Specific localization and imaging of amyloid deposits in vivo using 123I-labeled serum amyloid P component

Diagnostic performance of liver stiffness as marker of liver involvement in systemic immunoglobulin light chain (AL) amyloidosis

OBJECTIVE

To investigate the diagnostic performance of liver stiffness for detecting liver involvement in immunoglobulin light chain (AL) amyloidosis.

METHODS

Liver stiffness was measured using transient elastography in 71 patients with systemic AL amyloidosis and 18 patients with wild type transthyretin (ATTRwt) amyloidosis with cardiomyopathy. Both non-invasive consensus criteria and serum amyloid P component (SAP) scintigraphy were used as substitute standards instead of liver biopsy for establishing liver involvement.

RESULTS

Liver stiffness was higher in AL amyloidosis patients with liver involvement than in those without: this was observed using both consensus criteria (median 14.4 kPa vs. 8.1 kPa; p = 0.001) and SAP scintigraphy (median 20.9 kPa vs. 6.2 kPa; p < 0.001). Liver stiffness was also higher in AL amyloidosis patients with liver involvement compared to AL and ATTRwt amyloidosis patients with cardiac involvement. Based on receiver operating characteristic (ROC) curves a cut-off value of 14.4 kPa for stiffness was optimal to indicate liver involvement, providing sensitivity and specificity of 50% and 74%, respectively, using the consensus criteria and 63% and 90%, respectively, using SAP scintigraphy as standard.

CONCLUSION

Liver stiffness is a promising tool to establish liver involvement in AL amyloidosis having potential to become part of updated criteria for liver involvement.

Structurally Altered, Not Wild-Type, Pentameric C-Reactive Protein Inhibits Formation of Amyloid-β Fibrils

The structure of wild-type pentameric C-reactive protein (CRP) is stabilized by two calcium ions that are required for the binding of CRP to its ligand phosphocholine. CRP in its structurally altered pentameric conformations also binds to proteins that are denatured and aggregated by immobilization on microtiter plates; however, the identity of the ligand on immobilized proteins remains unknown. We tested the hypotheses that immobilization of proteins generated an amyloid-like structure and that amyloid-like structure was the ligand for structurally altered pentameric CRP. We found that the Abs to amyloid-β peptide 1-42 (Aβ) reacted with immobilized proteins, indicating that some immobilized proteins express an Aβ epitope. Accordingly, four different CRP mutants capable of binding to immobilized proteins were constructed, and their binding to fluid-phase Aβ was determined. All CRP mutants bound to fluid-phase Aβ, suggesting that Aβ is a ligand for structurally altered pentameric CRP. In addition, the interaction between CRP mutants and Aβ prevented the formation of Aβ fibrils. The growth of Aβ fibrils was also halted when CRP mutants were added to growing fibrils. Biochemical analyses of CRP mutants revealed altered topology of the Ca2+-binding site, suggesting a role of this region of CRP in binding to Aβ. Combined with previous reports that structurally altered pentameric CRP is generated in vivo, we conclude that CRP is a dual pattern recognition molecule and an antiamyloidogenic protein. These findings have implications for Alzheimer's and other neurodegenerative diseases caused by amyloidosis and for the diseases caused by the deposition of otherwise fluid-phase proteins.

The Pentraxins 1975-2018: Serendipity, Diagnostics and Drugs

The phylogenetically ancient, pentraxin family of plasma proteins, comprises C-reactive protein (CRP) and serum amyloid P component (SAP) in humans and the homologous proteins in other species. They are composed of five, identical, non-covalently associated protomers arranged with cyclic pentameric symmetry in a disc-like configuration. Each protomer has a calcium dependent site that mediates the particular specific ligand binding responsible for all the rigorously established functional properties of these proteins. No genetic deficiency of either human CRP or SAP has been reported, nor even any sequence polymorphism in the proteins themselves. Although their actual functions in humans are therefore unknown, gene deletion studies in mice demonstrate that both proteins can contribute to innate immunity. CRP is the classical human acute phase protein, routinely measured in clinical practice worldwide to monitor disease activity. Human SAP, which is not an acute phase protein, is a universal constituent of all human amyloid deposits as a result of its avid specific binding to amyloid fibrils of all types. SAP thereby contributes to amyloid formation and persistence in vivo. Whole body radiolabelled SAP scintigraphy safely and non-invasively localizes and quantifies systemic amyloid deposits, and has transformed understanding of the natural history of amyloidosis and its response to treatment. Human SAP is also a therapeutic target, both in amyloidosis and Alzheimer's disease. Our drug, miridesap, depletes SAP from the blood and the brain and is currently being tested in the DESPIAD clinical trial in Alzheimer's disease. Meanwhile, the obligate therapeutic partnership of miridesap, to deplete circulating SAP, and dezamizumab, a humanized monoclonal anti-SAP antibody that targets residual SAP in amyloid deposits, produces unprecedented removal of amyloid from the tissues and improves organ function. Human CRP binds to dead and damaged cells in vivo and activates complement and this can exacerbate pre-existing tissue damage. The adverse effects of CRP are completely abrogated by compounds that block its binding to autologous ligands and we are developing CRP inhibitor drugs. The present personal and critical perspective on the pentraxins reports, for the first time, the key role of serendipity in our work since 1975. (345 words).

Amyloid persistence in decellularized liver: biochemical and histopathological characterization

Systemic amyloidoses are a group of debilitating and often fatal diseases in which fibrillar protein aggregates are deposited in the extracellular spaces of a range of tissues. The molecular basis of amyloid formation and tissue localization is still unclear. Although it is likely that the extracellular matrix (ECM) plays an important role in amyloid deposition, this interaction is largely unexplored, mostly because current analytical approaches may alter the delicate and complicated three-dimensional architecture of both ECM and amyloid. We describe here a decellularization procedure for the amyloidotic mouse liver which allows high-resolution visualization of the interactions between amyloid and the constitutive fibers of the extracellular matrix. The primary structure of the fibrillar proteins remains intact and the amyloid fibrils retain their amyloid enhancing factor activity.

Protection of human podocytes from shiga toxin 2-induced phosphorylation of mitogen-activated protein kinases and apoptosis by human serum amyloid P component

Hemolytic uremic syndrome (HUS) is mainly induced by Shiga toxin 2 (Stx2)-producing Escherichia coli. Proteinuria can occur in the early phase of the disease, and its persistence determines the renal prognosis. Stx2 may injure podocytes and induce proteinuria. Human serum amyloid P component (SAP), a member of the pentraxin family, has been shown to protect against Stx2-induced lethality in mice in vivo, presumably by specific binding to the toxin. We therefore tested the hypothesis that SAP can protect against Stx2-induced injury of human podocytes. To elucidate the mechanisms underlying podocyte injury in HUS-associated proteinuria, we assessed Stx2-induced activation of mitogen-activated protein kinases (MAPKs) and apoptosis in immortalized human podocytes and evaluated the impact of SAP on Stx2-induced damage. Human podocytes express Stx2-binding globotriaosylceramide 3. Stx2 applied to cultured podocytes was internalized and then activated p38α MAPK and c-Jun N-terminal kinase (JNK), important signaling steps in cell differentiation and apoptosis. Stx2 also activated caspase 3, resulting in an increased level of apoptosis. Coincubation of podocytes with SAP and Stx2 mitigated the effects of Stx2 and induced upregulation of antiapoptotic Bcl2. These data suggest that podocytes are a target of Stx2 and that SAP protects podocytes against Stx2-induced injury. SAP may therefore be a useful therapeutic option.

Pathogenetic mechanisms of amyloid A amyloidosis

Systemic amyloid A (AA) amyloidosis is a serious complication of chronic inflammation. Serum AA protein (SAA), an acute phase plasma protein, is deposited extracellularly as insoluble amyloid fibrils that damage tissue structure and function. Clinical AA amyloidosis is typically preceded by many years of active inflammation before presenting, most commonly with renal involvement. Using dose-dependent, doxycycline-inducible transgenic expression of SAA in mice, we show that AA amyloid deposition can occur independently of inflammation and that the time before amyloid deposition is determined by the circulating SAA concentration. High level SAA expression induced amyloidosis in all mice after a short, slightly variable delay. SAA was rapidly incorporated into amyloid, acutely reducing circulating SAA concentrations by up to 90%. Prolonged modest SAA overexpression occasionally produced amyloidosis after long delays and primed most mice for explosive amyloidosis when SAA production subsequently increased. Endogenous priming and bulk amyloid deposition are thus separable events, each sensitive to plasma SAA concentration. Amyloid deposits slowly regressed with restoration of normal SAA production after doxycycline withdrawal. Reinduction of SAA overproduction revealed that, following amyloid regression, all mice were primed, especially for rapid glomerular amyloid deposition leading to renal failure, closely resembling the rapid onset of renal failure in clinical AA amyloidosis following acute exacerbation of inflammation. Clinical AA amyloidosis rarely involves the heart, but amyloidotic SAA transgenic mice consistently had minor cardiac amyloid deposits, enabling us to extend to the heart the demonstrable efficacy of our unique antibody therapy for elimination of visceral amyloid.

Computational modeling of the relationship between amyloid and disease

Amyloid is a title conferred upon a special type of linear protein aggregate that exhibits a common set of structural features and dye binding capabilities. The formation of amyloid is associated with over twenty-seven distinct human diseases which are collectively referred to as the amyloidoses. Although there is great diversity amongst the amyloidoses with regard to the polypeptide monomeric precursor, targeted tissues and the nature and time course of disease development, the common underlying link of a structurally similar amyloid aggregate has prompted the search for a unified theory of disease progression in which amyloid production is the central element. Computational modeling has allowed the formulation and testing of scientific hypotheses for exploring this relationship. However, the majority of computational studies on amyloid aggregation are pitched at the atomistic level of description, in simple ideal solution environments, with simulation time scales of the order of microseconds and system sizes limited to a hundred monomers (or less). The experimental reality is that disease related amyloid aggregation processes occur in extremely complex reaction environments (i.e. the human body), over time-scales of months to years with monitoring of the reaction achieved using extremely coarse or indirect experimental markers that yield little or no atomistic insight. Clearly a substantial gap exists between computational and experimental communities with a deficit of 'useful' computational methodology that can be directly related to available markers of disease progression. This Review will place its focus on the development of these latter types of computational models and discuss them in relation to disease onset and progression.

Isolation and characterization of pharmaceutical grade human pentraxins, serum amyloid P component and C-reactive protein, for clinical use

The human pentraxin proteins, serum amyloid P component (SAP) and C‐reactive protein (CRP) are important in routine clinical diagnosis, SAP for systemic amyloidosis and CRP for monitoring the non‐specific acute phase response. They are also targets for novel therapies currently in development but their roles in health and disease are controversial. Thus, both for clinical use and to rigorously elucidate their functions, structurally and functionally intact, pharmaceutical grade preparations of the natural, authentic proteins are required. We report here the production from normal human donor plasma and the characterization of the first such preparations. Importantly, we demonstrate that, contrary to reports using recombinant proteins and less well characterized preparations, neither CRP nor SAP stimulate the release by human peripheral blood mononuclear cells in vitro of any TNFα, IL‐6 or IL‐8, nor does SAP cause release of IL‐1β or IL‐10. Furthermore neither of our preparations was pro‐inflammatory in mice in vivo.

Genomically humanized mice: technologies and promises

Mouse models have become an invaluable tool for understanding human health and disease owing to our ability to manipulate the mouse genome exquisitely. Recent progress in genomic analysis has led to an increase in the number and type of disease-causing mutations detected and has also highlighted the importance of non-coding regions. As a result, there is increasing interest in creating 'genomically' humanized mouse models, in which entire human genomic loci are transferred into the mouse genome. The technical challenges towards achieving this aim are large but are starting to be tackled with success.

Development and evaluation of agents for targeting visceral amyloid

Wall, JS, Solomon A, Kennel, SJ. Development and evaluation of agents for targeting visceral amyloid. Visceral amyloidosis is a rare disease characterized by the deposition in organs and tissues of protein fibrils, heparan sulfate proteoglycan as well as serum amyloid P component and other serum proteins. Imaging these pathologic deposits aids in the clinical management of patients with amyloidosis. Whole body scintigraphic imaging of amyloid load as well as organ specific anatomic imaging provides information that can inform prognosis and can be used to monitor disease progression or response to therapy. These capabilities are limited in the USA, which has led to our development and evaluation of two new reagents that specifically target amyloid in vivo and have been used to image visceral deposits in mice and patients with AL amyloidosis. The fibril-reactive mAb 11-1F4, when labeled with iodine-124 was shown to bind AL amyloid in patients by using PET/CT imaging. These studies were performed to support the evaluation of this reagent as a novel immunotherapy for AL patients. In addition, we have identified a heparin-binding peptide that co-localizes with murine AA amyloid in vivo and can be used to image the deposits. The interaction of this peptide, designated p5, with amyloid is dependent on the net positive charge and truncated forms that would be more desirable as clinical imaging agents were found to be significantly less efficient for amyloid imaging. The development and positive preclinical validation of these two reagents offers potential new therapeutic and diagnostic tools for patients with these devastating diseases.

SPECT imaging of peripheral amyloid in mice by targeting hyper-sulfated heparan sulfate proteoglycans with specific scFv antibodies

INTRODUCTION

Amyloid deposits are associated with a broad spectrum of disorders including monoclonal gammopathies, chronic inflammation, and Alzheimer's disease. In all cases, the amyloid pathology contains, in addition to protein fibrils, a plethora of associated molecules, including high concentrations of heparan sulfate proteoglycans (HSPGs).

METHODS

We have evaluated radioiodinated scFvs that bind HS for their ability to image amyloid deposits in vivo. scFv's with different binding characteristics were isolated by phage display using HS extracted from bovine kidney or mouse and human skeletal muscle glycosaminoglycans (GAGs). Following purification and radioiodination, the biodistribution of (125)I-scFv's was assessed in mice with inflammation-associated AA amyloidosis or in amyloid-free mice by using SPECT imaging, biodistribution measurements and tissue autoradiography.

RESULTS

Four different scFv's all showed binding in vivo to amyloid in the spleen, liver and kidney of diseased mice; however, three of the scFv's also bound to sites within these organs in disease free mice. One scFv specific for hypersulfated HSPGs preferentially bound amyloid and did not accumulate in healthy tissues.

CONCLUSIONS

These data indicate that HS expressed in amyloid deposits has unique qualities that can be distinguished from HS in normal tissues. A scFv specific for rare hypersulfated HS was used to selectively image AA amyloid in mice with minimal retention in normal tissue.

Antibodies to human serum amyloid P component eliminate visceral amyloid deposits

Accumulation of amyloid fibrils in the viscera and connective tissues causes systemic amyloidosis, which is responsible for about one per thousand deaths in developed countries1. Localised amyloid can also be very serious, for example cerebral amyloid angiopathy is an important cause of haemorrhagic stroke. The clinical presentations of amyloidosis are extremely diverse and the diagnosis is rarely made before significant organ damage is present1. There is therefore a major unmet medical need for therapy which safely promotes the clearance of established amyloid deposits. Over 20 different amyloid fibril proteins are responsible for different forms of clinically significant amyloidosis and treatments that substantially reduce the abundance of the respective amyloid fibril precursor protein can arrest amyloid accumulation1. Unfortunately control of fibril protein production is not possible in some forms of amyloidosis and in others is often slow and hazardous1. There is no therapy that directly targets amyloid deposits for enhanced clearance. However, all amyloid deposits contain the normal, non-fibrillar, plasma glycoprotein, serum amyloid P component (SAP)2, 3. Here we show that administration of anti-human SAP antibodies to mice with amyloid deposits containing human SAP, triggers a potent, complement dependent, macrophage-derived giant cell reaction which swiftly removes massive visceral amyloid deposits without adverse effects. Anti-SAP antibody treatment is clinically feasible because circulating human SAP can be depleted in patients by the bis-D-proline compound, CPHPC4, thereby enabling injected anti-SAP antibodies to reach residual SAP in the amyloid deposits. The unprecedented capacity of this novel combined therapy to eliminate amyloid deposits should be applicable to all forms of systemic and local amyloidosis.

Molecular dissection of Alzheimer's disease neuropathology by depletion of serum amyloid P component

New therapeutic approaches in Alzheimer's disease are urgently needed. The normal plasma protein, serum amyloid P component (SAP), is always present in cerebrospinal fluid (CSF) and in the pathognomonic lesions of Alzheimer's disease, cerebrovascular and intracerebral Abeta amyloid plaques and neurofibrillary tangles, as a result of its binding to amyloid fibrils and to paired helical filaments, respectively. SAP itself may also be directly neurocytotoxic. Here, in this unique study in Alzheimer's disease of the bis(d-proline) compound, (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), we observed depletion of circulating SAP and also remarkable, almost complete, disappearance of SAP from the CSF. We demonstrate that SAP depletion in vivo is caused by CPHPC cross-linking pairs of SAP molecules in solution to form complexes that are immediately cleared from the plasma. We have also solved the structure of SAP complexed with phosphothreonine, its likely ligand on hyperphosphorylated tau protein. These results support further clinical study of SAP depletion in Alzheimer's disease and potentially other neurodegenerative diseases.

Cardiovascular magnetic resonance in clinically suspected cardiac amyloidosis: noninvasive imaging compared to endomyocardial biopsy

OBJECTIVES

We sought to evaluate the diagnostic performance of cardiovascular magnetic resonance imaging (CMRI) for detection of cardiac amyloidosis compared with endomyocardial biopsy (EMB) in a clinical routine setting.

BACKGROUND

For the clinical workup of heart failure with restrictive filling, pattern cardiac amyloidosis is an important differential diagnosis that is difficult to verify with current noninvasive techniques, especially in the presence of myocardial hypertrophy.

METHODS

A total of 33 consecutive patients underwent both CMRI and EMB for workup of heart failure with restrictive filling pattern in combination with myocardial hypertrophy (n = 24) and/or clinical conditions often associated with cardiac amyloidosis (n = 18).

RESULTS

Cardiac amyloidosis was detected by EMB in 15 of the 33 patients. In patients with biopsy-proven cardiac amyloidosis, CMRI revealed a distinct pattern of late gadolinium enhancement, which was distributed over the entire subendocardial circumference, extending in various degrees into the neighboring myocardium. This pattern was found in 12 of the 15 patients diagnosed with cardiac amyloidosis by EMB, compared with only 1 individual in the group of 18 patients diagnosed with other myocardial diseases. Consequently, using this pattern as a diagnostic criterion, the sensitivity of CMRI for diagnosing cardiac amyloidosis was 80%, yielding a specificity of 94%. The positive predictive value was 92%, and the negative predictive value was 85%.

CONCLUSIONS

In patients with biopsy-proven cardiac amyloidosis, late gadolinium enhancement frequently occurs in a peculiar pattern. On the basis of the gold standard, EMB, noninvasive CMRI can be used to diagnose or rule out cardiac amyloidosis with good sensitivity and excellent specificity in a clinical routine setting.

Micro-imaging of amyloid in mice

Scintigraphic imaging of radioiodinated serum amyloid P-component is a proven method for the clinical detection of peripheral amyloid deposits (Hawkins et al., 1990). However, the inability to perform comparably high-resolution studies in experimental animal models of amyloid disease has impacted not only basic studies into the pathogenesis of amyloidosis but also in the preclinical in vivo evaluation of potential anti-amyloid therapeutic agents. We have developed microimaging technologies, implemented novel computational methods, and established protocols to generate high-resolution images of amyloid deposits in mice. (125)I-labeled serum amyloid P component (SAP) and an amyloid-fibril reactive murine monoclonal antibody (designated 11-1F4) have been used successfully to acquire high-resolution single photon emission computed tomographic (SPECT) images that, when fused with x-ray computed tomographic (CT) data, have provided precise anatomical localization of secondary (AA) and primary (AL) amyloid deposits in mouse models of these diseases. This chapter will provide detailed protocols for the radioiodination and purification of amyloidophilic proteins and the generation of mouse models of AA and AL amyloidosis. A brief description of the available hardware and the parameters used to acquire high-resolution microSPECT and CT images is presented, and the tools used to perform image reconstruction and visualization that permit the analysis and presentation of image data are discussed. Finally, we provide established methods for measuring organ- and tissue-specific activities with which to corroborate the microSPECT and CT images.

Quantitative high-resolution microradiographic imaging of amyloid deposits in a novel murine model of AA amyloidosis

The mouse model of experimentally induced systemic AA amyloidosis is long established, well validated, and closely analogous to the human form of this disease. However, the induction of amyloid by experimental inflammation is unpredictable, inconsistent, and difficult to modulate. We have previously shown that murine AA amyloid deposits can be imaged using iodine-123 labeled SAP scintigraphy and report here substantial refinements in both the imaging technology and the mouse model itself. In this regard, we have generated a novel prototype of AA amyloid in which mice expressing the human interleukin 6 gene, when given amyloid enhancing factor, develop extensive and progressive systemic AA deposition without an inflammatory stimulus, i.e., a transgenic rapidly inducible amyloid disease (TRIAD) mouse. Additionally, we have constructed high-resolution micro single photon emission computed tomography (SPECT)/computed tomography (CT) instrumentation that provides images revealing the precise anatomic location of amyloid deposits labeled by radioiodinated serum amyloid P component (SAP). Based on reconstructed microSPECT/CT images, as well as autoradiographic, isotope biodistribution, and quantitative histochemical analyses, the (125)I-labeled SAP tracer bound specifically to hepatic and splenic amyloid in the TRIAD animals. The ability to discern radiographically the extent of amyloid burden in the TRIAD model provides a unique opportunity to evaluate the therapeutic efficacy of pharmacologic compounds designed to inhibit fibril formation or effect amyloid resolution.

Cardiovascular magnetic resonance in cardiac amyloidosis

BACKGROUND

Cardiac amyloidosis can be diagnostically challenging. Cardiovascular magnetic resonance (CMR) can assess abnormal myocardial interstitium.

METHODS AND RESULTS

Late gadolinium enhancement CMR was performed in 30 patients with cardiac amyloidosis. In 22 of these, myocardial gadolinium kinetics with T1 mapping was compared with that in 16 hypertensive controls. One patient had CMR and autopsy only. Subendocardial T1 in amyloid patients was shorter than in controls (at 4 minutes: 427+/-73 versus 579+/-75 ms; P<0.01), was shorter than subepicardium T1 for the first 8 minutes (P< or =0.01), and was correlated with markers of increased myocardial amyloid load, as follows: left ventricular (LV) mass (r=-0.51, P=0.013); wall thickness (r=-0.54 to -0.63, P<0.04); interatrial septal thickness (r=-0.52, P=0.001); and diastolic function (r=-0.42, P=0.025). Global subendocardial late gadolinium enhancement was found in 20 amyloid patients (69%); these patients had greater LV mass (126+/-30 versus 93+/-25 g/m2; P=0.009) than unenhanced patients. Histological quantification showed substantial interstitial expansion with amyloid (30.5%) but only minor fibrosis (1.3%). Amyloid was dominantly subendocardial (42%) compared with midwall (29%) and subepicardium (18%). There was 97% concordance in diagnosis of cardiac amyloid by combining the presence of late gadolinium enhancement and an optimized T1 threshold (191 ms at 4 minutes) between myocardium and blood.

CONCLUSIONS

In cardiac amyloidosis, CMR shows a characteristic pattern of global subendocardial late enhancement coupled with abnormal myocardial and blood-pool gadolinium kinetics. The findings agree with the transmural histological distribution of amyloid protein and the cardiac amyloid load and may prove to have value in diagnosis and treatment follow-up.

Amyloid Imaging: From Benchtop to Bedside

Tremendous efforts have been made in the search for a cure or effective treatment of Alzheimer's disease (AD) to develop therapies aimed at halting or reversing amyloid plaque deposition in the brain. This necessitates in vivo detection and quantification of amyloid plaques in the brain for efficacy evaluation of anti-amyloid therapies. For this purpose, a wide array of amyloid-imaging probes has been developed, mainly for in vivo studies based on positron emission tomography and single photon emission computed tomography. This review provides a full account of the development of amyloid-imaging agents. The in vitro binding properties and in vivo pharmacokinetic profiles of all amyloid-imaging agents so far reported are comprehensively and uniquely surveyed. Emphasis is placed on the development of small-molecule probes based on amyloid dyes, such as Congo red and thioflavin T. Compared to large biomolecules, these small-molecule probes have been systematically investigated through extensive structure activity relationship studies. Many of the probes show favorable properties for in vivo studies. As a result, three lead compounds, termed PIB (Pittsburgh-Compound B, [(11)C]6-OH-BTA-1), FDDNP (2-(1-[6-[(2-[(18)F]fluoroethyl)(methyl)amino]-2-naphthyl]ethylidene)malononitrile), and SB-13 (4-N-methylamino-4'-hydroxystilbene), have been identified and evaluated in human subjects. Preliminary studies have indicated that these lead compounds exhibit a characteristic retention in AD subjects that is consistent with the AD pathology, thus proving the concept that amyloid deposits in the brain can be readily detected and quantified in vivo. The progress to date paves the way for further investigation in various aspects of AD research. Once developed, these amyloid-imaging agents could be used as biomarkers to aid in early and definitive diagnosis of AD, facilitate drug discovery and development, and allow pathophysiological studies of the disease mechanism. Furthermore, the success in the development of amyloid-imaging agents helps with the development of imaging agents for in vivo studies of other AD pathologies in particular and of neurodegenerative disorders in general.

Autoimmunity and glomerulonephritis in mice with targeted deletion of the serum amyloid P component gene: SAP deficiency or strain combination?

Human serum amyloid P component (SAP) binds avidly to DNA, chromatin and apoptotic cells in vitro and in vivo. 129/Sv x C57BL/6 mice with targeted deletion of the SAP gene spontaneously develop antinuclear autoantibodies and immune complex glomerulonephritis. SAP-deficient animals, created by backcrossing the 129/Sv SAP gene deletion into pure line C57BL/6 mice and studied here for the first time, also spontaneously developed broad spectrum antinuclear autoimmunity and proliferative immune complex glomerulonephritis but without proteinuria, renal failure, or increased morbidity or mortality. Mice hemizygous for the SAP gene deletion had an intermediate autoimmune phenotype. Injected apoptotic cells and isolated chromatin were more immunogenic in SAP(-/-) mice than in wild-type mice. In contrast, SAP-deficient pure line 129/Sv mice did not produce significant autoantibodies either spontaneously or when immunized with extrinsic chromatin or apoptotic cells, indicating that loss of tolerance is markedly strain dependent. However, SAP deficiency in C57BL/6 mice only marginally affected plasma clearance of exogenous chromatin and had no effect on distribution of exogenous nucleosomes between the liver and kidneys, which were the only tissue sites of catabolism. Furthermore, transgenic expression of human SAP in the C57BL/6 SAP knockout mice did not abrogate the autoimmune phenotype. This may reflect the different binding affinities of mouse and human SAP for nuclear autoantigens and/or the heterologous nature of transgenic human SAP in the mouse. Alternatively, the autoimmunity may be independent of SAP deficiency and caused by expression of 129/Sv chromosome 1 genes in the C57BL/6 background.

Diagnostic tools for amyloidosis

Demonstration of amyloid deposits in biopsy specimens is the only means of confirming the diagnosis of amyloidosis. In experienced hands, nonsurgical biopsies of the rectal mucosa or, preferably, of the abdominal fat pad or labial salivary glands provide the diagnosis in 80 to 85% of cases. Immunolabeling studies help to determine the histological type of amyloidosis but are not performed routinely in everyday practice. In patients with a family history of amyloidosis, studies of the genome and amyloid protein can identify the protein variants capable of causing systemic amyloidosis. Once the diagnosis of amyloidosis is established, the extent of systemic involvement with amyloid should be evaluated by performing renal and hepatic function tests, a proteinuria assay, and an echocardiogram. Scintigraphy with radiolabeled serum amyloid P (SAP) component is a rapid and specific investigation that provides a map of the amyloid deposits. Deposits are usually seen in the liver and spleen. SAP component scintigraphy can provide support for the diagnosis of amyloidosis in patients with negative histological studies. Tissue retention of radioactivity predicts survival.

Serum amyloid P component scintigraphy for diagnosis and monitoring amyloidosis

Serum amyloid P component is a normal plasma protein and a universal non-fibrillar constituent of amyloid deposits. Radiolabelled serum amyloid P component scintigraphy is a non-invasive and quantitative method for imaging amyloid deposits, which produces diagnostic images in most patients with systemic amyloidosis, and can be used repeatedly to monitor the course of the disease. The scintigraphy technique and biopsy histology are complementary, providing a detailed microscopic analysis and a quantitative whole body survey respectively. Clinically useful observations provided by the imaging method include different organ distributions of amyloid in different types of the disease, demonstration of amyloid in anatomic sites not available for biopsy, and evidence for rapid progression and sometimes regression of amyloid deposits with different rates in different organs. Labelled serum amyloid P component studies thus make a unique contribution to the diagnosis and management of individual patients with systemic amyloidosis, and to systematic studies of existing and novel therapies. The technique is available routinely for all known or suspected cases of amyloidosis in the NHS National Amyloidosis Centre at the Royal Free Hospital, but it has not been developed commercially.

Targeted pharmacological depletion of serum amyloid P component for treatment of human amyloidosis

The normal plasma protein serum amyloid P component (SAP) binds to fibrils in all types of amyloid deposits, and contributes to the pathogenesis of amyloidosis. In order to intervene in this process we have developed a drug, R-1-[6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid, that is a competitive inhibitor of SAP binding to amyloid fibrils. This palindromic compound also crosslinks and dimerizes SAP molecules, leading to their very rapid clearance by the liver, and thus produces a marked depletion of circulating human SAP. This mechanism of drug action potently removes SAP from human amyloid deposits in the tissues and may provide a new therapeutic approach to both systemic amyloidosis and diseases associated with local amyloid, including Alzheimer's disease and type 2 diabetes.

Amyloidosis

Amyloidosis is not a single disease but a series of diseases in which there is extracellular deposition of a protein which, although it may be derived from different and unrelated sources, folds into a beta pleated sheet. There have recently been significant advances in elucidating the pathogenesis and in the treatment of this group of disorders. By identifying the source of precursor protein, treatment is aimed at eliminating or reducing the extent of deposition and is tailored for each patient. Early diagnosis is required for the optimal effect of treatment on patient survival and quality of life. An increased awareness among physicians of the spectrum of the disease and tools to aid its diagnosis is of increasing importance.

Amyloid load and clinical outcome in AA amyloidosis in relation to circulating concentration of serum amyloid A protein

BACKGROUND

Reactive systemic (AA, secondary) amyloidosis occurs in chronic inflammatory diseases, and most patients present with nephropathy. The amyloid fibrils are derived from the circulating acute-phase reactant serum amyloid A protein (SAA), but the relation between production of fibril precursor protein, amyloid load, and clinical outcome in AA and other types of amyloidosis is unclear.

METHODS

We studied amyloidotic organ function and survival prospectively for 12-117 months in 80 patients with systemic AA amyloidosis in whom serum SAA concentration was measured monthly and visceral amyloid deposits were assessed annually by serum amyloid P component scintigraphy. Underlying inflammatory diseases were treated as vigorously as possible.

FINDINGS

Amyloid deposits regressed in 25 of 42 patients whose median SAA values were within the reference range (<10 mg/L) throughout follow-up, and amyloidotic organ function stabilised or improved in 39 of these cases. Outcome varied substantially among patients whose median SAA concentration exceeded 10 mg/L, but amyloid load increased and organ function deteriorated in most of those whose SAA was persistently above 50 mg/L. Estimated survival at 10 years was 90% in patients whose median SAA was under 10 mg/L, and 40% among those whose median SAA exceeded this value (p=0.0009).

INTERPRETATION

Although isolated amyloid fibrils are stable in vitro, AA amyloid deposits exist in a state of dynamic turnover, and outcome is favourable in AA amyloidosis when the SAA concentration is maintained below 10 mg/L. The potential for amyloid to regress and for the function of amyloidotic organs to recover support therapeutic strategies to decrease the supply of amyloid fibril precursor proteins in amyloidosis generally.

Prognosis in Juvenile Arthritis

Juvenile arthritis implies an onset of disease under 16 years with arthritis persisting in one or more joints for at least six weeks, and with the active exclusion of well defined illnesses, such as systemic lupus erythematosus. Prognosis implies the ability to predict outcome. Its accuracy depends on many factors with early recognition and appropriate care being important. However, response to treatment may be variable. In general, those with involvement of a few joints do better than those with systemic disease or seropositive juvenile rheumatoid arthritis both with regard to persistence of disease activity and complications. These include not just joint deformities, but osteoporosis, amyloidosis, alterations in growth with overall failure and local anomalies, chronic iridocyclitis and psychosocial problems. More aggressive therapy was only introduced in the 1990's, so it is important that multicentre studies are properly assessed in the context of the suggested International diagnostic criteria. One hundred years ago, George Fredric Still drew attention to the systemic form of the disease as distinct from pure polyarthritis [1], but it was only in the 1970s, as follow-up proceeded, that the separate identity of variants became clinically evident [2]. At the Park City meeting [3] and at the EULAR meeting in 1977 [4] when three subgroups (notably systemic, polyarthritis and pauci-articular onset) were defined, that subclassification became regularly used. However, since there were no absolute diagnostic tests there had to be exclusions. At that time the most common medications were aspirin and corticosteroids, although a few patients received gold or penicillamine. In their large group Wallace and Levinson (1990) [5] found that at the 10 year follow-up between 31% and 55% still had active disease. Girls appeared to have a five-fold greater risk for persistent activity than boys; disease duration was probably the most important factor influencing disease activity at follow-up as suggested previously [6]. It was not until the 1990's that the more aggressive therapy in the form of methotrexate--which Giannini had shown to be effective when given in appropriate dosage [7]--and sulphasalazine [8] and the long acting local corticosteroid triamcinolone hexatonide became regularly employed [9, 10]. At the ILAR Meeting in 1993 an international task force was set up under the chairmanship of Dr. C. Fink [11] to develop a classification for the idiopathic arthritides in children, defining childhood as up to 16 years of age. Active exclusion of well-recognised disorders such as rheumatic fever or systemic lupus erythematosus, still had to be made. The first proposed types, which are mutually exclusive, are shown in Table 1. A more recent meeting in Durban under the chairmanship of Dr. R. Petty is yet to be published, but considerable advances have been made, particularly in the definition of subgroups.

Dialysis-related amyloidosis of the tongue in long-term hemodialysis patients

Dialysis-related amyloidosis (DRA) predominantly occurs in the osteoarticular structures. However, according to studies in the increasing number of long-term hemodialysis patients, DRA has also been systemically found to appear in the other tissues and organs as well. In this study, we investigated lingual amyloidosis in relation to systemic DRA. A total of 472 patients were studied who were on regular hemodialysis for more than 10 years, including 103 patients for more than 20 years. Eight of these patients (7 males and 1 female, mean age 59 +/- 8 years, range 46 to 68 years) developed lingual amyloidosis, seemingly as a result of beta2-microglobulin (beta2m) deposits. All patients demonstrating lingual amyloidosis had been treated with regular hemodialysis for more than 20 years (mean HD duration 23.6 +/- 1.4 years), and its morbidity was 7.8% in the 103 patients and 20% (6 patients) in the 30 patients treated for more than 23 years with hemodialysis. Hemodialysis (HD) duration with bioincompatible unsubstituted cellulose membranes in the 8 patients was longer than that in the control group without lingual amyloidosis (P < 0.05). Lingual amyloid nodules were whitish-yellow in color and varied in size, at least over 1 mm in diameter. Their consistency was firmer than the intact tongue. The location of the amyloid nodules could be classified into two types: (1) diffuse type (diffusely distributed over the tongue), and (2) lateral type (localized only in the lateral side of the tongue). Five of the eight patients with lingual amyloidosis complained of functional disturbances in the tongue, such as abnormal taste, or difficulty in mobility and articulation. No macroglossia was observed in any of these cases. It was thus concluded that DRA of the tongue is a very rare complication, occurring in the late stage of long-term hemodialysis patients, that disturbs their quality of life.

Amyloid deposition is delayed in mice with targeted deletion of the serum amyloid P component gene

The tissue amyloid deposits that characterize systemic amyloidosis, Alzheimer's disease and the transmissible spongiform encephalopathies always contain serum amyloid P component (SAP) bound to the amyloid fibrils. We have previously proposed that this normal plasma protein may contribute to amyloidogenesis by stabilizing the deposits. Here we show that the induction of reactive amyloidosis is retarded in mice with targeted deletion of the SAP gene. This first demonstration of the participation of SAP in pathogenesis of amyloidosis in vivo confirms that inhibition of SAP binding to amyloid fibrils is an attractive therapeutic target in a range of serious human diseases.

Biology and therapy of immunoglobulin deposition diseases

All forms of MIDD represent pathologic deposition of immunoglobulin as amorphous casts, crystals, congophilic fibrils (in AL amyloid), or punctate noncongophilic deposits (in LCDD/HCDD/LHCDD). Diagnosis is based on identification and immunohistochemical characterization of deposits and Congo red staining. Current information including development of novel in vitro and in vivo models suggests a contributory role of both protein and host factors in the pathogenesis of these disorders. In particular, primary structural features of the VL portions of the light chain molecule may affect not only the extent but also the morphologic type of protein deposits. Thus, certain types of light chains may be particularly pathogenic, although the nature or extent of proteolysis/processing involved in the pathogenesis of these deposits is yet unclear. Recent data also point to the importance of accessory molecules, cytokines, and host factors in this process. Newer therapeutic approaches using high-dose therapy with cytotoxic agents or dexamethasone appear promising, although these data need to be confirmed in a larger number of patients. The serendipitous discovery of I-DOX as an agent capable of promoting amyloid resorption provides another novel approach in patients with AL amyloidosis. Continued research on the mechanisms of deposition and resorption of these immunoglobulin deposits should provide important information that can be used to design strategies for more effective therapy and, ultimately, prevention of MIDD.

Long term effect of renal transplantation on dialysis-related amyloid deposits and symptomatology

We report the five year outcome of nine patients with dialysis-related amyloid (DRA) who underwent successful renal transplantation (RT) and six patients who remained on hemodialysis (HD). Amyloid bone cysts, a radiologic feature of DRA, and scintigraphy with 123I-labeled serum amyloid P component (SAP), a specific technique for evaluating amyloid deposits in vivo, were monitored and compared with clinical features. In all HD patients there was clinical, scintigraphic and/or radiologic evidence that DRA progressed. In contrast, eight of the RT patients experienced profound early relief of DRA symptoms following transplantation that persisted throughout follow-up, despite the reduction or withdrawal of corticosteroids. Amyloid bone cysts improved in four patients and SAP scans demonstrated regression of articular amyloid in eight out of nine cases. The modest radiographic improvement suggests that amyloid is mobilized more slowly in bone cysts than elsewhere or that cystic bone is remodeled poorly. This is the first objective evidence that DRA regresses following renal transplantation, and suggests that this may contribute to the long-term relief of DRA symptoms in transplant recipients who discontinue corticosteroids.

Ca(2+)-dependent binding of human serum amyloid P component to Alzheimer's beta-amyloid peptide

Serum amyloid P component (SAP), a normal glycoprotein, is universally found in amyloid deposits, including cerebrovascular amyloid of Alzheimer's disease. This paper describes the Ca(2+)-dependent binding of human SAP to Alzheimer's beta-amyloid peptide (A beta). 125I-SAP binds to synthetic human A beta-(1-40) immobilized on microtiter plates at a dissociation constant of 6.0 x 10(-9) M in 0.01 M Tris-HCl, 0.15 M NaCl, pH 7.5, containing 2 mM Ca2+, 1% bovine serum albumin, and 0.05% Tween 20. Binding inhibition assay has shown that soluble A beta-(1-40) and A beta-(1-28) also bind to SAP. Since SAP is resistant to proteases in the presence of calcium, the Ca(2+)-dependent binding of SAP to soluble A beta and to beta-amyloid fibrils would give pathological effects on fibril formation and persistence of beta-amyloid in Alzheimer's disease.

Native human serum amyloid P component is a single pentamer

Serum amyloid P component (SAP) and C-reactive protein (CRP) are members of the pentraxin protein family. SAP is the precursor protein to amyloid P component present in all forms of amyloidosis. The prevailing notion is that SAP in circulation has the form of a double pentameric molecule (decamer) whereas CRP is a single pentameric molecule. We have investigated by gel permeation chromatography the M(r) of SAP in freshly collected human serum and of SAP purified by carbohydrate affinity chromatography and anion exchange chromatography. SAP was monitored by quantitative immunoelectrophoresis and ELISA, and SAP peak fractions were analysed by use of SDS-PAGE, Western blotting, and electron microscopy. The results indicate that native SAP circulates as a single pentamer, a part of which forms complexes with C4b-binding protein. The properties of SAP changed during purification as indicated by rocket immunoelectrophoresis and electron microscopy. Thus, electron micrographs of purified SAP showed a predominance of decamers. However, the decamer form of SAP reversed to single pentamers when purified SAP was incorporated into SAP-depleted serum.

Amyloidosis

Amyloidosis is a heterogeneous group of disorders characterized by extracellular deposition of abnormal protein fibrils which are derived from different proteins in different forms of the disease. Asymptomatic amyloid deposition in a variety of tissues is a universal accompaniment of ageing, and clinical amyloidosis is not rare. Intracerebral and cerebrovascular beta-protein amyloid deposits are a hallmark of the pathology of both sporadic and familial Alzheimer's disease, beta 2-microglobulin-derived amyloid is a common complication of long term haemodialysis, and islet amyloid polypeptide is the fibril protein in the universal islet amyloidosis of type II diabetes mellitus. New fibril proteins have lately been identified in hereditary amyloidosis, including variants of gelsolin, apolipoprotein AI, lysozyme and fibrinogen. The development of radiolabelled serum amyloid P component (SAP) scintigraphy has allowed amyloid to be diagnosed non-invasively in vivo for the first time, provided unique insight into the distribution and size of amyloid deposits, and yielded novel information on the natural history and the effects of treatment. Amyloid deposits are in a state of dynamic turnover and can regress if new fibril formation is halted. The recent elucidation of the three dimensional structure of human SAP may enable the design of specific therapeutic agents.

The pentraxins, C-reactive protein and serum amyloid P component, are cleared and catabolized by hepatocytes in vivo

The cellular sites of clearance and degradation of the pentraxin plasma proteins, C-reactive protein, the classical acute phase reactant, and serum amyloid P component (SAP), a universal constituent of amyloid deposits, were sought using the ligand 125I-tyramine cellobiose (TC) which is substantially retained within the cells in which catabolism takes place. Pentraxins labeled with 125I-TC showed the same in vitro and in vivo ligand binding and the same in vivo plasma t1/2 as the directly iodinated proteins and the native unlabeled pentraxins, indicating that their mode of clearance was likely to be physiological. After intravenous injection into mice and rabbits of human C-reactive protein, human SAP, and mouse SAP, each labeled with 125I-TC, most of the radioactivity remaining in the body at 24 h was located in hepatocytes. None was detected in other liver cells, and only traces were present in other viscera; the rest was in the carcass, representing intact pentraxins in the blood and extravascular compartment, and escaped label which had not yet been excreted. Hepatocytes are thus the single major site of pentraxin clearance and catabolism in vivo. This is consistent with the observation that SAP that has localized to amyloid deposits persists there and is not degraded.

Demonstration of CRP immunoreactivity in brains of Alzheimer's disease: immunohistochemical study using formic acid pretreatment of tissue sections

C-reactive protein (CRP) is a well-known serum protein which increases during inflammation and deposits in damaged tissues. To establish whether CRP appears in brain of Alzheimer's disease (AD), we immunohistochemically investigated tissue sections which were pretreated with formic acid. Positive immunostaining by anti-CRP antibodies was clearly recognized in senile plaques (SP) in the pretreated tissue sections, with very weak immunostaining in non-treated sections. These findings may suggest that the formation process of SP includes an acute-phase inflammatory state.

Diagnosis and monitoring of amyloidosis

The diagnosis of systemic amyloidosis is only occasionally suspected on clinical grounds alone and is more often considered when an associated condition, such as a chronic inflammatory disease or monoclonal gammopathy, is present. No blood test is diagnostic of amyloid although routine haematological and biochemical investigations have important roles in defining the underlying disease process in amyloidosis, and evaluating organ function. A number of non-invasive investigations including echocardiography, electrocardiography and soft tissue scintigraphy with bone-seeking tracers give characteristic results in some patients with amyloidosis, but are non-specific. The diagnosis can only be confirmed by demonstrating the presence of amyloid deposits in the tissues. Histology is the traditional method in routine clinical practice and is sensitive for revealing microscopic deposits and permits immunotyping of fibril proteins. Disadvantages are that biopsies are invasive, open to sampling error and can only give limited information on the distribution and extent of amyloid deposits in an individual. Scintigraphic and turnover studies with radioiodinated SAP are new specific methods for confirming the presence of amyloid in tissues, based on the affinity of SAP for all types of amyloid fibril. Labelled SAP scans survey the whole body macroscopically for the presence and anatomical distribution of amyloid in a quantitative manner, and SAP turnover studies provide information on the whole body amyloid load. Although the availability of SAP scintigraphy presently remains restricted, the technique has been used in over 400 patients with amyloid in prospective studies, and has already provided a number of new insights into the natural history of amyloidosis. These include the observation that there is a consistently poor correlation between the quantity of amyloid in an organ and the resulting degree of functional impairment. Amyloid deposits accumulate at rates which vary substantially between different organs in a single subject and between individuals with similar types of amyloidosis, even when the rates of amyloid fibril precursor protein supply are apparently similar. In some patients amyloid accumulation may plateau without any measurable alteration in the precursor supply. In patients with amyloidosis in whom the supply of fibril precursors is reduced, either as a result of therapy directed towards the underlying process or through a natural remission, substantial regression of amyloid frequently occurs. This has been observed in patients with AA, AL and variant TTR-associated amyloidosis, and is usually associated with clinical benefits. In some such cases, however, the function of affected organs may continue to deteriorate despite halting the accumulation of amyloid, presumably because irreversible structural damage has already occurred.(ABSTRACT TRUNCATED AT 400 WORDS)

Labeling of cerebral amyloid in vivo with a monoclonal antibody

We assessed the ability of a murine monoclonal antibody to bind selectively to beta-amyloid in the brains of living nonhuman primates. To circumvent the blood-brain barrier, we injected unlabeled antibody 10D5 (murine whole IgG1 and/or Fab fragments) into the cerebrospinal fluid of the cisterna magna in three aged monkeys. A control animal was given an intracisternal injection of nonimmune mouse whole IgG plus Fab. Twenty-four hours later, the animals were perfused and prepared for immunohistochemical detection of bound murine immunoglobulin in brain. All three experimental animals showed selective binding of 10D5 to approximately 5-15% of amyloid deposits in cerebral cortex, primarily near the cortical surface. There was no labeling in the control animal. In vivo-labeled deposits were confirmed to be beta-amyloid by electron microscopy and by in vitro immunohistochemistry in adjacent sections. The animals tolerated the injection well, although some polymorphonuclear leukocytes infiltrated portions of the subarachnoid space and superficial neocortex. These results provide the first demonstration that it may be feasible to selectively direct a tagged monoclonal antibody to beta-amyloid in the brain for therapeutic or diagnostic purposes. With enhancement of labeling efficiency, the method also may be useful for studying the progression of beta-amyloidosis in experimental animals using emission tomography.

Studies of the structure and binding properties of hamster female protein

We report here the characterization of hamster female protein (FP), a member of the pentraxin family of plasma proteins, as a molecule composed of glycosylated subunits of 25,655 MW containing a single intrachain disulphide bridge. In the presence of EDTA the subunits are non-covalently associated as pentamers of mass approximately 128,000 MW, and in the presence of calcium they aggregate further, probably to form decamers. This pentamer-decamer transition at physiological ionic strength has not been described in other pentraxins. As previously reported, FP shares the capacity of C-reactive protein (CRP) in other species to bind phosphocholine and we show here that it also resembles human CRP in binding only weakly to agarose, to human AA amyloid fibrils in vitro, and to mouse AA amyloid deposits in vivo. It thus differs markedly from human and mouse serum amyloid P component (SAP) but it is nevertheless deposited in hamster AA amyloid in vivo and clearly is the hamster counterpart of SAP in other species. These results illustrate the subtle diversity among members of the otherwise conserved pentraxin family of vertebrate plasma proteins.

Metabolic and scintigraphic studies of radioiodinated human C-reactive protein in health and disease

Plasma and whole-body turnover studies of human C-reactive protein (CRP), isolated from a single normal healthy donor and labeled with 125I, were undertaken in 8 healthy control subjects and 35 hospitalized patients including cases of rheumatoid arthritis, systemic lupus erythematosus, infections, and neoplasia. Plasma clearance of 125I-CRP closely approximated to a monoexponential function and was similar in the control and all patient groups. There was no evidence for accelerated clearance or catabolism of CRP in any of the diseases studied. The 19-h half-life was more rapid than that of most human plasma proteins studied previously, and the fractional catabolic rate was independent of the plasma CRP concentration. The synthesis rate of CRP is thus the only significant determinant of its plasma level, confirming the validity of serum CRP measurement as an objective index of disease activity in disorders associated with an acute-phase response. Approximately 90% of injected radioactivity was recovered in the urine after 7 d, and scintigraphic imaging studies with 123I-labeled CRP in 10 patients with different focal pathology showed no significant localization of tracer. The functions of CRP are thus likely to be effected predominantly in the fluid phase rather than by major deposition at sites of tissue damage or inflammation.

Rapid method to isolate serum amyloid P component from human plasma. Characterization of the isolated protein

A rapid and reproducible method to isolate serum amyloid P component from healthy human plasma has been developed. It uses affinity chromatography on an agarose column followed by anion-exchange chromatography. It was found that the isolated compound has a significantly different isoelectric point (pI 5.7) from that reported previously (pI 4.1). The new data are in good agreement with calculated values determined from the amino acid composition of the protein.

Serum amyloid P component: a predictor of clinical beta 2-microglobulin amyloidosis

Beta 2-microglobulin (beta 2M) amyloidosis is common in patients on long-term hemodialysis, but the clinical conditions associated with disease activity are poorly understood. This study was designed to determine if the serum amyloid P (AP) component concentration is predictive of beta 2M amyloid disease activity. Serum AP component concentrations were determined by rocket immunoelectrophoresis and beta 2M concentrations by a commercially available kit. Radiographic evidence of beta 2M amyloidosis was determined from bone films of the hips, shoulders, and hands. Serum AP component concentrations were not different in dialysis and control patients. However, AP component concentrations in long-term (greater than or equal to 5 years) dialysis patients were significantly lower than in short-term (less than 5 years) dialysis patients (43.0 +/- 16.9 micrograms/mL [n = 28] v 56.0 +/- 18.3 micrograms/mL [n = 31], P less than 0.05). The patients on hemodialysis for 5 or more years who had radiographic evidence of severe beta 2 M amyloidosis were significantly older (57.9 +/- 9.5 v 38.3 +/- 11.3 years, P less than 0.001) and their serum AP concentrations were significantly lower (34.3 +/- 15.0 v 50.1 +/- 15.6 micrograms/mL, P less than 0.05) than long-term dialysis patients without radiographic evidence of disease. Stepwise regression analysis showed that the patient's age and serum AP component concentration were predictors of radiographic evidence of beta 2 M amyloidosis. Thus, serum AP component concentrations are decreased in long-term dialysis patients, suggesting accelerated deposition into amyloid deposits.(ABSTRACT TRUNCATED AT 250 WORDS)