Virus-binding activity of fibronectin: masking of hepatitis A virus

Human plasma fibronectin interacts with viruses. When fibronectin-containing human sera negative for antibodies to hepatitis A virus (HAV) were added to suspensions of HAV, radioimmunological detection of HAV was reduced. This masking effect seemed to depend on the fibronectin concentration of the sera: plasma fibronectin purified by cryoprecipitation and affinity chromatography showed a masking effect on purified HAV which was dependent on the concentrations of fibronectin and HAV. Fibronectin peptides were obtained by subtilisin digestion: the non-collagen-binding regions of the fibronectin molecule were involved in the binding of HAV. We conclude that fibronectin has a virus-binding activity which interferes with radioimmunological methods for virus detection, and may contribute to the frequent transmission of hepatitis viruses by blood products enriched in fibronectin.