title: Variants with reduced virulence derived from Leishmania major after mutagen treatment.
abstract: After several in vitro treatments of a virulent population of Leishmania major with the mutagen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), five clones (vir-) were obtained that did not produce cutaneous lesions after subcutaneous injection of 10(6) promastigotes. All the control clones (vir+) obtained from the non-mutagenized parasite population produced progressive cutaneous lesions with as few as 10(3) parasites. Late lesions were observed occasionally after injection of 10(7) vir- parasites. These late lesions appeared to result from the selection of virulent revertants, since parasites isolated from these lesions produced progressive lesions in BALB/c mice almost as readily as the control parasites. Two vir- clones, one vir+ clone and one revertant clone were examined for survival in BALB/c macrophages in vitro. All clones were taken up by the macrophages and transformed into amastigotes. However, vir- clones failed to multiply inside the macrophages. A vir- clone was found to protect mice against a subsequent challenge with vir+ parasites.
mesh_terms: D000371:Agglutination; D000818:Animals; D007895:Leishmania tropica / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D007896:Leishmaniasis / Q000469:parasitology; D008264:Macrophages / Q000469:parasitology; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D014774:Virulence
chemical_list: D008769:Methylnitronitrosoguanidine