Abstract
Visceral leishmaniasis (VL), also known as kala-azar, is an important public health problem. If not treated, virtually all clinically symptomatic patients die within months. The diagnosis is based on the Montenegro skin test (MST) and anti-Leishmania titers. Nevertheless, the time required for cured individuals living in a leishmaniasis-endemic area to present a positive skin test and negative anti-Leishmania serology is known. To determine the cellular and humoral immune response profile in relation to different times post-VL cure, a cross-sectional study was conducted on subjects from a kala-azar endemic area in Paço do Lumiar, MA, Brazil, on the basis of 1995-2005 notifications reported by the National Health Foundation/Regional Coordination of Maranhão. We visited cured individuals with a history of VL within the last 10 years. Seventy-four subjects (30 females) ranging in age from 1 to 44 years were included, all of them symptom free at the time of the study. A cellular immune response was observed in 73 (98.6%) subjects, whereas no significant antibody titers were detected by indirect immunofluorescence (IIF) in the sera of 69 (93.2%) cases. Ten years post-cure, 39 (52%) subjects had a positive MST and negative IIF reaction, while in one subject the skin and anti-Leishmania serology tests were negative. Two other subjects were positive in both tests 1 year after cure. These data suggest that a cellular immune response may still be present in subjects cured of VL regardless of post-cure time, and that the parasite persists in the host after clinical cure of the disease. This would explain the persistence of significant Leishmania sp antibody titers in some subjects after treatment.
Highlights
Visceral leishmaniasis (VL), known as kala-azar, is an important public health problem that affects poor populations in 70 countries in Asia, East Africa, South America, and the Mediterranean region
Various immunological abnormalities have been documented in VL patients, including unresponsive skin tests (Montenegro skin test, MST) and high Leishmania antibody titers, which have been used as a laboratory diagnostic criterion of the disease [4,5]
We found that 98.6% of the subjects were MST positive 10 years post-cure, which contrasts with findings obtained in the endemic area of Jacobina, BA, where only 15.5% of the individuals presented a cellular response at 4 to 9 years post-cure of the disease [7], and with Mayrink et al [8] who reported a 4.1% positivity rate in individuals with post-cure periods ranging from 8 to 720 days [8]
Summary
Visceral leishmaniasis (VL), known as kala-azar, is an important public health problem that affects poor populations in 70 countries in Asia, East Africa, South America, and the Mediterranean region. Leishmaniasis has emerged as an opportunistic infection, representing an important co-infection in immunodepressed patients and a major sanitary problem [2]. Diagnosis of VL is based on epidemiological data and clinical and laboratory findings, but the definitive diagnosis can only be made by detecting the parasite in infected tissues [3]. Immunocompetent individuals show negative results in skin tests when they are in the acute phase of VL. Serological tests may be useful for the diagnosis of visceral leishmaniasis, as they have a high predictive value in the diagnosis of immunocompetent individuals
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