Chapter I 

 The Problems of Virology 



F. M. Burnet and W. M. Stanley 



Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, 



Australia 



and 



Virus Laboratory, University of California, Berkeley, California 



I. Introduction 1 



II. The Double Approach 2 



A. The Infective Particle 2 



B. The Virus-Host Cell Relationship 8 



References 14 



I. Introduction 



The present work was designed to provide a relatively comprehensive 

 account of current knowledge of viruses regarded, not as agents of disease, 

 but as biological entities whose properties can be studied in the laboratory 

 by the methods of exjDerimental biochemistry, biology, and biophysics. We 

 have interpreted this as broadly limiting our topics to the chemical, physical 

 and, where relevant, genetic structure of the infective units and to what is 

 known of the interaction between virus and the cell it infects. Except where 

 it is necessary to allow definition of some intrinsic quality of a virus, no con- 

 sideration is given to the pathogenesis of virus diseases nor to clinical, 

 epidemiological, or ecological asj^ects of such diseases. 



Even with this limitation, the field to be covered is enormous and peculi- 

 arly difficult to organize satisfactorily. The first difficulty concerns the range 

 and diversity of viruses. If we confine attention to the infective form, we 

 have miits ranging in complexity from a relatively simple system of asso- 

 ciation between two types of macromolecule (tobacco mosaic virus) to large 

 units of complex composition which are more nearly like organisms (vaccmia 

 and psittacosis viruses). Some, such as the smaller plant and animal viruses, 

 possess ENA (ribonucleic acid) only, the bacterial viruses contain DNA 

 (deoxyribonucleic acid) in one group of a unique chemical structure, and 

 some of the larger animal viruses may be found to contain both tyjjes of 

 nucleic acid. No direct evidence can be obtained of the ways by which 

 viruses have evolved. It is doubtful whether any biologist would even suggest 

 that all types of virus had a remote common ancestor. Many have suggested, 

 on the other hand, that among the viruses we include a widely heterogeneous 

 group of many different evolutionary origins, the single common feature 



1 



