Experimental challenge with bovine respiratory syncytial virus in dairy calves: bronchial lymph node transcriptome response

Abstract

Bovine Respiratory Disease (BRD) is the leading cause of mortality in calves. The objective of this study was to examine the response of the host’s bronchial lymph node transcriptome to Bovine Respiratory Syncytial Virus (BRSV) in a controlled viral challenge. Holstein-Friesian calves were either inoculated with virus (103.5 TCID50/ml × 15 ml) (n = 12) or mock challenged with phosphate buffered saline (n = 6). Clinical signs were scored daily and blood was collected for haematology counts, until euthanasia at day 7 post-challenge. RNA was extracted and sequenced (75 bp paired-end) from bronchial lymph nodes. Sequence reads were aligned to the UMD3.1 bovine reference genome and differential gene expression analysis was performed using EdgeR. There was a clear separation between BRSV challenged and control calves based on gene expression changes, despite an observed mild clinical manifestation of the disease. Therefore, measuring host gene expression levels may be beneficial for the diagnosis of subclinical BRD. There were 934 differentially expressed genes (DEG) (p < 0.05, FDR <0.1, fold change >2) between the BRSV challenged and control calves. Over-represented gene ontology terms, pathways and molecular functions, among the DEG, were associated with immune responses. The top enriched pathways included interferon signaling, granzyme B signaling and pathogen pattern recognition receptors, which are responsible for the cytotoxic responses necessary to eliminate the virus.

ATAC-Seq identifies regions of open chromatin in the bronchial lymph nodes of dairy calves experimentally challenged with bovine respiratory syncytial virus

“…Ninety-three percent (26,518) of the ROCs within 2 kb upstream of a gene were closest to a gene expressed in the BLN (Additional file 3 ). Of the protein-coding genes expressed in the BLN [ 22 ], 82% (11, 047) had a ROC either within the gene or within 2 kb upstream of the gene. Twenty-two percent (1450) of the protein coding genes not expressed in the BLN had a ROC either within the gene or within 2 kb upstream of the gene.…”

“…An understanding of the identity of the variation within the bovine genome which confers variation in resistance to BRD is needed to incorporate genetic variants into breeding programmes designed to breed robust animals with increased resistance to BRD infection. In a previous study, we identified differentially expressed genes [ 22 ] and miRNAs (unpublished observations) in the bronchial lymph nodes (BLN) (the site of antigen presentation and activation of immune effector cells), of Holstein-Friesian calves experimentally challenged with BRSV. Additionally, the transcriptional response to infection with several pathogens involved in the bovine respiratory disease complex (BRDC) in BLN [ 23 ], lung and multiple lymphoid tissues [ 24 ] has previously been described in US Angus x Hereford crossbred beef steers.…”

“…When it is condensed and tightly wrapped around histone proteins (heterochromatin), it is in an inactive and transcriptionally inaccessible state [ 29 ]. While we have previously identified key genes that are expressed during BRSV infection [ 22 ], there is a lack of information on the specific regions of the genome that regulate the response to BRSV infection. The identification of the regions of chromatin that are open in respiratory tissues during BRSV infection will indicate the genomic regions that are transcriptionally active during infection.…”

Bovine Respiratory Syncytial Virus Decreased Pasteurella multocida Adherence by Downregulating the Expression of Intercellular Adhesion Molecule-1 on the Surface of Upper Respiratory Epithelial Cells

“…The respiratory epithelial cells are the first line of defence and function as a physical barrier to protect against invading pathogens (Agnes et al, 2013;Eberle et al, 2016;Cozens et al, 2019), including BRDC-causing pathogens (Liu et al, 2018;Johnston et al, 2019). Under normal conditions, the upper respiratory tract epithelial cells are responsible for inhibiting microbial invasion by trapping pathogens to adherence factors on the cellular surface (Masaki et al, 2011;Mata et al, 2012).…”

Bovine Respiratory Syncytial Virus Enhances the Adherence of Pasteurella multocida to Bovine Lower Respiratory Tract Epithelial Cells by Upregulating the Platelet-Activating Factor Receptor

“…BRSV infections in cattle augment the number of adherent bacteria (Tjønehøj et al, 2003;Tizioto et al, 2015) by destroying the normal transport mechanism used by airway epithelial cells, allowing the flow of bacteria through the lower airway and lung (Spilki et al, 2006;Jordan et al, 2015). Furthermore, BRSV infection of the lower respiratory tract can stimulate a substantial increase in bacterial load and lead to secondary complications and the development of severe pneumonia (Johnston et al, 2019).…”