Antigenaemia and antibody response to Leishmania donovani stage-specific antigens and rk39 antigen in human immunodeficiency virus-infected patients

In order to define the possible markers for the early diagnosis of asymptomatic visceral leishmaniasis in human immunodeficiency virus (HIV)-infected individuals, the antigenaemia and antibody response to stage-specific Leishmania donovani and rk39 antigens is assessed by enzyme-linked immunosorbent assay (ELISA) and immunoreactivity to stage-specific antigens analysed by Western blot. Serum samples from two out of 100 HIV-infected individuals were found positive for antigenaemia, antibody response to stage-specific L. donovani antigens and rk39 antigen, and one sample was also positive for antigenaemia and antibody response to L. donovani antigens, while antibody detection to rk39 antigen was not carried on this sample. Additionally, one sample was found positive for amastigote antigenaemia and antibody response to amastigote antigen, while in this patient promastigote antigenaemia and antibody response to promastigote L. donovani and rk39 antigen could not be detected. One sample was found positive for antigenaemia, antibody response to amastigote antigen and negative for antibody response to promastigote antigen, while in this patient response to rk39 antigen was borderline. Although antibody response to rk39 antigen could be detected in 9/88 (10%) HIV-infected individuals, in six of these nine patients neither antigenaemia nor antibody response to stage-specific L. donovani antigens could be detected. All 10 confirmed visceral leishmaniasis and HIV-negative control patients had positive antigenaemia and antibody response to L. donovani amastigote and promastigote antigens, while all the normal healthy individuals were negative. The study indicated that detection of antibody response to rk39 antigen, amastigote antigenaemia and antibody response to amastigote antigen may prove to be better markers than detection of promastigote antigenaemia, antibody response to promastigote antigen and immunoblot reactivity.