Located within the minimal neutralizing SU 90–98 epitope are residues that, as described above, mediate direct binding of the SU to NRP-1: a pentapeptide corresponding to residues 90–94 was shown to block both the binding to, and infection of, cells by HTLV-1, and to be capable of directly binding to NRP-1 [17].The arginine residue within this motif is the same residue (R94) shown in early studies to be important for cell-cell transmission of the virus [44]. This evidence concerns the gene NRP1 and infection.