ABSTRACT
The virus neutralization test (VNT) is the reference for the assessment of the functional ability of neutralizing antibodies (NAb) to block SARS-CoV-2 entry into cells. New competitive immunoassays measuring antibodies preventing interaction between the spike protein and its cellular receptor are proposed as surrogate VNT (sVNT). We tested three commercial sVNT (a qualitative immunochromatographic test and two quantitative immunoassays named YHLO and TECO) together with a conventional anti-spike IgG assay (bioMerieux) in comparison with an in-house plaque reduction neutralization test (PRNT50) using the original 19A strain and different variants of concern (VOC), on a panel of 306 sera from naturally-infected or vaccinated patients. The qualitative test was rapidly discarded because of poor sensitivity and specificity. Areas under the curve of YHLO and TECO assays were, respectively, 85.83 and 84.07 (p-value >0.05) using a positivity threshold of 20 for PRNT50, and 95.63 and 90.35 (p-value =0.02) using a threshold of 80. However, the performances of YHLO and bioMerieux were very close for both thresholds, demonstrating the absence of added value of sVNT compared to a conventional assay for the evaluation of the presence of NAb in seropositive subjects. In addition, the PRNT50 assay showed a reduction of NAb titers towards different VOC in comparison to the 19A strain that could not be appreciated by the commercial tests. Despite the good correlation between the anti-spike antibody titer and the titer of NAb by PRNT50, our results highlight the difficulty to distinguish true NAb among the anti-RBD antibodies with commercial user-friendly immunoassays.
ABSTRACT
With the availability of vaccines, commercial assays detecting anti-SARS-CoV-2 antibodies (Ab) evolved towards quantitative assays directed to the spike glycoprotein or its receptor binding domain (RBD). The main objective of the present study was to compare the Ab titers obtained with quantitative commercial binding Ab assays, after 1 dose (convalescent individuals) or 2 doses (naive individuals) of vaccine, in healthcare workers (HCW). Antibody titers were measured in 255 sera (from 150 HCW) with 5 quantitative immunoassays (Abbott RBD IgG II quant, bioMerieux RBD IgG, DiaSorin Trimeric spike IgG, Siemens Healthineers RBD IgG, Wantai RBD IgG). One qualitative total antibody anti RBD detection assay (Wantai) was used to detect previous infection before vaccination. The results are presented in binding Ab units (BAU)/mL after application, when possible, of a conversion factor provided by the manufacturers and established from a World Health Organization (WHO) internal standard. There was a 100% seroconversion with all assays evaluated after two doses of vaccine. With assays allowing BAU/ml correction, Ab titers were correlated (Pearson correlation coefficient, {rho}, range: 0.85-0.94). The titer differences varied by a mean of 10.6% between Siemens and bioMerieux assays to 60.9% between Abbott and DiaSorin assays. These results underline the importance of BAU conversion for the comparison of Ab titer obtained with the different quantitative assays. However, significant differences persist, notably, between kits detecting Ab against the different antigens. A true standardization of the assays would be to include the International Standard in the calibration of each assays to express the results in IU/mL.
ABSTRACT
ObjectivesWe evaluated widely-used SARS-CoV-2 serological tests and their potential association with virus neutralization test (VNT) in a cohort of mild COVID-19 patients. MethodsA total of 439 specimens were longitudinally collected from 76 healthcare workers with RT-PCR-confirmed mild COVID-19. Nine serological assays developed by leading global companies (Abbott, DiaSorin, Siemens, Bio-Rad, Wantai, bioMerieux, Euroimmun) were assessed. For each test the sensitivity to detect SARS-CoV-2 antibodies was determined weekly after symptom onset. Correlation and concordance were assessed using the Spearman and Cohens Kappa coefficients, respectively. Positive percent agreement and negative percent agreement (NPA) with the VNT were also determined. ResultsThe Wantai Total Ab assay targeting the receptor binding domain (RBD) within the S protein presented the best sensitivity at different times during the course of disease. The best correlation between antibody level and neutralizing antibody titer was found with the Euroimmun S1-based IgA assay (Spearman coefficient [95%CI]: 0.71 [0.61-0.79]). A moderate concordance (Kappa [95%CI]: 0.43[0.23-0.63]) as well as the lowest NPA (33%) was found between the Wantai Total Ab assay and the VNT. Compared to the Wantai Total Ab assay, other total Ab or IgG assays targeting the S or the RBD (bioMerieux, DiaSorin, Siemens,) were more concordant with the VNT (Kappa>0.7 for the three tests) and had a higher NPA (range: 90% to 97%). ConclusionsAlthough some assays presented a better concordance with VNT than others, the present findings emphasize that commercialized serological tests including those targeting the RBD cannot substitute VNT for the assessment of functional antibody response.
ABSTRACT
IntroductionA new respiratory virus, SARS-CoV-2, has emerged and spread worldwide since late 2019. This study aims at analyzing clinical presentation on admission and the determinants associated with direct admission or transfer to intensive care units (ICUs) in hospitalized COVID-19 patients. Patients and MethodsIn this prospective hospital-based study, socio-demographic, clinical and biological characteristics, on admission, of adult COVID-19 hospitalized patients were prospectively collected and analyzed. The outcome was admission/transfer to intensive care units compared with total hospital stay in medical wards according to patient characteristics. ResultsOf the 412 patients included, 325 were discharged and 87 died in hospital. Multivariable regression showed increasing odds of admission/transfer to ICUs with male gender (OR, 1.99 [95%CI, 1.07-3.73]), temperature (OR, 1.37 [95% CI, 1.01-1.88] per degree Celsius increase), abnormal lung auscultation on admission (OR, 2.62 [95% CI, 1.40-4.90]), elevated level of CRP (OR, 6.96 [95% CI, 1.45-33.35 for CRP>100mg/L vs CRP<10mg/L). Increased time was observed between symptom onset and hospital admission (OR, 4.82 [95% CI, 1.61-14.43] for time >10 days vs time <3 days) and monocytopenia (OR, 2.49 [95% CI, 1.29-4.82]). Monocytosis was associated with lower risk of admission/transfer to ICUs (OR, 0.25 [95% CI, 0.05-1.13]). ConclusionsClinical and biological features on admission and time until admission were associated with admission to ICUs. Signs to predict worsening on admission could be partially associated with the time until admission. This finding reinforces the need for appropriate guidelines to manage COVID-19 patients in this time window.
ABSTRACT
IntroductionThe newly identified SARS-CoV2 can cause serious acute respiratory infections such as pneumonia with a mortality rate of approximately 2% to 4%. In the current context of high incidence rates of SARS-CoV2 in the community, a significant increase in the rate of nosocomial transmission is expected. The risk of nosocomial transmission could even be higher in low-income countries that have fragile healthcare systems. This protocol is intended to study and document suspected or confirmed cases of nosocomial SARS-CoV2 infection, the clinical spectrum and the determinants (risk factors/protective) at participating hospitals. Methods and analysisThis will be an international multicentre prospective, observational, hospital-based study in adults and children. It will include volunteer patients, care givers and healthcare professionals in France and hospitals affiliated with the GABRIEL network. Demographic and clinical data will be collected using case-report forms designed especially for the purpose of the project. A nasopharyngeal swab will be collected and tested for SARS-CoV2 by RT-PCR. Characteristics of the study participants, the proportion of confirmed nosocomial SARS-CoV2 infections relative to all patients with syndromes suggestive of 2019-nCoV infection will be analysed. Appropriate multivariate modelling will be used to identify the determinants associated with nosocomial onset. Ethics and disseminationThis study was approved by the clinical research and committee of Ile de France V on March 8, 2020. Registration detailsThe trial was registered in ClinicalTrials (NCT04290780). Strengths and limitations of the study[tpltrtarr] This prospective study will generate and evaluate original data on nosocomial SARS-CoV2 infection in France and in the low-income countries of the GABRIEL network using the same protocol and standardised CRF. [tpltrtarr]The results will provide the opportunity to compare the management of nosocomial Covid-19 infection in different settings for mutual exchanges and optimisation. [tpltrtarr]The results will make it possible to refine the definition of nosocomial SARS-CoV2 infection, strengthen preventive campaigns for in-hospital transmission of SARS-CoV2 and pave the way for new recommendations in terms of preventive measures. [tpltrtarr]Selection bias owing to access to care in different populations and bias owing to the extent of access to personal protective equipment, in particular, in low-income countries may occur. [tpltrtarr]The non-exhaustivity of the confounders to be collected should be considered for interpretation of the results.
ABSTRACT
We present the first genetic characterization of a COVID-19 cluster in Europe using metagenomic next-generation sequencing (mNGS). Despite low viral loads, the mNGS workflow used herein allowed to characterize the whole genome sequences of SARS-CoV2 isolated from an asymptomatic patient, in 2 clinical samples collected 1 day apart. Comparison of these sequences suggests viral evolution with development of quasispecies. In addition, the present workflow identified a new deletion in nsp2 (Asp268Del) which was found in all 3 samples originating from this cluster as well as in 37 other viruses collected in England and in Netherlands, suggesting the spread of this deletion in Europe. The impact of Asp268Del on SARS-CoV-2 transmission and pathogenicity, as well as on PCR performances and anti-viral strategy should be rapidly evaluated in further studies.
