PLoS Pathogens (Feb 2017)

RNA-Seq analysis of chikungunya virus infection and identification of granzyme A as a major promoter of arthritic inflammation.

  • Jane A C Wilson,
  • Natalie A Prow,
  • Wayne A Schroder,
  • Jonathan J Ellis,
  • Helen E Cumming,
  • Linden J Gearing,
  • Yee Suan Poo,
  • Adam Taylor,
  • Paul J Hertzog,
  • Francesca Di Giallonardo,
  • Linda Hueston,
  • Roger Le Grand,
  • Bing Tang,
  • Thuy T Le,
  • Joy Gardner,
  • Suresh Mahalingam,
  • Pierre Roques,
  • Phillip I Bird,
  • Andreas Suhrbier

DOI
https://doi.org/10.1371/journal.ppat.1006155
Journal volume & issue
Vol. 13, no. 2
p. e1006155

Abstract

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Chikungunya virus (CHIKV) is an arthritogenic alphavirus causing epidemics of acute and chronic arthritic disease. Herein we describe a comprehensive RNA-Seq analysis of feet and lymph nodes at peak viraemia (day 2 post infection), acute arthritis (day 7) and chronic disease (day 30) in the CHIKV adult wild-type mouse model. Genes previously shown to be up-regulated in CHIKV patients were also up-regulated in the mouse model. CHIKV sequence information was also obtained with up to ≈8% of the reads mapping to the viral genome; however, no adaptive viral genome changes were apparent. Although day 2, 7 and 30 represent distinct stages of infection and disease, there was a pronounced overlap in up-regulated host genes and pathways. Type I interferon response genes (IRGs) represented up to ≈50% of up-regulated genes, even after loss of type I interferon induction on days 7 and 30. Bioinformatic analyses suggested a number of interferon response factors were primarily responsible for maintaining type I IRG induction. A group of genes prominent in the RNA-Seq analysis and hitherto unexplored in viral arthropathies were granzymes A, B and K. Granzyme A-/- and to a lesser extent granzyme K-/-, but not granzyme B-/-, mice showed a pronounced reduction in foot swelling and arthritis, with analysis of granzyme A-/- mice showing no reductions in viral loads but reduced NK and T cell infiltrates post CHIKV infection. Treatment with Serpinb6b, a granzyme A inhibitor, also reduced arthritic inflammation in wild-type mice. In non-human primates circulating granzyme A levels were elevated after CHIKV infection, with the increase correlating with viral load. Elevated granzyme A levels were also seen in a small cohort of human CHIKV patients. Taken together these results suggest granzyme A is an important driver of arthritic inflammation and a potential target for therapy.Trial registrationClinicalTrials.gov NCT00281294.