Antiviral agents with activity against human retroviruses

The ability of various known anti-HIV antivirals to inhibit four different strains of human immunodeficiency virus type 1 (HIV-1), a strain of type 2 (HIV-2), and a human T-cell lymphotropic virus type I (HTLV-I) was tested. The tested substances included two sulfated polysaccharides (lentinan sulfate and dextran sulfate) and a nonsulfated polysaccharide PSK, E-P-LEM, glycyrrhizin sulfate, and nucleoside analogues (AZT and DHT). The effects of the substances were measured quantitatively with two different assays: (i) inhibition of cell-free viral infection and (ii) inhibition of the fusion reaction induced by cell-to-cell infection. The results showed that cell-free infection of HIV-1 and HIV-2 was almost completely blocked in the presence of all of the substances tested. However, cell-to-cell infection by HIV-1, HIV-2, and HTLV-I was inhibited only by the polysaccharides, E-P-LEM, and glycyrrhizin sulfate but not by the two nucleoside analogues. Moreover, the extent of inhibition of the fusion reaction by the substances varied significantly from strain to strain in HIV-1.