Exometabolites ofLeishmania donovani promastigotes

Abstract

The defined medium of Steiger and Steiger conditioned by growth ofLeishmania donovani strain 3S promastigotes served as the primary source of parasite exometabolites. Four fractions of the conditioned medium were recovered by Sephadex G-25 column chromatography. These fractions shared immunologic determinants, but differed in their molecular weights, affinity for Sephadex G-25, and absorption spectra. Degradation and/or aggregation of one of the fractions (Fraction IV) appeared to yield substances found in the remaining three fractions. Furthermore, by appropriate manipulations, Fraction IV could be transformed into substances resembling those described by previous workers, eg., excretory factor (EF) or antigenically active glycoproteins (AAGP). The present findings suggest that the primary exometabolite released byL. donovani is a small glycopeptide-like molecule; however, in media conditioned by growth of promastigotes and during isolation procedures, aggregation and/or degradation processes yield higher molecular weight substances which vary in size and physico-chemical properties.