Further development of the baboon as a model for acute schistosomiasis.

Baboons develop a syndrome, including eosinophilia and transient fever, after infection with cercariae of Schistosoma mansoni that is consistent with the human syndrome of acute schistosomiasis. Radiotelemetry can be used to follow the course of fever in infected baboons. Individual variations in intensity of disease were noted in baboons. These symptoms and signs were more closely linked to the onset of oviposition by the newly matured worms than they were to the presence of migrating schistosomula or maturing worms. The baboon is concluded to be a suitable and useful model for human acute schistosomiasis mansoni.

Relative resistance of Brazil strain trypomastigote forms of Trypanosoma cruzi to in vitro antibody-dependent complement-mediated lysis.

Various assay conditions were employed in experiments examining the susceptibility of trypomastigote forms of the Brazil strain of Trypanosoma cruzi to antibody-dependent complement-mediated lysis. To identify optimal assay conditions, both guinea pig serum and normal human serum were used as complement sources, and fibroblast-derived or blood-form trypomastigotes were either coincubated with immune sera and complement together, or the parasites were first precoated with antibodies and then were incubated in complement. Under conditions promoting maximal lysis by antibodies and complement, 60-90% of the trypomastigote forms were not lysed. These results indicate that trypomastigotes of certain isolates of T. cruzi, such as the Brazil strain, may possess an escape mechanism by which they evade complement-mediated lysis.

Production and characterization of clones of the Brazil strain of Trypanosoma cruzi.

Six clones and 4 subclones were isolated from the Brazil strain of Trypanosoma cruzi and were passaged in C3H(He) mice. Parasitemia levels and survival times of mice infected with 8 of the isolates were equivalent to the Brazil strain in virulence. Two clones, designated WFTc-5.1 and WFTc-6.1 (WFTc = Wake Forest Trypanosoma cruzi) were of lower virulence in C3H mice than the other isolates and the Brazil strain. C57BL/6 mice infected with WFTc-5.1 had significantly lower parasitemias and higher survival rates than C57BL/6 mice infected with the Brazil strain or a clone designated WFTc-3.2. Levels of anti-T. cruzi IgM and IgG antibodies were the same in mice infected with higher virulence or lower virulence isolates. Based on these results the Brazil strain of T. cruzi is composed of distinct subpopulations which are heterogeneous with respect to virulence.