Clonal structure of Trypanosoma cruzi Colombian strain (biodeme Type III): biological, isoenzymic and histopathological analysis of seven isolated clones Estrutura clonal da cepa Colombiana do Trypanosoma cruzi (Biodema Tipo III): análise biológica, isoenzimática e histopatológica de sete clones isolados

The clonal structure of the Colombian strain of Trypanosoma cruzi, biodeme Type III and zymodeme 1, was analyzed in order to characterize its populations and to establish its homogeneity or heterogeneity. Seven isolated clones presented the basic characteristics of Biodeme Type III, with the same patterns of parasitemic curves, tissue tropism to skeletal muscle and myocardium, high pathogenicity with extensive necrotic-inflammatory lesions from the 20 to 30 day of infection. The parental strain and its clones C1, C3, C4 and C6, determined the higher levels of parasitemia, 20 to 30 days of infection, with high mortality rate up to 30 days (79 to 100%); clones C2, C5 and C7 presented lower levels of parasitemia, with low mortality rates (7.6 to 23%). Isoenzymic patterns, characteristic of zymodeme 1, (Z1) were similar for the parental strain and its seven clones. Results point to a phenotypic homogeneity of the clones isolated from the Colombian strain and suggest the predominance of a principal clone, responsible for the biological behavior of the parental strain and clones. Key-words: Trypanosoma cruzi. Colombian strain. Clonal structure. Clones. Biodemes. Zymodemes. Histopathology. Resumo A estrutura clonal da cepa Colombiana do Trypanosoma cruzi, biodema Tipo III e zimodema 1, foi analisada com o objetivo de caracterizar as suas populações e estabelecer a homogeneidade ou heterogeneidade das mesmas. Foram isolados sete clones, os quais apresentaram as características básicas do biodema Tipo III, com o mesmo padrão de curvas parasitêmicas, tropismo tecidual para músculo esquelético e miocárdio, alta patogenicidade, com extensas lesões necrótico-inflamatórias, do 20 ao 30 dia de infecção. A cepa parental e os clones C1, C3, C4 e C6 apresentaram os niveis mais elevados de parasitemia entre 20 e 30 dias pós-infecção e alto indice de mortalidade até 30 dias (79 a 100%); os clones C2, C5 e C7 apresentaram niveis mais baixos de parasitemia com baixa mortalidade até 30 dias (7,6 a 23%). Os padrões isoenzimáticos foram característicos do zimodema 1 (Z1) para a cepa parental e os sete clones. Os achados do presente trabalho indicam uma homogeneidade fenotípica entre os clones isolados da cepa Colombiana e sugerem a predominância de um clone principal, responsável pelo padrão de comportamento biológico da cepa parental e dos clones. Palavras-chaves: Trypanosoma cruzi. Cepa Colombiana. Estrutura clonal. Clones. Biodemas Zimodemas. Histopatologia. The Colombian strain of T. cruzi has been used in experimental investigations since the pioneering studies of Federici et al12. They described the progressive myocarditis occurring in mice as well as the main features of chronic disease in the murine model. Comparative studies of the biological behavior and histopathological lesions produced by the Colombian, Y17 and São Felipe strains1 showed marked differences in tissue tropism, virulence and pathogenicity3. These strains came to represent the prototypes for three different biological types or biodemes: I, II, III. The Colombian strain was isolated from a human case originating in Colombia12 and was typed as Biodeme Type III and identified as zymodeme Z1 by Andrade et al7, according to the isoenzymic patterns of Miles et al14. This classification corresponds to the recently 1. Laboratório de Doença de Chagas Experimental do Centro de Pesquisas Gonçalo Moniz/Fundação Instituto Oswaldo Cruz (FIOCRUZ). Salvador, BA. 2. Departamento de Ciências Biológicas, Universidade Estadual de Feira de Santana, Feira de Santana, BA. Financial support PAPES II – FIOCRUZ, Rio de Janeiro, RJ. Address to: Dra. Sonia G. Andrade. Centro de Pesquisas Gonçalo Moniz /FIOCRUZ. R. Valdemar Falcão 121, Brotas 41945-001 Salvador, BA. Fax: 55 71 356-2155. e-mail: [email protected] Recebido para publicação em 3/7/2000.