HEMAGGLUTINATION BY ANIMAL VIRUSES 31 



with relatively large amounts of NDV at 37°C, they rapidly stabilize and 

 are found to have lost all power to absorb or be agglutinated by NDV or 

 mumps virus. They have, however, two new qualities — they agglutinate 

 fresh red cells and they are agglutinated by specific antiviral serum and by a 

 proportion of sera from human cases of infectious mononucleosis (Anderson, 

 1947a; Burnet and Anderson, 1946). Both these properties are resistant to 

 treatment with RDE and appear to be due to an irreversible union of a pro- 

 portion of the virus particles with the cell surface. 



In support of this view, the following points may be cited:(l) the reaction 

 does not occur with cells treated with RDE before being exposed to virus; 

 (2) treated cells will not only agglutinate fresh cells but will progressively 

 destroy receptors on these; (3) Burnet and Mitchell found that cells showing 

 the typical reactions after treatment with NDV could be prepared for 

 electron microscopy and then showed the presence of typical virus particles 

 on the cell surface. 



Mumps virus behaves similarly but the reactions are more difficult to 

 demonstrate than with NDV (Burnet, 1946; Lind, 1948). Mumps and NDV, 

 again unlike the influenza viruses, are hemolytic (Morgan et at., 1948; 

 Kilham, 1949). The conditions for hemolysis are complex, but one feature 

 noted with NDV is that the reaction only takes place at temperatures above 

 24°C. (human cells) or 28°C. (fowl cells) (Burnet, 1950). Hemolytic action is 

 more readily inhibited or destroyed by heat and ultraviolet irradiation than 

 is hemagglutinin (Chu and Morgan, 1950b), and Gardner and Morgan (1952) 

 found that the hemagglutinin and hemolysin of mumps were differently 

 affected by certain inhibitors of enzymes. The same cell receptors, however, 

 seem to be necessary, and all authors agree that the hemolysin is, or is 

 carried by, the virus particle itself (Beveridge and Lind, 1946; Morgan 

 et al, 1948). 



From what has been said, it will be seen that NDV, and possibly mumps, 

 have two groups of actions on red cells. The first corresponds to hemag- 

 glutination and stabilization by active influenza viruses; the responsible 

 agents are stable to 56°C, and act at all temperatures in the range 4 to 

 37°C. 



The second group comprises production of agglutinin on stable cells, cell 

 sensitization, increase of hemagglutinin titer at 37°C. on repeated shaking, 

 hemolysis, and an undue reduction of electrophoretic mobility. These actions 

 may or may not depend on one mechanism. The agent or agents in virus 

 responsible for hemolysis are destroyed at 54°C. and act on red cells only 

 above 28°C. (fowl cells) or 24°C. (human cells). We may, for convenience, 

 denote this group of actions as "binding" actions, in contrast to elution, and 

 perhaps compare them with the "binding" action of indicator viruses on red 

 cells at 37°C. (Section 1, E). 



