Diagnostic and therapeutic potential of amyloid-reactive IgG antibodies contained in human sera

Cancer Immunotherapy and Medical Imaging Research Trends from 2003 to 2023: A Bibliometric Analysis

Purpose

With the rapid development of immunotherapy, cancer treatment has entered a new phase. Medical imaging, as a primary diagnostic method, is closely related to cancer immunotherapy. However, until now, there has been no systematic bibliometric analysis of the state of this field. Therefore, the main purpose of this article is to clarify the past research trajectory, summarize current research hotspots, reveal dynamic scientific developments, and explore future research directions.

Patients and Methods

A comprehensive search was conducted on the Web of Science Core Collection (WoSCC) database to identify publications related to immunotherapy specifically for the medical imaging of carcinoma. The search spanned the period from the year 2003 to 2023. Several analytical tools were employed. These included CiteSpace (6.2.4), and the Microsoft Office Excel (2016).

Results

By searching the database, a total of 704 English articles published between 2003 and 2023 were obtained. We have observed a rapid increase in the number of publications since 2018. The two most active countries are the United States (n=265) and China (n=170). Pittock, Sean J and Abu-sbeih, Hamzah are very concerned about the relationship between cancer immunotherapy and medical images and have published more academic papers (n = 5; n = 4). Among the top 10 co-cited authors, Topalian Sl (n=43) cited ranked first, followed by Graus F (n=40) cited. According to clustering, timeline, and burst word analysis, the results show that the current research focus is on "MRI", "deep learning", "tumor microenvironment" and so on.

Conclusion

Medical imaging and cancer immunotherapy are hot topics. The United States is the country with the most publications and the greatest influence in this field, followed by China. "MRI", "PET/PET-CT", "deep learning", "immune-related adverse events" and "tumor microenvironment" are currently hot research topics and potential targets.

Development and characterization of a prototypic pan-amyloid clearing agent - a novel murine peptide-immunoglobulin fusion

Introduction

Systemic amyloidosis is a progressive disorder characterized by the extracellular deposition of amyloid fibrils and accessory proteins in visceral organs and tissues. Amyloid accumulation causes organ dysfunction and is not generally cleared by the immune system. Current treatment focuses on reducing amyloid precursor protein synthesis and slowing amyloid deposition. However, curative interventions will likely also require removal of preexisting amyloid deposits to restore organ function. Here we describe a prototypic pan-amyloid binding peptide-antibody fusion molecule (mIgp5) that enhances macrophage uptake of amyloid.

Methods

The murine IgG1-IgG2a hybrid immunoglobulin with a pan amyloid-reactive peptide, p5, fused genetically to the N-terminal of the immunoglobulin light chain was synthesized in HEK293T/17 cells. The binding of the p5 peptide moiety was assayed using synthetic amyloid-like fibrils, human amyloid extracts and amyloid-laden tissues as substrates. Binding of radioiodinated mIgp5 with amyloid deposits in vivo was evaluated in a murine model of AA amyloidosis using small animal imaging and microautoradiography. The bioactivity of mIgp5 was assessed in complement fixation and in vitro phagocytosis assays in the presence of patient-derived amyloid extracts and synthetic amyloid fibrils as substrates and in the presence or absence of human serum.

Results

Murine Igp5 exhibited highly potent binding to AL and ATTR amyloid extracts and diverse types of amyloid in formalin-fixed tissue sections. In the murine model of systemic AA amyloidosis, 125I-mIgp5 bound rapidly and specifically to amyloid deposits in all organs, including the heart, with no evidence of non-specific uptake in healthy tissues. The bioactivity of the immunoglobulin Fc domain was uncompromised in the context of mIgp5 and served as an effective opsonin. Macrophage-mediated uptake of amyloid extract and purified amyloid fibrils was enhanced by the addition of mIgp5. This effect was exaggerated in the presence of human serum coincident with deposition of complement C5b9.

Conclusion

Immunostimulatory, amyloid-clearing therapeutics can be developed by incorporating pan-amyloid-reactive peptides, such as p5, as a targeting moiety. The immunologic functionality of the IgG remains intact in the context of the fusion protein. These data highlight the potential use of peptide-antibody fusions as therapeutics for all types of systemic amyloidosis.

Collagen inhibits phagocytosis of amyloid in vitro and in vivo and may act as a 'don't eat me' signal

BACKGROUND

Systemic amyloidosis refers to a group of protein misfolding disorders characterized by the extracellular deposition of amyloid fibrils in organs and tissues. For reasons heretofore unknown, amyloid deposits are not recognized by the immune system, and progressive deposition leads to organ dysfunction.

METHODS

In vitro and in vivo phagocytosis assays were performed to elucidate the impact of collagen and other amyloid associated proteins (eg serum amyloid p component and apolipoprotein E) had on amyloid phagocytosis. Immunohistochemical and histopathological staining regimens were employed to analyze collagen-amyloid interactions and immune responses.

RESULTS

Histological analysis of amyloid-laden tissue indicated that collagen is intimately associated with amyloid deposits. We report that collagen inhibits phagocytosis of amyloid fibrils by macrophages. Treatment of 15 patient-derived amyloid extracts with collagenase significantly enhanced amyloid phagocytosis. Preclinical mouse studies indicated that collagenase treatment of amyloid extracts significantly enhanced clearance as compared to controls, coincident with increased immune cell infiltration of the subcutaneous amyloid lesion.

CONCLUSIONS

These data suggest that amyloid-associated collagen serves as a 'don't eat me' signal, thereby hindering clearance of amyloid. Targeted degradation of amyloid-associated collagen could result in innate immune cell recognition and clearance of pathologic amyloid deposits.

Cardiovascular magnetic resonance in light-chain amyloidosis to guide treatment

AIMS

To assess the ability of cardiovascular magnetic resonance (CMR) to (i) measure changes in response to chemotherapy; (ii) assess the correlation between haematological response and changes in extracellular volume (ECV); and (iii) assess the association between changes in ECV and prognosis over and above existing predictors.

METHODS AND RESULTS

In total, 176 patients with cardiac AL amyloidosis were assessed using serial N-terminal pro-B-type natriuretic peptide (NT-proBNP), echocardiography, free light chains and CMR with T1 and ECV mapping at diagnosis and subsequently 6, 12, and 24 months after starting chemotherapy. Haematological response was graded as complete response (CR), very good partial response (VGPR), partial response (PR), or no response (NR). CMR response was graded by changes in ECV as progression (≥0.05 increase), stable (<0.05 change), or regression (≥0.05 decrease). At 6 months, CMR regression was observed in 3% (all CR/VGPR) and CMR progression in 32% (61% in PR/NR; 39% CR/VGPR). After 1 year, 22% had regression (all CR/VGPR), and 22% had progression (63% in PR/NR; 37% CR/VGPR). At 2 years, 38% had regression (all CR/VGPR), and 14% had progression (80% in PR/NR; 20% CR/VGPR). Thirty-six (25%) patients died during follow-up (40 ± 15 months); CMR response at 6 months predicted death (progression hazard ratio 3.82; 95% confidence interval 1.95-7.49; P < 0.001) and remained prognostic after adjusting for haematological response, NT-proBNP and longitudinal strain (P < 0.01).

CONCLUSIONS

Cardiac amyloid deposits frequently regress following chemotherapy, but only in patients who achieve CR or VGPR. Changes in ECV predict outcome after adjusting for known predictors.

Clinical characteristics and prognostic value of renal immune complex deposition in patients with light chain amyloidosis

Although patients with light chain amyloidosis (AL) may present with co-deposition of amyloid and immune complexes (ICs) in renal biopsies, data on clinical characteristics and prognostic value of renal IC deposition are limited. A total of 73 patients with AL amyloidosis who were newly diagnosed by renal biopsy in Xijing Hospital (Xi'an, China) were divided into two groups (IC and non-IC groups). As a result, renal IC deposition was found in 26% of patients. Patients with IC deposition were associated with more urinary protein excretion and lower serum albumin. Notably, patients in the non-IC group achieved higher hematological overall response rate (81.5% vs. 47.4%, p = 0.007) and ≥VGPR rate (75.9% vs. 39.8%, p = 0.004) compared with those in IC group. Renal response rate was also higher in the non-IC group (63% vs. 31.6%, p = 0.031). With the median follow-up time of 19 months, a significantly worse overall survival was observed in patients with the IC group as compared with those without renal IC deposition in the Kaplan-Meier analysis (p = 0.036). Further multivariate analysis demonstrated that renal immune complex deposition was associated with worse overall survival in patients with AL amyloidosis (HR 5.927, 95% CI 2.148-16.356, p = 0.001).

Cerebrospinal fluid and plasma distribution of anti-α-synuclein IgMs and IgGs in multiple system atrophy and Parkinson's disease

INTRODUCTION

Ubiquitous naturally occurring autoantibodies (nAbs) against alpha-synuclein (α-syn) may play important roles in the pathogenesis of Multiple System Atrophy (MSA) and Parkinson's disease (PD). Recently, we reported reduced high-affinity/avidity anti-α-syn nAbs levels in plasma from MSA and PD patients, along with distinct inter-group immunoglobulin (Ig)G subclass distributions. The extent to which these observations in plasma may reflect corresponding levels in the cerebrospinal fluid (CSF) is unknown.

METHODS

Using competitive and indirect ELISAs, we investigated the affinity/avidity of CSF anti-α-syn nAbs as well as the CSF and plasma distribution of IgG subclasses and IgM nAbs in a cross-sectional cohort of MSA and PD patients.

RESULTS

Repertoires of high-affinity/avidity anti-α-syn IgG nAbs were reduced in CSF samples from MSA and PD patients compared to controls. Furthermore, anti-α-syn IgM nAb levels were relatively lower in CSF and plasma from MSA patients but were reduced only in plasma from PD patients. Interestingly, anti-α-syn IgG subclasses presented disease-specific profiles both in CSF and plasma. Anti-α-syn IgG1, IgG2 and IgG3 levels were relatively increased in CSF of MSA patients, whereas PD patients showed increased anti-α-syn IgG2 and reduced anti-α-syn IgG4 levels.

CONCLUSIONS

Differences in the plasma/CSF distribution of anti-α-syn nAbs seem to be a common feature of synucleinopathies. Our data add further support to the notion that MSA and PD patients may have compromised immune reactivity towards α-syn. The differing α-syn-specific systemic immunological responses may reflect their specific disease pathophysiologies. These results are encouraging for further investigation of these immunological mechanisms in neurodegenerative diseases.

Anti-Aβ Antibodies and Cerebral Amyloid Angiopathy Complications

Cerebral amyloid angiopathy (CAA) corresponds to the deposition of amyloid material in the cerebral vasculature, leading to structural modifications of blood vessel walls. The most frequent form of sporadic CAA involves fibrillar β-amyloid peptide (Aβ) deposits, mainly the 40 amino acid form (Aβ_1-40), which are commonly found in the elderly with or without Alzheimer's disease. Sporadic CAA usually remains clinically silent. However, in some cases, acute complications either hemorrhagic or inflammatory can occur. Similar complications occurred after active or passive immunization against Aβ in experimental animal models exhibiting CAA, and in subjects with Alzheimer's disease during clinical trials. The triggering of these adverse events by active immunization and monoclonal antibody administration in CAA-bearing individuals suggests that analogous mechanisms could be involved during spontaneous CAA complications, drawing particular attention to the role of anti-Aβ antibodies. However, antibodies that react with several monomeric and aggregated forms of Aβ spontaneously occur in virtually all human individuals, hence being part of the "natural antibody" repertoire. Natural antibodies are usually described as having low-affinity and high cross-reactivity toward microbial components and autoantigens. Although frequently of the IgM class, they also belong to IgG and IgA isotypes. They likely display homeostatic functions and protective roles in aging. Until recently, the peculiar properties of these natural antibodies have hindered proper analysis of the Aβ-reactive antibody repertoire and the study of their implication in CAA complications. Herein, we review and comment the evidences of an auto-immune nature of spontaneous CAA complications, and discuss implications for forthcoming research and clinical practice.

Macrophage-Mediated Phagocytosis and Dissolution of Amyloid-Like Fibrils in Mice, Monitored by Optical Imaging

Light chain-associated amyloidosis is characterized by the extracellular deposition of amyloid fibrils in abdominothoracic organs, skin, soft tissue, and peripheral nerves. Phagocytic cells of the innate immune system appear to be ineffective at clearing the material; however, human light chain amyloid extract, injected subcutaneously into mice, is rapidly cleared in a process that requires neutrophil activity. To better elucidate the phagocytosis of light chain fibrils, a potential method of cell-mediated dissolution, amyloid-like fibrils were labeled with the pH-sensitive dye pHrodo red and a near infrared fluorophore. After injecting this material subcutaneously in mice, optical imaging was used to quantitatively monitor phagocytosis and dissolution of fibrils concurrently. Histologic evaluation of the residual fibril masses revealed the presence of CD68⁺, F4/80⁺, ionized calcium binding adaptor molecule 1^- macrophages containing Congo red-stained fibrils as well as neutrophil-associated proteins with no evidence of intact neutrophils. These data suggest an early infiltration of neutrophils, followed by extensive phagocytosis of the light chain fibrils by macrophages, leading to dissolution of the mass. Optical imaging of this novel murine model, coupled with histologic evaluation, can be used to study the cellular mechanisms underlying dissolution of synthetic amyloid-like fibrils and human amyloid extracts. In addition, it may serve as a test bed to evaluate investigational opsonizing agents that might serve as therapeutic agents for light chain-associated amyloidosis.

Hematological Malignancies and Arterial Thromboembolism

Established guidelines exist for prevention and treatment of venous thromboembolism in hematological malignancies, but none for arterial thromboembolism. However, arterial and venous thromboembolism share the same provoking features—including altered procoagulant factors and defective fibrinolytic system. The morbidity for arterial thromboembolism is increasing in hematological malignancies, with the advent of immunomodulatory and targeted therapy. However, survival rate for hematological malignancy is improving. Consequently, as patients with hematological malignancies live longer, comorbidities including diabetes, hypertension and dyslipidemia, may accentuate arterial thrombosis. Thus far, the scientific literature on prophylaxis and treatment for arterial thromboembolism in hematological malignancies is limited. This review highlights the pathogenesis, incidence and clinical features of arterial thromboembolism in hematological malignancies.

Bifunctional amyloid-reactive peptide promotes binding of antibody 11-1F4 to diverse amyloid types and enhances therapeutic efficacy

Amyloidosis is a malignant pathology associated with the formation of proteinaceous amyloid fibrils that deposit in organs and tissues, leading to dysfunction and severe morbidity. More than 25 proteins have been identified as components of amyloid, but the most common form of systemic amyloidosis is associated with the deposition of amyloid composed of Ig light chains (AL). Clinical management of amyloidosis focuses on reducing synthesis of the amyloid precursor protein. However, recently, passive immunotherapy using amyloid fibril-reactive antibodies, such as 11-1F4, to remove amyloid from organs has been shown to be effective at restoring organ function in patients with AL amyloidosis. However, 11-1F4 does not bind amyloid in all AL patients, as evidenced by PET/CT imaging, nor does it efficiently bind the many other forms of amyloid. To enhance the reactivity and expand the utility of the 11-1F4 mAb as an amyloid immunotherapeutic, we have developed a pretargeting "peptope" comprising a multiamyloid-reactive peptide, p5+14, fused to a high-affinity peptide epitope recognized by 11-1F4. The peptope, known as p66, bound the 11-1F4 mAb in vitro with subnanomolar efficiency, exhibited multiamyloid reactivity in vitro and, using tissue biodistribution and SPECT imaging, colocalized with amyloid deposits in a mouse model of systemic serum amyloid A amyloidosis. Pretreatment with the peptope induced 11-1F4 mAb accumulation in serum amyloid A deposits in vivo and enhanced 11-1F4-mediated dissolution of a human AL amyloid extract implanted in mice.

Immunoglobulin light chain amyloid aggregation

Light chain (AL) amyloidosis is a devastating, complex, and incurable protein misfolding disease. It is characterized by an abnormal proliferation of plasma cells (fully differentiated B cells) producing an excess of monoclonal immunoglobulin light chains that are secreted into circulation, where the light chains misfold, aggregate as amyloid fibrils in target organs, and cause organ dysfunction, organ failure, and death. In this article, we will review the factors that contribute to AL amyloidosis complexity, the findings by our laboratory from the last 16 years and the work from other laboratories on understanding the structural, kinetics, and thermodynamic contributions that drive immunoglobulin light chain-associated amyloidosis. We will discuss the role of cofactors and the mechanism of cellular damage. Last, we will review our recent findings on the high resolution structure of AL amyloid fibrils. AL amyloidosis is the best example of protein sequence diversity in misfolding diseases, as each patient has a unique combination of germline donor sequences and multiple amino acid mutations in the protein that forms the amyloid fibril.

Naturally occurring antibodies against serum amyloid A reduce IL-6 release from peripheral blood mononuclear cells

Serum amyloid A (SAA) is a sensitive inflammatory marker rapidly increased in response to infection, injury or trauma during the acute phase. Resolution of the acute phase and SAA reduction are well documented, however the exact mechanism remains elusive. Two inducible SAA proteins, SAA1 and SAA2, with their variants could contribute to systemic inflammation. While unconjugated human variant SAA1α is already commercially available, the variants of SAA2 are not. Antibodies against SAA have been identified in apparently healthy blood donors (HBDs) in smaller, preliminary studies. So, our objective was to detect anti-SAA and anti-SAA1α autoantibodies in the sera of 300 HBDs using ELISA, characterize their specificity and avidity. Additionally, we aimed to determine the presence of anti-SAA and anti-SAA1α autoantibodies in intravenous immunoglobulin (IVIg) preparations and examine their effects on released IL-6 from SAA/SAA1α-treated peripheral blood mononuclear cells (PBMCs). Autoantibodies against SAA and SAA1α had a median (IQR) absorbance OD (A₄₅₀) of 0.655 (0.262–1.293) and 0.493 (0.284–0.713), respectively. Both anti-SAA and anti-SAA1α exhibited heterogeneous to high avidity and reached peak levels between 41–50 years, then diminished with age in the oldest group (51–67 years). Women consistently exhibited significantly higher levels than men. Good positive correlation was observed between anti-SAA and anti-SAA1α. Both anti-SAA and anti-SAA1α were detected in IVIg, their fractions subsequently isolated, and shown to decrease IL-6 protein levels released from SAA/SAA1α-treated PBMCs. In conclusion, naturally occurring antibodies against SAA and anti-SAA1α could play a physiological role in down-regulating their antigen and proinflammatory cytokines leading to the resolution of the acute phase and could be an important therapeutic option in patients with chronic inflammatory diseases.

Cardiac amyloidosis

Systemic amyloidosis comprises an uncommon group of disorders caused by the extracellular deposition of misfolded proteins in various organs. Cardiac amyloid deposition, causing an infiltrative/restrictive cardiomyopathy, is a frequent feature of amyloidosis and a major determinant of survival. It may be the presenting feature of the disease or may be identified while investigating a patient presenting with other organ involvement. The need for a high index of suspicion and the critical importance of precise biochemical typing of the amyloid deposits is paramount in light of recent therapeutic advances that can significantly improve prognosis. Most cases of cardiac amyloidosis are of either transthyretin type, which may be acquired in older individuals or inherited in younger patients, or acquired monoclonal immunoglobulin light chain (AL) type. This article aims to review recent developments in diagnosis and management of cardiac amyloidosis.

Extracellular volume with bolus-only technique in amyloidosis patients: Diagnostic accuracy, correlation with other clinical cardiac measures, and ability to track changes in amyloid load over time

BACKGROUND

Extracellular volume (ECV) by T₁ mapping requires the contrast agent distribution to be at equilibrium. This can be achieved either definitively with a primed contrast infusion (infusion ECV), or sufficiently with a delay postbolus (bolus-only ECV). For large ECV, the bolus-only approach measures higher than the infusion ECV, causing some uncertainty in diseases such as amyloidosis.

PURPOSE

To characterize the relationship between the bolus-only and current gold-standard infusion ECV in patients with amyloidosis.

STUDY TYPE

Bolus-only and infusion ECV were prospectively measured.

POPULATION

In all, 186 subjects with systemic amyloidosis attending our clinic and 23 subjects with systemic amyloidosis who were participating in an open-label, two-part, dose-escalation, phase 1 trial.

FIELD STRENGTH

Avanto 1.5T, Siemens Medical Solutions, Erlangen, Germany.

ASSESSMENT

Bolus-only and infusion ECV were measured in all subjects using shortened modified Look-Locker inversion recovery (ShMOLLI) T₁ mapping sequence.

STATISTICAL TESTS

Pearson correlation coefficient (r); Bland-Altman; receiver operating characteristic (ROC) curve analysis. Linear regression model with a fractional polynomial transformation.

RESULTS

The difference between the bolus-only and infusion myocardial ECV increased as the average of the two measures increased, with the bolus-ECV measuring higher. For an average ECV of 0.4, the difference was 0.013. The 95% limits of agreement for the two methods, after adjustment for the bias, were ±0.056. However, cardiac diagnostic accuracy was comparable (bolus-only vs. infusion ECV area under the curve [AUC] = 0.839 vs. 0.836), as were correlations with other clinical cardiac measures, and, in the trial patients, the ability to track changes in the liver/spleen with therapy.

DATA CONCLUSION

In amyloidosis, with large ECVs, the bolus-only technique reads higher than the infusion technique, but clinical performance by any measure is the same. Given the work-flow advantages, these data suggest that the bolus-only approach might be acceptable for amyloidosis, and might support its use as a surrogate endpoint in future clinical trials.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2018;47:1677-1684.

Emerging therapeutic targets currently under investigation for the treatment of systemic amyloidosis

INTRODUCTION

Systemic amyloidosis occurs when one of a growing list of circulating proteins acquires an abnormal fold, aggregates and gives rise to extracellular amyloid deposits in different body sites, leading to organ dysfunction and eventually death. Current approaches are mainly aimed at lowering the supply of the amyloidogenic precursor or at stabilizing it in a non-amyloidogenic state, thus interfering with the initial phases of amyloid formation and toxicity. Areas covered: Improved understanding of the pathophysiology is indicating novel steps and molecules that could be therapeutically targeted. Here, we will review emerging molecular targets and therapeutic approaches against the main forms of systemic amyloidosis at the early preclinical level. Expert opinion: Conspicuous efforts in drug design and drug discovery have provided an unprecedented list of potential new drugs or therapeutic strategies, from gene-based therapies to small molecules and peptides, from novel monoclonal antibodies to engineered cell-based therapies. The challenge will now be to validate and optimize the most promising candidates, cross the bridge from the preclinical phase to the clinics and identify, through innovative trials design, the safest and most effective combination therapies, striving for a better care, possibly a definitive cure for these diseases.

A review on protein misfolding, aggregation and strategies to prevent related ailments

This review aims to highlight the fundamental mechanism of protein misfolding leading to protein aggregation and associated diseases. It also aims to anticipate novel therapeutic strategies with which to prevent or treat these highly debilitating conditions linked to these pathologies. The failure of a protein to correctly fold de novo or to remain correctly folded can have profound consequences on a living system especially when the cellular quality control processes fail to eliminate the rogue proteins. The core cause of over 20 different human diseases which have now been designated as 'conformational diseases' including neurodegenerative diseases such as Alzheimer's disease (AD), Huntington's disease (HD) and Parkinson's disease (PD) etc. A comprehensive study on protein misfolding, aggregation, and the outcomes of the effects of cytotoxic aggregates will lead to understand the aggregation-mediated cell toxicity and serves as a foundation for future research in development of promising therapies and drugs. This review has also shed light on the mechanism of protein misfolding which leads to its aggregation and hence the neurodegeneration. From these considerations, one could also envisage the possibility that protein aggregation may be exploited by nature to perform specific physiological functions in differing biological contexts.

Demonstration of safety of intravenous immunoglobulin in geriatric patients in a long-term, placebo-controlled study of Alzheimer's disease

INTRODUCTION

We present safety results from a study of Gammagard Liquid intravenous immunoglobulin (IGIV) in patients with probable Alzheimer's disease.

METHODS

This was a placebo-controlled double-blind study. Subjects were randomized to 400 mg/kg (n = 127), 200 mg/kg (n = 135) IGIV, or to 0.25% human albumin (n = 121) administered every 2 weeks ± 7 days for 18 months.

RESULTS

Elevated risk ratios of IGIV versus placebo included chills (3.85) in 9.5% of IGIV-treated subjects (all doses), compared to 2.5% of placebo-treated subjects, and rash (3.08) in 15.3% of IGIV-treated subjects versus 5.0% of subjects treated with placebo. Subjects in the highest IGIV dose group had the lowest proportion of SAEs considered related to product (2 of 127 [1.6%]). Subjects treated with IGIV experienced a lower rate of respiratory and all other infections compared to placebo.

DISCUSSION

IGIV-treated subjects did not experience higher rates of renal failure, lung injury, or thrombotic events than the placebo group. There were no unexpected safety findings. IGIV was well tolerated throughout 18 months of treatment in subjects aged 50-89 years.

Immunotherapeutic Approaches Targeting Amyloid-β, α-Synuclein, and Tau for the Treatment of Neurodegenerative Disorders

Disease-modifying alternatives are sorely needed for the treatment of neurodegenerative disorders, a group of diseases that afflict approximately 50 million Americans annually. Immunotherapy is one of the most developed approaches in this direction. Vaccination against amyloid-β, α-synuclein, or tau has been extensively explored, specially as the discovery that these proteins may propagate cell-to-cell and be accessible to antibodies when embedded into the plasma membrane or in the extracellular space. Likewise, the use of passive immunization approaches with specific antibodies against abnormal conformations of these proteins has also yielded promising results. The clinical development of immunotherapies for Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, dementia with Lewy bodies, and other neurodegenerative disorders is a field in constant evolution. Results to date suggest that immunotherapy is a promising therapeutic approach for neurodegenerative diseases that progress with the accumulation and prion-like propagation of toxic protein aggregates. Here we provide an overview of the most novel and relevant immunotherapeutic advances targeting amyloid-β in Alzheimer’s disease, α-synuclein in Alzheimer’s disease and Parkinson’s disease, and tau in Alzheimer’s disease and frontotemporal dementia.

[Pathological and clinical correlations in renal AA amyloidosis: A Moroccan series of 30 cases]

OBJECTIVE

Study of histological and clinical correlations of 30 cases of renal amyloidosis AA diagnosed between November 2010 and December 2012.

RESULTS

The main causes associated with amyloidosis AA were represented by chronic infectious diseases (60%). Nephrotic syndrome and renal failure were observed in 94% and 73% respectively. The distribution of amyloid deposits: 90% of patients had a glomerular form and 10% had a vascular form. Inflammatory reaction associated with AA renal amyloidosis was present in 50% of cases. This inflammation was observed near amyloid deposits associated with a deposition of immunoglobulin chains and/or complement factors.

CONCLUSION

Our study confirms the predominance of AA amyloidosis complicating chronic infectious diseases, especially tuberculosis. Our data point out a relationship between the morphology of renal AA amyloidosis, its clinical presentation and prognosis.

IgG Conformer's Binding to Amyloidogenic Aggregates

Amyloid-reactive IgGs isolated from pooled blood of normal individuals (pAbs) have demonstrated clinical utility for amyloid diseases by in vivo targeting and clearing amyloidogenic proteins and peptides. We now report the following three novel findings on pAb conformer's binding to amyloidogenic aggregates: 1) pAb aggregates have greater activity than monomers (HMW species > dimers > monomers), 2) pAbs interactions with amyloidogenic aggregates at least partially involves unconventional (non-CDR) interactions of F(ab) regions, and 3) pAb's activity can be easily modulated by trace aggregates generated during sample processing. Specifically, we show that HMW aggregates and dimeric pAbs present in commercial preparations of pAbs, intravenous immunoglobulin (IVIg), had up to ~200- and ~7-fold stronger binding to aggregates of Aβ and transthyretin (TTR) than the monomeric antibody. Notably, HMW aggregates were primarily responsible for the enhanced anti-amyloid activities of Aβ- and Cibacron blue-isolated IVIg IgGs. Human pAb conformer's binding to amyloidogenic aggregates was retained in normal human sera, and mimicked by murine pAbs isolated from normal pooled plasmas. An unconventional (non-CDR) component to pAb's activity was indicated from control human mAbs, generated against non-amyloid targets, binding to aggregated Aβ and TTR. Similar to pAbs, HMW and dimeric mAb conformers bound stronger than their monomeric forms to amyloidogenic aggregates. However, mAbs had lower maximum binding signals, indicating that pAbs were required to saturate a diverse collection of binding sites. Taken together, our findings strongly support further investigations on the physiological function and clinical utility of the inherent anti-amyloid activities of monomeric but not aggregated IgGs.

A human monoclonal IgG that binds aβ assemblies and diverse amyloids exhibits anti-amyloid activities in vitro and in vivo

Alzheimer's disease (AD) and familial Danish dementia (FDD) are degenerative neurological diseases characterized by amyloid pathology. Normal human sera contain IgG antibodies that specifically bind diverse preamyloid and amyloid proteins and have shown therapeutic potential in vitro and in vivo. We cloned one of these antibodies, 3H3, from memory B cells of a healthy individual using a hybridoma method. 3H3 is an affinity-matured IgG that binds a pan-amyloid epitope, recognizing both Aβ and λ Ig light chain (LC) amyloids, which are associated with AD and primary amyloidosis, respectively. The pan-amyloid-binding properties of 3H3 were demonstrated using ELISA, immunohistochemical studies, and competition binding assays. Functional studies showed that 3H3 inhibits both Aβ and LC amyloid formation in vitro and abrogates disruption of hippocampal synaptic plasticity by AD-patient-derived soluble Aβ in vivo. A 3H3 single-chain variable fragment (scFv) retained the binding specificity of the 3H3 IgG and, when expressed in the brains of transgenic mice using an adeno-associated virus (AAV) vector, decreased parenchymal Aβ amyloid deposition in TgCRND8 mice and ADan (Danish Amyloid) cerebral amyloid angiopathy in the mouse model of FDD. These data indicate that naturally occurring human IgGs can recognize a conformational, amyloid-specific epitope and have potent anti-amyloid activities, providing a rationale to test their potential as antibody therapeutics for diverse neurological and other amyloid diseases.

AA amyloidosis: pathogenesis and targeted therapy

The understanding of why and how proteins misfold and aggregate into amyloid fibrils has increased considerably during recent years. Central to amyloid formation is an increase in the frequency of the β-sheet structure, leading to hydrogen bonding between misfolded monomers and creating a fibril that is comparably resistant to degradation. Generation of amyloid fibrils is nucleation dependent, and once formed, fibrils recruit and catalyze the conversion of native molecules. In AA amyloidosis, the expression of cytokines, particularly interleukin 6, leads to overproduction of serum amyloid A (SAA) by the liver. A chronically high plasma concentration of SAA results in the aggregation of amyloid into cross-β-sheet fibrillar deposits by mechanisms not fully understood. Therefore, AA amyloidosis can be thought of as a consequence of long-standing inflammatory disease. This review summarizes current knowledge about AA amyloidosis. The systemic amyloidoses have been regarded as intractable conditions, but improvements in the understanding of fibril composition and pathogenesis over the past decade have led to the development of a number of different therapeutic approaches with promising results.

Intravenous immunoglobulin for the treatment of Alzheimer's disease: current evidence and considerations

Alzheimer's disease (AD) is a devastating neurodegenerative form of dementia with increasing incidence rates in most countries. AD is characterized by amyloid plaques and neurofibrillary tangles in the brains of AD individuals accompanied by global neuronal loss. The peptide amyloid-β (Aβ) aggregates to amyloid plaques in AD brains. As a result, many therapeutic approaches target Aβ. Human plasma and the plasma product intravenous immunoglobulin (IVIG) contain naturally-occurring anti-Aβ antibodies (Nabs-Aβ) that appear to reduce risks of developing AD. IVIG sequesters Aβ and thus interferes with AD progression. This study reviews the role of different Aβ species, Nabs-Aβ, preclinical data, and clinical studies of IVIG as potential AD treatments. The focus of this study is the outcomes of a recent Gammaglobulin Alzheimer's Partnership Phase III trial that did not reach primary endpoints, as well as efforts to compare IVIG with current anti-Aβ monoclonals such as bapineuzumab, solanezumab, and BIIB037. Moreover, this study critically examines current market and ethical consequences of potential off-label uses of IVIG, limits in IVIG supply, and subsequent challenges.

Safety and tolerability of immune globulin intravenous (human), 10% solution in Japanese subjects with mild to moderate Alzheimer's disease

BACKGROUND

Immune globulin intravenous (IGIV), 10% is a donor-derived polyclonal human immunoglobulin G antibody mixture that has potent immune modulatory properties and contains conformation selective anti-amyloid antibodies. We evaluated the safety and tolerability of multiple doses of IGIV, 10% in Japanese patients with mild to moderate Alzheimer's disease.

METHODS

Among the 16 subjects, 12 subjects were assigned to the IGIV group and 4 subjects to the placebo group. Subjects received a total of six infusions of either IGIV at a dose of 0.2 or 0.4 g/kg, or placebo every 2 weeks.

RESULTS

A total of 33 treatment-emergent adverse events (TEAE) occurred in 14 subjects: 13 TEAE in five subjects in both the IGIV 0.2 and 0.4 g/kg groups, and 7 TEAE in four subjects in the placebo group. The most common TEAE in the IGIV subjects were nasopharyngitis, injection-site swelling, and erythema. All 26 TEAE in the IGIV group were considered to be mild. Only one mild TEAE (rash) was considered to be possibly related to the study drug. There were no significant differences in incidence of TEAE between the treatment groups. Four serious TEAE were reported, and all of these were considered to be unrelated to the study treatment. Other assessments related to safety revealed neither clinically significant abnormal values nor findings in the study.

CONCLUSION

IGIV is generally safe and well tolerated with multiple intravenous infusions at doses of 0.2 g/kg and 0.4 g/kg in Japanese patients with mild to moderate Alzheimer's disease.

Update on treatment of light chain amyloidosis

Light chain amyloidosis is the most common type of amyloidosis as a consequence of protein misfolding of aggregates composed of amyloid fibrils. The clinical features are dependent on the organs involved, typically cardiac, renal, hepatic, peripheral and autonomic neuropathy and soft tissue. A tissue biopsy or fat aspirate is needed to confirm the presence/type of amyloid and prognostic tools are important in a risk stratified approach to treatment. Autologous stem cell transplant eligibility should be assessed at baseline, weighing the reversible or non-reversible contraindications, toxicity of treatment and chemotherapy alternatives available. Chemotherapy options include melphalan, thalidomide, bortezomib, lenalidomide, bendamustine in combination with dexamethasone. Many studies have explored these treatment modalities, with ongoing debate about the optimal first line and sequential treatment thereafter. Attaining a very good partial response or better is the treatment goal coupled with early assessment central to optimizing treatment. One major challenge remains increasing the awareness of this disease, frequently diagnosed late as the presenting symptoms mimic many other medical conditions. This review focuses on the treatments for light chain amyloidosis, how these treatments have evolved over the years, improved patient risk stratification, toxicities encountered and future directions.

Biomarkers in amyloid-β immunotherapy trials in Alzheimer's disease

Drug candidates directed against amyloid-β (Aβ) are mainstream in Alzheimer's disease (AD) drug development. Active and passive Aβ immunotherapy is the principle that has come furthest, both in number and in stage of clinical trials. However, an increasing number of reports on major difficulties in identifying any clinical benefit in phase II-III clinical trials on this type of anti-Aβ drug candidates have caused concern among researchers, pharmaceutical companies, and other stakeholders. This has provided critics of the amyloid cascade hypothesis with fire for their arguments that Aβ deposition may merely be a bystander, and not the cause, of the disease or that the amyloid hypothesis may only be valid for the familial form of AD. On the other hand, most researchers argue that it is the trial design that will need refinement to allow for identifying a positive clinical effect of anti-Aβ drugs. A consensus in the field is that future trials need to be performed in an earlier stage of the disease and that biomarkers are essential to guide and facilitate drug development. In this context, it is reassuring that, in contrast to most brain disorders, research advances in the AD field have led to both imaging (magnetic resonance imaging (MRI) and PET) and cerebrospinal fluid (CSF) biomarkers for the central pathogenic processes of the disease. AD biomarkers will have a central role in future clinical trials to enable early diagnosis, and Aβ biomarkers (CSF Aβ42 and amyloid PET) may be essential to allow for testing a drug on patients with evidence of brain Aβ pathology. Pharmacodynamic Aβ and amyloid precursor protein biomarkers will be of use to verify target engagement of a drug candidate in humans, thereby bridging the gap between mechanistic data from transgenic AD models (that may not be relevant to the neuropathology of human AD) and large and expensive phase III trials. Last, downstream biomarker evidence (CSF tau proteins and MRI volumetry) that the drug ameliorates neurodegeneration will, together with beneficial clinical effects on cognition and functioning, be essential for labeling an anti-Aβ drug as disease modifying.

Intravenous immunglobulin binds beta amyloid and modifies its aggregation, neurotoxicity and microglial phagocytosis in vitro

Intravenous Immunoglobulin (IVIG) has been proposed as a potential therapeutic for Alzheimer's disease (AD) and its efficacy is currently being tested in mild-to-moderate AD. Earlier studies reported the presence of anti-amyloid beta (Aβ) antibodies in IVIG. These observations led to clinical studies investigating the potential role of IVIG as a therapeutic agent in AD. Also, IVIG is known to mediate beneficial effects in chronic inflammatory and autoimmune conditions by interfering with various pathological processes. Therefore, we investigated the effects of IVIG and purified polyclonal Aβ -specific antibodies (pAbs-Aβ) on aggregation, toxicity and phagocytosis of Aβ in vitro, thus elucidating some of the potential mechanisms of action of IVIG in AD patients. We report that both IVIG and pAbs-Aβ specifically bound to Aβ and inhibited its aggregation in a dose-dependent manner as measured by Thioflavin T assay. Additionally, IVIG and the purified pAbs-Aβ inhibited Aβ-induced neurotoxicity in the SH-SY5Y human neuroblastoma cell line and prevented Aβ binding to rat primary cortical neurons. Interestingly, IVIG and pAbs-Aβ also increased the number of phagocytosing cells as well as the amount of phagocytosed fibrillar Aβ by BV-2 microglia. Phagocytosis of Aβ depended on receptor-mediated endocytosis and was accompanied by upregulation of CD11b expression. Importantly, we could also show that Privigen dose-dependently reversed Aβ-mediated LTP inhibition in mouse hippocampal slices. Therefore, our in vitro results suggest that IVIG may have an impact on different processes involved in AD pathogenesis, thereby promoting further understanding of the effects of IVIG observed in clinical studies.

Efficient amyloid A clearance in the absence of immunoglobulins and complement factors

Amyloid A amyloidosis is a protein misfolding disease characterized by deposition of extracellular aggregates derived from the acute-phase reactant serum amyloid A protein. If untreated, amyloid A amyloidosis leads to irreversible damage of various organs, including the kidneys, liver, and heart. Amyloid A deposits regress upon reduction of serum amyloid A concentration, indicating that the amyloid can be efficiently cleared by natural mechanisms. Clearance was proposed to be mediated by humoral immune responses to amyloid. Here, we report that amyloid clearance in mice lacking complement factors 3 and 4 (C3C4(-/-)) was equally efficient as in wild-type mice (C57BL/6), and was only slightly delayed in agammaglobulinemic mice (J(H-/-)). Hence, antibodies or complement factors are not necessary for natural amyloid clearance, implying the existence of alternative physiological pathways for amyloid removal.

Human anti-Aβ IgGs target conformational epitopes on synthetic dimer assemblies and the AD brain-derived peptide

Soluble non-fibrillar assemblies of amyloid-beta (Aβ) and aggregated tau protein are the proximate synaptotoxic species associated with Alzheimer's disease (AD). Anti-Aβ immunotherapy is a promising and advanced therapeutic strategy, but the precise Aβ species to target is not yet known. Previously, we and others have shown that natural human IgGs (NAbs) target diverse Aβ conformers and have therapeutic potential. We now demonstrate that these antibodies bound with nM avidity to conformational epitopes on plate-immobilized synthetic Aβ dimer assemblies, including synaptotoxic protofibrils, and targeted these conformers in solution. Importantly, NAbs also recognized Aβ extracted from the water-soluble phase of human AD brain, including species that migrated on denaturing PAGE as SDS-stable dimers. The critical reliance on Aβ's conformational state for NAb binding, and not a linear sequence epitope, was confirmed by the antibody's nM reactivity with plate-immobilized protofibrills, and weak uM binding to synthetic Aβ monomers and peptide fragments. The antibody's lack of reactivity against a linear sequence epitope was confirmed by our ability to isolate anti-Aβ NAbs from intravenous immunoglobulin using affinity matrices, immunoglobulin light chain fibrils and Cibacron blue, which had no sequence similarity with the peptide. These findings suggest that further investigations on the molecular basis and the therapeutic/diagnostic potential of anti-Aβ NAbs are warranted.

A clinicopathological analysis in a large cohort of Chinese patients with renal amyloid light-chain amyloidosis

BACKGROUND

The aim of the study is to investigate the association between clinical and pathological features in a large cohort of Chinese patients with renal immunoglobulin light-chain amyloidosis (AL).

METHODS

A series of 186 patients with renal AL amyloidosis diagnosed between 1990 and 2011 were retrospectively reviewed. The extent of amyloid deposition in glomeruli, blood vessels and tubulointerstitium were evaluated semiquantitatively. The renal amyloid load was defined by the sum of glomerular, vascular and interstitial deposits. The associations between the clinical manifestations and pathological features were analyzed.

RESULTS

The extent of glomerular amyloid deposition was positively correlated with the level of proteinuria. Patients with codeposition of amyloid and immune complexes (ICs) in glomeruli had higher levels of proteinuria than those without ICs. Advanced glomerular amyloid deposition was an independent pathological factor associated with renal insufficiency at diagnosis. The degree of vascular amyloid (VA) deposition was positively correlated with cardiac involvement and hepatic involvement. Patients with AL-κ showed a higher prevalence of hepatic involvement and more severe VA deposition than patients with AL-λ. High renal amyloid load independently predicted the increased risk for overall death after adjusting for recognized confounders.

CONCLUSIONS

The degree and localization of amyloid deposits in the kidney of AL patients were associated with the degree of proteinuria and renal insufficiency, as well as extrarenal organs involvement. There were some differences between AL-κ and AL -λ in clinical and pathological characteristics. The renal amyloid load was an independent predictor for overall mortality.

Rational design of potent domain antibody inhibitors of amyloid fibril assembly

Antibodies hold significant potential for inhibiting toxic protein aggregation associated with conformational disorders such as Alzheimer's and Huntington's diseases. However, near-stoichiometric antibody concentrations are typically required to completely inhibit protein aggregation. We posited that the molecular interactions mediating amyloid fibril formation could be harnessed to generate antibodies with potent antiaggregation. Here we report that grafting small amyloidogenic peptides (6-10 residues) into the complementarity-determining regions of a single-domain (V(H)) antibody yields potent domain antibody inhibitors of amyloid formation. Grafted AMyloid-Motif AntiBODIES (gammabodies) presenting hydrophobic peptides from Aβ (Alzheimer's disease), α-Synuclein (Parkinson's disease), and islet amyloid polypeptide (type 2 diabetes) inhibit fibril assembly of each corresponding polypeptide at low substoichiometric concentrations (1:10 gammabody:monomer molar ratio). In contrast, sequence- and conformation-specific antibodies that were obtained via immunization are unable to prevent fibrillization at the same substoichiometric concentrations. Gammabodies prevent amyloid formation by converting monomers and/or fibrillar intermediates into small complexes that are unstructured and benign. We expect that our antibody design approach--which eliminates the need for immunization or screening to identify sequence-specific domain antibody inhibitors--can be readily extended to generate potent aggregation inhibitors of other amyloidogenic polypeptides linked to human disease.

Correlation between protective immunity to α-synuclein aggregates, oxidative stress and inflammation

OBJECTIVE

Protein aggregation leading to central amyloid deposition is implicated in Parkinson's disease (PD). During disease progression, inflammation and oxidative stress may well invoke humoral immunity against pathological aggregates of PD-associated α-synuclein. The aim was to investigate any possible concurrence between autoimmune responses to α-synuclein monomers, oligomers or fibrils with oxidative stress and inflammation.

METHODS

The formation of α-synuclein amyloid species was assessed by thioflavin-T assay and atomic force microscopy was employed to confirm their morphology. Serum autoantibody titers to α-synuclein conformations were determined by ELISA. Enzyme activity and concentrations of oxidative stress/inflammatory indicators were evaluated by enzyme and ELISA protocols.

RESULTS

In PD patient sera, a differential increase in autoantibody titers to α-synuclein monomers, toxic oligomers or fibrils was associated with boosted levels of the pro-inflammatory cytokine interleukin-6 and tumour necrosis factor-α, but a decrease in interferon-γ concentration. In addition, levels of malondialdehyde were elevated whilst those of glutathione were reduced along with decrements in the activity of the antioxidants: superoxide dismutase, catalase and glutathione transferase.

CONCLUSIONS

It is hypothesized that the generation of α-synuclein amyloid aggregates allied with oxidative stress and inflammatory reactions may invoke humoral immunity protecting against dopaminergic neuronal death. Hence, humoral immunity is a common integrative factor throughout PD progression which is directed towards prevention of further neurodegeneration, so potential treatment strategies should attempt to maintain PD patient immune status.

AA-Amyloid is cleared by endogenous immunological mechanisms

OBJECTIVE

AA amyloidosis is a complication to longstanding inflammatory diseases, but reduction of amyloid mass has been reported as the inflammation ceases. Not much is known about the endogenous factors that contribute to this amyloid resolution. Herein, we describe the dynamics of amyloid degradation and resolution in experimental murine AA-amyloidosis.

METHODS

AA-amyloidosis was induced in mice with injections of amyloid enhancing factor (AEF) and by inflammation induced with injections of silver nitrate. Resolution of amyloid deposits was monitored over time.

RESULTS

Virtually all amyloid was cleared within 34 weeks. Using the ELISA-technique, antibodies directed against protein AA were detected in animals during amyloid clearance phase and macrophages were shown to internalize amyloid. Also, passive immunization with an amyloid specific monoclonal antibody, produced by a B-cell clone recovered from an animal with advanced AA-amyloidosis, reduced amyloid development in murine AA-amyloidosis.

CONCLUSION

Immunoglobulins co-localize with amyloid deposits and can contribute to amyloid degradation by Fc-receptor mediated phagocytosis, and should be considered key players in the degradation process.

Amyloid diseases of the heart: current and future therapies

Amyloid diseases in man are caused by as many as 23 different pre-cursor proteins already described. Cardiologists predominantly encounter three main types of amyloidosis that affect the heart: light chain (AL) amyloidosis, senile systemic amyloidosis (SSA) and hereditary amyloidosis, most commonly caused by a mutant form of transthyretin. In the third world, secondary amyloid (AA) is more prevalent, due to chronic infections and inadequately treated inflammatory conditions. Much less common, are the non-transthyretin variants, including mutations of fibrinogen, the apolipoproteins apoA1 and apoA2 and gelsolin. These rarer types do not usually cause significant cardiac compromise. Occurring worldwide, later in life and of less clinical significance, isolated atrial amyloid (IAA) also involves the heart. Heart involvement by amyloid often has devastating consequences. Clinical outcome depends on amyloid type, the extent of systemic involvement and the treatment options available. An exact determination of amyloid type is critical to appropriate therapy. In this review we describe the different approaches required to treat this spectrum of amyloid cardiomyopathies.

Immunoglobulin light chain, Blimp-1 and cytochrome P4501B1 peptides as potential vaccines for AL amyloidosis

Amyloid light chain (AL) amyloidosis is a lethal disorder characterized by the pathologic deposition of clonal plasma cell-derived, fibrillogenic immunoglobulin light chains in vital organs. Current chemotherapeutic regimens are problematic in patients with compromised organ function and are not effective for all patients. Here, a platform of computer-based prediction and preclinical mouse modeling was used to begin development of a complementary, immunotherapeutic approach for AL amyloidosis. Three peptide/MHC I-binding algorithms identified immunogenic peptides from three AL plasma cell-associated proteins: (1) amyloidogenic λ6 light chains, (2) CYP1B1, a universal tumor antigen hyper-expressed in AL plasma cells and (3) B lymphocyte-induced maturation protein 1 (Blimp-1), a transcription factor required for plasma cell differentiation. The algorithms correctly predicted HLA-A(*)0201-binding native and heteroclitic peptides. In HLA-A2 transgenic mice, these peptides, given individually or in combination, induced potent CTL which kill peptide-loaded human lymphoma cells and/or lymphoma cells producing target protein. Blimp-1 peptide-immunized mice exhibited a reduced percentage of splenic, lymph node and bone marrow plasma cells and a decrease in the absolute number of splenic plasma cells demonstrating (1) presentation of target peptide by endogenous plasma cells and (2) appropriate CTL homing to lymphoid organs followed by killing of target plasma cells. These studies suggest that AL amyloidosis, with its relatively low tumor cell burden, may be an attractive target for peptide-based multivalent vaccines.

Inhibition of amyloid formation

Amyloid is aggregated protein in the form of insoluble fibrils. Amyloid deposition in human tissue-amyloidosis-is associated with a number of diseases including all common dementias and type II diabetes. Considerable progress has been made to understand the mechanisms leading to amyloid formation. It is, however, not yet clear by which mechanisms amyloid and protein aggregates formed on the path to amyloid are cytotoxic. Strategies to prevent protein aggregation and amyloid formation are nevertheless, in many cases, promising and even successful. This review covers research on intervention of amyloidosis and highlights several examples of how inhibition of protein aggregation and amyloid formation has been achieved in practice. For instance, rational design can provide drugs that stabilize a native folded state of a protein, protein engineering can provide new binding proteins that sequester monomeric peptides from aggregation, small molecules and peptides can be designed to block aggregation or direct it into non-cytotoxic paths, and monoclonal antibodies have been developed for therapies towards neurodegenerative diseases based on inhibition of amyloid formation and clearance.

Naturally occurring autoantibodies against β-Amyloid

Naturally occurring antibodies (NAbs) have been described for more than 30 years. Recently, NAbs against β-Amyloid and against other proteins involved in neurodegenerative disorders have been detected in humans. Based on the current evidence, it is hypothesized that anti-Aβ NAbs can inhibit the fibrillation and toxicity of β-aymloid, can improve cognition in a transgenic mouse model and interfere with oligomers of Aβ. Different functions of these NAbs have been described in the current literature. Based on the results of the diverse studies a Phase-III study using IVIG has been initiated in patients with AD. The results will show whether the application of NAbs will change the fate of the disease. This chapter summarizes our current knowledge on NAbs against Aβ.

A monoclonal antibody against synthetic Aβ dimer assemblies neutralizes brain-derived synaptic plasticity-disrupting Aβ

Diverse lines of evidence indicate that pre-fibrillar, diffusible assemblies of the amyloid β-protein (Aβ) play an important role in Alzheimer's disease pathogenesis. Although the precise molecular identity of these soluble toxins remains unsettled, recent experiments suggest that sodium dodecyl sulfate (SDS)-stable Aβ dimers may be the basic building blocks of Alzheimer's disease-associated synaptotoxic assemblies and as such present an attractive target for therapeutic intervention. In the absence of sufficient amounts of highly pure cerebral Aβ dimers, we have used synthetic disulfide cross-linked dimers (free of Aβ monomer or fibrils) to generate conformation-specific monoclonal antibodies. These dimers aggregate to form kinetically trapped protofibrils, but do not readily form fibrils. We identified two antibodies, 3C6 and 4B5, which preferentially bind assemblies formed from covalent Aβ dimers, but do not bind to Aβ monomer, amyloid precursor protein, or aggregates formed by other amyloidogenic proteins. Monoclonal antibody 3C6, but not an IgM isotype-matched control antibody, ameliorated the plasticity-disrupting effects of Aβ extracted from the aqueous phase of Alzheimer's disease brain, thus suggesting that 3C6 targets pathogenically relevant Aβ assemblies. These data prove the usefulness of covalent dimers and their assemblies as immunogens and recommend further investigation of the therapeutic and diagnostic utility of monoclonal antibodies raised to such assemblies.

Application of immunosignatures to the assessment of Alzheimer's disease

OBJECTIVE

Accurate assessment of Alzheimer's disease (AD), both presymptomatically and at different disease stages, will become increasingly important with the expanding elderly population. There are a number of indications that the immune system is engaged in AD. Here we explore the ability of an antibody-profiling technology to characterize AD and screen for peptides that may be used for a simple diagnostic test.

METHODS

We developed an array-based system to profile the antibody repertoire of transgenic mice with cerebral amyloidosis (TG) and elderly individuals with or without AD. The array consists of 10,000 random sequence peptides (20-mers) capable of detecting antibody binding patterns, allowing the identification of peptides that mimic epitopes targeted by a donor's serum.

RESULTS

TG mice exhibited a distinct immunoprofile compared to nontransgenic littermates. Further, we show that dementia patients, including autopsy-confirmed AD subjects, have distinguishable profiles compared to age-matched nondemented people. Using antibodies to different forms of Aβ peptide and blocking protocols, we demonstrate that most of this signature is not due to the subject's antibodies raised against Aβ.

INTERPRETATION

We propose that "immunosignaturing" technology may have potential as a diagnostic tool in AD.

α-synuclein reactive antibodies as diagnostic biomarkers in blood sera of Parkinson's disease patients

Background

Auto-antibodies with specificity to self-antigens have been implicated in a wide variety of neurological diseases, including Parkinson's (PD) and Alzheimer's diseases, being sensitive indicators of neurodegeneration and focus for disease prevention. Of particular interest are the studies focused on the auto-immune responses to amyloidogenic proteins associated with diseases and their applications in therapeutic treatments such as vaccination with amyloid antigens and antibodies in PD, Alzheimer's disease and potentially other neurodegeneration ailments.

Methodology/Principal Findings

Generated auto-antibodies towards the major amyloidogenic protein involved in PD Lewy bodies – α-synuclein and its amyloid oligomers and fibrils were measured in the blood sera of early and late PD patients and controls by using ELISA, Western blot and Biacore surface plasmon resonance. We found significantly higher antibody levels towards monomeric α-synuclein in the blood sera of PD patients compared to controls, though the responses decreased with PD progression (P<0.0001). This indicates potential protective role of autoimmunity in maintaining the body homeostasis and clearing protein species whose disbalance may lead to amyloid assembly. There were no noticeable immune responses towards amyloid oligomers, but substantially increased levels of IgGs towards α-synuclein amyloid fibrils both in PD patients and controls, which subsided with the disease progression (P<0.0001). Pooled IgGs from PD patients and controls interacted also with the amyloid fibrils of Aβ (1–40) and hen lysozyme, however the latter were recognized with lower affinity. This suggests that IgGs bind to the generic amyloid conformational epitope, displaying higher specificity towards human amyloid species associated with neurodegeneration.

Conclusions/Significance

Our findings may suggest the protective role of autoimmunity in PD and therefore immune reactions towards PD major amyloid protein – α-synuclein can be of value in the development of treatment and diagnostic strategies, especially during the early disease stages.

Renal amyloidosis revisited: amyloid distribution, dynamics and biochemical type

BACKGROUND

Renal amyloidosis results from protein misfolding and leads to progressive renal insufficiency. Few data are available concerning the relevance of the histomorphological patterns and the dynamics of the disease process.

METHODS

Cases of renal amyloidosis in native kidney biopsies (n = 203) were retrospectively evaluated for the pattern of amyloid distribution, the extent of glomerular amyloid deposition and the amount of interstitial fibrosis and tubular atrophy. One hundred and fifty-eight cases were characterized by immunohistochemistry to determine the biochemical amyloid type. Morphological findings were correlated with available clinical data.

RESULTS

According to the predominant site of amyloid deposition, 84.6% showed a glomerular, 9.4% a vascular and 6% a tubulointerstitial distribution pattern. Within the glomeruli, amyloid was initially deposited in a focal segmental fashion that became diffuse and global in later stages. Most cases were identified as AL lambda (84/158) or AA (68/158). There was no correlation between the biochemical type and the distribution pattern. Serum creatinine correlated well with interstitial fibrosis and tubular atrophy and proteinuria with the glomerular amyloid load.

CONCLUSIONS

The relevance of the different distribution patterns is unclear at the moment, but they may be due to the physicochemical properties of the amyloid fibrils in a given patient. This may become important in future anti-fibrillar therapies.

Human intravenous immunoglobulin provides protection against Aβ toxicity by multiple mechanisms in a mouse model of Alzheimer's disease

Background

Purified intravenous immunoglobulin (IVIG) obtained from the plasma of healthy humans is indicated for the treatment of primary immunodeficiency disorders associated with defects in humoral immunity. IVIG contains naturally occurring auto-antibodies, including antibodies (Abs) against β-amyloid (Aβ) peptides accumulating in the brains of Alzheimer's disease (AD) patients. IVIG has been shown to alleviate AD pathology when studied with mildly affected AD patients. Although its mechanisms-of-action have been broadly studied, it remains unresolved how IVIG affects the removal of natively formed brain Aβ deposits by primary astrocytes and microglia, two major cell types involved in the neuroinflammatory responses.

Methods

We first determined the effect of IVIG on Aβ toxicity in primary neuronal cell culture. The mechanisms-of-action of IVIG in reduction of Aβ burden was analyzed with ex vivo assay. We studied whether IVIG solubilizes natively formed Aβ deposits from brain sections of APP/PS1 mice or promotes Aβ removal by primary glial cells. We determined the role of lysosomal degradation pathway and Aβ Abs in the IVIG-promoted reduction of Aβ. Finally, we studied the penetration of IVIG into the brain parenchyma and interaction with brain deposits of human Aβ in a mouse model of AD in vivo.

Results

IVIG was protective against Aβ toxicity in a primary mouse hippocampal neuron culture. IVIG modestly inhibited the fibrillization of synthetic Aβ1-42 but did not solubilize natively formed brain Aβ deposits ex vivo. IVIG enhanced microglia-mediated Aβ clearance ex vivo, with a mechanism linked to Aβ Abs and lysosomal degradation. The IVIG-enhanced Aβ clearance appears specific for microglia since IVIG did not affect Aβ clearance by astrocytes. The cellular mechanisms of Aβ clearance we observed have potential relevance in vivo since after peripheral administration IVIG penetrated to mouse brain tissue reaching highest concentrations in the hippocampus and bound selectively to Aβ deposits in co-localization with microglia.

Conclusions

Our results demonstrate that IVIG promotes recognition and removal of natively formed brain Aβ deposits by primary microglia involving natural Aβ Abs in IVIG. These findings may have therapeutic relevance in vivo as IVIG penetrates through the blood-brain barrier and specifically binds to Aβ deposits in brain parenchyma.

Anti-amyloidogenic activity of IgGs contained in normal plasma

INTRODUCTION

We have previously shown that a subpopulation of naturally occurring human IgGs has therapeutic potential for the amyloid-associated disorders. These molecules cross-react with conformational epitopes on amyloidogenic assemblies, including amyloid beta (Abeta) protein fibrils that are a pathological hallmark of Alzheimer's disease.

MATERIALS AND METHODS

Using our europium-linked immunosorbant assay, we established that approximately 95% of 260 screened donor plasma samples had amyloid fibril-reactive IgGs and Abeta conformer-reactive IgGs with minimal binding to Abeta monomers. Anti-amyloidogenic reactivity was diverse and attributed to Abeta targeting multiple fibril-related binding sites and/or variations in multidentate binding.

RESULTS AND DISCUSSION

There was no correlation between anti-fibril and anti-oligomer reactivity and donor age (19 to 60 years old) or gender. These findings demonstrate the inherent but diverse anti-amyloidogenic activity of natural IgGs contained in normal plasma.

CONCLUSION

Our studies provide support for investigating the clinical significance and physiological function of this novel class of antibodies.

Measurement of anti-beta amyloid antibodies in human blood

The human IgG repertoire contains endogenous antibodies against beta amyloid (Aβ) that may be relevant to the pathogenesis and treatment of Alzheimer's disease. There have been widely disparate estimates of the levels of these antibodies in human plasma. We identify factors that have contributed to these disparities and describe improved methods for measuring anti-Aβ antibodies in blood. These methods include isolating immunoglobulin by thiophilic chromatography and using chaotropic salts to dislodge weakly bound antibodies without significantly reducing the binding of specific anti-Aβ antibodies. Using these methods, we show that human blood contains polyvalent IgG antibodies that bind to Aβ with relatively low avidity and specificity, as well as IgG antibodies that bind to linear and conformational epitopes on amyloid monomers and aggregates with moderate to high avidity.