Biology subjects

Thibault, V.

Publications and source records attributed to Thibault, V..

4 recordsLinked to original sources

bioRxiv2024

What challenges remain in harmonizing cytomegalovirus viral load quantification across laboratories?

Cytomegalovirus (CMV) infection monitoring is a key element in the management of immunocompromised patients. CMV DNA quantification in plasma or whole blood is the best indicator for clinicians to adjust immunosuppressive or antiviral therapies. Despite the availability of internationally standardized material, the commutability of CMV quantification results across laboratories remains inadequate. To assess inter-laboratory variability in CMV DNA quantification, we conducted a blinded study in seven independent laboratories. Each participant received a panel of 92 specimens for CMV quantification using their routinely used standard platform. While quantifications were highly correlated and reproducible, large discrepancies were observed with differences up to 1.45 log10 IU/mL between techniques for identical specimens. However, quantification scattering was lower for the WHO international standard or a commercially tested control (IQR=0.129) than for clinical specimens (0.469; p=0.0142). Blind quantification of the WHO or the commercial standard indicated that all techniques, except for fully integrated platforms, did not align well with the expected values and most platforms tended to quantify specimens and standards differently. Recalibration of all platforms against the same standard improved the spread of results, but differences of up to 1.19 log10 IU/mL remained for the same specimens. Achieving commutability in CMV quantification remains an elusive goal. Efforts should focus on improving both the assay calibrators and the run controls, which currently do not appear to simulate the unique characteristics of circulating CMV in patients. Until this is resolved, each transplanted patient should be consistently monitored by the same laboratory on the same platform.

microbiology↗

bioRxiv2022

Characterization of hepatitis B viral forms from patient plasma using velocity gradient: evidence for an excess of capsids in Dane particles enriched fractions

Hepatitis B virus (HBV) morphogenesis is characterized by a large over-production of subviral particles and recently described new forms in parallel of complete viral particles (VP). This study was designed to depict circulating viral forms in HBV infected patient plasmas, using velocity gradients and most sensitive viral markers. Plasmas from chronic hepatitis B (CHB) patients, HBeAg positive or negative, genotype D or E, were fractionated on velocity and equilibrium gradients with or without detergent treatment. Antigenic and molecular markers were measured in plasma and in each collected fraction. Fast Nycodenz velocity gradients revealed good reproducibility and provided additional information to standard equilibrium sucrose gradients. HBV-RNAs circulated as enveloped particles in all plasmas, except one, and at lesser concentrations than VP. Calculations based on standardized measurements and relative virion and subviral particle molecular stoichiometry allowed to refine the experimental approach. For the HBeAg-positive plasma, VP were accompanied by an overproduction of enveloped capsids, either containing HBs, likely corresponding to empty virions, or for the main part, devoid of this viral envelope protein. Similarly, in the HBeAg-negative sample, HBs enveloped capsids, likely corresponding to empty virions, were detected and the presence of enveloped capsids devoid of HBs protein was suspected but not clearly evidenced due to the presence of contaminating high-density subviral particles. While HBeAg largely influences HBcrAg measurement and accounts for two-thirds of HBcrAg reactivity in HBeAg-positive patients, it remains a 10 times more sensitive marker than HBsAg to characterize VP containing fractions. Using Nycodenz velocity gradients and standardized biomarkers, our study proposes a detailed characterization of circulating viral forms in chronically HBV infected patients. We provide evidence for an excess of capsids in DNA enriched fractions, likely due to the presence of empty virions but also by capsids enveloped by an HBs free lipid layer. Identification of this new circulating viral particle sets the basis for studies around the potential role of these entities in hepatitis B pathogeny and their physiological regulation.

microbiology↗

bioRxiv2021

SARS-CoV2 envelop proteins reshape the serological responses of COVID-19 patients

The SARS-CoV-2 pandemic has elicited a unique international mobilization of the scientific community to better understand this coronavirus and its associated disease and to develop efficient tools to combat infection. Similar to other coronavirae, SARS-CoV-2 hijacks the host cell complex secretory machinery to produce properly folded viral proteins that will compose the nascent virions; including Spike, Envelope and Membrane proteins, the most exposed membrane viral proteins to the host immune system. Antibody response is part of the anti-viral immune arsenal that infected patients develop to fight viral particles in the body. Herein, we investigate the immunogenic potential of Spike (S), Envelope (E) and Membrane (M) proteins using a human cell-based system to mimic membrane insertion and N-glycosylation. We show that both S and M proteins elicit the production of specific IgG, IgM and IgA in SARS-CoV-2 infected patients. Elevated Ig responses were observed in COVID+ patients with moderate and severe forms of the disease. Finally, when SARS-CoV-2 Spike D614 and G614 variants were compared, reduced Ig binding was observed with the Spike G614 variant. Altogether, this study underlines the needs for including topological features in envelop proteins to better characterize the serological status of COVID+ patients, points towards an unexpected immune response against the M protein and shows that our assay could represent a powerful tool to test humoral responses against actively evolving SARS-CoV-2 variants and vaccine effectiveness.

cell biology↗

bioRxiv2020

Performances of NeuMoDx, a random-access system for HBV-DNA and HCV-RNA quantification

Viral loads (VL) monitoring for hepatitis B and C is essential to evaluate disease progression and treatment response. Automated, random-access rapid systems are becoming standard to provide reliable VL to clinicians. The aim of this study was to evaluate the analytical performances of the recently launched NeuMoDx for HBV-DNA and HCV-RNA quantification. Clinical samples routinely quantified on the Beckman-Veris system were either retrospectively (frozen samples; HBV n=178, HCV n=249), or in parallel (fresh primary tubes; HBV n=103, HCV n=124) tested using NeuMoDx. Linearity range was assessed on serial dilutions of high tittered plasmas containing different genotypes for HBV (A-E, n=10) and HCV (1a-b, 2-5, n=12). Overall test failure, mostly internal control amplification failure, was 2.3% and was not influenced by matrix types. For HBV-VL, Kappa agreement was 74%, with 27 (12.6%) discrepancies. Correlation between HBV assays on 72 quantified samples by both methods was excellent (r=0.963) with a mean bias (NeuMoDx-Veris) of 0.21 log IU/mL. For HCV-VL, Kappa agreement reached 94%, with 9 (2.8%) discrepancies. The r-correlation factor between assays on 104 samples was 0.960 with a mean bias of -0.14 log IU/mL (NeuMoDx-Veris). Serial dilutions confirmed the claimed linear ranges for all HBV and HCV genotypes. The mean turnaround time was 72 [55-101] for HBV and 96 [78-133] for HCV. These results obtained on the NeuMoDx confirmed the overall good functionality of the system with a short turn-around-time, full traceability and easy handling. These results on HBV- and HCV-VL look promising and should be challenged with further comparisons.

microbiology↗