Polylactosamines are not obligate receptors for invasion of Plasmodium falciparum malaria as shown in HEMPAS Variant II-gal- erythrocytes

A HEMPAS (hereditary erythroblastic multinuclearity with positiveacidified serum test) erythrocyte, atypical Variant II (referredto herein as Variant II-gal^-), lacking long-chain polylactosamineon both glycoproteins (Band 3 and 4.5) and glycosphingolipids,was characterized by the carbohydrate profile of the erythrocytemembrane according to Fukuda et al. (Blood, 73, 1331–1339,1989). Two laboratories previously reported that polylactosamineisolated from the erythrocyte protein Band 3 inhibited invasionof red blood cells by Plasmodium falciparum in malarial culture,suggesting a role for this carbohydrate in adhesion of the parasite.Therefore, HEMPAS erythrocyte Variant II-gal^- presented a uniqueopportunity to further examine this premise. Freshly drawn bloodsamples (normal and HEMPAS Variant II-gal^-) were separatelyincubated with P.falciparum from mannitol-synchronized cultures.The parasite was found to invade HEMPAS Variant II-gal^- erythrocytesat a 30% lower rate through two life cycles, as shown by microscopicevaluation of invasion and by ³H]hypoxanthine incorporationinto parasite. This observation, along with the published factthat glycophorin-deficient M^kM^k cells are also infectable, butat a lower rate, indicates that neither sialoglycoproteins norpolylactosamines are an obligate adhesive ligand for P.falciparum,although the possibility remains that either may still contributeto adhesive events during infection. HEMPAS malaria Plasmodium falciparum polylactosamine