Abstract
BackgroundLiHyV is an antigenic hypothetical protein present in both promastigote and amastigote stages of Leishmania infantum, which was recently identified by an immunoproteomic approach. A recombinant version of this protein (rLiHyV) was evaluated as a diagnostic marker for canine VL (CVL). In addition, the prophylactic efficacy of the rLiHyV protein, and two of its CD8+ T cell epitopes, has been analyzed in a murine model of visceral leishmaniasis (VL).MethodsInitially, the rLiHyV protein was evaluated by an ELISA technique for the serodiagnosis of CVL. Secondly, vaccines composed of the recombinant protein and both chemically synthesized peptides, combined with saponin as an adjuvant; were administered subcutaneously into BALB/c mice. The cellular and humoral responses generated by vaccination were evaluated. In addition, the parasite burden and immune response were studied 10 weeks after L. infantum infection.ResultsThe rLiHyV protein was recognized by antibodies of VL dogs. No cross-reactivity was obtained with sera from dogs vaccinated with a Brazilian commercial vaccine, with sera from animals infected with Trypanosoma cruzi, Babesia canis and Ehrlichia canis, or those from non-infected animals living in an endemic area for leishmaniasis. After challenge with L. infantum, spleen cells of BALB/c mice vaccinated with rLiHyV/saponin stimulated with parasite antigens showed a higher production of IFN-γ, IL-12 and GM-CSF, than the same cells obtained from mice vaccinated with the individual peptides, or mice from control (inoculated with saline or saponin) groups. This Th1-type cellular response observed in rLiHyV/saponin vaccinated mice was accompanied by the induction of parasite-specific IgG2a isotype antibodies. Animals immunized with rLiHyV/saponin showed significant reductions in the parasite burden in the liver, spleen, bone marrow and in the lymph nodes draining the paws relative to control mice.ConclusionsThe present study showed for the first time that the L. infantum LiHyV protein could be considered as a vaccine candidate against L. infantum infection, as well as a diagnostic marker for CVL.
Highlights
LiHyV is an antigenic hypothetical protein present in both promastigote and amastigote stages of Leishmania infantum, which was recently identified by an immunoproteomic approach
Serodiagnosis of canine visceral leishmaniasis (VL) (CVL) using the recombinant version of the LiHyV protein (rLiHyV) protein Serological tests are currently recommended for the laboratorial diagnosis of CVL
In Brazil, there are two commercial vaccines against CVL, Leishmune® [37] and Leish-Tec® [15] and, protective, they can induce seroconversion in the immunized animals, causing them to be classified as false-positive in the serological assays performed [9, 38]
Summary
LiHyV is an antigenic hypothetical protein present in both promastigote and amastigote stages of Leishmania infantum, which was recently identified by an immunoproteomic approach. The treatment of disease is based on the parenteral administration of pentavalent antimonials, increased parasite resistance and side effects observed in the patients have been important problems [3, 4] Other drugs, such as amphotericin B and its liposomal formulations, pentamidine and miltefosine are encouraging, their toxicity and/or high cost had limited their use [5, 6]. Canine visceral leishmaniasis (CVL) due to Leishmania infantum is a major global zoonosis, which is endemic in approximately 70 countries worldwide [7, 8]. It cannot only be considered as a veterinary disease, since infected dogs are the main domestic reservoirs of parasites for human disease [7]. The development of new strategies to diagnose leishmaniasis has become a priority
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