Bovine herpesvirus 1 UsORF8 protein induces apoptosis in infected cells and facilitates virus egress

The bovine herpesvirus 1 (BHV-1)U-s ORF8 protein with homology to the Us9 protein of other alphaherpesviruses induces apoptosis in rabbit kidney (RK13) cells without the presence of other BHV-1-encoded proteins. In this article, we have characterized the cytotoxicity and growth behavior of a BHV-1 recombinant, BHV-1/D8 which fails to express the U-s ORF8 protein in infected cells. BHV-1/D8 exhibited a reduced cytotoxicity to RK13 cells when compared to the cytotoxicity of control BHV-1 strains. In RK13 cells, the onset of apoptosis was not observed during the infection with BHV-1/D8, and the virus multiplication of BHV-1/D8 was markedly greater than that of control viruses. However, virus release of progeny viruses from the infected RK13 cells into culture supernatant was significantly decreased by the loss of the U-s ORF8 protein. These data demonstrate that the U-s ORF8 protein activates the apoptotic process and facilitates virus release from the BHV-1-infected cells. (C) 2002 Elsevier Science (USA).