Avaliação da eficácia protetora induzida pela imunização de camundongos balb/c com a proteína recombinante enolase de Leishmania braziliensis contra a infecção causada pela espécie Leishmania infantum

Abstract

The leishmaniasis are a complex of parasitic diseases caused by protozoa of the genus Leishmania. Because it is a serious public health problem and still presents problems in the prevention and diagnosis methods, and treatment of the patients, the development of vaccines could be presented as an additional and effective measure for the control of the disease. A major challenge encountered in the development of vaccines for leishmaniasis is the low efficacy of antigens in protecting against different species of parasites, since they usually offer species-specific protection. Thus, in the present study, the enolase protein of Leishmania braziliensis was expressed and evaluated as a vaccine candidate against Leishmania infantum infection. The recombinant protein (rEnolase) was evaluated in combination with the saponin, and immunizations were performed on BALB/c mice. Three doses at 15 day intervals were administered and, 30 days after the last dose, half of the animals in the groups were euthanized for immunogenicity evaluations, and the other animals were infected with stationary-phase promastigotes of the parasites. The parasitological and immunological evaluations were performed after 10 weeks of infection. The results showed that the vaccine induced a Th1 immune response with elevated levels of IFN-γ, IL-12 and GM-CSF, and a production of nitric oxide by phagocytic cells, following the in vitro stimulation with rEnolase or using the soluble extract of the parasites, when an ELISA capture and flow cytometry were performed. The vaccinated animals, when compared to the control groups, showed a low parasite load in the liver, spleen, bone marrow and lymph nodes, through the limiting dilution and qPCR techniques. These animals also had low levels of Th2 cytokines, such as IL-4 and IL-10, and IgG1 isotype antibodies. Furthermore, the protection was associated with an IFN- production by CD4+ T cells. Thus, it is concluded that the recombinant enolase protein of L. braziliensis can offered heterologous protection against L. infantum and could well be considered as a vaccine candidate against visceral leishmaniasis.