Abstract
Some cytopathic changes in L cells infected with the HA+ and HA- viruses and with mixture of both viruses were examined. The following results were obtained.
(1) The HA+ virus produced cell clumping and hemadsorption of fowl red blood cells around the infected cells, whereas the HA- virus produced polynucleated giant cells without hemadsorption.
(2) The production of hemagglutinin in cells infected with the HA+ virus first became appreciable 10 hours after infection and a parallelism was found between the growth of virus and the production of hemagglutinin. The cells infected with the heat and UV-treated HA+ virus showed no hemagglutinin production. Inhibition of the production of hemagglutinin by actinomycin and puromycin indicates that viral DNA-dependent RNA and protein synthesis are indispensable for the production of hemagglutinin.
(3) The HA+ virus produced cell clumping whereas the HA- virus produced polynucleated giant cells 6 hours after infection and their formation depended on multiplicity of viruses. The formation of polynucleated giant cells was not affected by mitomycin C and actinomycin but inhibited by puromycin. Although the heat-treated viruses produced no morphological changes in their host cells, the UV-irradiated HA+ and HA- viruses produced cell clumping and polynucleated giant cells respectively.
(4) The fact that dual infection with both HA+ and HA- viruses produced cell clumping but no polynucleated giant cells indicates that the changes produced by the HA+ virus were dominant.
