Leishmania major infection in BALB/c mice: protection or exacerbation by treatment with different doses of BCG.

The effect of live bacillus Calmette-Guérin (BCG), administered intraperitoneally to BALB/c mice, upon the development of lesions induced by subcutaneous infection with Leishmania major was examined. Lesions in mice given 10(7) BCG colony-forming units (CFU) 9 days before challenge with L. major were less severe and contained significantly fewer parasites than those of similarly infected control mice not given BCG. This effect of treatment with high doses of BCG upon the development of leishmanial lesions was observed using L. major promastigotes and amastigotes, whether or not 10(6) live BCG was included in the parasite inoculum. Lesions in mice given 5 x 10(4) BCG CFU 14 days before infection with L. major contained significantly fewer parasites than those of control mice not given BCG. Mice treated with low doses of BCG and infected with an L. major inoculum also comprising BCG exhibited larger lesions that contained more parasites. Interestingly, compared to naive mice infected with L. major, infection of naive mice with L. major mixed with live BCG consistently led to the development of more severe lesions that contained higher numbers of parasites. No correlation was found between the effect of BCG on the development of lesions induced by L. major and the amounts of IFN gamma, IL5 and TNF produced after in vitro antigenic challenge of either draining lymph node or spleen cells, the antigenic challenge being either live BCG or live L. major.