| Bovine herpesvirus-1 (BHV-1), pseudorabies (PrV), and equine herpesvirus-1 (EHV-1) are three herpesviruses of veterinary importance. All three viruses down-regulate cell surface expression of major histocompatibility complex (MHC) class I molecules, in vitro. Previous studies have shown that interference with transporter associated with antigen processing (TAP) is one of the mechanisms of class I down-regulation by two of these viruses (BHV-1 & PrV). The objectives of this study were to extend these findings to further characterize mechanisms of class I down-regulation by these viruses, and to identify the vial proteins responsible.; BHV-1 protein(s) responsible for TAP inhibition could be immunoprecipitated with the bovine TAP complex from infected cells. Lack of an antibody to, and low expression of, bovine TAP complex in epithelial cells hamper this approach. As the first step to overcome this problem, we have cloned, sequenced and characterized bovine TAP2.; Virion host shutoff (vhs) activity of BHV-1 partially contributes to down-regulation of class I expression. In order to investigate whether this is true with PrV, we generated two PrV vhs gene deletion mutants. Both vhs mutants interfered with TAP activity and down-regulated expression of class I, indicating that inhibition of TAP function in PrV-infected cells is due to mechanism(s) specifically directed at class I pathway.; Our studies with EHV-1 have revealed that this virus also interferes with TAP function. Furthermore, as with BHV-1 and PrV, an early protein(s) of EHV-1 inhibit(s) TAP function.; In order to identify the PrV protein responsible for TAP inhibition, we have constructed a PrV-bacterial artificial chromosome transposon mutant library. Screening of this library should lead to identification of PrV proteins responsible for TAP inhibition.; These studies shed light on the mechanisms of down-regulation of class I expression by these viruses. Furthermore, this dissertation research should expedite identification of the early protein(s) of BHV-1, PrV, and EHV-1 that mediate class I down-regulation. |
