Cytological Studies of Newcastle Disease Virus (NDV) in HEp-2 Cells.

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Abstract
Summary HEp-2 coverslip cultures were infected with the CG strain of Newcastle disease virus and incubated at 32 °, 37 °, and 42 °C. Infected cultures contained infected mononucleate and multinucleate cells when stained at frequent intervals with hematoxylin and eosin, and acridine orange stains. It was found that fluorescein conjugated antibody stain demonstrated the presence of viral antigen in the nucleus and cytoplasm as early as 6 hours after infection in cultures incubated at 37° or 42°. At 32°, antigen was demonstrable 12 hours after infection. The nuclear fluorescence was transient, disappearing between 24 and 48 hours after infection. In H & E and acridine orange stained cover-slip cultures, infected cells could not be differentiated until 12 hours after infection. These stains revealed the presence of granules possibly containing RNA corresponding in position and size to those staining with fluorescent antibody in the perinuclear zone. Syncytia could be classified into 2 groups. They could differ in origin or be different stages of infection of one type. The cultures incubated at 37° and 42° could not be differentiated from each other. The appearance of viral antigen as detected with fluorescein labeled antibody and the cellular alterations appeared to be delayed by approximately 6 hours in infected cultures incubated at 32°. We are indebted to Dr. Charles N. Luttrell, Dr. Bernard Roizman, and Philip R. Roane for their counsel during experimentation and in preparation of this manuscript.