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Background: The development of a vaccine for the prevention of visceral leishmaniasis (VL) still represents a significant unmet medical need. A human vaccine can be found if one takes into consideration that many people living in endemic areas of disease are infected but do not develop active VL, including those subjects with subclinical or asymptomatic infection. Methods: In this study, a phage display was used to select phage-exposed peptides that were specific to immunoglobulin G (IgG) antibodies from asymptomatic and symptomatic VL patients, separating them from non-infected subjects. Phage clones presenting valid peptide sequences were selected and used as stimuli of peripheral blood mononuclear cells (PBMCs) obtained from both patients' groups and controls. Those with higher interferon-gamma (IFN-γ)/interleukin (IL)-10 ratios were further selected for vaccination tests. Results: Among 17 evaluated clones, two were selected, B1 and D11, and used to immunize BALB/c mice in an attempt to further validate their in vivo protective efficacy against Leishmania infantum infection. Both clones induced partial protection against the parasite challenge, which was evidenced by the reduction of parasitism in the evaluated organs, a process mediated by a specific T helper (Th)1 immune response. Conclusions: To the best of our knowledge, this study is the first to use a rational strategy based on in vitro stimulation of human PBMCs with selected phage-displayed clones to obtain new immunogens against VL. [ABSTRACT FROM AUTHOR]

In the present study, Leishmania braziliensis enolase was cloned and the recombinant protein (rEnolase) was evaluated for the serodiagnosis of canine and human visceral leishmaniosis (VL). For the canine VL diagnosis, this study examined serum samples of Leishmania infantum -infected dogs, from non-infected animals living in endemic or non-endemic areas of leishmaniosis, as well as those from Leish-Tec ® -vaccinated dogs and Trypanosoma cruzi or Ehrlichia canis experimentally infected animals. For the human VL diagnosis, this study analyzed serum samples from VL patients, from non-infected subjects living in endemic or non-endemic areas of leishmaniosis, as well as those from T. cruzi -infected patients. In the results, an indirect ELISA method using rEnolase showed diagnostic sensitivity and specificity values of 100% and 98.57%, respectively, for canine VL serodiagnosis, and of 100% and 97.87%, respectively, for human VL diagnosis. These results showed rEnolase with an improved diagnostic performance when compared to the recombinant A2 protein, the crude soluble Leishmania antigenic preparation, and the recombinant K39-based immunochromatographic test. In conclusion, preliminary results suggest that the detection of antibodies against rEnolase improves the serodiagnosis of human and canine visceral leishmaniosis. [ABSTRACT FROM AUTHOR]