Acidic polysaccharides isolated from marine algae inhibit the early step of viral infection

We examined the effects of various acidic polysaccharides isolated from marine algae on the infection and replication of human immunodeficiency virus type-1 (HIV-1), hepatitis B virus (HBV), hepatitis C virus (HCV), and human T-cell leukemia virus type-1 (HTLV-1). It was found that sulfated fucan polysaccharides, ascophyllan, and two fucoidans derived from different sources significantly inhibited the early step of HIV-1 (R9 and JR-FL) infection, while they did not affect the late step. The alginate oligomer consisted of uronic acids and sulfated-galactan porphyran showed no significant inhibitory effects. In addition, ascophyllan and two fucoidans inhibited the early step of HBV infection in a dose-dependent manner. Furthermore, these polysaccharides inhibited the early step of HCV infection but had no inhibitory effects on HTLV-1 replication. To further examine the specificity of these polysaccharides in viral infections, we used vesicular stomatitis virus (VSV)-G-pseudotyped HIV-1 infection. Ascophyllan, the two fucoidans, and alginate oligomer also potently inhibited VSV-G-pseudotyped HIV-1 infection in HeLa cells. Taken together, these results suggest that the acidic polysaccharides used in this study are capable of inhibiting the early step of viral infections depending on the polysaccharides but not in a strict species-specific manner.