A new method to classify amyloid fibril proteins

Amyloids: from Pathogenesis to Function

The term "amyloids" refers to fibrillar protein aggregates with cross-β structure. They have been a subject of intense scrutiny since the middle of the previous century. First, this interest is due to association of amyloids with dozens of incurable human diseases called amyloidoses, which affect hundreds of millions of people. However, during the last decade the paradigm of amyloids as pathogens has changed due to an increase in understanding of their role as a specific variant of quaternary protein structure essential for the living cell. Thus, functional amyloids are found in all domains of the living world, and they fulfill a variety of roles ranging from biofilm formation in bacteria to long-term memory regulation in higher eukaryotes. Prions, which are proteins capable of existing under the same conditions in two or more conformations at least one of which having infective properties, also typically have amyloid features. There are weighty reasons to believe that the currently known amyloids are only a minority of their real number. This review provides a retrospective analysis of stages in the development of amyloid biology that during the last decade resulted, on one hand, in reinterpretation of the biological role of amyloids, and on the other hand, in the development of systems biology of amyloids, or amyloidomics.

Antigen retrieval in prion protein immunohistochemistry

Transmissible spongiform encephalopathies are a group of neurodegenerative diseases occurring in both humans and animals and are most likely caused by prions. Neuropathological confirmation of the clinical diagnosis has been a problem because of the difficulty in epitope retrieval from formalin-fixed, paraffin-embedded brain specimens. Many different protocols for the detection of prions in brain tissue have been used. Thus far, picric and/or formic acid, steam autoclaving at 121C of sections, microwave treatment, and 4 M guanidine thiocyanate treatment have been suggested. The objective of our experiment was to obtain the standard pretreatment(s) resulting in optimal immunostaining. In the experiment, successive tissue slides of brain specimens of several Creutzfeldt-Jakob disease and control patients were stained using different combinations of pretreatments. Using densitometric analysis, several well-defined locations per section were examined and prion immunostaining was quantified. The results showed that autoclaving is necessary for antigen retrieval and cannot be substituted by microwave treatment. The best results were obtained when the following combination was used in the specified order: 15 min saturated picric acid, 10 min steam autoclaving at 121C, 5 min 88% formic acid, and 2 hr 4 M guanidine thiocyanate at 4C. (J Histochem Cytochem 47:1465-1470, 1999)

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

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

Immunohistochemical study of ependymal neoplasms: histological subtypes and glial and epithelial characteristics

An immunohistochemical study on ependymal tumours was performed in order to determine what relationships exist between histological subtypes and epithelial or glial characteristics. Thirty-eight ependymal tumours were examined with antibodies to cytokeratin (CK), epithelial membrane antigen (EMA), transthyretin (TTR) and glial fibrillary acidic protein (GFAP) using the avidin-biotin-complex technique. They included 23 ependymomas, 13 anaplastic ependymomas, and 2 myxopapillary ependymomas. Only 3 of the 23 ependymomas were positive with EMA but 19 reacted with GFAP. None of them were positive with CK. Six of the 13 anaplastic ependymomas were positive with EMA, 3 with CK and 10 with GFAP. Five of the 6 anaplastic ependymomas which had epithelial marker proteins were either negative or weakly positive for GFAP. The present study demonstrates that most benign ependymomas exhibit GFAP positivity while the anaplastic ones tend to suppress their glial nature in favour of epithelial differentiation. However, ependymal tumours showed few characteristics of choroid plexus cells; only one of the examined cases was positive for TTR.

Amyloid neuropathy: immunocytochemical localization of intra- and extracellular immunoglobulin light chains

Sural nerve specimens from ten patients with amyloidosis (hereditary, associated with lymphoproliferative disorders, or of unknown origin) and peripheral neuropathy were investigated by immunohistochemistry at the light and electron microscopic level. Peroxidase-antiperoxidase and immunogold techniques were applied to glutaraldehyde-fixed, osmicated and epoxy-embedded tissue. In five cases, four of which associated with lymphoproliferative disorders, amyloid deposits strongly and exclusively reacted with antibodies to kappa or lambda light chains, respectively. By electron microscopy, bundles of immunogold-labelled amyloid fibrils could be identified in coated and uncoated single membrane-bound vesicles of endoneurial macrophages. Schwann cells did not contain intracellular amyloid but their processes were entangled in amyloid fibrils and their basement membranes were sometimes fused with the fibrillar masses. It is concluded that immunoglobulin light chains in AL (amyloid of immunoglobulin light chain origin) amyloidosis precipitate, forming amyloid fibrils, in the presence of, and presumably with the assistance of, endoneurial cells. Inefficiency of phagocytosis appears to be one of the major causes for the deleterious effects of amyloid.

Immunohistochemical verification of senile and kuru plaques in Creutzfeldt-Jakob disease and the allied disease

We investigated paraffin-embedded brain sections from 41 patients with Creutzfeldt-Jakob disease (CJD) and from 9 with Gerstmann-Sträussler syndrome (GSS) using anti-human prion protein (PrP) antisera (anti-GSS kuru plaque cores and anti-PrP synthetic peptide) and anti-beta protein antiserum. The anti-human PrP antiserum reacted with the plaques in CJD and GSS, with or without degenerative neurites (neuritic components). In addition, the anti-beta protein antiserum immunolabeled kuru plaque-like compact plaques in some cases of CJD. Therefore, previous morphological classifications of the plaques may not always be valid. Senile plaques labeled with anti-beta protein antiserum were evident in 65% of the CJD brains and 50% of GSS brains from patients in their 60s, and in 73% of brains from CJD patients in their 70s, but not in brains from patients under 60 years of age. The incidence of the senile plaques was compatible with the normal aging process and was apparently not accelerated by the disease process of CJD or GSS. These immunostaining approaches using anti-human PrP and anti-beta protein antisera allow classification of plaque types and increase the reliability of the pathological diagnosis in persons with dementia.

Methods for staining amyloid in tissues: a review

The traditional way of identifying amyloid in tissue sections has been staining with Congo red and demonstration of green birefringence under crossed polarizers. The original method of Congo red staining, described by Bennhold in 1922, has undergone several modifications to improve its sensitivity, specificity, and reliability. The most common modification is the alkaline Congo red method described by Puchtler and co-workers in 1962. Specificity is improved by using freshly prepared stain and a staining solution fully saturated with sodium chloride. Amyloid proteins can be further distinguished by autoclaving or by treating the tissue with potassium permanganate or alkaline guanidine. Autoclaving the tissues at 120 C for 30 min causes protein AA to lose its affinity for Congo red. Prolongation of autoclaving to 120 min abolishes the Congophilia of protein AL, but prealbumin-related amyloid shows little or no change. Treatment of the tissue with potassium permanganate causes protein AA and B2-microglobulin amyloid to lose their affinity to Congo red. Protein AA fails to stain with Congo red after treatment with alkaline guanidine for 1 min and protein AL and systemic senile amyloid protein (SSA) after 2 hr. Familial amyloid protein (FAP), prealbumin type, can stand 2 hr of alkaline guanidine treatment without losing its ability to stain with Congo red. Other methods of detection of amyloid include fluorescent stains, e.g., thioflavin T or S, and metachromatic stains such as crystal violet. Immunofluorescence and immunoperoxidase methods are used to identify and classify amyloid proteins in tissues. Antibodies against the P component, proteins AA and AL and FAP have been used with great precision. Due to cross-reactivity, these methods do not differentiate between some types of familial and senile systemic amyloidosis.

Familial amyloidotic polyneuropathy without familial occurrence: carrier detection by the radioimmunoassay of variant transthyretin

A 47 year old woman with familial amyloidotic polyneuropathy (FAP) is reported, without familial occurrence of the disease. Her 81 year old mother and 53 year old sister were proved to be asymptomatic carriers for variant transthyretin (TTR) by means of the radioimmunoassay. It is suggested that unknown factor(s) may play a role in preventing or delaying the onset of the disease, producing variations in sex and family incidence. In order to establish the diagnosis of non-hereditary primary amyloidotic polyneuropathy, it must be confirmed that variant TTR is absent in the serum of relatives.

A case of familial, atypical Alzheimer's disease: immunohistochemical study of amyloid P-component

The presence of amyloid P-component (AP) in the amyloid plaques of a case of familial, atypical Alzheimer's disease was examined by means of the anti-AP immunoperoxidase method. Many amyloid plaques stained strongly positive for AP, so that they were analogous in AP stainability to those of Creutzfeldt-Jakob disease.

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

Highly specific, high-resolution scintigraphic images of amyloid-laden organs in mice with experimentally induced amyloid A protein (AA) amyloidosis were obtained after intravenous injection of 123I-labeled serum amyloid P component (SAP). Interestingly, a much higher proportion (up to 40%) of the injected dose of heterologous human SAP localized to amyloid and was retained there than was the case with isologous mouse SAP, indicating that human SAP binds more avidly to mouse AA fibrils than does mouse SAP. Specificity of SAP localization was established by the failure of the related proteins, human C-reactive protein and Limulus C-reactive protein, to deposit significantly in amyloid and by the absence of human SAP deposition in nonamyloidotic organs. However, only partial correlations were observed between the quantity of SAP localized and two independent estimates, histology and RIA for AA of the amount of amyloid in particular organs. It is not clear which of the three methods used reflects better the extent or clinical significance of the amyloid deposits but in vivo localization of radiolabeled SAP, detectable and quantifiable by gamma camera imaging, is apparently extremely sensitive. These findings establish the use of labeled SAP as a noninvasive in vivo diagnostic probe in experimental amyloidosis, potentially capable of revealing the natural history of the condition, and suggest that it may also be applicable generally as a specific targeting agent for diagnostic and even therapeutic purposes in clinical amyloidosis.

Immunohistochemical study of cerebral amyloid angiopathy: use of an antiserum to a synthetic 28-amino-acid peptide fragment of the Alzheimer's disease amyloid precursor

A polyclonal antibody to a synthetic peptide representing a 28-amino-acid sequence of the previously isolated and described Alzheimer's disease amyloid precursor was raised in rabbits. The antibody was used in conjunction with an avidin-biotin-peroxidase technique to stain cerebral microvessels involved by amyloid angiopathy and senile "neuritic" plaque amyloid cores. The staining method has significant advantages over standard histologic techniques used to demonstrate brain amyloid and might have important practical applications in the study of microvascular lesions associated with cerebral amyloid angiopathy, as well as in studies on the pathogenesis of Alzheimer's disease or senile dementia of Alzheimer type.

Focal intracerebral accumulation of a novel type of amyloid protein. An early stage of cerebral amyloidoma?

The brain of a 60-year-old patient with bronchial carcinoma presented a focal amyloid deposit in the white matter associated with myelin and axonal destruction. An additional lesion was found in the basal ganglia. This silent focal intracerebral accumulation of amyloid substance may be a prestadium of a "cerebral amyloidoma". The histochemical and immunohistochemical analysis of the accumulated amyloid indicated that it may belong to a novel type of amyloid.

Incidence and characterization of age related amyloid deposits in the human anterior pituitary gland

To identify amyloid deposits in the anterior pituitary gland, we have immunohistochemical, histochemical and alkaline Congo red staining. The anti-human P component reacted positively with these amyloid deposits, while antisera against prealbumin, AA type amyloid fibril protein and various anterior pituitary hormones were negative. A combination of Congo red and anti-human P component staining was most sensitive and reliable for detection of amyloid in the anterior pituitary glands of 300 randomly autopsied patients. Amyloid deposits increased in parallel with the age of the patients, however, they appeared earlier and more frequently than heretofore reported. Deposition of amyloid was seen initially in the 3rd decade and the positivity rate of amyloid deposits was 73% in the 5th decade. The histochemical characteristics of these pituitary amyloid deposits differed from those of cerebral and systemic deposits, particularly those found in the amyloid of senile systemic amyloidosis.

Imaging of experimental amyloidosis with 131I-labeled serum amyloid P component

131I-labeled human serum amyloid P component, which was injected into mice with experimentally induced systemic AA amyloidosis and into controls, became specifically localized and was retained in amyloidotic organs. In comparison, it was rapidly and completely eliminated from unaffected tissues and from control animals. Distinctive images of this amyloid-specific deposition of labeled serum amyloid P component were derived from whole body scanning, in vivo, of amyloidotic mice. These findings suggest that such imaging may have applications for the diagnosis and quantitation of amyloid deposits in humans.

Choroidal epithelial cyst of the cerebral hemisphere. An immunohistochemical study

A case of choroidal epithelial cyst in the left cerebral hemisphere of a 4-month-old infant is described. The cyst wall was composed of a single epithelial layer with a basement membrane and fibrous connective tissue. An immunohistochemical study revealed the presence of prealbumin in the cytoplasm of these cuboidal epithelial cells. This fact strongly suggested that the cuboidal epithelium lining the cyst wall originated from choroidal epithelial cells. The diagnostic usefulness of the immunohistochemical study in choroidal epithelial cysts is discussed.

Chemical heterogeneity of amyloid in the carpal tunnel syndrome

140 biopsies from 108 patients afflicted with the carpal tunnel syndrome were studied, 27 of whom showed deposition of amyloid, in 6 of them to such an extent that the amyloid was considered significant in the pathogenesis of the carpal tunnel syndrome. Morphologically, vessels and ligaments were affected and especially the peritendinous structures. As it was always part of generalized amyloidosis, the amyloid in the carpal tunnel consisted immunohistologically of amyloid A in three cases (including one case with simultaneous amyloid deposition of the AA- and the AB-type), of amyloid A kappa in one case, of amyloid of prealbumin origin in seventeen cases and of AB-amyloid in eight cases. We also described for the first time the manifestation of generalized senile amyloidosis (ASs) in the carpal tunnel. Deposition of amyloid of beta-2-microglobulin type (AB) in the carpal tunnel was particularly frequent and massive.

Congophilia in cerebral amyloidosis is modified by inactivation procedures on slow transmissible pathogens

Cerebral tissues with amyloid deposits were treated by various chemicals which inactivated the agent of subacute spongiform encephalopathy (SSE). We discovered Congophilia in the amyloid plaques in cases of Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler syndrome (GSS) correlated to the chemical inactivation profiles of SSE. After incubation with trichloroacetate, guanidine-SCN, guanidine-HCl, formic acid, phenol and autoclaving, amyloid plaques in unfixed frozen sections of human brains with CJD or GSS, lost the affinity of Congo red and green birefringence under polarized light. In formalin-fixed, paraffin-embedded tissue sections, amyloid plaques of CJD and GSS lost the affinity of Congo red after most of these treatments. On the other hand, senile plaques in the aged, patients with Alzheimer's disease and with senile dementia of the Alzheimer type did not lose the affinity of Congo red after most of these treatments. Therefore, the amyloid deposits in the amyloid plaques differ from those in senile plaques. The methods we used facilitate differentiation of amyloid and senile plaques in formalin-fixed, paraffin-embedded tissues.

Scrapie-associated fibrils (SAF) purification method yields amyloid proteins from systemic and cerebral amyloidosis

We identified fibrils from non-transmissible systemic and cerebral amyloidosis using the purification method of scrapie-associated fibrils (SAF). The fibrils possessed the same nature of congophilia, filamentous structures and molecular weights as amyloid fibrils, and were resistant to Proteinase K digestion. This SAF method makes for a rapid extraction from amyloid-laden tissues. The method, therefore, may purify nontransmissible amyloids alone or together with SAF proteins.