Standardization of diagnostic assays for animal acute phase proteins

Pig Acute Phase Proteins as Non-Antibody Systemic Biomarkers of Intracellular Infections

As an alternative to traditional serological markers, that is, antibodies, for serum-based specific diagnosis of infections, circulating non-antibody markers may be used to monitor active disease. Acute phase proteins (APPs) are a prominent class of such markers widely used for diagnosing ongoing inflammation and infection. In this chapter, basic theoretical and practical considerations on developing APP assays and using APPs as markers of ongoing infection are presented with a specific focus on intracellular infections in pigs. Examples on APP-based monitoring of infection in pigs with viruses such as porcine respiratory and reproductive syndrome virus (PRRSV), porcine endemic diarrhea virus (PEDV), and influenza A virus (IAV), as well as intracellular bacteria (Lawsonia intracellularis) and the protozoan intracellular parasites Toxoplasma gondii and Cryptosporidium parvum are presented, with an emphasis on major pig APPs C-reactive protein (CRP), haptoglobin, serum amyloid A (SAA), and pig major acute phase protein (pig-MAP). The performance of these APPs as biomarkers in a range of experimental infection studies in pigs is described as examples on their use for estimating the severity of infection, vaccine efficacy, herd health characterization, and differential diagnosis.

Proteomic methods for the study of porcine acute phase proteins - anything new to detect?

Acute phase proteins (APPs) reflect the health status of individuals and are important tools in diagnostics, as their altered levels are a sign of disturbed homeostasis. While, in most cases, quantitation of known serum APPs is routinely performed by immunoassays, proteomics is helpful in discovery of new biomarker candidates, especially in samples other than body fluids. Besides putting APP regulation into an overall context of differentially abundant proteins, this approach can detect further details or outright new features in protein structure or specific modifications, and help understand better their function. Thus, it can show up ways to make present diagnostic assays more sensitive and/or specific, or correlate regulations of disease-specific proteins. The APP repertoire is dependent on the species. The pig is both, an important farm animal and a model animal for human diseases, due to similarities in physiology. Besides reviewing existing literature, yet unpublished examples for two-dimensional electrophoresis in connection with pig APPs highlight some of the benefits of proteomics. Of further help would be the emerging targeted proteomics, offering the possibility to determine particular isoforms or proteoforms, without the need of specific antibodies, but this method is presently scarcely used in veterinary medicine.

Effect of direct therapeutic ultrasound exposure of ovaries on histopathology, inflammatory response, and oxidative stress in dogs

BACKGROUND

This research was designed to evaluate the effects of therapeutic ultrasound waves on ovarian germinal tissue and inflammatory cytokines (interleukin-6 (IL-6), IL1β, tumor necrosis factor-α (TNF-α)), acute phase proteins (serum amyloid A (SAA), C reactive protein (CRP)) and oxidative stress (total antioxidant capacity (TAC), and malondialdehyde (MDA)) in dogs. Twenty-six clinically healthy adult mix-breed female dogs were aligned into three groups. Laparotomy was performed in control (n = 6) and treatment (T5, n = 10; T10, n = 10) groups. The ultrasonic exposure of ovaries in treatment groups was performed during laparotomy by round motions of the therapeutic ultrasonic transducer on both ovaries (1 MHz frequency, 1.5 W⁄cm2) for 5 min in the T5 group and for 10 min in the T10 group. Blood samples were collected from the jugular vein into a plain glass tube on days 0 (before laparotomy), 3, 6, and 9 after surgery. All control and treatment groups' dogs were ovariectomized for histological evaluation on day 60 after laparotomy or laparotomy + ultrasound exposure.

RESULTS

Direct exposure of ovaries with therapeutic ultrasound waves induced inflammation and oxidative stress comparison with the control group. Histopathological evaluation of treated ovaries with ultrasound waves indicated a decreased number of primordial follicles (ovarian reserve) and oocyte preservation scores compared with ovaries in the control group.

CONCLUSIONS

These changes may cause subfertility in the long term. It seems that inflammatory response and oxidative stress are factors in the permanent damage of ovarian tissue.

Validation of new automated turbidimetric immunoassays for the measurement of haptoglobin and inter-α-trypsin inhibitor heavy chain H4 specific for the bovine species

BACKGROUND

Good strategical programs are required for the early detection of disease even in the absence of evident clinical signs, which is crucial in satisfying animal welfare. Haptoglobin (Hp) and inter-α-trypsin inhibitor heavy chain H4 (ITIH4) are acute phase proteins and good biomarkers of early inflammation in cattle, with plasma levels that significantly increase after injury or infection.

OBJECTIVES

We aimed to develop and validate two new immunoturbidimetric methods for Hp and ITIH4.

METHODS

Species-specific antibodies were obtained and used to develop the immunoassays. For the Hp assay, antibodies were fixed to latex microparticles to enhance detection. The immunoassays were set up in an automated analyzer to carry out validation studies. Reference intervals were calculated using Reference Value Advisor.

RESULTS

The Hp immunoturbidimetric method had a linear analytical range up to 0.40 mg/mL. The limit of detection (LoD) was 0.005 mg/mL, and the limit of quantification (LoQ) was 0.007 mg/mL. Total imprecision was less than 7%. Comparison with ELISA and single radial immunodiffusion (SRID) showed good correlation, whereas the comparison with the colorimetric method showed constant and proportional differences. The ITIH4 immunoassay showed linearity up to 5 mg/mL, and the LoD was 0.002 mg/mL. Total imprecision was less than 6%. Method comparison showed a good correlation with single radial immunodiffusion, both methods being equivalent. Bilirubin, triglycerides, and hemoglobin presented no interference in any of the assays. Reference intervals were 0.007-0.017 mg/mL for Hp and 0.2-0.7 mg/mL for ITIH4 in dairy cows 10 days before parturition.

CONCLUSIONS

Immunoturbidimetric methods developed for Hp and ITIH4 can measure basal and increased levels of these proteins, showing adequate precision, accuracy, and robustness.

Biomarkers of Intestinal Injury in Colic

Biomarkers are typically proteins, enzymes, or other molecular changes that are elevated or decreased in body fluids during the course of inflammation or disease. Biomarkers pose an extremely attractive tool for establishing diagnoses and prognoses of equine gastrointestinal colic, one of the most prevalent causes of morbidity and mortality in horses. This topic has received increasing attention because early diagnosis of some forms of severe colic, such as intestinal ischemia, would create opportunities for rapid interventions that would likely improve case outcomes. This review explores biomarkers currently used in equine medicine for colic, including acute phase proteins, proinflammatory cytokines, markers of endotoxemia, and tissue injury metabolites. To date, no single biomarker has been identified that is perfectly sensitive and specific for intestinal ischemia; however, L-lactate has been proven to be a very functional and highly utilized diagnostic tool. However, further exploration of other biomarkers discussed in this review may provide the key to accelerated identification, intervention, and better outcomes for horses suffering from severe colic.

Method validation, reference values, and characterization of acute-phase protein responses to experimentally induced inflammation and bluetongue virus infection in the Iberian ibex

BACKGROUND

Acute phase protein (APP) concentrations can change due to inflammation and be used to monitor disease in the Iberian ibex (Capra pyrenaica).

OBJECTIVES

This study aimed to validate Haptoglobin (Hp) and serum amyloid A (SAA) analytes, establish reference values, and characterize Hp and SAA responses in the Iberian ibex after experimentally induced inflammation and experimental bluetongue virus (BTV) infection.

METHODS

Sera from 40 free-ranging box-trapped ibexes were used to establish Hp and SAA reference values. Six healthy ibexes were subcutaneously injected with 5 mL of turpentine, then, blood samples were taken, and clinical evaluations were performed on days 0, 1, 2, 3, 4, 7, and 14 postinjection. Another seven ibexes were challenged with BTV. Serum Hp and SAA concentrations were quantified using commercial assays following the manufacturer's instructions.

RESULTS

Intra-assay precision and linearity were acceptable for both Hp and SAA. Intra-assay variation for high and low concentration of Hp and SAA were 9.74% and 17.31% and 16.49% and 12.89%, respectively. Inter-assay variation was higher for the low APP concentrations. Reference values for the healthy Iberian ibexes were (median, minimum, and maximum values) 0.2 (0.12-0.64) g/L for Hp and 4.74 (0.05-29.54) mg/L for SAA. Both Hp and SAA acted as a moderate and a major APP, respectively, and each could distinguish animals with turpentine-induced inflammation from those without. Hp and SAA did not change in asymptomatic BTV-infected animals.

CONCLUSION

This study validated Hp and SAA analytes and provided basal reference values for these analytes in the Iberian ibex. Both APPs were able to discriminate between healthy and diseased Iberian ibexes animals during turpentine-induced inflammatory processes.

Comparison of α2-macroglobulin synthesis by juvenile vs. mature rats after identical inflammatory stimulation

Synthesis of α2-macoglobulin (α2M) by 3-week-old juvenile rats was compared to that of mature 7- and 11-week-old rats. Serum concentrations of α2M, interleukin (IL)-6- and cytokine-induced neutrophil chemoattractant (CINC)-1 were measured by enzyme-linked immunosorbent assay. The area under the concentration vs. time curve (AUC) for α2M was significantly different among the three groups. The synthesis of α2M increased in an age-dependent manner. No significant difference was observed for the AUC of IL-6, but that of CINC-1 in 3-week-old rats was significantly lower than that in 7- or 11-week-old rats. These results suggest that synthesis of α2M was increased in mature compared to juvenile rats, possibly due to differences in liver function. The maximum concentration of CINC-1 in 3-week-old rats was observed 6 h after turpentine oil injection. The serum concentrations of IL-6 and CINC-1 increased more quickly in juvenile rats than in mature rats after inflammatory stimulation.

Investigation of the solubility and the potentials for purification of serum amyloid A (SAA) from equine acute phase serum--a pilot study

Background

Serum amyloid A (SAA) is useful as a diagnostic marker of systemic inflammation in horses, but only heterologous assays based on non-equine calibration and standardization are available for measurements of equine SAA. More accurate measurements could be obtained using purified species-specific SAA in native conformation for assay calibration and standardization. Further knowledge about the biochemical properties of SAA would facilitate a future production of native species-specific calibration material Therefore, the aim of the study was an investigation of the solubility and potentials for purification of equine SAA based on biochemical properties.

Freeze dried equine acute phase serum was dissolved in 70% 2-propanol, 8 M urea, and milli-Q water, respectively. Supercritical fluid extraction (SFE), size-exclusive chromatography (FPLC-SEC), and preparative isoelectric focusing (IEF) were performed in the attempt to purify. Immunostaining of IEF blots were used for isoform-specific detection of SAA in the preparations and purity was assessed by silverstained SDS-PAGE.

Findings

SAA was soluble in 70% 2-propanol, 8 M urea and Milli-Q water. SAA was not separated in the lipophilic or ampipathic fractions following SFE. SAA was included in a FPLC-SEC-fraction of 237 kDa, despite the molecular weight known to be much smaller, suggesting binding to other serum constituents. SAA precipitated following separation of other serum proteins by preparative IEF.

Discussion

No effective purification of SAA was achieved in the present study, but findings important for future investigations were made. The study suggested that SAA is not exclusively hydrophobic, but appears less hydrophobic when interacting with other serum components. These results suggest more complex aspects of solubility than previously believed, and indicate potentials for purification of native SAA.

Validation of an automated chemiluminescent immunoassay for salivary cortisol measurements in pigs

The aim of the current study was to validate an automated immunoassay for cortisol quantification in the saliva of pigs. The assay had intra- and interassay coefficients of variation lower than 16%, in all cases. The limit of detection was 0.016 µg/dl, and the lower quantification limit was 0.197 µg/dl. The assay also demonstrated a high level of accuracy, as determined by linearity under dilution and recovery tests. In addition, this assay was used to quantify cortisol in 2 models of stress: 1 in which animals were immobilized with a nose-snare and 1 in which pigs were transported for a duration of 30 min. In both cases, a significant increase (P < 0.01) in salivary cortisol was detected after the stressful situation. Overall, the assay validated in the present study could be used for the evaluation of cortisol changes in stressful situations.

Impairment of α(2)-macroglobulin synthesis in experimental hepatopathic rats treated with turpentine oil

The aim of this study was to investigate the synthesis of α(2)-macroglobulin (α2M) in hepatopathic rats injected with turpentine oil to induce acute inflammation. Hepatopathy was induced by oral administration of acetaminophen at a dose of 1 g/kg daily for 2 weeks or a 25% solution of carbon tetrachloride (CCl(4)) at 2 ml/kg body weight three times per week for 7 weeks. Acute inflammation was induced by intramuscular injection of turpentine oil at a dose of 1.0 ml/kg body weight. Serum concentrations of α2M were measured by enzyme-linked immunosorbent assay. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and total protein differed significantly between acetaminophen or CCl(4)-induced hepatopathic rats and acetaminophen control (AA-control) or CCl(4) control (CC-control) rats. Furthermore, pathological examination confirmed hepatopathy in rat livers. Peak serum concentrations and area under the time-concentration curve for α2M showed significant differences between hepatopathic rats and AA-control or CC-control rats. Thus, serum concentrations of α2M did not increase when compared with nontreated rats.

Fast measurement of serum amyloid A in different specimens from swine by using a new one-step time-resolved fluorescent immunoassay

The objective of the present study was to develop a one-step, fast, competitive time-resolved fluorescent immunoassay to determine porcine serum amyloid A (SAA) by using species-specific reagents. The assay consisted of an all-in-one format involving only 55 min of incubation that was adapted and validated for use in 3 different specimens: serum, saliva, and meat juice. The method had overall within- and between-run coefficients of variation under 8% and 12%, respectively, and coefficients of determination higher than 0.93 for linearity under dilution analysis for all specimens. The limits of detection were 0.32 mg/l, 0.28 mg/l, and 1.74 mg/l for serum, saliva, and meat juice measurements, respectively. Upper and lower limits of quantification were determined for each sample type and resulted in wide assay ranges that allowed a precise SAA measurement in all the fluids investigated. Statistically significant differences (P = 0.0004 for serum and P < 0.0001 for the saliva and meat juice samples) in SAA levels were found when healthy (n = 20) and diseased (n = 20) pigs were compared. The obtained results indicate that this fast, sensitive, and robust assay for SAA measurement could be of use to determine health and welfare status in swine by employing alternative samples to serum.

Serum acute phase proteins in cows with SARA (Subacute Ruminal Acidosis) suspect

The aim of this study was to evaluate the variations of Acute Phase Proteins (APPs) and other blood constituents during the onset of the sub-acute ruminal acidosis (SARA) pathological status. A total of 108 cows from 12 dairy herds were randomly selected and divided into three Groups of 36 animals each. All animals were subjected to a rumenocentesis. Group A was composed by subjects with a rumen pH>5.8, Group B was composed by subjects with a rumen pH ≤5.5≤5.8 and Group C was composed by subjects with a rumen pH<5.5. Blood samples were collected by jugular venipuncture and Haptoglobin (Hp), Serum Amyloid A (SAA), Total Proteins, Albumin and White Blood Cells (WBC) were determined. One-way ANOVA showed a statistical significance on Rumen pH, Hp, SAA. SARA seems not stimulate the APPs production from liver.

Acute phase proteins in animals

Acute phase proteins (APP) were first identified in the early 1900s as early reactants to infectious disease. They are now understood to be an integral part of the acute phase response (APR) which is the cornerstone of innate immunity. APP have been shown to be valuable biomarkers as increases can occur with inflammation, infection, neoplasia, stress, and trauma. All animals--from fish to mammals--have demonstrable APP, but the type of major APP differs by species. While the primary application of these proteins in a clinical setting is prognostication, studies in animals have demonstrated relevance to diagnosis and detection and monitoring for subclinical disease. APP have been well documented in laboratory, companion, and large animals. With the advent of standardized and automated assays, these biomarkers are available for use in all fields of veterinary medicine as well as basic and clinical research.

Development and validation of a novel competitive ELISA for the detection of serum amyloid A in pigs

The objective of this study was to develop a novel competitive ELISA to measure the acute phase protein serum amyloid A (SAA) in pigs using species-specific reagents. Polyclonal antibodies were produced in rabbits immunised with recombinant porcine SAA (rSAA) expressed in Escherichia coli. Both the rSAA and polyclonal antibodies were used to develop a novel competitive assay that was analytically and clinically validated. This assay had within- and between-run coefficients of variation of 8.6% and 25%, respectively, and demonstrated a high level of accuracy as determined by linearity-under-dilution (correlation coefficient, r=0.965). The analytical and functional limits of detection were 3.3 and 105.02mg/L, and the upper and lower quantification limits were 66.9 and 2.8mg/L, respectively. Statistically significant differences (P<0.0001) were found between the concentrations of SAA in healthy and diseased pigs. This novel assay precisely and sensitively measures SAA levels in pigs and will facilitate the more accurate assessment and study of the acute phase response in this species.

Prospects of using proteome technologies in the diagnostics of sexually transmitted infections and skin diseases

The article presents data from the literature describing up-to-date syphilis diagnostics methods used in the Russian Federation. It also describes main proteome techniques and gives the results of applying proteome technologies in the diagnostics of diseases including infectious ones, and prospects and opportunities for using direct proteome profiling to develop a new method for syphilis diagnostics are analyzed.

Monitoring the response of canine hyperadrenocorticism to trilostane treatment by assessment of acute phase protein concentrations

BACKGROUND

Acute phase proteins (APPS) include haptoglobin (Hp), C-reactive protein (CRP) and serum amyloid A (SAA). Increased Hp concentrations may be induced by endogenous or exogenous glucocorticoids in dogs.

OBJECTIVES

To assess whether control of hyperadrenocorticism (HAC) affects the concentrations of Hp, CRP, SAA, alkaline phosphatase (ALKP) and cholesterol, to determine whether these analytes can be used to assess control of HAC following trilostane treatment, and whether a combination of these tests offers a valid method of assessing disease control.

METHODS

Hp, CRP, SAA, ALKP and cholesterol were assessed in 11 dogs with spontaneous HAC before and after treatment with trilostane. Adequate control of HAC was defined as post-ACTH cortisol less than 150 nmol/l.

RESULTS

Significant reductions in Hp, ALKP, cholesterol and SAA (P<0.05) but not of CRP were found after control of HAC. Only Hp, cholesterol and ALKP were moderately informative (Se & Sp>0.7) of disease control when compared to adrenocorticotropin or corticotropin (ACTH) stimulation test. SAA and CRP were unhelpful (Se & Sp<0.7). The analysis of the combination of the analytes did not improve the correlation with ACTH stimulation test.

CLINICAL RELEVANCE

Relying on these analytes does not provide additional information over ACTH stimulation test results when assessing control of HAC treated with trilostane.

Evaluation of a commercially available apparatus for measuring the acute phase protein serum amyloid A in horses

The aim of this study was to investigate the reliability of an immunoturbidometric assay for measuring the acute phase protein serum amyloid A (SAA) in horses in clinical practice. The assay was compared to a previously validated assay, and overlap performance was assessed by measuring the concentration of SAA in clinically healthy horses and horses with inflammatory and non-inflammatory diseases. In pools of serum with low and high SAA concentrations the assay's intra-assay coefficients of variation were 11.7 per cent and 4.6 per cent, and its interassay coefficients of variation were 9.1 per cent and 5.6 per cent, respectively. Slight inaccuracies were observed, but they were negligible in comparison with the range of the SAA response. The assay systematically underestimated the concentrations of SAA in comparison with the results of the validated assay. The assay detected the expected difference in SAA concentrations between the healthy and diseased horses.

Development and validation of an ELISA for the quantification of pig major acute phase protein (Pig-MAP)

Measurement of acute phase proteins (APPs) levels in blood is increasingly being used for monitoring health and welfare in farm animals. In this work a sandwich-type ELISA for the quantification of pig Major Acute phase Protein (Pig-MAP), one of the main APP in pigs, has been developed and validated. Two Pig-MAP specific monoclonal antibodies were developed in mouse. One of the monoclonal antibodies was fixed to microtiter plates and the other was coupled to horseradish peroxidase and used as detection antibody. To calibrate the assay dilutions of a standard pig serum of known Pig-MAP concentration were added to the plate in each assay. The assay showed good accuracy, kept linearity under dilution and recovery was proportional. The detection limit was 0.1 microg/mL. Precision was adequate with coefficients of variation lower than 8% for both inter and intra-assays. A good linear correlation between Pig-MAP concentration values obtained by ELISA and by radial immunodiffusion, used as reference method, was found (r = 0.978; beta = 1.02). Pig-MAP concentration was analysed in serum samples obtained from two pig herds of different health status (10 animals per age and herd, of 10, 12, 14, 18 weeks of age). Mean values obtained in the farm of low health status were higher than the obtained in the farm of high health status (p<0.001). In the farm of high health status, mean Pig-MAP concentration remained constant at the different ages analysed (mean values of 0.83+/-0.18 mg/mL) whereas in the farm of low health status differences between age groups were found. In this farm (low health status) mean values for the total of pigs analysed were of 1.68+/-0.74 mg/mL.

Canine serum C-reactive protein detected by means of a near-patient test for human C-reactive protein

OBJECTIVES

The aim of the study was to evaluate the reliability of a rapid human C-reactive protein near-patient slide reversed passive latex agglutination test (Randox) for the semi-quantitative determination of canine serum C-reactive protein.

METHODS

The concentration of C-reactive protein was determined in 244 canine serum samples by an established automated immunoturbidimetric method and in various predilutions by a commercially available reversed passive latex agglutination test for human C-reactive protein. The results were compared to assess if the reversed passive latex agglutination test reflected the results of the established method with special emphasis on the reversed passive latex agglutination test's ability to identify samples characterised as positive or negative by the established method.

RESULTS

The reversed passive latex agglutination test reflected the C-reactive protein concentration in canine serum samples at all the tested predilutions (undiluted, 1:4, 1:8 and 1:16). When applying a predilution of 1:8, the positive and negative analytical predictive values for discriminating between positive and negative samples (according to the established quantitative method) were high (0.94 [0.82 to 0.99] and 0.97 [0.93 to 0.99], respectively).

CLINICAL SIGNIFICANCE

In conclusion, this near-patient test was able to reflect the serum C-reactive protein concentration in canine samples in a reliable and clinically useful manner and could be applicable for general practice for evaluating C-reactive protein levels in canine serum.

Pig-MAP and haptoglobin concentration reference values in swine from commercial farms

Pig-MAP (Major Acute-phase Protein) and haptoglobin concentrations were determined in pigs from commercial farms, and reference intervals obtained for different productive stages. Pig-MAP serum concentrations were lower in sows than in adult boars (mean values 0.81 vs. 1.23 mg/mL) and the opposite was observed for haptoglobin (1.47 vs. 0.94 mg/mL). No differences were found between parities, except for a minor decrease in haptoglobin concentration in the 4th parity. A linear correlation between pig-MAP and haptoglobin concentration was observed. In the period 4-12 weeks of life, pig-MAP mean concentrations were around 1mg/mL, being lower in the finishing period (0.7-0.8 mg/mL). Haptoglobin concentrations increased with time, from around 0.6 mg/mL at 4 weeks of age to 1.4 mg/mL at 12 weeks. Mean values of around 0.9 mg/mL were observed in the finishing period. A wider distribution of values was observed for haptoglobin than for pig-MAP concentrations. Differences between herds were observed, with the highest values obtained in a herd with signs of respiratory disease.

Analytical validation of commercially available methods for acute phase proteins quantification in pigs

The aim of this study was to validate commercially available methods for porcine haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA) and major acute phase protein (Pig-MAP) determinations. Intra and inter assay coefficients of variation (CVs) were lower than 20% in all cases with exception of inter assay CVs for CRP and Pig-MAP assays with samples of low acute phase proteins concentration, and for SAA assay at any acute phase proteins concentration. All methods showed good linearity and detection limits were low enough to detect APPs levels in healthy animals. Hp and SAA were very affected by haemolysis. Lipaemia influenced mainly on SAA determination. Over 15-fold increase was observed in CRP and SAA concentrations after artificially induced inflammation by a single subcutaneous dose of turpentine, whereas Hp and Pig-MAP increased less than 5-fold.

Comparison of two automated spectrophotometric methods for ceruloplasmin measurement in pigs

Ceruloplasmin (Cp) determination could provide an objective measure of the health status of an animal and could be used as marker of animal health and welfare (Skinner, 2001) (Skinner, J. G., 2001. Special report. International standardization of acute phase proteins. Veterinary Clinical Pathology 30, 2-7.) but only manual methods have been reported to determine Cp concentrations in pigs (McCosker, 1961; Toussaint et al., 1995; Eckersall et al., 1996) (McCosker, P. J., 1961. Paraphenylenediamine oxidase activity and copper-levels in mammalian plasmas. Nature. 190, 887-889; Toussaint, M. J. M., Van Ederen, A. M., Gruys, E., 1995. Implication of clinical pathology in assessment of animal health and in animal production and meat inspection. Comparative Haematology International 5, 149-157; Eckersall, P. D., Saini, P. K., McComb, C., 1996. The acute phase response of acid soluble glycoprotein, alpha(1)-acid glycoprotein, ceruloplasmin, haptoglobin and C-reactive protein, in the pig. Veterinary Immunology and Immunopathology 51, 377-385). In the present study two automated methods based on the use of two different substrates for the determination of serum ceruloplasmin in pigs were developed, evaluated and compared. Both methods showed a good precision and detection limits, with no signs of inaccuracy and could be applied to biochemical autoanalyzers usually found in clinical laboratories using only minimal amounts of serum. Additionally the behaviour of Cp in experimental and clinical situations was studied showing an increase of around two fold after turpentine administration and significantly higher values in cases of pigs with inflammatory conditions when compared with healthy pigs.

Pig major acute-phase protein and apolipoprotein A-I responses correlate with the clinical course of experimentally induced African Swine Fever and Aujeszky's disease

In the present work, we studied the acute phase protein response after experimental virus infection in pigs. The animals were experimentally infected with African Swine Fever (ASF) or Aujeszky's disease (AD) viruses. The clinical course of ASF infection correlated with increasingly high levels of pig Major Acute-phase Protein (pig-MAP) (mean value of 6 mg/mL on day 6 post infection (p.i.), from 6 to 9 times higher than day 0) and sharp apolipoprotein A-I (apo A-I) decrease (mean value of 0.5 mg/mL, from 4 to 10 times lower than day 0 on day 4 p.i.). AD-clinical signs appeared at day 3 p.i., both in vaccinated (moderate clinical signs) and non-vaccinated pigs (severe outcome within 48 h p.i.). Pig-MAP and apo A-I profiles also followed clinical signs (changing from 0.70 mg/mL to around 3 mg/mL and from around 3 mg/mL to 0.96 mg/mL, respectively in non-vaccinated animals), with minor changes in concentration in the vaccinated group. Haptoglobin levels significantly increased in ASF and AD infected animals (mean maximum values of 2.77 and 3.96 mg/mL, respectively). Minor differences for the C-Reactive Protein in the case of ASF were observed, whereas its concentration increased more than 7 times in AD-infection. The albumin level was not modified in either case. The correlation of clinical signs to our data suggests the potential use of pig-MAP and apo A-I in monitoring infections in swine.

Evaluation and comparison of two immunoturbidimetric assays for the heterologous determination of porcine serum C-reactive protein

The objective was first to evaluate the performance (intra- and inter-assay imprecision, inaccuracy, detection limit and overlap performance) of two different commercially available human C-reactive protein (CRP) immunoturbidimetric assays (TIA) applied to porcine serum CRP; and secondly to investigate inter-laboratory discrepancies and the influence of calibration materials when comparing results. The intra-laboratory performance seemed acceptable for clinical purposes for both assays with excellent overlap performance, acceptable detection limits, no significant inaccuracies and low imprecision. Although a significant discrepancy in the measured CRP levels was observed when comparing results, the methods agreed significantly on diagnostic classification, suggesting a low clinical significance. Both assays performed reliably for the heterologous determination of porcine serum CRP for clinical purposes. The results emphasise the need to establish species-specific standards to decrease inter-laboratory discrepancies.

A time-resolved immunofluorometric assay for porcine C-reactive protein quantification in whole blood

A time-resolved immunofluorometric assay (TR-IFMA) for C-reactive protein (CRP) determination in whole blood of pigs was developed and validated. CRP was isolated from porcine acute-phase serum by affinity chromatography on agarose, coupled with phosphorylethanolamine and polyclonal antibodies to porcine CRP were purified from antiserum raised in sheep immunized with porcine CRP. Intra- and inter-assay coefficients of variation (CVs) were in the range 3.13-7.19% and 7.06-15.66%, respectively, showing good precision. The assay measured the CRP values in a proportional and linear manner (r=0.99); additionally, CRP concentrations measured in whole blood by the present TR-IFMA and in serum by an established immunoturbidimetric assay were highly correlated (R(2)=0.97). The limit of detection of the method was 0.0028 mg/L. Significantly lower CRP concentrations were observed after 7 days of sample storage at 4 degrees C. The injection of turpentine oil caused a significant increase in CRP concentrations and significantly higher CRP concentrations were observed in pigs with pathological processes compared to healthy animals.

The acute phase protein haptoglobin and its relation to oxidative status in piglets undergoing weaning-induced stress

Haptoglobin (Hp) prevents the hemoglobin driven generation of hydroxyl radicals and lipid peroxides. Hp can reduce the neutrophil respiratory burst and is an antioxidative molecule in its own right. We aimed to evaluate Hp concentrations, oxidative stress and antioxidative capacity in blood during weaning and to characterise potential relationships between these parameters. Two batches of 10 piglets each (2 trials) weaned at the age of 27-30 days were fed a starter feed mix ad libitum. Blood samples were taken 1 week before weaning and at weekly intervals thereafter. Oxidative stress was monitored via the D-ROM system, antioxidative capacity was measured with the TEAC assay and Hp concentrations were measured by ELISA. Neutrophil phagocytic activity and oxidative burst were examined via flow-cytometry. Body weights were recorded weekly. Hp concentrations were increased in both trials post-weaning (P < 0.01); oxidative stress and oxidative burst were elevated in trial I (P < 0.005). In trial I, Hp and ROM values returned to baseline levels at 6 weeks post-weaning. The piglets in trial II showed respiratory symptoms and maintained elevated Hp concentrations. ROM values and Hp were related (r = 0.58; P < 0.01). Hp and body weight gain were inversely related post-weaning.

Analytical and Clinical Validation of a Time-resolved Immunofluorometric Assay (TR-IFMA) for Canine C-reactive Protein in Serum

A time-resolved immunofluorometric assay (TR-IFMA) was developed for the determination of C-reactive protein (CRP) in canine serum. CRP was isolated from canine acute-phase serum by affinity chromatography on agarose coupled with phosphorylethanolamine. This isolated dog CRP was used as standard to calibrate the assay. Intra-assay and inter-assay coefficients of variation were in the ranges 5.3-7.1% and 4.8-13.3%, respectively. Accuracy, evaluated by adding 2 and 10 microg/ml of CRP to serum samples, provided recoveries of 99.9% and 106.8%. High correlation was found between CRP measurements by TR-IFMA and a by commercial enzyme-linked immunosorbent assay (R2 = 0.98). The limit of detection for the TR-IFMA method was 0.000067 microg/ml and the measurement of CRP in serial dilutions of acute-phase dog sera generated curves with the same slope as the one constructed with purified CRP. The TR-IFMA provides a precise, accurate and highly sensitive assay for CRP determination in dog samples. CRP levels in dogs with different diseases ranged between 10.2 and 210.7 microg/ml and were significantly higher than those observed in healthy dogs (< 7.1 microg/ml).

The concentration of apolipoprotein A-I decreases during experimentally induced acute-phase processes in pigs

In this work, apolipoprotein A-I (ApoA-I) was purified from pig sera. The responses of this protein after sterile inflammation and in animals infected with Actinobacillus pleuropneumoniae or Streptococcus suis were investigated. Decreases in the concentrations of ApoA-I, two to five times lower than the initial values, were observed at 2 to 4 days. It is concluded that ApoA-I is a negative acute-phase protein in pigs.

Plasma proteome of severe acute respiratory syndrome analyzed by two-dimensional gel electrophoresis and mass spectrometry

We have investigated the plasma proteome by using 2D gel electrophoresis and MS from patients with severe acute respiratory syndrome (SARS). A complete proteomic analysis was performed on four patients with SARS in different time courses, and a total of 38 differential spots were selected for protein identification. Most of the proteins identified are acute phase proteins, and their presence represents the consequence of serial cascades initiated by SARS-coronavirus infection. There are several proteins that have never been identified in plasma before using 2D gel electrophoresis, among which peroxiredoxin II was chosen for further study by analyzing additional 20 plasma samples from patients with probable and suspected SARS and patients with fever, respectively. The results showed that the level of plasma peroxiredoxin II in patients with SARS is significantly high and could be secreted by T cells. Taken together, our findings indicate that active innate immune responses, along with the oxidation-associated injuries, may play a major role in the pathogenesis of SARS.

A Comparison of Acute Phase Protein Measurements and Meat Inspection Findings in Cattle

The acute phase proteins haptoglobin (Hp) and serum amyloid-A (SAA) are increased in the blood of cattle with infectious or inflammatory diseases. As it is important to identify such cattle at meat inspection, a study was undertaken to compare the levels of Hp and SAA in blood samples from cattle at abattoir with the post-mortem meat inspection findings. The serum concentrations of Hp and SAA were determined in healthy beef cattle (n = 16); healthy dairy cows with no pathological conditions (n = 22); and cows with pathologic conditions (n = 62). The last group was subdivided into cows with acute pathological conditions (n = 10) and those with non-acute pathological conditions (n = 52). The mean (+/-SD) Hp levels in plasma from beef cattle and cows without pathological conditions found were 0.11 +/- 0.08 mg/mL and 0.02 +/- 0.03 mg/mL, respectively, and the difference was statistically significant (p < 0.001). However, mean Hp level in cattle with pathological conditions was 0.27 +/- 0.40 mg/mL, significantly higher than the mean values of either group of healthy animals (p < 0.01 versus healthy dairy cows and p < 0.001 versus healthy beef cattle). The mean SAA concentration in plasma samples from 22 healthy dairy cows (with no pathological conditions found) was 51 +/- 38 microg/mL, significantly higher (p < 0.01) than the mean SAA value of 29 +/- 21 microg/mL calculated from 16 plasma samples from healthy beef cattle. In the group of 62 cows with pathological conditions, the mean SAA level was 94 +/- 115 microg/mL being significantly higher than the respective value in either groups of healthy animals (p < 0.01 versus healthy cows and p < 0.001 versus healthy beef cattle). Considerations of the acute phase proteins results obtained from the animals with pathological conditions did not reveal a clear association between acute phase proteins levels and respective specific pathological conditions, although there was a significant correlation between Hp and SAA concentrations at the individual animal level when all results were considered (R = 0.75, n = 100, p < 0.001). Nevertheless, when the dairy cows with pathological conditions were subdivided, some significant differences in mean values of acute phase proteins were observed enabling differentiation between animals with (broadly categorised) acute and non-acute pathological conditions. Significantly higher Hp (p < 0.05) and SAA (p < 0.05) concentrations were found in the acute pathology group than in the non-acute pathology group. Overall, the result of the present study indicated that the acute phase protein analysis could be an additional and useful tool enabling separation of "suspect" from "non-suspect" animals during ante mortem inspection within a modernised meat inspection system.

Current research on acute phase proteins in veterinary diagnosis: an overview

The acute phase proteins (APP) are a group of blood proteins that contribute to restoring homeostasis and limiting microbial growth in an antibody-independent manner in animals subjected to infection, inflammation, surgical trauma or stress. In the last two decades, many advances have been made in monitoring APP in both farm and companion animals for clinical and experimental purposes. Also, the mechanism of the APP response is receiving attention in veterinary science in connection with the innate immune systems of animals. This review describes the results of recent research on animal APP, with special reference to their induction and regulatory mechanisms, their biological functions, and their current and future applications to veterinary diagnosis and animal production.

Development of an enzyme immuno assay for the determination of porcine haptoglobin in various body fluids: testing the significance of meat juice measurements for quality monitoring programs

Quantification of haptoglobin (Hp), an acute phase protein, in blood is presently discussed as being useful to monitor animal health. We developed an enzyme immuno assay (EIA) which is specific for porcine Hp, is not impaired by hemolytic samples and is sufficiently sensitive to be applied in meat juice. Hp was purified from porcine serum by affinity chromatography on hemoglobin Sepharose followed by gel filtration. A specific rabbit antiserum was obtained. In a competitive approach, biotinylated porcine Hp was used as tracer and incubated with Hp standard or sample in microtiter plates. The limit of detection was 0.02 mg/l, parallelism of sample dilutions was proven; recovery of Hp added to serum samples was 96.4 +/- 4.7%. The coefficients of intra and inter-assay variation were 3.3 (n=5) and 10.2% (n=16), respectively. Hp was reliably quantified in blood serum and plasma, whole blood, saliva and meat juice. For healthy pigs of different ages (4 weeks and 6 months), mean Hp concentrations of about 0.5-0.7 mg/ml were observed. To test the significance of Hp measurements in other matrices, samples were obtained from fattening pigs or from slaughter pigs. Blood serum or plasma was collected in parallel. In whole blood, Hp concentrations were about 40% lower than in plasma, but were closely related (n=24,r=0.85,P<0.001). Saliva Hp concentrations ranged between 0.3 and 3.0 microg/ml and were marginally related with blood plasma concentrations (n=93,r=0.35,P<0.001). From 106 hybrid slaughter pigs (100-110 kg) blood and muscle samples (diaphragmatic pillar, d.p.; m. brachiocephalicus, m.b.) were collected. Meat juice was obtained after freezing and thawing. Concentrations were 0.39+/-0.5 mg/ml in serum and 0.04+/-0.06 mg/ml in meat juice. Hp concentrations in blood were closely correlated with those in d.p. juice (P<0.001,r=0.750) and m.b. juice (P<0.001,r=0.776). In view of the many reports on Hp measurements being predictive for animal health even in the subclinical range, we conclude that Hp quantification in meat juice might be useful to assess meat quality at slaughter and further along the processing chain in terms of animal health.

Acute phase proteins in serum and milk from dairy cows with clinical mastitis

The serum concentrations of haptoglobin, serum amyloid A and alpha1 acid glycoprotein were determined in serum collected from healthy dairy cows and cows with clinical mastitis, graded as mild (clots in milk) or moderate (clots in milk and visible signs of inflammation in the mammary gland/s) to assess their relative diagnostic value in detecting the disease. The concentrations of haptoglobin and serum amyloid A were also measured in milk collected from infected and uninfected quarters. The concentrations of haptoglobin and serum amyloid A were higher in the serum and milk from the cows with mild or moderate mastitis. The diagnostic value of haptoglobin in differentiating between healthy animals and those with mastitis gave sensitivities and specificities of 82 per cent and 94 per cent respectively with serum and 86 per cent and 100 per cent with milk. The diagnostic value of serum amyloid A in differentiating between healthy animals and those with mastitis gave sensitivities and specificities of 83 per cent and 90 per cent with serum and 93 per cent and 100 per cent with milk. The diagnostic value of serum alpha1 acid glycoprotein in differentiating between healthy animals and those with mastitis gave sensitivities and specificities of 62 per cent and 91 per cent.

The acute phase response of haptoglobin and serum amyloid A (SAA) in cattle undergoing experimental infection with bovine respiratory syncytial virus

The ability of a pure virus infection to induce an acute phase protein response is of interest as viral infections are normally considered to be less efficient in inducing an acute phase protein response than bacterial infections. This was studied in a bovine model for infection with bovine respiratory syncytial virus (BRSV), analysing the induction of the two most dominant bovine acute phase proteins haptoglobin and serum amyloid A (SAA). Strong and reproducible acute phase responses were detected for both proteins, peaking at around 7-8 days after inoculation of BRSV, while no response was seen in mock-inoculated control animals. The serum concentrations reached for SAA and haptoglobin during the BRSV-induced acute phase response were generally the same or higher than previously reported for bacterial infections in calves. The magnitude and the duration of the haptoglobin response was found to correlate well with the severity of clinical signs (fever) and with the extent of lung consolidation while SAA responded most rapidly to infection.