Cormican, P. | bioRxiv Science

bioRxiv2021

Bovine milk somatic cell transcriptomic response to Staphylococcus aureus is dependent on strain genotype

BackgroundMastitis is an economically important disease of dairy cows with Staphylococcus aureus a major cause worldwide. Challenge of Holstein-Friesian cows demonstrated that S. aureus strain MOK124, which belongs to Clonal Complex (CC)151, caused clinical mastitis, while strain MOK023, belonging to CC97, caused mild or subclinical mastitis. The aim of this study was to elucidate the molecular mechanisms of the host immune response utilising a transcriptomic approach. Milk somatic cells were collected from cows infected with either S. aureus MOK023 or MOK124 at 0, 24, 48, 72 and 168 hours post-infection (hpi) and analysed for differentially expressed (DE) genes in response to each strain. ResultsIn response to MOK023, 1278, 2278, 1986 and 1750 DE genes were found at 24, 48, 72 and 168 hpi, respectively, while 2293, 1979, 1428 and 1544 DE genes were found in response to MOK124 at those time points. Genes involved in milk production (CSN1, CSN10, CSN1S2, CSN2, a-LACTA and PRLR) were downregulated in response to both strains, with a more pronounced decrease in the MOK124 group. Immune response pathways such as NF-{kappa}B and TNF signalling were overrepresented in response to both strains at 24 hpi. These immune pathways continued to be overrepresented in the MOK023 group at 48 and 72 hpi, while the Hippo signalling, extracellular matrix interaction (ECM) and tight junction pathways were overrepresented in the MOK124 group between 48 and 168 hpi. Cellular composition analysis demonstrated that a neutrophil response was predominant in response to MOK124, while M1 macrophages were the main milk cell type post-infection in the MOK023 group. ConclusionsA switch from immune response pathways to pathways involved in maintaining the integrity of the epithelial cell layer was observed in the MOK124 group from 48 hpi, which coincided with the occurrence of clinical signs in the infected animals. The higher proportion of M1 macrophages in the MOK023 group and lack of substantial neutrophil recruitment in response to MOK023 may indicate immune evasion by this strain. The results of this study highlight that the somatic cell transcriptomic response to S. aureus is dependent on the genotype of the infecting strain.

genomics↗

bioRxiv2018

Simultaneous detection of DNA and RNA virus species involved in bovine respiratory disease by PCR-free rapid tagmentation-based library preparation and MinION nanopore sequencing

AbstactThe Oxford Nanopore MinION Mk1B is a portable 90 g device that sequences DNA directly at 450 bases/second generating sequence reads in excess of 400 kb. Recent improvements in error rate and speed of library preparation mean that this device has considerable potential for rapid molecular bovine pathogen diagnostics. We tested the MinION for rapid untargeted detection of viral pathogens associated with bovine respiratory disease (BRD), an economically important disease often involving primary infection of the lung by one or more of a number of DNA and/or RNA viruses. We combined three foetal lung cell cultures which were infected with either Bovine Respiratory Syncytial Virus (BRSV), Bovine Herpes Virus 1 (BoHV1) or Bovine Parainfluenza Virus 3 (BPI-3). BoHV1 is a DNA virus and BPI-3 and BRSV are RNA viruses. The cell cultures were treated with DNase and RNase to deplete bovine nucleic acid prior to viral nucleic acid extraction and double-stranded cDNA synthesis. Sequencing libraries were generated by PCR-free tagmentation in under 10 minutes and loaded onto a MinION sequencer. Approximately 7,000 sequencing reads were generated and analysed using high-throughput local BLAST against the NCBI nr/nt database. The top BLAST hit for 2,937 of these reads was identified as a virus. Of these, 2,926 (99.6%) were correctly identified either as BoHV1, BRSV or BPI-3.

molecular biology↗