Biology and therapy of immunoglobulin deposition diseases

Differential recruitment efficacy of patient-derived amyloidogenic and myeloma light chain proteins by synthetic fibrils-A metric for predicting amyloid propensity

BACKGROUND

Monoclonal free light chain (LC) proteins are present in the circulation of patients with immunoproliferative disorders such as light chain (AL) amyloidosis and multiple myeloma (MM). Light chain-associated amyloid is a complex pathology composed of proteinaceous fibrils and extracellular matrix proteins found in all patients with AL and in ~10-30% of patients who presented with MM. Amyloid deposits systemically in multiple organs and tissues leading to dysfunction and ultimately death. The overall survival of patients with amyloidosis is worse than for those with early stage MM.

METHODS AND FINDINGS

We have developed a sensitive binding assay quantifying the recruitment of full length, patient-derived LC proteins by synthetic amyloid fibrils, as a method for studying their amyloidogenic potential. In a survey of eight urinary LC, both AL and MM-associated proteins were recruited by synthetic amyloid fibrils; however, AL-associated LC bound significantly more efficiently (p < 0.05) than did MM LCs. The LC proteins used in this study were isolated from urine and presumed to represent a surrogate of serum free light chains.

CONCLUSION

The binding of LC to synthetic fibrils in this assay accurately differentiated LC with amyloidogenic propensity from MM LC that were not associated with clinical amyloid disease. Notably, the LC from a MM patient who subsequently developed amyloid behaved as an AL-associated protein in the assay, indicating the possibility for identifying MM patients at risk for developing amyloidosis based on the light chain recruitment efficacy. With this information, at risk patients can be monitored more closely for the development of amyloidosis, allowing timely administration of novel, amyloid-directed immunotherapies-this approach may improve the prognosis for these patients.

Primary hepatic amyloidosis: report of an unusual case presenting as a mass

Hepatic involvement of amyloidosis is common. Diffuse infiltration with hepatomegaly is a usual radiologic finding of hepatic amyloidosis. To our knowledge, this is the first case of amyloidosis involving the liver that presented as a mass.

Renal Impairment in Patients With Multiple Myeloma: A Consensus Statement on Behalf of the International Myeloma Working Group

Renal impairment is a common complication of multiple myeloma (MM). The estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease formula is the recommended method for the assessment of renal function in patients with MM with stabilized serum creatinine. In acute renal injury, the RIFLE (risk, injury, failure, loss and end-stage kidney disease) and Acute Renal Injury Network criteria seem to be appropriate to define the severity of renal impairment. Novel criteria based on eGFR measurements are recommended for the definition of the reversibility of renal impairment. Rapid intervention to reverse renal dysfunction is critical for the management of these patients, especially for those with light chain cast nephropathy. Bortezomib with high-dose dexamethasone is considered as the treatment of choice for such patients. There is limited experience with thalidomide in patients with myeloma with renal impairment. Thus, thalidomide can be carefully administered, mainly in the context of well-designed clinical trials, to evaluate if it can improve the rapidity and probability of response that is produced by the combination with bortezomib and high-dose dexamethasone. Lenalidomide is effective in this setting and can reverse renal insufficiency in a significant subset of patients, when it is given at reduced doses, according to renal function. The role of plasma exchange in patients with suspected light chain cast nephropathy and renal impairment is controversial. High-dose melphalan (140 mg/m2) and autologous stem-cell transplantation should be limited to younger patients with chemosensitive disease.

Rheumatoid arthritis and renal light-chain deposition disease: long-term effectiveness of TNF-α blockade with etanercept

A 68-year-old woman diagnosed with erosive rheumatoid arthritis (RA) was treated with intramuscular methotrexate 15 mg weekly and oral prednisone 5 mg daily. A favorable outcome of 6 years was followed by RA flare and nephrotic syndrome (NS). Renal biopsy revealed non-amyloid light-chain deposition disease. Laboratory analysis and bone marrow biopsy excluded monoclonal protein and plasma cell dyscrasia. Addition of subcutaneous etanercept, 25 mg twice weekly allowed rapid control of both arthritis and NS. To date, after over 7-year follow-up, RA is in clinical remission, 24-h albuminuria is consistently below 0.5 g, and serum creatinine is 0.9 mg/dl.

Facial papules as a marker of internal malignancy

Facial papules (bumps) confront the general practitioner during every face-to-face meeting with the patient. Increased awareness and recognition of the facial papules that represent cutaneous signs of internal malignancy will allow an early, aggressive workup and treatment of any associated cancer. This article details the clinical presentation, etiology, pathologic findings, and associated malignancy for such presentations. A skin biopsy for histopathologic diagnosis is necessary to distinguish these clues to underlying malignancy from the numerous benign lesions that cause facial papules.

Complications of multiple myeloma

Multiple myeloma, also known as myeloma or plasma cell myeloma, is a progressive hematologic disease. Complications of multiple myeloma include renal insufficiency, hematologic complications (anemia, bone marrow failure, bleeding disorders), infections, bone complications (pathologic fractures, spinal cord compression, hyercalcemia), and neurologic complications (spinal cord and nerve root compression, intracranial plasmacytomas, leptomeningeal involvement, among others). This article reviews these various complications connected to multiple myeloma, examining their various causes and possible treatment.

Amyloidosis

Amyloidosis is a disease in which abnormal proteins form fibrillar tissue deposits that can compromise key viscera and lead to early death. In order to treat amyloidosis, the type of abnormal protein must be identified. The most common type is monoclonal immunoglobulin light chain or AL amyloidosis; the other important type is hereditary, caused by variant forms of transthyretin and other proteins, whereas amyloid associated with chronic inflammation ("secondary") is rare in the developed world. AL can be misdiagnosed if a monoclonal gammopathy and a hereditary variant are present in the same patient. The aim of therapy in systemic AL amyloidosis is to reduce the amyloid-forming monoclonal light chain, measured with the serum free light chain assay, by suppressing the underlying plasma cell dyscrasia, while using supportive measures to sustain organ function. Amyloid deposits can be resorbed and organ function restored if the amyloid-forming precursor light chain is eliminated. The most effective treatment for systemic AL amyloidosis is risk-adapted melphalan with peripheral blood stem cell transplant (SCT). The hematologic response rate is 75% at 12 months when adjuvant therapy with thalidomide and dexamethasone is used post-SCT. Patients can achieve long-term durable remissions with organ recovery. Drugs effective in multiple myeloma are usually helpful in AL amyloidosis if tolerated. The use of novel antibody-based approaches for imaging amyloid and possibly for accelerating removal of deposits is under active investigation.

Prion urine comprises a glycosaminoglycan-light chain IgG complex that can be stained by Congo red

Light chain IgG, a known amyloidotic protein, is present in the urine of prion disease affected individuals in a protease resistant form. In addition, it was shown recently that prion urine samples comprise a significant excess of glycosaminoglycans. Since amyloidotic proteins and glycosaminoglycans are the major components of amyloid aggregates, a Congo red dot blot assay was developed for detection of Creutzfeldt-Jacob disease (CJD) in urine. This assay was also positive for about 10% of patients suffering from diseases such as Alzheimer disease, cerebrovascular attacks and multiple sclerosis, but negative for healthy controls. Both glycosaminoglycans and proteins such as light chain IgG were required for the binding of Congo red to the urine fractions, as shown by the fact that Proteinase K digestion of the samples either after guanidine or after choindrotinase abolished the Congo red signal from the CJD samples.

Characterization of a dimeric unfolding intermediate of bovine serum albumin under mildly acidic condition

Protein aggregation is a well-known phenomenon related to serious medical implications. Bovine serum albumin (BSA), a structural analogue of human serum albumin, has a natural tendency for aggregation under stress conditions. While following effect of moderately acidic pH on BSA, a state was identified at pH 4.2 having increased light scattering capability at 350 nm. It was essentially a dimer devoid of disulphide linked large aggregates as observed from 'spin column' experiments, gel electrophoresis and ultra-centrifugations. Its surface hydrophobic character was comparable to the native conformer at pH 7.0 as observed by the extraneous fluorescence probes pyrene and pyrene maleimide but its interactions with 1-anilino 8-naphthelene sulphonic acid was more favorable. Dimerization was irreversible between pH 4.2 and 7.0 even after treatment with DTT. The role of the only cysteine-34 residue was investigated where modification with reagents of arm length bigger than 6 A prevented dimerization. Molecular modeling of BSA indicated that cys-34 resides in a cleft of 6 A depth. This indicated that the area surrounding the cleft plays important role in inducing the dimerization.

Renal, hematologic and infectious complications in multiple myeloma

Renal failure is a common complication in patients with multiple myeloma. It is generally due to tubular light-chain damage, and it is reversible in about 50% of patients. The reversibility rate depends on the degree of light-chain nephropathy. The initial therapy should consist of dexamethasone- or cyclophosphamide-based regimens. High-dose therapy/autologous transplant may be of benefit in selected patients. Early plasma exchange may be useful in patients who have severe renal failure but do not yet require dialysis. Renal replacement with dialysis is a worthwhile measure in patients with end-stage renal failure. Anemia is the most common hematologic complication. About 70% of anemic patients respond to recombinant human erythropoietin (rHuEPO), resulting not only in an increase in the hemoglobin level but also in an improvement in the quality of life. The hemoglobin level should ideally be maintained at around 12 g/dL. Infection is the main cause of morbidity and mortality in patients with myeloma. The highest risk of infection is within the first 2 months of initiation of therapy as well as in patients with renal failure and in those with relapsed and refractory disease.

Amyloses multisystémiques

OBJECTIVE

Clinical analysis of multisystem amyloidosis in Lebanon, by histological type.

METHOD

Retrospective study of 39 cases of multisystem amyloidosis diagnosed histologically in a university hospital center between 1991 and 2002. It analyzed the following clinical data: age, gender, type of presentation, time from symptom onset to diagnosis, clinical features, concomitant diseases, family history of amyloidosis, biopsy sites, presence of urinary or serum monoclonal gammopathy, immunohistochemical type, prognosis and treatment.

RESULTS

Median age at diagnosis was 56+/-18 years. The overall ratio of men to woman was 1.4. AL amyloidosis (amyloid light chain) accounted for 54% (21/39) of the cases, AA (amyloid-associated) amyloidosis 36% (14/39), while 10% (4/39) were not typed. Among the 21 cases of AL amyloidosis, 12 were idiopathic (57%) and 9 (43%) were associated with multiple myeloma; among the 14 cases of AA amyloidosis, 7 were associated with familial Mediterranean fever and 5 with chronic disorders. Proteinuria was often the first symptom. The initial manifestations in AL amyloidosis patients with myeloma were more often related to amyloidosis than to myeloma. Renal involvement was seen in 95% (37/39) of all cases (95% of AL versus 93% of AA), proteinuria in 87% of cases and renal failure in 72%. Cardiac amyloidosis (57% of AL versus 7% of AA; p>0.05), infiltration of the tongue (19% of AL versus 0% of AA; p>0.05) and neurological manifestations (24% of AL versus 7% of AA; p>0.05) were more frequent in AL amyloidosis. The 7 patients who died (18%) had AL amyloidosis (5 of them had myeloma). Heart failure was the most frequent cause of death related to amyloid.

CONCLUSION

Multisystem amyloidosis is frequent in Lebanon and familial Mediterranean fever is still frequently associated with the secondary type. Accurate diagnosis and classification are essential for the prognosis and treatment of the disease. Poor prognosis was associated with the AL type, especially when accompanied by myeloma, and with cardiac amyloidosis.

Immunotherapy in systemic primary (AL) amyloidosis using amyloid-reactive monoclonal antibodies

Heretofore, treatment of patients with primary or light chain-associated (AL) amyloidosis has been directed toward reducing the synthesis of the amyloidogenic precursor protein through conventional or high-dose cytotoxic antiplasma cell chemotherapy. Although such efforts have extended survival, most often the prognosis remains exceedingly poor due to the persistence (or progression) of the pathologic deposits. The development of murine amyloid-reactive monoclonal antibodies (mAbs) has provided another therapeutic approach; namely, passive immunotherapy. These reagents, prepared against human light chain-related fibrils, recognize an epitope common to the beta-pleated structure of AL and other types of amyloid proteins and can effect rapid amyloidolysis when administered to mice injected with human AL amyloid extracts. One such prototypic antibody, the IgG1kappa mAb 11-1F4, has now been chimerized and is undergoing GMP production for an eventual phase I and II clinical trial in patients with AL amyloidosis. Demonstration of the therapeutic efficacy of this amyloid-reactive mAb would provide an important proof-of-principle that this form of immunotherapy also could benefit individuals with other types of inherited or acquired amyloid-associated disease.

High dose chemotherapy in light chain or light and heavy chain deposition disease

BACKGROUND

Conventional chemotherapy for myeloma yield unsatisfactory results in light and/or heavy chain deposition disease [(H)CDD] Because of the well-established dose-response effect of high dose melphalan in multiple myeloma, aiming to dramatically reduce the pathogenic monoclonal immunoglobulin (MIg) level, high dose therapy is a tempting alternative approach.

METHODS

We treated 11 young patients with L(H)CDD by high dose therapy with the support of autologous blood stem cell transplantation. All had renal symptoms, including four who required dialysis and seven who had various, mainly cardiac, extrarenal manifestations.

RESULTS

No toxic deaths occurred. A decrease in the MIg level was observed in eight patients, with complete disappearance from serum and urine in six cases. Improvement in manifestations related to MIg deposits were observed in six patients, including renal, cardiac, and hepatic responses in 4/11, 4/4, and 2/2 cases, respectively. Histologic regression of MIg deposits was documented in cardiac, hepatic, and skin biopsies. In contrast, examination of the kidney still showed light chain deposits in one patient who had renal transplantation 3 years after high dose therapy, at a time when he was in persisting remission. Within a median follow-up of 51 months, three patients were retreated because of multiple myeloma relapse, of whom one died and one required hemodialysis, and renal function secondarily deteriorated in a patient who had resistant multiple myeloma. Otherwise, no manifestations related to MIg deposits occurred or recurred in any patient.

CONCLUSION

Present results of this retrospective study argue in favor of a benefit of high dose therapy with stem cell support in young patients with L(H)CDD.

A multicenter phase 2 trial of stem cell transplantation for immunoglobulin light-chain amyloidosis (E4A97): an Eastern Cooperative Oncology Group Study

Stem cell transplantation was introduced as a new therapeutic modality for amyloidosis. The purpose of the current study was to determine the feasibility and toxicity of stem cell transplantation for amyloidosis in a cooperative group setting in which most participating institutions would have limited experience in managing the disorder. A total of 30 patients with biopsy-proven amyloidosis shown to be immunoglobulin light-chain type were enrolled on this trial. The protocol required mobilization of a minimum of 6 x 10(8) mononuclear cells/kg or 5 x 10(6) CD34(+) cells/kg ideal body weight. These targets had to be achieved within seven collections. Patients with advanced hepatic, renal, or cardiac failure were excluded. End points included objective response rate and overall survival. The secondary end point of the protocol was nonhematologic toxicity. Accrual to the study was faster than expected. The overall response rate (hematologic and organ) was 64%, with three treatment-related deaths. Another patient died before day 30 of sudden cardiac death not treatment related. The median follow-up of surviving patients is 30.3 months. Median survival has not been reached. Stem cell transplantation for selected patients with amyloidosis is feasible in a cooperative group setting. A multicenter phase 3 trial of high-dose therapy is indicated.

Amyloidosis: Review and CT Manifestations

Amyloidosis is a collection of disease entities that produce considerable morbidity and mortality and are increasing in prevalence. The imaging findings are problematically nonspecific and diverse. This lack of specificity is compounded by the fact that amyloidosis is strongly associated with and frequently coexists with many other chronic disease states that have their own imaging findings. Amyloidosis can involve any organ singly or in conjunction with other organs and can do so in the form of a focal, tumorlike lesion or an infiltrative process. In the proper clinical setting, that is, in a patient with chronic inflammatory disease and especially in a patient with multiple myeloma, amyloidosis should be considered as a possible cause of worsening or new symptoms or imaging findings. Occasionally, the radiologic findings may precede the clinical findings, thus providing the radiologist with the opportunity to contribute to the patient's care. However, to make a difference in patient care, the radiologist must be familiar with the diverse imaging findings of amyloidosis as well as the patient's clinical history, which could raise the suspicion of amyloidosis.

Analysis of V(lambda)-J(lambda) expression in plasma cells from primary (AL) amyloidosis and normal bone marrow identifies 3r (lambdaIII) as a new amyloid-associated germline gene segment

Primary (AL) amyloidosis is a plasma cell dyscrasia characterized by extracellular deposition of monoclonal light-chain variable region (V) fragments in the form of amyloid fibrils. Light-chain amyloid is rare, and it is not fully understood why it occurs in only a fraction of patients with a circulating monoclonal component and why it typically associates with lambda isotype and lambdaVI family light-chain proteins. To provide insights into these issues, we obtained complete nucleotide sequences of monoclonal V(lambda) regions from 55 consecutive unselected cases of primary amyloidosis and the results were compared with the light-chain expression profile of polyclonal marrow plasma cells from 3 healthy donors (a total of 264 sequences). We demonstrated that: (1) the lambdaIII family is the most frequently used both in amyloidosis (47%) and in polyclonality (43%); (2) both conditions are characterized by gene restriction; (3) a very skewed repertoire is a feature of amyloidosis, because just 2 germline genes belonging to the lambdaIII and lambdaVI families, namely 3r (22% of cases, lambdaIII) and 6a (20%, lambdaVI), contributed equally to encode 42% of amyloid V(lambda) regions; (4) these same 2 gene segments have a strong association with amyloidosis if their prevalences are compared with those in polyclonal conditions (3r, 8.3%, P =.024; 6a, 2.3%, P =.0008, chi2 test); (5) the J(lambda)2/3 segment, encoding the fourth framework region, appears to be slightly overrepresented in AL (83% versus 67%, P =.03), and this might be related to preferential J(lambda)2/3 rearrangement in amyloid (11 of 12 cases) versus polyclonal 3r light chains (13 of 22 cases). These findings demonstrate that V(lambda)-J(lambda) expression is more restricted in plasma cells from amyloidosis than from polyclonal bone marrow and identify 3r as a new disease-associated gene segment. Overusage of just 2 gene segments, 3r and 6a, can thus account for the lambda light-chain overrepresentation typical of this disorder.

Immunoglobulin light chain amyloidosis and the kidney

Immunoglobulin light chain amyloidosis and the kidney. Amyloidosis (AL) is a common cause of nephrotic syndrome in nondiabetic, nonhypertensive adults. All adult patients with nephrotic syndrome should have immunofixation of serum and urine as a screen. The finding of a monoclonal protein, particularly of lambda type, should lead to a subcutaneous fat aspirate or bone marrow biopsy to search for amyloid deposits. When the result of either test is positive, a kidney biopsy is unnecessary. The prognosis of patients who have renal amyloidosis depends on the concentration of serum creatinine at presentation and whether an echocardiographic evaluation demonstrates infiltrative cardiomyopathy. Most therapies are directed against the plasma cell dyscrasia present in all patients with AL and can include melphalan and prednisone, high-dose dexamethasone, and, most recently, peripheral blood stem cell transplantation.

Both the environment and somatic mutations govern the aggregation pathway of pathogenic immunoglobulin light chain

Deposition of monoclonal immunoglobulin light chain (LC) aggregates in tissues is the hallmark of a class of fatal diseases with no effective treatment. In the most prevalent diseases two different types of LC aggregates are observed: fibrillar deposits in LC amyloidosis (AL) and granular aggregates in LC deposition disease (LCDD). The mechanisms by which a given LC forms either type of aggregate are not understood. Although some LCs are more aggregation-prone than others, this does not appear to be due to specific sequence determinants, but more likely from global properties that can be introduced by multiple somatic mutations. Moreover, a single LC isotype can sometimes form both fibrillar and granular aggregates within the same patient. To better understand how the different aggregation pathways arise, we developed a series of in vitro assays to analyze the formation of distinct aggregate types. The recombinant kappa IV LC (SMA) assembles into fibrils when agitated. We now show that SMA can also form granular aggregates upon exposure to copper, and that this aggregation can occur not only in vitro, but also in cells. A constellation of somatic mutations, consisting of His89/His94/Gln96, is sufficient to confer sensitivity to copper on wild-type kappa IV proteins. The formation of both types of aggregates is inhibited by synthetic peptides derived from the LC variable domain. However, the peptide that inhibits fibrillar aggregation is different from the peptide that inhibits copper-induced aggregation. Thus, distinct molecular surfaces of the LC underly each type of aggregate. We conclude that both the intrinsic properties of the sequence and extrinsic conditions govern the aggregation pathway of a LC.

Amyloid fibril formation in microwell plates for screening of inhibitors

Fibril formation is the basis of amyloid production in a number of disease states, such as Alzheimer's disease, diabetes and immunocytic dyscrasias. Compounds that inhibit fibril formation could be directly relevant to the treatment of amyloid diseases, and may also provide a foundation for the development of interventions in other molecular condensation diseases ranging from sickle cell anemia to atherosclerosis. We developed an economical and convenient high-throughput method for screening compounds against fibril formation in microwell plates. Chalcones, flavonoids and biflavonoids were screened against fibril formation by a recombinant antibody variable domain (V1). Chalcones 6 and 14 were found to demonstrate inhibition at 0.1 microM in 79 microM of protein solution in both test tube and microwell plate assays. The concentration of protein in the microwell plate assay could be as low as 5 microM using ThT as a monitoring agent. Molecular modeling studies indicated that both compounds could be individually docked into a binding site at the monomer-monomer interface of the V(L) protein dimer. These studies suggested that these compounds could potentially stabilize the VL dimer and therefore reduce its tendency to form fibrils. These findings may provide the basis for a new therapeutic approach to prevent or treat amyloid diseases.

Counteracting effects of renal solutes on amyloid fibril formation by immunoglobulin light chains

In primary (light chain-associated) amyloidosis, immunoglobulin light chains deposit as amyloid fibrils in vital organs, especially the kidney. Because the kidney contains high concentrations of urea that can destabilize light chains as well as solutes such as betaine and sorbitol that serve as protein stabilizers, we investigated the effects of these solutes on in vitro amyloid fibril formation and thermodynamic stability of light chains. Two recombinant light chain proteins, one amyloidogenic and the other nonamyloidogenic, were used as models. For both light chains, urea enhanced fibril formation by reducing the nucleation lag time and diminished protein thermodynamic stability. Conversely, betaine or sorbitol increased thermodynamic stability of the proteins and partially inhibited fibril formation. These solutes also counteracted urea-induced reduction in protein thermodynamic stability and accelerated fibril formation. Betaine was more effective than sorbitol. A model is presented to explain how the thermodynamic effects of the solutes on protein state equilibria can alter nucleation lag time and, hence, fibril formation kinetics. Our results provide evidence that renal solutes control thermodynamic and kinetic stability of light chains and thus may modulate amyloid fibril formation in the kidney.

Novel approaches to the treatment of primary amyloidosis

Primary (AL, amyloid light-chain) amyloidosis is a plasma cell disorder in which deposits of amyloid light-chain protein cause progressive organ failure. It is important to recognise that amyloidosis is a dynamic process and chemotherapy-induced reduction of the activity of the plasma cell clone reduces the supply of the amyloid precursor protein and can result in a major regression of the deposits. The most common target organ is the kidney and renal amyloidosis manifests as proteinuria or nephrotic syndrome. Proteinuria is seen in three quarters of patients. Amyloid related nephrotic syndrome and renal failure are potentially reversible. Fatigue, congestive heart failure, hepatomegaly, peripheral neuropathy, orthostatic hypotension, carpal tunnel syndrome and macroglossia are other common features. The median survival is one to two years. Conventional-dose melphalan as standard treatment can prolong the median duration of survival by about ten months, but the clinical response rates with improvement of impaired organ function are low. Up-front high-dose chemotherapy with autologous peripheral blood stem cell transplantation is much more effective and can result in a major improvement in the clinical condition of patients. However, the toxicity related to this treatment can be relevant due to impaired organ function. Conventional-dose chemotherapy consisting of vincristine, doxorubicin and dexamethasone or high-dose dexamethasone or interferon-alpha are other possible approaches to treatment. The improvement of patient condition with an effective conventional-dose chemotherapy may increase the tolerability of high-dose chemotherapy and reduce transplantation related problems.

Antibody-mediated resolution of light chain-associated amyloid deposits

Primary light-chain-associated (AL) amyloidosis is characterized by the deposition in tissue of monoclonal light chains as fibrils. With rare exception, this process is seemingly irreversible and results in progressive organ dysfunction and eventually death. To determine whether immune factors can effect amyloid removal, we developed an experimental model in which mice were injected with amyloid proteins extracted from the spleens or livers of patients with AL amyloidosis. Notably, the resultant amyloidomas were rapidly resolved, as compared to controls, when animals received injections of an anti-light-chain monoclonal antibody having specificity for an amyloid-related epitope. The reactivity of this monoclonal antibody was not dependent on the V(L) or C(L) isotype of the fibril, but rather seemed to be directed toward a beta-pleated sheet conformational epitope expressed by AL and other amyloid proteins. The amyloidolytic response was associated with a pronounced infiltration of the amyloidoma with neutrophils and putatively involved opsonization of fibrils by the antibody, leading to cellular activation and release of proteolytic factors. The demonstration that AL amyloid resolution can be induced by passive administration of an amyloid-reactive antibody has potential clinical benefit in the treatment of patients with primary amyloidosis and other acquired or inherited amyloid-associated disorders.

Entrapping intermediates of thermal aggregation in alpha-helical proteins with low concentration of guanidine hydrochloride

Aggregation of proteins is a problem with serious medical implications and economic importance. To develop strategies for preventing aggregation, the mechanism(s) and pathways by which proteins aggregate must be characterized. In this study, the thermally induced aggregation processes of three alpha-helix proteins (myoglobin, cytochrome c, and lysozyme) in the presence and absence of 1.0 m guanidine hydrochloride (GdnHCl) were investigated by means of infrared spectroscopy. In the absence of GdnHCl, intensities of the alpha-helix bands (approximately 1656 cm(-1)) decrease as a function of temperature at above 50 degrees C. With myoglobin and cytochrome c, the loss of helix bands was accompanied by the appearance of two new bands at 1694 and 1623 cm(-1), indicative of the formation of intermolecular beta-sheet aggregates. For lysozyme, bands indicative of intermolecular beta-sheet aggregates did not appear in any significant intensity. In the presence of 1.0 m GdnHCl, two major intermediate states rich in 3(10)-helix (represented by the band at 1663 cm(-1)) and beta-turn structure (represented by the band at 1667 cm(-1)), respectively, were observed. These findings demonstrated that IR spectroscopic studies of protein aggregation using a combination of thermal and chemical denaturing factors could provide a means to populate and characterize aggregation intermediates.

The amino acid sequence of a monoclonal gamma 3-heavy chain from a patient with articular gamma-heavy chain deposition disease

Abnormal deposition of proteins, including monoclonal immunoglobulin gamma-heavy chains, may cause tissue damage and organ dysfunction. We here report the amino acid sequence of the free gamma-heavy chains present in serum and urine of the first reported case (patient G. L.) of synovial heavy chain deposition disease. The protein was heavily deleted and consisted of the hinge, in addition to the CH2 and CH3 domains, in a dimeric form, thus lacking its variable domain as well as the CH1 domain. The sequence was consistent with the gamma 3 subclass (gamma 3GL). Gm typing revealed the gamma 3 allotypes G3m(b0) and G3m(b1) in accordance with the residues Pro123, Phe128, Thr171 and Phe268 in gamma 3GL. Furthermore, the gamma 3GL molecule was glycosylated at Asn in position 129. Finally, the gamma 3GL protein was shown to contain a typical binding site for the first complement component, C1q, namely the residues Glu150, Lys152 and Lys154, with the potential of binding and activating complement, causing tissue damage following deposition.

Thermodynamic modulation of light chain amyloid fibril formation

To obtain further insight into the pathogenesis of amyloidosis and develop therapeutic strategies to inhibit fibril formation we investigated: 1) the relationship between intrinsic physical properties (thermodynamic stability and hydrogen-deuterium (H-D) exchange rates) and the propensity of human immunoglobulin light chains to form amyloid fibrils in vitro; and 2) the effects of extrinsically modulating these properties on fibril formation. An amyloid-associated protein readily formed amyloid fibrils in vitro and had a lower free energy of unfolding than a homologous nonpathological protein, which did not form fibrils in vitro. H-D exchange was much faster for the pathological protein, suggesting it had a greater fraction of partially folded molecules. The thermodynamic stabilizer sucrose completely inhibited fibril formation by the pathological protein and shifted the values for its physical parameters to those measured for the nonpathological protein in buffer alone. Conversely, urea sufficiently destabilized the nonpathological protein such that its measured physical properties were equivalent to those of the pathological protein in buffer, and it formed fibrils. Thus, fibril formation by light chains is predominantly controlled by thermodynamic stability; and a rational strategy to inhibit amyloidosis is to design high affinity ligands that specifically increase the stability of the native protein.

Is there a pathogenic link between gamma heavy chain disease and chronic arthritis?

In 1991, gamma heavy chain disease was diagnosed in a 43-year-old female, who 3 years earlier had contracted an erosive seronegative chronic arthropathy. In 1996, her lymphoproliferative disorder required treatment with melphalan and prednisolone. Laboratory studies revealed a gamma3 heavy chain monoclonal component in serum and urine. Massive localization of plasma cells and blasts with cytoplasmic or cell membrane staining for gamma3 chains, but no staining for light chains, was observed by immunohistochemical studies of bone marrow as well as affected synovial tissue. Large amounts of extracellular gamma3-chains were also deposited in the synovial membrane. This is the first documentation of gamma heavy chain deposition disease directly affecting articular structures. Whether it represents the primary pathogenic event followed by reactive inflammatory changes in the joints, or another example of gamma heavy chain disease preceded by chronic arthritis, remains elusive. Regardless, several common cellular and molecular mechanisms discussed here suggest a pathogenic link between the two disease processes.

pH-dependent fibrillogenesis of a VkappaIII Bence Jones protein

Disorders of immunoglobulin (Ig) synthesis that occur in malignant plasma-cell proliferation may result in either granular (LCDD) or fibrillar (AL) tissue deposition of light-chain monoclonal components. The structural features that govern the transition from soluble polypeptides to either fibrillar or granular conformational states remain undefined. Among the many factors presumed to play a role in these transitions the net charge of the molecule has been associated with folding conformation changes. The majority of the proteins involved in AL amyloidosis show acidic isoelectric points (pI 3.8-5.2), whereas most L chains with basic pIs deposit in granular patterns. In our studies a 12 kD VkappaIII fragment was purified as the main component of the fibrils isolated from myocardium and adipose tissue of the pericardium obtained post-mortem from an individual with systemic AL amyloidosis. An apparently identical 12 kD VL fragment with the same N-terminal sequence constituted the BJ protein present in the urine. This urinary protein exhibited strikingly cathodic electrophoretic mobility on agarose gels and lacked retention by anionic exchange chromatography matrices, indicative of a highly basic pI (>10). When it was subjected to in vitro fibril-formation experiments, the BJ protein adopted a fibrillar conformation only at acidic pHs, remaining aggregated but not fibrillar at physiological pH. The data indicate that a specific tissue deposition pattern involves not only structural properties of the protein but rather more complex mechanisms in which acidic micro-environments may contribute to the stabilization of amyloidogenic conformations.

Phase II trial of high-dose dexamethasone for untreated patients with primary systemic amyloidosis

Primary systemic amyloidosis is the disorder that results from the deposition of insoluble immunoglobulin light chain fragments. Patients seen within 30 days of diagnosis have a median survival of 13 months. Patients treated with melphalan and prednisone have a median survival of 17 months. There is a need for new therapies. A prospective study was undertaken of high-dose dexamethasone in the treatment of 25 patients with previously untreated primary systemic amyloidosis. Treatment was similar to that given to patients with multiple myeloma. In this cohort, three patients showed objective regression with organ-specific improvement of the disease. The median survival of the entire group was 13.8 months. High-dose dexamethasone is of occasional benefit in patients with amyloidosis but does not appear to be superior to melphalan and prednisone chemotherapy.

Differential diagnosis of monoclonal gammopathies

Several disorders are associated with a monoclonal immunoglobulin detected by serum or urine electrophoresis, the most common being a monoclonal gammopathy of undetermined significance, multiple myeloma, Waldenstrom's macroglobulinemia, and amyloidosis. The clinical features of these conditions, as well as other similar entities, are described in this review. The objective is to demonstrate the importance of electrophoretic studies in the differential diagnosis of plasma cell dyscrasias and in guiding the decision for rational therapies.

Pathophysiology of paraprotein production

Paraproteins or monoclonal proteins are the result of clonal B-cell or plasma cell proliferation of a malignant, premalignant or non-malignant nature. Monoclonal proteins may consist of intact immunoglobulin molecules or of heavy or light chains only. Depending on their rate of production and/or secretion they may accumulate in the serum and/or urine of patients. Their presence in the circulation may remain silent, as in monoclonal gammopathy of undetermined significance (MGUS), or may lead to clinical syndromes such as Hyperviscosity, Acrocyanosis, Cold hemagglutination, hemolysis and hemorrhagic manifestations. Their tissue deposition may be localized, with the kidney being the most frequent target as in Myeloma Cast Nephropathy or systemic, as in AL amyloidosis where heart, liver, nerves, tongue are usual targets, in addition to the kidneys.