MALCHIODI Emilio Luis
Polymerase chain reaction reveals T. cruzi infection suspected by serology in leishmaniasis patients.
CHIARAMONTE MG, FRANK FM, FURER GM, TARANTO NJ, MARGNI RA & MALCHIODI EL.
Año: 1999 vol. 72 p. 295 - 308
The existence of patients suffering a double infection caused by Trypanosoma cruzi and Leishmania spp has been suggested by several authors. Since the conventional serological tests now available for the diagnosis of Chagas disease lack specificity due to the cross-reactivity between these two parasites, a serological confirmation of a T. cruzi infection cannot be made unless specific antigens are used. An enzyme linked immunosorbent assay (ELISA) to detect antibodies against a specific T. cruzi antigen, named Ag 163B6, and an immunoblotting using T. cruzi epimastigotes, are non-conventional serological techniques that could be employed for specific diagnosis of Chagas disease. Using these two methods 34 cutaneous or mucocutaneous leishmaniasis patients were classified into 2 groups: A) patients with serological evidence of T. cruzi infection, those who tested positive in at least one assay (18/34); B) patients with no serological evidence of T. cruzi infection, those who were negative for both assays (16/34). Taking into account the difficulties of xenodiagnosis and its low sensitivity (less than 50%) for a direct diagnosis in the chronic period of the disease, we used polymerase chain reaction (PCR) to confirm a T. cruzi infection in those leishmaniasis patients who presented positive results with the non-conventional serological techniques. Seventeen of the 18 patients with serological evidence of T. cruzi infection gave positive results when genomic DNA primers were used. Using minicircle primers, 15/18 of that group were positive. Nevertheless, all the patients suspected of being double infected were positive in at least one PCR test. Just one patient with no serological evidence of T. cruzi infection gave a positive PCR result when amplifying the minicircle sequence. The proof of the existence of a T. cruzi infection by PCR in leishmaniasis patients suspected to be chagasic when non-conventional serology was used, strongly sustains the use of the specific Ag163B6 and the immunoblotting with epimastigotes as specific serological diagnostic tools to determine a T. cruzi infection.