Alkaline Degradation of Polyoma Virus

Purified polyoma virus particles were degraded by exposure to carbonate + bicarbonate buffer, pH 10.5, at relatively low ionic strengths. The degradation was less when higher ionic strengths of the buffer were employed, i.e. 0.3 to 0.5m carbonate buffer. The degradation products were separated by caesium chloride density-gradient centrifugation and studied by infectivity, haemagglutination assays, and by electron microscopy. Electron microscopy demonstrated that treatment at pH 10.5 produced various stages of degradation, each stage dependent upon the ionic strength of the carbonate + bicarbonate solution. Polyoma particles were swollen when buffer of low ionic strength was used and, in addition, this swollen state allowed penetration of DNase. At slightly higher ionic strengths (0.1m-carbonate + bicarbonate buffer) the virus DNA was released from the polyoma virus coat and easily banded on caesium chloride gradients.