MET CALF 

 tance, physiological patterns of the host, or virus infectivity? 



This study was concerned with the initial stage of virus-cell 

 interaction using influenza virus with selected hosts as the experi- 

 mental model. The influence of low temperature upon the interaction 

 has been examined from the standpoint of its effect upon virus in- 

 fectivity. 



The proposal that neuraminidase facilitates the penetration of a 

 host cell by influenza virus presumes that infectious virus should 

 possess enzyme activity. This viewpoint has been presented by 

 Gottschalk (1957) who believes enzyme action renders cell wall 

 mucoproteins more permeable to virus and thereby facilitates 

 virus penetration of a host cell. 



This study began with the knowledge that experimental influenza 

 infections have been represented as occurring inthe absence of en- 

 zyme action (Fazekas, 1948; Fazekas and Graham, 1949), Without 

 adopting a position on the essentiality of enzyme to the infectious 

 process, it was reasoned that clues to the influence of cold upon vi- 

 rus infectivity might be gained by a consideration of the effect of 

 cold upon neuraminidase production by influenza virus. 



THE EFFECT OF COLD UPON THE NEURAMINIDASE ACTIVITY 

 OF INFLUENZA VIRUS 



Enzyme action was measured by two methods. The thiobarbituric 

 acid (TEA) method of Warren (19 59) was used to determine the free 

 neuraminic acid resulting from combination of virus and a neura- 

 minic acid containing substrate. A neuraminmucoid substrate was 

 prepared from oriental "edible birds nest" by a modification of the 

 method of Lawton et al. (1956), Edible birds nest is a salivary mu- 

 coid produced by the CoUocalia species of swift. The second method 

 included the use of ovomucin obtained from hens eggs (Gottschalk 

 and Lind, 1949) in an inhibitor reduction (IR) titration following com- 

 bination of virus and ovomucin (Isaacs and Edney, 1950). 



344 



