Vasoactive intestinal peptide 1-12: a ligand for the CD4 (T4)/human immunodeficiency virus receptor.

A five-amino-acid (TDNYT) sequence of vasoactive intestinal polypeptide (VIP) shares homology with the proposed attachment sequences of the human immunodeficiency virus (HIV). Synthetic peptides with these sequences have previously been shown to block viral envelope (gp120) binding and HIV infectivity and to serve as agonists of the CD4 (or T4) receptor. Utilizing an in vitro human monocyte chemotaxis bioassay we examined novel synthetic VIP and gp120 sequences and characterized their pharmacological activities on monocyte chemotaxis. CD4 receptor activity is primarily specified by N-terminal (VIP [1-12]) amino acids. The profound immunosuppression of AIDS is not easily explained solely by virus infection. Recently described immunological functions of VIP are similar to some of the immunological abnormalities shown by patients with AIDS. An overproduction of a VIP-like molecule from viral sources (e.g. gp120) could explain some of the immune system impairments which have been described in AIDS.