Leishmania:Amastigotes Synthesize Conserved Secretory Acid Phosphatases during Human Infection

Abstract

Ellis, S. L., Shakarian, A. M., and Dwyer, D. M., 1998.Leishmania:Amastigotes synthesize conserved secretory acid phosphatases during human infection.Experimental Parasitology89, 161–168.Leishmania donovaniis the major causative agent of Old World human visceral leishmaniasis (VL).In vitro, both promastigotes and axenic amastigotes ofL. donovaniconstitutively secrete soluble acid phosphatases (SAcPs), which contain conserved antigenic epitopes. These SAcPs are the most abundant and best characterized secretory proteins of this parasite. The aim of this study was to determine whether this enzyme was produced by intracellular amastigotes during the course of human infection. To that end, sera from acutely infected leishmaniasis patients were tested for anti-SAcP antibodies usingL. donovanipromastigote culture supernatants. Our results showed that VL patient sera from different endemic foci immunoprecipitated parasite SAcP enzyme activity. Further, these VL patient sera recognized the 110- and 130-kDa SAcPs in both Western blots and radioimmunoprecipitation assays. Results of tunicamycin experiments demonstrated that VL patient anti-SAcP antibodies were directed against the polypeptide backbone of the parasite SAcPs. In addition, both radiolabeledL. donovaniSAcPs and native enzyme activities were immunoprecipitated by sera from patients with various forms of cutaneous leishmaniasis. Together, these studies demonstrate thatLeishmaniaamastigotes produce SAcPs during the course of human infections.