Characterization of a circulating antigen involved in immune complexes in visceral leishmaniasis patients.

Complications of visceral leishmaniasis are explained in part by immune complex pathology, particularly nephritis. Using the polyethylene glycol precipitation method, we identified among these complexes a Leishmania infantum circulating antigen by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. Monoclonal antibodies were produced to specifically detect this antigen. This protein (molecular weight 51 kD) is a cytoplasmic antigen of L. infantum and its synthesis by promastigotes is related to stationary-phase culture. It was present in sera from dogs whose leishmaniasis was associated with nephritis, and it was found in the sera of 30% of human patients with visceral leishmaniasis. It was also detected in the sera of patients with cutaneous leishmaniasis, and it persists in the sera of clinically cured subjects.