DNA Strand Breakage and Biological Functions of Human Adenovirus after Gamma Irradiation

Human adenovirus type 2 was irradiated with gamma rays and the radio-sensitivity of several viral functions was determined and correlated with the damages in the viral DNA. The D₃₇ for plaque formation, inclusion body formation, and inhibition of cell cloning was found to be 0.46, 0.54, and 0.75× 106 rads, respectively. Radiation induced 0.5 single-strand breaks and 0.01 double-strand breaks per rad per 1012 daltons in the viral DNA. For the adsorbed virus, an average of 8.1 single-strand breaks and 0.16 double-strand breaks were induced in the viral DNA per inactivation of the plaque-forming ability. This suggested that the single-strand breaks may be repaired. No rejoining of broken DNA molecules could be detected after infecting cells with the irradiated virus at high multiplicity of infection. On the contrary, additional single-strand nicks were detected after infecting a host cell.