Virus-induced type I IFN stimulates generation of immunoproteasomes at the site of infection
Eui-Cheol Shin, … , Peter-M. Kloetzel, Barbara Rehermann
Eui-Cheol Shin, … , Peter-M. Kloetzel, Barbara Rehermann
Published November 1, 2006
Citation Information: J Clin Invest. 2006;116(11):3006-3014. https://doi.org/10.1172/JCI29832.
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Research Article Immunology

Virus-induced type I IFN stimulates generation of immunoproteasomes at the site of infection

Abstract

IFN-γ is known as the initial and primary inducer of immunoproteasomes during viral infections. We now report that type I IFN induced the transcription and translation of immunoproteasome subunits, their incorporation into the proteasome complex, and the generation of an immunoproteasome-dependent CD8 T cell epitope in vitro and provide in vivo evidence that this mechanism occurs prior to IFN-γ responses at the site of viral infection. Type I IFN–mediated generation of immunoproteasomes was initiated by either poly(I:C) or HCV RNA in human hepatoma cells and was inhibited by neutralization of type I IFN. In serial liver biopsies of chimpanzees with acute HCV infection, increases in immunoproteasome subunit mRNA preceded intrahepatic IFN-γ responses by several weeks, instead coinciding with intrahepatic type I IFN responses. Thus, viral RNA–induced innate immune responses regulate the antigen-processing machinery, which occurs prior to the detection of IFN-γ at the site of infection. This mechanism may contribute to the high effectiveness (95%) of type I IFN–based therapies if administered early during HCV infection.

Authors

Eui-Cheol Shin, Ulrike Seifert, Takanobu Kato, Charles M. Rice, Stephen M. Feinstone, Peter-M. Kloetzel, Barbara Rehermann

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Figure 3

Intracellular dsRNA induces the expression of immunoproteasome subunits by the secretion of type I IFN.

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Intracellular dsRNA induces the expression of immunoproteasome subunits ...
Huh-7 cells were transfected with 10 μg poly(I:C) (squares) or 10 μg pcDNA3.1 plasmid DNA (inverted triangles), treated with 10 μg/ml extracellular poly(I:C) (triangles), or were mock transfected (circles). (A) Quantitation of IFN-β and 2,5-OAS-1 mRNA by real-time PCR. Bars (indicating secreted IFN-β) are shown only for the poly(I:C)-transfected Huh-7 cells because no secreted IFN-β was detectable in the control cultures of DNA-transfected Huh-7 cells or Huh-7 cells treated extracellularly with poly(I:C). (B) Quantitation of mRNA levels of immunoproteasome subunits β1i, β5i, β2i and constitutive subunit β7 by real-time PCR. (C–E) Detection of immunoproteasome subunits β1i, β5i, and β2i by Western blot analysis. (C and D) Huh-7 cells were treated with IFN-α and IFN-γ as well as (C) treated with extracellular DNA and poly(I:C) or (D) transfected with DNA and poly(I:C). (E) Four hours after poly(I:C) transfection of Huh-7 cells, 5,000 U/ml neutralizing anti–IFN-α and 2,000 U/ml neutralizing anti–IFN-β, alone or in combination, as well as 1 μg/ml VV B18R protein were added into culture and incubated for 48 hours, and Western blot was performed to detect immunoproteasome subunits. Anti–IFN-α/β, combination of IFN-α– and IFN-β–neutralizing antibodies. The density of the Western blot bands was quantified and expressed as percent of the density of the α4 control band.