Adenylate kinase 5 autoimmunity in treatment refractory limbic encephalitis

AK7-deficiency reversal inhibits ccRCC progression and boosts anti-PD1 immunotherapy sensitivity

Clear cell renal cell carcinoma (ccRCC) is a common kidney cancer with subtle early symptoms, high recurrence rates, and low sensitivity to traditional treatments like radiotherapy and chemotherapy. Identifying novel therapeutic targets is critical. The expression level of adenylate kinases 7 (AK7) in ccRCC was examined by the TCGAportal and UALCAN databases. The effect of AK7 on proliferation, invasion and migration of ccRCC cell lines was evaluated by cell assay. The correlation between AK7 expression and prognosis, as well as its direct relationship with immunotherapy efficacy, was analyzed using CANCERTOOL and Kaplan-Meier plotter data. Moreover, the TISIDB database was used to study the relationship between AK7 and immune markers. The effect of overexpressed AK7 combined with PD1 monoclonal antibody on ccRCC was evaluated in animal experiments. The results showed that low level of AK7 expression was observed in ccRCC tissues. The expression of AK7 can regulate the proliferation, invasion, and migration of human ccRCC cell lines. The level of AK7 expression was associated with OS of ccRCC patients. This was potentially due to the negative connection between AK7 expression and CD8+ T cell depletion, indicating that immunotherapy might be less effective in individuals with low AK7 expression. Conversely, augmenting AK7 demonstrated an enhanced effectiveness of anti-PD1 therapy. The findings of our research strongly indicated that AK7 could serve as both a prognostic indicator and therapeutic target for patients with ccRCC. Moreover, the overexpression of AK7 combined with anti-PD1 held promising potential as a therapeutic approach for treating ccRCC.

Paraneoplastic Calmodulin Kinase-Like Vesicle-Associated Protein (CAMKV) Autoimmune Encephalitis

OBJECTIVES

To report an autoimmune paraneoplastic encephalitis characterized by immunoglobulin G (IgG) antibody targeting synaptic protein calmodulin kinase-like vesicle-associated (CAMKV).

METHODS

Serum and cerebrospinal fluid (CSF) samples harboring unclassified antibodies on murine brain-based indirect immunofluorescence assay (IFA) were screened by human protein microarray. In 5 patients with identical cerebral IFA staining, CAMKV was identified as top-ranking candidate antigen. Western blots, confocal microscopy, immune-absorption, and mass spectrometry were performed to substantiate CAMKV specificity. Recombinant CAMKV-specific assays (cell-based [fixed and live] and Western blot) provided additional confirmation.

RESULTS

Of 5 CAMKV-IgG positive patients, 3 were women (median symptom-onset age was 59 years; range, 53-74). Encephalitis-onset was subacute (4) or acute (1) and manifested with: altered mental status (all), seizures (4), hyperkinetic movements (4), psychiatric features (3), memory loss (2), and insomnia (2). Paraclinical testing revealed CSF lymphocytic pleocytosis (all 4 tested), electrographic seizures (3 of 4 tested), and striking MRI abnormalities in all (mesial temporal lobe T2 hyperintensities [all patients], caudate head T2 hyperintensities [3], and cortical diffusion weighted hyperintensities [2]). None had post-gadolinium enhancement. Cancers were uterine adenocarcinoma (3 patients: poorly differentiated or neuroendocrine-differentiated in 2, both demonstrated CAMKV immunoreactivity), bladder urothelial carcinoma (1), and non-Hodgkin lymphoma (1). Two patients developed encephalitis following immune checkpoint inhibitor cancer therapy (atezolizumab [1], pembrolizumab [1]). All treated patients (4) demonstrated an initial response to immunotherapy (corticosteroids [4], IVIG [2]), though 3 died from cancer.

INTERPRETATION

CAMKV-IgG is a biomarker of immunotherapy-responsive paraneoplastic encephalitis with temporal and extratemporal features and uterine cancer as a prominent oncologic association. ANN NEUROL 2024;96:21-33.

Anti-adenylate kinase 5 encephalitis: Clinical characteristics, diagnosis, and management of this rare entity

The spectrum and understanding of antibody-positive autoimmune encephalitis (AE) have expanded over the past few decades. In 2007, a rare subtype of AE known as anti-adenylate kinase 5 (AK5) encephalitis, was first reported. This disease is more common in elderly males, with limbic encephalitis as the core phenotype (characterized by subacute anterograde amnesia, sometimes with psychiatric symptoms, and rarely with seizures). Brain magnetic resonance imaging typically demonstrated initial temporal lobe T2/fluid-attenuated inversion recovery hyperintensities, and subsequent atrophy. No concomitant tumors have been found yet. AK5 antibody, targeting the intracellular antigen, is a biomarker for a non-paraneoplastic T-cell autoimmunity response, and can be detected in serum and cerebrospinal fluid using tissue-based and cell-based assays. Cytotoxic T-cell-mediating neuronal injury and loss play a pivotal role in the immunopathogenesis of anti-AK5 encephalitis. Patients mostly show poor response to immunotherapy and thus a poor prognosis in the long run. Herein, we review the literature and provide updated knowledge of this less-known entity, focusing on clinical characteristics, paraclinical findings, diagnosis process, and therapeutic approaches.

Identification of Adenylate Kinase 5 as a Protein Target of Ginsenosides in Brain Tissues Using Mass Spectrometry-Based Drug Affinity Responsive Target Stability (DARTS) and Cellular Thermal Shift Assay (CETSA) Techniques

Ginseng is a very famous Chinese herbal medicine with various pharmacological effects. Ginsenosides, the main effective compounds of ginseng, show favorable biological activities in the central nervous system (CNS), but the protein targets of ginsenosides in brain tissues have not been clarified clearly. First, we screened proteins that interact with ginsenosides by mass spectrometry-based drug affinity responsive target stability (DARTS) and cellular thermal shift assay (CETSA). Then, we identified and confirmed adenylate kinase 5 (AK5) as a target protein of ginsenosides by biolayer interferometry (BLI), isothermal titration calorimetry (ITC), and molecular docking. Finally, an enzyme activity kit was used to determine the effect of 20(S)-protopanaxadiol (PPD), a ginseng saponin metabolite, on AK5 activities in vivo and in vitro. We screened out seven overlapping target proteins by proteomics of DARTS and CETSA. The BLI direct action assays showed that the direct interaction of PPD with AK5 was higher compared to the parental ginsenosides. Subsequently, BLI kinetic analysis and ITC assay showed that PPD specifically bound to AK5. Furthermore, key amino acid mutations predicted by molecular docking decreased the affinity between PPD and AK5. Enzyme activity assays showed that PPD increased AK5 activities in vivo and in vitro. The above-mentioned findings indicated that AK5 is a protein target of ginsenoside in the brain and PPD is considered to be a small-molecular activator of AK5, which can improve comprehension of the molecular mechanisms of ginseng pharmacological effects in the CNS and further develop AK5 activators based on the dammarane-type triterpenoid structure.

Limbic encephalitis

Limbic encephalitis (LE) is a clinical syndrome defined by subacutely evolving limbic signs and symptoms with structural and functional evidence of mediotemporal damage in the absence of a better explanation than an autoimmune (or paraneoplastic) cause. There are features common to all forms of LE. In recent years, antibody(ab)-defined subtypes have been established. They are distinct regarding underlying pathophysiologic processes, clinical and magnetic resonance imaging courses, cerebrospinal fluid signatures, treatment responsivity, and likelihood of a chronic course. With immunotherapy, LE with abs against surface antigens has a better outcome than LE with abs to intracellular antigens. Diagnostic and treatment challenges are, on the one hand, to avoid overlooking and undertreatment and, on the other hand, to avoid overdiagnoses and overtreatment. LE can be conceptualized as a model disease for the consequences of new onset mediotemporal damage by different mechanisms in adult life. It may be studied as an example of mediotemporal epileptogenesis.

Distinctive clinical presentation and pathogenic specificities of anti-AK5 encephalitis

Limbic encephalitis (LE) with antibodies against adenylate kinase 5 (AK5) has been difficult to characterize because of its rarity. In this study, we identified 10 new cases and reviewed 16 previously reported patients, investigating clinical features, IgG subclasses, human leukocyte antigen (HLA), and CSF proteomic profiles. Patients with anti-AK5 LE were mostly men (20/26, 76.9%) of median age 66 years old (range 48-94). Predominant symptom was severe episodic amnesia in all patients, frequently associated with depression (17/25, 68.0%). Weight loss, asthenia, and anorexia were also highly characteristic, being present in 11/25 (44.0%) patients. Although epilepsy was always lacking at disease onset, seizures developed later in a subset of patients (4/25, 16.0%). All patients presented CSF abnormalities, such as pleocytosis (18/25, 72.0%), oligoclonal bands (18/25, 72.0%), and increased Tau (11/14, 78.6%). Temporal lobe hyper-intensities were almost always present at disease onset (23/26, 88.5%), evolving nearly invariably toward a severe atrophy in subsequent MRIs (17/19, 89.5%). This finding was in line with a poor response to immunotherapy, with only 5/25 (20.0%) patients responding. IgG1 was the predominant subclass, being the most frequently detected and the one with highest titres in nine CSF-serum paired samples. Temporal biopsy from one of our new cases showed massive lymphocytic infiltrates dominated by both CD4+ and CT8+ T-cells, intense granzyme B expression, and abundant macrophages/microglia. HLA analysis in 11 patients showed a striking association with HLA-B*08:01 (7/11, 63.6%; OR = 13.4, 95% CI [3.8-47.4]), C*07:01 (8/11, 72.7%; OR = 11.0, 95% CI [2.9-42.5]), DRB1*03:01 (8/11, 72.7%; OR = 14.4, 95% CI [3.7-55.7]), DQB1*02:01 (8/11, 72.7%; OR = 13.5, 95% CI [3.5-52.0]), and DQA1*05:01 (8/11, 72.7%; OR = 14.4, 95% CI [3.7-55.7]) alleles, which formed the extended haplotype B8-C7-DR3-DQ2 in 6/11 (54.5%) patients (OR = 16.5, 95% CI [4.8-57.1]). Finally, we compared the CSF proteomic profile of five anti-AK5 patients with that of 40 controls and 10 cases with other more common non-paraneoplastic LE (five with antibodies against leucine-rich glioma inactivated 1 and five against contactin-associated protein-like 2), as well as 10 cases with paraneoplastic neurological syndromes (five with antibodies against Yo and five against Ma2). These comparisons revealed, respectively, 31 and seven significantly up-regulated proteins in anti-AK5 LE, mapping to apoptosis pathways and innate/adaptive immune responses. These findings suggest that the clinical manifestations of anti-AK5 LE result from a distinct T-cell mediated pathogenesis, with major cytotoxicity-induced apoptosis leading to a prompt and aggressive neuronal loss, likely explaining the poor prognosis and response to immunotherapy.

Autoimmune encephalitis with psychiatric features in adults: historical evolution and prospective challenge

Our review aims to delineate the psychiatric spectrum of autoantibody-associated autoimmune encephalitis over time through its discoveries of antibodies. We searched in PubMed for appropriate articles depicting the first appearance and spectrum of psychiatric symptomatology in autoantibody-positive encephalitis for this narrative review. Memory impairment was first associated with autoantibodies against intracellular antigens such as anti-HuD antibodies in 1993. 8 years later, autoantibodies against cell membrane surface antigens such as voltage-gated potassium channels were described in conjunction with memory dysfunction. The spectrum of psychiatric syndromes was amplified between 1990 and 2020 to include disorientation, behavior, cognitive dysfunction, obsessive compulsive behavior and suicidality in encephalitis patients occurring together mainly with antibodies against surface antigens, less so against intracellular antigens. In general, we found no specific psychiatric symptoms underlying specific autoantibody-associated encephalitis. As fundamental data on this issue have not been systemically assessed to date, we cannot know whether our specific findings would remain from systematic studies, i.e., on the association between cerebrospinal fluid N-methyl-D-aspartate receptor antibodies in catatonia. The psychiatric symptomatology overlaps between psychiatric domains and occurs frequently in antibody-positive encephalitis. No specific psychiatric symptoms imply an underlying, specifically autoantibody-associated encephalitis. The psychiatric phenotypology associated with antibody-positive encephalitis has evolved tremendously recently, and this new evidence reveals its relevance for future diagnostic and treatment aspects of autoimmune encephalitis patients.

Autoimmune psychosis: an international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin

There is increasing recognition in the neurological and psychiatric literature of patients with so-called isolated psychotic presentations (ie, with no, or minimal, neurological features) who have tested positive for neuronal autoantibodies (principally N-methyl-D-aspartate receptor antibodies) and who have responded to immunotherapies. Although these individuals are sometimes described as having atypical, mild, or attenuated forms of autoimmune encephalitis, some authors feel that that these cases are sufficiently different from typical autoimmune encephalitis to establish a new category of so-called autoimmune psychosis. We briefly review the background, discuss the existing evidence for a form of autoimmune psychosis, and propose a novel, conservative approach to the recognition of possible, probable, and definite autoimmune psychoses for use in psychiatric practice. We also outline the investigations required and the appropriate therapeutic approaches, both psychiatric and immunological, for probable and definite cases of autoimmune psychoses, and discuss the ethical issues posed by this challenging diagnostic category.

Adenylate Kinase: A Ubiquitous Enzyme Correlated with Medical Conditions

Adenylate kinase is a small, usually monomeric, enzyme found in every living thing due to its crucial role in energetic metabolism. This paper outlines the most relevant data about adenylate kinases isoforms, and the connection between dysregulation or mutation of human adenylate kinase and medical conditions. The following datadases were consulted: National Centre for Biotechnology Information, Protein Data Bank, and Mouse Genomic Informatics. The SmartBLAST tool, EMBOSS Needle Program, and Clustal Omega Program were used to analyze the best protein match, and to perform pairwise sequence alignment and multiple sequence alignment. Human adenylate kinase genes are located on different chromosomes, six of them being on the chromosomes 1 and 9. The adenylate kinases' intracellular localization and organ distribution explain their dysregulation in many diseases. The cytosolic isoenzyme 1 and the mitochondrial isoenzyme 2 are the main adenylate kinases that are integrated in the vast network of inflammatory modulators. The cytosolic isoenzyme 5 is correlated with limbic encephalitis and Leu673Pro mutation of the isoenzyme 7 leads to primary male infertility due to impairment of the ciliary function. The impairment of the mitochondrial isoenzymes 2 and 4 is demonstrated in neuroblastoma or glioma. The adenylate kinases are disease modifier that can assess the risk of diseases where oxidative stress plays a crucial role in pathogenesis like metabolic syndrome or neurodegenerative diseases. Because adenylate kinases has ATP as substrate, they are integrated in the global network of energetic process of any organism therefore are valid target for new pharmaceutical compounds.

Identification of adenylate kinase 5 antibodies during routine diagnostics in a tissue-based assay: Three new cases and a review of the literature

Antibodies against adenylate kinase 5 (AK5) have been described in patients with non-paraneoplastic limbic encephalitis, mainly in men around 70 years of age. Routine testing with specific cell-based assays is not yet available. Three patients with episodic anterograde memory problems and depression had extensive limbic lesions and developed severe atrophy, mainly of the medial temporal lobes. The antibodies were identified in serum and CSF based on the typical staining pattern of AK5 antibodies on a tissue-based assay (here, unfixed mouse brain). Subsequently, they were confirmed by a research laboratory through a cell-based assay.

Conventional brain MRI features distinguishing limbic encephalitis from mesial temporal glioma

PURPOSE

Radiological hallmark of autoimmune limbic encephalitis (LE) is a hyperintense signal in MRI T2-weighted images of mesial temporal structures. We aimed to identify conventional magnetic resonance imaging (MRI) features that can help distinguish LE from temporal glioma.

METHODS

Brain MRIs of 25 patients affected by antibody-positive autoimmune LE, 24 patients affected by temporal glioma (tumor group), and 5 negative controls were retrospectively blindly evaluated in random order.

RESULTS

Ten brain MRIs from the LE group were correctly recognized; one additional patient with mesial temporal hyperintensity with anti-AK5 abs LE was wrongly diagnosed as having a tumor. The brain MRIs of the remaining 14 of the 25 patients with LE were judged negative or, in three cases, showed features not typical for LE. In the tumor group, all MRIs showed pathological alterations diagnosed as tumors in 22/24 cases and as LE in two (2/22, 9%). Unilateral lesions were more common in tumors than in neuroradiologically abnormal LE (96% vs. 18%, p < 0.001). T2/FLAIR hyperintensity of the parahippocampal gyrus was associated more with tumor than with LE (71% vs. 18%) (p = 0,009), as T2/FLAIR hyperintensity of extralimbic structures (p = 0.015), edema (p = 0.041), and mass effect (p = 0.015). Maintenance of gray/white matter distinction was strongly associated with LE (91% vs. 17%, p < 0.001).

CONCLUSION

Conventional brain MRI is a fundamental tool in the differential diagnosis between LE and glioma. Bilateral involvement and maintenance of gray/white matter distinction at the cortical/subcortical interface are highly suggestive of LE.

Brain ureido degenerative protein modifications are associated with neuroinflammation and proteinopathy in Alzheimer's disease with cerebrovascular disease

BACKGROUND

Brain degenerative protein modifications (DPMs) are associated with the apparition and progression of dementia, and at the same time, Alzheimer's disease with cerebrovascular disease (AD + CVD) is the most prevalent form of dementia in the elder population. Thus, understanding the role(s) of brain DPMs in this dementia subtype may provide novel insight on the disease pathogenesis and may aid on the development of novel diagnostic and therapeutic tools. Two essential DPMs known to promote inflammation in several human diseases are the ureido DPMs (uDPMs) arginine citrullination and lysine carbamylation, although they have distinct enzymatic and non-enzymatic origins, respectively. Nevertheless, the implication of uDPMs in the neuropathology of dementia remains poorly understood.

METHODS

In this study, we use the state-of-the-art, ultracentrifugation-electrostatic repulsion hydrophilic interaction chromatography (UC-ERLIC)-coupled mass spectrometry technology to undertake a comparative characterization of uDPMs in the soluble and particulate postmortem brain fractions of subjects diagnosed with AD + CVD and age-matched controls.

RESULTS

An increase in the formation of uDPMs was observed in all the profiled AD + CVD brains. Citrulline-containing proteins were found more abundant in the soluble fraction of AD + CVD whereas homocitrulline-containing proteins were preferentially abundant in the particulate fraction of AD + CVD brains. Several dementia-specific citrulline residues were also identified in soluble proteins previously categorized as pro-immunogenic, which include the receptor P2X7, alpha-internexin, GFAP, CNP, MBP, and histones. Similarly, diverse dementia-specific homocitrulline residues were also observed in the particulate fractions of AD + CVD in proteins that have been vastly implicated in neuropathology. Intriguingly, we also found that the amino acids immediately flanking arginine residues may specifically influence the increase in protein citrullination.

CONCLUSIONS

Taken together, these results indicate that uDPMs widely contribute to the pathophysiology of AD + CVD by promoting neuroinflammation and proteinopathy. Furthermore, the obtained results could help to identify disease-associated proteins that can act as potential targets for therapeutic intervention or as novel biomarkers of specific neuropathology.

Characteristics in limbic encephalitis with anti–adenylate kinase 5 autoantibodies

Objective:

To report 10 patients with limbic encephalitis (LE) and adenylate kinase 5 autoantibodies (AK5-Abs).

Methods:

We conducted a retrospective study in a cohort of 50 patients with LE with uncharacterized autoantibodies and identified a specific target using immunohistochemistry, Western blotting, immunoprecipitation, mass spectrometry, and cell-based assay.

Results:

AK5 (a known autoantigen of LE) was identified as the target of antibodies in the CSFs and sera of 10 patients with LE (median age 64 years; range 57–80), which was characterized by subacute anterograde amnesia without seizure and sometimes preceded by a prodromal phase of asthenia or mood disturbances. Anterograde amnesia can be isolated, but some patients also complained of prosopagnosia, paroxysmal anxiety, or abnormal behavior. No associated cancer was observed. All 10 patients had bilateral hippocampal hypersignal on a brain MRI. CSF analysis generally showed a mild pleiocytosis with elevated immunoglobulin G index and oligoclonal bands, as well as high levels of tau protein with normal concentration of Aβ42 and phospho-tau, suggesting a process of neuronal death. Except for one patient, clinical response to immunotherapy was unfavorable, with persistence of severe anterograde amnesia. Two patients evolved to severe cognitive decline. Hippocampal atrophy was observed on control brain MRI. Using in vitro tests on hippocampal neurons, we did not identify clues suggesting a direct pathogenic role of AK5-Abs.

Conclusions:

AK5-Abs should be systematically considered in aged patients with subacute anterograde amnesia. Recognition of this disorder is important to develop new treatment strategies to prevent irreversible limbic damage.

Clinico-pathological correlation in adenylate kinase 5 autoimmune limbic encephalitis

Autoantibodies associated with autoimmune limbic encephalitis (ALE) have been well-characterized, with intracellular neuronal antibodies being less responsive to immunotherapy than antibodies to cell surface antigens. Adenylate kinase 5 (AK5) is a nucleoside monophosphate kinase vital for neuronal-specific metabolism and is located intracellularly in the cytosol and expressed exclusively in the brain. Antibodies to AK5 had been previously identified but were not known to be associated with human disease prior to the report of two patients with AK5-related ALE (Tuzun et al., 2007). We present the complete clinical picture for one of these patients and the first reported neuropathology for AK5 ALE.

The many isoforms of human adenylate kinases

Adenine nucleotides are involved in a variety of cellular metabolic processes, including nucleic acid synthesis and repair, formation of coenzymes, energy transfer, cell and ciliary motility, hormone secretion, gene expression regulation and ion-channel control. Adenylate kinases are abundant phosphotransferases that catalyze the interconversion of adenine nucleotides and thus regulate the adenine nucleotide ratios in different intracellular compartments. Nine different adenylate kinase isoenzymes have been identified and characterized so far in human tissues, named AK1 to AK9 according to their order of discovery. Adenylate kinases differ in molecular weight, tissue distribution, subcellular localization, substrate and phosphate donor specificity and kinetic properties. The preferred substrate and phosphate donor of all adenylate kinases are AMP and ATP respectively, but some members of the family can phosphorylate other substrates and use other phosphate donors. In addition to their nucleoside monophosphate kinase activity, adenylate kinases were found to possess nucleoside diphosphate kinase activity as they are able to phosphorylate both ribonucleoside and deoxyribonucleoside diphosphates to their corresponding triphosphates. Nucleoside analogues are structural analogues of natural nucleosides, used in the treatment of cancer and viral infections. They are inactive prodrugs that are dependent on intracellular phosphorylation to their pharmacologically active triphosphate form. Novel data presented in this review confirm the role of adenylate kinases in the activation of deoxyadenosine and deoxycytidine nucleoside analogues.

Pathogenic and physiological autoantibodies in the central nervous system

In this article, we review the current knowledge on pathological and physiological autoantibodies directed toward structures in the central nervous system (CNS) with an emphasis on their regulation and origin. Pathological autoantibodies in the CNS that are associated with autoimmunity often lead to severe neurological deficits via inflammatory processes such as encephalitis. In some instances, however, autoantibodies function as a marker for diagnostic purposes without contributing to the pathological process and/or disease progression. The existence of naturally occurring physiological autoantibodies has been known for a long time, and their role in maintaining homeostasis is well established. Within the brain, naturally occurring autoantibodies targeting aggregated proteins have been detected and might be promising candidates for new therapeutic approaches for neurodegenerative disorders. Further evidence has demonstrated the existence of naturally occurring antibodies targeting antigens on neurons and oligodendrocytes that promote axonal outgrowth and remyelination. The numerous actions of physiological autoantibodies as well as their regulation and origin are summarized in this review.

Anti-NMDA receptor encephalitis. The disorder, the diagnosis and the immunobiology

Anti-NMDAR encephalitis is a newly characterized syndrome with a progressive, predictable clinical course and the possibility of effective treatment. Accurate and timely diagnosis is critical to selection and implementation of treatments, and optimal patient outcomes. Outcomes are improved with early diagnosis via indirect immunofluorescence or cell-based assays, and the rapid and appropriate administration of immunosuppressant and anti-psychotic therapies. Three possible scenarios accounting for the immunopathogenesis of anti-NMDAR encephalitis are presented, with the most probable one being that of paraneoplastic autoimmunity. Future efforts in this disorder should focus on elucidating the mechanisms that contribute to initiation of this antibody response, as well as exploring the role of tumors, infectious triggers and immune-reactivation. Finally, accessible tools need to be developed that allow for reliable identification of specific antibody markers against synaptic proteins.

Immunological markers in neurological disorders

Neurological dysfunction results from vascular, inflammatory, degenerative, neoplastic, metabolic or genetic causes. Of particular interest is a group of neurological symptoms thought to be linked to an underlying tumour, the so-called paraneoplastic syndromes. It is considered to be due to an attempt by the immune system to subjugate the growth of the tumour by triggering an antibody response against the neuronal antigens expressed by the neoplasm. The unfortunate consequence of this is an assault by the immune components on the nervous tissue, thereby rapidly precipitating a variety of neurological deficits. Every level of the nervous system is potentially vulnerable, with the disability being considered as irreversible due to the lack of regenerative capacity of the neurons. This phenomenon is rare, occurring at an approximate frequency of less than 1% of all tumours and often accompanied by the presence of specific high-titre autoantibodies in both the cerebrospinal fluid and blood. This group of antibodies are non-pathogenic markers for paraneoplastic neurological syndromes, which have expanded to almost 20 since the discovery, in 1986, of the first clinically relevant syndrome. More recently, a new generation of antineuronal antibodies against cell surface antigens, having a direct pathogenic role in causing the disease, has emerged to complement the existing repertoire. Neuronal antibodies are useful diagnostic markers of the brain disease and also, in some cases, may reveal an underlying malignancy, thus facilitating faster diagnosis and earlier treatment with consequently better prognosis.

Current approaches to the treatment of paraneoplastic encephalitis

Paraneoplastic neurological syndromes (PNSs) cover a wide range of diseases and involve both the central nervous system (CNS) and peripheral nervous system. Paraneoplastic encephalitis comprises several diseases such as paraneoplastic cerebellar degeneration (PCD), limbic encephalitis (LE), paraneoplastic encephalomyelitis (PEM), brainstem encephalitis, opsomyoclonus syndrome, in addition to other even less frequently occurring entities. LE was the first historically identified CNS PNS, and similarities between other temporal lobe diseases such as herpes encephalitis have been elucidated. In the past few decades several autoantibodies have been described in association with LE. These encompass the classical 'onconeuronal' antibodies (abs) such as Hu, Yo, Ri and others, and now additionally abs towards either ion channels or surface antigens. The clinical core findings in LE are various mental changes such as amnesia or confusion, often associated with seizures. Careful characterization of psychiatric manifestations and/or associated neurological signs can help to characterize the syndrome and type of ab. The treatment options in LE depend on the aetiology. In LE caused by onconeuronal abs, the treatment options are poor. In two types of abs associated with LE, abs against ion channels and surface antigens (e.g. NMDA), immunomodulatory treatments seem effective, making these types of LE treatable conditions. However, LE can also occur without being associated with cancer, in which case only immunomodulation is required. Despite effective treatments, some patients' residual deficits remain, and recurrences have also been described.

Treatable neurological disorders misdiagnosed as Creutzfeldt-Jakob disease

OBJECTIVE

Heightened awareness of Creutzfeldt-Jakob disease (CJD) among physicians and the lay public has led to its frequent consideration in the differential diagnosis of patients with rapidly progressive dementia (RPD). Our goal was to determine which treatable disorders are most commonly mistaken for CJD.

METHODS

We performed a retrospective clinical and neuropathological review of prion-negative brain autopsy cases referred to the US National Prion Disease Pathology Surveillance Center at Case Western Reserve University from January 2006 through December 2009.

RESULTS

Of 1,106 brain autopsies, 352 (32%) were negative for prion disease, 304 of which had adequate tissue for histopathological analysis. Alzheimer disease (n = 154) and vascular dementia (n = 36) were the 2 most frequent diagnoses. Seventy-one patients had potentially treatable diseases. Clinical findings included dementia (42 cases), pyramidal (n = 20), cerebellar (n = 14), or extrapyramidal (n = 12) signs, myoclonus (n = 12), visual disturbance (n = 9), and akinetic mutism (n = 5); a typical electroencephalogram occurred only once. Neuropathological diagnoses included immune-mediated disorders (n = 26), neoplasia (n = 25, most often lymphoma), infections (n = 14), and metabolic disorders (n = 6).

INTERPRETATION

In patients with RPD, treatable disorders should be considered and excluded before diagnosing CJD. Misdiagnosed patients often did not fulfill World Health Organization criteria. RPD with positive 14-3-3 cerebrospinal fluid protein should not be regarded as sufficient for the diagnosis of CJD. Adherence to revised criteria for CJD, which include distinctive magnetic resonance imaging features of prion disease, is likely to improve diagnostic accuracy.

Antineuronal autoantibodies in neurological disorders

Autoantibodies (abs) related to neurological disease are currently classified into two large groups depending on the site of the respective target antigen: Group I encompasses abs that recognise intracellular antigens (Hu, Yo, Ri, CV2/CRMP5, amphiphysin, Ma2, SOX, ZIC, GAD, adenylate kinase 5, homer 3), whereas group II abs are targeted against neuronal cell membrane antigens (VGKC, AMPA-R, GABAB-R, NMDA-R, Glycine-R, VGCC, metabotropic GluR1). Both abs groups can be further subdivided according to their diagnostic impact for paraneoplastic or non-paraneoplastic neurological disease. The review gives an overview of the common characteristics of each group and provides more detailed information on single abs and the associated clinical syndromes.

The characterization of human adenylate kinases 7 and 8 demonstrates differences in kinetic parameters and structural organization among the family of adenylate kinase isoenzymes

Differences in expression profiles, substrate specificities, kinetic properties and subcellular localization among the AK (adenylate kinase) isoenzymes have been shown to be important for maintaining a proper adenine nucleotide composition for many different cell functions. In the present study, human AK7 was characterized and its substrate specificity, kinetic properties and subcellular localization determined. In addition, a novel member of the human AK family, with two functional domains, was identified and characterized and assigned the name AK8. AK8 is the second known human AK with two complete and active AK domains within its polypeptide chain, a feature that has previously been shown for AK5. The full-length AK8, as well as its two domains AK8p1 and AK8p2, all showed similar AK enzyme activity. AK7, full-length AK8, AK8p1 and AK8p2 phosphorylated AMP, CMP, dAMP and dCMP with ATP as the phosphate donor, and also AMP, CMP and dCMP with GTP as the phosphate donor. Both AK7 and full-length AK8 showed highest affinity for AMP with ATP as the phosphate donor, and proved to be more efficient in AMP phosphorylation as compared with the major cytosolic isoform AK1. Expression of the proteins fused with green fluorescent protein demonstrated a cytosolic localization for both AK7 and AK8.

Proteome analysis of human Wharton's jelly cells during in vitro expansion

Background

The human umbilical cord contains mucoid connective tissue and fibroblast-like cells. These cells named Wharton's jelly cells, (WJCs) display properties similar to mesenchymal stem cells therefore representing a rich source of primitive cells to be potentially used in regenerative medicine.

Results

To better understand their self-renewal and potential in vitro expansion capacity, a reference 2D map was constructed as a proteomic data set. 158 unique proteins were identified. More than 30% of these proteins belong to cytoskeleton compartment. We also found that several proteins including Shootin1, Adenylate kinase 5 isoenzyme and Plasminogen activator-inhibitor 2 are no longer expressed after the 2^nd passage of in vitro replication. This indicates that the proliferative potency of these cells is reduced after the initial stage of in vitro growing. At the end of cellular culturing, new synthesized proteins, including, ERO1-like protein alpha, Aspartyl-tRNA synthetase and Prolyl-4-hydroxylase were identified. It is suggested that these new synthesized proteins are involved in the impairment of cellular surviving during replication and differentiation time.

Conclusions

Our work represents an essential step towards gaining knowledge of the molecular properties of WJCs so as to better understand their possible use in the field of cell therapy and regenerative medicine.

Autoimmune limbic encephalitis

Autoimmune limbic encephalitis (LE) can arise both by paraneoplastic and non-paraneoplastic mechanisms. Patients with LE usually have a subacute onset of memory impairment, disorientation and agitation, but can also develop seizures, hallucinations and sleep disturbance. The following investigations may aid the diagnosis: analysis of cerebrospinal fluid (CSF), electroencephalography, magnetic resonance imaging, fluorodeoxyglucose positron emission tomography and neuronal antibodies in the serum and CSF. Neuronal antibodies are sometimes, but not always, pathogenic. Autoimmune LE may respond to corticosteroids, intravenous IgG (IVIG) or plasma exchange. The cornerstone of paraneoplastic LE therapy is resection of the tumour and/or oncological treatment. Several differential diagnoses must be excluded, among them herpes simplex encephalitis.

Adenylate kinase and AMP signaling networks: metabolic monitoring, signal communication and body energy sensing

Adenylate kinase and downstream AMP signaling is an integrated metabolic monitoring system which reads the cellular energy state in order to tune and report signals to metabolic sensors. A network of adenylate kinase isoforms (AK1-AK7) are distributed throughout intracellular compartments, interstitial space and body fluids to regulate energetic and metabolic signaling circuits, securing efficient cell energy economy, signal communication and stress response. The dynamics of adenylate kinase-catalyzed phosphotransfer regulates multiple intracellular and extracellular energy-dependent and nucleotide signaling processes, including excitation-contraction coupling, hormone secretion, cell and ciliary motility, nuclear transport, energetics of cell cycle, DNA synthesis and repair, and developmental programming. Metabolomic analyses indicate that cellular, interstitial and blood AMP levels are potential metabolic signals associated with vital functions including body energy sensing, sleep, hibernation and food intake. Either low or excess AMP signaling has been linked to human disease such as diabetes, obesity and hypertrophic cardiomyopathy. Recent studies indicate that derangements in adenylate kinase-mediated energetic signaling due to mutations in AK1, AK2 or AK7 isoforms are associated with hemolytic anemia, reticular dysgenesis and ciliary dyskinesia. Moreover, hormonal, food and antidiabetic drug actions are frequently coupled to alterations of cellular AMP levels and associated signaling. Thus, by monitoring energy state and generating and distributing AMP metabolic signals adenylate kinase represents a unique hub within the cellular homeostatic network.

Paraneoplastic syndromes of the CNS

Major advances in the management of paraneoplastic neurologic disorders (PND) include the detection of new antineuronal antibodies, the improved characterisation of known syndromes, the discovery of new syndromes, and the use of CT and PET to reveal the associated tumours at an early stage. In addition, the definition of useful clinical criteria has facilitated the early recognition and treatment of these disorders. In this article, we review some classic concepts about PND and recent clinical and immunological developments, focusing on paraneoplastic cerebellar degeneration, opsoclonus-myoclonus, and encephalitides affecting the limbic system.

Paraneoplastic neurological syndromes: diagnosis and treatment

PURPOSE OF REVIEW

The most relevant advances in the field of paraneoplastic neurological syndromes are described, with special emphasis on particular clinical-immunological associations and practical issues for the diagnosis and treatment of these disorders.

RECENT FINDINGS

Paraneoplastic neurological syndromes may present with classical neurological symptoms or less frequently with symptoms that do not initially raise suspicion of these disorders. Recent examples include patients who present with epilepsia partialis continua or frontal disequilibrium associated with Hu antibodies, hypersommnia and anti-Ma2 antibodies, Devic's syndrome and CV2/CRMP5 antibodies and a syndrome characterized by psychiatric features and central hypoventilation in young women with anti-N-methyl-D-aspartate receptor antibodies. The cause of the neuronal damage is still open to debate. The recent description of antibodies against membrane proteins in opsoclonus or encephalitis associated with teratoma strongly suggests that antibodies may be responsible for the clinical features in some cases. Early diagnosis and effective treatment of the tumor remain the best options to improve or stabilize the syndrome. Immunotherapy, including rituximab, seems effective in those cases associated with functional damage.

SUMMARY

Neurologists must be aware of neurological syndromes that may have a paraneoplastic origin. Detection of onconeural antibodies is crucial to make the correct diagnosis. Immunotherapy should be used, although the impact of the treatment is unclear in cases with irreversible neuronal damage.