3, 1986 titled HTLV-III Envelope Peptides, inventors Gallo et al., now U.S. Pat. No. 4,772,547.DESCRIPTION OF THE INVENTIONThe peptides of the present invention can be represented by the following formula:W-X-Ala-Arg-Ile-Leu-Ala-Val-Glu-Arg-Tyr-Leu-Lys-Asp-Gln-Gln-Leu-Leu-Gly-Ile -Trp-Gly-Cys-Ser-Gly-Lys-Leu-Ile-Cys-Thr-Thr-Ala-Val-Y-Zwhere W is H-, Cys- or Tyr-, X is a bond or a sub-sequence of o