Preliminary study of a Mycobacterium leprae bacterin vaccine in a human volunteer population in a nonendemic area

Seventeen volunteers who had never resided in areas with significant transmission of leprosy (Hansen's disease) were inoculated intradermally with 1.5 X 10(8) killed, purified armadillo-derived Mycobacterium leprae in a standardized preparation being tested for possible vaccine use. The peak of local skin responses, consisting of induration with or without ulceration similar to the post-lepromin Mitsuda reaction, occurred between the 21st and 28th days after injection. The maximum mean induration diameter was 17.2 mm, the minimum, 6.1 mm. Sera tested with the ELISA technique revealed no humoral response to either the sonicated bacilli, M. leprae-specific phenolic glycolipid I antigen, or three semi-synthetic analogues reactive with lepromatous patients' sera. The dose of M. leprae inoculated appeared to be safe and without unacceptable reactions at the injection site. One volunteer developed a generalized skin rash parallel to the local reaction, but the relationship of the former to the inoculation was unclear.