Radiation Studies on the Infective Property of Newcastle Disease Virus

Abstract

In this paper we examine the fact that there is a differential sensitivity of some viruses in that the infectious property is associated with a sensitive portion which is less than the whole virus, as demonstrated by employing bombardment of varied energy releases, including the use of slow electrons which can penetrate to varying small depths. The results are consistent with the presence of an insensitive coat on the outside of a sensitive region. The development tissue-culture plaque-counting technique by Dulbecco and Vogt has made it possible to perform experiments with animal viruses with an accuracy comparable to that obtained with bacterial viruses. By this technique, the NK strain of Newcastle disease virus was bombarded by fast protons, deuterons, and a-particles, and also by slow electrons of varying penetrability. Irradiation was carried out in the dry state to guarantee that diffusion of the inactivating agents did not take place. This permits reasonable deductions to be made about the size and shape of the sensitive regions. The inactivation of the infective property in Newcastle disease virus (NDV) was studied with fast charged particles and slow electrons. The results of proteon, deuteron, and a-particle bombardment of NDV indicate that the total radius of the virus is at least 510 A, and that the virus possesses a spherical radiation-sensitive region 280 A in radius. The results of slow electron bombardment of NDV show that the radiation-sensitive region is surrounded by a radiation insensitive coat 230 A thick.