Comparison of Adjuvant Effects of Montanide ISA-720 and Heat Shock Protein 27 in Increasing Immunostimulatory Properties of HIV-1 Nef-Vif Fusion Protein Construct.

Introduction: Effective T-cell-mediated immunity has emerged as an essential component of human immunodeficiency virus-1 (HIV-1) vaccination. Thus, inducing an immune response against HIV proteins such as Nef and Vif, two major accessory proteins with critical roles in HIV pathogenesis and immune evasion, may lead to an effective approach.

Aim: Our goal is to evaluate and compare Montanide ISA-720 and heat shock protein 27 in increasing immunostimulatory properties of HIV-1 Nef-Vif fusion protein as a vaccine candidate.

Methods: In this study, the fusion gene with and without the gene was cloned in the prokaryotic pET24a (+) vector. Then, the recombinant Nef-Vif and Hsp27-Nef- Vif proteins were generated in the E. coli system. Finally, their immunostimulatory properties were evaluated in mice. Indeed, the potency of Hsp27 as an endogenous natural adjuvant was investigated to enhance HIV-1 Nef-Vif antigen-specific immunity compared to Montanide ISA-720 as a commercial adjuvant in protein-based immunization strategy.

Results: Our results approved the role of Hsp27 as an effective adjuvant in the stimulation of B- and T-cell immunity. The linkage of Hsp27 to antigen could elicit higher levels of IgG1, IgG2a, IFN-γ, IL- 5 and Granzyme B than antigen mixed with Montanide ISA-720. Moreover, the ratios of IFN-γ/IL-5 and IgG2a/IgG1 were significantly increased in groups receiving Nef-Vif protein + Montanide ISA- 720 and Hsp27-Nef-Vif protein indicating the direction of the immune response pathway toward strong Th1 response. These ratios were higher in the group receiving Hsp27-Nef-Vif protein than in the group receiving Nef-Vif protein + Montanide ISA-720.

Conclusion: Our findings suggest that Hsp27 can be used as an effective adjuvant to enhance antigenspecific immune responses in HIV-1 infectious models for therapeutic vaccine development.