Identification and mapping of functional domains on human T-cell lymphotropic virus type 1 envelope proteins by using synthetic peptides

To identify the regions that are important in human T-cell leukemia virus type 1 (HTLV-1) envelope function, we synthesized 23 kinds of peptides covering the envelope proteins and examined the inhibitory effect of each peptide on syncytium formation induced by HTLV-1-bearing cells, Of the 23 synthetic peptides, 2, corresponding to amino acids 197 to 216 on gp46 and 400 to 429 on gp21, inhibited syncytium formation induced by HTLV-l-bearing cells but did not affect syncytium formation induced by human immunodeficiency virus type 1-producing cells, The peptide concentrations giving 50% inhibition of syncytium formation for gp 16 197 to 216 and gp21 400 to 429 were 14.9 and 6.0 mu M, respectively. A syncytium formation assay with overlapping synthetic peptides containing amino acids 175 to 236 and 391 to 438 of the envelope proteins showed that syncytium formation was inhibited by peptides that contained the amino acid sequences 197 to 205 (Asp-His-Ile-Leu-Glu-Pro Ser-Ile-Pro) and 397 to 406 (Gln Glu-Gln-Cys-Arg-Phe Fro-Asn-Ile-Thr) These observations suggest that the two regions corresponding to amino acids 197 to 216 and 400 to 429 are involved in HTLV-1 envelope function.