Identification and characterization of a novel Leishmania donovani antigen for serodiagnosis of visceral leishmaniasis.

Despite several drawbacks, rK39-based rapid immunochromatographic test is widely used for the diagnosis of visceral leishmaniasis (VL) in the Indian subcontinent. There is an urgent need to develop a better antigen. In this study we separated crude soluble antigens of Leishmania donovani by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and hybridized with pool sera from pre- and post-treated VL patients, 6 months follow-up, endemic healthy (EHC), and nonendemic healthy controls (NEHC) by Western blotting. The sensitivity of enzyme-linked immunosorbent assay with identified protein was 95% (confidence interval [CI] = 89.6-98.01%), whereas the specificity for EHC, NEHC, and different disease groups were 96.3% (CI = 89.8-98.6%), 100% (CI = 95.8-100%), and 97.4% (CI = 91.02-99.3%), respectively. This specific antigen was subjected to two-dimensional gel electrophoresis and after tryptic digestion, antigen was characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Further analysis showed that it is a member of the heat shock protein family of 70 kDa, designated as BHUP1, and has great potential in the diagnosis of VL.