The molecular characterization and immune protection of adhesion protein 65 (AP65) of Trichomonas vaginalis.

Abstract Background Adherence to the surface of the host cell is the precondition for T. vaginalis parasitism and pathogenicity, causing urogenital infection. The AP65 of T. vaginalis (TvAP65) involves in the process of adhesion. So, the present study was aimed at investigating the molecular characterization and vaccine candidacy of TvAP65 for protecting the host from the onset of Trichomoniasis. Methods The open reading frame (ORF) of TvAP65 was amplified and then inserted into pET-32a (+) to clone recombinant TvAP65 (rTvAP65). The immunoblotting determined the immunogenicity and molecular size of TvAP65, while immunofluorescence staining visualized and the precise localization of TvAP65 in T. vaginalis trophozoites. Animal challenge and enzyme-linked immunosorbent assay (ELISA) test were used to evaluate the immunoprotection and the types of the immune response of TvAP65. Results By the sequence analysis, TvAP65 encoded a 63.13 kDa protein that consisted 567 amino acid residues with a high antigenic index. The western blotting revealed that rTvAP65 and native TvAP65 could interact with the antibodies in the rat serums post hoc rTvAP65 immunization and the serums from the mice that were experimentally infected with T. vaginalis, respectively. Immunofluorescence stained TvAP65 on the surface of T. vaginalis trophozoites. Moreover, following emulsification with Freund's adjuvant, rTvAP65 was subsequently administered to BALB/c mice three times at 0, 2, and 4 weeks and the results from this animal challenge experiments showed significant increases in immunoglobulins of IgG2a, IgG1, and IgG, and cytokine of IFN-γ, and IL-2, and 10. Lastly, rTvAP65 vaccinated animals had a prolonged survival time (26.80 ± 4.05) after challenged by T. vaginalis. Conclusions TvAP65 mediated the adhesion of T. vaginalis to the host epithelia for the pathogenesis of the parasite and can be considered as a candidate protein for designing a functional vaccine that induces cell-mediated and humoral immunity against the T. vaginalis infection.