BNT162b2 Vaccination in People Over 80 Years of Age Induces Strong Humoral Immune Responses with Cross Neutralisation of P.1 Brazilian Variant (preprint)

Background: Age is the major risk factor for mortality after SARS-CoV-2 infection and older people have received priority consideration for COVID-19 vaccination. However vaccine responses are often suboptimal in this age group and few people over the age of 80 years were included in vaccine registration trials.Methods: We determined the serological and cellular response to spike protein in 100 people aged 80-96 years at 2 weeks after second vaccination with the Pfizer BNT162b2 mRNA vaccine.Findings: Antibody responses were seen in every donor with high titres in 98%. Spike-specific cellular immune responses were detectable in only 63% and correlated with humoral response. Previous SARS-CoV-2 infection substantially increased antibody responses after one vaccine and antibody and cellular responses remained 28-fold and 3-fold higher respectively after dual vaccination. Post-vaccine sera mediated strong neutralisation of live Victoria (Wuhan-like prototype) infection and although neutralisation titres were reduced 14-fold against the P.1 variant first discovered in Brazil they remained largely effective.Interpretation: These data demonstrate that the mRNA vaccine platform delivers strong humoral immunity in people up to 96 years of age and retains broad efficacy against the P.1 Variant of Concern.Funding: This work was supported by the UK Coronavirus Immunology Consortium (UK-CIC) funded by DHSC/UKRI and the National Core Studies Immunity programme. Declaration of Interest: None to declare. Ethical Approval: The work was performed under the CIA UPH IRAS approval (REC 20\NW\0240) and conducted according to the Declaration of Helsinki and good clinical practice.

Pixatimod (PG545), a clinical-stage heparan sulfate mimetic, is a potent inhibitor of the SARS-CoV-2 virus (preprint)

A major global effort is currently ongoing to search for therapeutics and vaccines to treat or prevent infection by the SARS-CoV-2 virus. Repurposing existing entities is one attractive approach. The heparan sulfate mimetic pixatimod is a clinical-stage synthetic sulfated compound that is a potent inhibitor of the glycosidase heparanase, and has known anti-cancer, anti-inflammatory and also antiviral properties. Here we show that pixatimod binds directly to the SARS-CoV-2 spike protein S1 receptor binding domain (RBD) and alters its conformation. Notably, this site overlaps with the known ACE2 binding site in the S1 RBD. We find that pixatimod inhibits binding of recombinant S1 RBD to Vero cells which express the ACE2 receptor. Moreover, in assays with three different isolates of live SARS-CoV-2 virus we show that pixatimod effectively inhibits viral infection of Vero cells. Importantly, its potency is well within its safe therapeutic dose range. These data provide evidence that pixatimod is a potent antiviral agent against SARS-CoV-2. Together with its other known activities this provides a strong rationale for its clinical investigation as a new multimodal therapeutic for the current COVID-19 pandemic.

Neutralization of SARS-CoV-2 by Destruction of the Prefusion Spike (preprint)

There are as yet no licenced therapeutics for the COVID-19 pandemic. The causal coronavirus (SARS-CoV-2) binds host cells via a trimeric Spike whose receptor binding domain (RBD) recognizes angiotensin-converting enzyme 2 (ACE2), initiating conformational changes that drive membrane fusion. We find that monoclonal antibody CR3022 binds the RBD tightly, neutralising SARS-CoV-2 and report the crystal structure at 2.4 A of the Fab/RBD complex. Some crystals are suitable for screening for entry-blocking inhibitors. The highly conserved, structure-stabilising, CR3022 epitope is inaccessible in the prefusion Spike, suggesting that CR3022 binding would facilitate conversion to the fusion-incompetent post-fusion state. Cryo-EM analysis confirms that incubation of Spike with CR3022 Fab leads to destruction of the prefusion trimer. Presentation of this cryptic epitope in an RBD-based vaccine might advantageously focus immune responses. Binders at this epitope may be useful therapeutically, possibly in synergy with an antibody blocking receptor attachment.Funding: This work was supported by a grant from the CAMS-Oxford Institute to D.I.S. E.E.F and J.Ren are supported by the Wellcome Trust (101122/Z/13/Z), Y.Z. by Cancer Research UK (C375/A17721) and D.I.S. and E.E.F. by the UK Medical Research Council (MR/N00065X/1). J.H. is supported by a grant from the EPA Cephalosporin Fund. PPUK is funded by the Rosalind Franklin Institute EPSRC Grant no. EP/S025243/1. The National Institute for Health Research Biomedical Research Centre Funding Scheme supports G.R.S. together with the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Science (CIFMS), China (grant number: 2018-I2M-2-002), which also supports D.I.S. G.R.S. is also supported as a Wellcome Trust Senior Investigator (grant 095541/A/11/Z). T.M. is supported by Cancer Research UK grants C20724/A14414 and C20724/A26752 to Christian Siebold. This is a contribution from the UK Instruct-ERIC Centre. The Wellcome Centre for Human Genetics is supported by the Wellcome Trust (grant 090532/Z/09/Z). Virus used for the neutralisation assays was a gift from Julian Druce, Doherty Centre, Melbourne, Australia. Conflict of Interest: The authors declare no competing interests.

Neutralization of SARS-CoV-2 by destruction of the prefusion Spike (preprint)

There are as yet no licenced therapeutics for the COVID-19 pandemic. The causal coronavirus (SARS-CoV-2) binds host cells via a trimeric Spike whose receptor binding domain (RBD) recognizes angiotensin-converting enzyme 2 (ACE2), initiating conformational changes that drive membrane fusion. We find that monoclonal antibody CR3022 binds the RBD tightly, neutralising SARS-CoV-2 and report the crystal structure at 2.4 [A] of the Fab/RBD complex. Some crystals are suitable for screening for entry-blocking inhibitors. The highly conserved, structure-stabilising, CR3022 epitope is inaccessible in the prefusion Spike, suggesting that CR3022 binding would facilitate conversion to the fusion-incompetent post-fusion state. Cryo-EM analysis confirms that incubation of Spike with CR3022 Fab leads to destruction of the prefusion trimer. Presentation of this cryptic epitope in an RBD-based vaccine might advantageously focus immune responses. Binders at this epitope may be useful therapeutically, possibly in synergy with an antibody blocking receptor attachment. HighlightsO_LICR3022 neutralises SARS-CoV-2 C_LIO_LINeutralisation is by destroying the prefusion SPIKE conformation C_LIO_LIThis antibody may have therapeutic potential alone or with one blocking receptor attachment C_LI