INTERFERENCE BETWEEN ANIMAL-PATHOGENIC VIRUSES 



R. W. SCHLESINGER 



The Public Health Research Institute 

 of the City of New York, Inc. 



It has become general practice to classify as interference phenom- 

 ena all instances in which exposure to one of a pair of viruses renders 

 a host refractory to the disease-producing effects of the other or unable 

 to support its multiplication, and in which this acquired refractoriness 

 cannot be readily explained as due to conventional specific immune 

 reactions. According to this broad criterion, i.e. without regard for 

 possible diversities in the underlying mechanisms, one can say that 

 mutual interference between animal-pathogenic viruses is (a) not de- 

 pendent upon immunological or even obvious biological relationship be- 

 tween the two viruses involved, and (b) not restricted, as is "mutual 

 exclusion" between phage strains (Delbriick and Luria, 1942), to un- 

 related combinations. Henle has just written an exhaustive review of 

 the entire subject (Henle, W. 1950), in which he emphasizes the vary- 

 ing degrees of relationship between viruses which do or do not interfere 

 with each other. In this paper, an attempt will be made to reduce the 

 problem to the level of the single infected cell and to form the basis for 

 further discussion in which some analogies and some contrasts to the 

 phage-bacteriimi system might be brought out. Such a limitation in 

 scope calls for the following reservations: 



(a) "Interference" between immunologically related viruses may 

 be due to specific immune mechanisms, provided, of course, the animal 

 host is capable of antibody production. Recent findings on the rapidity 

 and efficacy of local antibody response, stimulated in immunized ani- 

 mals by the antigenic "booster" of the challenge dose (Schlesinger, 

 1949a), suggest the possibility that a specific immune response might 

 play a role even in those cases in which the "interfering" dose had not 

 led to the production of measurable antibody by the time the related 

 challenge dose was given. The interpretation of such observations, 

 i.e. the choice between interference and specific immunity, should be 

 based on determination of the additive antigenic effect of the two doses. 

 Obviously this reservation does not apply in instances of interference 

 between immunologically related viruses which have been studied in 

 hosts incapable of antibody production, i.e. the embryonated egg or 

 embryonic tissue culture media. 



(b) Interference has been observed in a variety of extremely dis- 

 similar host- virus systems (see Henle, W. 1950), and it is not always 

 known what cells are infected by the viruses. If the cells are identified. 



