CARBOHYDRATE AND LPG EXPRESSION IN LEISHMANIA-VIANNIA SUBGENUS

Glycosylated molecules expressed on the cell surface of Leishmania pro mastigotes contribute to the outcome of contact between the parasite a nd its invertebrate and vertebrate hosts. The expression of several su ch molecules is growth phase dependent. Information on the expression of carbohydrates by Leishmania of the Viannia subgenus (braziliensis c omplex), a widespread cause of morbidity in the Americas, is fragmenta ry. We have examined the relationship between growth phase and the exp ression of glycosylated surface structures in WHO reference strains of 3 species of the Viannia subgenus, i.e., L. panamensis, L. guyanensis , and L. braziliensis. Agglutination with lectins and the monoclonal a ntibody specific for the repeat unit of L. donovani lipophosphoglycan, CA7AE, distinguished logarithmic and stationary-phase promastigotes o f all 3 species. Flow cytometry revealed increased heterogeneity and d isparity in the expression of the repeat unit epitope in stationary-as compared to logarithmic-phase promastigotes. Biochemical analyses sho wed the LPG repeat unit of all 3 species reference strains to be const ituted by mannose and galactose with little or no substitution and, he nce, to be similar to the LPG of L. donovani. Initial quantitative ana lyses of L. braziliensis LPG indicated a 10-fold lower quantity of LPG in this species than L. donovani and an increase in the size of LPG i n the stationary phase. These findings provide bases for isolating and biologically characterizing phenotypically distinct populations of pr omastigotes and for identifying molecular determinants of the host par asite-relationship among Leishmania Viannia.