Intranuclear inclusions in cells infected with Newcastle disease virus.

Cells infected by Newcastle Disease Virus were observed to contain both intracytoplasmic and intranuclear inclusion bodies. Ultrastructurally, they consisted of twisted strands of about 18-20 nm diameter resembling nucleocapsids. The presence of these inclusions was detected irrespective of host cell or pathogenicity of the virus. In immunofluorescence and immunogold labelling experiments, these structures were tagged by an anti-P protein monoclonal antibody. In summary, we show that intracytoplasmic and intranuclear inclusion bodies, hitherto used as a taxonomic characteristic for the genus Morbillivirus of the Paramyxoviridae, also occur in a member of the genus Rubulavirus.