Abstract
This review describes and appraises a novel protein-based antigen detection test for visceral leishmaniasis (VL). The test detects in patient’s urine six proteins from Leishmania infantum (chagasi) and Leishmania donovani, the etiological agents of VL. The gold standard test for VL is microscopic observation of the parasites in aspirates from spleen, liver, or bone marrow (and lymph node for dogs). Culture of the parasites or detection of their DNA in these aspirates are also commonly used. Serological tests are available but they cannot distinguish patients with active VL from either healthy subjects exposed to the parasites or from subjects who had a successful VL treatment. An antigen detection test based on the agglutination of anti-leishmania carbohydrates antibody coated latex beads has been described. However, the results obtained with this carbohydrate-based test have been conflicting. Using mass spectrometry, we discovered six L. infantum/L. donovani proteins excreted in the urine of VL patients and used them as markers for the development of a robust mAb-based antigen (protein) detection test. The test is assembled in a multiplexed format to simultaneously detect all six markers. Its initial clinical validation showed a sensitivity of 93% and specificity of 100% for VL diagnosis.
Highlights
Visceral leishmaniasis (VL) or kala-azar is a systemic parasitic disease that is endemic in 75 countries with more than 200 million people at risk of infection
Serological tests are not suitable for diagnosing active VL for several reasons, which include: (a) high serum antibody levels are present in both asymptomatic and active VL [23,24,25,26,27,28]; (b) serum anti-Leishmania antibodies remain in the circulation for several years after cure, which complicates the diagnosis of relapsed VL [29,30,31]; (c) some individuals from endemic areas with no history of VL have anti-leishmanial antibodies, which is a major hindrance for these tests sensitivity/specificity [32]; and (d) sensitivity of serological tests in VL/human immunodeficiency virus (HIV) co-infected patients is poor, if VL occurs after HIV infection [33,34]
We firstly identified three parasite biomarkers of VL caused by L. infantum and later on three others from L. donovani [62,65]
Summary
Visceral leishmaniasis (VL) or kala-azar is a systemic parasitic disease that is endemic in 75 countries with more than 200 million people at risk of infection. Serological tests are not suitable for diagnosing active VL for several reasons, which include: (a) high serum antibody levels are present in both asymptomatic and active VL [23,24,25,26,27,28]; (b) serum anti-Leishmania antibodies remain in the circulation for several years after cure, which complicates the diagnosis of relapsed VL [29,30,31]; (c) some individuals from endemic areas with no history of VL have anti-leishmanial antibodies, which is a major hindrance for these tests sensitivity/specificity [32]; and (d) sensitivity of serological tests in VL/HIV co-infected patients is poor, if VL occurs after HIV infection [33,34] Interesting alternatives to these diagnostic procedures are platforms that detect pathogen antigens (proteins or carbohydrates) in bodily fluids.
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