Replication of swine and equine influenza viruses in canine kidney cells

Both swine and equine influenza viruses were replicated in Madin-Darby canine kidney cells. Hemagglutinin and complement-fixing antigens were synthesized at 4 to 8 hours postinfection and reached maximal synthesis at 16 to 20 hours. Neuraminidase activity increased 9- to 11-fold; 50% of the total hemagglutinin antigen was made before the infective virus progeny was detected.