Pulmonary Expression of Tumor Necrosis Factor Alpha, Interleukin-1 Beta, and Interleukin-8 in the Acute Phase of Bovine Pneumonic Pasteurellosis

Responses of selected biomarkers, female reproductive hormones and tissue changes in non-pregnant does challenged with Mannheimia haemolytica serotype A2 and its outer membrane protein (OMP) immunogen

BACKGROUND

Mannheimia haemolytica causative agent of pneumonic mannheimiosis, a common respiratory disease of goat and sheep, which cause huge economic losses to farmers worldwide. Pneumonic mannheimiosis caused by M. haemolytica serotype A2 has been reported among small ruminants in Malaysia. The lipopolysaccharide (LPS) and outer membrane protein (OMP) are major virulence determinants for M. haemolytica serotype A2. Although pneumonic mannheimiosis is known to cause poor reproductive performance in small ruminants under field conditions, there is a dearth of published information on the specific effects of M. haemolytica serotype A2 infection on the female reproductive physiology. In this experiment, we explored the impact of M. haemolytica serotype A2 and its OMP immunogen on selected pro-inflammatory cytokines, acute phase proteins, female reproductive hormones, and cellular changes in visceral and female reproductive organs of non-pregnant does.

METHODOLOGY

Twelve healthy, non-pregnant, Boer crossbreds does were divided equally into three groups (n = 4); Group 1 served as the negative control and was challenged with 2 ml of sterile PBS intranasally. Group 2 served as the positive control and was challenged with 2 ml of 10⁹ colonies forming unit (CFU) of M. haemolytica serotype A2 suspension intranasally. Group 3 was challenged with 2 ml of OMP extracted from 10⁹ CFU of M. haemolytica A2 intramuscularly. The experimental does were monitored for clinical signs and responses periodically. Blood samples were collected at 0, 1, 2, 4, 6, 12 and 24 h and 3, 7, 21, 35 and 56 days post treatment for serological analyses. All does were euthanised using the halal slaughter method on day 60 post challenge/treatment. Tissues from the uterus, liver, lung and associated bronchial lymph nodes were collected and fixed in 10% formalin for 14 days for histopathological study.

RESULTS

Compared to the control group, the challenged/treated groups showed significant (p < 0.05) increase in the rectal temperature, respiratory rate, heart rate, and rumen motility. Serum analyses revealed that the concentrations of progesterone and estrogen hormones were significantly (p < 0.05) decreased in groups 2 & 3. In contrast, the concentrations of pro-inflammatory cytokines (IL-1β and IL-6) and acute phase proteins (Hp and SAA) were significantly increased (p < 0.05) in the challenged/treated groups compared to the control group. Histopathological lesion scoring revealed mild to moderate cellular changes characterised by congestion, haemorrhage, degeneration, leucocytic cellular infiltration, and cellular necrosis in the tissues of does from the OMP treatment and bacterial challenge groups compared to the control group.

CONCLUSION

The findings from this study suggests that M. haemolytica serotype A2 and its OMP immunogen induced mild to moderate inflammatory and degenerative changes which may potentially interfere with fertilization through hormonal imbalances and cause temporary loss of fertility in infected does.

Hematological and immunological responses to naturally occurring bovine respiratory disease in newly received beef calves in a commercial stocker farm

The objective was to determine temporal changes in hematological and immune parameters in response to naturally occurring bovine respiratory disease (BRD) in commercially managed stocker calves. Forty newly weaned beef steers purchased from auction markets were housed at a commercial stocker operation in Crossville, TN. Blood samples, rectal temperature, and thoracic ultrasonography (TUS; 1: normal to 3: severe) were collected on days 0, 7, 14, and 21. Castration status (FC: freshly castrated; PC: previously castrated) was determined on arrival based on presence of a fresh castration site at the scrotum. Calves received antibiotics for BRD based on clinical severity scoring (CSS; 0: moribund, 4: moribund) and rectal temperature. Complete blood counts (CBC) were performed. Calves were categorized based on the number of treatments (NumTrt) received (0x, 1x, and 2x). Temporal variations in CBC and immune parameters were analyzed using mixed model repeated measure ANOVA (Proc GLIMMIX; SAS 9.4). Variation of CBCs and immune parameters based on TUS was determined using mixed model ANOVA. There was a NumTrt by day interaction effect on the responses of white blood cells (WBC) (P = 0.04) and haptoglobin (HPT) (P = 0.04). On day 21, WBC were greater in the 2x NumTrt group than other groups, but there were no differences in WBC between NumTrt levels on other days. Haptoglobin was greater in the 2x group on days 14 and 21 than 0x or 1x. Red blood cells (RBC) (P = 0.02) and WBC (P = 0.04) differed between FC and PC groups, and lower RBC and WBC were observed in the FC group. A castration status × day effect for mean corpuscular volume (MCV; P = 0.04) was observed where FC group had higher MCV at days 14 and 21 than the PC group. Tumor necrosis factor-α differed based on NumTrt (P = 0.03) and higher concentrations were found in 2x group. We observed a day effect for IL-1β (P = 0.009) and TNF-α (P = 0.001). Significant effect of TUS on HPT at day 14 (P = 0.0004) and day 21 (P = 0.002) was observed. Combining HPT and platelet explained 15% of the variability in treatment status on a given day, whereas HPT and hemoglobin explained 10% of the variability in lung consolidation status. Although hematological and immunological parameters varied largely in our study, the potential of combining HPT with hematological variables should be studied further. Results from this study would help in understanding temporal changes in CBC and immune parameters in newly received stocker cattle.

Immunomodulatory Effect of Vitamin C on Proinflammatory Cytokines Production in Ossimi Lambs (Ovis aries) with Pneumonic Pasteurellosis

In this study, we have investigated the impact of vitamin C on the production of pro-inflammatory cytokines (interleukin 1 β (IL-1 β), interleukin 6 (IL-6), interleukin 12p40 (IL-12p40), interferon gamma (IFNγ), and tumor necrosis factor alpha (TNF-α)) in lambs naturally infected by pneumonic pasteurellosis. Of 37 lambs, 18 lambs were identified to have pneumonic pasteurellosis and randomly allocated into two equal groups. Single subcutaneous dose of tulathromycine alone (2.5 mg kg−1) or tulathromycine combined with vitamin C (3 gm kg−1) were administrated to the diseased lambs. The serum levels of IL-1β, IL-6, IFN-γ, and TNF-α were returned to the normal levels in pneumonic lambs treated with the combination therapy. The obtained results indicate the selective influences of vitamin C on pro-inflammatory cytokines production in sera of lambs with pneumonic pasteurellosis and highlights the value of vitamin C as a potential anti-inflammatory drug and ideal immunomodulatory agent.

Integrated Network Analysis to Identify Key Modules and Potential Hub Genes Involved in Bovine Respiratory Disease: A Systems Biology Approach

Background: Bovine respiratory disease (BRD) is the most common disease in the beef and dairy cattle industry. BRD is a multifactorial disease resulting from the interaction between environmental stressors and infectious agents. However, the molecular mechanisms underlying BRD are not fully understood yet. Therefore, this study aimed to use a systems biology approach to systematically evaluate this disorder to better understand the molecular mechanisms responsible for BRD. Methods: Previously published RNA-seq data from whole blood of 18 healthy and 25 BRD samples were downloaded from the Gene Expression Omnibus (GEO) and then analyzed. Next, two distinct methods of weighted gene coexpression network analysis (WGCNA), i.e., module-trait relationships (MTRs) and module preservation (MP) analysis were used to identify significant highly correlated modules with clinical traits of BRD and non-preserved modules between healthy and BRD samples, respectively. After identifying respective modules by the two mentioned methods of WGCNA, functional enrichment analysis was performed to extract the modules that are biologically related to BRD. Gene coexpression networks based on the hub genes from the candidate modules were then integrated with protein-protein interaction (PPI) networks to identify hub-hub genes and potential transcription factors (TFs). Results: Four significant highly correlated modules with clinical traits of BRD as well as 29 non-preserved modules were identified by MTRs and MP methods, respectively. Among them, two significant highly correlated modules (identified by MTRs) and six nonpreserved modules (identified by MP) were biologically associated with immune response, pulmonary inflammation, and pathogenesis of BRD. After aggregation of gene coexpression networks based on the hub genes with PPI networks, a total of 307 hub-hub genes were identified in the eight candidate modules. Interestingly, most of these hub-hub genes were reported to play an important role in the immune response and BRD pathogenesis. Among the eight candidate modules, the turquoise (identified by MTRs) and purple (identified by MP) modules were highly biologically enriched in BRD. Moreover, STAT1, STAT2, STAT3, IRF7, and IRF9 TFs were suggested to play an important role in the immune system during BRD by regulating the coexpressed genes of these modules. Additionally, a gene set containing several hub-hub genes was identified in the eight candidate modules, such as TLR2, TLR4, IL10, SOCS3, GZMB, ANXA1, ANXA5, PTEN, SGK1, IFI6, ISG15, MX1, MX2, OAS2, IFIH1, DDX58, DHX58, RSAD2, IFI44, IFI44L, EIF2AK2, ISG20, IFIT5, IFITM3, OAS1Y, HERC5, and PRF1, which are potentially critical during infection with agents of bovine respiratory disease complex (BRDC). Conclusion: This study not only helps us to better understand the molecular mechanisms responsible for BRD but also suggested eight candidate modules along with several promising hub-hub genes as diagnosis biomarkers and therapeutic targets for BRD.

Responses of testosterone hormone and important inflammatory cytokines in bucks after challenge with Mannheimia haemolytica A2 and its LPS endotoxin

Previous studies have shown that Mannheimia haemolytica A2 is the principal microorganism causing pneumonic mannheimiosis, a major bacterial respiratory disease among sheep and goats. The effect of this bacteria on the respiratory system is well-established. However, its effect on the reproductive physiology remains unclear. Therefore, this study aimed to determine the alterations in the level of pro-inflammatory cytokines and testosterone hormone post-inoculation with M. haemolytica serotype A2 and its lipopolysaccharide (LPS) endotoxin which were hypothesized to affect the reproductive functions of bucks. Twelve clinically healthy adult male goats were divided equally into three groups. Goats in group 1 were treated with 2 ml of sterile phosphate-buffered saline (PBS) pH 7.0 intranasally (negative control), group 2 with 2 ml of 10⁹ colony-forming unit (CFU) of M. haemolytica serotype A2 intranasally (positive control), and group 3 were treated with 2 ml of lipopolysaccharide extracted from 10⁹ CFU of M. haemolytica serotype A2 intravenously. Following inoculation, blood samples were collected via jugular venipuncture into plain tubes at pre-determined intervals for serum collection to determine the concentration of interleukin (IL)-1β, IL6, tumor necrosis factor (TNF)-α, and testosterone hormone by using commercial ELISA test kits. Results from this study demonstrated that the inoculation of M. haemolytica A2 and its LPS increases the concentration of pro-inflammatory cytokines but decreases the concentration of testosterone hormone in challenged animals at most time points throughout the 56 days experimental period (p < 0.05). This study suggests that the M. haemolytica A2 and its LPS could alter the concentration of pro-inflammatory cytokines and testosterone hormone, which in turn, may negatively affect the reproductive functions of bucks.

Investigation of acute-phase proteins and cytokines response in goats with contagious caprine pleuropneumonia with special reference to their diagnostic accuracy

Acute-phase proteins (APPs) have always had valued diagnostic potentialities in response to infection. This study aimed to evaluate the diagnostic accuracy of selected APPs and proinflammatory cytokines (PIC) in goats with contagious caprine pleuropneumonia (CCPP) under field conditions. Moreover, to highlight the role of tested biomarkers in CCPP pathogenesis. Fifty-eight goats (38 confirmed cases with CCPP and 20 healthy controls) were involved in this investigation. C-reactive protein (CRP), procalcitonin (PCT), haptoglobin (HP), fibrinogen (Fb), serum amyloid A (SAA), selected PIC (IL1-α, IL1-β, IL-6, interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α)) levels were investigated in serum samples from all goats under investigation. Latex agglutination test was used for diagnosis of goats with CCPP. For microbiological investigations, nasopharyngeal swabs (from all goats), lung tissues and pleural fluids (from only necropsied goats) were collected. This study revealed that all tested parameters have a high to moderate degree of diagnostic performance for CCPP. Magnitudes of increase in levels of APPs (CRP, HP and SAA) were stronger than PIC, IFN-γ, Fb and PCT. All tested parameters showed high diagnostic accuracy (AUROC >90%), except HP (AUROC = 87.3%) and IFN-γ (AUROC = 78.8%) showed moderate accuracy in differentiation of goats with and without CCPP infection. For detecting goats with and without CCPP infection, HP had the lowest sensitivity (Se = 81.6%) and Fb had the lowest specificity (Sp = 85.0%) among the APPs parameters tested. However, PCT showed the highest Se (100%) and Sp (95.0%) to detect goats with and without CCPP infection among tested parameters. Conclusively, this study endorses the significance of selected APPs and PIC as additional screening diagnostic parameters for naturally occurring CCPP in goats. However, it does not replace traditional methods for diagnosis of CCPP in goats. Furthermore, APPs and PIC have an important role in disease pathogenesis in goats.

Changes in blood biomarkers in Arabian horses with Clostridium difficile-induced enterocolitis

Clostridium difficile (CD) is considered a major health care problem both in developing and developed countries; frequently reported to be associated with enterocolitis and diarrhea in horses and other animals. In this study, we examined acute phase response (APR), cytokines response, neopterin (NP) procalcitonin (PCT) production and oxidative stress condition in horses and foals with C. difficile-induced enterocolitis (CDIE) and evaluated the effectiveness of these parameters as biomarkers for the disease. A total of 407 Arabian horses in 35 stables were examined between January 2017 to December 2018. Only 24 out of 407 horses showed two or more signs of CDIE. The blood level of serum amyloid A (SAA), haptoglobin (HP), proinflammatory cytokines (TNF-α, IL-6 and IL1-β), serum malondialdehyde (MDA), PCT and NPT in horses with CDIE were higher than in healthy horses. Nevertheless, the levels of nitric oxide (NO), superoxide dismutase (SOD) and total antioxidant concentration (TAC) were considerably lower in diseased horses compared to those that were healthy. The ROC curves for eleven selected blood parameters, both in healthy horses and horses with CDIE demonstrated that all examined blood markers had significant levels of differentiation between CDIE cases and healthy controls (AUC > 87.5). The data in this study suggest that the evaluation of acute-phase proteins, cytokines, PCT, NPT, and oxidative stress biomarkers may well be used as a tool for diagnosis and assessment of CDIE and in disease pathogenesis in Arabian horses.

Pulmonary and systemic responses to aerosolized lysate of Staphylococcus aureus and Escherichia coli in calves

Background

Constitutive and inducible defenses protect the respiratory tract from bacterial infection. The objective of this study was to characterize the response to an aerosolized lysate of killed bacteria, as a basis for studying the regulation and in vivo effects of these inducible innate immune responses.

Results

Bacterial lysate consisting of heat-killed and sonicated Staphylococcus aureus and Escherichia coli was aerosolized to 6 calves and systemic and pulmonary innate immune and inflammatory responses were measured in the first 24 h relative to baseline. Evaluated parameters included clinical parameters (body temperature and heart and respiratory rates), blood acute phase proteins and leukocyte counts, and leukocytes and proteins in bronchoalveolar lavage fluid. Mild clinical signs with increased heart rates and rectal temperatures developed following administration of the lysate, with resolution by 24 h. Serum haptoglobin and plasma fibrinogen concentrations were elevated at 24 h relative to baseline. Bronchoalveolar lavage fluid (BALF) had increased cellularity and increased proportion of neutrophils, as well as higher concentrations of interleukin (IL)-8, IL-10 and total protein at 24 h relative to baseline. Mass spectrometry identified 965 unique proteins in BALF: 19 proteins were increased and 26 proteins were decreased relative to baseline. The upregulated proteins included those involved in innate immunity including activation of complement, neutrophils and platelets. At postmortem examination, calves receiving higher doses of lysate had areas of lobular consolidation and interlobular edema. Histologically, neutrophils were present within bronchioles and to a lesser extent within alveoli. Calves receiving highest doses of lysate had patchy areas of neutrophils, hemorrhage and hyaline membranes within alveoli.

Conclusions

Aerosolization of bacterial lysate stimulated an innate immune response in lungs and airways, with alveolar damage observed at higher doses. Such a stimulus could be of value for investigating the effects of inducible innate immune responses on occurrence of disease, or for evaluating how stress, drugs or genetics affect these dynamic responses of the respiratory tract.

Effects of 1, 25-dihydroxy vitamin D3 on clinical symptoms, pro-inflammatory and inflammatory cytokines in calves with experimental pneumonia

1, 25-dihydroxycholecalciferol is recognized as a potent immune-modulator which can fight against the pathogens via the activation of vitamin D3 receptors (VDRs), as well as stimulating various cytokines in infectious diseases. In the present study, because of the vitamin D3 has an appropriate immunomodulatory, the effects of this vitamin on the levels of pre-inflammatory and anti-inflammatory cytokines have been investigated in calves with experimental pasteurellosis. This study was experimentally carried out on 10 Holstein crossbred male calves (2-4 months) that were divided into two groups. Prepared Pasteurella multocida (3 × 10⁹ CFU/mL) was inoculated in the trachea with a lavage catheter and then the treatment group was injected with 1, 25-dihydroxycholecalciferol after confirming pneumonia. Blood sampling, clinical symptoms scoring and radiological evaluation were recorded for both groups at different time intervals. The prescription of, vitamin D₃ to the treatment group caused a decline in clinical symptoms score and changed interstitial and alveolo-interstitial lung pattern to such a degree that it could recover in comparison with the control group. The concentrations of pro-inflammatory cytokines (i.e., IL-1β, IL-6, and TNF-α) and the chemokine (IL-8) showed a significant decrease in the treatment group while the concentration of IL-10 increased in the treatment groups following the vitamin D₃ injection (P = .001). The evidence from the current study suggests that vitamin D3 exert the immunomodulatory effects in infectious diseases through the regulation of cytokines and activation of VDR pathways to produce antimicrobial peptides.

Use of procalcitonin, neopterin, haptoglobin, serum amyloid A and proinflammatory cytokines in diagnosis and prognosis of bovine respiratory disease in feedlot calves under field conditions

Bovine respiratory diseases (BRD) have long been considered a serious problem that causes major economic losses in feedlot calves (FC). This study aimed to determine the diagnostic and prognostic effect of selected biological markers including, procalcitonin (PCT), neopterin (NP), proinflammatory cytokines (IL-1β, IL-8, TNF-α, IF-γ), haptoglobin (HP) and serum amyloid A (SAA) on FC with BRD under field conditions. Sixty-nine FC that were identified to be infected with Mannheimia haemolytica and Histophilus somni and had different clinical respiratory signs (diseased group) were selected for this study. In addition, 20 healthy FC have been selected as a control group. We have detected higher serum levels of PCT, NP, HP, SAA, IL-1β, IL-8, TNF-α and IF-γ in diseased FC group compared with the control group. All tested markers revealed a high level of discrimination between BRD infected FC and healthy ones (AUC > 0.90). Moreover, the obtained data showed a high degree of prognostic accuracy for PCT, NP, IL-8, HP, IF-γ and IL-1β in predicting treatment response of FC with BRD at the selected thresholds (AUC = 0.99, 0.99, 0.97, 0.93, 0.88 and 0.82, respectively). Significant inhibition was observed for the selected biochemical markers in treated FC 7 days post-treatment. In conclusion, this study showed that BRD in FC was associated with significant alterations in serum APPs, proinflammatory cytokines, PCT and NPT levels. Furthermore, it demonstrated that these serum biomarkers are much higher in FC with BRD compared to recovered ones. Our data suggest that the measurement of PCT, NPT, APPs and cytokines together with the clinical examination may be a useful diagnostic and prognostic tool for assessment of FC naturally infected with M. haemolytica and H. somni.

Pathogenic Mannheimia haemolytica Invades Differentiated Bovine Airway Epithelial Cells

The Gram-negative bacterium Mannheimia haemolytica is the primary bacterial species associated with bovine respiratory disease (BRD) and is responsible for significant economic losses to livestock industries worldwide. Healthy cattle are frequently colonized by commensal serotype A2 strains, but disease is usually caused by pathogenic strains of serotype A1. For reasons that are poorly understood, a transition occurs within the respiratory tract and a sudden explosive proliferation of serotype A1 bacteria leads to the onset of pneumonic disease. Very little is known about the interactions of M. haemolytica with airway epithelial cells of the respiratory mucosa which might explain the different abilities of serotype A1 and A2 strains to cause disease. In the present study, host-pathogen interactions in the bovine respiratory tract were mimicked using a novel differentiated bovine bronchial epithelial cell (BBEC) infection model. In this model, differentiated BBECs were inoculated with serotype A1 or A2 strains of M. haemolytica and the course of infection followed over a 5-day period by microscopic assessment and measurement of key proinflammatory mediators. We have demonstrated that serotype A1, but not A2, M. haemolytica invades differentiated BBECs by transcytosis and subsequently undergoes rapid intracellular replication before spreading to adjacent cells and causing extensive cellular damage. Our findings suggest that the explosive proliferation of serotype A1 M. haemolytica that occurs within the bovine respiratory tract prior to the onset of pneumonic disease is potentially due to bacterial invasion of, and rapid proliferation within, the mucosal epithelium. The discovery of this previously unrecognized mechanism of pathogenesis is important because it will allow the serotype A1-specific virulence determinants responsible for invasion to be identified and thereby provide opportunities for the development of new strategies for combatting BRD aimed at preventing early colonization and infection of the bovine respiratory tract.

Haptoglobin and serum amyloid A as putative biomarker candidates of naturally occurring bovine respiratory disease in dairy calves

Bovine respiratory disease (BRD) is one of the leading causes of morbidity and mortality in dairy calves. Identification of reliable biomarkers of naturally occurring BRD is essential for ensuring early diagnosis and treatment of calves and monitoring treatment efficacy. This need is punctuated, especially in mild to moderate cases that would greatly help to decrease recurrence and the overall prevalence of BRD. The present study was conducted to investigate the changes in serum concentrations of haptoglobin (Hpt) and serum amyloid A (SAA) and association between oxidative stress and acute phase proteins (APPs) in BRD. Hpt and SAA levels significantly increased (P < .01) in BRD stressed calves as compared to healthy subjects. There was a significant decrease (P < .01) in serum albumin (Alb) concentration of infected calves as compared to controls. The oxidative stress markers revealed a significant (P < .01) increase in lipid peroxidation (LPO) and a concurrent decrease in activities of superoxide dismutase (SOD), reduced glutathione (R-GSH) and catalase (CAT) in BRD. A significant correlation among APPs, extent of oxidative stress and clinical score (CS) of calves was depicted. A stepwise decrease in Hpt and SAA and increase in Alb was observed in infected calves post-treatment. These results suggest implication of oxidative stress in enhancing APPs and monitoring of APPs as a potential complement to clinical assessment of treatment in calves with naturally occurring BRD. Hpt may be useful as the most sensitive biomarker in BRD. However, the combined use of Hpt and oxidative stress biomarkers would greatly improve the diagnostic accuracy.

Comparative therapeutic effect of steroidal and non-steroidal anti-inflammatory drugs on pro-inflammatory cytokine production in water buffalo calves (Bubalus bubalis) naturally infected with bronchopneumonia: a randomized clinical trial

In the current study, we compared the therapeutic effects of a non-steroidal and a steroidal anti-inflammatory drug on the production of pro-inflammatory cytokines, interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-12p40 (IL-12p40), interferon gamma (IFNγ), and tumor necrosis factor alpha (TNF-α) in the blood of water buffalo (Bubalus bubalis) calves naturally infected by bronchopneumonia. Twenty-seven buffalo calves (7 ± 2-month-old, 163 ± 12 kg) reared in smallholder farms in El-Dakahlia province in Egypt were identified to have bronchopneumonia and randomly allocated into three equal groups. Ten clinically healthy buffalo calves with negative bronchoalveolar lavage results were served as negative control. Diseased calves were treated with tulathromycin alone, a combination of tulathromycin with dexamethasone (steroidal anti-inflammatory drug) or tulathromycin with flunixin meglumine (non-steroidal anti-inflammatory drug). The results revealed significant elevations (P < 0.05) in the production of selected cytokines in all diseased calves in comparison with healthy animals. Six days post-treatment, a significant inhibition (P < 0.05) in the production of all assessed cytokines was observed in the blood of all treated calves. Interestingly, the serum concentrations of IL-1β and IL-12p40 were returned to the normal levels in pneumonic calves treated with the combination therapy of tulathromycin and flunixin meglumine. A strong significant positive correlation (P < 0.05) was detected between clinical sum scoring and IL-12p40 and TNF-α concentrations. The obtained results indicate the selectively potent anti-inflammatory effect of flunixin meglumine on the production of pro-inflammatory cytokines in pneumonic buffalo calves and highlight the efficacy of flunixin meglumine in the treatment of bronchopneumonia in buffalo calves when used in combination with tulathromycin.

Modulation of immunity and inflammatory gene expression in buffalo (Bubalus bubalis) with some digestive disorders

So far, there has been scarce information about the status of immunoglobulins (Ig) and the gene expression of inflammatory cytokines in buffaloes showing digestive troubles. The purpose of the present study was to explore the modulation of gene expression of some immune-inflammatory markers in buffaloes suffered from various digestive disorders. For this reason, 50 native breed water buffaloes were studied. Forty of these buffaloes showed various symptoms of digestive disorders and were allocated into 4 groups of equal sizes (group 1: uncategorized stomatitis; group 2: acute traumatic reticuloperitonitis [TRR]; group 3: acute rumen impaction; and group 4: undifferentiated enteritis). Ten apparently healthy buffaloes were randomly selected and considered as a control group. RNA was firstly extracted from the whole blood then a reverse transcription kits was used to convert the RNA to cDNA. Real-time PCR was used to measure the expression of mRNAs of interleukin (IL)-1β, IL-6, IL-10, and tumor necrosis factor (TNF)-α, IgG, and IgA, while glyceraldehyde-3-phosphate dehydrogenase (GAPDH) used as an internal reference. The results of real-time PCR revealed a significant (P ≤ 0.05) upregulation of the gene expression of IL-1β, IL-6, IL-10, and TNF-α in blood of diseased buffaloes compared with those of controls. Animals showing acute TRP had peak values of both IL-6 and IL-10; while those exhibiting enteritis and rumen impaction had the highest values of IL-1β and TNF-α, respectively. The results of qPCR also revealed a significant (P ≤ 0.05) downregulation of both IgG and IgA gene expression in blood of all diseased buffaloes compared with controls. The lowest values of both genes were recorded in buffaloes showing acute TRP. The results herein suggest that the tested genes could have a pivotal role in the pathophysiologic mechanism of the underlying diseases.

The diagnostic accuracy of acute phase proteins and proinflammatory cytokines in sheep with pneumonic pasteurellosis

The goal of this study was to assess the diagnostic accuracy of acute phase proteins and proinflammatory cytokines in sheep with pneumonic pasteurellosis. Blood samples were collected from 56 sheep (36 naturally infected with Pasteurella multocida and 20 healthy controls) belonging to one farm in Eastern region, Saudi Arabia. Serum samples were evaluated for acute phase proteins (Haptoglobin (Hp), serum amyloid A (SAA) and fibrinogen (Fb)), and the proinflammatory cytokines (interleukins (IL-1α, IL-1β, and IL-6), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-ϒ)). Additionally, nasopharyngeal swabs and bronchoalveolar lavages were collected from all animals for bacteriological examinations. Receiver operating characteristic curve was used to assess the diagnostic performance of each parameter. All parameters showed moderate to high degree of positive correlation with case-control status. There was no significant difference in the area under the curve (AUC) among acute phase proteins; however, both Hp and SAA showed better sensitivity and specificity than Fb. The proinflammatory cytokines (IL1-α, IL1-β, and IL6) showed similar and highly accurate diagnostic performance (AUC > 0.9), whereas IFN-ϒ was moderately accurate (AUC = 0.79). In conclusion, this study confirms the value of acute phase proteins and cytokines as diagnostic biomarkers of naturally occuring pneumonic pasteurellosis in sheep.

Bovine Gamma Delta T Cells Contribute to Exacerbated IL-17 Production in Response to Co-Infection with Bovine RSV and Mannheimia haemolytica

Human respiratory syncytial virus (HRSV) is a leading cause of severe lower respiratory tract infection in children under five years of age. IL-17 and Th17 responses are increased in children infected with HRSV and have been implicated in both protective and pathogenic roles during infection. Bovine RSV (BRSV) is genetically closely related to HRSV and is a leading cause of severe respiratory infections in young cattle. While BRSV infection in the calf parallels many aspects of human infection with HRSV, IL-17 and Th17 responses have not been studied in the bovine. Here we demonstrate that calves infected with BRSV express significant levels of IL-17, IL-21 and IL-22; and both CD4 T cells and γδ T cells contribute to this response. In addition to causing significant morbidity from uncomplicated infections, BRSV infection also contributes to the development of bovine respiratory disease complex (BRDC), a leading cause of morbidity in both beef and dairy cattle. BRDC is caused by a primary viral infection, followed by secondary bacterial pneumonia by pathogens such as Mannheimia haemolytica. Here, we demonstrate that in vivo infection with M. haemolytica results in increased expression of IL-17, IL-21 and IL-22. We have also developed an in vitro model of BRDC and show that co-infection of PBMC with BRSV followed by M. haemolytica leads to significantly exacerbated IL-17 production, which is primarily mediated by IL-17-producing γδ T cells. Together, our results demonstrate that calves, like humans, mount a robust IL-17 response during RSV infection; and suggest a previously unrecognized role for IL-17 and γδ T cells in the pathogenesis of BRDC.

Acute phase cytokines, TAC1, and toll-like receptor4 mRNA expression and health associated with group size in veal calves

Chronic stressors are a major health and well-being issue in animals. Immune status of animals under chronic stress is compromised, thus reducing disease resistance and compromising well-being of the animal. The objective of this study was to determine the influence of group size of veal calves on immune status and leukocyte mRNA expression of acute phase cytokines, toll-like receptor 4 (TLR4) and tachykinin 1 (TAC1) over a five-month finishing period. Holstein bull calves (n=168), 44±3 days of age were assigned to one of three treatments; 2, 4, or 8 calves/pen (pen space allowance of 1.82m(2)/calf). Jugular blood samples were collected at the day of grouping and then monthly for 4 months. The differential leukocyte counts were determined and mRNA was extracted from the leukocytes. Reverse transcription-qPCR was used to measure the gene expression of interleukin-1 (IL-1β), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor (TNF-α), TLR4, and TAC1 in leukocytes. Health was evaluated before grouping and monthly for 4 months. On the 1st month after grouping, veal calves that were housed in groups of 8 have greater expression of IL-1β mRNA than calves housed in groups of 4 or 2 (treatment×month, P=0.04). Also at 1 month, groups of 8 had greater TAC1 expression (P<0.05) than calves housed in groups of 4 or 2. However, the expression of IL-1Ra, TNF-α, and TLR4 were not influenced by group size. In the first month of the trial, calves in groups of 8 coughed more (P<0.05) than calves in groups of 2 and coughed more than calves in groups of 4 and 2 during the 2nd month (treatment×month, P=0.03). Calves housed in groups of 8 tended to have greater neutrophil percentage (P=0.09), neutrophil to lymphocyte ratio (P=0.06), and had lower lymphocyte percentage (P=0.06) than those housed in groups of 4 or 2. In conclusion, the number of veal calves in a group, given the same space during the finishing period did not alter IL-1Ra, TNF-α, and TLR4 mRNA expression. However, housing of calves in groups of 8 was associated with greater expression of IL-1β and TAC1 mRNA in peripheral blood leukocytes, and coughing during the first 2 months after grouping. Therefore, housing of veal calves in larger groups may lead to greater susceptibility to respiratory disease and stress.

Neutrophil gelatinase-associated lipocalin (NGAL) and insulin-like growth factor (IGF)-1 association with a Mannheimia haemolytica infection in sheep

This study was aimed at mapping the tissue distribution of some inflammatory parameters associated with a Mannheimia haemolytica (M. haemolytica) infection in sheep. The M. haemolytica was isolated and characterized from the affected lungs of slaughtered animals. Cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-10, insulin-like growth factor (IGF)-1, as well as the acute-phase protein, neutrophil gelatinase-associated lipocalin (NGAL), were identified in the lung tissues, the serum, and the lymph nodes of M. haemolytica infected sheep, by enzyme-linked immunosorbent assay (ELISA). NGAL and IGF-1 pointed to an innate immune response, and epithelial cell repairing, respectively. The adaptive immune response was identified through the type of cytokines present in the affected sheep, as TNF-α represents the pro-inflammatory cytokines, and IL-10 represents the anti-inflammatory cytokines. M. haemolytica isolates were confirmed by polymerase chain reaction (PCR) and DNA sequences. There was a significant difference in the concentrations of NGAL, IGF-1, TNF-α, and IL-10, as observed in the affected sheep when compared to the healthy sheep. This study, for the first time, closely describes the distribution of some key and new inflammatory parameters in the tissue homogenate of affected lungs.

The bovine lung in biomedical research: visually guided bronchoscopy, intrabronchial inoculation and in vivo sampling techniques

There is an ongoing search for alternative animal models in research of respiratory medicine. Depending on the goal of the research, large animals as models of pulmonary disease often resemble the situation of the human lung much better than mice do. Working with large animals also offers the opportunity to sample the same animal repeatedly over a certain course of time, which allows long-term studies without sacrificing the animals.

The aim was to establish in vivo sampling methods for the use in a bovine model of a respiratory Chlamydia psittaci infection. Sampling should be performed at various time points in each animal during the study, and the samples should be suitable to study the host response, as well as the pathogen under experimental conditions.

Bronchoscopy is a valuable diagnostic tool in human and veterinary medicine. It is a safe and minimally invasive procedure. This article describes the intrabronchial inoculation of calves as well as sampling methods for the lower respiratory tract. Videoendoscopic, intrabronchial inoculation leads to very consistent clinical and pathological findings in all inoculated animals and is, therefore, well-suited for use in models of infectious lung disease. The sampling methods described are bronchoalveolar lavage, bronchial brushing and transbronchial lung biopsy. All of these are valuable diagnostic tools in human medicine and could be adapted for experimental purposes to calves aged 6-8 weeks. The samples obtained were suitable for both pathogen detection and characterization of the severity of lung inflammation in the host.

Azithromycin inhibits nuclear factor-κB activation during lung inflammation: an in vivo imaging study

We studied in vivo the potential involvement of nuclear factor-κB (NF-κB) pathway in the molecular mechanism of the anti-inflammatory and immunomodulatory activity of azithromycin in the lung. Mice transiently transfected with the luciferase gene under the control of a NF-κB responsive element were used to assess in vivo NF-κB activation by bioluminescence imaging. Bioluminescence as well as inflammatory cells and concentrations of proinflammatory cytokines in bronchoalveolar lavage fluids, were monitored in an acute model of pulmonary inflammation resulting from intratracheal instillation of lipopolysaccharide. Lipopolysaccharide (LPS) instillation induced a marked increase in lung bioluminescence in mice transiently transfected with the luciferase gene under the control of an NF-κB responsive element, with significant luciferase expression in resident cells such as endothelial and epithelial cells, as assessed by duoplex immunofluorescence staining. Activation of NF-κB and inflammatory cell lung infiltration linearly correlated when different doses of bortezomib were used to inhibit NF-κB activation. Pretreatment with azithromycin significantly decreased lung bioluminescence and airways cell infiltration induced by LPS, also reducing proinflammatory cytokines concentrations in bronchoalveolar lavages and inhibiting NF-κB nuclear translocation. The results obtained using a novel approach to monitor NF-κB activation, provided, for the first time, in vivo evidence that azithromycin treatment results in pulmonary anti-inflammatory activity associated with the inhibition of NF-κB activation in the lung.

Enlightened Mannhemia haemolytica lung inflammation in bovinized mice

Polymorphonuclear cells diapedesis has an important contribution to the induced Mannhemia haemolytica (M. haemolytica) infection lung inflammation and IL-8 is the primary polymorphonuclear chemoattractant. Using a bovine IL-8/luciferase transiently transgenized mouse model, the orchestration among M. haemolytica, IL-8 promoter activation and neutrophilia was followed in real time by in vivo image analysis.

Comparison of pathological changes and viral antigen distribution in tissues of calves with and without preexisting bovine viral diarrhea virus infection following challenge with bovine herpesvirus-1

OBJECTIVE

To compare pathological changes and viral antigen distribution in tissues of calves with and without preexisting subclinical bovine viral diarrhea virus (BVDV) infection following challenge with bovine herpesvirus-1 (BHV-1).

ANIMALS

24 Friesian calves.

PROCEDURES

12 calves were inoculated intranasally with noncytopathic BVDV-1a; 12 days later, 10 of these calves were challenged intranasally with BHV-1 subtype 1. Two calves were euthanized before and 1, 2, 4, 7, or 14 days after BHV-1 inoculation. Another 10 calves were inoculated intranasally with BHV-1 only and euthanized 1, 2, 4, 7, or 14 days later. Two calves were inoculated intranasally with virus-free tissue culture fluid and euthanized as negative controls. Pathological changes and viral antigen distribution in various tissue samples from calves with and without BVDV infection (all of which had been experimentally inoculated with BHV-1) were compared.

RESULTS

Following BHV-1 challenge, calves with preexisting subclinical BVDV infection had earlier development of more severe inflammatory processes and, consequently, more severe tissue lesions (limited to lymphoid tissues and respiratory and digestive tracts) and greater dissemination of BHV-1, compared with calves without preexisting BVDV infection. Moreover, coinfected calves had an intense lymphoid depletion in the Peyer patches of the ileum as well as the persistence of BVDV in target organs and the reappearance of digestive tract changes during disease progression.

CONCLUSIONS AND CLINICAL RELEVANCE

In calves, preexisting infection with BVDV facilitated the establishment of BHV-1 infection, just as the presence of BHV-1 favors BVDV persistence, thereby synergistically potentiating effects of both viruses and increasing the severity of the resultant clinical signs.

Gene expression profiling of bovine bronchial epithelial cells exposed in vitro to bovine herpesvirus 1 and Mannheimia haemolytica

Bovine respiratory disease (BRD) often occurs when active respiratory virus infections (BHV-1, etc.) impair resistance to Mannheimia haemolytica infection in the lower respiratory tract. The interactions that occur when the respiratory epithelium encounters these viral and bacterial pathogens are poorly understood. We used Agilent bovine gene microarray chips containing 44,000 transcripts to elucidate bovine bronchial epithelial cell (BBEC) responses following in vitro exposure to BHV-1 alone, M. haemolytica alone, or both BHV-1 and M. haemolytica. Microarray analysis revealed differential regulation (>2-fold) of 978 transcripts by BHV-1 alone, 2040 transcripts by M. haemolytica alone, and 2189 genes by BHV-1 and M. haemolytica in combination. M. haemolytica treatment produced significantly greater inductions (>10-fold) of several inflammation associated genes, such as CXCL2, IL-6, IL-1α, e-selectin, and IL-8, than to BHV-1 alone. Functional analysis of the microarray data revealed a significant upregulation of genes involved in important biological processes such as inflammation (TNF-α, IL-8, Tlr-2, IL-1, CXCL2, CSF2), vascular functions (VEGF, EDN2) and leukocyte migration (ICAM1, IL-16) during a co-infection with BHV-1 and M. haemolytica compared to either pathogen alone. This study provides evidence to support that lung epithelial cells are a source of mediators that may promote inflammatory changes observed during bovine respiratory disease.

Pathogenic mechanisms implicated in the intravascular coagulation in the lungs of BVDV-infected calves challenged with BHV-1

Resistance to respiratory disease in cattle requires host defense mechanisms that protect against pathogens which have evolved sophisticated strategies to evade them, including an altered function of pulmonary macrophages (MΦs) or the induction of inflammatory responses that cause lung injury and sepsis. The aim of this study was to clarify the mechanisms responsible for vascular changes occurring in the lungs of calves infected with bovine viral diarrhea virus (BVDV) and challenged later with bovine herpesvirus type 1 (BHV-1), evaluating the role of MΦs in the development of pathological lesions in this organ. For this purpose, pulmonary lesions were compared between co-infected calves and healthy animals inoculated only with BHV-1 through immunohistochemical (MAC387, TNFα, IL-1α, iNOS, COX-2 and Factor-VIII) and ultrastructural studies. Both groups of calves presented important vascular alterations produced by fibrin microthrombi and platelet aggregations within the blood vessels. These findings were earlier and more severe in the co-infected group, indicating that the concomitance of BVDV and BHV-1 in the lungs disrupts the pulmonary homeostasis by facilitating the establishment of an inflammatory and procoagulant environment modulated by inflammatory mediators released by pulmonary MΦs. In this regard, the co-infected calves, in spite of presenting a greater number of IMΦs than single-infected group, show a significant decrease in iNOS expression coinciding with the presence of more coagulation lesions. Moreover, animals pre-inoculated with BVDV displayed an alteration in the response of pro-inflammatory cytokines (TNFα and IL-1), which play a key role in activating the immune response, as well as in the local cell-mediated response.

In vivo imaging of transiently transgenized mice with a bovine interleukin 8 (CXCL8) promoter/luciferase reporter construct

One of the most remarkable properties of interleukin 8 (CXCL8/IL-8), a chemokine with known additional functions also in angiogenesis and tissue remodeling, is the variation of its expression levels. In healthy tissues, IL-8 is barely detectable, but it is rapidly induced by several folds in response to proinflammatory cytokines, bacterial or viral products, and cellular stress. Although mouse cells do not bear a clear homologous IL-8 gene, the murine transcriptional apparatus may well be capable of activating or repressing a heterologous IL-8 gene promoter driving a reporter gene. In order to induce a transient transgenic expression, mice were systemically injected with a bovine IL-8 promoter–luciferase construct. Subsequently mice were monitored for luciferase expression in the lung by in vivo bioluminescent image analysis over an extended period of time (up to 60 days). We demonstrate that the bovine IL-8 promoter–luciferase construct is transiently and robustly activated 3–5 hours after LPS and TNF-α instillation into the lung, peaking at 35 days after construct delivery. Bovine IL-8 promoter–luciferase activation correlates with white blood cell and neutrophil infiltration into the lung. This study demonstrates that a small experimental rodent model can be utilized for non-invasively monitoring, through a reporter gene system, the activation of an IL-8 promoter region derived from a larger size animal (bovine). This proof of principle study has the potential to be utilized also for studying primate IL-8 promoter regions.

Dominant expression of interleukin-8 vs interleukin-1β and tumour necrosis factor alpha in lungs of lambs experimentally infected with Mannheimia haemolytica

AIMS

To quantify the number of cells infected with Mannheimia haemolytica and expressing interleukin (IL)-1β, tumour necrosis factor alpha (TNFα) and IL-8 using immunohistochemistry, and to measure the immunoreactivity of cytokines in pulmonary tissue extracts using ELISA, in the lung of lambs experimentally infected with M. haemolytica, and to compare the patterns of expression of cytokines in airways at different times post-infection (p.i.).

METHODS

Twenty 3-month-old lambs of both sexes were randomly assigned to two groups, viz infected (n=15), and uninfected controls (n=5). Each lamb in the infected group was inoculated with 1.5 x 10(9) cfu M. haemolytica in 5 mL sterile nutrient broth, control lambs were inoculated with 5 mL sterile nutrient broth and clinical signs were monitored. Infected and control animals were killed at 1, 3, 5, 7, and 15 days p.i. Histopathology and immunohistochemistry were conducted to determine the number of immunolabelled cells in pneumonic lungs, and study the pattern of expression of IL-1β, TNFα and IL-8 in lung extracts using ELISA.

RESULTS

Lesions in bronchi and bronchioles ranged from epithelial desquamation to bronchiolitis obliterans and necrosis. The alveoli had areas of seroproteinaceous fluid, fibrin and bacterial aggregates that evolved to foci of pyogranulomatous inflammation with clustered inflammatory cells, referred to as 'oat cells'. M. haemolytica antigen was observed in the cytoplasm of inflammatory cells. Labelling of IL-1β, TNFα and IL-8 was observed in bronchial and bronchiolar epithelial cells, alveolar exudate, and in interstitial inflammatory infiltrate, with increased expression on 1 and 3 days p.i. for IL-1β and TNFα, and 1, 3, and 5 days p.i. for IL-8. In lung tissue extracts, peak concentrations of IL-1β (55 (SD 5) ng/mL), TNFα (92 (SD 6) pg/mL) and IL-8 (8 [SD 2] μg/mL) occurred at 3 days p.i.

CONCLUSIONS

The results of this study suggested that the inflammatory cytokines IL-1β, TNFα and IL-8 may play an important role in enhancing the biological response to M. haemolytica, and contribute to the development of lesions in the lung in pulmonary pasteurellosis in sheep. Given that the expression of IL-8 in lung was much greater than that of IL-1β and TNFα, anti-cytokine agents directed at this mediator could be useful in the prevention and treatment of this disease.

Cytokine expression by pulmonary leukocytes from calves challenged with wild-type and leukotoxin-deficient Mannheimia haemolytica

The objective of this study was to assess the role of leukotoxin (LKT) in modulating the pulmonary cytokine response of calves challenged with Mannheimia haemolytica. Thirty-six calves, seronegative to LKT and M. haemolytica whole cell antigen were divided into three groups (I, II and III). Calves in groups I and II were challenged by the intra-bronchial route with 25 mL of phosphate buffered saline (PBS) containing 0.44×10(9) cfu/mL of LKT deficient (lkt(-)) and 25 mL of PBS containing 0.31×10(9) cfu/mL of wild-type (wt) M. haemolytica serotype 1, respectively. Group III calves were challenged intra-bronchially with 25 mL of sterile PBS. Leukocytes were collected from broncho-alveolar lavage fluid (BALF) 4 days before and at 1, 3, and 6 days post-inoculation (p.i.). Expression of the following cytokines in the recovered leukocytes was measured using real-time PCR: interleukin (IL)-1β, -8, -10, -12 (p40) and TNF-α. The amount of TNF-α produced was also quantified by ELISA. Although a statistically significant difference in the expression of these cytokines was not observed between groups challenged with the wt and lkt(-) strains, the wt infected group (II) did exhibit higher mean clinical scores. Overall, there was considerable variation in the composition of the BALF between the groups and by day 7 p.i., both lkt(-)- and wt-challenged calves had seroconverted to M. haemolytica.

Mannheimia haemolytica: bacterial-host interactions in bovine pneumonia

Mannheimia haemolytica serotype S1 is considered the predominant cause of bovine pneumonic pasteurellosis, or shipping fever. Various virulence factors allow M haemolytica to colonize the lungs and establish infection. These virulence factors include leukotoxin (LKT), lipopolysaccharide, adhesins, capsule, outer membrane proteins, and various proteases. The effects of LKT are species specific for ruminants, which stem from its unique interaction with the bovine β2 integrin receptor present on leukocytes. At low concentration, LKT can activate bovine leukocytes to undergo respiratory burst and degranulation and stimulate cytokine release from macrophages and histamine release from mast cells. At higher concentration, LKT induces formation of transmembrane pores and subsequent oncotic cell necrosis. The interaction of LKT with leukocytes is followed by activation of these leukocytes to undergo oxidative burst and release proinflammatory cytokines such as interleukins 1, 6, and 8 and tumor necrosis factor α. Tumor necrosis factor α and other proinflammatory cytokines contribute to the accumulation of leukocytes in the lung. Formation of transmembrane pores and subsequent cytolysis of activated leukocytes possibly cause leakage of products of respiratory burst and other inflammatory mediators into the surrounding pulmonary parenchyma and so give rise to fibrinous and necrotizing lobar pneumonia. The effects of LKT are enhanced by lipopolysaccharide, which is associated with the release of proinflammatory cytokines from the leukocytes, activation of complement and coagulation cascade, and cell cytolysis. Similarly, adhesins, capsule, outer membrane proteins, and proteases assist in pulmonary colonization, evasion of immune response, and establishment of the infection. This review focuses on the roles of these virulence factors in the pathogenesis of shipping fever.

Cytotoxicity and cytokine production by bovine alveolar macrophages challenged with wild type and leukotoxin-deficient Mannheimia haemolytica

Leukotoxin (LKT) is a virulence factor for Mannheimia haemolytica. In this study, bovine alveolar macrophages (BAMs) were challenged with wild type (wt) and LKT deficient (lkt(-)) M. haemolytica at a concentration of 1 bacterium/BAM and the cytokine response was quantified by ELISA and real-time reverse transcriptase-PCR. Significant increases in protein concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-10 were observed in supernatants obtained from BAMs challenged with the lkt(-) strain of M. haemolytica compared with wt challenged BAMs. There were no significant differences in mRNA expression of TNFα, IL-1ß, IL-6, IL-8 or IL-10 between BAMs challenged with the lkt(-) strain of M. haemolytica compared with wt challenged BAMs. BAMs challenged with the wt strain exhibited, on average, 43% more cytotoxicity than lkt(-) challenged BAMs (P<0.01).

Differential expression of interleukin-8 by polymorphonuclear leukocytes of two closely related species, Ovis canadensis and Ovis aries, in response to Mannheimia haemolytica infection

The pneumonic lesions and mortality caused by Mannheimia haemolytica in bighorn sheep (BHS; Ovis canadensis) are more severe than those in the related species, domestic sheep (DS; Ovis aries), under both natural and experimental conditions. Leukotoxin (Lkt) and lipopolysaccharide (LPS) are the most important virulence factors of this organism. One hallmark of pathogenesis of pneumonia is the influx of polymorphonuclear leukocytes (PMNs) into the lungs. Lkt-induced cytolysis of PMNs results in the release of cytotoxic compounds capable of damaging lung tissue. Interleukin-8 (IL-8) is a potent PMN chemoattractant. The objective of the present study was to determine if there is differential expression of IL-8 by the macrophages and PMNs of BHS and DS in response to M. haemolytica. Macrophages and PMNs of BHS and DS were stimulated with heat-killed M. haemolytica or LPS. IL-8 expression by the cells was measured by enzyme-linked immunosorbent assays and real-time reverse transcription-PCR (RT-PCR). The PMNs of BHS expressed severalfold higher levels of IL-8 than those of DS upon stimulation. Lesional lung tissue of M. haemolytica-infected BHS contained significantly higher levels of IL-8 than nonlesional tissue. The bronchoalveolar lavage (BAL) fluid of infected BHS also contained higher levels of IL-8 than that of infected DS. Depletion of IL-8 reduced migration of PMNs toward BAL fluid by approximately 50%, indicating that IL-8 is integral to PMN recruitment to the lung during M. haemolytica infection. Excessive production of IL-8, enhanced recruitment of PMNs, and PMN lysis by Lkt are likely responsible for the severity of the lung lesions in M. haemolytica-infected BHS.

Bovine herpesvirus type 1 infection of bovine bronchial epithelial cells increases neutrophil adhesion and activation

Respiratory infection of cattle with bovine herpesvirus type 1 (BHV-1) predisposes cattle to secondary pneumonia with Mannheimia haemolytica as part of the bovine respiratory disease complex (BRD). One cell type that has received limited investigation for its role in the inflammation that accompanies BRD is the respiratory epithelial cell. In the present study we investigated mechanisms by which BHV-1 infection of respiratory epithelial cells contributes to the recruitment and activation of bovine polymorphonuclear neutrophils (PMNs) in vitro. Primary cultures of bovine bronchial epithelial (BBE) cells were infected with BHV-1 and assessed for cytokine expression by real-time PCR. We found that BHV-1 infection elicits a rapid IL-1, IL-8 and TNF-alpha mRNA response by BBE cells. Bovine PMNs exhibited greater adherence to BHV-1 infected BBE cells than uninfected cells. The increased adherence was significantly reduced by the addition of an anti-IL-1beta antibody or human soluble TNF-alpha receptor (sTNF-alphaR). Pre-incubation of bovine PMNs with conditioned media from BHV-1 infected BBE cells increased PMN migration, which was inhibited by addition of an anti-IL-1beta antibody, sTNF-alphaR, or an IL-8 peptide inhibitor. Conditioned media from BHV-1 infected BBE cells activated bovine PMNs in vitro as demonstrated by PMN shape change, production of reactive oxygen species and degranulation. PMNs also exhibited increased LFA-1 expression and susceptibility to M. haemolytica LKT following incubation with BHV-1 infected BBE cell conditioned media. Our results suggest that BHV-1 infection of BBE cells triggers cytokine expression that contributes to the recruitment and activation of neutrophils, and amplifies the detrimental effects of M. haemolytica LKT.

Immune evasion by pathogens of bovine respiratory disease complex

Bovine respiratory tract disease is a multi-factorial disease complex involving several viruses and bacteria. Viruses that play prominent roles in causing the bovine respiratory disease complex include bovine herpesvirus-1, bovine respiratory syncytial virus, bovine viral diarrhea virus and parinfluenza-3 virus. Bacteria that play prominent roles in this disease complex are Mannheimia haemolytica and Mycoplasma bovis. Other bacteria that infect the bovine respiratory tract of cattle are Histophilus (Haemophilus) somni and Pasteurella multocida. Frequently, severe respiratory tract disease in cattle is associated with concurrent infections of these pathogens. Like other pathogens, the viral and bacterial pathogens of this disease complex have co-evolved with their hosts over millions of years. As much as the hosts have diversified and fine-tuned the components of their immune system, the pathogens have also evolved diverse and sophisticated strategies to evade the host immune responses. These pathogens have developed intricate mechanisms to thwart both the innate and adaptive arms of the immune responses of their hosts. This review presents an overview of the strategies by which the pathogens suppress host immune responses, as well as the strategies by which the pathogens modify themselves or their locations in the host to evade host immune responses. These immune evasion strategies likely contribute to the failure of currently-available vaccines to provide complete protection to cattle against these pathogens.

Cytokine Expression in Paraffin Wax-embedded Tissues from Conventional Calves

The cross-reactivity of antibodies against human tumour necrosis factor (TNF)alpha, interleukin (IL)-1alpha, IL-1beta and porcine IL-6, and the distribution of immunolabelled cells were evaluated on paraffin wax-embedded tissues from five healthy calves. The tissues were fixed in 10% buffered formalin or Bouin's solution and processed for structural studies and immunohistochemical studies by the avidin-biotin-peroxidase technique. Bouin's solution proved to be the more suitable fixative and Tween 20 the most effective antigen unmasking technique for increasing detectable antigenicity. Constitutive expression of TNFalpha, IL-1alpha, IL-1beta and IL-6 by different cell populations, mainly macrophage-like cells, was detected. Lymphoid organs displayed a higher presence of immunolabelled cells than did lung, liver or kidney. TNFalpha and IL-1alpha appeared as the predominant cytokines, especially in the gut-associated lymphoid tissue of the ileum and in the regional mesenteric lymph nodes. The results will facilitate investigation of the role of these cytokine-producing cells in inflammatory disease processes in calves.

The functional state of neutrophils correlates with the severity of renal dysfunction in children with hemolytic uremic syndrome

Hemolytic Uremic Syndrome (HUS) is the main cause of acute renal failure in children. The high percentage of patients who develop long-term sequelae constitutes an important medical concern. The identification of parameters that correlate with the degree of renal failure may be useful to plan the best treatment soon after hospitalization. Here, we investigated the functional state of neutrophils (PMN) from HUS patients on admission, before dialysis and/or transfusion, in relation to the severity of renal impairment reached during the acute period (AP). We found that all PMN activation parameters measured in severe cases of HUS (HUS AP3) were statistically lower comparing to children with mild cases of HUS (HUS AP1). As HUS PMN phenotype and dysfunction is compatible with that of cells undergoing cell death, we also studied spontaneous apoptosis. Not only were HUS PMN not apoptotic, but HUS AP3 PMN showed an increased survival. Almost all phenotypic and functional parameters measured on PMN correlated with severity. Our results revealed a marked deactivation of PMN in severe cases of HUS, and suggest that studying the functional state of PMN could be of prognostic value.

Bovine alveolar macrophage neurokinin-1 and response to substance P

In this study bovine alveolar macrophage neurokinin-1 (NK-1) and the in vitro response to substance P (SP) exposure were investigated. Bovine alveolar macrophage membrane extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotted using anti-NK-1 antiserum demonstrated the presence of an approximately 60kDa band. Phagocytosis of fluorescent bioparticles by SP-exposed macrophages was 39% greater than that of non-exposed macrophages (P=0.0089). Likewise, there was 28% greater TNF production by macrophages following SP exposure compared to non-exposed controls (P=0.116). These results suggest that bovine alveolar macrophages respond to SP at least in part by enhancing phagocytosis and TNF production.

Cytokine response of bovine mammary gland epithelial cells to Escherichia coli, coliform culture filtrate, or lipopolysaccharide

OBJECTIVE

To define the cytokine response of a cultured mammary gland epithelial cell line (ie, Mac-T) when incubated with Escherichia coli or its products.

SAMPLE POPULATION

Mac-T cells and E coli from cows with mastitis.

PROCEDURE

Mac-T cells were incubated with E coli or its products. The cytokine response of Mac-T cells to these treatments was quantified by measuring mRNA content of interleukin (IL)-1alpha, IL-1beta, IL-8, and tumor necrosis factor (TNF)-alpha by use of a quantitative reverse transcriptase-polymerase chain reaction assay. The amount of TNF-alpha secreted was also measured.

RESULTS

Treatment with E coli or its products resulted in significant increases in IL-1alpha, IL-8, and TNF-alpha mRNA content in Mac-T cells. This increase was reversible when culture filtrate was incubated with polymyxin B. The amount of IL-1beta mRNA in Mac-T cells increased only slightly over baseline after treatment with E coli or its products, but this increase was not diminished by incubation of E coli filtrate with polymyxin B.

CONCLUSIONS AND CLINICAL RELEVANCE

Incubation of Mac-T cells with E coli or its products resulted in increased amounts of IL1alpha, IL-8, and TNF-alpha mRNA. Inhibition of this response by incubation of culture filtrate with polymyxin B suggested that lipopolysaccharide was the main bacterial product that stimulated the cytokine response. The small increase in IL-1beta content in Mac-T cells incubated with E coli or its products suggested that this cytokine had a smaller role in the Mac-T cell response to E coli.

Interleukin-8 expression by mammary gland endothelial and epithelial cells following experimental mastitis infection with E. coli

Epithelial and endothelial cells play a pivotal role in initiating and controlling the movement of leukocytes into tissues during inflammation through the production of cytokines and chemokines such as interleukin-8 (IL-8). In situ hybridization with an IL-8 riboprobe was used to determine IL-8 mRNA expression by mammary gland epithelial and endothelial cells in cows with experimental Escherichia coli mastitis. Epithelial cells of the gland, especially surrounding the alveoli, had increased IL-8 mRNA levels at all time points at which tissue samples were collected (8, 12, and 24h) after E. coli challenge. Levels of IL-8 expression in the epithelial cells decreased at 24h post-infection. IL-8 expression by mammary gland endothelial cells was low, but did increase slightly at 24h post-infection. Both epithelial and endothelial cells of the mammary gland can contribute to the production of IL-8 that is typically seen in coliform mastitis.

Incubation of bovine PMNs with conditioned medium from BHV-1 infected peripheral blood mononuclear cells increases their susceptibility to Mannheimia haemolytica leukotoxin

Active infection with bovine herpesvirus-1 (BHV-1) increases the susceptibility of cattle to secondary bacterial pneumonia with Mannheimia (Pasteurella) haemolytica A1. In the present study we found that bovine PMNs incubated with conditioned media from BHV-1 infected peripheral blood mononuclear cells (PBMCs) exhibited increased LFA-1 expression, enhanced LKT binding and increased LKT cytotoxicity. These effects were abrogated when the conditioned medium was pre-incubated with an anti-IL-1beta Mab before being added to the PMNs. These findings suggest that BHV-1 infection, and the resulting release of IL-1beta and perhaps other inflammatory cytokines, can stimulate activation of LFA-1 in bystander bovine PMNs, thus enhancing the binding and biological effects of LKT.

Immunohistochemical Detection of the Expression of Pro-inflammatory Cytokines by Ovine Pulmonary Macrophages

The aim of this study was to determine the expression of three proinflammatory cytokines by pulmonary macrophages of sheep in paraffin wax-embedded tissue. Samples of lung from seven healthy sheep were fixed by immersion in either 10% neutral buffered formalin, acetic formalin, paraformaldehyde-lysine-periodate or Bouin's solution and processed for structural and immunohistochemical studies. The expression of interleukin (IL)-1alpha, IL-6 and tumour necrosis factor (TNF)-alpha by pulmonary intravascular macrophages (PIMs) and alveolar macrophages (AMs) was detected by the avidin-biotin-peroxidase (ABC) technique. Bouin's solution proved to be the most suitable fixative and Tween 20 the most effective pretreatment for increasing permeability. Constitutive expression of IL-1alpha, IL-6 and TNF-alpha by both macrophage populations was detected. The number of PIMs expressing IL-1alpha (the predominant cytokine in ovine lung) was higher than that of AMs, while the expression of IL-6 was greater in AMs. No differences between PIMS and AMs were found in respect of TNF-alpha expression. The evaluation of cytokine expression represents a valuable tool for studying the pathogenesis of disease in the ovine lung.

Potential involvement of gelatinases and their inhibitors in Mannheimia haemolytica pneumonia in cattle

Mannheimia haemolytica infection of the lower respiratory tract of cattle results in a bronchofibrinous pneumonia characterized by massive cellular influx and lung tissue remodeling and scarring. Since altered levels of gelatinases and their inhibitors have been detected in a variety of inflammatory conditions and are associated with tissue remodeling, we examined the presence of gelatinases in lesional and nonlesional lung tissue obtained from calves experimentally infected with M. haemolytica. Lesional tissue had elevated levels of progelatinase A and B and active gelatinase A and B when compared with nonlesional tissue obtained from the same lung lobe. In vitro, M. haemolytica products stimulated production of gelatinase B, but not its activation, by bovine monocytes. Alveolar macrophages showed constitutive production of gelatinase B but no change in response to M. haemolytica products. Bovine neutrophils exposed to M. haemolytica products also released gelatinase B, and there was a significant increase in the activated form of this enzyme. These effects were virtually identical when recombinant O-sialoglycoprotease was used to stimulate these cells. M. haemolytica products also enhanced the expression by bovine monocytes and alveolar macrophages of the tissue inhibitor of metalloproteinase 1. Our results provide evidence that matrix metalloproteinases are activated in lung lesions from cattle with shipping fever and that M. haemolytica virulence products induce production, release, and especially activation of gelatinase B by bovine inflammatory cells in vitro.