Fig. 8. Cooperative action of multivallent attachment sites in SVPs. (A) DMSO-treated HepG2 cells were pre-incubated for 2 h with 500 µg/ml of either BSA or recombinant preS1 as competitors prior to addition of preS1-conjugated beads. The soluble competitor proteins were pre-incubated at 100× the concentration of the conjugated ligand. The percentage of cells of the total population that attached more than four beads per cell is shown (upper panels). The experiment was carried out with an increasing amount of the competitor as indicated (lower panel). (B) The attachment of the preS1–beads was neutralized by pre-incubation of the beads for 2 h with either monoclonal anti-preS1 (MA 18/7) or the control monoclonal anti-HBcAg (ns, non-specific), as indicated.