Caracterização das proteínas PvETRAMP 4 e PvETRAMP 11.2 como candidatos vacinais para malária vivax

Abstract

Malaria is the deadliest parasitic disease in the world, caused by protozoa of the Plasmodium genus and transmitted by mosquitoes of the Anopheles genus. In Brazil, P. vivax is the predominant species, mainly concentrated in the Northern region, where it has a significant impact on public health. Despite the different strategies used to control the disease, the World Health Organization recognizes the need for vaccine development as a complement to existing measures. Based on studies by our research group, a new protective mechanism was characterized that considers the protective role of cytotoxic CD8+ T lymphocytes in P. vivax infection, in addition to the identification of peptides presented by MHC class I. Among the identified antigens, the proteins PvETRAMP 4 and PvETRAMP 11.2 were selected for the present work. In the present work, both proteins were produced in a heterologous expression system in E. coli and purified by affinity chromatography. Next, C57BL/6 mice were immunized to assess the immunogenicity of the target antigens, by evaluating the antibody profile induced as well as the effector cellular response. Flow cytometry was used for immunophenotyping of CD4+ and CD8+ T lymphocyte populations. Finally, the animals were challenged with P. yoelii to evaluate the protective capacity of the tested antigens. The results obtained throughout the project reinforce the in vivo immunogenic capacity of the antigens in C57BL/6 mice, with a prominent TNF and IFN-γ response—cytokines classically associated with malaria protection—by CD4+ T cells, and a significant IFN-γ response by CD8+ T cells. Additionally, the proteins were able to induce a robust antibody response, the role of which should be further explored in future studies. Interestingly, upon heterologous challenge in a murine model infected with P. yoelii 17XNL, only the PvETRAMP 4 protein demonstrated the ability to control parasitemia, with a reduction in blood parasite load from the seventeenth day of infection. Despite the promising findings, the protection studies indicate that further efforts employing transgenic parasites expressing the proteins of interest are necessary to confirm the efficacy of these antigens as vaccine candidates.