Synthesis of oligo-α-(1→2)-4,6-dideoxy-4-formamido-d-mannopyranosides related to the A epitope of the Brucella O-polysaccharide and their use for assaying of serum immunoglobulins

Pathogenic bacteria of the genus Brucella cause a severe threat for public health and agricultural economics. The World Health Organization considers brucellosis to be one of the most serious and also neglected zoonotic diseases. The use of traditional whole-cell brucellosis vaccines complicates the differentiation between infected and vaccinated animals (DIVA). Moreover, diagnostics based on lipopolysaccharide of Brucella are susceptible to false positive results. Structural features of Brucella O-antigens make synthetic oligosaccharides promising agents for the development of diagnostic tools and vaccines against brucellosis. Here we report the synthesis of spacer-armed di-, tri-, tetra- and penta-4,6-dideoxy-4-formamido-α-(1→2)-d-mannopyranosides which are related to the A-epitope of Brucella O-antigen. The key α-(1→2)-linked disaccharide thioglycoside donor was synthesized by employing the strategy of orthogonal glycosylation of thioglycoside acceptor with trichloroacetimidate donor. Sequential block-wise assembly yielded a series of desired compounds, which were subsequently deprotected and converted into target molecules and then into their fluorescein-labeled conjugates. The obtained conjugates were employed as tracers in a fluorescence polarization assay (FPA) to detect anti-Brucella immunoglobulins. Among the studied compounds, the trisaccharide conjugate showed the greatest difference in median FP signals between Brucella-positive and Brucella-negative sera samples making it a promising candidate for developing FP diagnostic assays. The decreased FP signal in the cases of tetra- and pentasaccharide tracers can be associated with the known “propeller-effect” due to the rotational mobility of the part bearing the fluorescent label and of the fluorescein itself and/or the enlarging of the distance between the fluorescein part and the antibody-oligosaccharide complex. This observation demonstrates the advantages of using synthetic relatively small synthetic tracers with well-defined structure in comparison with heterogeneous fluorescein-labelled O-polysaccharides which are in use today in spite of the fact that they contain poorly characterized amounts of label attached along the polysaccharide chains

Fluorescence-Polarization-Based Assaying of Lysozyme with Chitooligosaccharide Tracers

Lysozyme is a well-known enzyme found in many biological fluids which plays an important role in the antibacterial protection of humans and animals. Lysozyme assays are used for the diagnosis of a number of diseases and utilized in immunohistochemistry, genetic and cellular engineering studies. The assaying methods are divided into two categories measuring either the concentration of lysozyme as a protein or its activity as an enzyme. While the first category of methods traditionally uses an enzyme-linked immunosorbent assay (ELISA), the methods for the determination of the enzymatic activity of lysozyme use either live bacteria, which is rather inconvenient, or natural peptidoglycans of high heterogeneity and variability, which leads to the low reproducibility of the assay results. In this work, we propose the use of a chemically synthesized substrate of a strictly defined structure to measure in a single experiment both the concentration of lysozyme as a protein and its enzymatic activity by means of the fluorescence polarization (FP) method. Chito-oligosaccharides of different chain lengths were fluorescently labeled and tested leading to the selection of the pentasaccharide as the optimal size tracer and the further optimization of the assay conditions for the accurate (detection limit 0.3 μM) and rapid (<30 min) determination of human lysozyme. The proposed protocol was applied to assay human lysozyme in tear samples and resulted in good correlation with the reference assay. The use of synthetic fluorescently labeled tracer, in contrast to natural peptidoglycan, in FP analysis allows for the development of a reproducible method for the determination of lysozyme activity

Rapid detection of phycotoxin domoic acid in seawater and seafood based on the developed lateral flow immunoassay

A lateral flow immunoassay (LFIA) of phycotoxin domoic acid (DA) contaminating seawater and marine organisms was developed in this investigation.</jats:p

Application of the Chitooligosaccharides and Fluorescence Polarization Technique for the Assay of Active Lysozyme in Hen Egg White

This study describes the applicability of the fluorescence polarization assay (FPA) based on the use of FITC-labeled oligosaccharide tracers of defined structure for the measurement of active lysozyme in hen egg white. Depending on the oligosaccharide chain length of the tracer, this method detects both the formation of the enzyme-to-tracer complex (because of lectin-like, i.e., carbohydrate-binding action of lysozyme) and tracer splitting (because of chitinase activity of lysozyme). Evaluation of the fluorescence polarization dynamics enables simultaneous measurement of the chitinase and lectin activities of lysozyme, which is crucial for its detection in complex biological systems. Hen egg white lysozyme (HEWL), unlike human lysozyme (HL), formed a stable complex with the chitotriose tracer that underwent no further transformations. This fact allows for easy measurement of the carbohydrate-binding activity of the HEWL. The results of the lysozyme activity measurement for hen egg samples obtained through the FPA correlated with the results obtained using the traditional turbidimetry method. The FPA does not have the drawbacks of turbidimetry, which are associated with the need to use bacterial cells that cannot be precisely standardized. Additionally, FPA offers advantages such as rapid analysis, the use of compact equipment, and standardized reagents. Therefore, the new express technique for measuring the lysozyme activity is applicable for evaluating the complex biomaterial, including for the purposes of food product quality control

Applying a Fluorescence Polarization Assay for Detection of Brucellosis in Animals Using the Fluorescently Labeled Synthetic Oligosaccharides as Biosensing Tracer

Brucellosis in animals is an infectious disease caused by bacteria of the genus Brucella. Known methods for diagnosing brucellosis face some challenges, due to the difficulties in isolating and standardizing the natural brucellosis antigen. In this work, we investigated the possibility of using the fluorescence polarization assay (FPA) with synthetic glycoconjugate biosensing tracers to detect antibodies against Brucella as a new methodology for diagnosing brucellosis. Based on the received results, the synthetic fluorescein-labeled trisaccharide tracer is most effective for Brucellosis detection. This tracer is structurally related to the immune determinant fragment of the Brucella LPS buildup of N-formyl-d-perosamine units, connected via &alpha;-(1&rarr;3)-linkage at the non-reducing end and &alpha;-(1&rarr;2)-linkage at the reducing end. The sensitivity and specificity in the case of the use of trisaccharide tracer 3b were 71% and 100% (Yuden&rsquo;s method) and 87% and 88% (Euclidean method), respectively, which is comparable with the diagnostic efficiency of traditionally used serological methods, such as the agglutination test (AT), complement fixation test (CFT), and Rose Bengal test (RBT). Given the known advantages of FPA (e.g., speed, compactness of the equipment, and standard reagents) and the increased specificity of the developed test system, it would be appropriate to consider its widespread use for the diagnosis of brucellosis in animals, including rapid testing in the field

Second asymptomatic carotid surgery trial (ACST-2) : a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86-1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91-1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable