Immunologic Tests in Patients After Clinical Cure of Visceral Leishmaniasis

Abstract

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 > or = 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.

Significance of persistence of antibodies against Leishmania infantum in sicilian patients affected by acute visceral leishmaniasis

“…In conclusion, our results, confirming and extending previous studies [7][8][9][10][11][12][13], showed that specific antibodies to L. infantum might persist for many years, and decrease slowly, but steadily. The persistence of these specific antibodies, at low-medium levels, is not related to poor therapeutic response or prognosis, but an acute increase in their levels, or the persistence of high antibody levels, might be useful in identifying LV relapse or resistance to specific therapy.…”

“…Based on the results of our study, patients specifically cured and apparently healed after an acute episode of VL could be divided into three subtypes of antibody response: (1) patients whose anti-L. infantum antibodies disappear within 2 years after diagnosis and treatment, as just reported in the literature [7][8][9][10][11][12][13]; (2) patients showing low antibody titers for 4-6 years; and (3) patients whose antibody titers remain constantly at low-medium levels for more than 6 years.…”

“…In this contest, some studies have demonstrated that serological tests for VL (i.e., ELISA using rK39, rK26, and crude Leishmania antigen) in VL patients after clinical cure might continue to be positive after treatment of the disease and cannot be used as an indicator of an adverse therapeutic and prognostic evolution [9,26].…”

“…VL patients were treated with a complete course of meglumine antimoniate (MA, 20 mg/kg daily, by intramuscular injection, for 4 weeks) [9,14] or liposomal amphotericin B (1-3 mg/kg daily, for 5 days, with a final dose at 11th day, with no incremental dosage, infused slowly over 2 h). Patients were considered cured and discharged when fever subsided, and there was weight gain and absence of L. infantum bodies in the bone marrow aspirates and/or biopsy.…”

“…In some studies, the persistence of antibodies for prolonged periods after treatment appears to indicate a therapeutic inefficacy or also the possibility of disease reactivation, while in other reports, there is not any indication of a poor prognosis and/or a risk of VL relapse [7][8][9][10][11][12][13].…”