Project description:Mastitis is one of the most prevalent and economically important diseases of dairy animals. The disease is caused by ascending bacterial infection through the teat canal. Among the most common mastitis-causing bacteria are gram-negative coliforms, gram-positive streptococci and staphylococci, and mycoplasma. The most prominent cellular hallmark of acute mammary infection is a massive recruitment of blood neutrophils into the tubular and alveolar milk spaces. The complex biological processes of leukocyte recruitment, activation, adhesion, and migration in the mammary gland remain largely elusive to date. While field research of mastitis in dairy animals contributed a lot to the development of mitigation, control, and even eradication programs, little progress was made toward understanding the molecular mechanisms underlying the pathogenesis of the disease. We report here experimental mastitis model systems in lactating mice challenged with field strains of common udder pathogens in dairy cows. We used these model systems to apply recently developed multiplex gene expression technology (Nanostring nCounter), which enabled us to study the expression of over 700 immune genes. Our analysis revealed a core of 100 genes that are similarly regulated and functionally or physically interacting in E. coli, M. bovis and Strep uberis murine mastitis. Common significantly enriched gene sets include TNFɑ signaling via NFkB, Interferon gamma and alpha response, and IL6-JAK-STAT3 signaling. In addition, we show a significantly enriched expression of genes associated with neutrophil extracellular traps (NET) in glands challenged by the three pathogens. Ligand-receptor analysis revealed interactions shared by the three pathogens, including the interaction of the cytokines IL1β, IL1ɑ, and TNFɑ with their receptors, and proteins involved in immune cell recruitment such as complement C3 and ICAM1 (with CD11b), chemokines CCL3 and CCL4 (with CCR1), and CSF3 (with CSF3R). Taken together, our results show that mammary infection with E. coli, M. bovis and Strep uberis culminated in the activation of a conserved core of immune genes and pathways including NET formation.

Project description:Mastitis remains one of the most prevalent and costly diseases impacting the dairy industry worldwide. Escherichia coli is an environmental bacterium that frequently causes intramammary infections, the outcome of which depends on the capacity of the host to recognize and clear the bacterial pathogen. E. coli intramammary infection elicits localized and systemic responses, some of which have been characterized in mammary secretory tissue. However, nothing is known about early transcriptome-wide responses to infection that occur within regions of the teat and mammary parenchyma. Therefore, the objective of the current study was to use microarray analysis to characterize gene expression patterns and process networks that become activated in different regions of the mammary gland during the acute phase of experimentally induced intramammary infection with E. coli. Tissues evaluated were from Furstenberg’s rosette, teat cistern, gland cistern, and lobulo-alveolar regions of control and infected mammary glands, 12 and 24 h after bacterial (or control) infusions. For selected genes, quantitative RT-PCR was performed to confirm the microarray findings (Toll-like receptors; TLR1, TLR2, TLR4, TLR6) and evaluate the correspondence between mRNA level in tissues and protein level in milk (interleukin 8, tumor necrosis factor-alpha, haptoglobin, lipopolysaccharide-binding protein). The main networks activated by E. coli infection pertained to immune and inflammatory response, with marked induction of genes encoding proteins that function in chemotaxis, leukocyte activation and signaling. Genomic response was greatest in tissues of the teat and gland cisterns at 12 h post-infection, while tissue of the lobulo-alveolar region responded only, and most strongly of the regions, 24 h following the infection. Up regulation of TLR2, TLR4, IL8, TNF-alpha and bactericidal/permeability-increasing protein peaked at 12 h post infection in tissues of the teat and in the gland cistern, while the highest level of lipopolysaccharide-binding protein was reached at 24 h in the lobular alveoli region of infected quarters. Very few genes were down–regulated within the timeframe of this study. Similar genetic networks were impacted in all regions during early phases of E. coli intramammary infection, although regional differences throughout the gland were noted. Importantly, the tissues of the teat, which are first to encounter invading bacteria during a natural infection, responded rapidly and intensely, suggesting an important sentinel function for this region. Both resident mammary cells and infiltrating immune cells likely play an important role in recognition of pathogens and production of inflammatory mediators during mastitis. Three healthy lactating Holstein cows were used in this study. All mammary glands were bacteria-free. Immediately following the morning milking, 4 mL of E. coli suspension (100 colony forming units/mL) were infused into one mammary gland of the udder and the contralateral gland was infused with PBS (control gland). After the PM milking 12 h later, the remaining ipsilateral quarter was infused with E. coli. Cows were euthanized 24 h after initial infusions and tissues were collected from 4 regions of each mammary gland: Furstenburg’s rosette, teat cistern, gland cistern and lobuloalveolar regions. Tissues were snap frozen in liquid nitrogen, stored at -80C until processing.

Project description:Mastitis remains one of the most prevalent and costly diseases impacting the dairy industry worldwide. Escherichia coli is an environmental bacterium that frequently causes intramammary infections, the outcome of which depends on the capacity of the host to recognize and clear the bacterial pathogen. E. coli intramammary infection elicits localized and systemic responses, some of which have been characterized in mammary secretory tissue. However, nothing is known about early transcriptome-wide responses to infection that occur within regions of the teat and mammary parenchyma. Therefore, the objective of the current study was to use microarray analysis to characterize gene expression patterns and process networks that become activated in different regions of the mammary gland during the acute phase of experimentally induced intramammary infection with E. coli. Tissues evaluated were from Furstenberg’s rosette, teat cistern, gland cistern, and lobulo-alveolar regions of control and infected mammary glands, 12 and 24 h after bacterial (or control) infusions. For selected genes, quantitative RT-PCR was performed to confirm the microarray findings (Toll-like receptors; TLR1, TLR2, TLR4, TLR6) and evaluate the correspondence between mRNA level in tissues and protein level in milk (interleukin 8, tumor necrosis factor-alpha, haptoglobin, lipopolysaccharide-binding protein). The main networks activated by E. coli infection pertained to immune and inflammatory response, with marked induction of genes encoding proteins that function in chemotaxis, leukocyte activation and signaling. Genomic response was greatest in tissues of the teat and gland cisterns at 12 h post-infection, while tissue of the lobulo-alveolar region responded only, and most strongly of the regions, 24 h following the infection. Up regulation of TLR2, TLR4, IL8, TNF-alpha and bactericidal/permeability-increasing protein peaked at 12 h post infection in tissues of the teat and in the gland cistern, while the highest level of lipopolysaccharide-binding protein was reached at 24 h in the lobular alveoli region of infected quarters. Very few genes were down–regulated within the timeframe of this study. Similar genetic networks were impacted in all regions during early phases of E. coli intramammary infection, although regional differences throughout the gland were noted. Importantly, the tissues of the teat, which are first to encounter invading bacteria during a natural infection, responded rapidly and intensely, suggesting an important sentinel function for this region. Both resident mammary cells and infiltrating immune cells likely play an important role in recognition of pathogens and production of inflammatory mediators during mastitis.

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Expression data from mouse model of Ecoli mastitis

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