Development of an ELISA for bovine IL-10

Impact of an Injectable Trace Mineral Supplement on the Immune Response and Outcome of Mannheimia haemolytica Infection in Feedlot Cattle

The study aimed to assess the impact of injectable trace mineral ("ITM"; Multimin90; Fort Collins, CO) supplementation on bacterial infection in cattle. Angus-crossbred steers (n = 32) were organized into two blocks by initial body weight. Steers were maintained on a ryelage and dry-rolled corn-based growing diet without supplementation of Zn, Cu, Mn, and Se for the duration of the study. The steers were transported 6 h, then randomized into three treatment groups: control received sterile saline ("CON"), ITM administered 1 day after transport (6 days before infection, "ITMPRE"), and ITM administered 2 days post infection (dpi) concurrent with antibiotic treatment ("ITMPOST"). Steers were infected with Mannheimia haemolytica on day 0, and all were treated with tulathromycin at 2 dpi. Plasma levels of Zn, Cu, and Se did not differ among treatments (P ≥ 0.74). Liver Se was higher in ITMPRE at 2 dpi (P < 0.05), and both ITM groups had higher liver Se at 5 dpi (P < 0.05) compared to CON. A time × treatment interaction was detected for liver Cu (P = 0.02). Clinical scores were lower (P < 0.05) in ITMPRE on 1 and 8 dpi and ITMPOST on 8 dpi compared to CON. Thoracic ultrasonography scores were lower in ITMPRE at 2 dpi compared to CON (P < 0.05) and ITMPOST (P < 0.1). No treatment effects (P > 0.10) were observed for bacterial detection from bronchoalveolar lavage (BAL) or nasopharyngeal swabs. At 5 dpi, both ITMPRE and ITMPOST showed higher frequencies of γδ T cells and NK cells in BAL compared to CON (P < 0.05). Before infection, leukocytes from ITMPRE steers produced more IL-6 (P < 0.01) in response to stimulation with the TLR agonist, Pam3CSK4. Use of ITM may be an effective strategy for improving disease resistance in feedlot cattle facing health challenges.

Optimization of a bovine cytokine multiplex assay using a new bovine and cross-reactive equine monoclonal antibodies

Cytokines are important markers for immune activation, regulation, and homeostasis. The lack of monoclonal antibodies (mAbs) and sensitive assays to evaluate cytokine secretion has hindered research of bovine inflammation and immune regulation. We recently developed a fluorescent bead-based multiplex assay (multiplex assay) for bovine IL-10, TNF-α, and IFN-γ. Although the original assay covers a broad concentration range for the 3 targets, analytical sensitivity for IL-10 and IFN-γ could be improved to facilitate detection of these cytokines in their physiological low pg/mL range. To optimize the multiplex assay, we generated a new bovine IL-10 mAb and explored its use for the detection of intracellular and secreted bovine IL-10. The new bovine IL-10 mAb 130 recognized recombinant bovine IL-10 fusion protein and did not react with the fusion protein tag, or the TNF-α and IFN-γ standards in the multiplex assay. For improving IFN-γ detection, we explored cross-reactivity of anti-equine IFN-γ mAbs by intracellular staining of bovine stimulated peripheral blood mononuclear cells (PBMC). Equine IFN-γ mAb 3 showed excellent cross-reactivity with bovine IFN-γ by intracellular detection. Adding IL-10 mAb 130 and IFN-γ mAb 3 to the bovine multiplex assay substantially improved the analytical sensitivity with lower limits of detection in the low pg/mL range for all analytes. The detection ranges for the optimized multiplex assay were determined as 2 - 134,000 pg/mL for IL-10, 8 - 127,000 pg/mL for IFN-γ, and 12 - 193,000 pg/mL for TNF-α. The assay was next used to measure cytokine concentrations in cell culture supernatants from PBMC stimulated in plasma from whole blood stimulation to confirm native IL-10, TNF-α, and IFN-γ recognition and to explore the upper detection limits of the assay. In PBMC stimulation with a mix of phorbol myristate acetate (PMA) and ionomycin resulted in highest cytokine concentrations, while in plasma from whole blood stimulation, highest concentrations were observed in samples stimulated with a mix of lipopolysaccharide (LPS), phytohemagglutinin (PHA), and the TLR-2/6 agonist Pam2Csk4. PBMC and whole blood stimulation protocols showed that the optimized multiplex assay covers a wide linear detection range for measuring cytokine concentrations in bovine samples. For whole blood stimulation, a cocktail of pathogen associated molecular patterns elicited a stronger cytokine response than a mix of PMA and ionomycin, but response varied considerably between individual cattle. In conclusion, optimizing the bovine cytokine assay with new reagents improved the lower detection limits and widened the linear detection ranges while lowering the background of the multiplex assay.

Genetic profile of adaptive immune traits and relationships with parasite resistance and productivity in Scottish Blackface sheep

Gastrointestinal (GI) parasites cause significant production losses in grazing ruminants which can be mitigated by breeding animals resistant to disease. Lymphocyte cytokine production and parasite-specific Immunoglobulin A (IgA) are adaptive immune traits associated with immunity to GI parasites. To explore the utility of these traits for selective breeding purposes, this study estimated the genetic parameters of the immune traits in sheep and assessed their relationship with disease and productivity traits. Whole blood stimulation assays were performed on 1 040 Scottish Blackface lambs at two months of age in 2016-2017. Blood was stimulated with either pokeweed mitogen (PWM), a non-specific activator of lymphocytes, and Teladorsagia circumcincta (T-ci) larval antigen to activate parasite-specific T lymphocytes. The type of adaptive immune response was determined by quantifying production of cytokines interferon-gamma (IFN-γ), interleukin (IL)-4, and IL-10, which relate to T-helper type (Th) 1, Th2 and regulatory T cell responses, respectively. Serum T-ci specific IgA was also quantified. Heritabilities were estimated for each immune trait by univariate analyses. Genetic and phenotypic correlations were estimated between different immune traits, and between immune traits vs. disease and productivity traits that were recorded at three months of age. Disease phenotypes were expressed as faecal egg counts (FEC) of nematode parasites (Strongyles and Nematodirus), faecal oocyst counts (FOC) of coccidian parasites, and faecal soiling score; production was measured as lamb live weight. Significant genetic variation was observed in all immune response traits. Heritabilities of cytokine production varied from low (0.14 ± 0.06) to very high (0.77 ± 0.09) and were always significantly greater than zero (P < 0.05). IgA heritability was found to be moderate (0.41 ± 0.09). Negative associations previously identified between IFN-γ production and FOC, and IL-4 production and strongyle FEC, were not evident in this study, potentially due to the time-lag between immune and parasitology measures. Instead, a positive genetic correlation was found between FOC and PWM-induced IFN-γ production, while a negative genetic correlation was found between FOC and T-ci induced IL-10. Live weight was negatively genetically correlated with IFN-γ responses. Overall, IFN-γ and IL-4 responses were positively correlated, providing little evidence of cross-regulation of Th1 and Th2 immunity within individual sheep. Furthermore, T-ci specific IgA was highly positively correlated with PWM-induced IL-10, indicating a possible role for this cytokine in IgA production. Our results suggest that while genetic selection for adaptive immune response traits is possible and may be beneficial for parasite control, selection of high IFN-γ responsiveness may negatively affect productivity.

Role of hazelnut skin supplementation on plasma antioxidant status and cytokine profile in growing lambs

In this study, the effect of hazelnut skin dietary supplementation on antioxidant status and cytokine profile was evaluated in growing lambs. A total of 22 male lambs at the age of 2 months, balanced for their initial live weight (15.33 ± SD 1.79 kg), were selected and allocated into two experimental groups: the control group (CON) receiving a maize-barley-based concentrated diet, and the hazelnut group (HS) receiving supplementation with hazelnut skin (150 g/kg on the dry matter) as a maize substitute for the concentrate diet. The experiment lasted for 56 days. Peripheral blood was collected at 7, 35, and 56 days of the experiment. The free radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, the total antioxidant capacity assay (TAC), the reactive oxygen species (ROS), and reactive nitrogen species (RNS) were determined in plasma. The secretion of IL-1β, IL-6, and IL-10 cytokines was also determined by ELISA. The DPPH was affected by the interaction between feeding strategy and time of sampling (p = 0.039) with a higher level of DPPH at 7 days in the HS group than the CON group. The time of sampling affected the levels of plasma TAC (p = 0.016), while the ROS/RNS levels showed a higher value in the HS group (p < 0.001), on average. The antioxidant/oxidant index, which combines the TAC and the ROS/RNS levels, was not affected by the inclusion of hazelnut skin in the diet (p = 0.394). The cytokine profile showed a lower IL-6 secretion at both 35 and 56 days than at 7 days, on average. Furthermore, the feeding treatment affected the IL-1β level, showing a lower level in the HS group than in the CON group on average. Lambs from the HS group had higher IL-10 plasma levels than the CON group at 7 days of the experiment. The present data highlight an antioxidant effect and a modulatory role in the cytokine profile of HS supplementation in growing lambs.

Melatonin Administration to Pregnant Ewes for Coccidiosis Control in Their Offspring

In livestock research, there has been a growing interest in the impact of melatonin on both health and disease conditions. The hypothesis of the present study was that melatonin treatment prenatally could support the immune competence and growth of experimentally infected lambs. This is the first study that aimed to investigate the impact of melatonin administration throughout pregnancy on immunity and oocyst excretion of pre-partum ewes and their offspring after experimental infection with Eimeria species. Thirty pregnant ewes were allocated into five equal groups, ΚΜ, ΚC, CM, CC, and NC, and gave birth to 47 lambs. Ewes of the KM and KC groups were orally challenged with a cocktail of Eimeria-sporulated oocysts (mainly consisting of Eimeria ovinoidalis), on day 120 of pregnancy, as well as all the lambs at the age of 5-9 days apart from those born from the NC group (environmental control). Fecal samples were collected from all ewes before infection and at parturition and from all lambs 14 times (S0-S13), before infection and during the following 8 weeks, for counting oocysts per gram of feces (OPG). Immunoglobulin (IgG) and cytokine (IL-1β, IL-6, IL-10, IFN-γ) levels were determined in ewes' plasma collected before infection and at parturition, in lambs' plasma at 24 and 72 h after their birth, and in colostrum samples at parturition and 72 h later. Body weight of lambs was recorded five times from birth until the age of 60 days. Accordingly, the leucogram was evaluated in blood samples collected six times within the same period. On average, IgG concentration was higher (p < 0.05) in the blood of KM-ewes compared to KC and CC groups and in colostrum of KM-ewes compared to other groups (p < 0.001). KM-lambs had greater IgG titer and IFN-γ level than the other groups (p < 0.05). The IL-10/ IFN-γ ratio in KM-ewes was lower than the CC group (p = 0.06). Overall, the growth rate of lambs did not differ among groups (p > 0.05). Total oocysts' excretion in KM- and CM-lambs was reduced by 94.9% (p = 0.05) and 92.6% (p = 0.025), respectively, compared to KC-lambs, following the 3-week period after challenge, when E. ovinoidalis predominated in all groups. The dominant type of leucocytes was monocytes in all experimentally infected lambs, but not in NC-lambs, while overall lymphocytes were lower in KC-lambs than in NC-lambs (p < 0.05). Considering that almost all young indoor-reared lambs are exposed to coccidia species during their early life, melatonin treatment prenatally could suggest an alternative management tool in alleviating infection pressure.

The Immune Response in the Uteri and Placentae of Chlamydia abortus-Infected Ewes and Its Association with Pregnancy Outcomes

The enzootic abortion of ewes, caused by the bacterium Chlamydia abortus (C. abortus), is one of the main causes of abortion in sheep. There are multiple contributory factors, including chlamydial growth, host immune response, and hormonal balance, that result in different pregnancy outcomes, such as abortion, the birth of weak lambs that may die, or healthy lambs. This study aimed to determine the relationship between phenotypical patterns of immune cell infiltration and different pregnancy outcomes in twin-bearing sheep (both lambs born dead; one alive and one dead; both alive) when experimentally infected with C. abortus. Both the sheep uteri and placentae were collected after parturition. All samples were analysed for specific immune cell features, including cell surface antigens and the T-regulatory (Treg) cell-associated transcription factor and cytokines, by immunohistochemistry and in situ hybridisation. Some of these immunological antigens were evaluated in ovine reproductive tissues for the first time. Differential patterns of T helper/Treg cells revealed significant group effects in the placentae. It suggests the potential role that the balance of lymphocyte subsets may play in affecting different pregnancy outcomes in C. abortus-infected sheep. The present study provides novel detailed information about the immune responses observed at the maternofoetal interface in sheep at the time of pre-term abortion or lambing.

Protective Efficacy of BCG Vaccination in Calves Vaccinated at Different Ages

Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), is a globally prevalent pathogen with significant animal welfare, economic and public health impacts. In the UK, the control of bTB relies on detection via tuberculin skin tests with ancillary interferon gamma (IFN-γ) release assays, followed by culling infected animals. Vaccination with Bacille Calmette-Guérin (BCG) could be an important element of bTB control, and a number of studies have demonstrated its protective efficacy, particularly when young calves are vaccinated. Here, we compared immune responses and the protective efficacy of BCG in calves vaccinated within the first day of life and at three weeks of age. Significant protection from M. bovis infection was observed in BCG-vaccinated calves compared to non-vaccinated, age-matched controls. No significant differences were shown between calves vaccinated at one day and at three weeks of age when assessing the protective efficacy of BCG (measured as a reduction in lesions and bacterial burden). Antigen-specific IFN-γ levels were similar between the BCG-vaccinated groups, but significantly different from the non-vaccinated control animals. Antigen-specific IFN-γ expression post-BCG vaccination was correlated significantly with protection from M. bovis infection, whereas IFN-γ levels post-challenge correlated with pathology and bacterial burden. These results indicate that early-life vaccination with BCG could have a significant impact on M. bovis infection and, therefore, bTB incidence, and they demonstrate that age, at least within the first month of life, does not significantly impact the protective effect of vaccination.

Development of a bead-based multiplex assay to quantify bovine interleukin-10, tumor necrosis factor-α, and interferon-γ concentrations in plasma and cell culture supernatant

•

Bead-based assays provide a platform for simultaneous quantification of multiple cytokines.

•

We developed a multiplex bead-based assay for quantification of bovine TNF-α, IL-10, and IFN-γ to evaluate inflammatory profiles in cattle.

•

We used mononuclear reagents and recombinant standards produced in mammalian cells.

•

The multiplex assay quantified all 3 cytokines across a broad concentration range in plasma and cell culture supernatants.

The quantification of cytokines can improve our understanding of immune response and inflammation dynamics in dairy cows. Bead-based assays provide a sensitive, high-throughput platform, allowing for simultaneous quantification of multiple cytokines within a wide linear detection range. Our objective was to develop a multiplex bead-based assay using monoclonal antibodies for simultaneous quantification of bovine tumor necrosis factor (TNF)-α, IL-10, and IFN-γ in plasma and peripheral blood mononuclear cell (PBMC) culture supernatants. Recombinant cytokine standards produced in mammalian cells were used to determine the lower limit of detection and the linear detection range for each cytokine. The lower limit of detection was 110 pg/mL for IL-10, 95 pg/mL for TNF-α, and 20 pg/mL for IFN-γ. The linear quantification range was 110 to 241,000 pg/mL for IL-10, 95 to 620,000 pg/mL for TNF-α, and 20 to 130,000 pg/mL for IFN-γ. All 3 monoclonal capture and detection antibodies were specific for their respective cytokine analyte when using the recombinant IL-10, TNF-α, and IFN-γ standards. Intraassay and interassay coefficients of variation (CV) were <10% and <12%, respectively, for all analytes and samples matrices. Next, concentrations of native cytokines were determined in PBMC culture supernatants (n = 4) and in plasma from whole-blood samples (n = 6) with or without stimulation with Escherichia coli lipopolysaccharide or a mix of phorbol myristate acetate (PMA) and ionomycin. Peak concentrations of all 3 cytokines were secreted from PBMC after PMA/ionomycin stimulation (TNF-α, 8 h, range: 39,266–506,422 pg/mL; IL-10, 18 h, range: 15,770–63,415 pg/mL; IFN-γ 18 h, range: 189,977–492,659 pg/mL). In contrast, the highest concentrations in plasma from whole-blood stimulation were observed for IL-10 and TNF-α after LPS stimulation (TNF-α, 4 h, range: 1,764–13,460 pg/mL; IL-10, 24 h, range: 2,401–6,371 pg/mL), whereas PMA and ionomycin induced the highest secretion of IFN-γ (18 h, range: 53–20,215 pg/mL). In conclusion, the multiplex assay can quantify native IL-10, TNF-α, and IFN-γ across a broad concentration range in bovine plasma and cell culture supernatant, thereby providing a novel tool to evaluate inflammatory profiles in cattle and especially in dairy cows with inflammatory conditions. The existing multiplex assay can be expanded in the future by adding bead assays for additional bovine cytokines.

Green extraction of bioactive compounds from wine lees and their bio-responses on immune modulation using in vitro sheep model

The objective of this study was to apply microwave-assisted extraction using green solvents starting from 3 different wine (white, rosé, and red) lees and to test their bio-response on sheep peripheral blood mononuclear cells proliferation, Bax/Bcl-2 ratio, and cytokines secretion. Wine lees (WL) of local organic farming from white wine, produced with Trebbiano cultivar, rosé and red wine, made with Nero di Troia cultivar, were collected. The WL were subjected to microwave-assisted extraction using 2 green solvents (water and ethanol) in 3 different combinations (water; water/ethanol 1:1 vol/vol; ethanol) with a dry matter-to-solvent ratio of 1:40 (wt/vol) at 4 temperature levels: 50, 100, 150, and 200°C. Sodium carbonate Na₂CO₃ (2 mmol/g of dry weight of lees) was used for increasing the polyphenol extraction yield. A total number of 6 extracts, 2 for each kind of WL investigated, according to their total phenolic content and in vitro antioxidant capacity, were selected to be tested on sheep peripheral blood mononuclear cells, as an animal model. All the WL extracts demonstrated a strong antiproliferative action. On the contrary, the cytokines' profile was mainly dependent on the different winemaking derived WL and the extraction solvent combination procedures. Red WL extract obtained by a combination of water/Na₂CO₃ and tested at 0.8 mg/mL, resulted in an increase of both IL-6 secretion and Bax/Bcl-2 ratio. Data from the present study demonstrated that WL extracts derived from different winemaking and solvent extraction could have a bimodal action on control of inflammatory mediated damage and highlighted the importance for further studies aimed at applying the biorefinery process on by-products to increase their economic value and exploit new derived bioactive compound.

Functionally distinct T-helper cell phenotypes predict resistance to different types of parasites in a wild mammal

The adaptive immune system is critical to an effective response to infection in vertebrates, with T-helper (Th) cells pivotal in orchestrating these responses. In natural populations where co-infections are the norm, different Th responses are likely to play an important role in maintaining host health and fitness, a relationship which remains poorly understood in wild animals. In this study, we characterised variation in functionally distinct Th responses in a wild population of Soay sheep by enumerating cells expressing Th-subset specific transcription factors and quantifying Th-associated cytokines. We tested the prediction that raised Th1 and Th2 responses should predict reduced apicomplexan and helminth parasite burdens, respectively. All measures of Th-associated cytokine production increased with age, while Th17- and regulatory Th-associated cytokine production increased more rapidly with age in males than females. Independent of age, sex, and each other, IL-4 and Gata3 negatively predicted gastro-intestinal nematode faecal egg count, while IFN-γ negatively predicted coccidian faecal oocyst count. Our results provide important support from outside the laboratory that Th1 and Th2 responses predict resistance to different kinds of parasites, and illustrate how harnessing specific reagents and tools from laboratory immunology will illuminate our understanding of host-parasite interactions in the wild.

Association of Melatonin Administration in Pregnant Ewes with Growth, Redox Status and Immunity of Their Offspring

Simple Summary

Melatonin is a known antioxidant and anti-inflammatory regime, while in sheep it is broadly used to accelerate the onset of the breeding season. Our recent study showed that melatonin administration during pregnancy in heat-stressed ewes improved fertility rate and number of lambs born per ewe, the redox status of the maternal organism and the produced milk quantity until weaning. In this study, we present the impact of melatonin administration in stressed ewes during pregnancy considering: (a) humoral response of both maternal organism and offspring during the first two days after parturition, (b) chemical composition and antioxidant parameters of colostrum and milk until weaning and (c) redox status of the offspring until weaning. The results indicated that melatonin improved the redox status of the offspring and the quality of colostrum. Moreover, melatonin could be administered as immune-modulatory regime, apart from antioxidant, in prenatally stressed offspring in order to cope with the crucial first days of their life, as the humoral response results suggested.

Abstract

In this study, the effects of melatonin treatment on growth, redox status and immunity in prenatally stressed newborn lambs were evaluated. Thirty-seven newborn lambs were allocated into two groups (melatonin-MEL and control-CON), based on whether their mothers were treated with melatonin implants or not, respectively. All pregnant ewes were exposed to heat stress. The body weight of lambs was recorded at birth (L0), and then on days 15 (L15) and 40 (L40). Redox biomarkers [total antioxidant capacity (TAC), glutathione (GSH), thiobarbituric acid reactive substances (TBARS)] were assayed in blood samples collected from lambs on days L0, L1, L2, L5, L10 and L40. Chemical analysis and antioxidant capacity were evaluated in colostrum and milk samples collected at the same time points with blood samples. Cytokines (IL-1β, IL-6, IL-10, IFN-γ) and immunoglobulin (IgG) were assayed in blood and colostrum samples collected from ewes on days L0 and L1, and in lambs’ blood on days L0, L1 and L2. The results revealed that body weight gain of newborn lambs did not differ between the two groups (p > 0.05). Better redox status was found in MEL lambs until L2, as well as higher antioxidant capacity in the colostrum of MEL ewes compared to CON ones on day L0 (p < 0.05). In MEL ewes’ colostrum, higher protein content was measured on day L0 and higher fat content on L1 compared to CON group (p < 0.05). The highest level of IL-6 was found in MEL ewes on L1, with a concomitant increase of IL-10 level in MEL lambs in comparison to CON lambs on L2. Moreover, CON colostrum resulted in a higher level of IL-10 within time, coupled with an increased level of IgG found in lambs’ plasma on L2 (p = 0.04). This study indicated that melatonin could be administered as antioxidant and immune-modulatory regime in prenatally stressed offspring in order to cope with the crucial first days of their life. This effect of melatonin was also amplified by crosstalk between IL-6, IL-10 and IgG production, resulting in an improved quality of produced milk.

Antigen-specific response of CD4+ T cells and hepatic lymph node cells to Fasciola hepatica-derived molecules at the early and late stage of the infection in sheep

The immunomodulatory capacity of F. hepatica antigens is probably one of the main reasons for the development of a driven non-protective Th2 immune response. In this study, we analysed the cellular response of hepatic lymph node cells and CD4⁺ T cells in terms of proliferative response, efficiency of antigen presentation and cytokine production, to F. hepatica-derived molecules, at early and late stages of the infection. Thirty-one sheep were allocated into five groups and were slaughtered at 16 dpi and 23 wpi. In order to analyse antigen-specific response, the following F. hepatica recombinant molecules were used: rFhCL1, rFhCL2, rFhCL3, rFhCB1, rFhCB2, rFhCB3, rFhStf-1, rFhStf-2, rFhStf-3 and rFhKT1. A cell proliferation assay using hepatic lymph node cells and an antigen presentation cell assay using CD4⁺ T cells were performed. At 16 dpi, all molecules but rFhStf-2 and rFhKT1 elicited a significant cell proliferative response on hepatic lymph node cells of infected animals. At both early and late stage of the infection, antigen presentation of rFhCB3 and rFhCL2 resulted in higher stimulation index of CD4⁺ T cells which was IL-2 mediated, although no statistically significant when compared to uninfected animals. Significant cytokine production (IL-4, IL-10 and IFN-γ) was conditioned by the antigen-specific cell stimulation. No CD4⁺ T cell exhaustion was detected in infected sheep at the chronic stage of the infection. This study addressed antigen-specific response to F. hepatica-derived molecules that are involved in key aspects of the parasite survival within the host.

Synergistic Activation of Bovine CD4+ T Cells by Neutrophils and IL-12

CD4+ T cell activation requires inflammatory cytokines to provide a third signal (3SI), such as interleukin-12 (IL-12). We recently reported that bovine neutrophils can enhance the activation of bovine CD4+ T cells. To explore the interactions between neutrophils and third signal cytokines in bovine CD4+ T cell activation, naïve CD4+ T cells were isolated from cattle lymph nodes and stimulated for 3.5 days with anti-bovine CD3 (first signal; 1SI), anti-bovine CD28 (second signal; 2SI), and recombinant human IL-12 (3SI) in the presence or absence of neutrophils harvested from the same animals. Indeed, the strongest activation was achieved in the presence of all three signals, as demonstrated by CD25 upregulation, IFNγ production in CD4+ T cells, and secretion of IFNγ and IL-2 in cell supernatants. More importantly, 1SI plus neutrophils led to enhanced CD25 expression that was further increased by IL-12, suggesting synergistic action by IL-12 and neutrophils. Consistently, neutrophils significantly increased IFNγ production in 1SI plus IL-12-stimulated CD4+ T cells. Our data suggest the synergy of neutrophils and IL-12 as a novel regulator on bovine CD4+ T cell activation in addition to three signals. This knowledge could assist the development of immune interventions for the control of infectious diseases in cattle.

Development and validation of ELISAs for the quantitation of interleukin (IL)-1β, IL-6, IL-8 and IL-10 in ovine plasma

There is growing evidence that inflammation underpins many common diseases. Inflammatory/immunomodulatory/immune mediators, such as cytokines, are key modulators of inflammation and mediate both immune cell recruitment and complex intracellular signalling pathways. Ovine models of disease are increasingly utilized in pre-clinical research, however existing methods for measuring cytokine levels are limited. We established and validated enzyme-linked immunosorbent assays (ELISAs) targeting interleukin (IL)-1β, IL-6, IL-8 and IL-10 in sheep plasma. These ELISAs showed high sensitivity and specificity with intra- and inter-assay CV's below 10%, and recovery rates between 82 and 123%. Sensitivity for IL-1β, IL-6, IL-8 and IL-10 were 117.6 pg/mL, 443.1 pg/mL, 30.9 pg/mL, and 64.3 pg/mL, respectively. ELISA test result reproducibility decreased significantly after 12 weeks of plasma storage at -80 °C. Therefore, for accurate cytokine measurements, plasma samples need to be tested within three months of sample collection to account for cytokine protein degradation. These ELISAs offer a reliable and convenient method to identify inflammatory cytokine changes in sheep, allowing key insights into the disease pathogenesis of these ruminants.

Nexus Between Immune Responses and Oxidative Stress: The Role of Dietary Hydrolyzed Lignin in ex vivo Bovine Peripheral Blood Mononuclear Cell Response

The control of immune responses is particularly critical when an increase of oxidative stress occurs, causing an impairment of immune cell response and a condition of systemic inflammation, named oxinflammation. Nutritional strategies based on the use in the diet of phytochemicals extracted from plants, rich in antioxidants, could help restore the antioxidant/oxidant balance and obtain a modulation of immune response. Lignin represents a valuable resource of phenolic compounds, which are characterized by a corroborated antioxidant effect. To date, there are no studies reporting the effects of lignin in the diet on immune responses and oxidative stress in ruminants. The objective of the present experiment was the evaluation of the dietary inclusion of Pinus taeda hydrolyzed lignin on the ex vivo immune responses and oxidative stress biomarkers by peripheral blood mononuclear cells (PBMCs) isolated from beef steers. In order to test the effect during oxidative stress exposition, cells were treated with hydrogen peroxide (H₂O₂). The proliferation test and the viability assay were carried out on cells, whereas, on supernatants, the cytokine profile and the oxidative stress biomarkers were evaluated. The dietary inclusion with P. taeda hydrolyzed lignin resulted in cytoprotection after H₂O₂ exposition, increasing the number of viable monocytes and decreasing the reactive oxygen/nitrogen species production in supernatants. The cytokine profile indicated the modulatory role of hydrolyzed lignin on immune response, with a concomitant decrease of TNF-α and increase of IL-8 production, which are strictly connected with monocyte activation and antioxidant response pathway. These results demonstrated that hydrolyzed lignin may provide a modulation of oxidative stress and inflammatory response in PBMCs; thus, the P. taeda hydrolyzed lignin could be suggested as an innovative phytochemical in ruminant feed.

Characterization of IL-10-producing neutrophils in cattle infected with Ostertagia ostertagi

IL-10 is a master regulator of immune responses, but its cellular source and function in cattle during the initial phase of immune priming have not been well established. Despite a massive B cell response in the abomasal draining lymph nodes in Ostertagia ostertagi (OO)-infected cattle, protective immunity is slow to develop, and partial protection requires years of repeated exposure. In addressing this problem, our initial hypothesis was that B cells produce IL-10 that downregulates the host protective immune response. However, our results showed that neutrophils made up the majority of IL-10-producing cells in circulation and in secondary lymphoid tissues, particularly the spleen (80%). Conversely, IL-10-producing B cells were rare. In addition, approximately 10% to 20% of the neutrophils in the blood and spleen expressed MHC II and were IL-10 negative, suggesting that neutrophils could also participate in antigen presentation. In vitro investigation of bovine neutrophils revealed that exposure thereof to OO extract increased IL-10 and MHC II expression in these cells in a dose-dependent manner, consistent with IL-10+/MHC II+ neutrophils detected in cattle shortly after experimental OO infection. Co-culture of untreated neutrophils with anti-CD3 antibody (Ab)-stimulated CD4+ T cells led to enhanced T cell activation; also, IL-10 depletion with neutralizing Ab enhanced the stimulatory function of neutrophils. OO extract depressed neutrophil stimulation of CD4+ T cells in the presence of IL-10-neutralizing Ab, suggesting that OO utilizes both IL-10-dependent and independent mechanisms to manipulate the bovine immune response. Finally, contact and viability were required for T cell-stimulatory neutrophil function. This report, to the best of our knowledge, is the first to demonstrate that neutrophil-derived IL-10 is directly involved in T cell regulation in cattle. Our data suggest that neutrophils and neutrophil-derived IL-10 are co-opted by nematode parasites and other pathogens to attenuate host immune responses and facilitate pathogen survival.

Natural and inducible regulatory B cells are widely distributed in ovine lymphoid tissues

Regulatory B cells that produce IL-10 are now recognized as an important component of the immune system. We previously confirmed that IL-10 secreting CD21⁺ regulatory B cells (B_reg cells) were present in ovine jejunal Peyer's patches (JPP) and this IL-10 production suppressed IL-12 and IFN-γ secretion. It is not known, however, whether ovine B_reg cells are restricted to JPP or are present in other lymphoid tissues. Therefore, CD21⁺ B cells were purified from sheep JPP and from a variety of mucosal and systemic lymphoid tissues using magnetic cell sorting. Purified CD21⁺ B cells were stimulated with a TLR9-agonist, CpG oligodeoxynucleotide (CpG ODN), and the frequency of spontaneous and inducible (i) IL-10-secreting B cells was evaluated by ELISPOT. Spontaneous IL-10 secreting CD21⁺ B cells were present in mucosal (jejunal PP, parabronchial lymph nodes (LN), mesesnteric LN, and palatine tonsils) and systemic (spleen and blood) lymphoid tissues. Mucosal lymphoid tissues (parabronchial and mesenteric LNs and JPP) had the highest frequency of cells spontaneously secreting IL-10 while tonsils had the lowest. The frequency of B cells spontaneously secreting IL-10 was lowest in blood and spleen. There was large inter-animal variation in the frequency of CD21⁺ B cells spontaneously secreting IL-10 and no significant difference was detected following CpG ODN stimulation. When comparing within individual animals there was, however, a consistent increase in the frequency of CD21⁺ cells secreting IL-10 following CpG ODN stimulation versus stimulation with GpC control ODN. The presence of inducible (i)B_reg cells in ovine mucosal tissues supports previous evidence from mice indicating that B cells have the capacity to modulate inflammatory responses. The presence of iB_reg cells in ruminants may also provide a novel therapeutic target for both immunomodulatory drugs and vaccines designed to control antigen-specific mucosal inflammation.

Immunomodulatory Effects of Amblyomma variegatum Saliva on Bovine Cells: Characterization of Cellular Responses and Identification of Molecular Determinants

The tropical bont tick, Amblyomma variegatum, is a tick species of veterinary importance and is considered as one of major pest of ruminants in Africa and in the Caribbean. It causes direct skin lesions, transmits heartwater, and reactivates bovine dermatophilosis. Tick saliva is reported to affect overall host responses through immunomodulatory and anti-inflammatory molecules, among other bioactive molecules. The general objective of this study was to better understand the role of saliva in interaction between the Amblyomma tick and the host using cellular biology approaches and proteomics, and to discuss its impact on disease transmission and/or activation. We first focused on the immuno-modulating effects of semi-fed A. variegatum female saliva on bovine peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages in vitro. We analyzed its immuno-suppressive properties by measuring the effect of saliva on PBMC proliferation, and observed a significant decrease in ConA-stimulated PBMC lymphoproliferation. We then studied the effect of saliva on bovine macrophages using flow cytometry to analyze the expression of MHC-II and co-stimulation molecules (CD40, CD80, and CD86) and by measuring the production of nitric oxide (NO) and pro- or anti-inflammatory cytokines. We observed a significant decrease in the expression of MHC-II, CD40, and CD80 molecules, associated with decreased levels of IL-12-p40 and TNF-α and increased level of IL-10, which could explain the saliva-induced modulation of NO. To elucidate these immunomodulatory effects, crude saliva proteins were analyzed using proteomics with an Orbitrap Elite mass spectrometer. Among the 336 proteins identified in A. variegatum saliva, we evidenced bioactive molecules exhibiting anti-inflammatory, immuno-modulatory, and anti-oxidant properties (e.g., serpins, phospholipases A2, heme lipoprotein). We also characterized an intriguing ubiquitination complex that could be involved in saliva-induced immune modulation of the host. We propose a model for the interaction between A. variegatum saliva and host immune cells that could have an effect during tick feeding by favoring pathogen dissemination or activation by reducing the efficiency of host immune response to the corresponding tick-borne diseases.

Dairy Heifers Naturally Exposed to Fasciola hepatica Develop a Type 2 Immune Response and Concomitant Suppression of Leukocyte Proliferation

Fasciola hepatica is a parasitic trematode of global importance in livestock. Control strategies reliant on anthelmintics are unsustainable due to the emergence of drug resistance. Vaccines are under development, but efficacies are variable. Evidence from experimental infection suggests that vaccine efficacy may be affected by parasite-induced immunomodulation. Little is known about the immune response to F. hepatica following natural exposure. Hence, we analyzed the immune responses over time in calves naturally exposed to F. hepatica infection. Cohorts of replacement dairy heifer calves (n = 42) with no prior exposure to F. hepatica, on three commercial dairy farms, were sampled over the course of a grazing season. Exposure was determined through an F. hepatica-specific serum antibody enzyme-linked immunosorbent assay (ELISA) and fluke egg counts. Concurrent changes in peripheral blood leukocyte subpopulations, lymphocyte proliferation, and cytokine responses were measured. Relationships between fluke infection and immune responses were analyzed by using multivariable linear mixed-effect models. All calves from one farm showed evidence of exposure, while cohorts from the remaining two farms remained negative over the grazing season. A type 2 immune response was associated with exposure, with increased interleukin-4 (IL-4) production, IL-5 transcription, and eosinophilia. Suppression of parasite-specific peripheral blood mononuclear cell (PBMC) proliferation was evident, while decreased mitogen-stimulated gamma interferon (IFN-γ) production suggested immunomodulation, which was not restricted to parasite-specific responses. Our findings show that the global immune response is modulated toward a nonproliferative type 2 state following natural challenge with F. hepatica. This has implications in terms of the timing of the administration of vaccination programs and for host susceptibility to coinfecting pathogens.

1,25-Dihydroxyvitamin D3 modulates the phenotype and function of Monocyte derived dendritic cells in cattle

Background

The active form of the vitamin D₃, 1,25-Dihydroxyvitamin D₃ (1,25-(OH)₂D₃) has been shown to have major effects not only on physiological processes but also on the regulation of the immune system of vertebrates. Dendritic cells are specialised antigen presenting cells which are in charge of the initiation of T-cell dependant immune responses and as such are key regulators of responses towards pathogens. In this study we set out to evaluate the effects of 1,25-(OH)₂D₃ on the phenotype of cattle monocyte-derived dendritic cells (MoDCs) and how the conditioning with this vitamin affects the function of these myeloid cells.

Results

MoDCs were generated from CD14⁺ monocytes with bovine IL-4 and GM-CSF with or without 1,25-(OH)₂D₃ supplementation for 10 days. Vitamin D conditioned MoDCs showed a reduced expression of co-stimulatory and antigen presenting molecules, as well as a reduced capability of endocytose ovalbumin. Furthermore, the capacity of MoDCs to induce proliferation in an allogeneic mixed leukocyte reaction was abolished when MoDCs were generated in presence of 1,25-(OH)₂D₃. LPS induced maturation of 1,25-(OH)₂D₃conditioned MoDCs resulted in lower secretion of IL-12 and higher IL-10 than that observed in MoDCs.

Conclusions

The typical immunotolerant phenotype observed in cattle DCs after exposure to 1,25-(OH)₂D₃ has a significant effect on the functionality of these immune cells, inhibiting the T-cell stimulatory capacity of MoDCs. This could have profound implications on how the bovine immune system deals with pathogens, particularly in diseases such as tuberculosis or paratuberculosis.

The Chronic Stages of Bovine Fasciola hepatica Are Dominated by CD4 T-Cell Exhaustion

Fasciola hepatica infection of ruminants leads to non-resolving chronic infection, as patency develops, there is switching to a TGF-β and IL-10 led response. Here, we explore the responses of CD4 T-cells within the major draining lymph nodes. We found minimal expression of Foxp3 within CD4 cells but elevated levels within the γδ (WC1⁺) population. There is a strong T-cell-intrinsic exhaustion phenotype within the hepatic lymph node (HLN) characterized by a lack of antigen-specific proliferation and cytokine secretion. CD4 T-cells recovered from the HLN had high levels of PD-1 expression and low levels of IL-2 secretion. Exogenous IL-2 partially rescued this defect; when combined with neutralization of IL-10 and TGF-β, full restoration of proliferation, and cytokine production was achieved. Moreover, there is a clear uncoupling of the mechanisms that facilitate this regulation with parasite-specific proliferation and cytokine secretion being governed by independent means. These data would suggest that there is a CD4 T-cell-intrinsic regulation in place early in chronic infection, potentially leading to failure in resistance to reinfection.

Development of a bead-based multiplexed assay for simultaneous quantification of five bovine cytokines by flow cytometry

Quantifying cytokines is extremely important in studies of host-pathogen interactions. Multiplex assays are commercially available but only for human and mouse cytokines. Here a method for the simultaneous quantification of five important bovine cytokines IFNγ, IL-4, IL-10, IL-12, and TNFα in cell culture supernatants, using flow cytometry was reported. Functional beads from BD Biosciences expressing specific APC intensity were used. Commercially available antibodies against bovine cytokines were covalently coupled to beads as capture antibodies. Fixed recombinant cytokines were revealed with a second monoclonal antibody coupled with biotin, then revealed with streptavidin-PE. This complex was analyzed using a standard flow cytometer. Experiments were performed to check no cross reactions had occurred. The limits of detection ranged between 0.08 and 0.4 ng/ml depending on the cytokine, and the linearity between the lower and higher limits was remarkable (R²  > 99.8%). Finally, native cytokines from cell culture supernatants were tested. Results were compared using the standard ELISA test and showed that concentrations of native cytokine in cell culture supernatants were comparable with the two methods, with a wider dynamic range using beads and flow cytometry than with ELISA assays. Bovine IFNγ, IL-4, IL-10, IL-12, and TNFα in culture supernatants can be now simultaneously detected in a single assay, using a standard flow cytometer for both basic and high-throughput analyses. © 2017 International Society for Advancement of Cytometry.

Phytosterols from Dunaliella tertiolecta Reduce Cell Proliferation in Sheep Fed Flaxseed during Post Partum

The post partum period is characterized by immunosuppression and increased disease susceptibility. Both phytosterols from microalga Dunaniella tertiolecta and dietary supplementation with n-3 polyunsaturated fatty acids (PUFA) influence cell proliferation and cytokine release during inflammation. The objective of this paper was the evaluation of the effects of physterols, extracted and purified from D. tertiolecta, on the in vitro immune responses of ewes supplemented with flaxseed during post partum. Twenty Comisana parturient ewes were divided in two balanced groups, and supplemented with flaxseed (FS, 250 g/day) or fed with a conventional diet (CON). Blood samples (15 mL) were collected for five weeks, starting from lambing, in order to isolate peripheral blood mononuclear cells (PBMC). Stimulated PBMC were treated with a total sterols fraction from D. tertiolecta (TS), a mix of ergosterol and 7-dehydroporiferasterol (purified extract, PE), and a mix of acetylated ergosterol and 7-dehydroporiferasterol (acetylated purified extract, AcPE), extracted and purified from D. tertiolecta at two concentrations (0.4 and 0.8 mg/mL). Results of the experiment demonstrated that n-3 PUFA from flaxseed induced an anti-inflammatory cytokine profile, with an increase of both IL-10, IL-6 and a decrease of IL-1β. TS, PE, and AcPE purified from D. tertiolecta showed an anti-proliferative effect on sheep PBMC regardless their chemical composition and concentration.

Modulation of the transcription factor NF-κB in antigen-presenting cells by bovine respiratory syncytial virus small hydrophobic protein

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease in young cattle and is closely related to human RSV (HRSV), which causes severe respiratory disease in infants and the elderly. The RSV genome encodes a small hydrophobic (SH) protein with viroporin activity. Previous studies have shown that recombinant BRSV lacking the SH gene (rBRSVΔSH) is attenuated in the lungs, but not in the upper respiratory tract, of calves and mucosal vaccination with rBRSVΔSH induced long-lasting protective immunity. Attenuation of rBRSVΔSH may be due to the ability of this virus to induce an early innate response as rBRSVΔSH induces higher levels of pro-inflammatory cytokines than wild-type (wt) rBRSV. In this study, we investigated the effects of the BRSV SH protein on NF-κB p65 phosphorylation, a master step in the regulation of pro-inflammatory cytokines. Expression of SH resulted in the inhibition of NF-κB p65 phosphorylation in response to BRSV infection and extracellular lipopolysaccharide, and a reduction in the production of pro-inflammatory cytokines. In contrast, rBRSVΔSH does not inhibit NF-κB p65 phosphorylation in bovine antigen-presenting cells, including monocytes, macrophages and dendritic cells, resulting in increased expression of pro-inflammatory cytokines and increased activation of T cells compared to cells infected with wt BRSV. These findings highlight an important role for the BRSV SH protein in immune modulation.

IL-10 suppression of IFN-γ responses in tuberculin-stimulated whole blood from Mycobacterium bovis infected cattle

The measurement of bovine interferon-gamma (IFN-γ) forms the basis of a diagnostic test for bovine tuberculosis where Mycobacterium bovis sensitised effector T cells produce IFN-γ following in vitro stimulation with tuberculin antigens. In cattle infected with M. bovis it is also known that the anti-inflammatory IL-10 cytokine can inhibit in vitro production of IFN-γ leading to a reduced response in the IFN-γ diagnostic test. In order to investigate this in greater detail, whole blood samples from tuberculin skin test positive and negative cattle were stimulated with bovine and avian tuberculin antigens and in parallel with a neutralising anti-IL-10 monoclonal antibody. The results showed that IFN-γ protein levels increased when IL-10 activity was suppressed by Anti - IL-10. By using a standard diagnostic interpretation, the elevated levels of IFN-γ were shown to change the level of agreement between the performance of the single intradermal comparative tuberculin test (SICTT) and IFN-γ assay, depending on the tuberculin treatment. A transcriptomic analysis using RT-qPCR investigated the influence of IL-10 activity on expression of a suite of cytokine genes (IFNG, IL12B, IL10 and CXCL10) associated with antigen-stimulated production of IFN-γ. The IFNG and IL12B genes both experienced significant increases in expression in the presence of Anti-IL-10, while the expression of IL10 and CXCL10 remained unaffected.

Enhancing the toolbox to study IL-17A in cattle and sheep

The development of methods to detect cytokine expression by T cell subsets in ruminants is fundamental to strategic development of new livestock vaccines for prevention of infectious diseases. It has been possible to detect T cell expression of IFN-γ, IL-4 and IL-10 in ruminants for many years but methods to detect expression of IL-17A are relatively limited. To address this gap in capability we have cloned bovine and ovine IL-17A cDNAs and expressed biologically-active recombinant proteins in Chinese Hamster Ovary (CHO) cells. We used the transfected CHO cells to screen commercially-available antibodies for their ability to detect IL-17A expression intracellularly and in culture supernates. We demonstrate that an ELISA for bovine IL-17A detects native ovine IL-17A. Moreover, the constituent polyclonal antibodies (pabs) in the ELISA were used to enumerate peripheral blood mononuclear cells (PBMC) expressing IL-17A from cattle and sheep by ELISpot. We identified two monoclonal antibodies (mabs) that detect recombinant intracellular IL-17A in CHO cells by flow cytometry. One of these mabs was used to detect native intracellular IL-17A expression in PBMC in conjunction with cell surface phenotyping mabs [CD4+ve, CD8+ve and Workshop Cluster 1 (WC-1)+ve gamma-delta (γδ)] we show that distinct T cell subsets in cattle (defined as CD4+ve, CD8+ve or WC-1+ve) and sheep (defined as CD4+ve or WC-1+ve) can express IL-17A following activation. These novel techniques provide a solid basis to investigate IL-17A expression and define specific CD4+ve T cell subset activation in ruminants.

Human amnion epithelial cells modulate the inflammatory response to ventilation in preterm lambs

Ventilation of preterm neonates causes pulmonary inflammation that can contribute to lung injury, propagate systemically and result in long-term disease. Modulation of this initial response may reduce lung injury and its sequelae. We aimed to determine the effect of human amnion epithelial cells (hAECs) on immune activation and lung injury in preterm neonatal lambs. Preterm lambs received intratracheal hAECs (90x106) or vehicle, prior to 2 h of mechanical ventilation. Within 5 min of ventilation onset, lambs also received intravenous hAECs (90x106) or vehicle. Lung histology, bronchoalveolar lavage (BAL) cell phenotypes, and cytokine profiles were examined after 2 h of ventilation, and in unventilated controls. Histological indices of lung injury were higher than control, in vehicle-treated ventilated lambs but not in hAEC-treated ventilated lambs. Ventilation-induced pulmonary leukocyte recruitment was greater in hAEC-treated lambs than in vehicle-treated lambs. Lung IL-1β and IL-6 mRNA expression was higher in vehicle- and hAEC-treated ventilated lambs than in controls but IL-8 mRNA levels were greater than control only in vehicle-treated ventilated lambs. Numbers of CD44+ and CD21+ lymphocytes and macrophages from the lungs were altered in vehicle- and hAEC-treated ventilated lambs. Numbers of CD8+ macrophages were lower in hAEC-treated ventilated lambs than in vehicle-treated ventilated lambs. Indices of systemic inflammation were not different between vehicle- and hAEC-treated lambs. Human amnion epithelial cells modulate the pulmonary inflammatory response to ventilation in preterm lambs, and reduce acute lung injury. Immunomodulatory effects of hAECs reduce lung injury in preterm neonates and may protect against longer-term respiratory disease.

Evidence for the existence of regulatory and effector B cell populations in Peyer's patches of sheep

IL-10 secreting CD21(+) B cells exist in sheep Peyer's patches (PP). It's not known however, whether all PP B cells are regulatory or whether an effector population also exists in this tissue. To further characterize the subpopulations of B cells in PP's, highly purified B cells were negatively sorted from jejunal PP and fractionated according to co-expression of CD72(+)CD21(+)or CD72(+)CD21(-) molecules and then stimulated with the TLR9-agonist, CpG ODN. IL-10, IL-12, IFN-γ, and IgM production were then assayed. We observed that only highly purified CD72(+)CD21(+) B cells spontaneously secreted high levels of IL-10, but they did not produce any IL-12, IFN-γ or IgM suggesting that this cell population contains regulatory B cells. In contrast, CD72(+)CD21(-) B cells did not secrete IL-10, but secreted IL-12, IFN-γ, and IgM, suggesting they include effector cells. In addition, B cells expressing surface IgA, IgM and IgG1 all secreted similar levels of IL-10. We further confirmed that only B cells produce IL-10, while other cells in the PP including DCs and T cells do not. Our investigations may provide evidence for the existence of two sub-populations in sheep PP; IL-10 secreting regulatory (CD72(+)CD21(+)) cells, and IL-12/IFN-γ/IgM-secreting effector (CD72(+)CD21(-)) cells.

Macrophage polarization in cattle experimentally exposed to Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne's disease (JD) in cattle, has significant impacts on the livestock industry and has been implicated in the etiology of Crohn's disease. Macrophages play a key role in JD pathogenesis, which is driven by the manipulation of host immune mechanisms by MAP. A change in the macrophage microenvironment due to pathogenic or host-derived stimuli can lead to classical (M1) or alternative (M2) polarization of macrophages. In addition, prior exposure to antigenic stimuli has been reported to alter the response of macrophages to subsequent stimuli. However, macrophage polarization in response to MAP exposure and its possible implications have not been previously addressed. In this study, we have comprehensively examined monocyte/macrophage polarization and responsiveness to antigens from MAP-exposed and unexposed animals. At 3 years post-exposure, there was a heterogeneous macrophage activation pattern characterized by both classical and alternate phenotypes. Moreover, subsequent exposure of macrophages from MAP-exposed cattle to antigens from MAP and other mycobacterial species led to significant variation in the production of nitric oxide, interleukin-10 and tumour necrosis factor α. These results indicate the previously unreported possibility of changes in the activation state and responsiveness of circulating monocytes/macrophages from MAP-exposed cattle.

Interleukin-10 production at the early stage of infection with foot-and-mouth disease virus related to the likelihood of persistent infection in cattle

The factors leading to persistent infection of foot-and-mouth disease (FMD) virus in ruminants are not well defined. This paper provides evidence of the presence of interleukin-10 (IL-10) early in the course of infection (1–4 days) as a factor in the development of persistence of FMD virus in cattle. Results showed that serum IL-10 in carrier cattle infected with FMD virus type O (n = 4) was detected and peaked at 1 or 2 days post infection and rapidly declined thereafter. In contract, serum IL-10 levels in non-carrier cattle (n = 21) were very low or undetectable during the same period.

Phenotypic and functional analysis of monocyte populations in cattle peripheral blood identifies a subset with high endocytic and allogeneic T-cell stimulatory capacity

Circulating monocytes in several mammalian species can be subdivided into functionally distinct subpopulations based on differential expression of surface molecules. We confirm that bovine monocytes express CD172a and MHC class II with two distinct populations of CD14⁺CD16^low/-CD163⁺ and CD14⁻CD16⁺⁺CD163^low- cells, and a more diffuse population of CD14⁺CD16⁺CD163⁺ cells. In contrast, ovine monocytes consisted of only a major CD14⁺CD16⁺ subset and a very low percentage of CD14⁻CD16⁺⁺cells. The bovine subsets expressed similar levels of CD80, CD40 and CD11c molecules and mRNA encoding CD115. However, further mRNA analyses revealed that the CD14⁻CD16⁺⁺ monocytes were CX3CR1^highCCR2^low whereas the major CD14⁺ subset was CX3CR1^lowCCR2^high. The former were positive for CD1b and had lower levels of CD11b and CD86 than the CD14⁺ monocytes. The more diffuse CD14⁺CD16⁺ population generally expressed intermediate levels of these molecules. All three populations responded to stimulation with phenol-extracted lipopolysaccharide (LPS) by producing interleukin (IL)-1β, with the CD16⁺⁺ subset expressing higher levels of IL-12 and lower levels of IL-10. The CD14⁻CD16⁺⁺ cells were more endocytic and induced greater allogeneic T cell responses compared to the other monocyte populations. Taken together the data show both similarities and differences between the classical, intermediate and non-classical definitions of monocytes as described for other mammalian species, with additional potential subpopulations. Further functional analyses of these monocyte populations may help explain inter-animal and inter-species variations to infection, inflammation and vaccination in ruminant livestock.

Dynamics of IL-4 and IL-13 expression in the airways of sheep following allergen challenge

Background

IL-4 and IL-13 play a critical yet poorly understood role in orchestrating the recruitment and activation of effector cells of the asthmatic response and driving the pathophysiology of allergic asthma. The house dust mite (HDM) sheep asthma model displays many features of the human condition and is an ideal model to further elucidate the involvement of these critical Th₂ cytokines. We hypothesized that airway exposure to HDM allergen would induce or elevate the expression profile of IL-4 and IL-13 during the allergic airway response in this large animal model of asthma.

Methods

Bronchoalveolar lavage (BAL) samples were collected from saline- and house dust mite (HDM)- challenged lung lobes of sensitized sheep from 0 to 48 h post-challenge. BAL cytokines (IL-4, IL-13, IL-6, IL-10, TNF-α) were each measured by ELISA. IL-4 and IL-13 expression was assessed in BAL leukocytes by flow cytometry and in airway tissue sections by immunohistology.

Results

IL-4 and IL-13 were increased in BAL samples following airway allergen challenge. HDM challenge resulted in a significant increase in BAL IL-4 levels at 4 h compared to saline-challenged airways, while BAL IL-13 levels were elevated at all time-points after allergen challenge. IL-6 levels were maintained following HDM challenge but declined after saline challenge, while HDM administration resulted in an acute elevation in IL-10 at 4 h but no change in TNF-α levels over time. Lymphocytes were the main early source of IL-4, with IL-4 release by alveolar macrophages (AMs) prominent from 24 h post-allergen challenge. IL-13 producing AMs were increased at 4 and 24 h following HDM compared to saline challenge, and tissue staining provided evidence of IL-13 expression in airway epithelium as well as immune cells in airway tissue.

Conclusion

In a sheep model of allergic asthma, airway inflammation is accompanied by the temporal release of key cytokines following allergen exposure that primarily reflects the Th₂-driven nature of the immune response in asthma. The present study demonstrates for the first time the involvement of IL-4 and IL-13 in a relevant large animal model of allergic airways disease.

Immune Response of Calves Vaccinated with Brucella abortus S19 or RB51 and Revaccinated with RB51

Brucella abortus S19 and RB51 strains have been successfully used to control bovine brucellosis worldwide; however, currently, most of our understanding of the protective immune response induced by vaccination comes from studies in mice. The aim of this study was to characterize and compare the immune responses induced in cattle prime-immunized with B. abortus S19 or RB51 and revaccinated with RB51. Female calves, aged 4 to 8 months, were vaccinated with either vaccine S19 (0.6-1.2 x 1011 CFU) or RB51 (1.3 x 1010 CFU) on day 0, and revaccinated with RB51 (1.3 x 1010 CFU) on day 365 of the experiment. Characterization of the immune response was performed using serum and peripheral blood mononuclear cells. Blood samples were collected on days 0, 28, 210, 365, 393 and 575 post-immunization. Results showed that S19 and RB51 vaccination induced an immune response characterized by proliferation of CD4+ and CD8+ T-cells; IFN-ɣ and IL-17A production by CD4+ T-cells; cytotoxic CD8+ T-cells; IL-6 secretion; CD4+ and CD8+ memory cells; antibodies of IgG1 class; and expression of the phenotypes of activation in T-cells. However, the immune response stimulated by S19 compared to RB51 showed higher persistency of IFN-ɣ and CD4+ memory cells, induction of CD21+ memory cells and higher secretion of IL-6. After RB51 revaccination, the immune response was chiefly characterized by increase in IFN-ɣ expression, proliferation of antigen-specific CD4+ and CD8+ T-cells, cytotoxic CD8+ T-cells and decrease of IL-6 production in both groups. Nevertheless, a different polarization of the immune response, CD4+- or CD8+-dominant, was observed after the booster with RB51 for S19 and RB51 prime-vaccinated animals, respectively. Our results indicate that after prime vaccination both vaccine strains induce a strong and complex Th1 immune response, although after RB51 revaccination the differences between immune profiles induced by prime-vaccination become accentuated.

Dietary polyunsaturated fatty acids from flaxseed affect immune responses of dairy sheep around parturition

The objective of the study was to characterize the immune profile of dairy ewes fed flaxseed, rich in polyunsaturated fatty acids (PUFA), around parturition. The hypothesis to be verified was that a physiological stressor, such as parturition, could be overcome with a nutritional manipulation in the diet of the animal in order to guarantee welfare of animals and to sustain their immune responses. Twenty Comisana ewes were divided in two groups (10 ewes/group), and fed a supplementation of whole flaxseed in the diet (FS group) or no supplementation (CON group). Blood samples were collected at parturition and then 7, 14, 21, 28, and 42 day post partum. Plasma samples were used to assess the humoral immune response after ovalbumin (OVA) immunization. At parturition, at 14 day, and 42 day post partum the level of plasma cytokines was assessed. The sheep showed a reduced responsiveness to OVA immunization. In FS ewes the IL-6 level remained unchanged until 14 day post partum and then significantly decreased from 14 day to 42 day post partum. IL-10 level was significantly higher in FS ewes than in CON ewes at 14 day. At parturition IL-1β level was significantly lower in FS ewes than in CON ewes and significantly decreased in both groups from parturition to 42 day. In conclusion, PUFA from flaxseed, as supplement in the diet of ewes around parturition can modulate sheep immune reactivity by influencing cytokine production.

Lipopolysaccharide-Induced Preconditioning Attenuates Apoptosis and Differentially Regulates TLR4 and TLR7 Gene Expression after Ischemia in the Preterm Ovine Fetal Brain

Acute exposure to subclinical infection modulates subsequent hypoxia-ischemia (HI) injury in a time-dependent manner, likely by cross-talk through Toll-like receptors (TLRs), but the specific pathways are unclear in the preterm-equivalent brain. In the present study, we tested the hypothesis that repeated low-dose exposure to lipopolysaccharide (LPS) before acute ischemia would be associated with induction of specific TLRs that are potentially neuroprotective. Fetal sheep at 0.65 gestation (term is ∼145 days) received intravenous boluses of low-dose LPS for 5 days (day 1, 50 ng/kg; days 2-5, 100 ng/kg) or the same volume of saline. Either 4 or 24 h after the last bolus of LPS, complete carotid occlusion was induced for 22 min. Five days after LPS, brains were collected. Pretreatment with LPS for 5 days decreased cellular apoptosis, microglial activation and reactive astrogliosis in response to HI injury induced 24 but not 4 h after the last dose of LPS. This was associated with upregulation of TLR4, TLR7 and IFN-β mRNA, and increased fetal plasma IFN-β concentrations. The association of reduced white matter apoptosis and astrogliosis after repeated low-dose LPS finishing 24 h but not 4 h before cerebral ischemia, with central and peripheral induction of IFN-β, suggests the possibility that IFN-β may be an important mediator of endogenous neuroprotection in the developing brain.

Design and evaluation of a unique SYBR Green real-time RT-PCR assay for quantification of five major cytokines in cattle, sheep and goats

Background

Today, when more than 60% of animal diseases are zoonotic, understanding their origin and development and identifying protective immune responses in ruminants are major challenges. Robust, efficient and cost-effective tools are preconditions to solve these challenges. Cytokines play a key role in the main mechanisms by which the immune system is balanced in response to infectious pathogens. The cytokine balance has thus become the focus of research to characterize immune response in ruminants. Currently, SYBR Green reverse transcriptase quantitative PCR (RT-qPCR) is the most widely method used to investigate cytokine gene expression in ruminants, but the conditions in which the many assays are carried out vary considerably and need to be properly evaluated. Accordingly, the quantification of gene expression by RT-qPCR requires normalization by multiple reference genes. The objective of the present study was thus to develop an RT-qPCR assay to simultaneously quantify the expression of several cytokines and reference genes in three ruminant species. In this paper, we detail each stage of the experimental protocol, check validation parameters and report assay performances, following MIQE guidelines.

Results

Ten novel primer sets were designed to quantify five cytokine genes (IL-4, IL-10, IL-12B, IFN-γ and TNF-α) and five reference genes (ACTB, GAPDH, H3F3A, PPIA and YWHAZ) in cattle, sheep, and goats. All the primer sets were designed to span exon-exon boundaries and use the same hybridization temperature. Each stage of the RT-qPCR method was detailed; their specificity and efficiency checked, proved and are reported here, demonstrating the reproducibility of our method, which is capable of detecting low levels of cytokine mRNA up to one copy whatever the species. Finally, we checked the stability of candidate reference gene expression, performed absolute quantification of cytokine and reference gene mRNA in whole blood samples and relative expression of cytokine mRNA in stimulated PBMC samples.

Conclusions

We have developed a novel RT-qPCR assay for the simultaneous relative quantification of five major cytokines in cattle, sheep and goats, and their accurate normalization by five reference genes. This accurate and easily reproducible tool can be used to investigate ruminant immune responses and is widely accessible to the veterinary research community.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0382-0) contains supplementary material, which is available to authorized users.

Immunity, safety and protection of an Adenovirus 5 prime--Modified Vaccinia virus Ankara boost subunit vaccine against Mycobacterium avium subspecies paratuberculosis infection in calves

Vaccination is the most cost effective control measure for Johne’s disease caused by Mycobacterium avium subspecies paratuberculosis (MAP) but currently available whole cell killed formulations have limited efficacy and are incompatible with the diagnosis of bovine tuberculosis by tuberculin skin test. We have evaluated the utility of a viral delivery regimen of non-replicative human Adenovirus 5 and Modified Vaccinia virus Ankara recombinant for early entry MAP specific antigens (HAV) to show protection against challenge in a calf model and extensively screened for differential immunological markers associated with protection. We have shown that HAV vaccination was well tolerated, could be detected using a differentiation of infected and vaccinated animals (DIVA) test, showed no cross-reactivity with tuberculin and provided a degree of protection against challenge evidenced by a lack of faecal shedding in vaccinated animals that persisted throughout the 7 month infection period. Calves given HAV vaccination had significant priming and boosting of MAP derived antigen (PPD-J) specific CD4⁺, CD8⁺ IFN-γ producing T-cell populations and, upon challenge, developed early specific Th17 related immune responses, enhanced IFN-γ responses and retained a high MAP killing capacity in blood. During later phases post MAP challenge, PPD-J antigen specific IFN-γ and Th17 responses in HAV vaccinated animals corresponded with improvements in peripheral bacteraemia. By contrast a lack of IFN-γ, induction of FoxP3+ T cells and increased IL-1β and IL-10 secretion were indicative of progressive infection in Sham vaccinated animals. We conclude that HAV vaccination shows excellent promise as a new tool for improving control of MAP infection in cattle.

Investigation of immunity in sheep following footrot infection and vaccination

Ovine footrot is a major disease affecting sheep welfare and production. The anaerobic Gram-negative bacterium Dichelobacter nodosus is the essential transmitting agent. Monovalent or bivalent vaccines induce high levels of D. nodosus antibodies and are the basis of several successful footrot treatment, control and eradication programs. Due to the rapid rate of disease transmission within a flock, the presence of therapeutic vaccination non-responders has major implications for a control program. The aim of this study was to assess the immunological basis of a therapeutic vaccination non-response. Sheep (n=120) were infected with D. nodosus in an artificial pen challenge. Once disease had established, animals were vaccinated with a serogroup specific D. nodosus fimbrial vaccine. Based on the response to therapeutic vaccination, animals were allocated into one of three groups: (i) TVNR where disease persisted despite vaccination (ii) non-diseased, where disease never established and (iii) TVR, where disease was established but resolved with vaccination. Factors related to both the innate and adaptive immune pathways were assessed. These included antigen-specific serum antibodies, interferon-γ, interleukin-10, proliferation of lymphocyte subsets and phagocytic activity of leukocytes. There was no significant difference between the three groups of sheep for any of these parameters. All three groups of sheep produced antibody in excess of a previously published minimum antibody titre required for protection. Opsonising activity in sera from the three groups of sheep was also not significantly different and phagocytic cells from sheep from all three groups were able to destroy D. nodosus intracellularly. These findings show that the measured systemic adaptive and innate immune responses were unlikely to be the cause of a therapeutic vaccination non-response. They also show that the accepted minimum protective titre may be incorrect and may need further examination.

Stress-induced behavioral and metabolic adaptations lead to an obesity-prone phenotype in ewes with elevated cortisol responses

The underlying cause of predisposition to obesity is complex but one marker is cortisol responsiveness. Selection of sheep for high (HR) or low (LR) cortisol responses to adrenocorticotropin shows that HR are more likely to become obese. Increased propensity to obesity is associated with reduced skeletal muscle thermogenesis. We sought to determine whether metabolic or behavioral responses to stress also contribute to altered propensity to obesity in LR and HR. Animals (n=5-10/group) were exposed to 3 stressors and we measured food intake and thermogenesis (recorded with dataloggers implanted into muscle). Stressors were hypoglycaemia (0.125 units/kg insulin, IV), a barking dog and immune challenge (200 ng/kg lipopolysaccharide--LPS, IV). LR animals showed a greater catabolic state in response to both immune and psychosocial stressors. LPS reduced (P<0.01) food intake in both groups but LR showed a greater (P<0.05) reduction in food intake and a more substantial (P<0.05) rise in muscle temperature. Introduction of the barking dog reduced (P<0.05) food intake in LR only. These metabolic differences coincided with differences in cortisol responsiveness, where HR animals had increased (P<0.05) cortisol in response to both immune and psychosocial stressors. We also assessed behavior in the following paradigms: 1, isolation in the open field test; 2, response to a human intruder; and 3, food competition. LR had greater (P<0.05) activity, reduced fearfulness and displayed a proactive coping style of behavior. Thus we demonstrate that high cortisol responsiveness identifies animals with stress-induced metabolic and behavioral traits that may contribute to susceptibility to obesity.

Hypothalamic-pituitary-adrenal axis activation and immune regulation in heat-stressed sheep after supplementation with polyunsaturated fatty acids

The aim of this study was to assess the effects of supplementation with polyunsaturated fatty acids from different sources on immune regulation and hypothalamic-pituitary-adrenal (HPA) axis activation in heat-stressed sheep. The experiment was carried out during the summer 2012. Thirty-two Comisana ewes were divided into 4 groups (8 sheep/group): (1) supplemented with whole flaxseed (FS); (2) supplemented with Ascophyllum nodosum (AG); (3) supplemented with a combination of flaxseed and A. nodosum (FS+AG); and (4) control (C; no supplementation). On d 22 of the experiment, cortisol concentrations in sheep blood were measured after an injection of ACTH. Cellular immune response was evaluated by intradermic injection of phytohemagglutinin (PHA) at 0, 15, and 30 d of the trial. Humoral response to ovalbumin (OVA) was measured at 0, 15, and 30 d. At 0, 15, and 30 d of the experiment, blood samples were collected from each ewe to determine production of T-helper (Th)1 cytokines (IL-12 and IFN-γ), and Th2 cytokines (IL-10, IL-4, IL-13), and concentrations of heat shock proteins (HSP) 70 and 90. Ewes supplemented with flaxseed alone had greater cortisol concentrations and a longer-lasting cell-mediated immune response compared with ewes in the control and other groups. Anti-OVA IgG concentrations increased in all groups throughout the trial, even though ewes in the FS+AG group had the lowest anti-OVA IgG concentrations at 15 d. The level of IL-10 increased in all groups throughout the experiment; the FS+AG group had the lowest IL-13 concentration at 15 and 30 d. The concentration of HSP 70 increased in AG ewes at the end of the experiment and decreased in FS ewes, whereas that of HSP 90 increased in FS ewes compared with FS+AG ewes. Flaxseed supplementation was found to influence in vivo HPA activation in heat-stressed sheep, resulting in increased cortisol concentrations, probably to meet increased energy demand for thermoregulation. Flaxseed supplementation also supported Th1 response via a complex cross-talk between IL-10, IL-12, and IFN-γ production.

Bovine γδ T cells are a major regulatory T cell subset

In humans and mice, γδ T cells represent <5% of the total circulating lymphocytes. In contrast, the γδ T cell compartment in ruminants accounts for 15–60% of the total circulating mononuclear lymphocytes. Despite the existence of CD4⁺CD25^high Foxp3⁺ T cells in the bovine system, these are neither anergic nor suppressive. We present evidence showing that bovine γδ T cells are the major regulatory T cell subset in peripheral blood. These γδ T cells spontaneously secrete IL-10 and proliferate in response to IL-10, TGF-β, and contact with APCs. IL-10–expressing γδ T cells inhibit Ag-specific and nonspecific proliferation of CD4⁺ and CD8⁺ T cells in vitro. APC subsets expressing IL-10 and TFG-β regulate proliferation of γδ T cells producing IL-10. We propose that γδ T cells are a major regulatory T cell population in the bovine system.

Giardia duodenalis stimulates partial maturation of bovine dendritic cells associated with altered cytokine secretion and induction of T-cell proliferation

Giardia duodenalis is an important intestinal parasite in animals and humans. The role of dendritic cells (DC) in the initiation of the immune response against G. duodenalis is poorly documented. The aim of this study was to test the hypothesis that G. duodenalis interferes with bovine DC function. Therefore, the effect of trophozoites and excretion/secretion products on bovine monocyte-derived dendritic cells (MoDC) was investigated. We assessed MoDC maturation and cytokine production of G. duodenalis-stimulated MoDC and the ability of these MoDC to take up antigen and induce lymphocyte proliferation. Little or no upregulation of maturation markers CD40 and CD80 was measured, but MHCII expression was increased after stimulation with low parasite concentrations. A dose-dependent decrease in ovalbumin uptake was observed in G. duodenalis-stimulated MoDC. In addition, stimulated MoDC induced proliferation of CD3(-) , γδ-T-cells and TCRαβ(+) CD4(+) and CD8(+) T-cells. Increased transcription of TGF-β was shown in CD4(+) T cells, and increased TNF-α, TGF-β, IL-10 and IL-4 were seen in γδ-T-cells. We found no evidence that G. duodenalis has a regulatory or inhibitory effect on bovine MoDC. MoDC stimulated with G. duodenalis are functionally active and able to induce proliferation of T cells that produce both pro- and anti-inflammatory cytokines.

IL-10 secreting CD21⁺ B cells are present in jejunal Peyer's patches of sheep during fetal development

We recently reported a novel interleukin-10 (IL-10)-secreting CD21(+) B cell population in jejunal Peyer's patches (JPP) of sheep with a regulatory function (Bregs) suppressing Toll-like receptor 9 (TLR9)-induced cytokine responses. However, little is known about the development of these cells. Therefore, we investigate their existence in JPP cells from fetal and newborn lambs. CD21(+) B cells were purified from JPP cells by magnetic cell sorting and subsequently stimulated with the TLR9 agonist, CpG ODN (CpG oligodeoxynucleotide). Lymphocyte proliferative responses, cytokine production (IL-10, IL-12 and interferon-γ [INF-γ]) and antibody secretion were assayed. We found that fetal and neonatal CD21(+) B cells spontaneously secreted high levels of IL-10 regardless of CpG stimulation but that these cells did not produce any IL-12 or INF-γ upon stimulation with CpG. The observed responses are consistent with those previously reported for Bregs characterized in JPP of older lambs. Surprisingly, unlike in older lambs, fetal and neonatal JPP CD21(+) B cells proliferated in response to CpG stimulation. Our investigations of fetal and neonatal lambs provide evidence for the development of IL-10-secreting CD21(+) B cells in PPs prior to antigen exposure.

Development of maternal and foetal immune responses in cattle following experimental challenge with Neospora caninum at day 210 of gestation

This study examined the immunological responses of pregnant cattle and their foetuses following an experimental challenge with live Neospora caninum tachyzoites at day 210 of gestation. Animals were bled prior to and weekly throughout the experiment and sacrificed at 14, 28, 42 and 56 days post inoculation (dpi). At post mortem examination, samples of lymph nodes and spleen were collected from both dam and foetus for immunological analysis. Subcutaneous (sc) inoculation over the left prefemoral (LPF) lymph node of pregnant cattle at day 210 of gestation, led to the vertical transmission of parasites by 14 dpi, however no foetal deaths were observed in the infected animals. Foetuses from infected dams mounted Neospora-specific humoral and cell-mediated immune (CMI) responses by 14 dpi. These responses involved anti-Neospora IgG, antigen-specific lymphocyte proliferation, and the production of the cytokines IFN–γ, interleukin (IL)-4 and IL-10. There was also evidence of innate immunity during the response against Neospora from infected dams, with statistically significant (p < 0.05) increases in mean expression of toll like receptors (TLR)-2 on 56 dpi in maternal spleen, LPF, right prefemoral (RPF), left uterine (LUL) and right uterine (RUL) lymph nodes and TLR-9 in retropharyngeal (RLN), LPF and RPF lymph nodes from 28 dpi. Statistically significant (p < 0.05) increases in mean TLR-9 were detected in spleen samples from foetuses of infected dams, compared to the foetuses from control animals. Our results show that vertical transmission of the parasite occurred in all infected dams, with their foetuses showing effective Neospora-specific cell mediated, humoral and innate immune responses.

Mannosylated lipoarabinomannans from Mycobacterium avium subsp. paratuberculosis alters the inflammatory response by bovine macrophages and suppresses killing of Mycobacterium avium subsp. avium organisms

Analysis of the mechanisms through which pathogenic mycobacteria interfere with macrophage activation and phagosome maturation have shown that engagement of specific membrane receptors with bacterial ligands is the initiating event. Mannosylated lipoarabinomannan (Man-LAM) has been identified as one of the ligands that modulates macrophage function. We evaluated the effects of Man-LAM derived from Mycobacterium avium subsp. paratuberculosis (MAP) on bovine macrophages. Man-LAM induced a rapid and prolonged expression of IL-10 message as well as transient expression of TNF-α. Preincubation with Man-LAM for up to 16 h did not suppress expression of IL-12 in response to interferon-γ. Evaluation of the effect of Man-LAM on phagosome acidification, phagosome maturation, and killing of Mycobacterium avium subsp. avium (MAA) showed that preincubation of macrophages with Man-LAM before addition of MAA inhibited phagosome acidification, phagolysosome fusion, and reduced killing. Analysis of signaling pathways provided indirect evidence that inhibition of killing was associated with activation of the MAPK-p38 signaling pathway but not the pathway involved in regulation of expression of IL-10. These results support the hypothesis that MAP Man-LAM is one of the virulence factors facilitating survival of MAP in macrophages.

Suppression of ovine lymphocyte activation by Teladorsagia circumcincta larval excretory-secretory products

Teladorsagia circumcincta is an important pathogenic nematode of sheep. It has been demonstrated previously that stimulation of murine T lymphocytes with excretory-secretory (ES) products derived from fourth stage larvae of T. circumcincta (Tci-L4-ES) results in de novo expression of Foxp3, a transcription factor intimately involved in regulatory T cell function. In the current study, Foxp3⁺ T cell responses in the abomasum and the effects of Tci-L4-ES on ovine peripheral blood mononuclear cells (PBMC) following T. circumcincta infection were investigated. T. circumcincta infection resulted in a significant increase in numbers of abomasal Foxp3⁺ T cells, but not an increase in the proportion of T cells expressing Foxp3. Unlike in mice, Tci-L4-ES was incapable of inducing T cell Foxp3 expression but instead suppressed mitogen-induced and antigen-specific activation and proliferation of ovine PBMC in vitro. This effect was heat labile, suggesting that it is mediated by protein(s). Suppression was associated with up-regulation of interleukin-10 (IL-10) mRNA, and specific monoclonal antibody neutralisation of IL-10 resulted in a 50% reduction in suppression, indicating involvement of the IL-10 signaling pathway. Suppression was significantly reduced in PBMC isolated from T. circumcincta infected vs. helminth-naïve lambs, and this reduction in suppression was associated with an increase in Tci-L4-ES antigen-specific T cells within the PBMC. In conclusion, we have identified a mechanism by which T. circumcincta may modulate the host adaptive immune response, potentially assisting survival of the parasite within the host. However, the impact of Tci-L4-ES-mediated lymphocyte suppression during T. circumcincta infection remains to be determined.

Differential chemokine and cytokine production by neonatal bovine γδ T-cell subsets in response to viral toll-like receptor agonists and in vivo respiratory syncytial virus infection

γδ T cells respond to stimulation via toll-like receptors (TLR). Bovine γδ T cells express TLR3 and TLR7, receptors that are key for the recognition of viruses such as bovine respiratory syncytial virus (BRSV); however, responses of γδ T cells to stimulation via these receptors, and their role during viral infections, remains unclear. Here, we demonstrate that neonatal bovine γδ T cells exhibit robust chemokine and cytokine production in response to the TLR3 agonist, Poly(I:C), and the TLR7 agonist, Imiquimod. Importantly, we observe a similar phenotype in γδ T-cell subsets purified from calves infected with BRSV. Bovine γδ T cells are divided into subsets based upon their expression of WC1, and the response to TLR stimulation and viral infection differs between these subsets, with WC1.1(+) and WC1(neg) γδ T cells producing macrophage inflammatory protein-1α and granulocyte-macrophage colony-stimulating factor, and WC1.2(+) γδ T cells preferentially producing the regulatory cytokines interleukin-10 and transforming growth factor-β. We further report that the active vitamin D metabolite 1,25-dihydroxyvitamin D3 does not alter γδ T-cell responses to TLR agonists or BRSV. To our knowledge, this is the first characterization of the γδ T-cell response during in vivo BRSV infection and the first suggestion that WC1.1(+) and WC1(neg) γδ T cells contribute to the recruitment of inflammatory populations during viral infection. Based on our results, we propose that circulating γδ T cells are poised to rapidly respond to viral infection and suggest an important role for γδ T cells in the innate immune response of the bovine neonate.

Immune competence of the mammary gland as affected by somatic cell and pathogenic bacteria in ewes with subclinical mastitis

Immune competence of the ewe mammary gland was investigated by monitoring the leukocyte differential count, cytokine pattern, and endogenous proteolytic enzymes in milk samples with different somatic cell counts (SCC) and pathogenic bacteria. Furthermore, the leukocyte differential count and T-lymphocyte populations were evaluated in ewe blood. A total of 1,500 individual milk samples were randomly selected from the pool of the samples collected during sampling and grouped into 5 classes of 300 samples each, on the basis of SCC. Classes were <300,000 cells/mL, from 300,000 to 500,000 cells/mL, from 501,000 to 1,000,000 cells/mL, from 1,001,000 to 2,000,000 cells/mL, and >2,000,000 cells/mL. Microbiological analyses of ewe milk were conducted to detect mastitis-related pathogens. Sheep whose udders were without clinical abnormalities, and whose milk was apparently normal but with at least 10(3)cfu/mL of the same pathogen were considered to have subclinical mastitis and therefore defined as infected. Polymorphonuclear neutrophilic leukocytes (PMNL) and macrophages increased with SCC, whereas lymphocytes decreased. Milk samples with SCC >1,000,000 cells/mL showed differences in leukocyte populations between uninfected and infected ewes, with higher percentages of PMNL and macrophages and lower percentages of lymphocytes in infected animals. Nonviable PMNL levels were the highest in ewe milk samples with SCC <300,000 cells/mL; starting from SCC >500,000 cells/mL, nonviable PMNL were higher in uninfected ewes than in infected ones. In infected animals giving milk with SCC >1,000,000 cells/mL, a higher CD4(+)/CD8(+) ratio was observed, suggesting that the presence of pathogens induced an activation of both CD4(+) and CD8(+). The levels of tumor necrosis factor-α and IL-12 were higher in infected than uninfected ewes, irrespective of SCC. Plasmin activity increased along with SCC and was always higher in infected than uninfected animals; cathepsin D increased starting from 1,001,000 cells/mL in milk samples from noninfected ewes and starting from 301,000 cells/mL in milk samples from infected animals. The associations between somatic cells, cytokines, endogenous proteolytic enzymes, and pathogenic bacteria can be used to better understand the pathogenesis of subclinical mastitis in ewes and the effect on the immune response of ewe mammary gland.