LEISHMANIA (VIANNIA) BRAZILIENSIS - BIOLOGICAL BEHAVIOR IN GOLDEN-HAMSTERS OF ISOLATES FROM ARGENTINE PATIENTS

This study reports intraspecific variations of native isolates of Leis hmania (Viannia) braziliensis from patients with leishmaniasis from Sa lta, Argentina. These isolates induced skin lesions in golden hamsters , initially showing rapid development, reaching their largest size bet ween 28 and 35 days postinfection (PI). Thereafter, the infections wer e self-limiting and total regression was observed at 80-150 days PI. T he majority of the native isolates were characterized by low infectivi ty in the experimental animals, and a classic pattern of dissemination to systemic organs was established. However, unusual features for L. braziliensis were displayed by two isolates; one showed evidence of hi gh infectivity in hamsters characterized by a short prepatent period a nd larger, severe and persistent lesions at the inoculation site. The other isolate, of low infectivity, showed cutaneous metastasis and rec urrent systemic dissemination in the same animals, suggesting dissocia tion between infectivity and pathogenicity. Metastasis has been freque ntly described in hamsters infected with L. (V) guyanensis and L. (V) panamensis, but not in infections induced by L. (V) braziliensis, as w as observed in this study. Active and/or regressive histopathologic le sions were observed, depending on the stage of the infection. An exuda tive and mixed inflammatory pattern with microabscesses and necrotic a reas was observed during early infection, while well-defined granuloma s and collagen formation were the predominant features detected at a l ater time. Amastigotes were easily detected in the tissues, although i n low numbers. Schaumann bodies were always detected. The characteriza tion of the unique features of these native isolates, and the verifica tion of their reproducibility in vitro and in vivo will be useful tool s in tests related to immunoprophylaxis and chemotherapy.