Immunization of susceptible BALB/c mice against Leishmania braziliensis. II. Use of temperature-sensitive avirulent clones of parasite for vaccination purposes.

Avirulent clones of Leishmania braziliensis were produced by treatment of parental parasite stock with the mutagen N-methyl-N'-methyl-N'-nitro-N-nitrosoguanidine and selection for growth at 19 degrees C. These clones have a clear preference for infection and growth in vitro at 19 degrees C rather than the normal 28 degrees C. In addition, they can be used to vaccinate naive mice successfully against growth of the parental parasite clones. Immunity can be adoptively transferred from vaccinated mice by Lyt-1+ cells from immunized animals.