Pathogen-dependent induction of cytokines and other soluble inflammatory mediators during intramammary infection of dairy cows

Analysis of Inflammatory and Regulatory Cytokines in the Milk of Dairy Cows with Mastitis: A Comparative Study with Healthy Animals

Bovine mastitis remains a major problem in the global dairy cattle industry. The acute invasion of udder by pathogens induces innate immune response as the first defence mechanism in subclinical and clinical mastitis. The aim of the study was to determine inflammatory and regulatory cytokines IL-2, IL-4, TGF-β1, IL-17A, beta-defensin 3 and IL-10 and their potential changes in milk of dairy cows with subclinical and clinical mastitis, and to compare the findings with healthy animals. Milk samples from 15 holstein Friesian breed cows were used in the study. Cows were divided into three groups based on their health status (5 healthy, 5 subclinical and 5 clinical animals). All samples were tested using immunohistochemistry to evaluate IL-2, IL-4, IL-10, IL17A, TGF-β1 and β-Def 3 proteins. Expression of all proteins was detected in all milk samples. High expression of IL-2, IL-4, IL17A, TGF-β1 was detected in healthy cows' milk and in milk of cows with subclinical and clinical mastitis. However, expression of IL-10 and β-Def 3 in milk samples of healthy cows was significantly higher compared to the milk of cows with subclinical and clinical mastitis (p < .001). IL-10 and β-Def 3 can be considered as informative biomarkers in diagnosis of subclinical and clinical mastitis.

Beta-Glucans Improve the Mammary Innate Immune Response to Endotoxin Challenge in Dairy Ewes

This study evaluated short-term immune responses of dairy ewes supplemented with barley β-glucan (BG) following an intramammary Escherichia coli lipopolysaccharide (LPS) challenge. In the adaptation period, 36 ewes were fed an alfalfa hay diet ad libitum and barley grain cv. Hispanic (3.8% BG). Then, ewes were assigned into three experimental groups: (1) Control (CON), the same previous diet (13.3 g BG/d); (2) high β-glucans barley (HBG), new barley (cv. Annapurna) containing 10% BG (35 g BG/d); (3) intraperitoneally injected (INP) with a 1.4% BG solution dose (2 g BG/ewe). At d 9, all ewes were infused with an E. coli LPS or saline solution in each udder half. After the challenge, rectal temperature (RT), milk yield and composition, somatic cell count (SCC), and plasma interleukins (IL-1α and IL-1β) were monitored daily. The INP treatment revealed a transitory increase in RT and decreased milk yield by 38%. Milk fat, protein, and SCC increased in LPS-treated udders but not by BG treatment. The IL-1α plasma concentration was similar among groups but INP ewes showed a lower IL-1β concentration suggesting a lower inflammatory response. The BG administration appears more effective intraperitoneally than orally, which needs additional study.

Nucleotide sequence variants, gene expression and serum profile of immune and antioxidant markers associated with bacterial diarrhea susceptibility in Barki lambs

BACKGROUND

Despite the fact that diarrhea is more accurately described as a clinical symptom than a disease. Diarrhea is one of the most important issues in ovine medicine, particularly in lambs, and because of high morbidity and mortality rate, sluggish growth performance, and veterinary costs, it is believed to be a major source of economic loss. Salmonella and enterotoxigenic Escherichia coli are the most common and commercially significant agents responsible for diarrhea.

OBJECTIVE

The objective of this study was to monitor the nucleotide sequence variations, gene expression, serum inflammatory and oxidative stress biomarkers in diarrheic lambs. Another aim was to identify different pathotypes and virulence genes of Salmonella and E. coli causing diarrhea.

METHODOLOGY

Blood samples were taken from 50 Barki who were diarrheal and 50 who appeared to be healthy, and then divided in 3 portions, with EDTA added to the first part for CBC, DNA and RNA extraction. The second sample received 5000 I.U. of heparin calcium, and a clean plain tube was used for the third component. The second and third sections were centrifuged to extract serum and plasma until the biochemical and immunological analysis was completed. Fecal samples were collected for bacteriological examination, and the bacteria were identified by PCR analysis. PCR-DNA sequencing was conducted for immune (SELL, JAK2, SLC11A1, IL10, FEZF1, NCF4, LITAF, SBD2, NFKB, TNF-α, IL1B, IL6, LGALS, and CATH1), antioxidant (SOD1, CAT, GPX1, GST, Nrf2, Keap1, HMOX1, and NQO1), and GIT health (CALB1, GT, and MUC2) genes in healthy and diarrheic lambs.

RESULTS

Virulent genetic markers of pathogenic characteristics of E. coli (astA, Vt2e (Stx2e), CFA/I, groES and luxS) and Salmonella (invA, SopB, bcfC and avrA) were detected in all diarrheic lambs. PCR-DNA sequencing of immune, antioxidant and intestinal health genes found eleven single nucleotide polymorphisms (SNPs) linked to either diarrhea resistance or susceptibility in Barki lambs. Transcript levels of immune, antioxidant, and GIT health (CALB1, GT, and MUC2) genes varied between healthy and diarrheic lambs. Nucleotide sequence variation of the genes under inquiry between reference sequences in GenBank and those of the animals under investigation verified all identified SNPs. Significant (P = 0.001) erythrocytosis, neutrophilic leukocytosis, with lymphocytopenia were observed in diarrheic lambs. Significant (P = 0.001) increases in serum IL-1α, IL-1β, IL-6, TNF-α (90.5 ± 1.7, 101.8 ± 1.7, 72.3 ± 6.6, 71.26 ± 4.89 Pg/ml, respectively), serum Fb, Cp, Hp, SAA (230.7 ± 12.4 mg/dl, 6.5 ± 0.07 mg/dl, 2.5 ± 0.09 g/dl, 7.4 ± 0.4 mg/L, respectively), free radicals (MDA, NO), cortisol (6.91 ± 0.18 μg/dl) and growth hormone, with significant (P = 0.001) decreases in serum IL-10 (81.71 ± 1.05 Pg/ml), antioxidants (CAT, GPx), insulin, triiodothyronine (T3) and thyroxine (T4) in diarrheic lambs.

CONCLUSIONS

The study's findings provided credence to the theory that marker-assisted selection (MAS) could be used to predict and prevent diarrhea in Barki sheep by selecting lambs based on SNPs in genes linked to inflammation, antioxidants, and intestinal health. In order to establish an efficient management protocol and determine the most susceptible risk period for disease occurrence, gene expression profiles of the genes under investigation, pro-inflammatory cytokines and acute phase proteins may also be utilized as proxy biomarkers for lamb enteritis.

Positive impacts of Nannochloropsis oculata supplementation on gene expression of immune and antioxidant markers and metabolic profile of Barki sheep in the transition period and lipogenic effects on progeny

Nannochloropsis species should be given priority when it comes to microalgae that should be added to feed since they are suitable for intense culture and have a high concentration of PUFAs (especially EPA), antioxidants, and certain vitamins. This study investigated the possible immune and antioxidant impacts of Nannochloropsis supplementation on Barki ewes during transition period and their newly born lambs. Three weeks prior to the expected time of lambing, the researched ewes were divided into two equal groups of thirty ewes each. The second group, on the other hand, was fed the same base diet as the first group plus 10 g of commercially available Nannochloropsis powder per kg of concentrate, given daily to each ewe's concentrate. Findings revealed that supplementation of ewes with Nannochloropsis significantly up-regulated the expression pattern of immune (NFKB, RANTES, HMGB1, TNF-α, IRF4, TLR7, CLA-DRB3.2, IL1B, IL6, CXCL8, S-LZ, and Cathelicidin), and antioxidant (SOD1, CAT, GPX1, GST, ATOX1, Nrf2 and AhpC/TSA) markers in ewes post-lambing and their newly born lambs. Additionally, mRNA levels of lipogenic (ACACA, FASN SCD, LPL, and BTN1A) markers were significantly up-regulated in lambs from supplemented ewes than control ones. There was a significant increase in the WBCs, Hb, RBc count, serum level of glucose, total protein, triacylglycerol and total cholesterol, GPx, catalase, IL1α and IL6 with significantly decreased serum level of TNF-α and MDA in supplemented ewes after lambing as compared with control ones. There was also a significant increase in WBCs, Hb, RBc count, birth weight and body temperature with significantly decreased in the serum levels of TNF-α and stillbirth of newly born lambs from supplemented ewes as compared to other lambs from control ones.

Effects of a multistrain Bacillus-based direct-fed microbial on gastrointestinal permeability and biomarkers of inflammation during and following feed restriction in mid-lactation Holstein cows

Objectives were to evaluate the effects of a multistrain Bacillus-based (Bacillus subtilis and Bacillus pumilus blend) direct-fed microbial (DFM) on production, metabolism, inflammation biomarkers and gastrointestinal tract (GIT) permeability during and following feed restriction (FR) in mid-lactation Holstein cows. Multiparous cows (n = 36; 138 ± 53 DIM) were randomly assigned to 1 of 3 dietary treatments: (1) control (CON; 7.5 g/d rice hulls; n = 12), (2) DFM10 (10 g/d Bacillus DFM, 4.9 × 109 cfu/d; n = 12) or 3) DFM15 (15 g/d Bacillus DFM, 7.4 × 109 cfu/d; n = 12). Before study initiation, cows were fed their respective treatments for 32 d. Cows continued to receive treatments during the trial, which consisted of 3 experimental periods (P): P1 (5 d) served as baseline for P2 (5 d), during which all cows were restricted to 40% of P1 DMI, and P3 (5 d), a "recovery" where cows were fed ad libitum. On d 4 of P1 and on d 2 and 5 of P2, GIT permeability was evaluated in vivo using the oral paracellular marker Cr-EDTA. As anticipated, FR decreased milk production, insulin, glucagon, and BUN but increased nonesterified fatty acids. During recovery, DMI rapidly increased on d 1 then subsequently decreased (4.9 kg) on d 2 before returning to baseline, whereas milk yield slowly increased but remained decreased (13%) relative to P1. The DFM10 cows had increased DMI and milk yield relative to DFM15 during P3 (10%). Overall, milk lactose content was increased in DFM cows relative to CON (0.10 percentage units), and DFM10 cows tended to have increased lactose yield relative to CON and DFM15 during P3 (8% and 10%, respectively). No overall treatment differences were observed for other milk composition variables. Circulating glucose was quadratically increased in DFM10 cows compared with CON and DFM15 during FR and recovery. Plasma Cr area under the curve was increased in all cows on d 2 (9%) and 5 (6%) relative to P1. Circulating LPS binding protein (LBP), serum amyloid A (SAA), and haptoglobin (Hp) increased in all cows during P2 compared with baseline (31%, 100%, and 9.0-fold, respectively). Circulating Hp concentrations continued to increase during P3 (274%). Overall, circulating LBP and Hp tended to be increased in DFM15 cows relative to DFM10 (29% and 81%, respectively), but no treatment differences were observed for SAA. Following feed reintroduction during P3, fecal pH initially decreased (0.62 units), but returned to baseline levels whereas fecal starch markedly increased (2.5-fold) and remained increased (82%). Absolute quantities of a fecal Butyryl-CoA CoA transferase (but) gene associated with butyrate synthesis, collected by fecal swab were increased in DFM10 cows compared with CON and DFM15 cows. In summary, FR increased GIT permeability, caused inflammation, and decreased production. Feeding DFM10 increased some key production and metabolism variables and upregulated a molecular biomarker of microbial hindgut butyrate synthesis, while DFM15 appeared to augment immune activation.

Innate immune response of bovine mammary epithelial cells in Mycoplasma bovis mastitis using an in vitro model of bovine mammary gland infection

Mycoplasma bovis mastitisis highly contagious and disrupts lactation, posing a significant threat to the dairy industry. While the mammary gland's defence mechanism involves epithelial cells and mononuclear cells (MNC), their interaction with M. bovis remains incompletely understood. In this study, we assessed the immunological reactivity of bovine mammary epithelial cells (bMEC) to M. bovis through co-culture with MNC. Upon co-culture with MNC, the mRNA expression levels of interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor (TNF)-α in bMEC stimulated by M. bovis showed a significant increase compared to monoculture. Additionally, when stimulated with M. bovis, the culture supernatant exhibited significantly higher concentrations of IL-6 and interferon (IFN)-γ, while IL-1β concentration tended to be higher in co-culture with MNC than in monoculture. Furthermore, the mRNA expression levels of toll-like receptor (TLR) 2 in bMEC stimulated with M. bovis tended to increase, and TLR4 significantly increased when co-cultured with MNC compared to monocultures. However, the surface expression levels in bMEC did not exhibit significant changes between co-culture and monoculture. Overall, our research indicates that the inflammatory response of bMEC is increased during co-culture with MNC, suggesting that the interaction between bMEC and MNC in the mammary gland amplifies the immune response to M. bovis in cows affected by M. bovis mastitis.

Microbiome and metabolome analyses of milk and feces from dairy cows with healthy, subclinical, and clinical mastitis

Mastitis is commonly recognized as a localized inflammatory udder disease induced by the infiltration of exogenous pathogens. In the present study, our objective was to discern fecal and milk variations in both microbiota composition and metabolite profiles among three distinct groups of cows: healthy cows, cows with subclinical mastitis and cows with clinical mastitis. The fecal microbial community of cows with clinical mastitis was significantly less rich and diverse than the one harbored by healthy cows. In parallel, mastitis caused a strong disturbance in milk microbiota. Metabolomic profiles showed that eleven and twenty-eight molecules exhibited significant differences among the three groups in feces and milk, respectively. Similarly, to microbiota profile, milk metabolome was affected by mastitis more extensively than fecal metabolome, with particular reference to amino acids and sugars. Pathway analysis revealed that amino acids metabolism and energy metabolism could be considered as the main pathways altered by mastitis. These findings underscore the notable distinctions of fecal and milk samples among groups, from microbiome and metabolomic points of view. This observation stands to enhance our comprehension of mastitis in dairy cows.

Different Immune Control of Gram-Positive and Gram-Negative Mammary Infections in Dairy Cows

In the dairy industry, bovine mastitis represents a major concern due to substantial production losses and costs related to therapies and early culling. The mechanisms of susceptibility and effective response to intra-mammary infections are still poorly understood. Therefore, we investigated innate immunity in acellular bovine skim milk through cytofluorimetric analyses of bacterial killing activity against both Gram-positive and Gram-negative pathogens. Freshly cultured E. coli and S. aureus strains were incubated with colostrum and milk samples at different lactation time points from two groups of cows, purportedly representing mastitis-resistant and mastitis-susceptible breeds; bacterial cells were analyzed for vitality by flow cytometry following incorporation of vital dyes. N-acetyl-β-D-glucosaminidase (NAGase) activity was also investigated in milk and colostrum samples. Our findings revealed that colostrum and milk bacterial killing activity was greater against S. aureus compared to E. coli., with this activity correlated with milk NAGase levels. Furthermore, both killing of S. aureus and NAGase activity were negatively correlated to the elapsed time of lactation. Interestingly, samples from the allegedly mastitis-resistant breed displayed higher bacterial killing and NAGase activities. Our study suggests that diverse control mechanisms are exerted against Gram-positive and Gram-negative pathogens in the mammary glands of cows, probably beyond those already described in the literature.

Effects of topical application of resveratrol on tight junction barrier and antimicrobial compound production in lactating goat mammary glands

In mammary glands, the formation of less-permeable tight junctions (TJs) and the production of antimicrobial compounds like lactoferrin and defensins are important for preventing mastitis. Resveratrol, a polyphenol contained in red grapes, is known to protect mammary epithelial cells (MECs) from oxidative stress; however, oral administration of resveratrol causes a decrease in certain biological processes through conjugation and metabolic conversion. In this study, we determined the beneficial effects of resveratrol on TJs and antimicrobial compounds in cultured goat MECs by adding it to the medium, and in lactating goat mammary glands by topical application for percutaneous absorption. TJ barrier function was evaluated by transepithelial resistance and expression or localization pattern of claudins for culture model in vitro and by somatic cell count, Na+, albumin, and IgG in milk for topical application in vivo. Concentrations of antimicrobial compounds and cytokines were measured using ELISA. Activation of STAT3 was evaluated by Western blotting. Resveratrol strengthened TJ barrier function by upregulating claudin-3 in cultured MECs and topical application to udders reduced somatic cell count, Na+, albumin, and IgG in milk. Resveratrol increased β-defensin and S100A7 levels in cultured MECs and milk. In addition, resveratrol down-regulated cytokine production and STAT3 pathway. These findings suggest that the topical application of resveratrol to udders may be effective in preventing mastitis.

Pathogen and severity-dependent immune responses in bovine mastitis: highlight the dynamics of differential somatic cell count

Immune responses in bovine clinical mastitis (CM) probably differ depending on the causative pathogen and disease severity. The observational study aimed to investigate whether both factors are associated with the dynamics of immune indicators, including somatic cell score (SCS), white blood cell count (WBC), serum albumin/globulin (A/G) ratio, and differential somatic cell count (DSCC). We collected blood and milk samples 0, 3, 5, 7, 14, and 21 days after CM occurred in 38 cows, and grouped the cases (n=49) by disease severity and pathogen. We analyzed data using a linear mixed model considering the effects of pathogens and severity, calculated estimated-marginal means for indicators at each time point, and compared the means between groups. The dynamics of WBC varied depending on both pathogen and severity. WBC changed drastically in either severe or coliform-caused CM, slightly elevated in streptococcal mastitis, but unchanged in staphylococcal mastitis. This possibly relates to the deficiency in innate immune response toward staphylococci. The A/G ratio also changed depending on severity, as it dropped sharply only in severe CM. We observed a non-linear relationship between DSCC and SCS, possibly due to mammary epithelial cells shedding in milk when CM occurred. When cows recovering from Streptococcus dysgalatiae mastitis, DSCC decreased while SCS remained high, suggesting a healing process requiring more macrophages. Our results demonstrate that both the severity and pathogen are associated with immune responses in CM, providing insights into mastitis pathogenesis.

DNA methylation and gene expression changes in mouse mammary tissue during successive lactations: part I - the impact of inflammation

Mastitis is among the main reasons women cease breastfeeding, which leads to them supplementing breast milk with artificial formula. In farm animals, mastitis results in significant economic losses and the premature culling of some animals. Nevertheless, researchers do not know enough about the effect of inflammation on the mammary gland. This article discusses the changes to DNA methylation in mouse mammary tissue caused by lipopolysaccharide-induced inflammation (4 h post-injection of lipopolysaccharide). We analysed the expression of some genes related to mammary gland function, epigenetic regulation, and the immune response. The analysis focused on three comparisons: inflammation during the first lactation, inflammation during second lactation with no history of inflammation, and inflammation during second lactation with previous inflammation. We identified differentially methylated cytosines (DMCs), differentially methylated regions (DMRs), and some differentially expressed genes (DEGs) for each comparison. The three comparisons shared some DEGs; however, few DMCs and only one DMR were shared. These observations suggest that inflammation is one of several factors affecting epigenetic regulation during successive lactations. Furthermore, the comparison between animals in second lactation with and without inflammation, with no inflammation history during first lactation showed a different pattern compared to the other conditions in this experiment. This indicates that inflammation history plays an important role in determining epigenetic changes. The data presented in this study suggest that lactation rank and previous inflammation history are equally important when explaining mammary tissue gene expression and DNA methylation changes.Abbreviations: RRBS, reduced representation bisulfite sequencing; RT-qPCR, real-time quantitative polymerase chain reaction; MEC, mammary epithelial cells; TSS, transcription start site; TTS, transcription termination site; UTR, untranslated region; SINE, short interspersed nuclear element; LINE, long interspersed nuclear element; CGI, CpG island; DEG, differentially expressed gene; DMC, differentially methylated cytosine; DMR, differentially methylated region; GO term, gene ontology term; MF, molecular function; BP, biological process.

Health concerns about possible long-term effects of legally marketed milk and dairy from animals with intramammary infections

Milk and dairy from animals with subclinical mastitis infections are marketable. Mastitis is detected with the somatic cell count (SCC). The EU regulation, among the stricter ones, limits an average of 400,000 somatic cells/ml in milk. Other countries have higher or no thresholds. This level suggests 40% of infected animals, and we indeed consume mastitic milk and dairy. A worldwide prevalence of dairy cattle and buffaloes with subclinical mastitis is estimated to range between 34 and 46%. The current food safety regulations account for mastitis pathogens, their toxins, and the risk of antimicrobial residues, but milk from animals with mastitis contains also compounds that derive from an immune response and inflammation process with biological function for the offspring. To the best of the current knowledge, it cannot be excluded that these compounds do not interfere with human homeostasis and that they do not contribute to redox or cytokine dysregulation that, in turn, could promote certain chronic diseases. These compounds include radicals, oxidation products, nitrosamines, and proinflammatory cytokines with nitrosamines being already recognized as probable carcinogens. Mastitis also alters the composition of caseins, plasmin, and plasminogen activators, which may be related to increased transformation into amyloid with similar characteristics as the fibrils associated with Alzheimer's disease. We should determine whether these bioactive compounds could, alone or in combination, represent any long-term risk to the consumer's health. Adapted regulations and concomitant subsidies for farmers are suggested, for sensing tools that reveal individual SCC and mastitis at milking. Frequent SCC determination is the prerequisite for any mastitis control program.

Influence of a temporary restriction of dietary protein in prepubertal ewe lambs on first lactation milk traits and response to a mammary gland inflammatory challenge

This study evaluated the influence of a temporary nutritional protein restriction (NPR) performed, under commercial conditions, in prepubertal female lambs on first lactation milk production traits and the inflammatory response triggered by an inflammatory challenge of the. From 40 Assaf female lambs, we defined a control group (Cn = 20), which received a standard diet for replacement lambs and the NPR group (n = 20), which received the same diet but without soybean meal between 3 and 5 months of age. About 150 days after lambing, 24 of these ewes (13 NPR, 11C) were subjected to an intramammary infusion of E. coli lipopolysaccharide (LPS). Our dynamic study identified indicator traits of local (SCC) and systemic (rectal T^a, IL-6, CXCL8, IL-10, IL-36RA, VEGF-A) response to the LPS challenge. The NPR did not show significant effects on milk production traits and did not affect the SCC and rectal T^a after the LPS challenge. However, the NPR had a significant influence on 8 of the 14 plasma biomarkers analysed, in all the cases with higher relative values in the C group. The effects observed on VEGF-A (involved in vasculogenesis during mammary gland development and vascular permeability) and IL-10 (a regulatory cytokine classically known by its anti-inflammatory action) are the most remarkable to explain the differences found between groups. Whereas further studies should be undertaken to confirm these results, our findings are of interest considering the current concern about the future world's demand for protein and the need for animal production systems to evolve toward sustainability.

Effect of Holstein genotype on ex-vivo interleukin-1β response to lipopolysaccharide (LPS), lipoteichoic acid (LTA) and heat-killed Gram-negative and Gram-positive bacteria

Effects of Holstein genotype on interleukin-1β response were assessed by ex-vivo stimulation of whole blood with lipopolysaccharide (LPS), lipoteichoic acid (LTA), or sonicated, heat-killed Gram-negative or Gram-positive bacteria. Holstein genotypes were unselected Holsteins (UH, n = 14) not subjected to selection pressures since the mid-1960s and contemporary Holsteins (CH, n = 13). Milk yield of UH and CH cows differ by more than 4500 kg/lactation. Whole blood was mixed with 0.01 µg LPS, 10 µg LTA or 2.5 × 10⁶ CFU of sonicated, heat-killed E. coli, K. pneumoniae, S. marcescens, S. aureus, S. dysgalactiae, or S. uberis per mL of blood and incubated (4 h, 37 °C). Plasma IL-1β was quantified by ELISA and log₁₀-transformed concentrations analyzed with a multivariate linear mixed effects model. Responses to bacteria were greater than responses to LPS or LTA. Responses to LPS, LTA and the Gram-negative stimulants were greater in UH than in CH cows while responses to the Gram-positive bacteria did not differ between Holstein genotypes. In both genotypes, strong correlations were detected among IL-1β responses to the Gram-negative stimulants and to LTA. There were strong correlations among IL-1β responses to the Gram-positive bacteria in CH cows but only between S. aureus and S. dysgalactiae in UH cows. The IL-1β response to S. uberis was highly correlated with responses to all of the Gram-negative stimulants in CH cows but only with E. coli in the UH cows. The reduced immune response could make contemporary cows more susceptible to infection by Gram-negative bacteria. Results confirm selection practices since the mid-1960s have altered immune response in the Holstein, at least to Gram-negative bacteria, and validate the need for additional studies to further evaluate the impacts of these selection practices on immune function in contemporary Holsteins.

In vitro evaluation of ginsenoside Rg1 immunostimulating effect in bovine mononuclear cells

The aim of this study was to evaluate the immunomodulatory effect of ginsenoside Rg1 on mammary secretion and peripheral blood mononuclear cells (MSMC and PBMC, respectively). The mRNA expression of TLR2, TLR4 and selected cytokines were evaluated on MSMC after Rg1 treatment. Also, TLR2 and TLR4 protein expression was evaluated on MSMC and PBMC after Rg1 treatment. Phagocytic activity and capacity, ROS production and MHC-II expression were evaluated on MSMC and PBMC after Rg1 treatment and co-culture with Staphylococcus aureus strain 5011. Rg1 induced mRNA expression of TLR2, TLR4, TNF-α, IL-1β, IL-6 and IL-8 in groups treated with different concentrations and at different times in MSMC, and induced TLR2 and TLR4 protein expression in MSMC and PBMC. Rg1 increased phagocytic capacity and ROS production in MSMC and PBMC. Rg1 increased MHC-II expression by PBMC. However, Rg1 pre-treatment had no effect on cells co-cultured with S. aureus. In conclusion, Rg1 was able to stimulate several sensing and effector activities in these immune cells.

Individual Genomic Loci and mRNA Levels of Immune Biomarkers Associated with Pneumonia Susceptibility in Baladi Goats

The effectiveness of breeding for inherent disease resistance in animals could be considerably increased by identifying the genes and mutations that cause diversity in disease resistance. One hundred and twenty adult female Baladi goats (sixty pneumonic and sixty apparently healthy) were used in this study. DNA and RNA were extracted from blood samples collected from the jugular vein of each goat. SLC11A1, CD-14, CCL2, TLR1, TLR7, TLR8, TLR9, β defensin, SP110, SPP1, BP1, A2M, ADORA3, CARD15, IRF3, and SCART1 SNPs that have been previously found to be associated with pneumonia resistance/susceptibility were identified via PCR-DNA sequencing. The pneumonic and healthy goats differed significantly, according to a Chi-square analysis of the discovered SNPs. The mRNA levels of the studied immune markers were noticeably greater in the pneumonic goats than in the healthy ones. The findings could support the significance of the use of immune gene expression profiles and nucleotide variations as biomarkers for the susceptibility/resistance to pneumonia and provide a practical management technique for Baladi goats. These results also suggest a potential strategy for lowering pneumonia in goats by employing genetic markers linked to an animal’s ability to fend off infection in selective breeding.

Immunological and Oxidative Biomarkers in Bovine Serum from Healthy, Clinical, and Sub-Clinical Mastitis Caused by Escherichia coli and Staphylococcus aureus Infection

The study aimed to investigate the mastitis' emerging causative agents and their antimicrobial sensitivity, in addition to the hematological, biochemical indicators, oxidative biomarkers, acute phase protein (APP), and inflammatory cytokine changes in dairy farms in Gamasa, Dakahlia Governorate, Egypt. One hundred Holstein Friesian dairy cattle with clinical and subclinical mastitis were investigated and were allocated into three groups based on a thorough clinical examination. Escherichia coli and Staphylococcus aureus were found responsible for the clinical and subclinical mastitis in dairy farms, respectively. Multiple drug resistance (MDR) was detected in 100%, and 94.74% of E. coli and S. aureus isolates, respectively. Significantly low RBCs count, Hb, and PCV values were detected in mastitic cows compared with both subclinical mastitic and control groups; moreover, WBCs, lymphocytes, and neutrophil counts were significantly diminished in mastitic cows compared to the controls. Significantly higher levels of AST, LDH, total protein, and globulin were noticed in both mastitic and subclinical mastitic cows. The haptoglobin, fibrinogen, amyloid A, ceruloplasmin, TNF-α, IL-1β, and IL-6 levels were statistically increased in mastitic cows compared to the controls. Higher MDA levels and reduction of TAC and catalase were identified in all the mastitic cases compared to the controls. Overall, the findings suggested potential public health hazards due to antimicrobial resistance emergence. Meanwhile, the APP and cytokines, along with antioxidant markers can be used as early indicators of mastitis.

Immunomodulatory Effects of Bacterial Toll-like Receptor Ligands on the Phenotype and Function of Milk Immune Cells in Dromedary Camel

(1) Toll-like receptors (TLR) are a family of pattern recognition receptors that sense distinct molecular patterns of microbial origin. Although the immune cell composition of camel milk has been recently described, host-pathogen interaction studies in the camel mammary gland are still scarce. The present study aimed to use a whole milk stimulation assay for investigating the modulatory effect of selected Toll-like receptor (TLR) ligands on the phenotype and function of milk immune cells. (2) Methods-camel milk samples (n = 7) were stimulated in vitro with the TLR4 ligand LPS or the TLR2/1 ligand Pam3CSK4, and separated milk cells were evaluated for stimulation-induced shape change, the expression of cell surface markers, phagocytosis, apoptosis, ROS production, and NETosis. Stimulation with PMA was used as a control stimulation. (3) Results-all stimulants induced shape change in milk cells, change in the expression of several cell markers, and increased cell apoptosis and NETosis. In addition, stimulation with Pam3CSK4 and PMA was associated with enhanced ROS production, while only PMA stimulation resulted in enhanced bacterial phagocytosis by milk immune cells. (4) Conclusions-our data indicates selective modulating effects of the TLR ligands LPS and Pam3CSK4 on camel milk phagocytes. These results may have implications for the use of synthetic TLR agonists as immunomodulatory adjuvants of the immune response to intra-mammary vaccines against mastitis pathogens.

Traditional and emerging Fusarium mycotoxins disrupt homeostasis of bovine mammary cells by altering cell permeability and innate immune function

High incidence of traditional and emerging Fusarium mycotoxins in cereal grains and silages can be a potential threat to feed safety and ruminants. Inadequate biodegradation of Fusarium mycotoxins by rumen microflora following ingestion of mycotoxin-contaminated feeds can lead to their circulatory transport to target tissues such as mammary gland. The bovine udder plays a pivotal role in maintaining milk yield and composition, thus, human health. However, toxic effects of Fusarium mycotoxins on bovine mammary gland are rarely studied. In this study, the bovine mammary epithelial cell line was used as an in-vitro model of bovine mammary epithelium to investigate effects of deoxynivalenol (DON), enniatin B (ENB) and beauvericin (BEA) on bovine mammary gland homeostasis. Results indicated that exposure to DON, ENB and BEA for 48 h significantly decreased cell viability in a concentration-dependent manner (P < 0.001). Exposure to DON at 0.39 μmol/L and BEA at 2.5 μmol/L for 48 h also decreased paracellular flux of FITC-40 kDa dextran (P < 0.05), whereas none of the mycotoxins affected transepithelial electrical resistance after 48 h exposure. The qPCR was performed for assessment of expression of gene coding tight junction (TJ) proteins, toll-like receptor 4 (TLR4) and cytokines after 4, 24 and 48 h of exposure. DON, ENB and BEA significantly upregulated the TJ protein zonula occludens-1, whereas markedly downregulated claudin 3 (P < 0.05). Exposure to DON at 1.35 μmol/L for 4 h significantly increased expression of occludin (P < 0.01). DON, ENB and BEA significant downregulated TLR4 (P < 0.05). In contrast, ENB markedly increased expression of cytokines interleukin-6 (IL-6) (P < 0.001), tumor necrosis factor α (TNF-a) (P < 0.05) and transforming growth factor-β (TGF-β) (P < 0.01). BEA significantly upregulated IL- 6 (P < 0.001) and TGF-β (P = 0.01), but downregulated TNF-α (P < 0.001). These results suggest that DON, ENB and BEA can disrupt mammary gland homeostasis by inducing cell death as well as altering its paracellular permeability and expression of genes involved in innate immune function.

Immune mechanisms, resistance genes, and their roles in the prevention of mastitis in dairy cows

Mastitis is one of the most important diseases of the mammary gland. The increased incidence of this disease in cows is due to the breeding of dairy cattle for higher yields, which is accompanied by an increased susceptibility to mastitis. Therefore, the difficulty involved with preventing this disease has increased. An integral part of current research is the elimination of mastitis in order to reduce the consumption of antibiotic drugs, thereby reducing the resistance of microorganisms and decreasing companies' economic losses due to mastitis (i.e. decreased milk yield, increased drug costs, and reduced milk supply). Susceptibility to mastitis is based on dairy cows' immunity, health, nutrition, and welfare. Thus, it is important to understand the immune processes in the body in order to increase the resistance of animals. Recently, various studies have focused on the selection of mastitis resistance genes. An important point is also the prevention of mastitis. This publication aims to describe the physiology of the mammary gland along with its immune mechanisms and to approximate their connection with potential mastitis resistance genes. This work describes various options for mastitis elimination and focuses on genetic selection and a closer specification of resistance genes to mastitis. Among the most promising resistance genes for mastitis, we consider CD14, CXCR1, lactoferrin, and lactoglobulin.

Immune defenses of the mammary gland epithelium of dairy ruminants

The epithelium of the mammary gland (MG) fulfills three major functions: nutrition of progeny, transfer of immunity from mother to newborn, and its own defense against infection. The defense function of the epithelium requires the cooperation of mammary epithelial cells (MECs) with intraepithelial leucocytes, macrophages, DCs, and resident lymphocytes. The MG is characterized by the secretion of a large amount of a nutrient liquid in which certain bacteria can proliferate and reach a considerable bacterial load, which has conditioned how the udder reacts against bacterial invasions. This review presents how the mammary epithelium perceives bacteria, and how it responds to the main bacterial genera associated with mastitis. MECs are able to detect the presence of actively multiplying bacteria in the lumen of the gland: they express pattern recognition receptors (PRRs) that recognize microbe-associated molecular patterns (MAMPs) released by the growing bacteria. Interactions with intraepithelial leucocytes fine-tune MECs responses. Following the onset of inflammation, new interactions are established with lymphocytes and neutrophils recruited from the blood. The mammary epithelium also identifies and responds to antigens, which supposes an antigen-presenting capacity. Its responses can be manipulated with drugs, plant extracts, probiotics, and immune modifiers, in order to increase its defense capacities or reduce the damage related to inflammation. Numerous studies have established that the mammary epithelium is a genuine effector of both innate and adaptive immunity. However, knowledge gaps remain and newly available tools offer the prospect of exciting research to unravel and exploit the multiple capacities of this particular epithelium.

Differential immune response to two Staphylococcus aureus strains with distinct adaptation genotypes after experimental intramammary infection of dairy cows

The aim of this study was to evaluate and compare the ability of two S. aureus strains with different adaptation genotypes (low and high) to the bovine mammary gland (MG) to establish an intramammary infection (IMI) and induce an immune response after an experimental challenge in lactating cows. Two isolates (designated 806 and 5011) from bovine IMI with different genotypic profiles, harboring genes involved in adherence and biofilm production, belonging to different capsular polysaccharide (CP) type, accessory gene regulator (agr) group, pulsotype (PT) and sequence type/clonal complex (ST/CC) were selected. Strains 806 and 5011 were associated with low (nonpersistent-NP) and high (persistent-P) adaptation to the MG, respectively. Strain 806 (NP) was characterized as agr group II, cap5 positive and ST350; strain 5011 (P) agr group I, cap8 positive and CC188. Three groups of clinically healthy cows, 4 cows/treatment group, were inoculated by the intramammary route with strain 806 (NP), strain 5011 (P) and pyrogen-free saline solution. All mammary quarters challenged with strain 806 (NP) developed mild clinical mastitis between 1 and 7 d post inoculation (pi). Quarters challenged with strain 5011 (P) developed a persistent IMI; bacteria were recovered from milk from d 7 pi and up to d 56 pi. In quarters inoculated with strain 806 (NP) the inflammatory response induced was greater and earlier than the one induced by strain 5011 (P), since a somatic cell count (SCC) peak was observed at d 2 pi, while in quarters inoculated with strain 5011 (P) no variations in SCC were observed until d 4 pi reaching the maximum values at d 14 pi; indicating a lower and delayed initial inflammatory response. The highest levels of nitric oxide (NO) and lactoferrin (Lf) detected in milk from quarters inoculated with both S. aureus strains coincided with the highest SCC at the same time periods, indicating an association with the magnitude of inflammation. The high levels of IL-1β induced by strain 806 (NP) were associated with the highest SCC detected (d 2 pi); while quarters inoculated with strain 5011 (P) showed similar IL-1β levels to those found in control quarters. In quarters inoculated with strain 806 (NP) two peaks of IL-6 levels on d 2 and 14 pi were observed; while in quarters inoculated with strain 5011 (P) IL-6 levels were similar to those found in control quarters. The strain 806 (NP) induced a higher total IgG and IgG₁ response; while strain 5011 (P) generated a higher IgG₂ response (even against the heterologous strain). The present study demonstrated that S. aureus strains with different genotype and adaptability to bovine MG influence the local host immune response and the course and severity of the infectious process.

Ochratoxin A and Citrinin Differentially Modulate Bovine Mammary Epithelial Cell Permeability and Innate Immune Function

Frequent detection of mycotoxins ochratoxin A (OTA) and citrinin (CIT) in ruminant feed and feedstuff can be a potential threat to feed safety, animal performance and health. Ineffective biodegradation of these mycotoxins by rumen microflora following ingestion of contaminated feeds can lead to their circulatory transport to tissues such as mammary gland as the result of their biodistribution throughout the body. The bovine mammary epithelium plays a pivotal role in maintaining milk yield and composition and contributes to innate immune defense of the udder. The present study is the first to investigate individual effects of OTA and CIT on barrier and innate immune functions of the bovine mammary epithelium using a bovine mammary epithelial cell line (MAC-T). Results indicated that OTA and CIT exposure for 48 h significantly decreased cell viability in a concentration-dependent manner (p < 0.05). A decrease in transepithelial electrical resistance and increase in paracellular flux of FITC-40 kDa dextran was significantly induced by OTA treatment (p < 0.05), but not by CIT after 48 h exposure. qPCR was performed for assessment of expression of tight-junction proteins, Toll-like receptor 4 (TLR4) and cytokines after 4, 24 and 48 h of exposure. Both OTA and CIT markedly downregulated expression of claudin 3 and occludin (p < 0.05), whereas CIT did not affect zonula occludens-1 expression. Expression of TLR4 was significantly upregulated by OTA (p < 0.001) but downregulated by CIT (p < 0.05) at 48 h. Expression of IL-6, TNF-a and TGF-β was significantly upregulated by OTA (p < 0.05), whereas IL-6 and TGF-β expression was downregulated by CIT (p < 0.01). These results suggest that OTA and CIT could potentially differentially modulate barrier and innate immune functions of mammary epithelium. The present study not only throws light on the individual toxicity of each mycotoxin on bovine mammary epithelium but also lays the foundation for future studies on the combined effects of the two mycotoxins.

Effects of lipoteichoic and arachidonic acids on the immune-regulatory mechanism of bovine mammary epithelial cells using multi-omics analysis

Staphylococcus aureus is one of the most important pathogens causing mastitis in dairy cows. It mainly utilizes the properties of its pathogenic factor, lipoteichoic acid (LTA), to elicit a host-cell inflammatory response and evade the host-cell immune response. Arachidonic acid (AA) has a regulatory role in the inflammatory response, cell metabolism, and apoptosis. The study aimed to establish a cell model by determining the optimal concentration of LTA and AA for cell induction using the Cell Counting Kit−8 assay and the quantitative polymerase chain reaction of interleukin (IL)-1β, IL-2, and IL-6. MAC-T cells were planted in 36 10-cm² culture dishes at a density of 1 × 10⁷ cells per dish. They were treated with LTA for 24 h to constitute the LTA group and with AA for 12 h to constitute the AA group. The cells were pretreated with LTA for 24 h followed by treatment with AA for 12 h to constitute the LTA + AA group. Using proteomic, transcriptomic, and metabolomic analyses, this study determined that LTA can regulate the expression of Actin Related protein 2/3 complex (ARPC)3, ARPC4, Charged Multivesicular Body Protein 3, protein kinase cGMP-dependent, NF-κB Inhibitor Alpha,and other genes to affect cellular metabolism, immune regulation and promote apoptosis. In contrast, AA was observed to regulate the expression of genes such as ARPC3, ARPC4, Charged Multivesicular Body Protein 3, Laminin Gamma 1, Insulin Receptor, Filamin B, and Casein Kinase 1 Epsilon to inhibit cellular apoptosis and promote immune regulation, which provides a theoretical basis for future studies.

Effect of Holstein genotype on ex-vivo cytokine response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) during the periparturient period

Effects of Holstein genotype on innate immune response were assessed with ex-vivo lipopolysaccharide (LPS) and lipoteichoic acid (LTA) stimulation of whole blood from unselected (UH, n = 10) and contemporary (CH, n = 11) Holsteins that differ in production by more than 4,500 kg/lactation. Blood was collected at -14, 7, 28, and 49 days in milk (DIM), mixed with a pathogen-associated molecular pattern (PAMP) molecule (0.01 or 1.0 µg LPS or 10 or 100 µg LTA per mL blood) and incubated (4 h, 37 °C). Plasma cytokines were quantified by ELISA, log₁₀-transformed and analyzed by repeated measures with DIM as the repeated effect. Cytokine responses increased with PAMP dose and decreased as DIM increased. There was a genotype by LPS dose interaction for IL-1β as response to the low dose was greater in UH but did not differ between genotypes for the high dose. The IL-1β response was greater while the IL-6 response to LTA tended to be greater in UH than in CH cows. The more negative energy balance of CH cows did not impact genotype difference in cytokine responses. Results indicate selection since the mid-1960s has decreased ex-vivo, whole blood cytokine response of CH cows to LPS and to LTA.

Gene expression adjustment of inflammatory mechanisms in dairy cow mammary gland parenchyma during host defense against staphylococci

The aim of the study was to identify differences in the expression of splice variants of the PRMT2, LTF and C4A genes in the mammary glands of healthy dairy cows and those infected with staphylococci. An expression study was conducted on 38 Polish Holstein-Friesian dairy cows who were removed from the herd owing to subclinical and chronic mastitic or reproductive issues. Two days before slaughter, milk samples were taken for microbiological analysis and examined for the presence of bacteria. The mammary gland parenchyma samples with a predominance of secretory tissue were taken; these were divided into three groups according to the health status of the mammary gland: H (without pathogenic bacteria in milk), CoNS (with coagulase-negative staphylococci in milk), and CoPS (with coagulase-positive staphylococci in milk). Two of the investigated genes, LTF and C4A, demonstrated variants unequivocally expressed in infected tissue. Two LTF gene variants were found to be associated with cow health status, and with the type of bacteria causing mastitis (CoPS or CoNS). In addition, the expression of C4A isoforms differed with regard to mastitis etiology groups. The comprehensive evaluation of PRMT2 transcript suggested that the gene may also be involved in course of mastitis: two of four PRMT2 transcripts showed increased expression in the mammary gland of the CoPS group compared to controls. The obtained results are important for the knowledge on the etiology of bovine mastitis. The effects of the identified mastitis-relevant splice variants need to be further explored on the protein level to verify the suitability of splice variants and recognize their contribution towards the disease phenotypes and course.

Identification of Inflammatory and Regulatory Cytokines IL-1α-, IL-4-, IL-6-, IL-12-, IL-13-, IL-17A-, TNF-α-, and IFN-γ-Producing Cells in the Milk of Dairy Cows with Subclinical and Clinical Mastitis

In naturally occurring bovine mastitis, effects of infection depend on the host inflammatory response, including the effects of secreted cytokines. Knowledge about the inflammatory and regulatory cytokines in milk cells of free-stall barn dairy cows and in naturally occurring mastitis is lacking as most studies focus on induced mastitis. Hereby, the aim of the study was to determine inflammatory and regulatory cytokines in the milk of dairy cows with subclinical and clinical mastitis. The following examinations of milk samples were performed: differential counting of somatic cells (SCC), bacteriological examination, and immunocytochemical analysis. Mean SCC increased in subclinical and clinical mastitis cases. The number of pathogenic mastitis-causing bacteria on plates increased in subclinical mastitis cases but decreased in clinical mastitis. The inflammatory and regulatory markers in the milk cells of healthy cows showed the highest mean cell numbers (%). In mastitis cases, immunoreactivity was more pronounced for IL-4, IL-6, IL-12, IL-13, IL-17A, TNF-α, and IFN-γ. Data about subclinical and clinical mastitis demonstrate inflammatory responses to intramammary infection driven by IL-1α, IL-4, and IL-17A. Moreover, the host defense response in mastitis is characterized by continuation or resolution of initial inflammation. IL-12 and INF-γ immunoreactivity was recognized to differ mastitis cases from the relative health status.

Graduate Student Literature Review: Systemic mediators of inflammation during mastitis and the search for mechanisms underlying impaired lactation

The negative effect of mastitis on lactation is well established, yet the mechanisms causing reduced milk production in the afflicted dairy cow are not. As one of the major inflammatory diseases in the dairy industry, mastitis has rightly received considerable research interest for decades. However, the focus on distinct, pathologic effects in mastitic glands has largely overlooked systemic effects on noninflamed mammary glands. This is particularly evident in the severe, acute response to the potent inflammatory mediator, lipopolysaccharide (LPS). Whereas secretory cell death, impaired tight junctions, and migration of leukocytes are locally restricted to an inflamed, LPS-challenged gland, changes in milk yield and milk components may be detectable in all mammary glands. Further, these differences extend to the mammary transcriptome. Notably, few transcriptomic studies have been designed to test for effects of systemic mediators of inflammation on gene expression. Relevant changes in the noninflamed mammary gland, identified through biochemical analyses and transcriptional studies, warrant further research. Current evidence suggests proinflammatory cytokines play a role in regulating lactose synthesis, but additional candidates and mechanisms continue to be identified. Ultimately, understanding how systemic mediators of inflammation affect mammary function may lead to the development of interventions that enable more efficient milk production without sacrificing the benefits of inflammation.

Profile of host cell responses to exposure to stressed bacteria in planktonic; dislodged, and intact biofilm mode

The host defense response to microbial challenge emerging from the root canal system leads to apical periodontitis. The aim of this study was to evaluate the expression of inflammatory cytokines and Nitric Oxide (NO) by macrophages after interaction with Enterococcus faecalis in the: plankton and dislodged biofilm mode; intact biofilm mode stimulated by calcium hydroxide (CH), CH and chlorhexidine (CHX) or Triple Antibiotic Paste (TAP). For this purpose, culture of macrophages from monocytes in human peripheral blood (N=8) were exposed to the different modes of bacteria for 24 hours. Subsequently, the cytokines, such as, Tumor Necrotic Factor- alfa (TNF-α), interleukin (IL)-1β, IL-6, IL-10; and NO were quantified by Luminex xMAP and Greiss reaction, respectively. In addition to the potential therapeutic effects of the intracanal medication, their antimicrobial activity against Enterococcus faecalis biofilm were also tested in vitro by confocal microscopy. The experiments` data were analyzed by the Kruskal-Wallis test with the Dunn post hoc test (α < 0.05). Bacteria in dislodged biofilm mode were shown to be more aggressive to the immune system than bacteria in plankton mode and negative control, inducing greater expression of NO and TNF-α. Relative to bacteria in intact biofilm mode, the weakest antimicrobial activity occurred in Group CH. In Groups CH/CHX and TAP the percentage of dead bacteria was significantly increased to the same extent. Interestingly, the biofilm itself did not induce the release of pro-inflammatory cytokines - except for NO - while the biofilm treated with TAP and CH based pastes enhanced the levels of IL-6 and TNF-α; and IL-1 β, respectively. In contrast, the levels of a potent anti-inflammatory (IL-10) were increased in Group TAP.

Expression of cytokines in dairy cattle mammary gland parenchyma during chronic staphylococcal infection

The study aim was to determine the expression of genes potentially related to chronic mastitis at the mRNA and protein levels, viz. chemokine C–C motif receptor 1 (CCR1), C–C motif chemokine ligand 2 (CCL2), C–C motif chemokine ligand 5 (CXCL5), tumor necrosis factor α (TNFα), interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 18 (IL-18), in bovine mammary gland parenchyma. The study examines the differences in expression of selected genes between cows with chronic mastitis caused by coagulase-positive (CoPS) or coagulase-negative staphylococci (CoNS) and those with healthy udders (H). Samples were collected from the udder quarters from 40 Polish Holstein–Friesian cows; 54 of these samples were chosen for analysis based on microbiological analysis of milk taken two days before slaughter. They were categorized into three groups: CoPS (N = 27), CoNS (N = 14) and H (N = 13). The RNA expression was analyzed by RT-qPCR and protein concentration by ELISA. No differences in the mRNA levels of seven genes (TNFα, IL-18, CCR1, IL-1β, CCL2, IL-8, IL-6) and four proteins (TNFα, IL-18, CCR1, IL-1β) were identified between the CoPS and H groups. Higher transcript levels of CXCL5 (p ≤ 0.05) gene were noted in CoPS than in H. Compared to H, higher concentrations of IL-8 and CXCL5 (p ≤ 0.05) were observed in CoPS (0.05 < p < 0.1) and CCL2 (0.05 < p < 0.1) in CoNS, while lower levels of Il-6 were found in CoPS. This may suggest that during chronic mastitis the organism stops producing pro-inflammatory cytokines, probably to protect the host tissues against their damage during prolonged infection.

Naturally Occurring Glycosidases in Milk from Native Cattle Breeds: Activity and Consequences on Free and Protein Bound-Glycans

Little is known about the extent of variation and activity of naturally occurring milk glycosidases and their potential to degrade milk glycans. A multi-omics approach was used to investigate the relationship between glycosidases and important bioactive compounds such as free oligosaccharides and O-linked glycans in bovine milk. Using 4-methylumbelliferone (4-MU) assays activities of eight indigenous glycosidases were determined, and by mass spectrometry and ¹H NMR spectroscopy various substrates and metabolite products were quantified in a subset of milk samples from eight native North European cattle breeds. The results showed a clear variation in glycosidase activities among the native breeds. Interestingly, negative correlations between some glycosidases including β-galactosidase, N-acetyl-β-d-glucosaminidase, certain oligosaccharide isomers as well as O-linked glycans of κ-casein were revealed. Further, a positive correlation was found for free fucose content and α-fucosidase activity (r = 0.37, p-value < 0.001) indicating cleavage of fucosylated glycans in milk at room temperature. The results obtained suggest that milk glycosidases might partially degrade valuable glycans, which would result in lower recovery of glycans and thus represent a loss for the dairy ingredients industry if these activities are pronounced.

Relative virulence of Staphylococcus aureus bovine mastitis strains representing the main Canadian spa types and clonal complexes as determined using in vitro and in vivo mastitis models

Staphylococcus aureus is one of the main pathogens leading to both clinical and subclinical bovine mastitis in dairy cattle. Prediction of disease evolution based on the characteristics of Staph. aureus isolates that cause intramammary infections and understanding the host-pathogen interactions may improve management of mastitis in dairy herds. For this study, several strains were selected from each of the 6 major Canadian spa types associated with mastitis (t267, t359, t529, t605, t2445, and t13401). Adherence to host cells and intracellular persistence of these strains were studied using a bovine mammary gland epithelial cell line (MAC-T). Additionally, relative virulence and host response (cytokines production) were also studied in vivo using a mouse model of mastitis. Whole-genome sequencing was performed on all strains and associations between clonal complex, sequence type, and presence of certain virulence factors were also investigated. Results show that spa type t2445 was correlated with persistence in MAC-T cells. Strains from spa t359 and t529 showed better ability to colonize mouse mammary glands. The exception was strain sa3154 (spa t529), which showed less colonization of glands compared with other t359 and t529 strains but possessed the highest number of superantigen genes including tst. All strains possessed hemolysins, but spa types t529 and t2445 showed the largest diameter of β-hemolysis on blood agar plates. Although several spa types possessed 2 or 3 serine-aspartate rich proteins (Sdr) believed to be involved in many pathogenic processes, most t529 strains expressed only an allelic variant of sdrE. The spa types t605 (positive for the biofilm associated protein gene; bap+) and t13401 (bap-), that produced the largest amounts of biofilm in vitro, were the least virulent in vivo. Finally, strains from spa type t529 (ST151) elicited a cytokine expression profile (TNF-α, IL-1β and IL-12) that suggests a potential for severe inflammation. This study suggests that determination of the spa type may help predict the severity of the disease and the ability of the immune system to eliminate intramammary infections caused by Staph. aureus.

Going further post-RNA-seq: In silico functional analyses revealing candidate genes and regulatory elements related to mastitis in dairy cattle

This study aimed to obtain a better understanding of the regulatory genes and molecules involved in the development of mastitis. For this purpose, the transcription factors (TF) and MicroRNAs (miRNA) related to differentially expressed genes previously found in extracorporeal udders infected with Streptococcus agalactiae were investigated. The Gene-TF network highlighted LOC515333, SAA3, CD14, NFKBIA, APOC2 and LOC100335608 and genes that encode the most representative transcription factors STAT3, PPARG, EGR1 and NFKB1 for infected udders. In addition, it was possible to highlight, through the analysis of the gene-miRNA network, genes that could be post-transcriptionally regulated by miRNAs, such as the relationship between the CCL5 gene and the miRNA bta-miR-363. Overall, our data demonstrated genes and regulatory elements (TF and miRNA) that can play an important role in mastitis resistance. The results provide new insights into the first functional pathways and the network of genes that orchestrate the innate immune responses to infection by Streptococcus agalactiae. Our results will increase the general knowledge about the gene networks, transcription factors and miRNAs involved in fighting intramammary infection and maintaining tissue during infection and thus enable a better understanding of the pathophysiology of mastitis.

An Untargeted Metabolomics Investigation of Milk from Dairy Cows with Clinical Mastitis by 1H-NMR

Mastitis is one of the diseases with the highest incidence in dairy cows, causing huge economic losses to the dairy industry all over the world. The aim of the study was to characterize mastitic milk metabolome through untargeted nuclear magnetic resonance spectroscopy (¹H-NMR). Taking advantage of the high reproducibility of ¹H-NMR, we had the opportunity to provide quantitative information for all the metabolites identified. Fifty-four molecules were characterized, sorted mainly into the chemical groups, namely amino acids, peptides and analogues, carbohydrates and derivates, organic acids and derivates, nucleosides, nucleotides and analogues. Combined with serum metabolomic investigations, several pathways were addressed to explain the mechanisms of milk metabolome variation affected by clinical mastitis, such as tricarboxylic acid cycle (TCA cycle) and phenylalanine, tyrosine and tryptophan biosynthesis. These results provide a further understanding of milk metabolome altered by clinical mastitis, which can be used as a reference for the further milk metabolome investigations.

Effect of polymyxin B on ex vivo tumor necrosis factor-alpha responsiveness of blood leukocytes in Danish Holstein Friesian cows

Whole blood stimulation assay (WBA) with killed gram-positive and gram-negative udder pathogens were used to investigate the interference of the endotoxin-binding antibiotic polymyxin B (PMB) on the ex vivo TNF-α response. Blood samples were collected from first to third lactating dairy cows in their early lactation (<50 days in milk, n = 32) period. The WBA was stimulated with both inactivated bacteria (e.g., dead Escherichia coli, Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis), at a concentration of 2.5 × 10⁶/mL; and pathogen-associated molecular pattern molecules, namely E. coli LPS (10 μg/mL), and S. aureus peptidoglycan (PG, 10 μg/mL). The PMB was added at a concentration of 0, 12.5, 25, 50, 100, and 200 μg/mL to each stimulant, respectively. All bacteria stimulants resulted in an increased TNF-α response compared to the negative control. The PMB affected the TNF-α responses of gram-positive (except S. dysgalactaie), gram-negative bacteria; and bacterial cell wall components at a PMB concentration of 25-50 μg/mL. The LPS and E. coli had similar TNF-α response but PG had a lower TNF-α response than gram-positive bacteria. The doses of PMB (≥ 25 μg/mL) should be used with caution when using different types of pathogens or should be avoided in ex vivo TNF-α studies.

Bovine Immunology: Implications for Dairy Cattle

The growing world population (7.8 billion) exerts an increased pressure on the cattle industry amongst others. Intensification and expansion of milk and beef production inevitably leads to increased risk of infectious disease spread and exacerbation. This indicates that improved understanding of cattle immune function is needed to provide optimal tools to combat the existing and future pathogens and improve food security. While dairy and beef cattle production is easily the world's most important agricultural industry, there are few current comprehensive reviews of bovine immunobiology. High-yielding dairy cattle and their calves are more vulnerable to various diseases leading to shorter life expectancy and reduced environmental fitness. In this manuscript, we seek to fill this paucity of knowledge and provide an up-to-date overview of immune function in cattle emphasizing the unresolved challenges and most urgent needs in rearing dairy calves. We will also discuss how the combination of available preventative and treatment strategies and herd management practices can maintain optimal health in dairy cows during the transition (periparturient) period and in neonatal calves.

Global transcriptomic profiles of circulating leucocytes in early lactation cows with clinical or subclinical mastitis

Bovine mastitis, an inflammatory disease of the mammary gland, is classified as subclinical or clinical. Circulating neutrophils are recruited to the udder to combat infection. We compared the transcriptomic profiles in circulating leukocytes between healthy cows and those with naturally occurring subclinical or clinical mastitis. Holstein Friesian dairy cows from six farms in EU countries were recruited. Based on milk somatic cell count and clinical records, cows were classified as healthy (n = 147), subclinically (n = 45) or clinically mastitic (n = 22). Circulating leukocyte RNA was sequenced with Illumina NextSeq single end reads (30 M). Differentially expressed genes (DEGs) between the groups were identified using CLC Genomics Workbench V21, followed by GO enrichment analysis. Both subclinical and clinical mastitis caused significant changes in the leukocyte transcriptome, with more intensive changes attributed to clinical mastitis. We detected 769 DEGs between clinical and healthy groups, 258 DEGs between subclinical and healthy groups and 193 DEGs between clinical and subclinical groups. Most DEGs were associated with cell killing and immune processes. Many upregulated DEGs in clinical mastitis encoded antimicrobial peptides (AZU1, BCL3, CAMP, CATHL1, CATHL2, CATHL4,CATHL5, CATHL6, CCL1, CXCL2, CXCL13, DEFB1, DEFB10, DEFB4A, DEFB7, LCN2, PGLYRP1, PRTN3, PTX3, S100A8, S100A9, S100A12, SLC11A1, TF and LTF) which were not upregulated in subclinical mastitis. The use of transcriptomic profiles has identified a much greater up-regulation of genes encoding antimicrobial peptides in circulating leukocytes of cows with naturally occurring clinical compared with subclinical mastitis. These could play a key role in combatting disease organisms.

Intramammary Immunisation Provides Short Term Protection Against Mannheimia haemolytica Mastitis in Sheep

Mastitis affects both dairy and meat/wool sheep industries with losses due to reductions in milk quality and quantity, increased treatment costs and restricted lamb growth. Effective vaccines would be important tools for mastitis control. However, the development of vaccines against mastitis has proved challenging due to the failure to target protective immunity to the mammary gland. In order to target responses to the mammary gland, this study tested whether local administration directly into the gland through the teat canal or in the udder skin confers protection against an intramammary infection. In this study, we tested a vaccine that confers protection against respiratory disease caused by Mannheimia haemolytica to determine if it also protects against intramammary infection by the same organism. No evidence of protection was observed in animals that received a subcutaneous immunisation in the udder skin, however, intramammary immunisation provided almost complete protection against an experimental challenge administered 7 days post immunisation but not if the challenge was delivered 14 days post immunisation. To investigate further the nature of this variation in response, the somatic cell count and concentration of cytokines Interleukin-1β, Interleukin-10 and Interleukin-17A was determined in milk over the course of each study. Intramammary immunisation induced an inflammatory response within the mammary gland, characterised by increases in SCC and in the production of cytokines IL-1β, IL-10, and IL-17A. This response was similar to that observed in un-vaccinated control animals post challenge. The SCC and cytokine levels had returned to levels comparable with un-vaccinated controls prior to challenge at both 7 and 14 days post immunisation. The transient nature of the protective effect is consistent with the priming of an innate antibacterial response within the mammary gland which provides protection against challenge at 7 days but is diminished by 14 days post-vaccination. Further studies are planned to determine the nature of the innate immune mechanisms associated with the protective effect described here to determine whether it may be exploited to improve ruminant udder health.

Mechanisms by which mastitis affects reproduction in dairy cow: A review

Reproductive performance is a key factor in determining the profitability of dairy farm, which is affected by many factors such as environment and diseases. Mastitis is a common and important disease, which has caused huge economic losses to the dairy industries worldwide. Mammary gland infection causes immune responses, resulting in the abnormal secretion of cytokines and hormones and abnormal function of the reproductive system such as the ovary, corpus luteum, uterus and embryo. Cows with mastitis have delayed oestrus, decreased pregnancy rate and increased risk of abortion. The adverse effects of mastitis on reproductive performance are affected by many factors, such as occurrence time, pathogen and cow factors. This paper primarily reviews the progress in the effects and mechanisms of mastitis on reproductive performance, with emphasis on maternal transcriptome, genomic analysis, epigenetic modification, microbiota, inflammatory regulation and immune evasion mechanism of mastitis, aiming to provide directions for the prevention and control of mastitis in the future.

MicroRNA expression profile in bovine mammary gland parenchyma infected by coagulase-positive or coagulase-negative staphylococci

MicroRNAs (miRNAs) are short, non-coding RNAs, 21-23 nucleotides in length which are known to regulate biological processes that greatly impact immune system activity. The aim of the study was to compare the miRNA expression in non-infected (H) mammary gland parenchyma samples with that of glands infected with coagulase-positive staphylococci (CoPS) or coagulase-negative staphylococci (CoNS) using next-generation sequencing. The miRNA profile of the parenchyma was found to change during mastitis, with its profile depending on the type of pathogen. Comparing the CoPS and H groups, 256 known and 260 potentially new miRNAs were identified, including 32 that were differentially expressed (p ≤ 0.05), of which 27 were upregulated and 5 downregulated. Comparing the CoNS and H groups, 242 known and 171 new unique miRNAs were identified: 10 were upregulated (p ≤ 0.05), and 2 downregulated (p ≤ 0.05). In addition, comparing CoPS with H and CoNS with H, 5 Kyoto Encyclopedia of Genes and Genomes pathways were identified; in both comparisons, differentially-expressed miRNAs were associated with the bacterial invasion of epithelial cells and focal adhesion pathways. Four gene ontology terms were identified in each comparison, with 2 being common to both immune system processes and signal transduction. Our results indicate that miRNAs, especially miR-99 and miR-182, play an essential role in the epigenetic regulation of a range of cellular processes, including immunological systems bacterial growth in dendritic cells and disease pathogenesis (miR-99), DNA repair and tumor progression (miR-182).

Ex vivo tumor necrosis factor-alpha response of blood leukocytes in Danish Holstein-Friesian cows stimulated by Gram-positive and Gram-negative bacteria isolated from mastitic milk

A whole blood stimulation assay was used to investigate the effects of parity, number of weeks after calving and Gram-positive and Gram-negative bacteria on the ex vivo TNF-α responsiveness of Danish Holstein-Friesian cows of first to third lactation (n = 28). Blood samples were collected in weeks 2, 3, 5 and 8 after parturition and stimulated with Escherichia coli LPS (10 μg/mL), Staphylococcus aureus peptidoglycan (PGN, 10 μg/mL) and dead Escherichia coli, Streptococcus uberis, Staphylococcus aureus, and Streptococcus dysgalactiae at a concentration of 2.5 × 10⁶/mL. The antibiotic polymyxin-B (100 μg/mL) was added to the Gram-positive bacteria to avoid the influence of environmental endotoxin by ELISA test. Overall, parity had no effect, whereas number of weeks after calving altered the TNF-α responsiveness of the majority of the stimulants. Ex vivo, Gram-positive bacteria always resulted in a higher TNF-α response than Gram-negative bacteria with large differences within the individual cows. High correlations were found within the Gram-negative stimulants panel (r = 0.83) and within the Gram-positive (r = 0.81 to 0.86) stimulants panel except PGN. The higher TNF-α responsiveness by Gram-positive bacteria is in agreement with in vitro studies in human but in contrast to the in vivo TNF-α responsiveness in bovine udder.

Lipopolysaccharide and lipoteichoic acid influence milk production ability via different early responses in bovine mammary epithelial cells

Lipopolysaccharide (LPS) and lipoteichoic acid (LTA) are cell wall components of Escherichia coli and Staphylococcus aureus, which cause clinical and subclinical mastitis, respectively. However, the reason of the difference in symptoms by pathogen type remains unclear. In this study, the influence of LPS and LTA on early response and milk production in lactating bovine mammary epithelial cells (BMECs) was comparatively investigated. The results showed that LPS decreased the secretion of β-casein, lactose, and triglycerides, whereas LTA decreased the secretion of lactose and triglycerides but increased lactoferrin production without any influence on β-casein secretion. In addition, the influence of milk lipid droplet size in BMECs and gene expression related to milk fat synthesis was different between LPS and LTA. LPS increased the gene expression of interleukin (IL)-1β, tumor necrosis factor-α, and IL-8 through the activation of the nuclear factor-κB (NF-κB), p38, and c-Jun N-terminal kinase pathways, whereas LTA increased IL-1β and CC chemokine ligand 5 expression through the activation of the NF-κB pathway. Moreover, these cytokines and chemokines differently affected the milk production ability of BMECs. These results suggested that the pathogen-specific symptoms may be related to the differences in the early response of BMECs to bacterial toxins.

Proteomic 2D-DIGE Analysis of Milk Whey from Dairy Cows with Staphylococcus aureus Mastitis Reveals Overexpression of Host Defense Proteins

Bovine mastitis remains a primary focus of dairy cattle disease research due to its considerable negative economic impact on the dairy industry. Subclinical mastitis (SCM), commonly caused by Staphylococcus aureus, lacks overt clinical signs and the diagnosis is based on bacteriological culture and somatic cell counts of milk, both of which have limitations. The main objective of this study was to identify, characterize and quantify the differential abundance of milk whey proteins from cows with S. aureus SCM compared to whey from healthy cows. Using two-dimensional differential gel electrophoresis (2D-DIGE) coupled with liquid chromatography and tandem mass spectrometry, 28 high-abundant proteins were detected in whey from mastitic milk, 9 of which had host defense functions. These included acute phase proteins involved in innate immunity and antimicrobial functions (e.g., serotransferrin, complement C3, fibrinogen gamma-B chain and cathepsin B), and proteins associated with the immune response to pathogens (e.g., polymeric immunoglobulin receptor-like protein, MHC class I antigen and beta-2-microglobulin). These results provide a unique 2D map of the modulated milk proteome during S. aureus mastitis. The broader importance is that the identified proteins, particularly those with host-defense biological functions, represent potential candidate biomarkers of subclinical mastitis in dairy cows.

Epidemiology and Classification of Mastitis

Simple Summary

Farmers should focus on milk quality over quantity. However, in some situations, more attention is focused on the amount of milk produced. In the long term, this approach might represent an important economic cost as it leads to increased incidence of mastitis. Mastitis affects herds in all countries and is the most economically burdensome disease encountered by dairy farmers. The current review focuses on the main pathogens that cause this inflammation and their prevalence as well as strategies to prevent their proliferation. We discuss economic loss, with the goal of demonstrating that prevention is always better than disease management.

Abstract

Farmers should focus on milk quality over quantity because milk that contains unsuitable components and/or antibiotic residues, or has a high somatic cell count, cannot be used in food production and thereby results in reduced milk yield. One of the main problems affecting the ultimate milk yield of dairy cows is mastitis. This disease is the most serious economic and health problem associated with dairy cow herds and is a major reason for excessive culling. Therefore, many studies have addressed this problem to further our understanding of the agents causing mastitis and their classification and virulence factors. This review summarizes the current knowledge regarding mastitis prevalence, the characteristics of its main causative agents, and the effects of mastitis on dairy production. The review also intends to provide guidance for future studies by examining external effects influencing dairy production in cows under field conditions.

Outcome prediction from the first examination in clinical mastitis using ultrasonography in dairy cows

The aim of this study was to examine whether ultrasonography can be used to predict the outcome of clinical mastitis in dairy cows. Forty-seven mastitic quarters of Holstein-Friesian cows were examined using ultrasonography at the time of the first examination. In mastitic mammary tissue, three sonographic signs indicating tissue abnormality were found: a hyperechoic spot in the parenchyma area, structural changes to the milk duct, and non-homogeneous parenchyma. Logistic regression was used to evaluate whether the abnormal findings in the sonographic images can be used to predict the outcome of clinical mastitis. The outcomes of clinical mastitis were defined by the return, or failure to return, to marketable milk production. The sonogram finding of non-homogeneous parenchyma in the first examination did predict the outcome of clinical mastitis, whereas the type of systemic symptoms (severe or moderate) was not a predictor in this regression model. Therefore, ultrasound examinations of mammary glands in the first examination could be a useful method for predicting outcome of clinical mastitis. There is an economic benefit if ultrasound examination in first examination helps in the decision of whether or not to treat the mastitic cows.

Graduate Student Literature Review: Understanding the genetic mechanisms underlying mastitis

Mastitis is the costliest disease facing dairy producers today; consequently, it has been the subject of substantial research focus. Efforts have evolved from an initial focus on understanding the etiology of intramammary infections to the application of preventative measures, including attempts to breed cows that are resistant to infection. However, breeding for resistance to infection has proven difficult, given the complexity of the disease and the high expense associated with assembling high-quality genotypes and phenotypes. This review provides a brief background on mastitis; illustrates current understanding of the genetics influencing mastitis and the application of this knowledge; and discusses challenges and limitations in understanding these mechanisms and applying these findings to genetic improvement strategies.

Intramammary inoculation with lactic acid bacteria at dry-off triggers an immunomodulatory response in dairy cows

The use of antibiotics to prevent bovine mastitis is responsible for the emergence and selection of resistant strains. Lactic acid bacteria (LAB) could be introduced into animal feed as an alternative prevention method that would bypass the risk of resistance development. In previous research, we demonstrated that two probiotic LAB strains isolated from bovine milk were capable of stimulating the production of antibodies and the host's immune cellular response in the udder. The present study aimed to elucidate whether the antibodies of animals inoculated with these strains were able to increase phagocytosis by neutrophils and inhibit the growth of different mastitis-causing pathogens. Moreover, the effect of LAB on the expression of pro-inflammatory cytokines was assessed. Ten animals were inoculated intramammarily with 10⁶ cells of the two strains at dry-off. The blood serum was tested for its ability to opsonize bovine mastitis pathogens, the in vitro bactericidal activity of bovine blood and milk against these pathogens was determined, and cytokine mRNA expression was quantified in milk somatic cells. The inoculated animals did not show abnormal signs of sensitivity to the LAB. Their blood serum significantly enhanced the phagocytosis of Staphylococcus spp. and the LAB. Escherichia coli and Streptococcus uberis were inhibited by the milk serum but not the blood serum, whereas Staphylococcus aureus and Staphylococcus haemolyticus were inhibited by both. In regard to cytokine expression, interleukin (IL)-1β increased markedly for up to 4 h post-inoculation, and an increase in IL-8 was observed 4, 12 and 24 h after inoculation. Tumour necrosis factor-α mRNA increased 1 and 2 h after inoculation and a significant difference was registered at 6 h for interferon-γ. This rapid immunomodulatory response shows that inoculating animals with LAB at dry-off, when they are especially susceptible, could be a useful strategy for the prevention of bovine mastitis.

Concentrations of Acute-Phase Proteins in Milk from Cows with Clinical Mastitis Caused by Different Pathogens

Among the new diagnostic methods for mastitis detection under development, milk acute-phase proteins (APPs) are receiving special attention. The study aimed to compare the profile of milk APPs from cows with natural clinical mastitis caused by distinct pathogens. The concentrations of haptoglobin (Hp), serum amyloid A (SAA), alpha-1-acid glycoprotein (AGP), and C-reactive protein (CRP) were measured by Spatial Proximity Analyte Reagent Capture Luminescence (SPARCL). Each APP was compared across the pathogens causing mastitis. The APPs differed statistically (p < 0.05) among the pathogens causing udder infection. There were significant and positive correlations among the concentration profile, for each pathogen, in three of four APPs studied. It can be concluded that the pathogen causing mastitis could modify the profile of release of the APPs in milk. The profile of Hp, AGP, and CRP demonstrated significant correlation, indicating that the three APPs are suggested as biomarkers, in milk, for bovine mastitis.

Proteomic analysis of bovine mammary epithelial cells after in vitro incubation with S. agalactiae: potential biomarkers

Streptococcus agalactiae is one of the causative agents of subclinical mastitis, a common disease of dairy cows that causes great economic losses in the industry worldwide. It is thought that pathology is mainly due to inflammatory damage of bovine mammary epithelial cells (bMECs); however, the mechanism by which S. agalactiae damages the bMECs is not clear. The aim of this study was to evaluate the inflammatory effects of S. agalactiae on bMECs and the resulting changes in protein profiles. The bMECs were incubated with S. agalactiae for different times and assayed for cell viability by MTT assay, apoptosis by annexin V and propidium iodide dual staining, and morphological and ultrastructural changes by scanning and transmission electron microscopy. Quantitative real-time PCR was used to determine the effect of S. agalactiae on expression of mRNA of inflammatory factors in bMECs and protein levels were quantitated by liquid chromatography/mass spectrometry. Exposure to S. agalactiae significantly decreased the cell viability and triggered apoptosis, as well as up-regulating TNF-α, IL-1β and IL-6 mRNA, and inhibiting IL-8 expression. S. agalactiae also induced morphological and ultrastructural changes. Furthermore, we identified 325 up-regulated and 704 down-regulated proteins in the treated vs control group. All significant differentially expressed proteins (DSEPs) were classified into three major areas by function: biological processes, cellular components and molecular functions. These differentially expressed proteins included enzymes and proteins associated with various metabolic processes and cellular immunity. Pathway enrichment analysis showed that eight down-regulated signaling pathways were significantly enriched. Exposure to even subclinical levels of S. agalactiae can lead to inflammation and bMEC damage. Our data suggest some possible molecular mechanisms for the harmful effects of subclinical mastitis in dairy cows.