Differential regulation of human papillomavirus type 8 by interferon regulatory factors 3 and 7

J Virol. 2011 Jan;85(1):178-88. doi: 10.1128/JVI.00998-10. Epub 2010 Oct 27.

Abstract

The genus β human papillomavirus (HPV) type 8 is associated with nonmelanoma skin cancer in patients with epidermodysplasia verruciformis, and evidence for its protumorigenic potential in the general population increases. To date, strategies to suppress genus β HPV infections are limited. Interferon regulatory factors IRF-3 and IRF-7 play key roles in the activation of the innate immune response to viral infections. In this study, we show for the first time that both IRF-3 and IRF-7 regulate transcription of a papillomavirus, but with opposing effects. IRF-7, expressed in the suprabasal layers of human epidermis, increased HPV8 late promoter activity via direct binding to viral DNA. UV-B light-induced activation of the HPV8 promoter involved IRF-7 as a downstream effector. In contrast, IRF-3, expressed in all layers of human epidermis, induced strong HPV8 suppression in primary keratinocytes. IRF-3-mediated suppression prevailed over IRF-7-induced HPV8 transcription. Unlike the E6 oncoprotein of the mucosal high-risk HPV16, the HPV8 E6 protein did not bind to IRF-3 and only weakly antagonized its activity. Strong antiviral activity was also observed, when keratinocytes were treated with potent IRF-3 activators, poly(I:C) or RNA bearing 5' phosphates. In conclusion, we show that IRF-3 activation induces a state of cell-autonomous immunity against HPV in primary human keratinocytes. Our study suggests that local application of IRF-3-activating compounds might constitute an attractive novel therapeutic strategy against HPV8-associated diseases, particularly in epidermodysplasia verruciformis patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Betapapillomavirus / drug effects*
  • Betapapillomavirus / genetics
  • Betapapillomavirus / metabolism
  • Cell Line, Tumor
  • Cells, Cultured
  • Gene Expression Regulation, Viral*
  • Humans
  • Interferon Regulatory Factor-3 / pharmacology*
  • Interferon Regulatory Factor-7 / pharmacology*
  • Interferon Type I / metabolism
  • Keratinocytes / immunology
  • Keratinocytes / virology
  • Transcription, Genetic*

Substances

  • IRF3 protein, human
  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factor-7
  • Interferon Type I