Abstract
Visceral leishmaniasis (VL), a fatal parasitic infection, is categorized as being neglected among tropical diseases. The use of conventional tissue aspiration for diagnosis is not possible in every setting. The immunochromatography-based lateral flow assay (LFA) has attracted attention for a long time due to its ability to give results within a few minutes, mainly in resource-poor settings. In the present study, we optimized and developed the LFA to detect anti-Leishmania antibodies for VL diagnosis. The performance of the developed test was evaluated with serum and urine samples of Indian VL patients and Brazilian sera. The new test exploits well-studied and highly-sensitive purified antigens, LAg isolated from Leishmania donovani promastigotes and protein G conjugated colloidal-gold as a signal reporter. The intensity of the bands depicting the antigen–antibody complex was optimized under different experimental conditions and quantitatively analyzed by the ImageJ software. For the diagnosis of human VL in India, LFA was found to be 96.49% sensitive and 95% specific with serum, and 95.12% sensitive and 96.36% specific with urine samples, respectively. The sensitivity and specificity of LFA were 88.57% and 94.73%, respectively, for the diagnosis of Brazilian VL using patients’ sera infected with Leishmania infantum. LFA is rapid and simple to apply, suitable for field usage where results can be interpreted visually and particularly sensitive and specific in the diagnosis of human VL. Serum and urine LFA may improve diagnostic outcomes and could be an alternative for VL diagnosis in settings where tissue aspiration is difficult to perform.
Highlights
We developed Leishmania promastigote membrane antigens (LAg)-based lateral flow assay (LFA) to detect antibodies in samples qualitatively
As the diagnostic potential of LAg has been apparent in ELISA and dipstick tests in our previous studies, here we developed the LFA format to improve its diagnostic aptitude and assessed its performance with serum and urine of Indian Visceral leishmaniasis (VL) patients and with Brazilian sera [13,19,20]
8 serum and 12 urine samples from healthy individuals were obtained from relatives of the patients as endemic controls; 20 serum and 18 urine samples were collected from diseases other than VL, including four each of malaria, tuberculosis and typhoid, three of dengue, two of gastroenteritis and influenza-like illness along with two serum samples of filariasis and systemic lupus erythematosus
Summary
Visceral leishmaniasis (VL) or kala-azar is a serious yet neglected parasitic disease of tropical and sub-tropical regions [1]. The disease has been endemic mainly in the Indian Subcontinent, Latin America and East Africa [2]. The global extent of this disease is continuously changing, with reports of the disease arising from the newer areas of Southern Europe and Mediterranean regions [3].
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