Analysis of O-Acetylated Sialic Acids in Dried Blood Spots

Analysis of O-acetylated sialic acids by 3-nitrophenylhydrazine derivatization combined with LC-MS/MS

Sialic acids are a family of monosaccharides that share a nine-carbon backbone and a carboxyl group. A recent derivatization method based on 3-nitrophenylhydrazine (3-NPH) provides a mild chemical labeling technique for biomolecules containing carbonyl or carboxyl groups. In this study, we utilized 3-NPH to label sialic acids via a two-step derivatization process. The derivatized species can produce a common reporter ion corresponding to C1-C3 with two labels, and a fragment differentiating between Neu5Ac, Neu5Gc, and KDN. This method is compatible with O-acetylated sialic acids and provides high sensitivity to Neu5Gc and KDN, and since the utilization of dual labeling significantly enhances the hydrophobicity of derivatives, it can effectively mitigate matrix effects when combined with parallel reaction monitoring technology. Negative-ion tandem mass spectrometry (MS/MS) analysis reveals a distinctive fragmentation profile for the 4-O-acetylated species, while the other sialic acids yield similar MS/MS spectra with a high abundance of reporter ions. Using the reporter ion as a transition, this analytical strategy is effective for analyzing complex biological samples. For example, it was successfully employed to quantify sialic acids in the intestinal tissues of several carp species, demonstrating its potential in sialylation research.

9-O Acetylated Gangliosides in Health and Disease

Glycosphingolipids comprise a lipid class characterized by the presence of sugar moieties attached to a ceramide backbone. The role of glycosphingolipids in pathophysiology has gained relevance in recent years in parallel with the development of analytical technologies. Within this vast family of molecules, gangliosides modified by acetylation represent a minority. Described for the first time in the 1980s, their relation to pathologies has resulted in increased interest in their function in normal and diseased cells. This review presents the state of the art on 9-O acetylated gangliosides and their link to cellular disorders.

Precision Characterization of Site-Specific O-Acetylated Sialic Acids on N-Glycoproteins

O-Acetylation is a common modification of sialic acid, playing a significant role in glycoprotein stability, immune response, and cell development. Due to the lack of efficient methods for direct analysis of O-acetylated sialoglycopeptides (O-AcSGPs), the majority of identified O-acetylated sialic acids (O-AcSia) until now had no glycosite/glycoprotein information. Herein, we introduced a new workflow for precise interpretation of O-AcSGPs with probability estimation by recognizing the characteristic B and Y ions of O-AcSias. With further optimization of mass spectrometry parameters, the method allowed us to identify a total of 171 unique O-AcSGPs in mouse serum. Although the majority of these O-AcSGPs were at a relatively low abundance compared with their non-O-acetylated states, they were mainly involved in peptidase/endopeptidase inhibitor activities. The method paves the way for large-scale structural and functional analyses of site-specific O-AcSias in various complex samples as well as further identification of many other similar chemical modifications on glycoproteins.

Quantitative Standards of 4-O acetyl and 9-O acetyl N-acetyl Neuraminic Acid for the Analysis of Plasma and Serum

N‐Acetylneuraminic acid (sialic acid, Neu5Ac) is one of a large, diverse family of nine‐carbon monosaccharides that play roles in many biological functions such as immune response. Neu5Ac has previously been identified as a potential biomarker for the presence and pathogenesis of cardiovascular disease (CVD), diabetes and cancer. More recent research has highlighted acetylated sialic acid derivatives, specifically Neu5,9Ac₂, as biomarkers for oral and breast cancers, but advances in analysis have been hampered due to a lack of commercially available quantitative standards. We report here the synthesis of 9‐O‐ and 4‐O‐acetylated sialic acids (Neu5,9Ac₂ and Neu4,5Ac₂) with optimisation of previously reported synthetic routes. Neu5,9Ac₂ was synthesised in 1 step in 68 % yield. Neu4,5Ac₂ was synthesised in 4 steps in 39 % overall yield. Synthesis was followed by analysis of these standards via quantitative NMR (qNMR) spectroscopy. Their utilisation for the identification and quantification of specific acetylated sialic acid derivatives in biological samples is also demonstrated.

The role of sialic acids in the initiation of atherosclerosis

Atherosclerosis is a major cause of disease-related mortality around the globe. The main characteristic of the disease is an accumulation of plaque on the arterial wall and subsequent erosion or rupture of some plaques. Atherosclerosis often leads to cardiovascular disease and such acute complications as myocardial infarction or ischemic stroke due to thrombus formation. Most recent advances in atherosclerotic research state that the modifications of low-density lipoprotein (LDL) are one of the most significant stages in the disease initiation, and among these modifications desialylation is of particular interest. Sialic acids are widely expressed on all types of cells of many organisms and participate in numerous biological processes. Regarding atherosclerosis, sialidases that are responsible for the regulation of the sialic component of different molecules, are probably one of the most crucial enzymatic families. Sufficient sialylation of vascular endothelium defines its susceptibility to an atherogenic plaque formation. Moreover, the desialylation of LDL provokes an accumulation of cholesterol and lipids in the arterial walls. According to the multiple involvements of sialic acids and related enzymes, sialidases, in the initiation and development of atherosclerosis, the deeper understanding of their exact role, as well as cellular and molecular mechanisms, will allow creating more targeted and effective therapeutic and diagnostic approaches.

An efficient method for simultaneously screening for HIV, syphilis, and HCV based on one dried blood spot sample

OBJECTIVE

The aim of this study was to optimize the parameters of a dried blood spot (DBS)-based ELISA method to simultaneously screen for anti-HIV, anti-hepatitis C virus (HCV) and anti-treponema pallidum (TP) antibodies, and investigate the assay performance.

METHODS

Experiments were performed to establish optimized parameters for a DBS-based ELISA method to simultaneously screen for anti-HIV, anti-HCV, and anti-TP antibodies. Then, 429 paired plasma and DBS samples were collected to evaluate the performance of the assay with optimized parameters. Plasma test results were used as the reference standard.

RESULTS

The optimized assay conditions were: blood volume, 70-100 μL; DBS size, whole spot; eluent volume, 500 μL; eluent, PBS with 1‰ Tween20; elution time, 4 h; elution temperature, room temperature. The overall prevalence of HIV, HCV, and TP was 6.06% (95% confidence interval [CI]: 4.07-8.87%), 27.74% (95% CI: 23.60-32.28%), and 14.92% (95% CI: 11.75-18.73%). The clinical sensitivity of the assay for anti-HIV, anti-HCV, and anti-TP antibodies was 88.46%, 98.32%, and 92.19%, respectively. The assay was 100% specificity for each analyte. The assay positive predictive value for each analyte was 100%, and the negative predictive values were >98%. Of the 429 samples, 9 DBS results were different than the plasma results; in these samples the plasma signal-to-cutoff rations were low (range, 1.40-7.81).

CONCLUSION

The DBS-based ELISA method demonstrated good performance for simultaneously screening for anti-HIV, anti-HCV, and anti-TP antibodies. DBS samples are a promising method to screen for HIV, HCV, and TP infections.

IMPORTANCE

DBS samples are a promising alternative to plasma samples, with the advantages of good sample stability, smaller blood volume, simpler storage, and easier transport. DBS sample testing is used for the diagnosis of a wide variety of pathogens, including HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV). The performance of DBS samples for the serological diagnosis of HIV, HCV, and Treponema pallidum (TP) has been demonstrated to be good in many studies, and therefore DBS is regarded as an ideal choice to screen for HIV, HCV, and TP infections, especially in difficult-access or resource-limited settings. There is no generally accepted procedure for sample collection and processing of DBS samples and there are few studies on simultaneous detection of anti-HIV, anti-HCV and anti-TP using a single DBS.

Tilapia Lake Virus Does Not Hemagglutinate Avian and Piscine Erythrocytes and NH4Cl Does Not Inhibit Viral Replication In Vitro

Tilapia lake virus (TiLV) is a negative-sense single-stranded RNA (-ssRNA) icosahedral virus classified to be the only member in the family Amnoonviridae. Although TiLV segment-1 shares homology with the influenza C virus PB1 and has four conserved motifs similar to influenza A, B, and C polymerases, it is unknown whether there are other properties shared between TiLV and orthomyxovirus. In the present study, we wanted to determine whether TiLV agglutinated avian and piscine erythrocytes, and whether its replication was inhibited by lysosomotropic agents, such as ammonium chloride (NH₄Cl), as seen for orthomyxoviruses. Our findings showed that influenza virus strain A/Puerto Rico/8 (PR8) was able to hemagglutinate turkey (Meleagris gallopavo), Atlantic salmon (Salmo salar L), and Nile tilapia (Oreochromis niloticus) red blood cells (RBCs), while infectious salmon anemia virus (ISAV) only agglutinated Atlantic salmon, but not turkey or tilapia, RBCs. In contrast to PR8 and ISAV, TiLV did not agglutinate turkey, Atlantic salmon, or tilapia RBCs. qRT-PCR analysis showed that 30 mM NH₄Cl, a basic lysosomotropic agent, neither inhibited nor enhanced TiLV replication in E-11 cells. There was no difference in viral quantities in the infected cells with or without NH₄Cl treatment during virus adsorption or at 1, 2, and 3 h post-infection. Given that hemagglutinin proteins that bind RBCs also serve as ligands that bind host cells during virus entry leading to endocytosis in orthomyxoviruses, the data presented here suggest that TiLV may use mechanisms that are different from orthomyxoviruses for entry and replication in host cells. Therefore, future studies should seek to elucidate the mechanisms used by TiLV for entry into host cells and to determine its mode of replication in infected cells.