Immunologic tests in patients after clinical cure of visceral leishmaniasis

The results of five serologic tests (ELISA using promastigote antigen [ELISAp] and recombinant K39 [ELISArK39] and K26 [ELISArK26] antigens, indirect immunofluorescence test using promastigote antigen [IIFT], and immunochromatographic tests using the rK39 antigen [TRALd]) and of the Montenegro skin test (MST) were analyzed in 41 individuals treated for kala-azar and living in Porteirinha, Minas Gerais, Brazil. The tests were carried out 1 week to 12 years after specific treatment. All MSTs during the 8 months after treatment were negative, whereas after 1 year, 28 (84.8%) were positive. Negativity in all serologic tests was observed for 11 (26.8%) of the 41 individuals, whereas positivity in at least one test was observed for 70.3% of subjects evaluated ≥ 2 years after treatment. With respect to each exam, positivity was 38.0% for TRALd, 61.9% for ELISA rK39, 47.6% for ELISA rK26, 38.0% for ELISAp, and 40.5% for IIFT. None of the individuals presented recurrence of the disease during the 4 years of follow-up. The tests were repeated in 24 of the 41 individuals, after some time, and the results were the same in 33.3% of the cases. We conclude that serological tests for kala-azar might continue to be positive after treatment of the disease, although this does not indicate a poor prognosis or a poor therapeutic response.