Release of infectious virus and cytokines in nasopharyngeal swabs from individuals infected with non-B.1.1.7 or B.1.1.7 SARS-CoV-2 variants. (preprint)

The mechanisms that allowed for the SARS-CoV-2 B.1.1.7 variant to rapidly outcompete pre-existing variants in many countries remain poorly characterized. Here, we analyzed viral release, anti-SARS-CoV-2 antibodies and cytokine production in a retrospective series of 427 RTqPCR+ nasopharyngeal swabs collected in COVID-19 patients harbouring either non-B.1.1.7 or B.1.17 variants. We utilized a novel rapid assay, based on S-Fuse-T reporter cells, to quantify infectious SARS-CoV-2. With both non-B.1.1.7 and B.1.1.7 variants, viral titers were highly variable, ranging from 0 to >106 infectious units, and correlated with viral RNA levels. Lateral flow antigenic rapid diagnostic tests (RDTs) were positive in 96% of the samples harbouring infectious virus. About 67 % of individuals carried detectable infectious virus within the first two days after onset of symptoms. This proportion decreased overtime, and viable virus was detected up to 14 days. Samples containing anti-SARS-CoV-2 IgG or IgA did not generally harbour infectious virus. The proportion of individuals displaying viable virus or being RDT-positive was not higher with B.1.1.7 than with non- B.1.1.7 variants. Ct values were slightly but not significantly lower with B.1.1.7. The variant was characterized by a fast decrease of infectivity overtime and a marked release of 17 cytokines (including IFN-b, IP-10, IL-10 and TRAIL). Our results highlight differences between non-B.1.1.7 and B.1.1.7 variants. B.1.1.7 is associated with modified viral decays and cytokine profiles at the nasopharyngeal mucosae during symptomatic infection.

A Monocyte/Dendritic Cell Molecular Signature of SARS-CoV-2 Related Multisystem Inflammatory Syndrome in Children (MIS-C) with Severe Myocarditis (preprint)

SARS-CoV-2 infection in children is generally milder than in adults, yet a proportion of cases result in hyperinflammatory conditions often including myocarditis. To better understand these cases, we applied a multi-parametric approach to the study of blood cells of 56 children hospitalized with suspicion of SARS-CoV-2 infection. The most severe forms of MIS-C (multisystem inflammatory syndrome in children related to SARS-CoV-2), that resulted in myocarditis, were characterized by elevated levels of pro-angiogenesis cytokines and several chemokines. Single-cell transcriptomic analyses identified a unique monocyte/dendritic cell gene signature that correlated with the occurrence of severe myocarditis, characterized by sustained NF-κ B activity, TNF-α signaling, associated with decreased gene expression of NF-κ B inhibitors. We also found a weak response to type-I and type-II interferons, hyperinflammation and response to oxidative stress related to increased HIF-1α and VEGF signaling. These results provide potential for a better understanding of disease pathophysiology.Funding: The study was supported by the Institut National de la Santé et de la Recherche Médicale (INSERM), by the “URGENCE COVID-19” fundraising campaign of Institut Pasteur, by the Atip-Avenir, Emergence ville de Paris program and fond de dotation Janssen Horizon and by government grants managed by the Agence National de la Recherche as part of the “Investment for the Future” program (Institut Hospitalo-Universitaire Imagine, grant ANR-10-IAHU-01, Recherche Hospitalo-Universitaire, grant ANR-18-RHUS-0010, Laboratoire d’Excellence ‘‘Milieu Intérieur”, grant ANR-10-LABX-69-01), the Centre de Référence Déficits Immunitaires Héréditaires (CEREDIH), the Agence National de la Recherche (ANR-flash Covid19 “AIROCovid” to FRL and “CoVarImm” to DD and JDS), and by the FASTFoundation (French Friends of Sheba Tel Hashomer Hospital). The LabTech Single-Cell@Imagine is supported by the Paris Region and the “Investissements d’avenir” program through the 2019 ATF funding – Sésame Filières PIA (Grant N°3877871).CdC is the recipient of a CIFRE-PhD (Sanofi). L.B. was a recipient of an Imagine institute PhD international program supported by the Fondation Bettencourt Schueller. L.B. was also supported by the EUR G.E.N.E. (reference #ANR-17-EURE-0013) and is part of the Université de Paris IdEx #ANR-18-IDEX-0001 funded by the French Government through its“Investments for the Future” program. S.M. was a recipient of an INSERM and Institut Imagine post-doctorat program supported by the Fondation pour la Recherche Médicale (FRMN°SPF20170938825). NS was a recipient of the Pasteur-Roux-Cantarini Fellowship. VGP obtained an Imagine international PhD fellowship program supported by the Fondation Bettencourt Schueller. BPP is the recipient of an ANRS post-doctoral fellowship.Conflict of Interest: DD, FRL, JT and MMM are listed as inventors on a patent application related to this technology (European Patent Application no. EP21305197, entitled “Methods of predicting multisystem inflammatory syndrome (MIS-C) with severe myocarditis in subjects suffering from a SARS-CoV-2 infection”).Ethical Approval: The study was approved by the Ethics Committee (Comité de Protection des Personnes Ouest IV, n° DC-2017-2987).

Distinct systemic and mucosal immune responses to SARS-CoV-2 (preprint)

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.

A measles-vectored COVID-19 vaccine induces long-term immunity and protection from SARS-CoV-2 challenge in mice (preprint)

In light of the expanding SARS-CoV-2 pandemic, developing efficient vaccines that can provide sufficient coverage for the world population is a global health priority. The measles virus (MV)-vectored vaccine is an attractive candidate given the measles vaccine's extensive safety history, well-established manufacturing process, and induction of strong, long-lasting immunity. We developed an MV-based SARS-CoV-2 vaccine using either the full-length spike (S) or S2 subunit as the antigen. While the S2 antigen failed to induce neutralizing antibodies, the prefusion-stabilized, full-length S (MV-ATU2-SF-2P-dER) construct proved to be an attractive vaccine candidate, eliciting strong Th1-dominant T-cell and neutralizing antibody responses against the S antigen while minimizing reactivity to the vector itself. Neutralizing antibody titers remained high three months after homologous prime-boost immunization, and infectious virus was undetectable in all animals after challenge with a mouse-adapted SARS-CoV-2 virus.