Inhibitory effect of biphalin and AZT on murine Friend leukemia virus infection in vitro

Biphalin is a bivalent opioid analogue containing two tyrosine residues, We have examined the effect of biphalin's anti-retroviral potency in vitro using a murine model. Biphalin, in non-cytotoxic concentrations, suppressed ina dose-dependent fashion the replication of Friend leukemia virus (FLV) in Mus dunni cells as determined using a focus forming assay. FLV replication was substantially reduced by biphalin at 10(-4) M concentration, When biphalin was combined with 3'-azido-3'-deoxythymidine (AZT) the two acted synergistically in inhibiting FLV replication compared to either used alone. Using a reverse transcriptase (RT) assay, FLV RT levels also were noted to be reduced in the presence of biphalin. These observations indicate that biphalin possesses anti-retroviral activity in vitro, suggesting that this opioid peptide should be examined further in vivo to determine if it is a candidate for combined therapy with AZT and possibly other drugs for retrovirus infections including the human immunodeficiency virus (HIV). (C) 1998 International Society for Immunopharmacology. Published by Elsevier Science Ltd.