Since we had determined that inhibition with both peptides occurs at a viral entry step, we asked if infection could still be inhibited after virus had bound to the surface of target cells. We bound virus to cells at 4uC, then treated with increasing concentrations of DN57opt or 1OAN1 before warming the cells back to 37uC and allowing the infections to progress ( Figure 6C and D). Inhibition of viral entry was observed for both peptides when added to the virus after it was bound to target cells.