Interactions between L1 and sulfated sugars on the cell surface promote initial attachment of the virus.[31][32] The virus is then able to get inside from the cell surface via interaction with a specific receptor, likely via the alpha-6 beta-4 integrin,[33][34] and transported to membrane-enclosed vesicles called endosomes.[35][36] The capsid protein L2 disrupts the membrane of the endosome through a cationic cell-penetrating peptide, allowing the viral genome to escape and traffic, along with L2, to the cell nucleus.[37][38][39]