ABSTRACT
Background Tixagevimab and cilgavimab (AZD7442) are two monoclonal antibodies developed by AstraZeneca for the pre-exposure prophylaxis and treatment of patients infected by SARS-CoV-2. Its effectiveness and safety in patients hospitalized with COVID-19 was not known at the outset of this trial. Methods DisCoVeRy is a phase 3, adaptive, multicentre, randomized, controlled trial conducted in 63 sites in Europe. Participants were randomly assigned (1:1) to receive placebo or tixagevimab-cilgavimab in addition to standard of care. The primary outcome was the clinical status at day 15 measured by the WHO seven-point ordinal scale. Several clinical, virological, immunological and safety endpoints were also assessed. Findings Due to slow enrolment, recruitment was stopped on July 1st, 2022. The antigen positive modified intention-to-treat population (mITT) was composed of 173 participants randomized to tixagevimab-cilgavimab (n=91) or placebo (n=82), 91.9% (159/173) with supplementary oxygen, and 47.4% (82/173) previously vaccinated at inclusion. There was no significant difference in the distribution of the WHO ordinal scale at day 15 between the two groups (odds ratio (OR) 0.93, 95%CI [0.54-1.61]; p=0.81) nor in any clinical, virological or safety secondary endpoints. In the global mITT (n=226), neutralization antibody titers were significantly higher in the tixagevimab-cilgavimab group/patients compared to placebo at day 3 (Least-square mean differences (LSMD) 1.44, 95% Confidence interval (CI) [1.20-1.68]; p < 10-23) and day 8 (LSMD 0.91, 95%CI [0.64-1.18]; p < 10-8) and it was most important for patients infected with a pre-omicron variant, both at day 3 (LSMD 1.94, 95% CI [1.67-2.20], p < 10-25) and day 8 (LSMD 1.17, 95% CI [0.87-1.47], p < 10-9), with a significant interaction (p < 10-7 and p=0.01 at days 3 and 8, respectively). Interpretation There were no significant differences between tixagevimab-cilgavimab and placebo in clinical endpoints, however the trial lacked power compared to prespecified calculations. Tixagevimab-cilgavimab was well tolerated, with low rates of treatment related events.
Subject(s)
COVID-19ABSTRACT
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has shown that vaccine preparedness is critical to anticipate a fast response to emergent pathogens with high infectivity. To rapidly reach herd immunity, an affordable, easy to store and versatile vaccine platform is thus desirable. We previously designed a non-infectious adenovirus-inspired nanoparticle (ADDomer), and in the present work, we efficiently decorated this original vaccine platform with glycosylated receptor binding domain (RBD) of SARS-CoV-2. Cryo-Electron Microscopy structure revealed that up to 60 copies of this antigenic domain were bound on a single ADDomer particle with the symmetrical arrangements of a dodecahedron. Mouse immunization with the RBD decorated particles showed as early as the first immunization a significant anti-coronavirus humoral response, which was boosted after a second immunization. Neutralization assays with spike pseudo-typed-virus demonstrated the elicitation of strong neutralization titers. Remarkably, the existence of pre-existing immunity against adenoviral-derived particles enhanced the humoral response against SARS-CoV-2. This plug and play vaccine platform revisits the way of using adenovirus to combat emergent pathogens while potentially taking advantage of the adenovirus pre-immunity.
Subject(s)
Coronavirus InfectionsABSTRACT
The SARS-CoV-2 pandemic causes an ongoing global health crisis, which requires efficient and safe vaccination programs. Here, we present synthetic SARS-CoV2 S glycoprotein-coated liposomes that resemble in size and surface structure virus-like particles. Soluble S glycoprotein trimers were stabilized by formaldehyde cross-linking and coated onto lipid vesicles (S-VLP). Immunization of cynomolgus macaques with S-VLPs induced high antibody titers and TH1 CD4+ biased T cell responses. Although antibody responses were initially dominated by RBD specificity, the third immunization boosted non-RBD antibody titers. Antibodies showed potent neutralization against the vaccine strain and the Alpha variant after two immunizations and robust neutralization of Beta and Gamma strains. Challenge of animals with SARS-CoV-2 protected all vaccinated animals by sterilizing immunity. Thus, the S-VLP approach is an efficient and safe vaccine candidate based on a proven classical approach for further development and clinical testing.
ABSTRACT
SARS-CoV-2 spike proteins are responsible for the membrane fusion event, which allows the virus to enter the host cell and cause infection. This process starts with the binding of the spike extramembrane domain to the angiotensin-converting enzyme 2 (ACE2), a membrane receptor highly abundant in the lungs. In this study, the extramembrane domain of SARS-CoV-2 Spike (sSpike) was injected on model membranes, formed by supported lipid bilayers in presence and absence of the soluble part of receptor ACE2 (sACE2), and the structural features were studied at sub-nanometer level by neutron reflection. In all cases the presence of the protein produced a remarkable degradation of the lipid bilayer. Indeed, both for membranes from synthetic and natural lipids, a significant reduction of the surface coverage was observed. Quartz crystal microbalance measurements show that lipid extraction starts immediately after sSpike protein injection. All measurements indicate that the presence of proteins induces the removal of membrane lipids, both in the presence and in the absence of ACE2, suggesting that sSpike molecules strongly associate with lipids, and strip them away from the bilayer, via a non-specific interaction. A cooperative effect of sACE2 and sSpike on lipid extraction was also observed.
ABSTRACT
The efficient spread of SARS-CoV-2 resulted in a pandemic that is unique in modern history. Despite early identification of ACE2 as the receptor for viral spike protein, much remains to be understood about the molecular events behind viral dissemination. We evaluated the contribution of C-type lectin receptors (CLRS) of antigen-presenting cells, widely present in air mucosa and lung tissue. DC-SIGN, L-SIGN, Langerin and MGL bind to diverse glycans of the spike using multiple interaction areas. Using pseudovirus and cells derived from monocytes or T-lymphocytes, we demonstrate that while virus capture by the CLRs examined does not allow direct cell infection, DC/L-SIGN, among these receptors, promote virus transfer to permissive ACE2+ cells. A glycomimetic compound designed against DC-SIGN, enable inhibition of this process. Thus, we described a mechanism potentiating viral capture and spreading of infection. Early involvement of APCs opens new avenues for understanding and treating the imbalanced innate immune response observed in COVID-19 pathogenesis