Synthesis and specific influenza A virus-adsorptive functionality of alkyl curdlan sulfate-coated membrane filter

Abstract

To develop a biomaterial with an influenza virus-adsorptive functionality, an alkyl curdlan sulfate was prepared by ionic interaction between a positively charged didodecyldimethyl ammonium bromide and a negatively charged sulfate group of curdlan sulfate, which has potent anti-HIV activity, and then it was coated on a membrane filter with a 1-μm pore size by hydrophobic interaction with the long alkyl groups in the curdlan sulfate. The alkyl curdlan sulfate with the degree of alkylation (DOA) of 0.03 (one didodecyldimethyl group/12 sugar residues with 36 hydroxyl or sulfate groups) showed potent anti-HIV activity in a 50% effective concentration (EC 50 ) as low as 0.87 μg/mL (standard curdlan sulfate EC 50 = 0.3 μg/mL), and the activity decreased with increasing DOA. A DOA higher than 0.1 (one didodecyldimethyl group/three sugar residues with nine hydroxyl or sulfate groups) gave no anti-HIV activity. Although both curdlan sulfate and alkyl curdlan sulfates did not inhibited infection of Madin-Darby canine kidney cells by influenza viruses, the alkyl curdlan sulfate-coated membrane filter was found to have a specific adsorptive functionality for influenza A virus in vitro. When 1.6 mg of the alkyl curdlan sulfate with the DOA of 0.03 was coated on a membrane filter (φ13 mm; pore size, 1 μm), three stacked alkyl curdlan sulfate-coated membrane filters dramatically decreased hemagglutination to 1/4-1/32. However, the membrane filter did not effectively remove on influenza B viruses, and thus a membrane filter without alkyl curdlan sulfate was not effective against influenza viruses. These results can therefore be presumed to demonstrate that the alkyl curdlan sulfate-coated membrane filter removed influenza A viruses by adsorption between the negatively charged sulfate groups and the positively charged envelope protein of the virus.