Strain-specific recognition of live Leishmania donovani promastigotes by homologous antiserum raised against a crude membrane fraction of infected macrophages.

Surface antigens on Leishmania promastigotes and infected macrophages are obvious targets in immunoprophylaxis for leishmanial infection. We have recently demonstrated that the polyclonal antiserum and monoclonal antibodies generated by homologous immunizations with the crude membranes of parasite-infected cells react effectively with the 'neo-antigenic' determinants on the infected cell surface. In the present study, we investigated the utility of such polyclonal antisera for identifying 'minor' surface components of promastigotes. The reactivity of anti-Leishmania donovani-(strain RMRI68) infected macrophage membrane (anti-IMm) antiserum was compared with that of anti-promastigote (anti-Pr) antiserum towards the infected macrophage surface and promastigotes of three Indian strains of L. (donovani, RMRI68, AG83 and DD8. While anti-Pr antiserum showed no reactivity with the infected macrophage surface but reacted strongly with air dried and live promastigotes of all three strains, anti-IMm antiserum reacted with the infected cell surface and, interestingly, specifically recognized live promastigotes of the strain used for infection, i.e., strain RMRI68. The reactivity patterns of the two antisera with the immunodominant components of the L. donovani promastigote surface, i.e., purified LPG-KMP11 complex and gp63 molecules, indicated that unlike anti-Pr antiserum, the specificities in anti-IMm antiserum were mainly directed towards molecules other than the LPG-KMP11 complex and gp63. Antiserum generated in a similar fashion against the macrophage membrane of cells infected in vitro with strain AG83 also contained antibodies specific to strain AG83 promastigotes. The present approach may therefore greatly help in identifying specific antigen(s) important in clinical and epidemiological control of leishmaniasis.