An Early Pseudorabies Virus Protein Down-Regulates Porcine MHC Class I Expression by Inhibition of Transporter Associated with Antigen Processing (TAP)

Abstract

The objectives of this study were to identify the mechanism(s) of pseudorabies virus (PrV)-induced down-regulation of porcine class I molecules and the viral protein(s) responsible for the effect. The ability of PrV to interfere with the peptide transport activity of TAP was determined by an in vitro transport assay. In this assay, porcine kidney (PK-15) cells were permeabilized with streptolysin-O and incubated with a library of 125I-labeled peptides having consensus motifs for glycosylation in the endoplasmic reticulum (ER). The efficiency of transport of peptides from the cytosol into the ER was determined by adsorbing the ER-glycosylated peptides onto Con A-coupled Sepharose beads. Dose-dependent inhibition of TAP activity was observed in PrV-infected PK-15 cells. This inhibition, which occurred as early as 2 h postinfection (h.p.i.), reached the maximum level by 6 h.p.i., indicating that TAP inhibition is one of the mechanisms by which PrV down-regulates porcine class I molecules. Infection of cells with PrV in the presence of metabolic inhibitors revealed that cycloheximide a protein synthesis inhibitor, but not phosphonoacetic acid a herpesvirus DNA synthesis inhibitor, could restore the cell surface expression of class I molecules, indicating that late proteins are not responsible for the down-regulation. Infection in the presence of cycloheximide followed by actinomycin-D, which results in accumulation of the immediate-early protein, failed to down-regulate class I, indicating that one or more early proteins are responsible for the down-regulation of class I molecules.

Molecular mechanisms of HLA class I antigen abnormalities following viral infection and transformation

“…43 In addition, several other viruses, such as the bovine herpesvirus-1, pseudorabies virus and the murine g-herpesvirus 68 (MHV-68), are able to block TAP function. [44][45][46][47] Interestingly, MHV-68 has been shown to degrade TAP and, to a lesser extent, tpn, thereby abrogating both efficient peptide transport and peptide loading onto MHC class I molecules. 47 In contrast, the latent membrane protein LMP1 of EBV uniquely induces TAP expression in BL cell lines.…”

Varicelloviruses avoid T cell recognition by UL49.5-mediated inactivation of the transporter associated with antigen processing

“…Various members of the varicellovirus group down-modulate MHC class I expression (29)(30)(31)(32)(33)(34). Among these viruses, bovine herpesvirus 1 (BHV1), pseudorabies virus (PRV), and equine herpesvirus 1 (EHV1) abolish peptide transport by TAP, resulting in down-regulation of MHC class I surface expression.…”

Cellular gene expression survey of PseudoRabies Virus (PRV) infected Human Embryonic Kidney cells (HEK-293)

“…The microarray approach should potentially have two major advantages for viral disease studies: (1) it should speed up identification of the virus species involved (the virus responsible for SARS was partially identified and sequenced from samples in less than one week by DeRisi's lab using a pan viral microarray [43]), (2) it should allow blind studies in which no prior knowledge about the virus or its impact on cell physiology is required, with the very large number of targets deposited on the micro array covering most of the cellular processes and demonstrating any significant alterations in one or several of these. Large scale analysis of the virus host interaction should then confirm or reveal those cellular targets of interest in understanding the virus and its action on cell physiology and eventually, help to identify potential targets for use in the control of viral infection.…”