SARS Coronavirus Spike Protein-Induced Innate Immune Response Occurs via Activation of the NF-kappaB Pathway in Human Monocyte Macrophages in Vitro

Virus Res. 2009 Jun;142(1-2):19-27. doi: 10.1016/j.virusres.2009.01.005. Epub 2009 Jan 29.

Abstract

A purified recombinant spike (S) protein was studied for its effect on stimulating human peripheral blood monocyte macrophages (PBMC). We examined inflammatory gene mRNA abundances found in S protein-treated PBMC using gene arrays. We identified differential mRNA abundances of genes with functional properties associated with antiviral (CXCL10) and inflammatory (IL-6 and IL-8) responses. We confirmed cytokine mRNA increases by real-time quantitative(q) RT-PCR or ELISA. We further analyzed the sensitivity and specificity of the prominent IL-8 response. By real-time qRT-PCR, S protein was shown to stimulate IL-8 mRNA accumulation in a dose dependent manner while treatment with E protein did not. Also, titration of S protein-specific production and secretion of IL-8 by ELISA showed that the dose of 5.6nM of S produced a significant increase in IL-8 (p=0.003) compared to mock-treated controls. The increase in IL-8 stimulated by a concentration of 5.6nM of S was comparable to concentrations seen for S protein binding to ACE2 or to neutralizing monoclonal antibody suggesting a physiological relevance. An NF-kappaB inhibitor, TPCK (N-Tosyl-L-Phenylalanine Chloromethyl Ketone) could suppress IL-8 production and secretion in response to S protein in PBMC and THP-1 cells and in HCoV-229E virus-infected PBMC. Activation and translocation of NF-kappaB was shown to occur rapidly following exposure of PBMC or THP-1 cells to S protein using a highly sensitive assay for active nuclear NF-kappaB p65 transcription factor. The results further suggested that released or secreted S protein could activate blood monocytes through recognition by toll-like receptor (TLR)2 ligand.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cells, Cultured
  • Gene Expression
  • Humans
  • Interleukin-6 / genetics
  • Interleukin-6 / immunology
  • Interleukin-8 / genetics
  • Interleukin-8 / immunology
  • Macrophages / immunology*
  • Membrane Glycoproteins / immunology*
  • SARS Virus / immunology*
  • Severe Acute Respiratory Syndrome / genetics
  • Severe Acute Respiratory Syndrome / immunology*
  • Severe Acute Respiratory Syndrome / virology
  • Spike Glycoprotein, Coronavirus
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / immunology*
  • Viral Envelope Proteins / immunology*

Substances

  • Interleukin-6
  • Interleukin-8
  • MHV surface projection glycoprotein
  • Membrane Glycoproteins
  • Spike Glycoprotein, Coronavirus
  • Transcription Factor RelA
  • Viral Envelope Proteins
  • spike glycoprotein, SARS-CoV