The role of carboxy-terminal portion of beta subunit of human chorionic gonadotropin in human immunodeficiency virus infection.

Human chorionic gonadotropin (hCG) and the beta subunit of this dimer glycoprotein hormone (beta hCG) have been reported by us to inhibit HIV replication. In order to identify the active site responsible for the antiviral activity, twelve overlapping peptides spanning across beta hCG were examined for their effect against HIV-caused cell death. Although the NH2-terminus of beta hCG appeared to contribute to activity, the core region was biologically inert. The most potent activity was observed with the fragment representing the carboxy-terminus of beta hCG. The dose response curve to serial dilutions of the peptide, containing amino acid residues 106-145, had a bell-shaped appearance - characteristic of hCG and beta hCG. The peak of activity corresponded to 100 ng/ml - the dose at which two thirds of virus-exposed MT-4 T lymphocytes survived. None of the tested peptides were toxic to MT-4. While the mechanism of action remains unclear, the results suggest that the COOH-terminal portion, unique to beta hCG, confers anti-HIV activity.