Studies of Trypanosoma cruzi clones in inbred mice. I. A comparison of the course of infection of C3H/HEN- mice with two clones isolated from a common source.

Two single-cell-isolate cloned stocks of the Sylvio-X10 strain, recovered from an acute human Trypanosoma cruzi infection, were used to infect C3H/HEN mice. The Sylvio-X10/4 clone produced a chronic infection in mice; clone Sylvio-X10/7 produced an acute lethal infection under identical experimental conditions. The course of infection of mice with the Sylvio-X10/7 clone was characterized by higher peripheral blood parasitemia and greater tissue involvement, an earlier appearance of specific anti-T. cruzi plasma IgG and shorter survival times than in mice infected with the Sylvio-X10/4 clone. The course of infection in mice with the Sylvio-X10 strain was intermediate between that of the two clones. This is the first demonstration of the pluripotential pathogenetic nature of a T. cruzi strain due to genetic heterogeneity of the population of parasites that constitute the strain. This experimental system is highly stable and reproducible. Consequently, the use of inbred mice and T. cruzi clones appears to provide an excellent model to study factors which influence the course of Chagas' disease.