Bluetongue virus infection activates bovine monocyte-derived macrophages and pulmonary artery endothelial cells

Abstract

Bluetongue virus (BTV) is the cause of bluetongue (BT), an emerging, arthropod-transmitted disease of ungulates. The cellular tropism of BTV in ruminants includes macrophages, dendritic cells and endothelial cells (EC), and fulminant infection is characterized by lesions consistent with those of so-called viral hemorrhagic fevers. Specifically, BT is characterized by vascular injury with hemorrhage, tissue infarction and widespread edema. To further investigate the pathogenesis of vascular injury in BT, we evaluated the responses of cultured bovine pulmonary artery EC (bPAEC) and monocyte -derived macrophages (bMDM) to BTV infection by measuring transcript levels of genes encoding molecules important in mediating EC activation and/or endothelial barrier dysregulation. The data confirm that BTV infection of bPAEC resulted in increased transcription of genes encoding chemokine ligand 2 (CCL2) and E-selectin, and BTVinfection of bMDM resulted in increased transcription of genes encoding TNF-α, IL-1β, IL-8, and inducible nitric oxide synthase (iNOS). The data from these in vitro studies provide further evidence that cytokines and other vasoactive substances produced in macrophages potentially contribute to vascular injury in BTV-infected ruminants, along with direct effects of the virus itself on ECs.

Pathological Characterization Of IFNAR(-/-) Mice Infected With Bluetongue Virus Serotype 4

“…Nevertheless, the excessive production of iNOS, and subsequent high levels of NO during viral infections may have negative effects, acting with other damaging oxidants to promote excessive inflammation or induce apoptosis, as it has been described in influenza virus infection 43. As it has been described in the pathogenesis of viral hemorrhagic fevers 15, 44, 45, the overproduction of iNOS and pro-inflammatory cytokines in BTV infected tissues could contribute to the pathology of this disease-causing vasodilatation, increase of leukocyte adhesion and thrombus formation, and increase of vascular permeability of endothelial cells with subsequent tissue edema 39, 46.…”

“…Besides the induction of pro-inflammatory cytokines observed in serum and tissues of BTV infected ruminants, it has been also reported that BTV infection of sheep led to enhance transcription of iNOS in peripheral blood mononuclear cells and regional lymphoid organs 42. Furthermore, in vitro studies provided evidence that cytokines and other vasoactive substances produced in macrophages potentially contributed to vascular injury in BTV-infected ruminants 39. The IFNAR(-/-) mouse model reproduced in vivo the increase expression of iNOS in BTV-4(M) infected tissues.…”

“…Previously it was reported from both in vivo and in vitro studies that BTV- infected mononuclear leukocytes (dendritic cells, macrophages, monocytes and some lymphocytes) secrete numerous pro-inflammatory cytokines, including IFN-α, IFN-γ, IL-12, TNF, IL-1β and IL-8 8, 14, 37-39. Induction of a balanced antiviral and pro-inflammatory response is crucial to control viral replication and activate optimal adaptive immune responses.…”

“…Although such response is required for viral clearance, depending on the type of disease, it may also damage tissues in severe cases, contributing to disease pathogenesis 40. The endothelial injury observed in ruminants during BTV infection could be due to the direct pathogenic effect of BTV infection on endothelial cells or to a response to inflammatory mediators released by virus-infected endothelial cells and, possibly, other cell types such as monocytes/macrophages 8, 14, 18, 39. Furthermore, in vitro BTV infections of peripheral blood mononuclear cells (PBMC) from a number of ruminant species resulted in the production of inflammatory cytokines.…”

“…Furthermore, in vitro BTV infections of peripheral blood mononuclear cells (PBMC) from a number of ruminant species resulted in the production of inflammatory cytokines. BTV infection of PBMC from bovine 39, sheep and goats 41 induced IL-1, 6, 8, and 10, IFN-γ, TNF and iNOS, although these studies used different experimental designs and BTV serotypes, making correlations among species difficult.…”