The early phase transcriptome of bovine monocyte-derived macrophages infected with Staphylococcus aureus in vitro

Abstract

BackgroundIn the mammary gland, local recruitment and action of macrophages is a key immunological defence mechanism against infection. Macrophages are members of the innate immune system, serve as the first line of the defence against invading pathogens and are critical effectors and regulators of inflammation. We have examined the early phase response of bovine macrophages to infection with live Staphylococcus aureus. Genome-wide transcript profiling of blood monocyte-derived macrophages from six Norwegian Red heifers infected with live S. aureus for 2 and 6 hours in vitro was performed.ResultsAbout 420 of the 17 000 genes on the ARK-Genomics bovine cDNA array were differentially regulated at 6 hours post infection. Approximately 70% of the responding genes had a known identity (Entrez Gene ID) and were used in the identification of overrepresented pathways and biological functions in the dataset.Analysis of a subset of differentially regulated genes (List eQG) obtained by comparison with data from genome-wide association mapping in Norwegian Red cattle identified anti-inflammatory cytokines interleukin 4 and interleukin 13 as putative expression quantitative trait loci, suggesting that S. aureus infection triggers alternative activation of macrophages. Moreover, several classical activation pathways were found, mainly cellular immune response and cytokine signaling pathways, i.e. triggering receptor expressed on myeloid cells 1 (TREM1) and nucleotide-binding and oligomerization domain-like receptor (NLR) pathways. Tumor necrosis factor receptor superfamily member 5 (CD40 ligand) was identified as an upstream regulator which points toward CD40 likely acting as a co-stimulatory receptor during Toll-like receptor 2(TLR2)-mediated inflammatory response of bovine macrophages to S. aureus infection. Furthermore, peptidoglycan was identified as an upstream regulator in the List eQG, which indicates that this bacterial cell-wall component might be pivotal in macrophage intracellular bacterial recognition during early inflammation.ConclusionsHere we have shown that in vitro infection of bovine macrophages with live S. aureus induced both alternative and classical activation pathways. Alternative activation of macrophages may be a mechanism contributing to intracellular persistence of S. aureus in the course of inflammation such as during mastitis in dairy cattle.

Associations between MUC1 gene polymorphism and resistance to mastitis, milk production and fertility traits in Murrah water buffaloes

“…In the present study, allele 1 was associated with higher means for SCC, suggesting a potential relationship between alleles with low number of repeats to high susceptibility to infection in the mammary gland. Undergoing intramammary infection, macrophages, members of the innate immune system, serve as the first line of defense against invading pathogens in the mammary gland and together with the mammary epithelial cells, they release proinflammatory cytokines (such as interleukins and tumour necrosis factor (TNF)) which are signalling molecules for the recruitment and activation of neutrophils to the site of infection (Lewandowska-Sabat et al 2013). Upon activation, neutrophils release enzymes such as myeloperoxidase, which displays cytotoxic oxidant, crucial for the infection resolution (Witko-Sarsat et al 2000).…”

Comparison of the pathogen species-specific immune response in udder derived cell types and their models

“…Experimentally amenable models for macrophages may be established by differentiating bovine blood derived monocytes for several days in vitro (boMdM) [ 35 ]. Global transcriptome profiling of S. aureus infected boMdM suggested [ 37 ] that this infection triggered their alternative activation into a M2 phenotype associated with tissue remodeling rather than the M1 phenotype associated with acute inflammation (see [ 38 ] for a review on macrophage polarization).…”

Differences in virulence between the two more prevalent Staphylococcus aureus clonal complexes in rabbitries (CC121 and CC96) using an experimental model of mammary gland infection

“…These results would support the greater virulence of strains ST121 than strains ST96. Haemolysis (lysis of erythrocytes) is a significant virulence determinant of S. aureus and represents a crucial means for bacteria to acquire iron [14], whereas increased cytotoxicity in PMN and the macrophages of strain ST121 would affect two of the most important defence mechanisms of mammary glands against invading pathogens [51,52].…”