Hepatitis B core virus-like particles bearing Pgp3 antigen enhance immune response against genital chlamydial infection in mice.

Chlamydia trachomatis Pgp3 protein-induced immunoprotection is effective but incomplete, which requires the suitable adjuvants to enhance its immune response. Within this context, Hepatitis B core virus-like particles (HBc-VLP) emerge as nanoscale protein particles capable of incorporating either endogenous or exogenous antigens or epitopes. In this study, HBc-Pgp3 chimeric protein was accomplished by integrating the identified dominant epitope of the Pgp3 protein into the major immunodominant region of a truncated HBc-VLP, which was realized in the pET28a (+) vector and expressed via the E. coli BL21 expression system. The efficacious expression and purification of the recombinant HBc-Pgp3 facilitated a tripartite immunization regimen in mice. The immunological assessment encompassed the measurement of IgG antibody and cytokine levels through ELISA, alongside flow cytometric analysis of the CD4+ Th1 cell-mediated immune responses within the murine spleen. Comparative analysis revealed that the HBc-Pgp3-vaccinated mice demonstrated superior IgG antibody titers and subtypes relative to the controls. Moreover, the HBc-Pgp3 formulation was instrumental in augmenting IFN-γ production, enhancing the efficiency of Chlamydia muridarum clearance post-challenge, and severity of hydrosalpinx within the lower genital tract. Collectively, these findings illuminate the potential of the novel HBc-Pgp3 chimeric construct as an innovative vaccine candidate, offering augmented immunoprotection against chlamydial infection.