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

Dayle Johnston,Matthew S Mccabe,S Louise Cosby,Jeremy F Taylor,Michael Mcmenamy,Bernadette Earley,Jaewoo Kim,Ken Lemon,Catherine Duffy,Sinead M Waters,Gordon Blackshields

doi:10.1038/s41598-019-51094-z

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.

Highlights

Bovine Respiratory Disease (BRD) is the leading cause of morbidity and mortality in calves over one month of age in Ireland[1,2,3,4] and internationally[5,6,7,8]
Two RNA-Seq studies performed in crossbred Angus-Hereford beef calves that were artificially challenged with single pathogens of the bovine respiratory disease complex (BRDC) at the University of California Davis have discovered multiple genes and pathways to be differentially expressed following a Bovine Respiratory Syncytial Virus (BRSV) challenge in bronchial lymph node[18] and in multiple lymphoid and lung tissues[19]
The aims of this study were: (1) to describe the clinical and haematological response to a BRSV challenge infection, (2) to elucidate the genes and pathways involved in the host’s bronchial lymph node transcriptome response to an experimental challenge with BRSV in Irish artificially-reared dairy calves, and (3) to compare the bronchial lymph node transcriptomic response of these dairy calves challenged with BRSV to that of the crossbred beef calves challenged with BRSV at the University of California Davis[18]

Summary

Introduction

Bovine Respiratory Disease (BRD) is the leading cause of morbidity and mortality in calves over one month of age in Ireland[1,2,3,4] and internationally[5,6,7,8]. The aims of this study were: (1) to describe the clinical and haematological response to a BRSV challenge infection, (2) to elucidate the genes and pathways involved in the host’s bronchial lymph node transcriptome response to an experimental challenge with BRSV in Irish artificially-reared dairy calves, and (3) to compare the bronchial lymph node transcriptomic response of these dairy calves challenged with BRSV to that of the crossbred beef calves challenged with BRSV at the University of California Davis[18]. These differentially expressed genes (DEG), and in particular the genes which were commonly differentially expressed in both the present study and the US study[18] may harbour variants which influence the host’s resistance to BRSV

Objectives

Methods

Results

Conclusion