Immunoblot analysis of the antibody response to antigens of Leishmania donovani in Indian kala-azar

When infected with Leishmania donovani, patients develop specific antibodie s that constitute the basis of serodiagnosis. Using immunoblot analysis, we examined the antibody response to antigens of L. donovani in 35 kalaazar ( KA) patients and 67 controls. Sera from KA patients recognised numerous ant igens with molecular weights ranging from 14-110 kDa. Antigens of 40 kDa, 5 5 kDa, 65 kDa, 70 kDa and 82 kDa were recognised most frequently. All KA pa tients produce an antibody response to one or more of these antigens. The m ajority (83%) of KA cases recognised at least four of these five parasite a ntigens. The 70 kDa antigen showed the greatest sensitivity for Indian KA, and produced a positive reaction in 94% of patients. This antigen gave 10% false-positive reactions in controls comprising patients with related disea ses (i.e. tuberculosis, leprosy and malaria) and in healthy controls. Data indicated that the 70 kDa antigen may include a member of the heat shock pr otein 70 family. Studies with four clinical isolates of L. donovani showed that the 70 kDa component was expressed in all the strains examined. Immuno blot assay (Western blotting) provided a sensitive diagnostic test for KA p atients, and identified the 70 kDa parasite antigen that is promising as a potential target antigen for the development of less complex serodiagnostic assays for KA.