GP38 peptide corresponds to aa 578-603 of HIV-2 gp160 envelope glycoprotein. GP38 includes the 17-amino acid long immunosuppressive region present in many retroviral envelope proteins. Peptides derived from this sequence inhibit immune function. GP38 antibodies are found in plasma of HIV-infected patient.H-Arg-Val-Thr-Ala-Ile-Glu-Lys-Tyr-Leu-Gln-Asp-Gln-Ala-Arg-Leu-Asn-Ser-Trp-Gly-Cys-Ala-Phe-Arg-Gln-Val-Cys-OH (Cys20-Cys26) or H-RVTAIEKYLQDQARLNSWGCAFRQVC-OH (Cys20-Cys26)