The influence of dextran sulfate on influenza A virus fusion with erythrocyte membranes.

Dextran sulfate suppresses the low pH-induced fusion of influenza virus A/Brazil 11/78 with erythrocyte membranes, as shown by fluorescence dequenching assay, using the fluorophore octadecylrhodamine B chloride (R18). Inhibition of fusion was maximal at pH 5.0, while at higher pH values (> 5.6) fusion was not affected. Hemolysis of intact red blood cells by influenza A virus at low pH values is also prevented by dextran sulfate. The inhibiting effect of the polymer is mainly ascribed to repression of virus attachment. Evidence is given that the conformational change of the virus envelope protein hemagglutinin (HA) responsible for triggering fusion is not affected by the polymer.