CARACTERIZACI 3N PARASITOL 3GICA, PATOG\uc9NICA E INMUNOG\uc9NICA DE CEPAS SALVAJES DE T. cruzi AISLADAS EN LOS ESTADOS LARA Y YARACUY - VENEZUELA

Se determinaron las caracter\uedsticas parasitol\uf3gicas, patog\ue9nicas e inmunog\ue9nicas de cepas salvajes de T.cruzi, aislados en los estados Lara y Yaracuy en Venezuela, comparadas con la cepa patr\uf3n YBM. La muestra consisti\uf3 de cuarenta ratas (40) Sprague Dawley de 03 semanas de edad, divididas en 04 grupos de 10 ratas c/u. Cada rata fue inoculada con 100 tripomastigotes metac\uedclicos/gr. peso del animal, v\ueda intrad\ue9rmica. Cada grupo fue tratado con una cepa diferente, cuya identificaci\uf3n y procedencia era desconocida para los investigadores (m\ue9todo doble ciego). La parasitemia fue evaluada cada semana por 8 semanas mediante un Hemocit\uf3metro. La integridad del Sistema Nervioso Aut\uf3nomo (SNA) y de la funcionalidad cardiaca fue evaluada mediante estudios electrocardiogr\ue1ficos realizados antes y despu\ue9s de administrar Fenilefrina 1mg/Kg. Se realizaron tres estudios electrocardiogr\ue1ficos: animal sano (pre - inoculaci\uf3n), etapa aguda (4 semanas post - inoculaci\uf3n) y etapa subaguda (9 semanas post - inoculaci\uf3n). La inmunogenicidad fue medida a los dos meses post inoculaci\uf3n, mediante la titulaci\uf3n de anticuerpos tipo IgG anti-T.cruzi y mediante Hipersensibilidad retardada. Nuestros estudios revelaron que la cepa Cauderales mostr\uf3 la mayor (p ABSTRACT \ua0 Parasitologic, pathogenic and immunogenic\u92s T. cruzi characteristics were determined from wild strains isolated from vectors and reservoirs in the states of Lara and Yaracuy at Venezuela, as compared with the already characterized YBM stock. Sample consisted of forty 03 weeks of age- Sprague Dawley rats, divided in 04 groups of 10 rats each. Rats were inoculated with 100 metacyclic trypomastigotes per gr. of the animal, via intradermic. Each group was inoculated with a different strain, whose identification and origin of both were not known by researchers (double blind trial). Blood parasite levels were evaluated every week for 8 weeks using an hemocitometer. Autonomic nervous system (ANS) and cardiac functionality were evaluated by means of electrocardiographic studies made before and after fenilefrine administration at doses of 1mg/Kg. Three electrocardiographic studies were made: when animals were healthy (pre-inoculation), in the acute stage (4 weeks post-inoculation) and in subacute stage (9 weeks postinoculation). The immunogenicity was measured 2 months after inoculation, by measuring the levels of IgG serum anti-T.cruzi antibodies and retarded hypersensitivity. Our results revealed that Cauderales\u92 strain displayed greater blood parasite levels (p < 0,05) as compared with Nirgua\u92s and YBM\u92s strains, which shown the smallest blood parasite levels; Guariquito\u92s did not induce any parasitemia. Nirgua\u92s strain displayed greater humoral type immunogenicity and a greater alteration of the ANS as compared with YBM\u92s strain, reflected by a significant increase of the fenilefrine induced-bradicardia in the acute period of the disease and a significant tachicardia in the subacute period of the disease. Cauderales\u92 showed an humoral immunogenicity similar to YBM and they did not display alterations in the ANS. Guariquito\u92s did not show any humoral immune response, nevertheless; they presented alterations in the ANS. Retarded hypersensitivity was similar for all the stains and significant differences in the electrocardiographic parameters were not observed. In conclusion the present study demonstrates that circulating T. cruzi strains in Lara and Yaracuy are different from YBM