Biology subjects

Marcelin, A.-G.

Publications and source records attributed to Marcelin, A.-G..

4 recordsLinked to original sources

bioRxiv2021

XAV-19, a novel swine glyco-humanized polyclonal antibody against SARS-CoV-2 spike, efficiently neutralizes B.1.1.7 British and B.1.351 South-African variants.

Amino acid substitutions and deletions in Spike protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants can reduce the effectiveness of monoclonal antibodies (mAbs). In contrast, heterologous polyclonal antibodies raised against S protein, through the recognition of multiple target epitopes, have the potential to maintain neutralization capacities. XAV-19 is a swine glyco-humanized polyclonal neutralizing antibody raised against the receptor binding domain (RBD) of the Wuhan-Hu-1 Spike protein of SARS-CoV-2. XAV-19 target epitopes were found distributed all over the RBD and particularly cover the receptor binding motives (RBM), in direct contact sites with the Angiotensin Converting Enzyme-2 (ACE-2). Therefore, in Spike/ACE2 interaction assays, XAV-19 showed potent neutralization capacities of the original Wuhan Spike and of the United Kingdom (Alpha/B.1.1.7) and South African (Beta/B.1.351) variants. These results were confirmed by cytopathogenic assays using Vero E6 and live virus variants including the Brazil (Gamma/P.1) and the Indian (Delta/B.1.617.2) variants. In a selective pressure study with the Beta strain on Vero E6 cells conducted over 1 month, no mutation was associated with addition of increasing doses XAV-19. The potential to reduce viral load in lungs was confirmed in a human ACE2 transduced mouse model. XAV-19 is currently evaluated in patients hospitalized for COVID-19-induced moderate pneumonia in a phase 2a-2b (NCT04453384) where safety was already demonstrated and in an ongoing 2/3 trial (NCT04928430) to evaluate the efficacy and safety of XAV-19 in patients with moderate-to-severe COVID-19. Owing to its polyclonal nature and its glyco-humanization, XAV-19 may provide a novel safe and effective therapeutic tool to mitigate the severity of coronavirus disease 2019 (Covid-19) including the different variants of concern identified so far.

immunology↗

bioRxiv2021

Neutralization heterogeneity of United Kingdom and South-African SARS CoV-2 variants in BNT162b2-vaccinated or convalescent COVID-19 healthcare workers

There are concerns about neutralizing antibodies (NAb) potency against the newly emerged VOC202012/01 (UK) and 501Y.V2 (SA) SARS-CoV-2 variants in mRNA-vaccinated subjects and in recovered COVID-19 patients. We used a viral neutralization test with a strict 100% neutralizing criterion on UK and SA clinical isolates in comparison with a globally distributed D614G SARS-CoV-2 strain. In two doses BNT162b2-vaccinated healthcare workers (HCW), despite heterogeneity in neutralizing capacity against the three SARS-CoV-2 strains, most of the sera harbored at least a NAb titer [≥] 1:10 suggesting a certain humoral protection activity either on UK or SA variants. However, six months after mild forms of COVID-19, an important proportion of HCW displayed no neutralizing activity against SA strain. This result supports strong recommendations for vaccination of previously infected subjects.

microbiology↗

bioRxiv2021

In silico investigation of the new UK (B.1.1.7) and South African (501Y.V2) SARS-CoV-2 variants with a focus at the ACE2-Spike RBD interface

SARS-CoV-2 exploits angiotensin-converting enzyme 2 (ACE2) as a receptor to invade cells. It has been reported that the UK and South African strains may have higher transmission capabilities, eventually due to amino acid substitutions on the SARS-CoV-2 Spike protein. The pathogenicity seems modified but is still under investigation. Here we used the experimental structure of the Spike RBD domain co-crystallized with part of the ACE2 receptor and several in silico methods to analyze the possible impacts of three amino acid replacements (Spike K417N, E484K, N501Y) with regard to ACE2 binding. We found that the N501Y replacement in this region of the interface (present in both UK and South African strains) should be favorable for the interaction with ACE2 while the K417N and E484K substitutions (South African) would seem unfavorable. It is unclear if the N501Y substitution in the South African strain could counterbalance the predicted less favorable (regarding binding) K417N and E484K Spike replacements. Our finding suggests that, if indeed the South African strain has a high transmission level, this could be due to the N501Y replacement and/or to substitutions in regions outside the direct Spike-ACE2 interface. HihglightsO_LITransmission of the UK and possibly South African SARS-CoV-2 strains appears substantially increased compared to other variants C_LIO_LIThis could be due, in part, to increased affinity between the variant Spike proteins and ACE2 C_LIO_LIWe investigated in silico the 3D structure of the Spike-ACE2 complex with a focus on Spike K417N, E484K and N501Y C_LIO_LIThe N501Y substitution is predicted to increase the affinity toward ACE2 (UK strain) with subsequent enhanced transmissibility and possibly pathogenicity C_LIO_LIAdditional substitutions at positions 417 and 484 (South African strain) may pertub the interaction with ACE2 raising questions about transmissibility and pathogenicity C_LI

bioinformatics↗

bioRxiv2020

Multicenter comparison of the Cobas 6800 system with the RealStar RT-PCR kit for the detection of SARS-CoV-2

BackgroundRT-PCR testing is crucial in the diagnostic of SARS-CoV-2 infection. The use of reliable and comparable PCR assays is a cornerstone to allow use of different PCR assays depending on the local equipment. In this work, we provide a comparison of the Cobas(R) (Roche) and the RealStar(R) assay (Altona). MethodsAssessment of the two assays was performed prospectively in three reference Parisians hospitals, using 170 clinical samples. They were tested with the Cobas(R) assay, selected to obtain a distribution of cycle threshold (Ct) as large as possible, and tested with the RealStar assay with three largely available extraction platforms: QIAsymphony (Qiagen), MagNAPure (Roche) and NucliSENS-easyMag (BioMerieux). ResultsOverall, the agreement (positive for at least one gene) was 76%. This rate differed considerably depending on the Cobas Ct values for gene E: below 35 (n = 91), the concordance was 99%. Regarding the positive Ct values, linear regression analysis showed a determination correlation (R2) of 0.88 and the Deming regression line revealed a strong correlation with a slope of 1.023 and an intercept of -3.9. Bland-Altman analysis showed that the mean difference (Cobas(R) minus RealStar(R)) was + 3.3 Ct, with a SD of + 2.3 Ct. ConclusionsIn this comparison, both RealStar(R) and Cobas(R) assays provided comparable qualitative results and a high correlation when both tests were positive. Discrepancies exist after 35 Ct and varied depending on the extraction system used for the RealStar(R) assay, probably due to a low viral load close to the detection limit of both assays.

microbiology↗