Production of plaques with influenza viruses.

Abstract

THE demonstration of the production of plaques, that is, necrotic foci, in tissue culture with the viruses of Eastern equine encephalomyelitis1, Western equine encephalomyelitis2, Newcastle disease2, vaccinia3, and poliomyelitis4, offers additional quantitative applications to the study of these viruses. A necessary condition for the development of a plaque in tissue culture has been shown to be a destructive activity of the virus on the tissue employed. With the demonstration of a highly destructive effect of the WSE strain of influenza A virus on various chick embryonic tissues (9-day chorio-allantoic membrane, and 14-day lung and liver in roller tube cultures, unpublished results), experiments were undertaken to show production of plaques with this virus. Using the technique of Noyes3, plaques averaging 0.5 mm. in diameter were obtained in five days on chick embryonic layer tissue cultures with a high dilution of the allantoic fluids used. Attention was then directed to a less heterogeneous source of tissue, chick embryo lung. Plaque formation was shown to occur readily with this tissue not only with the WSE strain of influenza A virus, but also with the other influenza virus strains tested.