PCR (POLYMERASE CHAIN REACTION) AS A DIAGNOSTIC TOOL FOR LEISHMANIASIS: OLD PROBLEMS SOLVED AND NEW QUESTION RAISE

Abstract
As it is well known, the conventional methods for diagnosis of American cutaneous leishmaniasis (ACL) present limitations, justifying the development and validation of new diagnostic approaches. In this direction, we identified the major promastigote antigens of Leishmania (Viannia) braziliensis. The antigens of 27 (Lb27) and 30 kDa (Lb30) were recognized by approximately 90% of the patients presenting active lesions. These antigens are relevant for both diagnosis and monitoring of clinical cure. Sera from patients clinically cured from ACL recognized the 19 kDa antigen (Lb19) more frequently than patients with active lesions, suggesting that this antigen is important for protective immunity. In another investigation, we analysed by PCR 119 cutaneous biopsies of patients with ACL and non-leishmaniasis lesions. The PCR based systems were 100% specific. In addition, they were significantly more sensitive than smear examination, histological staining and isolation by culture. Finally, we analyzed scar biopsies from patients clinically cured after specific chemotherapy, and DNA specific for Leishmania (Viannia) was detected in scars of 30 out of 32 (93.7%) patients. Furthermore, Leishmania could be isolated by culture in a few of these scars, and the isolates were able to infect experimental animals, suggesting that the persistence of parasites is the rule rather than the exception in leishmaniasis. Thus, in one hand, the molecular tools overcome the limitations of the conventional diagnostic tests. On the other hand, the demonstration that parasites persist after clinical cure of ACL raises several new questions regarding the clinical evolution, epidemiology and control of the disease.

Bibliografía del artículo

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