Avaliação clínica, parasitológica e da resposta imunológica induzida em cães pela vacinação com o antígeno A2 contra a infecção experimental por Leishmania (Leishmania) chagasi

Abstract

Leishmaniasis is an infectious disease with an overall prevalence of 12 million cases and 350 million people at risk of infection. Leishmania parasites are transmitted through the bite of an infected sand fly to vertebrate hosts, leading to a spectrum of clinical manifestations, including visceral leishmaniasis. Leishmania (Leishmania) infantum and L. (L.) chagasi, which are now considered synonymous species, and L. (L.) donovani are the major etiologic agents of visceral leishmaniasis (VL), a fatal infection if diagnosis and treatment are not promptly established. Dogs are highly susceptible to infection and considered the major reservoir for L. (L.) infantum and L. (L.) chagasi, in different geographical regions of the globe. Research has recently revealed much new information, but advances in treatment and control have been disappointing. Treatment of infected dogs is of limited effectiveness and not recommended in endemic regions, since dogs that respond to treatment may still be a source of parasites. In this study, we investigated in dogs the immunogenicity and protective immunity against L. (L.) chagasi infection induced by vaccination with a formulation containing the recombinant A2 protein, an amastigote specific antigen, and saponin. Vaccinated animals produced significantly increased levels of total IgG and IgG2, but not IgG1 anti-A2 antibodies, and remained negative in conventional leishmaniasis serodiagnostic methods. Significantly increased IFN- and low IL-10 levels were detected in vaccinated animals before and after challenge, as compared to control animals. In the group of infected dogs, only 28.5% of dogs remained asymptomatic, with clinical symptoms were found in other weight loss, intense, and profuse bloody diarrhea, cachexia, hepatosplenomegaly, onychogryphosis, lesions of skin and eye purulent secretion. These symptoms appear early in the dogs in the control group. Finally, vaccination with rA2 did not convert serological tests using promatigote antigens, allowing for discrimination between vaccinated and infected animals, an important requirement for a public campaign control of CVL.