HEMAGGLUTINATION BY ANIMAL VIRUSES 43 



The infective virus followed the hemagglutinin onto and off red cells and 

 the ratios of hemagglutinin to infectivity were fairly constant at different 

 stages of infection of the mouse. For these reasons it is believed that hemag- 

 glutination is a function of the infective virus particle (Lahelle and Ward, 

 1951; Morris, 1953). 



b. Nonspecific Inhibition. A nonspecific inhibitor is present in lipid-free 

 extracts from normal mouse brain and other organs (Fastier, 1950, 1951a), 

 and also in normal serum of mice, rats, guinea pigs, and rabbits. It can be 

 partly inactivated by trypsin (Morris, 1952). From human urine and chick 

 allantoic fluid a fairly pure inhibitor can be isolated which is heat stable, and 

 combines with the virus at 4°C. and elutes from it at 22°C. (Tamm and Tyrrell, 

 1954). It is electrophoretically distinct from the mucoid inhibitor of influenza. 



A mucopolysaccharide inhibitor of hemagglutinin and infectivity was 

 recovered from intestinal tissues of adult mice by Mandel and Racker (1953b). 

 Union between inhibitor and virus is probably determined by weak electro- 

 static forces and can be broken by reducing the concentration of electrolytes. 

 Both components — inhibitor and virus — are then recovered in an active 

 form (Mandel, 1957). There is a fecal enzyme of mice which destroys this 

 inhibitor (Mandel and Racker, 1953a). 



2. Other Strains 



Olitsky and Yager (1949) and Hallauer (1949) described the agglutination 

 of sheep cells at 4°C. by the EMC group of viruses — Columbia SK, Columbia 

 MM, encephalomyocarditis and Mengo encephalitis. They elute at 20°C, like 

 GD VII (Gard and Heller, 1951). Verlinde and de Baan (1949) stated that the 

 cells can be rendered inagglutinable by prior treatment with RDE of V. 

 cholerae. 



Goldneld et al. (1957) recently reported that some ECHO * viruses and 

 Coxsackie B3 agglutinate washed group human cells at room temperature. 

 The preliminary data suggest that the hemagglutinin is associated with the 

 infectious particle. In this, the human viruses resemble the murine enteric 

 virus, GD VII, and the EMC group. 



RDE has no demonstrable action on ECHO receptors, and apparently 

 receptors for ECHO viruses differ from those for myxoviruses. Further 

 studies in this field should be of very great interest. 



C. Pneumonia Virus of Mice (PVM) 



Pneumonia virus of mice (PVM) is generally latent in mouse lung, but may 

 produce clinical disease (Horsfall and Halm, 1940). It may be extracted in 

 saline, and in such a preparation is combined with tissue elements from the 



* Enteric cytopathogenic human orphan. 



