Antiviral activity of chondroitin sulphate E targeting dengue virus envelope protein.

Sulphated glycosaminoglycans such as heparin inhibit the early step of dengue virus infection through interaction with envelope (E) protein. Here, we found that chondroitin sulphate E (CSE), but not CSD, which contains the same degree of sulphation, inhibited dengue virus (DENV) infection of cells with adsorption. CSE significantly reduced infectivity of all dengue virus serotypes to BHK-21 and Vero cells. DENV preferentially bound to CSE immobilised on plastic plates. Also, virus binding to CSE or heparin was cross-inhibited by soluble CSE or heparin. These findings suggested that common carbohydrate determinants on CSE and heparin could be essential epitopes for interaction of DENV, and may be responsible for inhibition of the early steps of DENV infection. A recombinant E protein directly bound heparin and CSE, but not CSD, meaning that interaction of CSE with E protein contributes to the inhibitory action of this glycosaminoglycan. These observations indicate that a specific carbohydrate structure rather than polysulphation or addition of negative charges of the glycosaminoglycan molecule would be necessary for direct binding to DENV E protein. In conclusion, CSE showed antiviral activity as an entry inhibitor targeting E protein of dengue virus.

Structure and anti-dengue virus activity of sulfated polysaccharide from a marine alga.

A sulfated polysaccharide, named fucoidan, from the marine alga Cladosiphon okamuranus is comprised of carbohydrate units containing glucuronic acid and sulfated fucose residues. Here we found this compound potently inhibits dengue virus type 2 (DEN2) infection. Viral infection was inhibited when DEN2, but not other serotypes, was pretreated with fucoidan. A carboxy-reduced fucoidan derivative in which glucuronic acid was converted to glucose did not inhibit viral infection. Elimination of the sulfated function group from fucoidan significantly attenuated the inhibitory activity on DEN2 infection with <1% fucoidan. DEN2 particles bound exclusively to fucoidan, indicating that fucoidan interacts directly with envelope glycoprotein (EGP) on DEN2. Structure-based analysis suggested that Arg323 of DEN2 EGP, which is conformationally proximal to one of the putative heparin binding residues, Lys310, is critical for the interaction with fucoidan. In conclusion, both the sulfated group and glucuronic acid of fucoidan account for the inhibition of DEN2 infection.