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On-line version ISSN 1678-9946
Rev. Inst. Med. trop. S. Paulo vol.37 no.1 São Paulo Jan./Feb. 1995
Caracterização de uma cepa de Trypanosoma cruzi isolada de uma zona não endêmica no Nordeste do Brasil
Yara de Miranda GomesI; Tereza Cristina A. LealI; Marlene R. SilvaI; Christiane M. G. SantiagoII; Eridan M. CoutinhoI
ICentro de Pesquisas Aggeu Magalhães - FIOCRUZ, Av. Moraes Rego s/n. Cidade Universitária, 50670-420 Recife, PE, Brazil
IICentro de Pesquisas Gonçalo Moniz - FIOCRUZ, Rua Valdemar Falcão, 121, 40295-001 Salvador, Bahia, Brazil
A cepa WSL (Wild São Lorenço) de T. cruzi, isolada de um cobaio proveniente de São Lorenço da Mata (Nordeste do Brasil) foi caracterizada através da análise do seu comportamento morfobiológico e perfil isoenzimático. Para o estudo do comportamento morfobiológico, tripomastigotas sanguíneos (1 x 10 5) da cepa WSL foram inoculados por via intraperitonal em camundongos albinos Swiss. Como controle a cepa Y (Tipo I) foi usada. Durante o curso da infecção os seguintes parâmetros foram analisados: parasitemia, mortalidade, morfologia dos parasitas no sangue periférico e tropismo tissular. O perfil isoenzimático foi analisado em relação às enzimas ALAT, GPI e PGM usando como controle de referência as cepas Peruana (Tipo I), 21SF (Tipo II) e Colombiana (Tipo III). A cepa WSL apresentou as seguintes características biológicas: 1) multiplicação lenta e pico parasitêmico entre 21 - 25 dias pós-infecção; 2) mortalidade de 3,3% 40 dias pós-infecção; 3) predominância de formas largas no sangue periférico e 4) miotropismo com predominante envolvimento cardíaco. A análise isoenzimática mostrou um padrão de zimodema 2 (Z2) que corresponde às cepas biológicas Tipo II. Os resultados mostram que a cepa WSL apresenta baixa virulência e patogenicidade.
Chagas' disease presents a variety of epidemiological and clinical pictures in Latin America. In Brazil, the socioeconomic impact of the disease during the chronic stage is high. According to WHO 10 about 30% of the infected population (75,000 people) will develop severe cardiac and digestive lesions such as cardiac arrhythmia (45,000 cases) and megaesophagous and megacolon (30,000 cases) every year, thus presenting a serious public health problem.
Differences detected in the clinical presentation of Chagas' disease in different endemic areas, as well as the enormous variability in response of different T. cruzi strains to chemotherapeutic drugs, have led to the hypothesis that parasite strains can be a factor accounting for such discrepancies 2. The adoption of standard methods for strain classification as well as the need for analytical epidemiological studies to determine associations between T. cruzi strains and clinical and geographical varieties of Chagas' disease, was agreeded in an international meeting held in Panama City 9.
In Brazil, the classification of T. cruzi and their correlation with the clinical manifestations of the chagasic infection have been more detailed in the Reconcavo Baiano-Bahia State 1-4. In others areas of Northeast Brazil the incidence of domiciliated and infected vectors has been determined 5,6. However, the strains isolated in these regions were not fully characterized.
This work reports the characterization of a T. cruzi WSL (Wild São Lorenço) strain isolated from a naturally infected guinea pig from São Lorenço da Mata, rural area of the State of Pernambuco, in Northeast Brazil. Although this is considered a non-endemic area, some cases of chronic cardiac Chagas' disease have been found (MALTA, personnal communication).
For this sixty Swiss albino mice were inoculated with 1 x 105 trypomastigotes of the WSL strain by intraperitoneal route. As a control the Type I Y strain was used. The morphobiological behaviour as well as the histophathological study were analyzed according to ANDRADE 1 and BRENER 7. The isoenzymic study was performed according to ANDRADE 4. In this approach the following enzymes were investigated: alanine aminotransferase (E.C.18.104.22.168. ALAT), phosphoglucomutase (E.C.22.214.171.124. PGM) and glucosephosphate isomerase (E.C.126.96.36.199. GPI). As a reference control, the prototypes of each of the three morphobiological patterns (Peruviana-Type I; 21SF-Type II and Colombiana-Type III) were included on each electrophoretic running.
The WSL strain presented slow multiplication and parasitemic peaks within 21 and 25 days postinfection (Fig. 1A). Cumulative mortality was 3.3% at the 31-40 days after infection. It was verified a predominance of broad forms of the parasite throughout the course, with the presence of slender forms in the earlier phase (Fig. 1B). Myotropism with predominant cardiac involvement was detected. The WSL strain was classified as Type II by its morphobiological characters. Data obtained for the Y strain shows the already described characteristics of Type I strains (rapid multiplication, predominance of slender forms, macrophagotropism and high virulence). The isoenzymic analysis showed the pattern of zymodeme 2 (Z2) that has been shown to correspond to the biological Type II strains (Fig. 2). Thus, we conclude from the above data that the WSL strain has a very low virulence and pathogenicity. May be this could explain the difficulties in the clinical identification of Chagas' disease in São Lorenço da Mata. One could also especulate that the infection with low virulence and pathogenicity strains may protect against infection with more virulent strains.
The WSL strain was initially referred as W strain 8. However, to differentiate it from W or WBH strain isolated from a Brazilian patient in 1926 by Reychenov, the designation WSL is now being proposed.
To Dr. Sonia Andrade for scientific support and to Dr. Frederico Abath for helpful discussion. This work was supported by: Fundação de Amparo a Ciência e Tcnologia do Estado de Pernambuco (FACEPE) and FIOCRUZ.
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2. ANDRADE, S.G. - Morphological and behavioural characterization of Trypanosoma cruzi strains. Rev. Soc. bras. Med. trop., 18 (suppl.): 39-46, 1985. [ Links ]
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Recebido para publicação em 14/06/1994
Aceito para publicação em 02/08/1994