Although, Freund’s adjuvant induced the strongest IgG responses, given that Freund’s adjuvant has no human use, and OMV is a human adjuvant, OMV could be considered in vaccine design against N. meningitidis.