Amino acid alignment of the RBD region in the SUgp46 of different variants isolated from 3 HTLV-1 infected patients and 2 STLV-1 naturally infected Celebes macaques. Sequences are aligned with the dominant viral genotype found in the 3 HTLV-1 infected individuals. Dots indicate no change in amino acid and the asterisk denotes a stop codon. Numbers at the top represent the position in Env in reference to the ATK-1 sequence . Amino acids in bold refer to conserved positions found on the multiple alignments of available PTLV types. Amino acids in red refer to positions that remain conserved among our variants. Identical variants found in different hosts are indicated by an asterisk (*) on the right side of the sequence.