Immunogenicity and safety of autoclaved Leishmania major plus BCG vaccine in healthy Sudanese volunteers.

In a longitudinal study in the epidemiology of Leishmania donovani infection in an endemic focus in eastern Sudan, we observed that previous exposure or infection with Leishmania major appeared to protect against visceral leishmaniasis caused by L. donovani. We therefore conducted a study to test the safety and immunogenicity of a vaccine consisting of autoclaved L. major (ALM) plus BCG in inducing protection in vaccinated individuals. Leishmanin-negative healthy Sudanese volunteers were enrolled in the study and were divided into three groups: group (A) received ALM+BCG, group (B) received BCG alone, and group (C) received the vaccine diluent. The subjects were examined for their clinical and immunological responses before intervention, following intervention and 6-8 weeks after vaccination. Vaccinated subjects (group A) developed localized reactions at the sites of vaccine inoculation that ulcerated and healed within 4-6 weeks; 61.6% of them converted to leishmanin reactive following vaccination. Only one subject in group (C) became leishmanin-positive. A total 76.9% of the vaccinated volunteers in group (A) produced significant levels of interferon-gamma in response to L. major antigen. The vaccine produced significant cellular immune responses that may protect against natural challenge. None of the groups had systemic reactions and all the reactions observed in the vaccinated group were comparable with the BCG-vaccinated group.