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Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21256823


Assessment of the kinetics of SARS-CoV-2 antibodies is essential to predict protection against reinfection and durability of vaccine protection. Here, we longitudinally measured Spike (S) and Nucleocapsid (N)-specific antibodies in 1,309 healthcare workers (HCW) including 393 convalescent COVID-19 and 916 COVID-19 negative HCW up to 405 days. From M1 to M7-9 after infection, SARS-CoV-2 antibodies decreased moderately in convalescent HCW in a biphasic model, with men showing a slower decay of anti-N (p=0.02), and a faster decay of anti-S (p=0.0008) than women. At M11-13, anti-N antibodies dramatically decreased (half-life: 210 days) while anti-S stabilized (half-life: 630 days) at a median of 2.41 log Arbitrary Units (AU)/mL (Interquartile Range (IQR): 2.11 -2.75). One case of reinfection was recorded in convalescent HCW (0.47 per 100 person-years) versus 50 in COVID-19 negative HCW (10.11 per 100 person-years). Correlation with live-virus neutralization assay revealed that variants D614G and B.1.1.7, but not B.1.351, were sensitive to anti-S antibodies at 2.3 log AU/mL, while IgG [≥] 3 log AU/mL neutralized all three variants. After SARS-CoV-2 vaccination, anti-S levels reached 4 logs regardless of pre-vaccination IgG levels, type of vaccine, and number of doses. Our study demonstrates a long-term persistence of anti-S IgG antibodies that may protect against reinfection. By significantly increasing cross-neutralizing antibody titers, a single-dose vaccination strengthens protection against escape mutants.

Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-20230466


The evolution of SARS-CoV-2 humoral response in infected individuals remains poorly characterized. Here, we performed a longitudinal study of sera from 308 RT-qPCR+ individuals with mild disease, collected at two time-points, up to 6 months post-onset of symptoms (POS). We performed two anti-S and one anti-N serology assays and quantified neutralizing antibodies (NAbs). At month 1 (M1), males, individuals > 50 years of age or with a body mass index (BMI) > 25 exhibited higher levels of antibodies. Antibody levels decreased over time. At M3-6, anti-S antibodies persisted in 99% of individuals while anti-N IgG were measurable in only 59% of individuals. The decline in anti-S and NAbs was faster in males than in females, independently of age and BMI. Our results show that some serology tests are less reliable overtime and suggest that the duration of protection after SARS-CoV-2 infection or vaccination will be different in women and men.

Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-20132449


BackgroundIn the background of the current COVID-19 pandemic, serological tests are being used to assess past infection and immunity against SARS-CoV-2. This knowledge is paramount to determine the transmission dynamics of SARS-CoV-2 through the post pandemic period. Several individuals belonging to households with an index COVID-19 patient, reported symptoms of COVID-19 but discrepant serology results. MethodsHere we investigated the humoral and cellular immune responses against SARS-CoV-2 in seven families, including nine index patients and eight contacts, who had evidence of serological discordances within the households. Ten unexposed healthy donors were enrolled as controls. ResultsAll index patients recovered from a mild COVID-19. They all developed anti-SARS-CoV-2 antibodies and a significant T cell response detectable up to 69 days after symptom onset. Six of the eight contacts reported COVID-19 symptoms within 1 to 7 days after the index patients but all were SARS-CoV-2 seronegative. Six out of eight contacts developed a SARS-CoV-2-specific T cell response against structural and/or accessory proteins that lasts up to 80 days post symptom onset suggesting a past SARS-CoV-2 infection. ConclusionExposure to SARS-CoV-2 can induce virus-specific T cell responses without seroconversion. T cell responses may be more sensitive indicators of SARS-Co-V-2 exposure than antibodies. Our results indicate that epidemiological data relying only on the detection of SARS-CoV-2 antibodies may lead to a substantial underestimation of prior exposure to the virus.

Preprint Dans Anglais | bioRxiv | ID: ppbiorxiv-156166


Rapid and accurate diagnosis is crucial for successful outbreak containment. During the current coronavirus disease 2019 (COVID-19) public health emergency, the gold standard for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection diagnosis is the detection of viral RNA by reverse transcription (RT)-PCR. Additional diagnostic methods enabling the detection of current or past SARS-CoV-2 infection would be highly beneficial to ensure the timely diagnosis of all infected and recovered patients. Here, we investigated several serological tools, i.e., two immunochromatographic lateral flow assays (LFA-1 (Biosynex COVID-19 BSS) and LFA-2 (COVID-19 Sign IgM/IgG)) and two enzyme-linked immunosorbent assays (ELISAs) detecting IgA (ELISA-1 Euroimmun), IgM (ELISA-2 EDI) and/or IgG (ELISA-1 and ELISA-2) based on well-characterized panels of serum samples from patients and healthcare workers with PCR-confirmed COVID-19 and from SARS-CoV-2-negative patients. A total of 272 serum samples were used, including 62 serum samples from hospitalized patients (panel 1 and panel 3), 143 serum samples from healthcare workers (panel 2) diagnosed with COVID-19 and 67 serum samples from negative controls. Diagnostic performances of each assay were assessed according to days after symptom onset (dso) and the antigenic format used by manufacturers. We found overall sensitivities ranging from 69% to 93% on panels 1 and 2 and specificities ranging from 83% to 98%. The clinical sensitivity varied greatly according to the panel tested and the dso. The assays we tested showed poor mutual agreement. A thorough selection of serological assays for the detection of ongoing or past infections is advisable.

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