Background: There have been great efforts in vaccine design against HIV-1 since 1981. Various approaches have been investigated, including optimized delivery systems and effective adjuvants to enhance the efficacy of selective antigen targets. In this study, we evaluated the efficiency of IMT-P8 and LDP12 cell penetrating peptides in eliciting immune responses against HIV-1 Nef-MPER-V3 fusion protein as an antigen candidate. Moreover, the potency of HP91 and HSP27 was compared as an adjuvant in female BALB/c mice through different regimens.
Methods: For this purpose, the recombinant Nef-MPER-V3, IMT-P8-Nef-MPER-V3 and LDP-Nef- MPER-V3 proteins were generated on a large scale. After mice immunization with different regimens, the secretion of antibodies, cytokines and granzyme B was evaluated by ELISA.
Results: Our results demonstrated that immunized mice receiving the Nef-MPER-V3 linked to IMT-P8 exhibited significantly higher levels of IgG compared to other groups. The IMT-P8-Nef- MPER-V3 with the Hp91 group showed the highest level of humoral response, which was significantly stronger than the LDP12 formulation using the same antigen (LDP-Nef-MPER-V3). Additionally, the combination of IMT-P8-Nef-MPER-V3 with either Hp91 or Hsp27 resulted in robust induction of IFN-γ compared to the LDP-Nef-MPER-V3 group. Furthermore, cytotoxic T lymphocyte (CTL) activation and proliferation assays indicated that IMT-P8 served as a more effective CPP, particularly when used in conjunction with the Hp91 adjuvant Conclusion: Altogether, the data indicated that Nef-MPER-V3 antigen in different formulations was effective in eliciting immune responses. This fusion protein has the high potency to induce both immunity arms, specifically when incorporated with IMT-P8, which showed priority to LDP12. Moreover, HP91 resulted in a greater humoral and cellular immune activation compared to HSP27. These findings suggest the potential of IMT-P8 as a superior delivery system for enhancing immune responses in vaccine development.