DELETION OF GLYCOPROTEIN GM OF PSEUDORABIES VIRUS RESULTS IN ATTENUATION FOR THE NATURAL HOST

Glycoprotein M (gM) is one of the very few nonessential glycoproteins conserved throughout the herpesvirus family. Despite this conservation little is known about its function in virus replication. To test for the importance of gM in vivo in a natural virus-host system, 6-week-ol d piglets were intranasally infected with a gM(-) mutant of the alphah erpesvirus pseudorabies virus (PrV). Following infection virus excreti on from the nasal mucosa was decreased ca. 100-fold compared to wild-t ype or revertant virus. Clinical signs were limited to transiently ele vated temperature, In contrast, animals infected by wild-type or rever tant virus exhibited high fever, severe respiratory symptoms and affli ction of the central nervous system. Prior infection with gM(-) PrV co nferred protection against challenge infection and animals mounted an antibody response against gM after wild-type virus infection. Thus, gM is important for efficient virus replication in vivo and deletion of gM may contribute to development of live attenuated, genetically marke d vaccines.