Safety and immunogenicity of a defined vaccine for the prevention of cutaneous leishmaniasis

Healthy Colombian adult volunteers with no history of leishmaniasis were evaluated for evidence of previous subclinical infection with Leishmania based on the Montenegro skin test (MST). Twelve MST-positive subjects were enrolled in an open-label, uncontrolled clinical trial (the “MST-positive trial”) and received three injections of the LEISH-F1 + MPL-SE vaccine (consisting of 10 μg recombinant Leishmania polyprotein LEISH-F1 antigen [TSA + LmSTI1 + LeIF] + 25 μg MPL®-SE adjuvant). Sixty-eight MST-negative subjects were enrolled in a randomized, double-blind, controlled trial (the “MST-negative trial”) and were randomly assigned to receive three injections of either the vaccine (n = 34), 10 μg LEISH-F1 protein alone (n = 17), or saline placebo (n = 17). In both trials, the study injections were given subcutaneously on Days 0, 28, and 56, and subjects were followed for safety and immunological endpoints. The LEISH-F1 + MPL-SE vaccine was safe and well tolerated in MST-positive and MST-negative subjects. In both trials, an IFN-γ response to the LEISH-F1 antigen at Day 84 was observed in more than half of the vaccine recipients. In the MST-negative trial, the IFN-γ response was significantly more frequent and of greater magnitude in vaccine recipients than in protein-alone or placebo recipients. An IgG antibody response to LEISH-F1 was observed in all vaccine recipients. In both trials, delayed-type hypersensitivity (DTH) to LEISH-F1 was observed in most of the vaccine recipients. In the MST-negative trial, DTH was significantly higher in vaccine than placebo recipients. These clinical trials of the first defined vaccine for leishmaniasis show that the LEISH-F1 + MPL-SE vaccine is safe and immunogenic in healthy subjects with and without evidence of previous subclinical infection with Leishmania.