Figure 1. Inhibition of HPV16-GFP (green fluorescent protein–labeled human papillomavirus 16) pseudovirus infection in HeLa cells by human defensins. Pseudovirus and inhibitors were added to subconfluent cells in 96 well plates and GFP-positive cells were counted by a fluorescence-activated cell sorter (FACS) 3 days post infection. Heparin is a highly sulfated form of heparan sulfate previously described as a potent inhibitor of papillomavirus infection.