Correlation between pseudotyped virus and authentic virus neutralisation assays, a systematic review and meta-analysis of the literature

Double-blinded, randomised, placebo-controlled trial of convalescent plasma for COVID-19: analyses by neutralising antibodies homologous to recipients' variants

INTRODUCTION

Convalescent plasma (CP) emerged as potential treatment for COVID-19 early in the pandemic. While efficacy in hospitalised patients has been lacklustre, CP may be beneficial at the first stages of disease. Despite multiple new variants emerging, no trials have involved analyses on variant-specific antibody titres of CP.

METHODS

We recruited hospitalised COVID-19 patients within 10 days of symptom onset and, employing a double-blinded approach, randomised them to receive 200 ml convalescent plasma with high (HCP) or low (LCP) neutralising antibody (NAb) titre against the ancestral strain (Wuhan-like variant) or placebo in 1:1:1 ratio. Primary endpoints comprised intubation, corticosteroids for symptom aggravation, and safety assessed as serious adverse events. For a preplanned ad hoc analysis, the patients were regrouped by infused CP's NAb titers to variants infecting the recipients i.e. by titres of homologous HCP (hHCP) or LCP (hLCP).

RESULTS

Of the 57 patients, 18 received HCP, 19 LCP and 20 placebo, all groups smaller than planned. No significant differences were found for primary endpoints. In ad hoc analysis, hHCPrecipients needed significantly less respiratory support, and appeared to be given corticosteroids less frequently (1/14; 7.1%) than those receiving hLCP (9/23; 39.1%) or placebo (8/20; 40%), (p = 0.077).

DISCUSSION

Our double-blinded, placebo-controlled CP therapy trial remained underpowered and does not allow any firm conclusions for early-stage hospitalised COVID-19 patients. Interestingly, however, regrouping by homologous - recipients' variant-specific - CP titres suggested benefits for hHCP. We encourage similar re-analysis of ongoing/previous larger CP studies.

TRIAL REGISTRATION

ClinTrials.gov identifier: NCT0473040.

Safety and immunogenicity of heterologous boosting with a bivalent SARS-CoV-2 mRNA vaccine (XBB.1.5/BQ.1) in Chinese participants aged 18 years or more: A randomised, double-blinded, active-controlled phase 1 trial

Continuous emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants urges the development of new vaccines. We assessed the safety and immunogenicity of SYS6006.32, a bivalent vaccine (XBB.1.5/BQ.1), in healthy adults who had received SARS-CoV-2 primary vaccination. In a randomised, double-blinded, active-controlled trial, 200 participants were randomised to receive one dose of SYS6006.32 (N = 100) or a prototype-based, monovalent control vaccine SYS6006 (N = 100). Adverse events (AEs) were collected through the study. Immunogenicity was assessed by live-virus neutralising antibody (Nab) and pseudovirus Nab. 61 (61.0 %) and 60 (60.0 %) participants reported AE in the SYS6006.32 and SYS6006 groups, respectively. Most AEs were grade 1 or 2. Pain and fever were the most common injection-site and systemic AEs, respectively. No serious AEs were observed. SYS6006.32 heterologous boosting induced robust Nab responses against BA.5, XBB.1.5 and EG.5 with live-virus Nab geometric mean titres (GMTs) increased by 17.1-, 34.0-, and 48.0-fold, and pseudovirus Nab GMTs increased by 12.2-, 32.0-, and 35.1-fold, respectively, 14 days after vaccination. SYS6006.32 demonstrated a superior immunogenicity to SYS6006. SYS6006.32 also induced robust pseudovirus Nab responses against XBB.1.16, XBB.2.3, and BA.2.86, with GMTs 3- to 6-fold higher than those induced by SYS6006. In conclusion, SYS6006.32 showed good safety profile and superior immunogenicity to the monovalent vaccine SYS6006.

A pan-influenza monoclonal antibody neutralizes H5 strains and prophylactically protects through intranasal administration

Avian A(H5N1) influenza virus poses an elevated zoonotic threat to humans, and no pharmacological products are currently registered for fast-acting pre-exposure protection in case of spillover leading to a pandemic. Here, we show that an epitope on the stem domain of H5 hemagglutinin is highly conserved and that the human monoclonal antibody CR9114, targeting that epitope, potently neutralizes all pseudotyped H5 viruses tested, even in the rare case of substitutions in its epitope. Further, intranasal administration of CR9114 fully protects mice against A(H5N1) infection at low dosages, irrespective of pre-existing immunity conferred by the quadrivalent seasonal influenza vaccine. These data provide a proof-of-concept for broad, pre-exposure protection against a potential future pandemic using the intranasal administration route. Studies in humans should assess if autonomous administration of a broadly-neutralizing monoclonal antibody is safe and effective and can thus contribute to pandemic preparedness.

Pseudoviruses, a safer toolbox for vaccine development against enveloped viruses

INTRODUCTION

Pseudoviruses are recombinant, replication-incompetent, viral particles designed to mimic the surface characteristics of native enveloped viruses. They are a safer, and cost-effective research alternative to live viruses. With the potential emergence of the next major infectious disease, more vaccine scientists must become familiar with the pseudovirus platform as a vaccine development tool to mitigate future outbreaks.

AREAS COVERED

This review aims at vaccine developers to provide a basic understanding of pseudoviruses, list their production methods, and discuss their utility to assess vaccine efficacy against enveloped viral pathogens. We further illustrate their usefulness as wet-lab simulators for emerging mutant variants, and new viruses to help prepare for current and future viral outbreaks, minimizing the need for gain-of-function experiments with highly infectious or lethal enveloped viruses.

EXPERT OPINION

With this platform, researchers can better understand the role of virus-receptor interactions and entry in infections, prepare for dangerous mutations, and develop effective vaccines.

Full-spike deep mutational scanning helps predict the evolutionary success of SARS-CoV-2 clades

SARS-CoV-2 variants acquire mutations in spike that promote immune evasion and impact other properties that contribute to viral fitness such as ACE2 receptor binding and cell entry. Knowledge of how mutations affect these spike phenotypes can provide insight into the current and potential future evolution of the virus. Here we use pseudovirus deep mutational scanning to measure how >9,000 mutations across the full XBB.1.5 and BA.2 spikes affect ACE2 binding, cell entry, or escape from human sera. We find that mutations outside the receptor-binding domain (RBD) have meaningfully impacted ACE2 binding during SARS-CoV-2 evolution. We also measure how mutations to the XBB.1.5 spike affect neutralization by serum from individuals who recently had SARS-CoV-2 infections. The strongest serum escape mutations are in the RBD at sites 357, 420, 440, 456, and 473-however, the antigenic impacts of these mutations vary across individuals. We also identify strong escape mutations outside the RBD; however many of them decrease ACE2 binding, suggesting they act by modulating RBD conformation. Notably, the growth rates of human SARS-CoV-2 clades can be explained in substantial part by the measured effects of mutations on spike phenotypes, suggesting our data could enable better prediction of viral evolution.