Induction of acute phase protein by recombinant human interleukin-6 (IL-6) in calves

Biomarkers of sepsis in pigs, horses and cattle: from acute phase proteins to procalcitonin

Sepsis is a complex clinical syndrome triggered by an inflammatory host response to an infection. It is usually complicated to detect and diagnose, and has severe consequences in human and veterinary health, especially when treatment is not started early. Therefore, efforts to detect sepsis accurately are needed. In addition, its proper diagnosis could reduce the misuse of antibiotics, which is essential fighting against antimicrobial resistance. This case is a particular issue in farm animals, as antibiotics have been traditionally given massively, but now they are becoming increasingly restricted. When sepsis is suspected in animals, the most frequently used biomarkers are acute phase proteins such as C-reactive protein, serum amyloid A and haptoglobin, but their concentrations can increase in other inflammatory conditions. In human patients, the most promising biomarkers to detect sepsis are currently procalcitonin and presepsin, and there is a wide range of other biomarkers under study. However, there is little information on the application of these biomarkers in veterinary species. This review aims to describe the general concepts of sepsis and the current knowledge about the biomarkers of sepsis in pigs, horses, and cattle and to discuss possible advances in the field.

Short communication: Effects of transition milk and milk replacer supplemented with colostrum replacer on growth and health of dairy calves

Transition milk (TM, defined here as the second through fourth milkings after calving) supplies additional fat, protein, and immunoglobulins to the calf compared with milk replacer at industry-suggested feeding rates (∼14% solids). Our objective was to determine whether 9 feedings of TM on d 2 through 4 of life increase the growth rate and overall health of calves. Holstein heifer calves on a commercial farm were randomly assigned to 1 of 3 diets (n = 35/diet): milk replacer (MR; Purina Warm Front BOV MOS Medicated Milk Replacer, St. Louis, MO), TM, or a 50:50 blend of MR and colostrum replacer (MCR; Alta HiCal Colostrum Powder Replacer, the Saskatoon Colostrum Company Ltd., Saskatoon, SK, Canada). The TM was harvested from Holstein cows on the farm, pooled, and pasteurized at 71.7°C for 15 s. Nutrient composition on a dry matter basis of TM was 25.9% fat, 41.8% protein, and 14% solids; MR was 10.3% fat, 27.8% protein, and 14% solids; and MCR was 14.6% fat, 38.6% protein, and 15% solids. All calves received IgG-enriched colostrum replacer for the first 2 feedings after birth. Subsequently, calves were fed 1.9 L of MR, TM, or MCR 3 times per day for 3 d (starting on d 2). After initial diets ended, calves were fed and managed similarly. Body weights (d 1, 7, 14, 21, and 56), blood samples (d 1, 7, 14, and 21), and daily health scores (scale of 0 to 3, with 0 representing normal or healthy and 3 representing severe symptoms or ill) were collected through weaning at 56 d. All except 1 calf achieved successful transfer of passive immunity, with serum IgG values greater than 10.0 mg/mL. From birth through weaning, calves fed TM and MCR gained 3 kg more total body weight than those fed MR (34.3, 34.3, and 31.3 kg, respectively). Increased metabolizable energy (using NRC 2001 recommendations) in TM accounts for 0.68 kg of the increased gain compared with MR. Treatment did not alter health scores for ears, eyes, or feces. Haptoglobin concentrations were lower in TM and MCR than in MR calves (4.63, 3.62, and 7.54 µg/mL, respectively), whereas lipopolysaccharide binding protein concentrations were not different. In conclusion, compared with MR alone, feeding TM or MR with colostrum replacer for 3 d increased growth rate of calves throughout the preweaning period.

Effects of once- versus twice-a-day feeding of pasteurized milk supplemented with yeast-derived feed additives on growth and health in female dairy calves

The objective of this study was to compare the effects of feeding preweaning dairy calves pasteurized milk once or twice a day with or without a combination of yeast-derived products. Holstein heifer calves (n = 48) from The Pennsylvania State University dairy herd were fed 3.8 L of colostrum in 1 feeding and randomly assigned to 1 of 4 treatments (once-a-day milk feeding with or without live yeast culture and mannan-rich fraction and twice-a-day milk feeding with or without live yeast culture and mannan-rich fraction). All calves were fed 6 L of milk daily. Weekly growth measurements and blood samples were taken 3 h after the morning milk feeding for all animals. Growth measurement included body weight, hip width, and withers height. Calf starter refusal was recorded weekly, and a sample was taken to determine dry matter intake. Daily health scores were recorded for each calf using a standard scoring system. Intake, growth measurements, haptoglobin, and health scores data were analyzed using repeated measures analysis with calf included as a random variable. Preweaning average daily gain was 553.4 and 512.1 g/d for calves fed milk once and twice a day, respectively, and we found no difference between treatments. Preweaning calf starter intake was 242.3 and 198.7 g/d for calves fed milk once and twice a day, respectively, and we found no treatment differences. Preweaning calf starter intake was 224.3 and 216.6 g/d for calves fed yeast and without yeast, respectively. Withers height and hip width were similar in calves fed milk either once or twice a day; however, calves fed yeast tended to have greater withers height and hip width than control calves. Haptoglobin concentration as a measure of stress had least squares means of 4.0 and 9.5 ± 3.5 µg/mL for calves fed milk once or twice a day, respectively, and we found no difference among treatments. Scours score and total daily score were similar for calves fed milk once or twice a day. These results suggest that feeding milk once a day can be successfully applied to a calf feeding system and that yeast products may improve structural growth.

The use of infrared thermography as a rapid, quantitative, and noninvasive method for evaluation of inflammation response in different anatomical regions of rats

PURPOSE

Thermographic assessment of temperature distribution within the examined tissues allows a quick, noncontact, noninvasive measurement of their temperature. The aim of the study was to evaluate the usefulness of digital infrared imaging in monitoring experimental inflammation of pleura (PL), lower lip (LL), and left paw (LP) and right paw (RP) of lower limbs in rats.

MATERIALS AND METHODS

The inflammatory reaction was induced by injection of 1% carrageenin solution into pleural cavity, lip, or paws. With the use of digital infrared imaging temperature measurement was conducted at 0 to 72 hours of the inflammatory reaction.

RESULTS

The temperature decrease was observed at the site of injection directly afterwards. Next, it was gradually increasing and it reached the maximum on the third day of the inflammatory reaction. Statistically significant changes were observed after 48-hour period in PL and LL regions, as well as after 72-hour period in LP and RP regions (P < 0.005).

CONCLUSION

It was found that thermographic examination allows for indicating the presence of inflammatory reaction within examined tissues and determining the dynamics of this process. This method could be used as alternative procedure that allows using fewer animals for experiments.

Characterization of the contributions of Hp-MMP 9 to the serum acute phase protein response of lipopolysaccharide challenged calves

Background

Bovine respiratory disease (BRD) is a costly feature of modern cattle production. Early and accurate detection of BRD may prove useful in the successful management of this disease. The primary objective of the study was to define the time course of covalent complexes of neutrophil, haptoglobin (Hp) and matrix metalloproteinase 9 (Hp-MMP 9) in serum after intravenous lipopolysaccharide (LPS) in comparison to traditional markers. Our hypothesis was that serum concentrations of neutrophil Hp-MMP 9 provides information distinct from traditional acute phase protein markers. To characterize the neutrophil responses to lipopolysaccharide (E. coli; O111:B4; 2.5 μg/kg body weight), nine healthy, Jersey calves (65-82 days of age; 74.5 ± 13.1 kg) were challenged and physiologic parameters, peripheral blood cell counts and serum cortisol (C), Hp-MMP 9, Hp, alpha₁-acid glycoprotein (AGP), serum amyloid A (SAA) were obtained starting 24 hours before to 96 hours post-LPS challenge.

Results

Physiologic parameters (temperature, pulse, respiratory rate) and attitude assessed at each time point indicated that LPS challenge resulted in rapid onset of depression, tachypnea, leukopenia, neutropenia and lymphopenia within 1 hour. Serum C concentrations were significantly increased by 1 hour post-LPS. Serum Hp-MMP 9 complexes were detectable in serum by 0.5 hours and peaked at 16 h, serum total Hp remained <10 μg/mL until 8 hours post LPS infusion and were significantly greater than baseline by 12 hours post-LPS infusion. Serum amyloid A concentrations increased significantly by 8 hours post LPS. Serum concentrations of AGP increased significantly by 16 hours post LPS. Serum concentrations of Hp, SAA and AGP remained significantly greater than baseline out to 96 hours post-LPS. The total systemic exposure to traditional makers is significantly greater than from Hp-MMP 9

Conclusion

Using a well described model for acute phase protein responses, the data demonstrate that serum neutrophil Hp-MMP 9 complexes appear sooner and decline more rapidly than other acute phase proteins (APP). Since Hp-MMP9 is stored pre-formed, it provides information specifically addressing the LPS-induced activation of bovine neutrophils. Contributions of Hp-MMP 9 to the serum acute phase protein response may provide useful information, independent of hepatic responses, in diagnosis of acute inflammation.

Concentrations of haptoglobin in bovine plasma determined by ELISA or a colorimetric method based on peroxidase activity

The objective was to compare different procedures for determination of haptoglobin in bovine plasma. Nine Angus steers were vaccinated against Mannheimia haemolytica to stimulate an acute-phase response. Blood samples were collected immediately prior to vaccination (day 0), and on days 1, 3, 5, 7 and 10. Plasma samples were frozen in duplicates at -80 °C. One set of the duplicates was analysed for haptoglobin concentrations using a commercial ELISA kit. A day effect was detected (p < 0.01) because haptoglobin peaked on day 3 and returned to baseline on day 7 relative to vaccination. The second duplicate was analysed using a procedure that measures haptoglobin-haemoglobin complexing by estimating differences in peroxidase activity (CPPA) with results expressed as optical density. Further, based on the ELISA results, the plasma sample with the greatest haptoglobin concentration was also serially diluted into a plasma sample with negligible haptoglobin concentration from the same steer (1:1 through 1:1024 dilution). These dilutions were used within the CPPA method to generate a standard curve and estimate plasma haptoglobin concentrations (CPPA + STD). A linear standard curve was generated (r(2)  = 0.99). A day effect similar to the ELISA method was detected for the CPPA and CPPA + STD methods (p < 0.01). Results obtained from CPPA and ELISA methods were positively correlated (r = 0.97; p < 0.01). The values generated by the CPPA + STD procedure were similar (p = 0.38) compared to the values generated by the ELISA method. In conclusion, assessing concentrations of haptoglobin in bovine plasma using the CPPA and CPPA + STD methods generate highly correlated or similar results, respectively, compared to ELISA. Therefore, the CPPA + STD and CPPA methods can be used as a less expensive alternative to ELISA to determine concentrations or monitor changes in plasma haptoglobin in bovine samples.

Taurine attenuates Streptococcus uberis-induced mastitis in rats by increasing T regulatory cells

Taurine (Tau) is reported to have a key role in the regulation of the innate immune response and thus reduce tissue damage induced by bacterial infection. In this study, the effects of Tau on a rat model of mastitis induced by Streptococcus uberis (S. uberis) and the changes of T regulatory cells (Tregs) were assessed. Starting on gestation day 14 and continuing until parturition, 100 mg/kg of taurine (group TS) or an equal volume of physiological saline (group CS) was administered daily, per os. Seventy-two hours after parturition, rats were infused with approximately 100 cfu of S. uberis into each of two mammary glands. The results showed that the resultant inflammation, evidenced by swelling, secretory epithelial cell degeneration, increased adipose tissue and neutrophil (PMN) infiltration were evident in mammary tissue following injection with S. uberis. Pre-treatment with Tau attenuated these morphologic changes, the expression of interleukin (IL)-2, interferon (INF)-γ mRNA, myeloperoxidase (MPO) activity and N-acetyl-β-D-glucosaminidase (NAGase) in mammary tissue. The percentages of Foxp3+CD25+CD4+/lymphocytes (Tregs) were dramatically increased after the S. uberis challenge. Significant differences (P<0.05) were observed at 24, and 72 h post S. uberis-injection (PI) in CS. Pre-treatment further increased the percentage of Tregs and a significant difference between CS and TS (P<0.05) was apparent at 24 h PI. Our data indicate that in rats, Tau can be used to regulate the immune response following infection by S. uberis and consequently prevent mammary tissue damage by increasing Tregs.

Evaluation of clumping factor A binding region A in a subunit vaccine against Staphylococcus aureus-induced mastitis in mice

The present study evaluated the potential of recombinant binding region A of clumping factor A (rClfA-A) to be an effective component of a vaccine against mastitis induced by Staphylococcus aureus in the mouse. rClfA-A and inactivated S. aureus were each emulsified in Freund's adjuvant, mineral oil adjuvant, and Seppic adjuvant; phosphate-buffered saline was used as a control. Seven groups of 12 mice each were immunized intraperitoneally three times at 2-week intervals. The titers of IgG and subtypes thereof (IgG1 and IgG2a) in the rClfA-A-immunized group were more than 1,000-fold higher than those in the killed-bacteria-immunized group (P < 0.01). Of the three adjuvants used, mineral oil adjuvant induced the highest antibody levels for both antigens (P < 0.001). Furthermore, the anti-rClfA-A antibody capacities for bacterial adhesion and opsonizing phagocytosis were significantly greater in the rClfA-A-immunized group than in the killed-bacteria-immunized group (P < 0.05). Lactating mice immunized with either rClfA-A or inactivated vaccine were challenged with S. aureus via the intramammary route. The numbers of bacteria recovered from the murine mammary glands 24 h after inoculation were significantly lower in the rClfA-A group than in the killed-bacteria-immunized group (P < 0.001). Histologic examination of the mammary glands showed that rClfA-A immunization effectively preserved tissue integrity. Thus, rClfA-A emulsified in an oil adjuvant provides strong immune protection against S. aureus-induced mastitis in the mouse.

Serum concentrations of C-reactive protein, serum amyloid A, and haptoglobin in pigs inoculated with African swine fever or classical swine fever viruses

OBJECTIVE

To determine serum concentrations of the selected acute-phase proteins (APPs) haptoglobin, serum amyloid A (SAA), and C-reactive protein (CRP) in pigs experimentally inoculated with classical swine fever (CSF) and African swine fever (ASF) viruses.

ANIMALS

8 crossbred (Large White x Landrace) 10-week-old pigs.

PROCEDURES

Pigs were allocated to 2 groups (4 pigs/group). One group was inoculated with the CSF virus Alfort 187 strain, whereas the other groupwas inoculated with the ASF virus Spain 70 isolate. Blood samples were collected at various time points. At the end of the study, pigs were euthanized and a complete necropsy was performed, including histologic and immunohistochemical analyses.

RESULTS

Serum concentrations of APPs increased in pigs inoculated with CSF and ASF viruses, which suggested an acute-phase response in the course of both diseases. The most noticeable increase in concentration was recorded for SAA in both groups (up to a 300-fold increase for CSF virus and an approx 40-fold increase for ASF virus), followed by CRP and then haptoglobin, which each had only 3- to 4-fold increases.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum concentrations of APPs increased significantly in pigs inoculated with CSF and ASF viruses. However, differences were evident in serum concentrations of the proteins evaluated in this study.

Protective effect of CpG-DNA against mastitis induced by Staphylococcus aureus infection in a rat model

A mastitis model in rats, induced by Staphylococcus aureus infection, was established and the protective effect of CpG-DNA on this model was determined. A S. aureus suspension containing 2 x 10(3) CFU.mL(-1) (SL group), 2 x 10(5) CFU.mL(-1) (SH group) or 100 microL PBS (CON group) was inoculated into the mammary glands of rats 72 h after parturition. The rats were euthanized at 24 h post-infection. The histopathologic changes in mammary tissue from SL were mild, whereas the structural changes of the mammary gland from SH were severe and polymorphonuclear leukocytes (PMNs) accumulated in mammary alveoli. Interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and N-acetyl-beta-d-Glucosaminidase (NAGase) in mammary tissue from SH were significantly increased, however, those from SL were not significantly changed. Therefore, 2 x 10(5) CFU.mL(-1) was selected to test the potential protective effect of CpG-DNA on mammary glands. CpG-DNA (200 microg) or PBS (100 microL) controls were intramuscularly injected right after parturition of rats. At 72 h post-partum, 2 x 10(5) CFU.mL(-1)of S. aureus (100 microL) were inoculated into the mammary gland of all rats and at pre-infection (0 h), 8, 16, 24, 48 and 72 h after inoculation six rats were euthanatized. CpG-DNA induced more rapid migration of PMNs from blood to mammary tissue at the initial stage of infection, stimulated the secretion of IL-6 and TNF-alpha at different time points, reduced viable S. aureus in mammary tissue and decreased the activity of NAGase. CpG-DNA also promoted the expression of its specific receptor TLR-9 mRNA in mammary tissue. In conclusion, CpG-DNA protected against S. aureus mastitis in a rat model.

ITIH4 (inter-alpha-trypsin inhibitor heavy chain 4) is a new acute-phase protein isolated from cattle during experimental infection

We have isolated from calf serum a protein with an apparent M(r) of 120,000. The protein was detected by using antibodies against major acute-phase protein in pigs with acute inflammation. The amino acid sequence of an internal fragment revealed that this protein is the bovine counterpart of ITIH4, the heavy chain 4 of the inter-alpha-trypsin inhibitor family. The response of this protein in the sera was determined for animals during experimental bacterial and viral infections. In the bacterial model, animals were inoculated with a mixture of Actinomyces pyogenes, Fusobacterium necrophorum, and Peptostreptococcus indolicus to induce an acute-phase reaction. All animals developed moderate to severe clinical mastitis and exhibited remarkable increases in ITIH4 concentration in serum (from 3 to 12 times the initial values, peaking at 48 to 72 h after infection) that correlated with the severity of the disease. Animals with experimental infections with bovine respiratory syncytial virus (BRSV) also showed increases in ITIH4 concentration (from two- to fivefold), which peaked at around 7 to 8 days after inoculation. Generally, no response was seen after a second infection of the same animals with the virus. Because of the significant induction of the protein in the animals in the mastitis and BRSV infection models, we can conclude that ITIH4 is a new positive acute-phase protein in cattle.

The protozoan parasite, Theileria annulata, induces a distinct acute phase protein response in cattle that is associated with pathology

Acute phase proteins (APP) are synthesised in the liver in response to the systemic presence of high levels of pro-inflammatory cytokines. Bacteria are considered to be strong inducers of APP whereas viruses are weak or non-inducers of APP. Very few reports have been published on APP induction by parasites. Here, we report that the tick-borne protozoan parasite of cattle, Theileria annulata, induced an atypical acute phase response in cattle. Following experimental infection, serum amyloid A (SAA) appeared first, followed by a rise in alpha(1) acid glycoprotein (alpha(1)AGP) in all animals, whereas haptoglobin, which is a major APP in cattle, only appeared in some of the animals, and generally at a low level. All three APP only became elevated around or after the appearance of schizonts in draining lymph nodes and after the first observed temperature rise. Increased alpha(1)AGP levels coincided with the appearance of piroplasms. The production of SAA and alpha(1)AGP correlated strongly with each other, and also with some clinical measures of disease severity including the time to fever, development of leucopaenia, parasitaemia and mortality. These results are consistent with the hypothesis that T. annulata causes severe pathology in susceptible cattle by inducing high levels of pro-inflammatory cytokines.

Genomic structure, organisation, and promoter analysis of the bovine (Bos taurus) Mx1 gene

Some MX proteins are known to confer a specific resistance against a panel of single-stranded RNA viruses. Many diseases due to such viruses are known to affect cattle worldwide, raising the possibility that the identification of an antiviral isoform of a bovine MX protein would allow the implementation of genetic selection programs aimed at improving innate resistance of cattle. With this potential application in mind, the present study was designed to isolate the bovine Mx1 gene including its promoter region and to investigate its genomic organisation and promoter reactivity. The bovine Mx1 gene is made up of 15 exons. All exon-intron boundaries conformed to the consensus sequences. A PCR product that contained a approximately 1-kb, 5'-flanking region upstream from the putative transcription start site was sequenced. Unexpectedly, this DNA region did not contain TATA or CCAAT motifs. A computer scan of the region disclosed a series of putative binding sites for known cytokines and transcription factors. There was a GAAAN(1-2)GAAA(C/G) motif, typical of an interferon-sensitive responsive element, between -118 and -107 from the putative transcription start site. There were also a NF-kappaB, two interleukin-6 binding sites, two Sp1 sites and five GC-rich boxes. The region also contained 12 stretches of the GAAA type, as described in all IFN-inducible genes. Bovine Mx1 expression was assessed by Northern blotting and immunofluorescence in the Madin Darby bovine kidney cells (MDBK) cell line treated with several stimuli. In conclusion, the bovine Mx1 gene and promoter region share the major structural and functional characteristics displayed by their homologs described in the rainbow trout, chicken, mouse and man.

Transient detection of proinflammatory cytokines in sera of colostrum-fed newborn calves

To obtain basic information on the state of proinflammatory cytokines in newborn calves, we determined the kinetics of 5 cytokines (IL-1beta, IL-6, TNF-alpha, IFN-gamma and IL-1 receptor antagonist) in sera of newborns during the first 4 weeks of life. At birth, none of the 5 cytokines were detected in almost all serum samples, but the cytokines became detectable within 12 hr after being fed colostram. The mean concentrations of the cytokines reached peak levels by 24 hr and then gradually decreased and became undetectable by 4 weeks after birth. Cytokine mRNA expressions in peripheral blood mononuclear cells of newborns were observed without reference to the cytokine concentrations in sera. Serum cytokines detected in newborn calves are probably colostral origin.

Cytokine profile of a Holstein calf with bovine leukocyte adhesion deficiency during the acute-phase inflammatory response

Changes in interleukin (IL)-1beta, IL-6 and IL-8 in serum, and their mRNA expression on neutrophils from a 4.6-month old Holstein young calf with bovine leukocyte adhesion deficiency (BLAD) during the acute phase were evaluated. IL-1beta concentrations in the serum of the calf with BLAD at age 143-162 days ranged from 8.7 to 16.6 ng/ml, whereas the values were less than 2.7 ng/ml in control calves. Serum IL-6 (0.04 ng/ml) was only detected on the 1st day when the animal was diagnosed with the BLAD. IL-1beta and IL-8 mRNA expression on neutrophils from the affected calf appeared to be similar to those of controls. Serum cytokine levels and their mRNA expression on neutrophils from the calf with BLAD appeared to be little affected by the deficient expression of beta(2)-integrin on leukocytes, and are considered to be modulated by the inflammatory stimuli.

Regulation of haptoglobin secretion by recombinant bovine cytokines in primary cultured bovine hepatocytes

We examined the regulation of haptoglobin (Hp) secretion in primary cultured bovine hepatocytes using recombinant bovine (rb) proinflammatory cytokines. The concentrations of Hp in the supernatant of cultured hepatocytes after incubation with rb interleukin (IL)-6, rb tumor necrosis factor (TNF)-alpha, rbIL-1 beta or rbIFN-gamma alone or with combinations of two of these cytokines were measured by ELISA. The rbIL-6, rbTNF-alpha and rbIL-1 beta increased Hp synthesis, but rbIFN-gamma did not, and rbIL-6 was the most effective Hp inducer among these cytokines. The Hp secretion was accelerated synergistically by combined treatment with rbIL-6 and rbTNF-alpha, whereas it remained unchanged with a combination of rbIL-6 and rbIL-1 beta. In contrast, the combination of rbIL-6 and rbIFN-gamma downregulated Hp secretion. In conclusion, IL-6 is the principal cytokine in Hp secretion in bovine hepatocytes in vitro, and its activity may be regulated by other cytokines.

Acute phase response in naturally occurring coliform mastitis

Changes in the activities of serum cytokines and in acute phase response were observed in dairy cows with naturally occurring coliform mastitis. Seven cows with severe mastitis showed systemic and mammary inflammatory response throughout the observation period, and 11 cows with mild mastitis recovered and were able to be milked within 3 days of onset of mastitis. Serum interleukin (IL)-I and tumor necrosis factor (TNF) activities were higher in the severe group than in the mild group at the first appearance of symptoms. Elevated IL-1 activity was evident in the severe group throughout the observation period. Serum alpha-1-acidglycoprotein (alpha1AG) concentration began to rise with the beginning of mastitis in the severe group, and peaked at 9 days. Serum haptoglobin (Hp) concentrations peaked at 3 days, and decreased gradually after 3 days in the severe group. These results showed that there are dynamic changes in serum IL-1 activity and in serum alpha1AG and Hp concentrations in cows with severe coliform mastitis.

Concentrations of IL-6 in serum and whey from healthy and mastitic cows

Inflammatory cytokines, such as interleukin (IL)-6, have been shown to reflect clinical signs in certain conditions in diseased animals. In this study, we quantified the IL-6 concentrations in the serum and milk whey from 94 dairy cows with acute clinical mastitis and 55 healthy lactating cows. The IL-6 concentrations in serum from mastitic cows were significantly higher on the first day of illness compared to those of normal cows. Higher concentrations of IL-6 were also detected in the whey from mastitic cows, whereas low concentrations of IL-6 were detected in both serum and whey samples from normal cows. IL-6 concentrations in the serum taken at the onset of illness from cows that later required euthanasia were significantly higher than those in samples from cows that later recovered. These results suggest that serum IL-6 concentrations may be of prognostic value in identifying cows with severe mastitis.

Serum haptoglobin: an objective indicator of experimentally-induced Salmonella infection in calves

Experimental models of Salmonella -induced gastroenteritis have previously relied on crude subjective clinical markers of infection to assess disease severity. The aim of this study was to investigate the possibility that changes in serum levels of the acute phase protein, haptoglobin, may be used as an objective, quantitative measurement of infection. Eight 3- to 4-week-old animals were challenged with a mixture of three Salmonella serotypes containing 6 x 10(10)bacteria and compared with five animals given a placebo preparation. Animals were monitored and characteristic clinical symptoms of infection; diarrhoeal scores, morbidity scores and rectal temperature, were recorded. Serum samples, from both animal groups, taken prior to challenge and again on days 1, 3, and 5 post-challenge, were analysed for haptoglobin levels using a direct serum binding assay. Prior to challenge, all 13 animals had normal levels of haptoglobin in their serum. By day 3 post-challenge six of eight animals challenged with Salmonella had abnormal serum haptoglobin levels (median level = 212 microg ml(-1)), while haptoglobin levels remained normal in placebo-challenged animals (median level = 0 microg ml(-1)). The change in haptoglobin levels during the 5-day observation period was statistically significant in the Salmonella -challenged animals (P = 0.0003, H = 16.477). Serum haptoglobin levels showed a statistical correlation with clinical measures of disease severity; diarrhoeal scores (P = 0.0015, H =8. 988), morbidity scores (P = 0.0004, H = 15.711) and rectal temperature (P = 0.0001, Z = 4.304). Thus, serum haptoglobin levels closely reflect the clinical symptoms of infection and are therefore a useful marker of infection severity in salmonellosis in calves.

Biological functions of recombinant bovine interleukin 6 expressed in a baculovirus system

The cDNA encoding bovine interleukin 6 (IL-6) was obtained from messenger RNA extracted from lipopolysaccharide-stimulated bovine Kupffer cells by the reverse transcription polymerase chain reaction (RT/PCR), and cloned into the baculovirus vector pVL 1392. Insect cells (Sf21AE derived from Spodoptera frugiperda) infected with the recombinant baculovirus secreted a large amount of 23.7 kD protein into the culture medium. This protein was capable of causing increased haptoglobin production and decreased albumin production in primary cultured bovine hepatocytes. The swine and human IL-6s were also able to decrease albumin production in bovine hepatocytes. This recombinant IL-6 did not stimulate the proliferation of 7TD1 cells (a murine IL-6-dependent cell line), whereas the recombinant swine IL-6 which was expressed in the same baculovirus system, and recombinant human IL-6 derived from Escherichia coli were each capable of stimulating proliferation of 7TD1 cells, respectively. This suggests a species restriction between bovine IL-6 and murine IL-6 dependent cell lines.

The release of tumor necrosis factor-alpha, interleukin-1, interleukin-6 and prostaglandin E2 in bovine Kupffer cells stimulated with bacterial lipopolysaccharide

Kupffer cells, in response to gut-derived bacteria, viruses and endogenous endotoxins, are thought to be a major source of proinflammatory cytokines and other mediators. In the present study, we investigated the mode of tumor necrosis factor alpha (TNF-alpha) and interleukin-1 (IL-1), interleukin-6 (IL-6) and prostaglandin E2 (PGE2) production by bovine Kupffer cells in response to LPS in vitro. By semi-quantitative reverse transcription-polymerase chain reaction, both TNF-alpha and IL-1beta mRNAs were expressed between 3 and 12 h after stimulation with 1 microg/ml of LPS. The IL-1alpha transcript also increased at 3 h, and then disappeared at 6 h. Although IL-6 mRNA was slightly expressed without stimulation, it increased and reached a peak after 6 h, and then decreased to normal levels by 24 h. The secretion of TNF-alpha and IL-1 was detected after 3 h and increased until 12 and 24 h, respectively, as detected by bioassay. IL-6 was secreted at a low level without stimulation, peaked 6 h after stimulation and remained elevated until 24 h. The secretion of prostaglandin E2 continued to increase for 24 h. These results suggest that several inflammatory cytokines released from bovine Kupffer cells are regulated in different modes.

Serum levels of interleukin-6, alpha1-acid glycoprotein, and corticosterone in two-week-old chickens inoculated with Escherichia coli lipopolysaccharide

The concentration of interleukin-6 (IL-6), alpha1-acid glycoprotein (alpha1-AG), and corticosterone (CORT) was investigated chronologically (0 h to 14 d) in the sera of 2-wk-old specific-pathogen-free chicks inoculated with Escherichia coli lipopolysaccharide (LPS). In the LPS group the IL-6 level was elevated from 1 h to 2 d and was the highest at 3 h. From 4 to 14 d the IL-6 level was low in the LPS group. In the PBS group, IL-6 was not detected except a mild increase from 1 h to 6 h. In the LPS group, the alpha1-AG level increased from 6 h to 4 d, and the peak was 2 d. In the PBS group the alpha1-AG level was always low. The CORT level in the LPS group was higher than that of PBS group at 1 h. This study suggests that E. coli LPS may elevate serum IL-6 and CORT, and that IL-6 and CORT may increase the alpha1-AG level in the chicks.

Elevated levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) activities in the sera and milk of cows with naturally occurring coliform mastitis

The presence of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) activities was determined in milk and serum of cows with naturally occurring coliform mastitis (CFM). TNF-alpha was detected in the sera from 26 of 32 cows with CFM. TNF-alpha levels were higher in the sera than in the milk. IL-6 was high in the sera of surviving CFM animals, but was low in animals that died and in healthy controls. Furthermore, the mean level of IL-6 was 20-fold higher in the milk than in the sera of mastitic cows. The level of IL-6 in the serum was correlated to that in the milk in individual animals. The presence of IL-6 and TNF-alpha in the sera appears to relate to severe clinical condition of CFM, in the milk whereas they may play a role in generating inflammation of the mammary gland.

Acute phase proteins and transformed cells

Acute phase proteins (APP) are plasma proteins whose concentration and glycosylation alters in response to tissue injury, inflammation, or tumor growth. Significant interspecies and sex differences in APP response exist. APP are produced mainly by hepatocytes, and their synthesis and glycosylation are controlled by a network consisting of cytokines, their soluble receptors, and glucocorticoids. The major cytokines involved in these processes belong to a group of interleukin-6-type cytokines that act through the hematopoietin receptor complex on hepatocytes and JAK-STAT signal transduction pathway. Transformed cells (hepatoma) display significant differences in synthesis of APP, cytokine responsiveness, expression of cytokine-receptor subunits and signal-transduction machinery. The most striking variability relates to the glycosylation alterations induced by cytokines. However, transformed cells (hepatoma) form a basic model for studying and understanding mechanisms controlling the synthesis and glycosylation of APP. Furthermore, APP may be secreted by transformed (tumor) cells of various origins and may display a growth factor-like function in certain cancer types.

Primary bovine hepatocytes in the study of cytokine induced acute-phase protein secretion in vitro

To investigate the utility of primary cultures of bovine hepatocytes for compartmentalized acute phase protein studies the secretion of serum amyloid-A (SAA) and haptoglobin (Hp) was measured after stimulation by pro-inflammatory cytokines (recombinant human IL-6 (rhIL-6) and recombinant human tumour necrosis factor-alpha (rhTNF-alpha)). During the incubation period of the experiment, the SAA and Hp secretion into the culture medium increased (P < 0.05). SAA concentrations showed an additional increase following treatment with each of the cytokines (P < 0.01). Hp concentrations remained unchanged, whereas incubation with a combination of both resulted in a significant increase of the medium concentration of both SAA (P < 0.01) and Hp (P < 0.05). From these findings it is concluded that primary bovine hepatocytes can be used for in vitro studies on acute-phase protein secretion.

Characterisation of bovine lipopolysaccharide binding protein and the in vivo acute phase response to Pasteurella haemolytica Type A

Lipopolysaccharide binding protein (LBP) is a liver-derived acute phase protein which is implicated in modulating the host responses to lipopolysaccharide (LPS) from Gram-negative bacteria. LBP interacts with circulatory LPS to form complexes which bind to the CD14 receptor or cells of the monocytic lineage and neutrophils resulting in their activation. This causes the release of mediators and cytokines which are responsible for initiating the acute phase response. LBP-like activity has now been identified in bovine serum and in this study LBP has been purified from acute phase bovine serum using ion exchange chromatography. On sodium dodecyl sulphate polyacrylamide electrophoresis, bovine LBP demonstrated a single band with a molecular mass of 58 kDa. Bovine LBP enhanced the binding of LPS to human monocytes while enzymatic removal of the CD14 receptor abrogated this interaction. Furthermore, bovine LBP increased the sensitivity of monocytes to LPS by at least 100-fold. Depletion of LBP by means of antibodies to bovine LBP inhibited the serum mediated LPS binding to monocytes. Antibodies to rabbit LBP or recombinant human LBP did not cross-react with bovine LBP. Studies on the kinetics of LBP activity in calves during the acute phase response demonstrated a four-fold increase in the serum concentration 36 h after a single intratracheal inoculation of Pasteurella haemolytica A1. The findings of this study indicate that cattle possess a LPS detection mechanism comparable to that described in man and experimental animals in which LBP forms complexes in serum with circulatory LPS enhancing the signal to the immune system to mount a host response. The isolation of LBP will allow further investigations into LBP-mediated responses to LPS in cattle.

Interleukin-6 secretion by bacterial lipopolysaccharide-stimulated bovine alveolar macrophages in vitro

Interleukin-6 (IL-6) is a pluripotent cytokine that may play a role in pulmonary defense against bacterial pathogens. We have quantitated the response of bovine alveolar macrophages (bAM) to bacterial lipopolysaccharide (LPS; E. coli 055: B5) in vitro using the IL-6 sensitive 7TD1 cell line. Bacteria LPS in the absence of serum induced IL-6 secretion from bAM (1 x 10(6) ml-1) over a range of LPS concentrations from 10 ng ml-1 to 10 micrograms ml-1. This resulted in IL-6 levels ranging from approximately 5 to over 200 U ml-1.IL-6 secretion by from approximately 5 to over 200 U ml-1.IL-6 secretion by LPS-stimulated bAM was increased by 24 h poststimulation, and continued to increase up to 72 h after stimulation. Fetal bovine serum (FBS, 1% vol/vol; 320 micrograms ml-1) enhanced IL-6 secretion from macrophages in the presence of LPS by approximately 10-fold compared with LPS alone. A bovine serum fraction (1 microgram ml-1 protein) prepared using ion-exchange chromatography also markedly enhanced IL-6 secretion versus LPS alone. The stimulatory effect of IL-6-like activity in the bAM supernatants was neutralized by an anti-human IL-6 polyclonal antibody. Northern blot analysis revealed increased IL-6 mRNA at 2 h poststimulation with LPS + FBS, peak levels at 4 h, and levels were decreased by 6 h poststimulation. Results suggest that IL-6 is secreted by bovine alveolar macrophages, and that bacterial LPS and serum components synergize to produce this response.

Development of a sensitive and specific time resolved fluorimetric immunoassay for the bovine acute phase protein haptoglobin (Hp)

Haptoglobin (Hp) is recognised as a major acute phase protein in the bovidae and its presence in serum is used as an indicator of inflammation. A mouse monoclonal antibody (1D9) specific for bovine Hp was labelled with a lanthanide (Eu) chelate and used to develop a competitive immunoassay. This competitive immunoassay allowed direct measurement of Hp in serum and was validated for intra- and interassay coefficients of variation (below 8%). Cross-reactivity with other serum proteins was measured (less than 0.1%) and limits of detection for Hp in serum were established for adult male (0.344 microgram/ml) and adult female cattle (1.589 micrograms/ml). The immunoassay was compared with an established haptoglobin-haemoglobin binding assay.