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An enzyme-linked immunosorbent assay (ELISA) using native gp63 for detection of serum antibodies to Leishmania was evaluated. The test identified antibodies in sera from 16 of 16 visceral leishmaniasis (VL) patients and 9 of 12 sera from patients with Trypanosoma brucei infection. In comparison, sera from 80 Danish controls and 40 control donors from a malaria endemic area of Ghana without known exposure to Leishmania were negative, as were sera from 12 Kenyan malaria patients and 9 schistosomiasis patients. After cure of VL, sera rapidly became negative. Only 1 of 7, 1 of 21, and 1 of 27 sera from cured VL patients 6-12 months, 1-2 years and > 2 years after cure were positive. Thus, in contrast to other serological tests for VL, the gp63 ELISA seems to distinguish an ongoing from a past infection. This might prove useful both for diagnostic and epidemiological purposes.

In a cross-sectional house-to-house study in a leishmaniasis-endemic area in Kenya, the cellular and humoral immune response to Leishmania lipophosphoglycan (LPG) was determined. Clinical data, peripheral blood mononuclear cells, and plasma were obtained from 50 individuals over the age of eight years. Lymphoproliferation and interferon-gamma (IFN-gamma) production by these cells were examined. It was shown that cells from all six individuals in the population with a history of kala-azar responded to LPG in the lymphocyte proliferation assay, and four of these six responded in the IFN-gamma assay. In contrast, cells from 12 of 44 individuals from the study area with no history of kala-azar and none of the five Danish control samples responded to LPG. Antibodies against LPG were detected by enzyme-linked immunosorbent assay in 45 of 50 plasma samples. Our findings clearly show that mononuclear cells from kala-azar patients cured of infection were able to respond to the LPG preparation. The finding of a specific cellular immune response to LPG in 12 of 44 individuals with no history of kala-azar is consistent with previous epidemiologic studies, in which it has been shown that a proportion of L. donovani infections run a subclinical course. The high frequency of individuals with antibodies against LPG might indicate that a majority of the population had been exposed to the parasite.(ABSTRACT TRUNCATED AT 250 WORDS)