Immunopathology of mastitis: insights into disease recognition and resolution

Significance of metabolic stress, lipid mobilization, and inflammation on transition cow disorders

The incidence and severity of disease in cows is greatest during the transition period, when immune functions are impaired. Intense lipid mobilization is associated with both metabolic and infectious diseases in the transition cow. Significant increases in plasma nonesterified fatty acids contribute to oxidative stress and uncontrolled inflammatory responses. A dysfunctional inflammatory response is the common link between metabolic and infectious diseases around the time of calving. Intervention strategies that can reduce lipid mobilization may improve inflammatory responses and reduce the economic losses associated with health disorders during the transition period.

Nonesterified fatty acids modify inflammatory response and eicosanoid biosynthesis in bovine endothelial cells

Intense lipid mobilization during the transition period in dairy cows is associated with increased disease susceptibility. The potential impact of altered plasma nonesterified fatty acids (NEFA) concentrations and composition on host inflammatory responses that may contribute to disease incidence and severity are not known. The objective of this study was to evaluate if increased NEFA concentrations could modify vascular inflammatory responses in vitro by changing the expression of important inflammatory mediators that are important in the pathogenesis of infectious diseases of transition cows such as mastitis and metritis. Bovine aortic endothelial cells (BAEC) were cultured with different concentrations of a NEFA mixture that reflected the plasma NEFA composition during different stages of lactation. The expression of cytokines, adhesion molecules, and eicosanoids were measured to assess changes in BAEC inflammatory phenotype. Addition of NEFA mixtures altered the fatty acid profile of BAEC by increasing the concentration of stearic acid (C18:0) and decreasing the content of arachidonic acid (C20:4n6c) and other long-chain polyunsaturated fatty acids in the phospholipid fraction. A significant increase also occurred in mRNA expression of cytokine and adhesion molecules that are associated with increased inflammatory responses during the transition period. Expression of cyclooxygenase 2, an important enzyme associated with eicosanoid biosynthesis, was increased in a NEFA concentration-dependent manner. The production of linoleic acid-derived eicosanoids 9- and 13-hydroxyoctadecadienoic acids also was increased significantly after treatment with NEFA mixtures. This research described for the first time specific changes in vascular inflammatory response during in vitro exposure to NEFA mixtures that mimic the composition and concentration found in cows during the transition period. These findings could explain, in part, alterations in inflammatory responses observed during intense lipid mobilization stages such as in the transition period of dairy cows. Future studies should analyze specific mechanisms by which high NEFA concentrations induce a vascular proinflammatory phenotype including the effect of 9 and 13-hydroxyoctadecadienoic acids and other lipid mediators.

Selenium-dependent regulation of oxidative stress and immunity in periparturient dairy cattle

Uncontrolled or impaired immune and inflammatory responses in periparturient dairy cows are associated with increased incidence and severity of infectious diseases. The progressive development of oxidative stress during the transition from late gestation to peak lactation is thought to be a significant underlying factor leading to dysfunctional immune cell responses. Certain trace minerals, such as selenium (Se), can ameliorate oxidative stress and reduce the severity of several economically important diseases in dairy cattle including mastitis and metritis. Many of the health benefits of Se can be attributed to the antioxidant functions of selenoproteins. Changes in selenoprotein activity as a consequence of Se nutritional status can directly alter a number of critical cellular functions involved in the inflammatory response. A better understanding of how Se can optimize immune cell responses may facilitate the design of nutritional regimes that will reduce health disorders during the periparturient period.

Effects of sodium octanoate on innate immune response of mammary epithelial cells during Staphylococcus aureus internalization

Bovine mammary epithelial cells (bMECs) are capable of initiating an innate immune response to invading bacteria. Short chain fatty acids can reduce Staphylococcus aureus internalization into bMEC, but it has not been evaluated if octanoic acid (sodium octanoate, NaO), a medium chain fatty acid (MCFA), has similar effects. In this study we determined the effect of NaO on S. aureus internalization into bMEC and on the modulation of innate immune elements. NaO (0.25–2 mM) did not affect S. aureus growth and bMEC viability, but it differentially modulated bacterial internalization into bMEC, which was induced at 0.25–0.5 mM (~60%) but inhibited at 1-2 mM (~40%). Also, bMEC showed a basal expression of all the innate immune genes evaluated, which were induced by S. aureus. NaO induced BNBD4, LAP, and BNBD10 mRNA expression, but BNBD5 and TNF-α were inhibited. Additionally, the pretreatment of bMEC with NaO inhibited the mRNA expression induction generated by bacteria which coincides with the increase in internalization; only TAP and BNDB10 showed an increase in their expression; it coincides with the greatest effect on the reduction of bacterial internalization. In conclusion, NaO exerts a dual effect on S. aureus internalization in bMEC and modulates elements of innate immune response.

Incidence rates of clinical mastitis among Canadian Holsteins classified as high, average, or low immune responders

The objective of this study was to compare the incidence rate of clinical mastitis (IRCM) between cows classified as high, average, or low for antibody-mediated immune responses (AMIR) and cell-mediated immune responses (CMIR). In collaboration with the Canadian Bovine Mastitis Research Network, 458 lactating Holsteins from 41 herds were immunized with a type 1 and a type 2 test antigen to stimulate adaptive immune responses. A delayed-type hypersensitivity test to the type 1 test antigen was used as an indicator of CMIR, and serum antibody of the IgG1 isotype to the type 2 test antigen was used for AMIR determination. By using estimated breeding values for these traits, cows were classified as high, average, or low responders. The IRCM was calculated as the number of cases of mastitis experienced over the total time at risk throughout the 2-year study period. High-AMIR cows had an IRCM of 17.1 cases per 100 cow-years, which was significantly lower than average and low responders, with 27.9 and 30.7 cases per 100 cow-years, respectively. Low-AMIR cows tended to have the most severe mastitis. No differences in the IRCM were noted when cows were classified based on CMIR, likely due to the extracellular nature of mastitis-causing pathogens. The results of this study demonstrate the desirability of breeding dairy cattle for enhanced immune responses to decrease the incidence and severity of mastitis in the Canadian dairy industry.

Breast, milk and microbes: a complex relationship that does not end with lactation

Until relatively recently, the extent of microbiota presence in the human breast was under-appreciated. A high-throughput sequencing study and culture-based studies have demonstrated the extensive presence of microbes in human milk, with their origin believed to be from the skin, oral cavity and via gut translocation. Since formula milk substitutes do not contain these bacteria, what benefits are denied to these infants? The addition of probiotic bacteria to some infant formula is meant to provide some benefits, but these only contain one species and the dose is relatively high compared with breast milk. Many questions of importance to women's health arise from these findings. When, how and what types of microbes colonize the breast at different stages of a woman's life, including postlactation, and what effect do they have on the host in the short and long term? This article discusses some aspects of these questions.

Ferrous ferric chloride downregulates the inflammatory response to Rhodococcus aurantiacus infection in mice

The healthy drink Pairogen is mainly composed of ferrous ferric chloride water that reportedly changes the status of intracellular water from oxidative to antioxidative. Here, we investigated whether Pairogen affects host immune function in a murine model of granulomatous inflammation in response to Rhodococcus aurantiacus (R. aurantiacus) infection. Longitudinal ingestion of Pairogen markedly improved the survival of infected mice in a concentration-dependent manner. Compared to mice received water, mice that ingested 10-fold-diluted Pairogen displayed rapid bacterial elimination, decreased production of tumor necrosis factor (TNF)-α and interleukin (IL)-6, and high levels of IL-10 in organs during the initial phase of infection. Moreover, histological studies showed significant reduction in the number and size of granulomas as well as amelioration of oxidative stress in the livers of mice ingested 10-fold-diluted Pairogen at 14 d post-infection. These characteristics were further pronounced in first-generation (F1) mice that also ingested 10-fold-diluted Pairogen. Following stimulation with heat-killed R. aurantiacus, the production of TNF-α, IL-6, and IL-10 by macrophages from F1 mice was similar to that detected in vivo, while their gene expression levels in these cells were significantly lower than the levels in macrophages from mice received water. Heat-killed R. aurantiacus also induced the expression of heme oxygenase-1 mRNA in the cells from F1 mice. Taken together, these results indicate that Pairogen contributes to the negative regulation of the immuno-inflammatory response to R. aurantiacus infection in mice by modulating the cellular redox state. Longitudinal ingestion of Pairogen further enhances the defense function in mouse progeny.