Chapter VII 



Interference between Animal Viruses 



R. Walter Schlesinger 

 Saint Louis University School of Medicine, Saint Louis, Missouri 



I. Introduction 157 



II. Definition of the Problem 158 



A. Qualitative Criteria for a Definition of Interference 158 



1. The Relation to Virulence 158 



2. Mutual Exclusion and Nonspecific Inhibition of Viral "Toxicity" 159 



B. Criteria for Quantitative Analysis 160 



III. Experimental Systems 161 



A. Demonstration of Interference in Mammalian and Avian Hosts 161 



1 . Heterologous Viruses 161 



2. Homologous Viruses 166 



3. Interfering Capacity of Inactivated Viruses 170 



4. The Role of Timing and Dosage 170 



5. Localized Character 1 72 



B. Interference among Members of the Myxovirus Group in the Allantoic 

 Membrane of Chick Embryos (CAM) 173 



1. Heterology and Homology among Myxoviruses 173 



2. Interference and Mixed Infection with Two Active Myxoviruses 174 



3. Interference and Genetic Interaction between Inactivated and Active 



Myxoviruses 175 



4. Autointerference and the Genesis of " Incomplete " Influenza Virus. 178 



5. Interfering Capacity of "Incomplete" Virus 179 



C. Demonstration of Interference in Tissue Culture 181 



1. Interference in Surviving Tissue Fragments 181 



2. Interference in Growing Cell Cultures 181 



IV. Dynamics of Interference — Summary 182 



A. Qualitative Criteria — Specificity of Induction 182 



B. Quantitative Criteria ] 84 



1. Number of Interfering Particles per Cell 184 



2. Speed and Duration of Interference 184 



3. Efficiency — "Overcoming" of Interference 185 



V. Mechanisms of Interference 185 



A. Nature of Association of Interfering Virus and Cell 186 



B. Fate of the Superinfecting Virus 187 



C. Perspectives 189 



References 189 



I. Introduction 



Immunity to animal viruses is a peculiarly complex problem. More than 

 any other phase of viral activity, it reflects the double standard of reference 



157 



