Morphogenesis of three pseudorabies virus strains in porcine nasal mucosa.

After intranasal inoculation of pseudorabies virus in 10-week-old pigs, the morphogenesis of three pseudorabies virus strains was studied in nasal mucosa. Virulent NIA-3 virus rapidly invaded the lamina propria of the nasal mucosa. NIA-3 nucleocapsids were enveloped at the nuclear membrane. Invasion of the lamina propria was delayed after intermediate virulent 2.4N3A virus infection or absent after nonvirulent Bartha virus infection. 2.4N3A virus was mainly enveloped by membranes of the smooth endoplasmic reticulum. Bartha virus replication was delayed for at least 24 h as compared with NIA-3 virus, and Bartha virus was also enveloped by membranes of the smooth endoplasmic reticulum. The virulence of 2.4N3A and Bartha virus may be diminished because of altered envelopment and delayed viral replication and release.