Inactivation with Fast Charged Particles of Infectivity and Hemagglutination in Influenza A Virus

There are several techniques available for the study of viral morphology. Most of these techniques, such as electron microscopy, hydrodynamic studies, and light scattering, reveal only the over-all form of the elementary body or fragments thereof; they cannot tell us whether or not the entire particle under study is necessary for any particular viral function. Radiation inactivation studies, on the other hand, can give information on this point. In addition, they provide evidence concerning the internal morphology of the virus without actually disrupting the elementary body (1). This paper reports studies of the infectivity and hemagglutination of two strains of influenza A virus. Solutions of the virus were dried in thin layers and bombarded in vacuum with fast charged particles. Such particles have essentially straight-line tracks when passing through thin layers of organic material, and their energy release is statistically predictable. It is possible, therefore, to determine the size, shape, and multiplicity of the structural entity responsible for a certain property by observing the manner in which the virus loses this property under irradiation. Dry samples of virus were used in order to avoid indirect effects of irradiation caused by the production of inactivating substances in the medium surrounding the virus. Such indirect effects make it difficult to interpret radiation effects in terms of a specific target for inactivation. The technique of bombardment has been described by Pollard (2). Studies similar to those being reported in this paper have been made on Newcastle disease virus by Woese and Pollard (3). These references should be consulted for a more thorough discussion of principles and techniques.