Parvovirus B19 does not bind to membrane-associated globoside in vitro

The glycosphingolipid globoside (globotetraosylceramide, Gb4Cer) has been proposed to be the cellular receptor of human parvovirus B19. Quantitative measurements of the binding of parvovirus B19 to Gb4Cer were performed to explore the molecular basis of the virus tropism. Solid-phase assays with fluorescence-labeled liposomes or 125iodine-labeled empty capsids were used to characterize the specificity of binding. In addition, surface plasmon resonance on lipid layers, as well as isothermal titration microcalorimetry, was utilized for real-time analysis of the virus-receptor interaction. These studies did not confirm binding of Gb4Cer to recombinant B19 VP2 capsids, suggesting that Gb4Cer does not function on its own as the cellular receptor of human parvovirus B19, but might be involved in a more complex recognition event. The biochemical results were further confirmed by cryo-electron microscopy image reconstructions at 10 Å resolution, in which the structures of empty capsids were compared with empty capsids incubated with Gb4Cer.