Immunogenicity in dogs and protection against visceral leishmaniasis induced by a 14 kDa Leishmania infantum recombinant polypeptide

In areas were human visceral leishmaniasis (VL) is endemic, the domestic dog is the main parasite reservoir in the infectious cycle of Leishmania infantum. Development of prophylactic strategies to lower the parasite burden in dogs would reduce sand fly transmission thus lowering the incidence of zoonotic VL. Here we demonstrate that vaccination of dogs with a recombinant 14 kDa polypeptide of L. infantum nuclear transport factor 2 (Li-ntf2) mixed with adjuvant BpMPLA-SE resulted in the production of specific anti-Li-ntf2 IgG antibodies as well as IFN-γ release by the animals’ peripheral blood mononuclear cells stimulated with the antigen. In addition, immunization with this single and small 14 kDa polypeptide resulted in protracted progression of the infection of the animals after challenging with a high dose of virulent L. infantum. Five months after challenge the parasite load was lower in the bone marrow of immunized dogs compared to non-immunized animals. The antibody response to K39, a marker of active VL, at ten months after challenge was strong and significantly higher in the control dogs than in vaccinated animals. At the study termination vaccinated animals showed significantly more liver granulomas and lymphoid hyperplasia than non-vaccinated animals, which are both histological markers of resistance to infection. Together, these results indicate that the 14 kDa polypeptide is an attractive protective molecule that can be easily incorporated in a leishmanial polyprotein vaccine candidate to augment/complement the overall protective efficacy of the final product.