Simplified microELISA for the quantitation of murine serum amyloid A protein

Protective effects of alpha1-acid glycoprotein and serum amyloid A on concanavalin A-induced liver failure via interleukin-6 induction by ME3738

We examined whether the 22beta-methoxyolean-12-ene-3beta,24(4beta)-diol (ME3738)-mediated selective induction of interleukin-6 increased alpha1-acid glycoprotein and serum amyloid A expression, and whether these proteins protected against liver injury in vitro and in vivo. ME3738 treatment in male mice increased gene expression of alpha1-acid glycoprotein subtypes and serum amyloid A 2 genes, and plasma concentration of serum amyloid A. Treatment with alpha1-acid glycoprotein at 5 mg/animal or serum amyloid A at 0.03 and 0.1 mg/animal prior to concanavalin A administration reduced multifocal necrosis in the liver. Treatment with alpha1-acid glycoprotein and serum amyloid A, but not alpha1-antitrypsin, protected Hep G2 cells against cell injury. These results suggest that alpha1-acid glycoprotein and serum amyloid A, increased by ME3738-induced interleukin-6, might protect against concanavalin A-induced liver injury.

Enhancement of AA-amyloid formation in mice by transthyretin amyloid fragments and polyethylene glycol

The mechanism behind amyloid formation is unknown in all types of amyloidosis. Several substances can enhance amyloid formation in animal experiments. To induce secondary systemic amyloid (AA-type amyloid) formation, we injected silver nitrate into mice together with either amyloid fibrils obtained from patients with familial polyneuropathy (FAP) type I or polyethylene glycol (PEG). Mice injected with silver nitrate only served as controls. Amyloid deposits were detectable at day 3 in animals injected with amyloid fibrils and in those injected with PEG, whereas in control mice, deposits were not noted before day 12. Our results indicate that amyloid fibrils from FAP patients and even a non-sulfate containing polysaccharide (PEG) have the potential to act as amyloid-enhancing factors.

Monoclonal antibody-based sensitive enzyme-linked immunosorbent assay for murine serum amyloid A

Enzyme-linked immunosorbent assay (ELISA) methods for measuring murine serum amyloid A (SAA), a representative acute phase reactant, were developed utilizing a newly produced monoclonal antibody. Two site-ELISA, in which the monoclonal antibody was used as the captured antibody, was sensitive enough to determine the SAA concentration in mice at the steady state. Direct binding ELISA, in which the sample SAA bound to the plastic wells was detected by the antibody, was simple and suitable for measuring the elevated SAA, but could not analyze the resting level of SAA because of the need for high dilution in plasma samples. Plasma SAA concentrations were measured in ten ICR mice on the day of purchase and at the end of seven days of ordinary rearing. The SAA concentration of one animal decreased from 1.6 to 0.5 mg/l during a week, while the others had no obvious changes. The plasma SAA of the ten animals after one week of rearing ranged from 0.3 to 0.8 mg/l with a mean of 0.47. These mice, two days after 10 microg lipopolysaccharide were given, had increased SAA values up to a mean of 300 mg/l, though with variations between animals.

Serum copper/zinc superoxide dismutase levels in patients with rheumatoid arthritis

Rheumatoid arthritis is characterized by a chronic hypertrophic synovitis leading to destruction of connective tissue and functional damage of cartilage and bone structures. Reactive oxygen species play an important role in tissue injury in this disease. To clarify the role of the cellular antioxidant system in the protection against oxygen free radicals, we examined the levels of copper/zinc superoxide dismutase in the sera of patients with rheumatoid arthritis. We used an enzyme-linked immunosorbent assay which determines the concentration of copper/zinc superoxide dismutase independently from its enzymatic activity. We found that patients with rheumatoid arthritis have higher serum copper/zinc superoxide dismutase levels than control subjects. Copper/zinc superoxide dismutase also correlated positively with serum levels of both neopterin and rheumatoid factor, sensitive markers for disease activity in rheumatoid arthritis. These results support the hypothesis that the increased amount of copper/zinc superoxide dismutase is probably inadequate to exert an effective antioxidant protection but can result in a pro-inflammatory, pathogenic effect enhancing tissue damage. Furthermore, copper/zinc superoxide dismutase might be used as a marker of inflammatory activity in rheumatoid arthritis.

A rapid enzyme-linked immunosorbent assay for serum amyloid A using sequence-specific antibodies

A microtitre plate based enzyme-linked immunosorbent assay for determining the concentration of serum amyloid A (SAA) is described. The method employs easily produced sequence-specific rabbit antibodies and the preferential absorption of SAA to polystyrene, which obviates the use of capture antibodies and allows an assay time of only 3.5 h, so that the diagnostic potential of the SAA level as a rapid and reliable marker for inflammation can be fully exploited. The assay has a working concentration range of 0.1-2500 mg/L, which embraces the known biological variation of the SAA concentration. The intra-assay coefficient of variation (CV) for SAA concentrations above 10 mg/L is between 1.6 and 3.3% and the interassay CV between 3.0 and 4.2%. Recovery of SAA added to serum is from 96 to 102%.

Serum markers of immune activation and liver allograft rejection

We monitored the immune response after liver transplantation in 20 patients by measuring the serum levels of soluble interleukin-2 receptor (sIL-2R), soluble CD8 (sCD8), serum amyloid-A protein (SAA), and tumor necrosis factor-alpha (TNF-alpha). In six patients data were available to extend the follow-up period to one year. In all patients mean sIL-2R levels increased in the first month after liver transplantation, and subsequently decreased to values similar to pre-OLT ones, while SAA mean levels rose in the first week after OLT only in patients with rejection. sCD8 levels did not significantly rise after OLT, and TNF-alpha was undetectable in most cases. During episodes of rejection, rejector patients had significantly higher levels of sIL-2R, sCD8, and SAA than stable (without complications) patients. Conversely, no significant difference between rejectors and patients with other complications existed for any of the markers studied. These results diminish the importance of these serum markers of immune activation as laboratory tools in the differential diagnosis of acute rejection from other complications. However, sIL-2R, SAA, and sCD8 levels correlated with the histological grade of rejection and therefore can be utilized to monitor patients with an established diagnosis of acute rejection.

Ubiquitin: its potential significance in murine AA amyloidogenesis

Amyloid enhancing factor (AEF), which has recently been shown to have identity with ubiquitin (Ub), is believed to play a causative role in experimentally induced AA amyloidosis in mice. We have examined the profile of Ub in activated leukocytes and splenic reticulo-endothelial (RE) cells and its relationship with serum amyloid A protein (SAA) and AA amyloid deposits in an alveolar hydatid cyst (AHC)-infected mouse model of AA amyloidosis. Two monospecific antibodies, anti-ubiquitin (RABU) and anti-mouse AA amyloid, were used as immunological probes to localize Ub, SAA, and AA amyloid. In response to AHC infection, the dull and diffuse Ub immunoreactivity in normal mouse leukocytes and RE cells promptly changed to a discrete granular pattern suggesting an increase in the intracellular concentration of Ub and the formation of Ub-protein conjugates. This corresponded to an elevation in SAA levels, SAA uptake by RABU-positive phagocytic cells, co-localization of Ub-SAA immunoreactive splenocytes in the perifollicular areas, and deposition of Ub-bound AA amyloid in the splenic and hepatic tissues. These results suggest that Ub-loaded monocytoid cells may play an important role in the physiological processing of the sequestered SAA into AA amyloid. Aspects of AA amyloidogenesis are discussed in relation to other experimental models in which stress-induced Ub-protein conjugate formation and its transport to lysosomal vesicles have been studied.

Serum amyloid A protein concentration in bone marrow transplantation for beta thalassaemia

AIMS

To investigate whether serum amyloid A protein (SAA) and C-reactive protein (CRP) concentrations could be used in the management of beta thalassaemic patients undergoing bone marrow transplantation (BMT).

METHODS

Serum SAA and CRP concentrations were determined in paired samples from 66 patients with beta thalassaemia before and after BMT. Serum SAA concentrations were determined by an enzyme linked immunoassay (EIA); serum CRP concentrations were determined by a nephelometric assay.

RESULTS

Serum SAA concentrations before transplantation were significantly higher in the group that subsequently rejected the transplant than the group without complications. SAA concentrations increased after BMT in acute graft versus host disease (GvHD) and rejection. No significant increase in SAA or CRP was found in chronic GvHD. Increases in serum in SAA and CRP concentrations were not related to concomitant infection episodes.

CONCLUSIONS

The different acute phase response in acute GvHD and rejection compared with chronic GvHD suggests that different immunopathogenic mechanisms are responsible.

Amyloid enhancing factor activity is associated with ubiquitin

Crude amyloid enhancing factor (AEF) drastically reduces the pre-amyloid phase on passive transfer and induces amyloid deposition in the recipient mice in 48-120 h. We attempted to purify AEF from murine amyloidotic liver and spleen extracts by using gel filtration, preparative sodium dodecyl sulphate-polyacrylamide gel electrophoresis and ion exchange chromatography and isolated a 5.5 kDa peptide. In the mouse bioassay, this peptide induced accelerated splenic AA deposition in a dose-dependent manner. Based on structural, electrophoretic and immunochemical criteria the peptide was identified as ubiquitin. A polyclonal rabbit anti-bovine ubiquitin IgG antibody (RABU) abolished the in vivo AEF activity of crude murine AEF in a dose-dependent manner. Monomeric ubiquitin and its large molecular weight adducts were isolated from crude AEF using cyanogen bromide-activated sepharose conjugated to RABU and size exclusion chromatography methods. These were assayed and were found to possess AEF activity. Furthermore, increased levels of ubiquitin, a phenomenon similar to that of AEF, were detected by immunocytochemistry in mouse peritoneal leucocytes prior to and during amyloid deposition. Since AEF shares a number of biological and functional properties with ubiquitin, we suggest a possible role of ubiquitin as an AEF, and that serum amyloid protein A and ubiquitin, the two reactants generated during inflammatory stress conditions, may converge to induce AA amyloid deposition.

Failure of adrenocorticotrophic hormone to release serum amyloid A in cattle

The objective of this study was to determine whether adrenocorticotrophic hormone plays a direct role in the secretion of serum amyloid A (SAA) in cattle. Seven lactating Holstein-Friesian cows were given either saline or 25 iu adrenocorticotrophic hormone (ACTH) intravenously at 09.00 in a two factor crossover design. Plasma cortisol concentrations had increased significantly by one hour after the injection of ACTH, whereas the SAA level had not increased by 24 hours after injection. It is concluded that in cattle adrenocorticotrophic hormone has no direct influence on the release of SAA by the hepatocyte.

A monoclonal antibody sandwich immunoassay for serum amyloid A (SAA) protein

An antibody sandwich immunoassay using two purified rat monoclonal antibodies to human serum amyloid A was developed and used to measure serum amyloid A in human serum. The assay was specific, sensitive, reproducible, and reliable and does not require denaturation of the specimen prior to assay. Serum amyloid A purified by hydrophobic interaction chromatography of acute phase human serum afforded a reliable standard for the assay. A significant (r = 0.69) correlation for SAA and C reactive protein values was found for 180 patient samples analyzed.

Direct binding enzyme-linked immunosorbent assay (ELISA) for serum amyloid A (SAA)

A solid-phase, direct binding ELISA for serum amyloid A (SAA) proteins is described, in which noncovalent interactions of SAA with other plasma constituents are disrupted to permit direct coating of the wells of flexible polyvinyl chloride microtitration plates with an amount of SAA antigen proportional to its concentration in plasma. The wells are coated overnight at 60 degrees C with plasma diluted in 3 M potassium bromide and 0.1 M sodium bicarbonate. pH 9.6. The next day, any remaining sites on the wells are blocked by incubation for 1 h at ambient temperature with a 5% solution of dry milk solids and 0.05% Tween 20 in 0.02 M phosphate buffer, pH 7.4. The wells are rinsed and incubated for 90 min at 37 degrees C with polyclonal rabbit or rat anti-human SAA antiserum. Then, the wells are rinsed and incubated with goat anti-rabbit or rat IgG antiserum to which has been conjugated horseradish peroxidase. o-phenylenediamine and hydrogen peroxide substrates are added to the wells, color is allowed to develop, and sulfuric acid is added to stop the enzyme-catalyzed reaction. The amount of SAA coated to wells is quantified by absorbance at 490 nm. Four or more serial three-fold dilutions of plasma samples are assayed simultaneously on separate plates. Each plate contains a set of wells with identical concentrations of SAA standard protein diluted in decreasing concentrations of plasma proteins corresponding to the dilution of sample. The method can detect SAA concentrations in plasma samples ranging from 1 microgram/ml to greater than 1000 micrograms/ml. The method is suited to serial monitoring of SAA concentration in patients undergoing treatment for inflammatory conditions and to the quantitative analysis of large numbers of samples.

Purification of mouse haptoglobin by antibody affinity chromatography and development of an ELISA to measure serum haptoglobin levels

Mouse haptoglobin was isolated from acute-phase serum initially by affinity chromatography on haemoglobin-Sepharose. This proved inefficient, but sufficient material was obtained for use as an immunogen. Rabbit anti-haptoglobin antibodies were used as immunoabsorbents to isolate larger quantities of haptoglobin. Subsequently, specific anti-haptoglobin antibodies were prepared by affinity chromatography on haptoglobin-Sepharose. A direct sandwich ELISA for mouse serum haptoglobin was developed, using affinity purified reagents. The working range of the haptoglobin standard curve was 0.02-0.5 microgram/ml. The reagents did not cross-react with albumin or haemoglobin and the antibody also recognised rat haptoglobin.