Downregulation of Class I Major Histocompatibility Complex Surface Expression by Varicella-Zoster Virus Involves Open Reading Frame 66 Protein Kinase-Dependent and -Independent Mechanisms

Abstract

We show here that the varicella-zoster virus (VZV) open reading frame 66 (ORF66) protein kinase is one mechanism employed to reduce class I major histocompatibility complex (MHC-I) surface expression in VZV-infected cells. Cells expressing enhanced green fluorescent protein-tagged functional and inactivated ORF66 (GFP-66 and GFP-66kd) from replication-defective adenovirus vectors revealed that ORF66 reduced MHC-I surface levels in a manner dependent on kinase activity. Cells infected with recombinant VZV expressing GFP-66 exhibited a significantly greater reduction in MHC-I surface expression than that observed in cells infected with VZV disrupted in GFP-66 expression. MHC-I maturation was delayed in its transport from the endoplasmic reticulum through the Golgi in both adenovirus-transduced cells expressing only GFP-66 and in VZV-infected cells expressing high levels of GFP-66, and this was predominantly kinase dependent. MHC-I levels were reduced in VZV-infected cells, and analyses of intracellular MHC-I revealed accumulation of folded MHC-I in the Golgi region, irrespective of ORF66 expression. Thus, the ORF66 kinase is important for VZV-mediated MHC-I downregulation, but additional mechanisms also may be involved. Analyses of the VZV ORF9a protein, the ortholog of the bovine herpesvirus 1 transporter associated with antigen processing inhibitor UL49.5 revealed no effects on MHC-I. These results establish a new role for viral protein kinases in immune evasion and suggest that VZV utilizes unique mechanisms to inhibit antigen presentation.Varicella-zoster virus (VZV) is the human-restricted member of the herpesvirus subfamily Alphaherpesvirinae and causes chicken pox upon primary infection and herpes zoster (shingles) following reactivation from a prolonged period of neuronal latency in the sensory ganglia. Based on the current model of pathogenesis (38), efficient dissemination, disease, and establishment of latency within the infected host requires VZV growth in multiple cell types. Following inhalation, VZV is spread to epidermal sites of replication by a T-lymphocyteassociated viremia. Infection likely occurs in the tonsils, with VZV preferentially infecting memory CD4 ϩ T lymphocytes (39). These T cells can home to and mediate infection of human skin allografts in the severe combined immunodeficient (SCID)-hu model of VZV infection (40). In humans, skin lesions occur 10 to 21 days after the initial inoculation, and VZV DNA is detected in peripheral blood mononuclear cells during primary infection (13,45). VZV accesses axons of innervating sensory neurons in the skin and establishes a lifelong latent infection in neurons of the dorsal root ganglia. In contrast with latency of the closely related herpes simplex virus type 1 (HSV-1), VZV latency is characterized by persistent transcription, and possibly expression, of several viral lytic genes, including open reading frames (ORFs) 4, 21, 29, 62, 63, and 66 (10,

Histone Deacetylases 1 and 2 Are Phosphorylated at Novel Sites during Varicella-Zoster Virus Infection

“…Replication-deficient wild-type (AdORF66WT) and kinasedeficient (AdORF66KD) adenoviruses expressing ORF66p tagged at their amino termini with EGFP under the control of a Tet-repressible promoter were used to ask if autonomous expression of ORF66p was sufficient to induce modification of HDAC1 and HDAC2 (10). Expression from these adenoviruses was dependent on coinfection with an adenovirus expressing the tetracycline tTa transactivator (AdTetOff) and the absence of doxycycline.…”

“…This virus allowed us to track the spread of infection in real time. The EGFP tag does not hinder viral replication or ORF66p activity (10). At 24, 48, and 72 hpi, cells were harvested and the electrophoretic mobilities of HDAC1 and HDAC2 were examined by Western blotting (Fig.…”

Immune Regulation and Evasion of Mammalian Host Cell Immunity During Viral Infection

“…They all produce infectious progenies by downregulating MHC-II expression without changing any Adenovirus also retains MHC-I molecules in ER [36,45,65,106]. The complex assembly of the mature MHC complex has been simplified and depicted with a small circle, filled in black.…”

“…HIV-1 protein, Nef diverts MHC-I trafficking from the trans-Golgi network to the lysosomal compartment [109,145]. Varicella zoster virus (VZV) retains mature MHC-I complexes in the cis/medial Golgi of the trans-Golgi network that regulates the vesicular trafficking of these molecules [36]. 5a Transport of peptide loaded mature MHC from Golgi to cell surface for antigen presentation to CD8 ?…”

“…HIV Vpu protein holds the nascent MHC-I chains in the ER and LANA1 of KSHV can inhibit MHC-I peptide presentation [71,80]. Varicella-zoster virus (VZV) constitute an open reading frame 66 (ORF66) protein kinase, that can reduce the expression of MHC-I by delaying the maturation step of transport from ER through Golgi apparatus [36]. Adenoviruses are found to evade immune recognition by disrupting the pathway of MHC-I assembly in ER.…”