Maternal Influenza A Virus Infection Restricts Fetal and Placental Growth and Adversely Affects the Fetal Thymic Transcriptome.

Maternal influenza A viral infections in humans are associated with low birth weight, increased risk of pre-term birth, stillbirth and congenital defects. To examine the effect of maternal influenza virus infection on placental and fetal growth, pregnant C57BL/6 mice were inoculated intranasally with influenza A virus A/CA/07/2009 pandemic H1N1 or phosphate-buffered saline (PBS) at E3.5, E7.5 or E12.5, and the placentae and fetuses collected and weighed at E18.5. Fetal thymuses were pooled from each litter. Placentae were examined histologically, stained by immunohistochemistry (IHC) for CD34 (hematopoietic progenitor cell antigen) and vascular channels quantified. RNA from E7.5 and E12.5 placentae and E7.5 fetal thymuses was subjected to RNA sequencing and pathway analysis. Placental weights were decreased in litters inoculated with influenza at E3.5 and E7.5. Placentae from E7.5 and E12.5 inoculated litters exhibited decreased labyrinth development and the transmembrane protein 150A gene was upregulated in E7.5 placentae. Fetal weights were decreased in litters inoculated at E7.5 and E12.5 compared to controls. RNA sequencing of E7.5 thymuses indicated that 957 genes were downregulated ≥2-fold including Mal, which is associated with Toll-like receptor signaling and T cell differentiation. There were 28 upregulated genes. It is concluded that maternal influenza A virus infection impairs fetal thymic gene expression as well as restricting placental and fetal growth.

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

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 (ECs), 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 BTV infection of bMDM resulted in increased transcription of genes encoding TNF-alpha, IL-1beta, 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.

Bluetongue virus infection alters the impedance of monolayers of bovine endothelial cells as a result of cell death.

Bluetongue virus (BTV) is the cause of bluetongue, an emerging, arthropod-transmitted disease of ungulates. Bluetongue is characterized by vascular injury with hemorrhage, tissue infarction and widespread edema, lesions that are consistent with those of the so-called viral hemorrhagic fevers. To further investigate the pathogenesis of vascular injury in bluetongue, we utilized an electrical impedance assay and immunofluorescence staining to compare the effects of BTV infection on cultured bovine endothelial cells (bPAEC) with those of inducers of cell death (Triton X-100) and interendothelial gap formation (tissue necrosis factor [TNF]). The data confirm that the adherens junctions of BTV-infected bPAECs remained intact until 24h post-infection, and that loss of monolayer impedance precisely coincided with onset of virus-induced cell death. In contrast, recombinant bovine TNF-alpha caused rapid loss of bPAEC monolayer impedance that was associated with interendothelial gap formation and redistribution of VE-cadherin, but without early cell death. The data from these in vitro studies are consistent with a pathogenesis of bluetongue that involves virus-induced vascular injury leading to thrombosis, hemorrhage and tissue necrosis. However, the contribution of cytokine-induced interendothelial gap formation with subsequent edema and hypovolemic shock contributes to the pathogenesis of bluetongue remains to be fully characterized.