Comparison of predicted accessory protein sequences of selected primate T-cell lymphotropic viruses. Upper alignment, HTLV-4(1863LE) open reading frame (ORF) IV compared to HTLV-1 (p13II), STLV-2 ORFII, HTLV-3(2026ND) ORFIV, and HTLV-2 p28XII. Location of conserved mitochondrial targeting sequence in the HTLV-1 p13II protein and highly conserved amino acid region are boxed. Lower alignment, HTLV-4(1863LE) ORFV compared to HTLV-2 ORFII (p28XII). % Sim, percent amino acid similarity of HTLV-4 ORFs to other PTLV ORFs.