Effectiveness of Capillary Electrophoresis Fluoroimniunoassay of Blood PrPSc for Evaluation of Scrapie Pathogenesis in Sheep

Management of prion diseases in livestock would benefit greatly from availability of a validated blood test. A promising immunocapillary electrophoresis technique (also known as capillary electrophoresis fluoroimmunoassay) to detect abnormal prion protein in blood from live sheep is evaluated here. Capillary electrophoresis fluoroimmunoassay was applied to analysis of extracted blood from scrapie-exposed sheep ( n = 87; 347 samples) at various stages of incubation, and to control sheep ( n = 194; 489 samples). Overall, test values for the control and test populations were not significantly different, and a similar proportion of control (7%) and test (10%) sheep were classified as positive. Over 2−3 month intervals from birth until clinical disease, test specificity and sensitivity ranged from 66.7% to 100% and 0% to 66.7%, respectively, indicating poor diagnostic performance at all stages of pathogenesis. In routine application, in its present form, the capillary electrophoresis fluoroimmunoassay procedure proved to be insufficiently robust for use as a blood test for scrapie diagnosis.

Validation of an assay for quantification of alpha-amylase in saliva of sheep

The objective of this study was to develop a time-resolved immunofluorometric assay (TR-IFMA) for quantification of salivary alpha-amylase in sheep. For that purpose, after the design of the assay, an analytical and a clinical validation were carried out. The analytical validation of the assay showed intra- and inter-assay coefficients of variation (CVs) of 6.1% and 10.57%, respectively and an analytical limit of detection of 0.09 ng/mL. The assay also demonstrated a high level of accuracy, as determined by linearity under dilution. For clinical validation, a model of acute stress testing was conducted to determine whether expected significant changes in alpha-amylase were picked up in the newly developed assay. In that model, 11 sheep were immobilized and confronted with a sheepdog to induce stress. Saliva samples were obtained before stress induction and 15, 30, and 60 min afterwards. Salivary cortisol was measured as a reference of stress level. The results of TR-IFMA showed a significant increase (P < 0.01) in the concentration of alpha-amylase in saliva after stress induction. The assay developed in this study could be used to measure salivary alpha-amylase in the saliva of sheep and this enzyme could be a possible noninvasive biomarker of stress in sheep.

Effect of repeated administration of lipopolysaccharide on inflammatory and stress markers in saliva of growing pigs

Although saliva could be considered to be an ideal biological sample for evaluation of biomarkers relating to stress and inflammatory responses in pigs, little is known about how these might be influenced by the presence of endotoxaemia. In the present study, the response to repeated administrations of lipopolysaccharide (LPS) was investigated, using a panel of salivary stress markers such as chromogranin A (CgA) and cortisol, as well as inflammatory/immune markers such as haptoglobin (Hp), C-reactive protein (CRP) and immunoglobulin A (IgA). Sixteen growing pigs were adapted to experimental conditions for 3 weeks, after which, 10 of the pigs were selected to receive three doses of LPS at 48 h intervals. Saliva samples were taken from all pigs prior to any LPS administration (baseline) and at time points corresponding to 3 h after each injection of LPS (T1, T2 and T3). Results showed that repeated administration of LPS induced significant elevation of salivary markers of hypothalamic-pituitary-adrenal (cortisol) and immune (Hp, CRP and IgA) activity compared to baseline levels (P < 0.05). However, rectal temperature, CRP and cortisol data suggested that the amplitude of the inflammatory response decreased with successive LPS administrations. Thus, measurement of salivary biomarkers could be a practical tool for evaluating the inflammatory response to endotoxaemia in pigs. In the case of chronic inflammatory states, salivary Hp and IgA might be more sensitive markers than CRP or cortisol.

Dual-label time-resolved fluoroimmunoassay for simultaneous quantification of haptoglobin and C-reactive protein in meat juice from pigs

A new method was developed to simultaneously measure 2 acute-phase proteins (APPs) by time-resolved immunofluorometry. The assay, based on double-label quantification of haptoglobin (Hp) and C-reactive protein (CRP) in meat juice samples from pigs, was constructed by use of a combination of europium and samarium chelate lanthanides as labels. Meat juice samples from 154 pigs were used for analytic and clinical validation of the assay through determination of precision, accuracy, limit of detection, and quantification. The analytic performance of the assay was satisfactory, with good intra-assay and interassay precision and accuracy. The levels of Hp and CRP were increased in the meat juice samples of diseased animals compared with healthy ones. According to the results, higher sensitivity could be achieved if the cut-off values of both proteins were taken into account for clinical relevance rather than used individually. Since the dual assay saved both time and sample, it could be used as a rapid and sensitive screening test in porcine production.

Effects of haemolysis, lipaemia and bilirubinaemia in canine C-reactive protein and haptoglobin determination by time-resolved fluorometry: short communication

C-reactive protein (CRP) and haptoglobin (Hp) are well-known acute phase proteins in the dog. Currently, a commercial ELISA and a colorimetric assay are the methods of choice for measuring CRP and Hp, respectively; however, these assays showed interference when using haemolysed, lipaemic or hyperbilirubinaemic samples. Recently, time-resolved immunofluorometric assays (TR-IFMAs) have been developed for measuring canine CRP and Hp. The aim of the present study was to evaluate the effect of increasing concentrations of haemoglobin, lipids and bilirubin in CRP and Hp serum measurements using these new fluoroimmunoassays. Haemolysis was produced by freezing blood cells at -20 degrees C. The haemolysate was added to pooled sera at final concentrations of 0, 2.5, 5, 10, 20 and 40 g/L. A commercial emulsion of triglycerides was added to homologous pooled sera at 0, 0.35, 0.7, 1.4, 2.8, 5.6 and 11.2 mmol/L. Bilirubin, initially dissolved in dimethyl sulphoxide, was added to pooled sera at 0, 64.2, 128.4, 256.8, 513.7 and 1027.4 micromol/L. Addition of fresh haemolysate, triglycerides or bilirubin to serum samples did not affect either CRP or Hp concentrations (P > or = 0.18), so the TR-IFMAs could be an alternative to the traditional tests for measuring canine CRP and Hp in those laboratories where immunofluorometric assays are available.

Persistent infection with and serologic cross-reactivity of three novel murine noroviruses

According to serologic testing, murine norovirus is the most prevalent viral pathogen in contemporary laboratory mice. Previously, murine norovirus 1 (MNV-1) was the only norovirus reported to infect research mice. In this study, 3 novel murine norovirus strains--MNV-2, MNV-3, and MNV-4--were isolated from geographically separate mouse research colonies. All 4 murine norovirus strains used as individual antigens in microsphere fluorescent immunoassays displayed serologic cross-reactivity to serum from mice inoculated with MNV-1, MNV-2, MNV-3, or MNV-4. In addition, reverse transcriptase-polymerase chain reaction analysis at 8 wk postinoculation detected virus in the feces and tissues of all mice experimentally inoculated with MNV-2, MNV-3, or MNV-4. This finding suggests that mice can have prolonged fecal shedding of and can become persistently infected with murine noroviruses.

Concentrations of C-reactive protein in effusions in dogs

The concentration of C-reactive protein (CRP) was measured in effusions from 50 dogs to assess the potential for measuring this protein to differentiate body cavity fluids. The effusions were classified as either transudates, modified transudates or exudates according to their total protein concentration, total nucleated cell count, cytological findings and aetiology, and the concentration of CRP was determined by a time-resolved immunofluorometric assay. There were significant differences between the concentrations of CRP in the three types of effusion; the highest concentrations were observed in the exudates (4.47 to 54.59 microg/ml), the lowest were in the transudates (0.0094 to 7.87 microg/ml), and the modified transudates contained intermediate concentrations of CRP (0.045 to 10.78 microg/ml). A cut-off value of 4 microg/ml had a sensitivity of 100 per cent and a specificity of 94.4 per cent for differentiating transudates from exudates, and a cut-off value of 11 microg/ml had a sensitivity of 88.2 per cent and a specificity of 100 per cent for distinguishing modified transudates from exudates. However, a cut-off value of 1 microg/ml had a lower sensitivity (80 per cent) and an unacceptably low specificity (66.7 per cent) for differentiating transudates from modified transudates.

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).

Application of a Solid-Phase Fluorescence Immunoassay to Determine Oxytetracycline and Tetracycline Residues in Tissue of Olive Flounder (Paralichthys olivaceus)

Parallux, a solid-phase fluorescence immunoassay (SPFIA) developed for antibotics residue detection in milk, was applied for analysis of fish tissue. The recommended therapeutic doses of oxytetracycline (OTC, 100 g/ton water, withdrawal period 30 days) and tetracycline (TC, 150 g/ton water, withdrawal period 30 days) were treated to a group of 35 olive flounders (Paralichthys olivaceus) using dipping administration. Muscle was sampled before and after drug treatment 1st, 2nd, 3rd, 5th, 7th, and 14th day. The concentration of oxytetracycline in muscle, determined by SPFIA, was compared with that of internal standard (100 ppb as oxytetracycline). The S/C ratio of sample inhibition value to cutoff inhibition value was employed as an index to determine the muscle residue in olive flounder. To investigate the recovery rate, and standard solutions were added to muscle samples to give final concentrations in muscle of 0.1 and 0.5 microg/ml. The recovery rates of all spiked samples were >89% of the spiked value. OTC and TC were detected in muscle of fishes treated until the 3rd day of withdrawal period. The present study showed that the SPFIA can be easily adopted in predicting tissue residues for OTC and TC in farmed fishes.

Changes in Circulating and Testicular Levels of Inhibin A and B During Postnatal Development in Bulls

We investigated testicular and circulating levels of dimeric inhibins in Holstein bulls from the infantile to postpubertal periods (5 to 50 weeks of age) and examined the relationship between the profiles of circulating dimeric inhibins and FSH. Concentrations of total inhibin and inhibin B in the testis were highest at 4 to 5 weeks of age but decreased gradually as the bulls aged. Testicular inhibin A levels showed a gradual decline to a nadir at 15 to 26 weeks of age, but by 39 weeks, they were high again. The contents of total inhibin, inhibin A, and inhibin B per testis generally increased with age. Fractionation of testicular homogenates obtained from 15-week-old bulls by a combination of immunoaffinity chromatography and SDS-PAGE confirmed the presence of two major molecular weight forms (32 and 45 kDa) of dimeric inhibins in the testes. Circulating levels of total inhibin and inhibin A showed a significant increase in bulls at around 10 to 14 weeks of age compared to the levels between 5 and 7 weeks of age but decreased thereafter. However, immunoreactivity for inhibin B was not detected in the peripheral circulation, probably because of low sensitivity of the inhibin B assays. The concentrations of plasma FSH were high at 5 weeks of age but declined to lower levels between 11 and 40 weeks, and then increased from 41 weeks onward. There was no significant correlation between the plasma levels of FSH and inhibin A or total inhibin. The results clearly indicate that the bull testis produces inhibin A and B and secretes at least inhibin A into the circulation during postnatal development. However, the profile of circulating FSH in bulls shows no reciprocal relationship with the inhibin A or total inhibin profile during the postnatal period.

C-reactive protein measurement in canine saliva

An established time-resolved immunofluorometric assay designed for measurement of C-reactive protein (CRP) in canine blood was evaluated and validated for use in canine saliva. C-reactive protein was measured in saliva specimens from 5 healthy dogs before and after the injection of casein and in 37 dogs with different disease conditions. The analytical and functional limits of detection were 0.000053 microg/ml and 0.0091 microg/ml, respectively, and intra- and interassay coefficients of variation ranged between 6.7-9.9% and 8.5-16.5%, respectively. A recovery experiment showed no significant disagreement between detected values and expected ones, and saliva CRP concentration was measured in a linear and proportional manner. A positive correlation was found between CRP levels obtained in saliva and serum samples in the experimental (R2 = 0.76) and clinical studies (R2 = 0.70). The assay was able to detect significant differences between salivary CRP levels in healthy dogs and dogs with inflammatory processes. These results suggest that saliva can be used for CRP measurement in dogs. The use of saliva presents the advantage of an easier and less stressful sampling method for the animals, which might be performed outside of hospital environments.

The potential risk of Dirofilaria immitis becoming established in the Czech Republic by imported dogs

We examined 110 dogs, imported or born to imported females or living together with imported dogs in kennels, for the presence of Dirofilaria immitis, and assessed the climatic conditions in the Czech Republic that may promote spread of the disease. Relevant techniques were used to detect specific antigen, specific antibodies and microfilariae. The presence of antigen was detected in one imported dog, microfilariae were not found and antibodies were detected in 30.5% of the imported dogs. No heartworm was found in dogs, which did not travel outside of the Czech Republic. The evaluation of temperature charts showed that it was possible for at least one heartworm generation to develop under climatic conditions in the Czech Republic.

Development of a time-resolved fluorometry based immunoassay for the determination of canine haptoglobin in various body fluids

A time-resolved immunofluorometric assay (TR-IFMA) was developed for the determination of haptoglobin (Hp) in canine serum. Haptoglobin was purified from canine acute phase serum by ammonium sulphate precipitation followed by gel filtration. This isolated dog Hp was used as the standard to calibrate the assay. Intra- and inter-assay coefficients of variation of the assay were, respectively, 5.7% and 16.6% at 0.51 mg/mL, 2.4% and 10.6% at 2.1 mg/mL and 10.5% and 11.9% at 32.5 mg/mL. The dilution of serum samples with high Hp concentrations resulted in linear regression equations with R2 of 0.99 and 0.97. A high correlation was found in serum Hp measurements by TR-IFMA and a commercial assay based on peroxidase activity of haemoglobin bound to haptoglobin (R2 = 0.96). The limit of detection for the TR-IFMA method was 0.002 microg/mL. The addition of fresh haemolysate to serum samples did not affect the haptoglobin concentration (P = 0.694). Statistical differences (P < 0.003) were found between healthy dogs and dogs with different pathological processes. In whole blood, Hp concentrations were much lower than in serum but closely related (R2 = 0.84) whereas saliva Hp concentrations were poorly related with serum concentrations (R2 = 0.53). However, the concentration of Hp in saliva was significantly (P < 0.039) higher in dogs with pathological processes compared to healthy dogs. The assay sensitivity was adequate to also be applied to whole blood and saliva specimens.

Development of an optical immunosensor based on the fluorescence of Cyanine-5 for veterinarian diagnostics

A model optical immunosensor was developed to quantify an antibody present in a sample by measuring the fluorescence of Cyanine-5 conjugated with the antibody, using a competitive and a sandwich immunoreaction configuration, with the antigen immobilised in controlled pore glass beads. At pH 2, 94% of the antigen-antibody complex was dissociated, allowing reutilisation. Photobleaching had no effect on the fluorescence. This model system was used to detect Brucella sp. infection and could quantify anti-Brucella sp. antibodies in ovine serum samples in the range from 0.005 to 0.11 mg ml(-1).

Establishment of a time-resolved fluoroimmunoassay for measuring plasma insulin-like growth factor I (IGF-I) in fish: effect of fasting on plasma concentrations and tissue mRNA expression of IGF-I and growth hormone (GH) in channel catfish (Ictalurus punctatus)

A time-resolved fluoroimmunoassay (TR-FIA) was established and validated that allows for the determination of plasma concentrations of insulin-like growth factor I (IGF-I) in three domestically cultured fishes: channel catfish (Ictalurus punctatus), hybrid striped bass (Morone chrysopsxM. saxatilis), and rainbow trout (Oncorhynchus mykiss). Sensitivity of the assay was 0.20 ng/ml. Intra- and inter-assay coefficients of variation (CV) were <7 and <12%, respectively. Serial dilutions of plasma from each species were parallel to the standard curve. Recovery of IGF-I from spiked plasma samples was >90% for all three species of fishes. The IGF-I TR-FIA was biologically validated via its use to determine the effect of fasting on circulating IGF-I levels in channel catfish. Fasting-induced changes in plasma growth hormone (GH), hepatic IGF-I mRNA expression, and pituitary GH mRNA expression were also determined. Fasted channel catfish lost 5.6 and 15.6% body mass after 2 and 4 weeks of fasting, respectively. Plasma IGF-I concentrations were depressed (P<0.05) relative to fed controls following 2 and 4 weeks of fasting. Plasma GH concentrations were not different (P>0.05) in fasted fish after 2 weeks, but significantly increased (P<0.05) by 4 weeks of fasting. Hepatic IGF-I mRNA expression after 2 and 4 weeks of fasting was reduced (P<0.05) relative to fed controls. Pituitary GH mRNA expression was similar (P>0.05) between 2-week-fasted catfish and fed controls, but was increased (P<0.05) in 4-week-fasted catfish. The IGF-I TR-FIA was sensitive, accurate, and precise for all three species of fishes, and provided a low-cost, and non-radioisotopic method for quantifying plasma IGF-I levels in fed and fasted channel catfish.

Use of a time-resolved immunofluorometric assay for determination of canine C-reactive protein concentrations in whole blood

OBJECTIVE

To develop and validate a time-resolved immunofluorometric assay (TR-IFMA) for measurement of C-reactive protein (CRP) in canine whole blood.

ANIMALS

12 healthy dogs and 35 dogs with inflammatory processes.

PROCEDURE

CRP was isolated from acute-phase serum by affinity chromatography and used as a standard for calibration. Analytic and functional limit of detection and intra-assay and interassay precision were calculated. Accuracy was evaluated by recovery assays and by comparison with results of a commercial ELISA. Correlation between CRP concentrations in whole blood and corresponding plasma fractions was tested by use of TR-IFMA. Stability of blood samples at 4 degrees C was assessed during a 1-month period, and effects of anticoagulants were evaluated. Measurements of CRP in blood samples from 12 healthy dogs were compared with those of 35 dogs with inflammatory diseases.

RESULTS

Analytic and functional limits of detection were 0.53 and 3.26 microg/mL, respectively. Intra-assay and interassay coefficients of variation varied between 2.1% to 8.9% and 8.0% to 12.3%, respectively. Mean recoveries of added CRP were 104% and 114%. Measurements of CRP by use of TR-IFMA and ELISA were highly correlated (R2 = 0.97). Measurements of CRP in whole blood and in corresponding plasma fractions by use of TR-IFMA were also highly correlated (R2 = 0.97). Neither storage nor use of anticoagulants disturbed measurement of CRP concentrations in whole blood. Concentrations of CRP in whole blood of dogs with inflammation were significantly higher than in healthy dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Determination of CRP concentrations in whole blood may provide a diagnostic test for inflammation in dogs.

A time-resolved immunofluorometric assay for quantification of collectin-43

CL-43 is a serum collectin involved in the innate immunity of cattle and variability of serum CL-43 may relate to disease in cows. A high capacity time-resolved immunofluorometric assay (TRIFMA) for the bovine collectin-43 (CL-43) was developed. The TRIFMA was constructed as a noncompetitive sandwich based on polyclonal antibodies and a novel monoclonal antibody (mab) raised against CL-43 and was set up to run on an automatic analyser designed for the TRIFMA detection system. The polyclonal antibodies were immobilized on microtiter plate wells and incubated with diluted plasma samples, including quality controls (QC) and dilutions of a plasma with known CL-43 concentration. CL-43 was sandwiched between the capture antibodies and the monoclonal antibody and the detection was optimised with biotin-labelled secondary antibodies and streptavidin-Eu3+. Plates were washed four times between each step and finally incubated with enhancement solution before measuring the fluorescence. The assay detection limit was 0.24 ng/ml and the working range was 0.54-22 ng/ml. Recovery was 92.3% when samples were spiked with 2.0 ng/ml of CL-43. Intraplate and interplate coefficients of variation were in the range of 1.11-2.36% and 0.70-1.35%, respectively. No circadian rhythm (24-h variation) in CL-43 plasma levels was observed, indicating that plasma levels were not influenced by e.g. feeding. Samples could be stored at -20 degrees C and were not sensitive to repeated freezing and thawing. In conclusion, the developed TRIFMA for CL-43 is specific and reliable over a measurement range covering most situations.

Characteristics of oligodeoxyribonucleotides that induce interferon (IFN)-alpha in the pig and the phenotype of the IFN-alpha producing cells

The immunostimulatory effects of oligodeoxyribonucleotides (ODN) containing unmethylated CpG dinucleotides (CpG-ODN) in certain base contexts have been extensively studied in man and mice. One major action is their ability to trigger production of massive amounts of interferon-alpha (IFN-alpha) by plasmacytoid dendritic cells (PDC), also referred to as natural IFN-alpha/beta producing cells (NIPC). The present study using porcine PBMC activated by CpG-ODN or plasmid DNA revealed a considerable variation in the IFN-alpha production in response to various CpG-ODN constructs. Several phosphodiester ODNs, such as 5' TTTTCAATTCGAAGATGAAT 3' (ODN H), and the plasmid pcDNA3 all required pre-incubation with lipofectin in order to induce IFN-alpha. Intact unmethylated CpGs were also important, because methylation or substitution of the cytosines and CpG-inversion strongly reduced the IFN-alpha induction by single- or double-stranded forms of ODN H. Certain CpG-ODNs that contained flanking phosphorothioate or phosphodiester poly-G sequences were potent inducers of IFN-alpha without pre-incubation with lipofectin, for instance the ODN 2216 (5' GGGGGACGATCGTCGGGGGG 3'). While poly-G sequences have been suggested to increase uptake of ODNs by cells, they did not obviate the need for lipofectin when added to the ODN H. However, they resulted in up to five-fold increases of the IFN-alpha levels caused by ODN H upon lipofection, indicating other enhancing effects of poly-G sequences on the induction of IFN-alpha. The identity of the IFN-alpha producing cells (IPC) stimulated by CpG-ODN or plasmid DNA was studied by means of flow cytometry using combined staining for intracellular IFN-alpha and surface markers. Approximately 1-3 IPC/10(3) PBMC were detected, compared to only 3 IPC/10(4) PBMC stimulated by Aujeszky's disease virus. The IPC frequencies were confirmed by detection of IFN-alpha mRNA positive cells by in situ hybridisation. The IPC induced by CpG-ODN or plasmid DNA had a similar phenotype, expressing CD2 and CD4 and intermediate levels of MHC class II and the myeloid marker SWC3, but not the markers of T and B cells or monocytes (CD3, CD21 and CD14). Consequently, porcine IPC that respond to CpG-DNA seem to correspond to the PDC/NIPC.

Prevalence of zeranol, taleranol andFusariumspp. toxins in urine: implications for the control of zeranol abuse in the European Union

There is currently little information concerning the prevalence of zeranol and taleranol in animal urine following metabolism of the naturally occurring Fusarium spp. toxins. An epidemiological study is described which involves four European Union control laboratories in which 8008 urine samples were screened for the presence of zeranol using a time-resolved fluoroimmunoassay (TR-FIA). Of these samples, 93.6% screened negative for zeranol. All samples testing positive for zeranol were then analysed with a confirmatory method. Based on the confirmatory results, the TR-FIA-positive samples were then categorized as false-positive, true-positive or 'equivocal' (zeranol/taleranol and the Fusarium spp. toxins detected). The true-positive samples represented only 0.05% of the total number of samples (n = 4). After statistical analysis, 170 of 174 equivocal samples proved to belong to a 'normal' population in which the amount of zeranol/taleranol could be related to the total amount of Fusarium spp. toxins through a linear regression with a 99% prediction interval. This suggested that the presence of zeranol in these samples might be due to in vivo metabolism of the Fusarium spp. toxins. The presence of zeranol in the four remaining 'outliers' might be attributable to zeranol abuse rather than to natural contamination. The results are of interest for control laboratories as they might provide an analytical tool to help distinguish between abuse and natural contamination in zeranol testing.

A time-resolved immunofluorometric assay for quantification of the bovine collectin conglutinin

A high capacity time-resolved immunofluorometric assay (TRIFMA) for the bovine collectin conglutinin was developed. The TRIFMA was constructed as a non-competitive sandwich assay based on polyclonal antibodies as the capture reagent and a novel monoclonal antibody raised against conglutinin as the detection reagent and was set up to run on an automatic analyzer designed for the TRIFMA detection system. Polyclonal antibodies immobilized on microtiter plate wells were incubated overnight at 4 degrees C with diluted plasma samples, including quality controls (QC) and dilutions of a plasma with known conglutinin concentration. Conglutinin was sandwiched between the capture antibodies and the monoclonal antibody and the detection optimised with biotin-labelled secondary antibodies and streptavidin-Eu(3+). Plates were washed four times between each step and finally incubated with enhancement solution before measuring the fluorescence. The assay detection limit was 0.34 ng/ml and the working range 0.80 ng/ml-0.20 microg/ml. Intra-plate and inter-plate coefficients of variation (CV) were in the range of 5.0-8.3% and 6.2-7.2%, respectively, at concentrations of 3.4 and 150 ng/ml. Recovery was 90.9+/-2.4% and 98.8+/-2.5% when samples were spiked with 20 ng/ml and 100 ng/ml purified bovine conglutinin (BK). No circadian rhythm (24-h variation) in conglutinin plasma levels was observed across animals, indicating that the plasma levels were not influenced by, e.g. feeding. Samples could be stored at -20 degrees Celsius and were not sensitive to repeated freezing and thawing. In conclusion, the developed TRIFMA for bovine conglutinin is specific and reliable over a measurement range covering most situations.

Technical note: time-resolved immunofluorometric assay for growth hormone in ruminants

A noncompetitive, time-resolved immunofluorometric assay (TRIFMA) was developed using a selected pair of monoclonal antibodies (mab) raised against recombinant bovine GH, with the catching mab immobilized on microtiter plate wells and the detection mab labeled with Eu3+ as a tracer, arranged as a sandwich. Plates were coated with mab1.15 (680 ng/well) using a phosphate buffer (pH 4.9), and then blocked with assay buffer containing 1% (wt/vol) BSA. The assay procedure involved incubation of 50 microL of sample (plasma or serum) and 200 microL of assay buffer containing 25 ng of mab1.2-Eu3+ conjugate for 4 h at 25 degrees C. Plates were then washed six times, incubated for 5 to 10 min with 250 microL of enhancement solution, and fluorescence read with a time-resolved fluorometer. The sensitivity of the assay was 0.1 ng/mL, and the working range was 0.2 to 200 ng/mL. Recovery of quantitative amounts of bovine GH added to plasma samples was close to 100%. Cross-reactivity with other bovine pituitary hormones or with GH from nonbovidae or cervidae species was not significant. Intra- and interassay CV during routine operation was 4.4 and 10.7%, respectively (mean = 3.54 ng/mL). Plasma concentrations of bovine GH determined by TRIFMA correlated closely (r2 > or = 0.93) with RIA results, with a conversion ratio of 0.62 when the higher specificity of the monoclonal antibodies was taken into account. The TRIFMA is a reliable alternative to RIA methods because the assay employs no radiolabeled or hazardous chemicals, delivers results rapidly, and has little risk of down periods.

Development and validation of dry reagent time-resolved fluoroimmunoassays for zeranol and alpha-zearalenol to assist in distinguishing zeranol abuse from Fusarium spp. toxin contamination in bovine urine

Zeranol, an oestrogenic growth promoter in food animals, is banned within the European Union (EU). However, commercially available immunoassay kits for zeranol cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the validation of a specificity enhanced, rapid dry reagent time-resolved fluoroimmunoassay (TR-FIA) for zeranol (recovery 99%, limit of detection 1.3 ng ml(-1)) demonstrating that up to 150 ng ml(-1) of Fusarium spp. toxins in urine do not lead to false-positive results. This assay will assist EU Member States to implement Council Directive 96/23/EC, which requires states to monitor for potential abuses of zeranol. A similar TR-FIA for the Fusarium spp. toxin alpha-zearalenol, using the same sample extract, is also described (recovery 68%, limit of detection 5.6 ng ml(-1)). Only the addition of diluted sample extract is required to perform these dry-reagent TRFIAs, the results being available within 1h of extract application. The EU-funded project 'Natural Zeranol' (FAIR5-CT97-3443) will use these fluoroimmunoassays to screen bovine urine in four Member States to gather data on the seasonality of Fusarium spp. toxin contamination of urine and the incidence of zeranol screening test positives.

Technical note: time-resolved fluoro-immunometric assay for intact insulin in livestock species

Insulin levels in ruminants are often very low and hence are difficult to measure with commercially available RIA kits designed for use with human serum or plasma samples. Those assays may also have high cross-reactivity with nonintact insulin. An assay originally invented for human insulin and based on a pair of monoclonal antibodies binding to specific parts of the insulin molecule was further developed and validated for use with bovine or porcine plasma or serum. The assay is of the sandwich type, with the catching antibody coated to the solid phase of microtiter plate wells and with the detecting antibody labeled with europium, and measured as time-delayed fluorescence. The assay protocol includes an incubation step in which plasma samples of 50 microL are incubated with buffer and detecting antibody for 3 h in coated wells, followed by an enhancement step in which the fluorescence from the europium label is stabilized before measurement. This gives a sensitivity of 3 pmol/L and a possible working range up 16,700 pmol/L. There is no cross-reactivity with pro-insulin or IGF-I. Calibrators are prepared in heat-inactivated serum from the relevant species. Porcine and bovine insulin have different calibration curves; porcine insulin is more reactive and has a higher background than bovine insulin. Validation results show low CV values, parallel dilution of samples, and a recovery ratio close to unity. Comparison with a commercial RIA shows good agreement, except at low concentrations, at which the RIA determinations are inaccurate. Plasma samples from other domestic species (horse, sheep, goat, and mink) have also been assayed, but it is emphasized that calibrators should be prepared in heat-inactivated serum from the appropriate species, and preferably insulin from that species should be used for calibration.

The measurement of prion protein in bovine brain tissue using differential extraction and DELFIA as a diagnostic test for BSE

A simple diagnostic test for the detection of bovine spongiform encephalopathy (BSE), based on a commercially available time-resolved fluorescence immunoassay (DELFIA) for the measurement of the normal and disease-associated isoforms of prion protein (PrP), is described. The isoforms are sequentially extracted from homogenized bovine brain tissue using two concentrations of guanidine hydrochloride. This procedure initially extracts a soluble isoform and subsequently a less soluble disease-associated aggregated isoform. Following quantification of the two fractions, the percentage of the insoluble prion becomes a measurable parameter, independent of protein concentration, clearly identifying normal from infected animals displaying clinical signs of BSE. The mean percentages of insoluble PrP in brain tissue from 60 BSE-confirmed-positive cattle and 100 cattle that had never been exposed to the disease were 52.6% (SD = 22.8) and 3.9% (SD = 1.5), respectively. The assay is sensitive, with a detection limit of less than 50 pg PrP, and is robust and precise (CVs < 10%) over the appropriate working range.

Cats surviving natural infection with Cytauxzoon felis: 18 cases (1997-1998)

Eighteen cats surviving natural infection with Cytauxzoon felis were identified. All cats came from a limited geographic area in northwestern Arkansas and northeastern Oklahoma. Clinical signs in most cats were similar to those described for cytauxzoonosis; however, 4 cats were asymptomatic. All cases were initially diagnosed by microscopic identification of signet ring-shaped piroplasms in erythrocytes of peripheral blood smears. Four of 4 cats tested had detectable serum antibodies to C felis. Four different cats were positive by polymerase chain reaction (PCR). Partial sequencing of the PCR product from 1 cat revealed >99% homology with the reported sequence of C felis. Repeated examination of blood smears from 12 cats revealed that the erythroparasitemia was generally persistent for the duration of follow-up (3-154 days). Survival did not seem dependent on treatment, as only 1 cat was treated with a drug with potential antiprotozoal activity (imidocarb dipropionate), and 4 cats received no treatment. The findings of this study may indicate the existence of a less virulent strain of C felis.

Relationship among estradiol, cortisol and intensity of estrous behavior in dairy cattle

Economic profitability of a dairy farm is based, in part, on the calving interval of the cows. The optimal interval is 365 d. To achieve this, the cow needs to be pregnant within 85 d post partum. The first and most problematic step in this process is the determination of the optimal time for insemination, which is based on estrous behavior. The expression of estrous behavior, however, is at a low level in modem dairy herds, resulting in low detection rates and longer calving intervals. In the present study, a point scale was used to monitor postpartum, nonpregnant cows for estrous symptoms. Frequent blood samples were taken around estrus, and the cows were fit with pedometers to measure their activity. Correlations between the occurrence of symptoms of estrus and levels of estradiol and cortisol were then analyzed. Standing heat, the standard symptom of estrus, was observed in only 53% of the cows. A high correlation of 0.7 was found between estradiol concentration and estrous behavior. This was empasized by the fact that the estradiol level reached its highest level of 7.76 + 2.39 (SD) pg/mL at the same time as the highest behavior score. The highest pedometer readout lagged 8 h behind this moment. Cortisol levels did not exceed the physiological levels in rest situations but showed an increase at the time estrous behavior was at its maximum. The present study showed that standing heat is not the primary symptom for detecting estrus in cows. Pedometers are a useful aid but they have to be read several times a day. The high correlation between the visual symptoms of estrus and estradiol concentrations indicates that visual estrus detection is an efficient, reliable way to determine the right time for insemination.

Epidermal lesions and mortality caused by vibriosis in deep-sea Bahamian echinoids: a laboratory study

When significant mortality of the bathyal spatangoid echinoid Paleopneustes cristatus occurred under laboratory conditions, we investigated the cause and course of the disease by culturing and identifying internal pathogens, then experimentally infecting healthy urchins with isolates of the suspected disease organism. The pathogen was determined to be the gram-negative halophilic bacterium Vibrio alginolyticus. This species was also recovered from frozen post-challenge specimens of P. cristatus and from moribund individuals of Archaeopneustes hystrix, another spatangoid reared under similar in vitro conditions. This is the first experimental study of bacterial disease in any deep-sea invertebrate.

Time-resolved fluoroimmunoassay (TR-FIA) of porcine relaxin

We developed and validated a new assay system for porcine relaxin that overcame the drawbacks of RIA by adapting time-resolved fluoroimmunoassay (TR-FIA), which was recently introduced as a non-RIA format. The assay system was a solid-phase TR-FIA based on competition for a polyclonal anti-porcine relaxin antibody between europium (Eu)-labeled porcine relaxin and test samples. Antibody-relaxin complexes were then bound to the second antibody coated on the solid phase, achieving rapid and complete separation of bound and free antigen. A standard curve was produced over the range of 1 pg/well to 1000 pg/well. Serum and corpus luteum extracts from pigs in late pregnancy exhibited inhibition curves parallel to that of the relaxin standard, whereas male pig serum caused no displacement of the labeled hormone. No cross-reactivity was seen with other hormones, such as insulin, LH, and FSH, indicating a high specificity of the assay. The sensitivity was 4 pg/well (80 pg/ml), which was high and equivalent to that of the porcine relaxin RIA. The intra-assay and inter-assay coefficients of variation were less than 3.8% and 6.7%, respectively. Recovery of porcine relaxin added to male pig serum sample averaged 103%. The advantages of this TR-FIA were that addition of tyrosine was not necessary for labeling, unlike the RIA, Eu-labeled relaxin was stable enough to allow long-term storage for more than one year, the assay was completed in only 5 h versus two to seven days for the RIA, and no special safety precautions were needed. To validate this TR-FIA, the serum relaxin concentrations during late pregnancy, parturition and early lactation were investigated in pigs. Serum relaxin levels determined by this assay were similar to those obtained previously by RIA. In conclusion, this TR-FIA could replace RIA as the method of choice for assay of relaxin.

Reproductive disturbance caused by an S-triazine herbicide in pigs

The aim of the study was to assess the effect of subacute treatment with a low dose of atrazine (1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methyl-ethyl), an s-triazine herbicide, on endocrine oestrus regulation in gilts. A group of nine gilts (F1 generation of Swedish Landrace x Large Yorkshire) were treated with 1 mg atrazine/kg body mass daily, mixed to the feed for 19 days before the onset of expected oestrus. Blood samples were obtained by cranial vena cava puncture three times daily at 3-h intervals on five post-treatment days, i.e. before and during oestrus. The serum concentration of oestradiol-17 beta (E2) was determined by the fluoroimmunochemical method. On Day -2 before the onset of expected oestrus, a significantly lower (P < 0.001) E2 concentration was measured in the serum of treated gilts (31.25 +/- 1.95 and 39.32 +/- 1.38 pg/mL) than in the control pigs (51.43 +/- 1.29 and 68.59 +/- 2.99 pg/mL). In contrast, the E2 concentration measured in the serum of treated animals was significantly higher (P < 0.001) on the day of the expected onset of oestrus and on the subsequent two days (35.43 +/- 1.85, 53.92 +/- 1.98 and 60.32 +/- 2.35 pg/mL, respectively) than in the control animals (13.52 +/- 1.79, 21.53 +/- 1.35 and 20.05 +/- 1.46 pg/mL, respectively). Insufficient serum E2 concentration of the treated gilts resulted in a failure of expected oestrus, as indicated also by the state of dioestrus demonstrated by histopathological examination of the uterus.

Effects of repeated jugular puncture on plasma cortisol concentrations in loose-housed dairy cows

In three experiments, the effects of venipuncture on plasma cortisol concentrations were studied in loose-housed dairy cows. In Exp. 1, two blood samples were collected 18 min apart on three alternate days from 20 dairy cows for studying their adrenocortical response to a single venipuncture. To further evaluate the effect of cows anticipating venipuncture, in Exp. 2, 15 dairy cows were sequentially venipunctured once daily on 12 successive days in a randomized order in groups of five, starting 15 min apart. In Exp. 3, 10 primiparous cows were used on three alternate days to study habituation to serial sampling (i.e., collection of five blood samples by venipuncture, 15 min apart). In cows accustomed to handling, jugular puncture did not affect cortisol concentrations in plasma collected 18 min later. Average daily cortisol concentrations varied between 2.07 +/- .38 and 3.81 +/- .56 ng/mL in the first (t = 0) and between 1.43 +/- .15 and 2.61 +/- .72 ng/mL in the second (t = 18) blood samples. Likewise, when cows were sampled sequentially once a day, the order of sampling between and within groups did not influence (P > .05) plasma cortisol concentrations. In contrast, primiparous dairy cows that were less used to being handled showed an average increase in cortisol concentrations when five samples were collected by venipuncture 15 min apart. During successive sampling sessions, however, the cows did not decrease or increase plasma cortisol concentrations in response to repeated serial sampling at the group level (P > .05). Between individuals, the maximum effect of repeated venipuncture on cortisol concentrations (4.5 to 22.6 ng/mL), the time at which the effect reached its maximum (30 to 60 min), and the consistency of the response pattern over successive series varied largely. The results of this study show that in cows that were accustomed to handling and to being restrained, baseline cortisol concentrations can be measured in single blood samples that are collected by jugular puncture within 1 min after first approaching the cow. When successive blood samples need to be collected within 15 to 20 min, jugular puncture may induce an increase in cortisol concentration, which seems to depend on the handling experience of the animals and on individual differences.

Downregulation of a protective Actinobacillus pleuropneumoniae antigen during the course of infection

The persistence of Actinobacillus pleuropneumoniae in convalescent pigs significantly contributes to the distribution of disease. The downregulation of protective antigens in vivo as one possible mechanism responsible for this phenomenon was investigated using the small iron-regulated transferrin binding protein (TbpB-protein) as exemplary protective antigen. From a total of 21 pigs experimentally infected with A. pleuropneumoniae serotype 7 in three trials, bronchoalveolar lavage fluid (BALF) was obtained on day 1 or 2, day 7, day 14 and day 21. Employing double immunofluorescence of BALF with a monoclonal anti-TbpB antibody and an A. pleuropneumoniae -specific anti-polysaccharide antiserum a statistically significant decrease of the percentage of A. pleuropneumoniae bacteria strongly expressing TbpB protein was observed during the course of infection. These results were supported by in vitro incubation of A. pleuropneumoniae in medium supplemented with BALF. In addition, it was found that TbpB-expression in BALF from day 7 after infection could not be inhibited by the substitution of iron. These results suggest (i) the downregulation of protective antigens is one possible mechanism allowing bacterial persistence, (ii) in vitro induction in the presence of BALF mimics the in vivo situation, and (iii) TbpB expression is additionally regulated by an iron-independent mechanism.

Establishing albumin levels in sheep serum by a specific fluoroimmunoassay

A rapid and sensitive fluoroimmunoassay (FIA) was developed to measure albumin levels in sheep serum. The assay employed ovine albumin labelled with fluorescein as the tracer and a rabbit antiserum raised against sheep albumin. Separation of antibody-bound from free albumin was achieved using a second antiserum directed against the Fc component of rabbit IgG. Assay procedures were simplified by mixing the two antisera prior to use. Satisfactory assay validation parameters were demonstrated and the reagents were stable for at least 1 year at 4 degrees C. In contrast to the bromocresol green dye binding method, the accuracy of the FIA was unaffected by contaminating immunoglobulins. The FIA was used to establish reference ranges for serum albumin levels in lambs, in normal ewes and in ewes undergoing a prolonged course of immunisation. Mean serum albumin levels for these three groups were 38.8, 51.3 and 37.8 gL-1 respectively. The sensitivity of the assay makes it suitable to monitor albumin levels in therapeutic products derived from sheep blood or serum.

Actinobacillus pleuropneumonia serotype 2--effects on the interferon-alpha production of porcine leukocytes in vivo and in vitro

Effects of a bacterial infection on the IFN-alpha production in vivo and in vitro were studied in eight specific pathogen free pigs experimentally infected with Actinobacillus pleuropneumoniae. Clinically, the experimental infection was manifested as a febrile stage which lasted approximately one week and by signs of respiratory disease. The Aujeszky's disease virus (ADV) induced IFN-alpha production, assessed in whole blood cultures, was increased for the infected pigs during the febrile stage. Potentiating effects on the IFN-alpha production could be transferred to cultures of purified peripheral blood mononuclear cells with sera collected from the infected pigs during this period of time. Although the experimental infection with A. pleuropneumoniae did not induce any detectable amounts of IFN-alpha in serum or nasal secretion, both a phenol-extract and a heat-inactivated preparation of the bacteria induced low levels of IFN-alpha in cultures of purified PBMC. The interferogenic structures of the bacteria were not identified but there were indications that the bacteria induced IFN-alpha production in the same cell type as ADV.

Development of a specific fluoroimmunoassay for ovine albumin

A fluoroimmunoassay has been developed to measure serum levels of albumin in sheep. It employs ovine albumin labelled with fluorescein as the tracer and a rabbit antiserum raised against ovine albumin. Separation of the antibody bound and free fractions is achieved using a second antiserum directed against the Fc of rabbit immunoglobulin G and, to simplify the assay, the two antisera are premixed prior to use. Assay validation parameters are satisfactory and the reagents are predicted to be stable for at least one year at 4 degrees C. In contrast to the bromocresol green method, the assay is unaffected by immunoglobulins. A reference range for serum albumin levels has been established in lambs, normal ewes and ewes undergoing immunisation. Mean serum levels were 38.8, 51.3 and 37.8 g/l respectively. The sensitivity of the assay also enabled its use to monitor albumin levels at various stages during the production of specific antibody fragments from ovine antisera for therapeutic purposes.

Effect of drug formulation and feeding on the pharmacokinetics of orally administered quinidine in the horse

Quinidine is the drug of choice for the treatment of cardiac arrhythmias in horses. The plasma concentrations vs. time profiles following oral administration of two formulations of quinidine sulphate, an oral solution and an oral suspension paste, were evaluated in nine horses. They received multiple administrations of the oral solution under fed and non-fed conditions and of the paste under non-fed conditions. A loading dose of 20 mg.kg-1 and a maintenance dose of 10 mg.kg-1 quinidine with dosing interval of 6 h were used. The relative bioavailability of the oral solution under fed conditions in comparison to the solution under non-fed conditions was 75.0 +/- 10.2% for the loading dose and 97.18 +/- 31.66% after the fourth dose. For the paste formulation the relative bioavailability values are not reported, as steady-state levels were not reached. There was a large variation in plasma quinidine levels when the paste formulation was administered. Feeding conditions had a significant influence on the Cmax values after administration of the loading dose. The Tmax values were not affected by food intake. It was concluded that an oral solution has to be preferred because of the variable drug bioavailability from the paste formulation and the poor acceptability of the paste by the horse.

Comparison of particle concentration fluorescence immunoassay to card and complement fixation tests using isolation of Brucella abortus as the standard

Serologic test data and bacteriologic culture results from 816 cattle were evaluated. Brucella abortus (field strain or strain 19) was isolated from 27.3% of the cows. Results of the card test, particle concentration fluorescence immunoassay (PCFIA), and complement fixation (CF) test were compared. Antibody titers were directly associated with B. abortus isolation, with the majority (64.7%) of field strain isolations having a PCFIA value of < or = 0.300 and a CF test result of at least 1+ at a 1:160 dilution. The specificity of the CF test was significantly higher than that of the PCFIA (at CF > or = 1:40 and PCFIA < or = 0.300).

Serodiagnosis of canine visceral leishmaniasis in Portugal: comparison of three methods

Sera collected in Portugal from 43 dogs were screened for specific antibodies to Leishmania donovani antigens. Three different techniques were compared: an indirect immunofluorescence assay (IFA), a direct enzyme-linked immunosorbent assay (ELISA) and a competitive-ELISA (C-ELISA) using two species-specific monoclonal antibodies, D2 and D13. By IFA, 22 of the sera examined showed positive reactions, compared with 26 by ELISA or 27 by C-ELISA. There was no direct correlation observed between the serum titre by IFA and the strength of the reaction in ELISA or inhibition in C-ELISA. However, a good correlation was observed between sera identified as positive (95.5%) by all three techniques. Western blotting on leishmanial membranes showed that common antigens with Mr of 26,000 and 70-84,000 were recognized by all infected dog sera, regardless of the serum titre. In large scale studies, ELISAs are preferred to IFA for the rapid diagnosis of canine visceral leishmaniasis because of their greater simplicity.

Changes in lymphocyte blastogenic response of mares during the perinatal period

A fluorometric assay was applied to evaluate blastogenesis of equine lymphocytes. Optimal culture conditions were as follows; concentrations of phytohaemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were 1 microgram/ml, 40 micrograms/ml and 10 micrograms/ml, respectively, when 5 X 10(5) lymphocytes were incubated with culture medium containing 20% pooled horse serum (PHS) for 120 hours. The relative mean stimulation index of healthy non-pregnant mares were 5.107 +/- 0.323 (M +/- SE) with PHA, 4.019 +/- 0.183 with Con A and 3.610 +/- 0.131 with PWM. Sequentially the blastogenic responses of lymphocytes from twenty mares were observed during various stages of the perinatal period. Response decreased gradually before parturition was lowest at the time of parturition (PHA: 1.923 +/- 0.174, Con A: 1.698 +/- 0.206 and PWM: 1.706 +/- 0.177), and then increased gradually after parturition towards non-pregnant levels.