AlphaLISA detection of alpha-synuclein in the cerebrospinal fluid and its potential application in Parkinson's disease diagnosis

Development of an AlphaLISA assay for sensitive and accurate detection of influenza B virus

Objective

Influenza B virus (IBV) is highly contagious, spreads rapidly, and causes seasonal epidemic respiratory disease in the human population, especially in immunocompromised people and young children. Clinical manifestations in this high-risk population are often more severe than in immunocompetent hosts and sometimes atypical. Therefore, rapid, and accurate detection of IBV is important.

Methods

An amplified luminescent proximity homogeneous assay linked immunosorbent assay (AlphaLISA) was developed for detection of IBV by optimizing the ratio of IBV antibody-labeled receptor beads, streptavidin-conjugated donor beads and biotinylated IBV antibody, as well as the optimal temperature and time conditions for incubation. Assay sensitivity, specificity and reproducibility were evaluated. A total of 228 throat swab samples and inactivated influenza B virus were tested by AlphaLISA and lateral flow colloidal gold-based immunoassay (LFIA).

Results

AlphaLISA produced the best results for detection of inactivated influenza B virus when IBV antibody-labeled acceptor beads were 50 μg/ mL, streptavidin-conjugated donor beads were 40 μg/mL, and biotinylated IBV antibody was 0.5 μg/mL at 37°C for 15-10 min. Under these conditions, AlphaLISA had a limit of detection of 0.24 ng/mL for the detection of influenza B nucleoprotein, did not cross react with other common respiratory viruses, and showed good reproducibility with inter-assay coefficient of variation (CV) and intra-assay CV < 5%. The results of 228 clinical throat swab samples showed good agreement between AlphaLISA and LFIA (Kappa = 0.982), and AlphaLISA showed better sensitivity than LFIA for detecting inactivated influenza B virus.

Conclusion

AlphaLISA showed higher sensitivity and throughput in the detection of IBV and can be used for IBV diagnosis and epidemic control.

Conformational change of α-synuclein fibrils in cerebrospinal fluid from different clinical phases of Parkinson's disease

α-Synuclein (α-syn) has been shown to form various conformational fibrils associated with different synucleinopathies. But whether the conformation of α-syn fibrils changes during disease progression is unclear. Here, we amplified α-syn aggregates from the cerebrospinal fluid (CSF) of patients with Parkinson's disease (PD) staged in preclinical PD (pre-PD), middle- to late-stage PD (mid-PD), and late-stage PD (late-PD). Our results show that α-syn fibrils derived from the late-PD patient are most potent in inducing endogenous α-syn aggregation in primary neurons, followed by the mid-PD and pre-PD fibrils. By using cryo-electron microscopy, we further determined the high-resolution structures of the CSF-amplified fibrils. The structures exhibit remarkable differences in a minor but significant population of conformational species in different staged samples. Our work demonstrates structural and pathological differences between α-syn fibrils derived from PD patients at a spectrum of clinical stages, which suggests potential conformational transition of α-syn fibrils during the progression of PD.

α-Helical peptidic scaffolds to target α-synuclein toxic species with nanomolar affinity

α-Synuclein aggregation is a key driver of neurodegeneration in Parkinson's disease and related syndromes. Accordingly, obtaining a molecule that targets α-synuclein toxic assemblies with high affinity is a long-pursued objective. Here, we exploit the biophysical properties of toxic oligomers and amyloid fibrils to identify a family of α-helical peptides that bind to these α-synuclein species with low nanomolar affinity, without interfering with the monomeric functional protein. This activity is translated into a high anti-aggregation potency and the ability to abrogate oligomer-induced cell damage. Using a structure-guided search we identify a human peptide expressed in the brain and the gastrointestinal tract with analogous binding, anti-aggregation, and detoxifying properties. The chemical entities we describe here may represent a therapeutic avenue for the synucleinopathies and are promising tools to assist diagnosis by discriminating between native and toxic α-synuclein species.

Quantifying misfolded protein oligomers as drug targets and biomarkers in Alzheimer and Parkinson diseases

Protein misfolding and aggregation are characteristic of a wide range of neurodegenerative disorders, including Alzheimer and Parkinson diseases. A hallmark of these diseases is the aggregation of otherwise soluble and functional proteins into amyloid aggregates. Although for many decades such amyloid deposits have been thought to be responsible for disease progression, it is now increasingly recognized that the misfolded protein oligomers formed during aggregation are, instead, the main agents causing pathological processes. These oligomers are transient and heterogeneous, which makes it difficult to detect and quantify them, generating confusion about their exact role in disease. The lack of suitable methods to address these challenges has hampered efforts to investigate the molecular mechanisms of oligomer toxicity and to develop oligomer-based diagnostic and therapeutic tools to combat protein misfolding diseases. In this Review, we describe methods to quantify misfolded protein oligomers, with particular emphasis on diagnostic applications as disease biomarkers and on therapeutic applications as target biomarkers. The development of these methods is ongoing, and we discuss the challenges that remain to be addressed to establish measurement tools capable of overcoming existing limitations and to meet present needs.

Astrocytic expression of the Alzheimer's disease risk allele, ApoEε4, potentiates neuronal tau pathology in multiple preclinical models

ApoEε4 is a major genetic risk factor for Alzheimer's disease (AD), a disease hallmarked by extracellular amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs). The presence of the ApoEε4 allele is associated with increased Aβ deposition and a role for ApoEε4 in the potentiation of tau pathology has recently emerged. This study focused on comparing the effects of adeno-associated virus (AAV)-mediated overexpression of the three predominant human ApoE isoforms within astrocytes. The isoform-specific effects of human ApoE were evaluated within in vitro models of tau pathology within neuron/astrocyte co-cultures, as well as in a transgenic tau mouse model. Tau aggregation, accumulation, and phosphorylation were measured to determine if the three isoforms of human ApoE had differential effects on tau. Astrocytic overexpression of the human ApoEε4 allele increased phosphorylation and misfolding of overexpressed neuronal tau in multiple models, including the aggregation and accumulation of added tau oligomers, in an isoform-specific manner. The ability of ApoEε4 to increase tau aggregation could be inhibited by an ApoEε4-specific antibody. This study indicates that astrocytic expression of ApoEε4 can potentiate tau aggregation and phosphorylation within neurons and supports a gain of toxic function hypothesis for the effect of hApoEε4 on tau.

The establishment and clinical evaluation of a novel, rapid, no-wash one-step immunoassay for the detection of dengue virus non-structural protein 1

Dengue fever is a highly endemic arthropod-borne viral disease in the tropical and sub-tropical countries and is rapidly becoming a global threaten. Diagnosis has been conducted by either traditional serological methods or molecular biological techniques. However, these methods are either labor-intensive, time-consuming or with multiple steps, which are not suitable for high throughput detection of large quantity of samples. In the current study, a novel, rapid, no-wash one-step amplified luminescent proximity homogenous assay-linked immunosorbent assay (AlphaLISA) was developed and optimized for the diagnosis of dengue fever through the detection of dengue virus non-structural protein 1 (NS1). The linear range of the assay was determined to be 60,000 pg/mL to 200 pg/mL, with a lower detection limit of 127.45 pg/mL for NS1 protein. The precision of the assay was 8.24 % and 4.93 % for the high and low concentration. Clinical evaluation indicated that the sensitivity and specificity of the assay was 91.49 % and 81.54 %, respectively. This novel, rapid, no-wash one-step AlphaLISA assay is convenient and sensitive, which could be a good alternative for the screening of dengue fever in a high throughput format.