Establishment of clones of Trypanosoma cruzi and their characterization in vitro and in vivo.

An efficient technique for isolating clones of Trypanosoma cruzi from cultures and from animals has been developed. It is based on the inoculation of one organism, obtained by serial dilutions of cultured epimastigotes or isolated blood stream trypomastigotes, into enriched NNN medium (NNN-F:93). The cloning efficiency (percentage of positive cultures over the number inoculated) was 70% for cultured epimastigotes and 30-40% for blood-stream trypomastigotes. In vitro cultural characteristics of 14 secondary clones of an avirulent strain indicated that 12 clones grew in the F-94 medium primarily as epimastigotes at 27 degrees C and exclusively as amastigotes at 37 degrees C; 2 clones grew in F-94 medium primarily as amastigotes regardless of incubation temperature (27 degrees C or 37 degrees C). In vivo characterization of 7 clones from 2 virulent strains indicated that the virulence of individual clones was low immediately after isolation in NNN-F:93 medium, but the virulence of some clones returned to the level of the parent strain after more than 8 serial passages in CD-1 mice.