Inhibition of viral hemagglutination by aggregated orosomucoid

Abstract

The aggregation of orosomucoid by heating at 80 °, and its resultant capacity to inhibit viral hemagglutination by PR8 influenza virus has been studied. Heating orosomucoid in unbuffered saline resulted in a polydisperse aggregate. Fractionation of such preparations on Sephadex G-200 resulted in a separation into three components. The capacity to inhibit viral hemagglutination was associated only with protein eluting with the void volume on this grade of Sephadex. Aggregation by heating was found to be most pronounced at pH values close to 3.8, when the aggregate appeared essentially monodisperse in the ultracentrifuge with a sedimentation constant S 20, w = 30.1 S. The product formed was a potent inhibitor of viral hemagglutination, and 6.0 × 10 -3 μg inhibited 4HA units of PR8 indicator virus. No aggregation of orosomucoid occurred on heating at neutral or slightly basic pH. and little aggregation occurred below pH 2.6. Treatment of heat-aggregated orosomucoid with 8 m urea caused disaggregation of the high molecular weight material and a loss of its inhibitor capacity. The inhibitory activity of the aggregate was destroyed by treatment with neuraminidase or sodium periodate.