| The gamma134.5 protein has been demonstrated to be a neurovirulence factor contributing to HSV virulence in experimental animals. The ability of the gamma134.5 protein to suppress the PKR response plays a crucial role in HSV pathogenesis. Accumulating evidences suggest the gamma134.5 protein is a multi-functional protein. However, it remain unsolved how these functions contribute to virulence.;Recently, we developed a novel system to study the functions of the gamma 134.5 protein, in which the gamma134.5 gene in HSV-1 genome is replaced by the NS1(non-structural protein 1) gene, an IFN antagonist of influenza A virus. Based on this model system, we can separate the anti-PKR activity of the gamma134.5 protein from its other functions. Further, from the electron microscopy studies, we demonstrated that the gamma 134.5 protein is involved in facilitating viral egress in MEF 3T6 cells, including nuclear and cytoplasmic egress. Deletion analysis showed that loss of 1-30aa of the gamma134.5 protein led to a delay or block in virus budding from nucleus to cytoplasm, and further deletions of 30-72aa or 72-106aa exerted a defect in egress from the cytoplasm to the cell surface when compared to the wild type virus.;In addition to the neurovirulence, neuroinvasiveness is also an important parameter in pathogenic study. As a unique feature of the gamma134.5 protein encoded by HSV-1, the number of triplet repeats varies among different strains. However, the precise role of the triplet repeats in pathogenesis has not been established. Hence, in this work, we characterized the role of triplet repeats in gamma134.5 protein during HSV-1 infection. Deletions of triplet repeats from ten in HSV-1(F) to three or zero in the gamma 134.5 protein have no effect on viral response to interferon. However, in mouse 3T6 cells, these mutants replicate with delayed growth kinetics. This decrease in growth, as compared to wild-type HSV-1(F), does not result from viral failure to suppress the PKR response but rather a delay in virus release or egress. These results indicate that deletions in the central domain of the gamma134.5 protein impair virus egress but not viral response to interferon. |
