High serum CXCL10 in Rickettsia conorii infection is endothelial cell mediated subsequent to whole blood activation

Cytokine. 2016 Jul:83:269-274. doi: 10.1016/j.cyto.2016.05.006. Epub 2016 May 12.

Abstract

Background: The pathophysiological hallmark of Rickettsia conorii (R. conorii) infection comprises infection of endothelial cells with perivascular infiltration of T-cells and macrophages. Although interferon (IFN)-γ-induced protein 10 (IP-10)/CXCL10 is induced during vascular inflammation, data on CXCL10 in R. conorii infection is scarce.

Methods: Serum CXCL10 was analyzed in two cohorts of southern European patients with R. conorii infection using multiplex cytokine assays. The mechanism of R. conorii-induced CXCL10 release was examined ex vivo using human whole blood interacting with endothelial cells.

Results: (i) At admission, R. conorii infected patients had excessively increased CXCL10 levels, similar in the Italian (n=32, ∼56-fold increase vs controls) and the Spanish cohort (n=38, ∼68-fold increase vs controls), followed by a marked decrease after recovery. The massive CXCL10 increase was selective since it was not accompanied with similar changes in other cytokines. (ii) Heat-inactivated R. conorii induced a marked CXCL10 increase when whole blood and endothelial cells were co-cultured. Even plasma obtained from R. conorii-exposed whole blood induced a marked CXCL10 release from endothelial cells, comparable to the levels found in serum of R. conorii-infected patients. Bacteria alone did not induce CXCL10 production in endothelial cells, macrophages or smooth muscle cells.

Conclusions: We show a massive and selective serum CXCL10 response in R. conorii-infected patients, likely reflecting release from infected endothelial cells characterized by infiltrating T cells and monocytes. The CXCL10 response could contribute to T-cell infiltration within the infected organ, but the pathologic consequences of CXCL10 in clinical R. conorii infection remain to be defined.

Keywords: CXCL10; IP-10; Inflammation; Mediterranean spotted fever; Rickettsia conorii.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Boutonneuse Fever / blood*
  • Boutonneuse Fever / pathology
  • Chemokine CXCL10 / biosynthesis*
  • Cohort Studies
  • Endothelial Cells / metabolism*
  • Endothelial Cells / pathology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Monocytes / metabolism
  • Monocytes / pathology
  • Rickettsia conorii*
  • T-Lymphocytes / metabolism
  • T-Lymphocytes / pathology

Substances

  • CXCL10 protein, human
  • Chemokine CXCL10