Avaliação da proteína fator eucarioto de alongamento 1 beta de Leishmania (EF1β) como candidata para uso no diagnóstico e vacina contra as leishmanioses

Abstract

Leishmaniasis are neglected tropical diseases caused by protozoan parasites of the genus Leishmania. Controlling this complex of diseases is crucial for reducing cases in humans and dogs, which are considered the main urban reservoirs of the Leishmania parasite. Diagnostic methods are based on parasitological and immunological tests, which have variable sensitivity for detecting cases with low parasite load, in addition to variable specificity, since cross-reactions with diseases caused by other trypanosomatids are present. Growing limitations in available chemotherapy strategies and the absence of an effective vaccine deepen the difficulty in controlling leishmaniasis. Therefore, new studies that seek to identify more sensitive and specific antigens for potential use as a diagnosis and prophylactic agent are extremely important. Thus, in the present work, the protein called Leishmania elongation factor 1 beta (EF1β) was selected through immunoproteomic assay performed in Leishmania infantum protein extracts, and it was produced as recombinant antigen and tested in ELISA experiments for the serological diagnosis of canine and human visceral leishmaniasis. Due to the high similarity in the protein amino acid sequence in the Leishmania genus, assays were also performed for the diagnosis of human tegumentary leishmaniasis. The rEF1β protein showed 100% sensitivity and specificity, being able to identify patients with visceral and tegumentary leishmaniasis, as well as symptomatic and asymptomatic dogs, with no significant cross-reactivity withother serum classes. The recombinant protein also showed excellent results as a serological marker for the follow-up of patients after treatment and cure of disease. As a vaccine candidate, the antigen was administered as DNA vaccine or recombinant protein plus saponin as adjuvant in BALB/c mice, and immunized animals developed a Th1 type immune response, characterized by high levels of IFN-γ, IL-12, GM-CSF, and IgG2a subtype antibodies, before infection, which was maintained after challenge and corroborated with significant reductions in the parasite load in the liver, spleen, bone marrow and lymph nodes of the immunized animals, when compared to data obtained in the control groups. The vaccination using rEF1β plus saponin induced a more robust Th1 response and better parasitological protection, when compared to the DNA vaccine. In conclusion, results suggest that EF1β can be considered as a promising agent for diagnosis and/or as a vaccine candidate against leishmaniasis.