Alignment of amino acid sequences of Envelope (Env) proteins of BLV isolates. Amino acid residues corresponding to gp51 (SU) and gp30 (TM) proteins are shown on the top of the alignment. Leader peptide of SU is shown in green. Structural strong turn motif GYPD is shown in bold, italics and double underlined. Conformational epitope region is indicated on top of the alignment. Linear epitopes are shown in italics and underlined [41, 42]. Receptor-binding domain (RBD)  residues are delimited by two triangles. Second strong turn, SSSG, is shown in bold and italics. Amino acids involved in neutralization domains are shown in yellow. CD8 + −T epitope is shown in red. SU transmembrane hydrophobic region (TMHR) is shown in light blue. TM fusion peptide is shown in light grey and residues believed to span host cell membranes are indicated double lined. BLV leash and α-helical region (LHR)  is shown in bold, italics and underlined. Epitope GD21 is shown in magenta. TM membrane-spanning region is shown in bold and italics. The cytoplasmic domain is indicated on top of the alignment. The rest is the same as in Figure 1.