BIOCHEMICAL, IMMUNOLOGICAL, AND BIOLOGICAL CHARACTERIZATION OF TRYPANOSOMA-CRUZI POPULATIONS OF THE ANDEAN NORTH OF CHILE

Twenty-one Trypanosoma cruzi stocks isolated from Triatoma infestans a nd humans of the Chilean Andean highlands were studied at the genotypi c level by schizodeme and molecular karyotype analyses, which allowed a clear distinction of the parasites from those hosts. A phenotypical characterization was performed by proteolytic activity after electroph oretic fractionation without discrimination among the stocks. Metacycl ic trypomastigotes obtained in vitro proved to be infective to Swiss m ice and the study of immune response and biological behavior was asses sed. Of a total of 21 T. cruzi stocks, only 11 proved to be infective in mice due to difficulties in obtaining metacyclic trypomastigotes wi th the parasite populations isolated from humans. Western blot analysi s revealed a complex immune response even in the first days postinfect ion with each T. cruzi strain studied. Antigenic recognition by each i mmune serum is characteristic, although several major and common antig ens were detected. Lytic antibodies were studied by the in vitro compl ement-mediated lytic assay using purified metacyclic trypomastigotes a s target cells. All the T. cruzi isolates tested induced lytic antibod ies in this experimental model. Parasitemias were moderate and charact eristic for each T. cruzi strain. Results are compared with metacyclic forms of the infective and pathogenic Tulahuen strain. (C) 1995 Acade mic Press, Inc.