Tissue Tropism in Host Transcriptional Response to Members of the Bovine Respiratory Disease Complex.

Bovine respiratory disease (BRD) is the most common infectious disease of beef and dairy cattle and is characterized by a complex infectious etiology that includes a variety of viral and bacterial pathogens. We examined the global changes in mRNA abundance in healthy lung and lung lesions and in the lymphoid tissues bronchial lymph node, retropharyngeal lymph node, nasopharyngeal lymph node and pharyngeal tonsil collected at the peak of clinical disease from beef cattle experimentally challenged with either bovine respiratory syncytial virus, infectious bovine rhinotracheitis, bovine viral diarrhea virus, Mannheimia haemolytica or Mycoplasma bovis. We identified signatures of tissue-specific transcriptional responses indicative of tropism in the coordination of host's immune tissue responses to infection by viral or bacterial infections. Furthermore, our study shows that this tissue tropism in host transcriptional response to BRD pathogens results in the activation of different networks of response genes. The differential crosstalk among genes expressed in lymphoid tissues was predicted to be orchestrated by specific immune genes that act as 'key players' within expression networks. The results of this study serve as a basis for the development of innovative therapeutic strategies and for the selection of cattle with enhanced resistance to BRD

Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex

Bovine respiratory disease complex (BRDC) is an important cause of mortality and morbidity in cattle; costing the dairy and beef industries millions of dollars annually, despite the use of vaccines and antibiotics. BRDC is caused by one or more of several viruses (bovine respiratory syncytial virus, bovine herpes type 1 also known as infectious bovine rhinotracheitis, and bovine viral diarrhea virus), which predispose animals to infection with one or more bacteria. These include: Pasteurella multocida, Mannheimia haemolytica, Mycoplasma bovis, and Histophilus somni. Some cattle appear to be more resistant to BRDC than others. We hypothesize that appropriate immune responses to these pathogens are subject to genetic control. To determine which genes are involved in the immune response to each of these pathogens it was first necessary to experimentally induce infection separately with each pathogen to document clinical and pathological responses in animals from which tissues were harvested for subsequent RNA sequencing. Herein these infections and animal responses are described

The Sickness Response in Bovine Respiratory Disease

Bovine respiratory disease (BRD) is the most common disorder in North American beef cattle. This work aimed to describe the BRD sickness response, identify measures to improve detection, and assess effects of a non-steroidal anti-inflammatory drug (NSAID). We hypothesized that BRD challenge would induce a sickness response, with an NSAID and antibiotics attenuating this more than antibiotics alone. Challenged steers (BRD) were infected with a respiratory virus (d 0) and bacteria (d 5) and No-challenge steers received sterile medium. All were treated once with antibiotics, and half also received one 0.5 mg/kg NSAID dose (d 8). After applying inclusion criteria, sample size was 5 BRD-No NSAID, 4 BRD-NSAID, 2 No-challenge-No NSAID, and 3 No-challenge-NSAID. Clinical examinations were performed daily, loggers tracked fever (d 3 to 10) and lying (d 0 to 13) continuously, dry matter intake (DMI) was recorded/24 h (d 0 to 12), grooming was assessed for 20 min/d (d 4, 6 to 11, 13), and mechanical nociceptive threshold (MNT) testing evaluated hyperalgesia (d 4, 6, 7, 9, 10, 13). Average daily gain (ADG) was calculated from end-of-study and baseline BW. Clinical signs occurred d 2 to 11, peaking on d 5. Sickness response components peaked on different days. Compared with No-challenge, BRD had fever d 3 to 7 (up to 2.1°C higher on d 3; P < 0.001), lower DMI d 2 to 10 (88% less at the lowest point on d 5; P < 0.01), lower ADG (88% less; P < 0.01), higher total lying time (up to 11% higher on d 3; P = 0.01), longer lying bouts d 3 to 5 and d 9 (up to 87% higher on d 4; P < 0.01) and a tendency for fewer lying bouts (22% less; P = 0.07). Compared with No-challenge, BRD groomed less (58% lower; P = 0.02) and had hyperalgesia (44% lower MNT; P < 0.01). The NSAID had no effect (P ≥ 0.11) except for an interaction involving total lying time (P = 0.05), possibly due to experimental design limitations or poor efficacy. In summary, the sickness response began within 2 d of challenge, persisting for up to 10 d. Some aspects mirrored fluctuating clinical signs and appeared early (DMI, fever); others reflected disease in a relatively invariable manner (lying bout number, hyperalgesia, grooming). The most persistent changes lasted for ≥ 5 d (DMI, fever, hyperalgesia, and grooming). Sickness response components that occur early, persist and mirror clinical sign progression may be better for BRD detection; from this perspective, DMI was the most promising

Immunological Response to Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex: An RNA-Sequence Analysis of the Bronchial Lymph Node Transcriptome

<div><p>Susceptibility to bovine respiratory disease (BRD) is multi-factorial and is influenced by stress in conjunction with infection by both bacterial and viral pathogens. While vaccination is broadly used in an effort to prevent BRD, it is far from being fully protective and cases diagnosed from a combination of observed clinical signs without any attempt at identifying the causal pathogens are usually treated with antibiotics. Dairy and beef cattle losses from BRD are profound worldwide and genetic studies have now been initiated to elucidate host loci which underlie susceptibility with the objective of enabling molecular breeding to reduce disease prevalence. In this study, we employed RNA sequencing to examine the bronchial lymph node transcriptomes of controls and beef cattle which had individually been experimentally challenged with bovine respiratory syncytial virus, infectious bovine rhinotracheitis, bovine viral diarrhea virus, <i>Pasteurella multocida</i>, <i>Mannheimia haemolytica</i> or <i>Mycoplasma bovis</i> to identify the genes that are involved in the bovine immune response to infection. We found that 142 differentially expressed genes were located in previously described quantitative trait locus regions associated with risk of BRD. Mutations affecting the expression or amino acid composition of these genes may affect disease susceptibility and could be incorporated into molecular breeding programs. Genes involved in innate immunity were generally found to be differentially expressed between the control and pathogen-challenged animals suggesting that variation in these genes may lead to a heritability of susceptibility that is pathogen independent. However, we also found pathogen-specific expression profiles which suggest that host genetic variation for BRD susceptibility is pathogen dependent.</p></div

Heatmap for 200 differentially expressed genes with the greatest fold differences from all pathogen challenges using hierarchical clustering analysis.

<p>Hierarchical clustering of gene expression profiles in all samples. Each row represents a gene and each column an animal. The extent of expression of each gene in each sample is indicated by a color code. The color key ranges from saturated red for log_<b>2</b> ratios less or equal to -5.0 to saturated yellow for log_<b>2</b> ratios greater than or equal to 10. Red indicates an increased gene expression in the challenged animals. Legend: bact_0, bact_1 and bact_2 are <i>M</i>. <i>bovis</i> challenged; bact_3, bact_4, bact_5 and bact_6 are <i>P</i>. <i>multocida</i> challenged; bact_7, bact_8, bact_9 and bact_10 are <i>M</i>. <i>haemolytica</i> challenged; virus_0, virus_1, virus_2 and virus_3 are BRSV challenged; virus_4, virus_5, virus_6 and virus_7 are BVDV challenged and virus_8, virus_9, virus_10 and virus_11 are IBR challenged.</p

Histopathology of pharynx from IBR infected steer.

<p>(A) Focal ulcerative pharyngitis with epithelial necrosis (area indicated by length of the arrow), (B) Immunohistochemistry of lesions demonstrating positive cytoplasmic staining for IBR, indicated by arrows and red/brown color.</p

Histopathology of lung from BRSV infected steer.

<p>(A) Bronchiolitis with epithelial necrosis and numerous syncytia (arrows), (B) Immunohistochemistry stain showing positive stain for BRSV in bronchioles (brown color and arrow).</p

Principal component analysis for gene-level features.

<p>Principal component analysis for gene-level features.</p

Dynamic range of FPKM values represented as log₁₀ transformed FPKM values for each gene calculated for each biological replicate.

<p>Legend: bact_0, bact_1 and bact_2 are <i>M</i>. <i>bovis</i> challenged; bact_3, bact_4, bact_5 and bact_6 are <i>P</i>. <i>multocida</i> challenged; bact_7, bact_8, bact_9 and bact_10 are <i>M</i>. <i>haemolytica</i> challenged; virus_0, virus_1, virus_2 and virus_3 are BRSV challenged; virus_4, virus_5, virus_6 and virus_7 are BVDV challenged and virus_8, virus_9, virus_10 and virus_11 are IBR challenged.</p

Differentially Expressed Genes with the Largest Expression Variances by Challenge Group.

<p>Differentially Expressed Genes with the Largest Expression Variances by Challenge Group.</p