Avaliação de protocolos vacinais baseados em formulacões de mRNA para o desenvolvimento de uma vacina contra leishmaniose

Abstract

Leishmaniasis is a neglected tropical disease of global distribution, still affecting around 700,000 to 1 million people per year. Prevention and control options are limited, and no vaccines are approved for human use. In this context, messenger RNA (mRNA)-based vaccines emerge as a promising approach, as they predominantly induce a Th1 response, which is essential for controlling intracellular parasites such as Leishmania. Previous studies have shown that the recombinant protein LinKAP, in association with the adjuvant Poly ICLC (Hiltonol®), induced an immune response with IFN-γ production and conferred partial protection in mice infected with L. infantum. In the present study, we developed an mRNA vaccine encoding the LinKAP antigen and compared its immunogenicity and protective efficacy with the recombinant protein-based vaccine against infection by L. amazonensis and L. infantum. Homologous regimens of three doses of mRNA or protein, as well as heterologous regimens of two or three doses combining mRNA and protein, were tested. LinKAP-encoding mRNAs were transcribed in vitro, and protein expression was validated by Western blot and immunofluorescence. Subsequently, the mRNAs were encapsulated in lipid nanoparticles (LNPs), and their physicochemical characteristics were evaluated, confirming their suitability for mouse immunization. In C57BL/6 mice, the homologous mRNA regimen induced a predominance of IgG2c, whereas the protein induced IgG1. Both protein and mRNA induced IFN-γ production, but neither formulation conferred protection against L. amazonensis infection. Heterologous regimens elicited similar levels of total IgG, with increased IgG1 and IFN-γ proportional to protein doses, partially protecting against L. amazonensis. In the homologous regimen in BALB/c mice, only recombinant LinKAP protein induced both humoral and cellular responses, with a balanced profile of inflammatory and regulatory cytokines, and was also the only formulation able to partially protect against L. infantum. In conclusion, the mRNA vaccine proved promising in inducing humoral responses, but the recombinant protein was more effective in inducing Th1 responses and protection. These data highlight the impact of the vaccine platform and antigen presentation on the immune profile, reinforcing the need to optimize the mRNA formulation and the animal model used.