Inhibitory effect of tachyplesin I on the proliferation of human immunodeficiency virus in vitro.

An antimicrobial peptide, tachyplesin I, isolated from hemocytes of the Japanese horseshoe crab (Tachypleus tridentatus) was examined for its inhibitory effects on human immunodeficiency virus (HIV) infection in vitro. At a concentration of 7.5 micrograms/ml, tachyplesin I suppressed the development of cytopathic effects (CPE) by more than 70% in MT-4 cells infected with HIV (lymphadenopathy-associated virus). This inhibitory effect was observed only when the drug was added during the adsorption period of the virus to the cells. In cocultures of MOLT-4 and persistently HIV-infected cells (MOLT-4/HIV), tachyplesin I at the same concentration completely inhibited multinucleated giant cell formation. Infectivity of HIV was reduced by 10(-2.5) in medium free from fetal calf serum containing tachyplesin I at a concentration of 200 micrograms/ml. Tachyplesin I did not show any inhibitory effect on reverse transcriptase activity of HIV at concentrations of 9-80 micrograms/ml at which tachyplesin I inhibited HIV infection. These results suggest that the anti-HIV action of tachyplesin I was due to the inhibition of virus adsorption.