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1.
Preprint in English | bioRxiv | ID: ppbiorxiv-516888

ABSTRACT

Convergent evolution of SARS-CoV-2 Omicron BA.2, BA.4 and BA.5 lineages has led to the emergence of several new subvariants, including BA.2.75.2, BA.4.6. and BQ.1.1. The subvariants BA.2.75.2 and BQ.1.1 are expected to become predominant in many countries in November 2022. They carry an additional and often redundant set of mutations in the spike, likely responsible for increased transmissibility and immune evasion. Here, we established a viral amplification procedure to easily isolate Omicron strains. We examined their sensitivity to 6 therapeutic monoclonal antibodies (mAbs) and to 72 sera from Pfizer BNT162b2-vaccinated individuals, with or without BA.1/BA.2 or BA.5 breakthrough infection. Ronapreve (Casirivimab and Imdevimab) and Evusheld (Cilgavimab and Tixagevimab) lost any antiviral efficacy against BA.2.75.2 and BQ.1.1, whereas Xevudy (Sotrovimab) remained weakly active. BQ.1.1 was also resistant to Bebtelovimab. Neutralizing titers in triply vaccinated individuals were low to undetectable against BQ.1.1 and BA.2.75.2, 4 months after boosting. A BA.1/BA.2 breakthrough infection increased these titers, which remained about 18-fold lower against BA.2.75.2 and BQ.1.1, than against BA.1. Reciprocally, a BA.5 breakthrough infection increased more efficiently neutralization against BA.5 and BQ.1.1 than against BA.2.75.2. Thus, the evolution trajectory of novel Omicron subvariants facilitated their spread in immunized populations and raises concerns about the efficacy of most currently available mAbs.

2.
Preprint in English | medRxiv | ID: ppmedrxiv-22278699

ABSTRACT

The emergence of novel Omicron lineages, such as BA.5, may impact the therapeutic efficacy of anti-SARS-CoV-2 neutralizing monoclonal antibodies (mAbs). Here, we evaluated the neutralization and ADCC activity of 6 therapeutic mAbs against Delta, BA.2, BA.4 and BA.5 isolates. The Omicron sub-variants escaped most of the antibodies but remained sensitive to Bebtelovimab and Cilgavimab. Consistent with their shared spike sequence, BA.4 and BA.5 displayed identical neutralization profiles. Sotrovimab was the most efficient at eliciting ADCC. We also analyzed 121 sera from 40 immunocompromised individuals up to 6 months after infusion of 1200 mg of Ronapreve (Imdevimab + Casirivimab), and 300 or 600 mg of Evusheld (Cilgavimab + Tixagevimab). Sera from Ronapreve-treated individuals did not neutralize Omicron subvariants. Evusheld-treated individuals neutralized BA.2 and BA.5, but titers were reduced by 41- and 130-fold, respectively, compared to Delta. A longitudinal evaluation of sera from Evusheld-treated patients revealed a slow decay of mAb levels and neutralization. The decline was more rapid against BA.5. Our data shed light on the antiviral activities of therapeutic mAbs and the duration of effectiveness of Evusheld pre-exposure prophylaxis.

3.
Preprint in English | bioRxiv | ID: ppbiorxiv-495733

ABSTRACT

SARS-CoV-2 infects cells by attachment to its receptor - the angiotensin converting enzyme 2 (ACE2). Regardless of the wealth of structural data, little is known about the physicochemical mechanism of interactions of the viral spike (S) protein with ACE2 and how this mechanism has evolved during the pandemic. Here, we applied experimental and computational approaches to characterize the molecular interaction of S proteins from SARS-CoV-2 variants of concern (VOC). Data on kinetics, activation- and equilibrium thermodynamics of binding of the receptor binding domain (RBD) from VOC with ACE2 as well as data from computational protein electrostatics revealed a profound remodeling of the physicochemical characteristics of the interaction during the evolution. Thus, as compared to RBDs from Wuhan strain and other VOC, Omicron RBD presented as a unique protein in terms of conformational dynamics and types of non-covalent forces driving the complex formation with ACE2. Viral evolution resulted in a restriction of the RBD structural dynamics, and a shift to a major role of polar forces for ACE2 binding. Further, we investigated how the reshaping of the physicochemical characteristics of interaction affect the binding specificity of S proteins. Data from various binding assays revealed that SARS-CoV-2 Wuhan and Omicron RBDs manifest capacity for promiscuous recognition of unrelated human proteins, but they harbor distinct reactivity patterns. These findings might contribute for mechanistic understanding of the viral tropism, and capacity to evade immune responses during evolution.

4.
Preprint in English | bioRxiv | ID: ppbiorxiv-492832

ABSTRACT

SARS-CoV-2 remained genetically stable during the first three months of the pandemic, before acquiring a D614G spike mutation that rapidly spread worldwide, and then generating successive waves of viral variants with increasingly high transmissibility. We set out to evaluate possible epistatic interactions between the early occurring D614G mutation and the more recently emerged cleavage site mutations present in spike of the Alpha, Delta, and Omicron variants of concern. The P681H/R mutations at the S1/S2 cleavage site increased spike processing and fusogenicity but limited its incorporation into pseudoviruses. In addition, the higher cleavage rate led to higher shedding of the spike S1 subunit, resulting in a lower infectivity of the P681H/R-carrying pseudoviruses compared to those expressing the Wuhan wild-type spike. The D614G mutation increased spike expression at the cell surface and limited S1 shedding from pseudovirions. As a consequence, the D614G mutation preferentially increased the infectivity of P681H/R-carrying pseudoviruses. This enhancement was more marked in cells where the endosomal route predominated, suggesting that more stable spikes could better withstand the endosomal environment. Taken together, these findings suggest that the D614G mutation stabilized S1/S2 association and enabled the selection of mutations that increased S1/S2 cleavage, leading to the emergence of SARS-CoV-2 variants expressing highly fusogenic spikes. AUTHOR SUMMARYThe successive emergence of SARS-CoV-2 variants is fueling the COVID pandemic, thus causing a major and persistent public health issue. The parameters involved in the emergence of variants with higher pathogenic potential remain incompletely understood. The first SARS-CoV-2 variant that spread worldwide in early 2020 carried a D614G mutation in the viral spike, making this protein more stable in its cleaved form at the surface of virions, and resulting in viral particles with higher infectious capacity. The Alpha and the Delta variants that spread in late 2020 and early 2021, respectively, proved increasingly transmissible and pathogenic when compared to the original SARS-CoV-2 strain. Interestingly, Alpha and Delta both carried mutations in a spike cleavage site that needs to be processed by cellular proteases prior to viral entry. The cleavage site mutations P681H/R made the Alpha and Delta spikes more efficient at viral fusion, by generating a higher fraction of cleaved spikes subunits S1 and S2. We show here that the early D614G mutation and the late P681H/R mutations act synergistically to increase the fusion capacity of SARS-CoV-2 variants. Specifically, viruses with increased spike cleavage due to P681H/R were even more dependent on the stabilizing effect of D614G mutation, which limited the shedding of cleaved S1 subunits from viral particles. These findings suggest that the worldwide spread of the D614G mutation was a prerequisite to the emergence of more pathogenic SARS-CoV-2 variants with highly fusogenic spikes.

5.
Preprint in English | bioRxiv | ID: ppbiorxiv-486719

ABSTRACT

Memory B-cell and antibody responses to the SARS-CoV-2 spike protein contribute to long-term immune protection against severe COVID-19, which can also be prevented by antibody-based interventions. Here, wide SARS-CoV-2 immunoprofiling in COVID-19 convalescents combining serological, cellular and monoclonal antibody explorations, revealed humoral immunity coordination. Detailed characterization of a hundred SARS-CoV-2 spike memory B-cell monoclonal antibodies uncovered diversity in their repertoire and antiviral functions. The latter were influenced by the targeted spike region with strong Fc-dependent effectors to the S2 subunit and potent neutralizers to the receptor binding domain. Amongst those, Cv2.1169 and Cv2.3194 antibodies cross-neutralized SARS-CoV-2 variants of concern including Omicron BA.1 and BA.2. Cv2.1169, isolated from a mucosa-derived IgA memory B cell, demonstrated potency boost as IgA dimers and therapeutic efficacy as IgG antibodies in animal models. Structural data provided mechanistic clues to Cv2.1169 potency and breadth. Thus, potent broadly neutralizing IgA antibodies elicited in mucosal tissues can stem SARS-CoV-2 infection, and Cv2.1169 and Cv2.3194 are prime candidates for COVID-19 prevention and treatment.

6.
Preprint in English | medRxiv | ID: ppmedrxiv-22272066

ABSTRACT

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.

7.
Preprint in English | bioRxiv | ID: ppbiorxiv-478159

ABSTRACT

As the COVID-19 pandemic continues and new SARS-CoV-2 variants of concern emerge, the adaptive immunity initially induced by the first-generation COVID-19 vaccines wains and needs to be strengthened and broadened in specificity. Vaccination by the nasal route induces mucosal humoral and cellular immunity at the entry point of SARS-CoV-2 into the host organism and has been shown to be the most effective for reducing viral transmission. The lentiviral vaccination vector (LV) is particularly suitable for this route of immunization because it is non-cytopathic, non-replicative and scarcely inflammatory. Here, to set up an optimized cross-protective intranasal booster against COVID-19, we generated an LV encoding stabilized Spike of SARS-CoV-2 Beta variant (LV::SBeta-2P). mRNA vaccine-primed and -boosted mice, with waning primary humoral immunity at 4 months post-vaccination, were boosted intranasally with LV::SBeta-2P. Strong boost effect was detected on cross-sero-neutralizing activity and systemic T-cell immunity. In addition, mucosal anti-Spike IgG and IgA, lung resident B cells, and effector memory and resident T cells were efficiently induced, correlating with complete pulmonary protection against the SARS-CoV-2 Delta variant, demonstrating the suitability of the LV::SBeta-2P vaccine candidate as an intranasal booster against COVID-19.

8.
Preprint in English | bioRxiv | ID: ppbiorxiv-475248

ABSTRACT

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.

9.
Preprint in English | bioRxiv | ID: ppbiorxiv-472630

ABSTRACT

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.

10.
Preprint in English | bioRxiv | ID: ppbiorxiv-462234

ABSTRACT

As the coronavirus disease 2019 (COVID-19) pandemic continues, there is a strong need for highly potent monoclonal antibodies (mAbs) that are resistant against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants of concern (VoCs). Here, we evaluate the potency of a previously described mAb J08 against these variants using cell-based assays and delve into the molecular details of the binding interaction using cryo-EM. We show that mAb J08 has low nanomolar affinity against VoCs, binds high on the receptor binding domain (RBD) ridge and is therefore unaffected by most mutations, and can bind in the RBD-up and -down conformations. These findings further validate the phase II/III human clinical trial underway using mAb J08 as a monoclonal therapy. One Sentence SummaryPotent neutralizing monoclonal antibody J08 binds SARS-CoV-2 spike independent of known escape mutations.

11.
Preprint in English | bioRxiv | ID: ppbiorxiv-448011

ABSTRACT

Severe COVID-19 is characterized by lung abnormalities, including the presence of syncytial pneumocytes. Syncytia form when SARS-CoV-2 spike protein expressed on the surface of infected cells interacts with the ACE2 receptor on neighbouring cells. The syncytia forming potential of spike variant proteins remain poorly characterized. Here, we first assessed Alpha and Beta spread and fusion in cell cultures. Alpha and Beta replicated similarly to D614G reference strain in Vero, Caco-2, Calu-3 and primary airway cells. However, Alpha and Beta formed larger and more numerous syncytia. Alpha, Beta and D614G fusion was similarly inhibited by interferon induced transmembrane proteins (IFITMs). Individual mutations present in Alpha and Beta spikes differentially modified fusogenicity, binding to ACE2 and recognition by monoclonal antibodies. We further show that Delta spike also triggers faster fusion relative to D614G. Thus, SARS-CoV-2 emerging variants display enhanced syncytia formation. SynopsisThe Spike protein of the novel SARS-CoV-2 variants are comparative more fusogenic than the earlier strains. The mutations in the variant spike protein differential modulate syncytia formation, ACE2 binding, and antibody escape. O_LIThe spike protein of Alpha, Beta and Delta, in the absence of other viral proteins, induce more syncytia than D614G C_LIO_LIThe ACE2 affinity of the variant spike proteins correlates to their fusogenicity C_LIO_LIVariant associated mutations P681H, D1118H, and D215G augment cell-cell fusion, while antibody escape mutation E484K, K417N and {Delta}242-244 hamper it. C_LIO_LIVariant spike-mediated syncytia formation is effectively restricted by IFITMs C_LI

12.
Preprint in English | bioRxiv | ID: ppbiorxiv-445838

ABSTRACT

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.

13.
Preprint in English | medRxiv | ID: ppmedrxiv-21251633

ABSTRACT

Coordinated local mucosal and systemic immune responses following SARS-CoV-2 infection protect against COVID-19 pathologies or fail leading to severe clinical outcomes. To understand this process, we performed an integrated analysis of SARS-CoV-2 spike-specific antibodies, cytokines, viral load and 16S bacterial communities in paired nasopharyngeal swabs and plasma samples from a cohort of clinically distinct COVID-19 patients during acute infection. Plasma viral load was associated with systemic inflammatory cytokines that were elevated in severe COVID-19, and also with spike-specific neutralizing antibodies. In contrast, nasopharyngeal viral load correlated with SARS-CoV-2 humoral responses but inversely with interferon responses, the latter associating with protective microbial communities. Potential pathogenic microrganisms, often implicated in secondary respiratory infections, were associated with mucosal inflammation and elevated in severe COVID-19. Our results demonstrate distinct tissue compartmentalization of SARS-CoV-2 immune responses and highlight a role for the nasopharyngeal microbiome in regulating local and systemic immunity that determines COVID-19 clinical outcomes.

14.
Preprint in English | bioRxiv | ID: ppbiorxiv-430472

ABSTRACT

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.

15.
Preprint in English | medRxiv | ID: ppmedrxiv-20230508

ABSTRACT

A large proportion of SARS-CoV-2 infected individuals remains asymptomatic. Little is known about the extent and quality of their antiviral humoral response. Here, we analyzed antibody functions in 52 asymptomatic infected individuals, 119 mild and 21 hospitalized COVID-19 patients. We measured anti-Spike antibody levels with the S-Flow assay and mapped SARS-CoV-2 Spike- and N-targeted regions by Luminex. Neutralization, complement deposition and Antibody-Dependent Cellular Cytotoxicity (ADCC) were evaluated using replication-competent SARS-CoV-2 or reporter cell systems. We show that COVID-19 sera mediate complement deposition and kill infected cells by ADCC. Sera from asymptomatic individuals neutralize the virus, activate ADCC and trigger complement deposition. Antibody levels and activities are slightly lower in asymptomatic individuals. The different functions of the antibodies are correlated, independently of disease severity. Longitudinal samplings show that antibody functions follow similar kinetics of induction and contraction, with minor variations. Overall, asymptomatic SARS-CoV-2 infection elicits polyfunctional antibodies neutralizing the virus and targeting infected cells. - Sera from convalescent COVID-19 patients activate the complement and kill infected cells by ADCC. - Asymptomatic and symptomatic SARS-CoV-2-infected individuals harbor polyfunctional antibodies. - Antibody levels and functions are slightly lower in asymptomatic individuals - The different antiviral activities of anti-Spike antibodies are correlated regardless of disease severity. - Functions of anti-Spike antibodies have similar kinetics of induction and contraction.

16.
Preprint in English | medRxiv | ID: ppmedrxiv-20230466

ABSTRACT

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.

17.
Preprint in English | bioRxiv | ID: ppbiorxiv-202028

ABSTRACT

Severe cases of COVID-19 are associated with extensive lung damage and the presence of infected multinucleated syncytial pneumocytes. The viral and cellular mechanisms regulating the formation of these syncytia are not well understood. Here, we show that SARS-CoV-2 infected cells express the viral Spike protein (S) at their surface and fuse with ACE2-positive neighbouring cells. Expression of S without any other viral proteins triggers syncytia formation. Type-I interferon (IFN)-induced transmembrane proteins (IFITMs), a family of restriction factors that block the entry of many viruses, inhibit S-mediated fusion, with IFITM1 being more active than IFITM2 and IFITM3. On the contrary, the TMPRSS2 serine protease, which is known to enhance infectivity of cell-free virions, processes both S and ACE2 and increases syncytia formation by accelerating the fusion process. TMPRSS2 thwarts the antiviral effect of IFITMs. Our results show that the pathological effects of SARS-CoV-2 are modulated by cellular proteins that either inhibit or facilitate syncytia formation. One Sentence SummarySyncytia produced by SARS-CoV-2 infected cells and regulation of their formation by IFITMs and TMPRSS2.

18.
Preprint in English | medRxiv | ID: ppmedrxiv-20068858

ABSTRACT

It is of paramount importance to evaluate the prevalence of both asymptomatic and symptomatic cases of SARS-CoV-2 infection and their antibody response profile. Here, we performed a pilot study to assess the levels of anti-SARS-CoV-2 antibodies in samples taken from 491 pre-epidemic individuals, 51 patients from Hopital Bichat (Paris), 209 pauci-symptomatic individuals in the French Oise region and 200 contemporary Oise blood donors. Two in-house ELISA assays, that recognize the full-length nucleoprotein (N) or trimeric Spike (S) ectodomain were implemented. We also developed two novel assays: the S-Flow assay, which is based on the recognition of S at the cell surface by flow-cytometry, and the LIPS assay that recognizes diverse antigens (including S1 or N C-terminal domain) by immunoprecipitation. Overall, the results obtained with the four assays were similar, with differences in sensitivity that can be attributed to the technique and the antigen in use. High antibody titers were associated with neutralisation activity, assessed using infectious SARS-CoV-2 or lentiviral-S pseudotypes. In hospitalized patients, seroconversion and neutralisation occurred on 5-14 days post symptom onset, confirming previous studies. Seropositivity was detected in 29% of pauci-symptomatic individuals within 15 days post-symptoms and 3 % of blood of healthy donors collected in the area of a cluster of COVID cases. Altogether, our assays allow for a broad evaluation of SARS-CoV2 seroprevalence and antibody profiling in different population subsets.

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