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Mpox virus (MPXV) caused a multi-country outbreak in non-endemic areas in 2022. The Modified Vaccinia Ankara (MVA)-based vaccine was used as prophylaxis, but its effectiveness remains poorly characterized. Here, we developed two assays for quantification of neutralizing antibodies (NAbs), using MVA-GFP or a recently isolated MPXV. We measured NAb levels in 470 sera from control, MPXV-infected or MVA-vaccinated individuals. Various levels of MVA NAbs were detected after infection, historic smallpox or MVA vaccination. MPXV was barely sensitive to neutralization. Addition of complement enhanced detection of responsive individuals and NAb levels. Anti-MVA and -MPXV NAbs were observed in 94% and 82% of infected individuals, respectively, and 92% and 56% of MVA vaccinees, respectively. NAb titers were higher in individuals born before 1980, highlighting the impact of historic smallpox vaccination on humoral immunity. Altogether, our results indicate that MPXV neutralization is complement-dependent and help uncover the mechanisms underlying vaccine effectiveness.SUMMARYIn 2022, mpox virus (MPXV) caused an unprecedented pandemic outbreak in non-endemic areas. The efficacy of currently available third generation MVA-based vaccines and the nature of the humoral response generated after MPXV infection remain poorly characterized. We established cell-based assays to measure neutralizing antibodies (NAbs) targeting MVA or MPXV. We analyzed 470 sera and detected robust levels of MVA NAbs after infection, historic smallpox vaccination or administration of MVA-based vaccines. Efficient MPXV neutralization required addition of complement. High NAb titers were measured in ancient smallpox-vaccinated MPXV-infected patients, suggesting a potential cross-protection mediated by hybrid immunity.

The SARS-CoV-2 Omicron BA.1 variant has been supplanted in many countries by the BA.2 sub-lineage. BA.2 differs from BA.1 by about 21 mutations in its spike. Human anti-spike monoclonal antibodies (mAbs) are used for prevention or treatment of COVID-19. However, the capacity of therapeutic mAbs to neutralize BA.1 and BA.2 remains poorly characterized. Here, we first compared the sensitivity of BA.1 and BA.2 to neutralization by 9 therapeutic mAbs. In contrast to BA.1, BA.2 was sensitive to Cilgavimab, partly inhibited by Imdevimab and resistant to Adintrevimab and Sotrovimab. Two combinations of mAbs, Ronapreve (Casirivimab + Imdevimab) and Evusheld (Cilgavimab + Tixagevimab), are indicated as a pre-exposure prophylaxis in immunocompromised persons at risk of severe disease. We analyzed sera from 29 such individuals, up to one month after administration of Ronapreve and/or Evusheld. After treatment, all individuals displayed elevated antibody levels in their sera and neutralized Delta with high titers. Ronapreve recipients did not neutralize BA.1 and weakly impaired BA.2. With Evusheld, neutralization of BA.1 and BA.2 was detected in 19 and 29 out of 29 patients, respectively. As compared to Delta, titers were more severely decreased against BA.1 (344-fold) than BA.2 (9-fold). We further report 4 breakthrough Omicron infections among the 29 participants. Therefore, BA.1 and BA.2 exhibit noticeable differences in their sensitivity to therapeutic mAbs. Anti-Omicron activity of Ronapreve, and to a lesser extent that of Evusheld, is reduced in patients’ sera, a phenomenon associated with decreased clinical efficacy.

SARS-CoV-2 lineages are continuously evolving. As of December 2021, the AY.4.2 Delta sub-lineage represented 20 % of sequenced strains in UK and has been detected in dozens of countries. It has since then been supplanted by the Omicron variant. AY.4.2 displays three additional mutations (T95I, Y145H and A222V) in the N-terminal domain (NTD) of the spike when compared to the original Delta variant (B.1.617.2) and remains poorly characterized. Here, we analyzed the fusogenicity of the AY.4.2 spike and the sensitivity of an authentic AY.4.2 isolate to neutralizing antibodies. The AY.4.2 spike exhibited similar fusogenicity and binding to ACE2 than Delta. The sensitivity of infectious AY.4.2 to a panel of monoclonal neutralizing antibodies was similar to Delta, except for the anti-RBD Imdevimab, which showed incomplete neutralization. Sensitivity of AY.4.2 to sera from individuals having received two or three doses of Pfizer or two doses of AstraZeneca vaccines was reduced by 1.7 to 2.1 fold, when compared to Delta. Our results suggest that mutations in the NTD remotely impair the efficacy of anti-RBD antibodies. The temporary spread of AY.4.2 was not associated with major changes in spike function but rather to a partially reduced neutralization sensitivity.

The SARS-CoV-2 Omicron variant was first identified in November 2021 in Botswana and South Africa1,2. It has in the meantime spread to many countries and is expected to rapidly become dominant worldwide. The lineage is characterized by the presence of about 32 mutations in the Spike, located mostly in the N-terminal domain (NTD) and the receptor binding domain (RBD), which may enhance viral fitness and allow antibody evasion. Here, we isolated an infectious Omicron virus in Belgium, from a traveller returning from Egypt. We examined its sensitivity to 9 monoclonal antibodies (mAbs) clinically approved or in development3, and to antibodies present in 90 sera from COVID-19 vaccine recipients or convalescent individuals. Omicron was totally or partially resistant to neutralization by all mAbs tested. Sera from Pfizer or AstraZeneca vaccine recipients, sampled 5 months after complete vaccination, barely inhibited Omicron. Sera from COVID-19 convalescent patients collected 6 or 12 months post symptoms displayed low or no neutralizing activity against Omicron. Administration of a booster Pfizer dose as well as vaccination of previously infected individuals generated an anti-Omicron neutralizing response, with titers 5 to 31 fold lower against Omicron than against Delta. Thus, Omicron escapes most therapeutic monoclonal antibodies and to a large extent vaccine-elicited antibodies.

The control of the COVID-19 epidemics has been one of top global health priorities for the last eighteen months. To that end, more reliable and easy-to-use diagnostic tests are necessary. Young children are still not eligible to vaccination and it is important to find a way to easily test this key population regularly. With that in mind, we evaluated a new innovative easy two-step self-test named COVID-VIRO ALL IN® developed by AAZ that uses a sampling nasal sponge instead of a classic nasal swab. Mirroring the previous study conducted on the first generation of COVID-VIRO® antigenic self-test, we first performed a multicentre, prospective study on 124 adults and children, in a point-of-care setting. Sensitivity, specificity and overall acceptance of the COVID-VIRO ALL IN® antigen self-test compared to RT-PCR on nasopharyngeal samples were evaluated at 93.02%, 100% and 97,5%, respectively. We then performed a multicentre, prospective, usability study to evaluate the ease of use of COVID-VIRO ALL IN® in real life on 68 laypersons, all adults. Globally, 99% of them considered the instructions material good, 98% executed the procedure well, and all of them interpreted the results correctly. The usability was then specifically investigated on 40 children and teenagers participants, comparing both COVID-VIRO® first generation and the new COVID-VIRO ALL IN®. All of them found COVID-VIRO ALL IN® much easier to use and much more comfortable. For young children, the COVID-VIRO ALL IN® self-test appears to be safer (less risk of trauma compare to nasal swabs and no liquid exposure) easier to use than classic COVID self-tests and giving immediate result which is not the case for RT-PCR done on saliva samples (currently done in routine for kids in French schools). It could be an adapted tool for future mass screening campaigns in schools or at home under adult supervision for kids from the age of 3.

The SARS-CoV-2 B.1.617 lineage emerged in October 2020 in India1–6. It has since then become dominant in some indian regions and further spread to many countries. The lineage includes three main subtypes (B1.617.1, B.1617.2 and B.1.617.3), which harbour diverse Spike mutations in the N-terminal domain (NTD) and the receptor binding domain (RBD) which may increase their immune evasion potential. B.1.617.2 is believed to spread faster than the other versions. Here, we isolated infectious B.1.617.2 from a traveller returning from India. We examined its sensitivity to monoclonal antibodies (mAbs) and to antibodies present in sera from COVID-19 convalescent individuals or vaccine recipients, in comparison to other viral lineages. B.1.617.2 was resistant to neutralization by some anti-NTD and anti-RBD mAbs, including Bamlanivimab, which were impaired in binding to the B.1.617.2 Spike. Sera from convalescent patients collected up to 12 months post symptoms and from Pfizer Comirnaty vaccine recipients were 3 to 6 fold less potent against B.1.617.2, relative to B.1.1.7. Sera from individuals having received one dose of AstraZeneca Vaxzevria barely inhibited B.1.617.2. Thus, B.1.617.2 spread is associated with an escape to antibodies targeting non-RBD and RBD Spike epitopes.

SARS-CoV-2 B.1.1.7 and B.1.351 variants emerged respectively in United Kingdom and South Africa and spread in many countries. Here, we isolated infectious B.1.1.7 and B.1.351 strains and examined their sensitivity to anti-SARS-CoV-2 antibodies present in sera and nasal swabs, in comparison with a D614G reference virus. We established a novel rapid neutralization assay, based on reporter cells that become GFP+ after overnight infection. B.1.1.7 was neutralized by 79/83 sera from convalescent patients collected up to 9 months post symptoms, almost similar to D614G. There was a mean 6-fold reduction in titers and even loss of activity against B.1.351 in 40% of convalescent sera after 9 months. Early sera from 19 vaccinated individuals were almost as potent against B.1.1.7 but less efficacious against B.1.351, when compared to D614G. Nasal swabs from vaccine recipients were not neutralizing, except in individuals who were diagnosed COVID-19+ before vaccination. Thus, faster-spreading variants acquired a partial resistance to humoral immunity generated by natural infection or vaccination, mostly visible in individuals with low antibody levels.

IntroductionThe SARS-CoV-2 pandemic has become a major public health issue worldwide. Developing and evaluating rapid and easy-to-perform diagnostic tests is an absolute priority. The current study was designed to assess diagnostic performances of an antigen-based rapid detection test (COVID-VIRO®) in a real-life setting.MethodsTwo nasopharyngeal specimens of symptomatic or asymptomatic adult patients hospitalized in the Infectious Diseases Department or voluntarily accessing the COVID-19 Screening Department of the Regional Hospital of Orléans, France, were concurrently collected. COVID VIRO® diagnostic specificity and sensitivity were assessed in comparison to real-time reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) results. A subset of patients underwent an additional oropharyngeal and/or a saliva swab for rapid testing.Results121 patients already having a confirmed infection and 127 patients having no evidence of recent or ongoing infection were enrolled, for a total of 248 couple of nasopharyngeal swab specimens. Overall COVID-VIRO® sensitivity was 96.7% (IC: 93.5%-99.9%). In asymptomatic patients, symptomatic patients having symptoms for more than 4 days and those having a RT-qPCR Cycle threshold value ≥32, sensitivity was of 100%, 95.8% and 91.9% respectively. The concordance between RT-qPCR and COVID VIRO® rapid test was 100% for the 127 patients with no SARS-CoV-2 infection.ConclusionCOVID-VIRO® test had 100% specificity and above 95% sensitivity, better than WHO recommendations (specificity ≥97-100%, sensitivity ≥80%). These rapid tests are particularly interesting for large-scale screening in Emergency Department, low resource settings and airports.

BackgroundThe SARS-CoV-2 virus is responsible for the infectious respiratory disease called COVID-19 (COronaVIrus Disease). In response to the growing COVID-19 pandemic, Rapid Diagnostic Tests (RDTs) have been developed to detect specific antibodies, IgG and IgM, to SARS-CoV-2 virus in human whole blood. We conducted a real-life study to evaluate the performance of two RDTs, COVID-PRESTO® and COVID-DUO®, compared to the gold standard, RT-PCR.MethodsRT-PCR testing of SARS-Cov-2 was performed from nasopharyngeal swab specimens collected in adult patients visiting the infectious disease department at the hospital (Orléans, France). Fingertip whole blood samples taken at different time points after onset of the disease were tested with RDTs. The specificity and sensitivity of the rapid test kits compared to test of reference (RT-PCR) were calculated.ResultsAmong 381 patients with symptoms of COVID-19 who went to the hospital for a diagnostic, 143 patients were RT-PCR negative. Results of test with RDTs were all negative for these patients, indicating a specificity of 100% for both RDTs.In the RT-PCR positive subgroup (n=238), 133 patients were tested with COVID-PRESTO® and 129 patients were tested with COVID-DUO® (24 patients tested with both). The further the onset of symptoms was from the date of collection, the greater the sensitivity. The sensitivity of COVID-PRESTO® test ranged from 10.00% for patients having experienced their 1st symptoms from 0 to 5 days ago to 100% in patients where symptoms had occurred more than 15 days before the date of tests. For COVID-DUO® test, the sensitivity ranged from 35.71% [0-5 days] to 100% (> 15 days).ConclusionCOVID-PRESTO® and DUO® RDTs turned out to be very specific (none false positive) and to be sensitive enough after 15 days from onset of symptom. These easy to use IgG/IgM combined test kits are the first ones allowing a screening with capillary blood sample, by typing from a finger prick. These rapid tests are particularly interesting for screening in low resource settings.