Phase I and II clinical trial comparing the LBSap, Leishmune®, and Leish-Tec® vaccines against canine visceral leishmaniasis.

Abstract

In this study, we performed a phase I and II clinical trial in dogs to evaluate the toxicity and immunogenicity of LBSap-vaccine prototype, in comparison to Leishmune® and Leish-Tec® vaccines. Twenty-eight dogs were classified in four groups: (i) control group received 1 mL of sterile 0.9% saline solution; (ii) LBSap group received 600 µg of Leishmania braziliensis promastigotes protein and 1 mg of saponin adjuvant; (iii) Leishmune®; and (iv) Leish-Tec®. The safety and toxicity of the vaccines were measured before and after three immunizations by clinical, biochemical, and hematological parameters. The clinical examinations revealed that some dogs of LBSap and Leishmune® groups presented changes at the site of vaccination inoculum, such as nodules, mild edema, and local pain, which were transient and disappeared seventy-two hours after vaccination, but these results indicate that adverse changes caused by the immunizations are tolerable. The immunogenicity results demonstrate an increase of B lymphocytes CD21+ regarding the Leishmune® group and monocytes CD14+ concerning LBSap and Leishmune® groups. In the in vitro analyses, an increase in lymphoproliferative activity in LBSap and Leishmune® groups was observed, with an increase of antigen-specific CD4+ and CD8+ T lymphocytes in the LBSap group. A second approach of in vitro assays aimed at evaluating the percentage of antigen-specific CD4+ and CD8+ T lymphocytes producers of IFN-γ and IL-4, where an increase in both IFN-γ producing subpopulations in the LBSap group was observed, also showed an increase in IFN-γ producers in CD8+ lymphocytes in the Leish-Tec® group. Our data regarding immunogenicity indicate that the vaccination process, especially with the LBSap vaccine, generated a protective immune response compatible with L. infantum parasite control. Based on the foregoing, the LBSap vaccine would be suitable for further studies of phase III clinical trial in endemic areas with high prevalence and incidence of canine visceral leishmaniasis (VL) cases.