Murine Cytomegalovirus Inhibits Interferon γ–induced Antigen Presentation to CD4 T Cells by Macrophages Via Regulation of Expression of Major Histocompatibility Complex Class II–associated Genes

Abstract

CD4 T cells and interferon γ (IFN-γ) are required for clearance of murine cytomegalovirus (MCMV) infection from the salivary gland in a process taking weeks to months. To explain the inefficiency of salivary gland clearance we hypothesized that MCMV interferes with IFN-γ induced antigen presentation to CD4 T cells. MCMV infection inhibited IFN-γ–induced presentation of major histocompatibility complex (MHC) class II associated peptide antigen by differentiated bone marrow macrophages (BMMφs) to a T cell hybridoma via impairment of MHC class II cell surface expression. This effect was independent of IFN-α/β induction by MCMV infection, and required direct infection of the BMMφs with live virus. Inhibition of MHC class II cell surface expression was associated with a six- to eightfold reduction in IFN-γ induced IAb mRNA levels, and comparable decreases in IFN-γ induced expression of invariant chain (Ii), H-2Ma, and H-2Mb mRNAs. Steady state levels of several constitutive host mRNAs, including β-actin, cyclophilin, and CD45 were not significantly decreased by MCMV infection, ruling out a general effect of MCMV infection on mRNA levels. MCMV effects were specific to certain MHC genes since IFN-γ–induced transporter associated with antigen presentation (TAP)2 mRNA levels were minimally altered in infected cells. Analysis of early upstream events in the IFN-γ signaling pathway revealed that MCMV did not affect activation and nuclear translocation of STAT1α, and had minor effects on the early induction of IRF-1 mRNA and protein. We conclude that MCMV infection interferes with IFN-γ–mediated induction of specific MHC genes and the Ii at a stage subsequent to STAT1α activation and nuclear translocation. This impairs antigen presentation to CD4 T cells, and may contribute to the capacity of MCMV to spread and persist within the infected host.

Murine cytomegalovirus paralyzes macrophages by blocking IFNγ-induced promoter assembly

“…Bone marrow M (BMM ) lacking IFN␣␤ receptor-1 (IFNAR1) chain (IFNAR1Ϫ͞Ϫ mice) and MCMV (ATCC no. VR-194, Lot 10) were cultured as described (6,10,15,19). BMM were infected for 1 h at a multiplicity of infection (moi) of 5 in 2 ml of media at 37°C and then treated with or without 100 units͞ml murine IFN␥ (R & D Systems) for 6, 24, and 48 h. UV inactivation of MCMV by using a NuAire (Plymouth, MN) laminar flow hood UV bulb for 30 min resulted in a Ͼ10 7 fold decrease in titer and an absence of viral gene expression by quantitative RT-PCR (qRT-PCR) analysis.…”

“…M infection was assessed by immunofluorescence by counting Ͼ200 cells after staining for IE1 protein (10). Fluorescence-activated cell sorting (FACS) analysis was performed as described (15,19) by using 2G9-phycoerythrin (PE) (MHC class II) and stem cell antigen-1 (Sca-1)-PE (PharMingen).…”

“…Given the importance of M and IFN␥ for control of CMV infection, it is not surprising that these viruses have strategies for altering differentiation of infected cells such as dendritic cells and M (14)(15)(16)(17)(18). For example, infection with HCMV or MCMV effectively inhibits IFN␥-induced antigen presentation by MHC class II by inhibiting IFN␥ induction of genes involved in antigen presentation (15,(19)(20)(21).…”

“…For example, infection with HCMV or MCMV effectively inhibits IFN␥-induced antigen presentation by MHC class II by inhibiting IFN␥ induction of genes involved in antigen presentation (15,(19)(20)(21).…”

Mouse cytomegalovirus inhibits beta interferon (IFN-β) gene expression and controls activation pathways of the IFN-β enhanceosome

“…The CMV interference with IFN production is complemented by further independent strategies counteracting the efficacy of IFNs. Through establishing a state of IFN receptor unresponsiveness by disrupting Jak/STAT signalling and antiviral gene expression (Heise et al, 1998;Presti et al, 2001;Zimmermann et al, 2005) MCMV builds protected 'virus factories' enabling efficient viral replication even in the presence of significant concentrations of IFNs. On the other hand MCMV triggering of IFN producing capacities in pDCs could be essential for the augmenting of natural killer and cytotoxic T lymphocyte responses attaining a balanced virus-host relationship.…”