Cardiovascular symptoms of PASC are associated with trace-level cytokines that affect the function of human pluripotent stem cell derived cardiomyocytes (preprint)

Globally, over 65 million individuals are estimated to suffer from post-acute sequelae of COVID-19 (PASC). A large number of individuals living with PASC experience cardiovascular symptoms (i.e. chest pain and heart palpitations) (PASC-CVS). The role of chronic inflammation in these symptoms, in particular in individuals with symptoms persisting for >1 year after SARS-CoV-2 infection, remains to be clearly defined. In this cross-sectional study, blood samples were obtained from three different sites in Australia from individuals with i) a resolved SARS-CoV-2 infection (and no persistent symptoms i.e. Recovered), ii) individuals with prolonged PASC-CVS and iii) SARS-CoV-2 negative individuals. Individuals with PASC-CVS, relative to Recovered individuals, had a blood transcriptomic signature associated with inflammation. This was accompanied by elevated levels of pro-inflammatory cytokines (IL-12, IL-1beta;, MCP-1 and IL-6) at approximately 18 months post-infection. These cytokines were present in trace amounts, such that they could only be detected with the use of novel nanotechnology. Importantly, these trace-level cytokines had a direct effect on the functionality of pluripotent stem cell derived cardiomyocytes in vitro. This effect was not observed in the presence of dexamethasone. Plasma proteomics demonstrated further differences between PASC-CVS and Recovered patients at approximately 18 months post-infection including enrichment of complement and coagulation associated proteins in those with prolonged cardiovascular symptoms. Together, these data provide a new insight into the role of chronic inflammation in PASC-CVS and present nanotechnology as a possible novel diagnostic approach for the condition.

Virus-like particle displaying SARS-CoV-2 receptor binding domain elicits neutralizing antibodies and is protective in a challenge model (preprint)

While the effort to vaccinate people against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has largely been successful, particularly in the developed world, the rise of new variants as well as waning immunity illustrate the need for a new generation of vaccines that provide broader and/or more durable protection against infection and severe disease. Here we describe the generation and characterization of IVX-411, a computationally designed, two-component virus-like particle (VLP) displaying the ancestral SARS-CoV-2 receptor binding domain (RBD) on its surface. Immunization of mice with IVX-411 generates neutralizing antibodies against the ancestral strain as well as three variants of concern. Neutralizing antibody titers elicited by IVX-411 are durable and significantly higher than those elicited by immunization with soluble RBD and spike antigens. Furthermore, immunization with IVX-411 is shown to be protective in a Syrian Golden hamster challenge model using two different strains of SARS-CoV-2. Overall, these studies demonstrate that IVX-411 is highly immunogenic and capable of eliciting broad, protective immunity.

Nanoparticle display of prefusion coronavirus spike elicits S1-focused cross-reactive protection across divergent subgroups (preprint)

Multivalent antigen display is a fast-growing area of interest towards broadly protective vaccines. Current nanoparticle-based vaccine candidates demonstrate the ability to confer antibody-mediated immunity against divergent strains of notably mutable viruses. In coronaviruses, this work is predominantly aimed at targeting conserved epitopes of the receptor-binding domain. However, targeting other conserved non-RBD epitopes could further limit the potential for antigenic escape. To further explore new potential targets, we engineered protein nanoparticles displaying CoV_S-2P trimers derived from MERS-CoV, SARS-CoV-1, SARS-CoV-2, hCoV-HKU1, and hCoV-OC43 and assessed their immunogenicity in mice. Monotypic SARS-1_S-2P nanoparticles elicited cross-neutralizing antibodies against MERS_S and protected against MERS-CoV challenge. MERS and SARS-I53_dn5 nanoparticles elicited S1-focused antibodies, revealing a conserved site on the NTD. Moreover, mosaic nanoparticles co-displaying distinct CoV_S-2P trimers elicited antibody responses to distant cross-group antigens while protecting against MERS challenge despite diminished valency of MERS_S-2P. Our findings will inform further efforts towards the development of pan-coronavirus vaccines.

Stabilization of the SARS-CoV-2 Spike receptor-binding domain using deep mutational scanning and structure-based design (preprint)

The unprecedented global demand for SARS-CoV-2 vaccines has demonstrated the need for highly effective vaccine candidates that are thermostable and amenable to large-scale manufacturing. Nanoparticle immunogens presenting the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein (S) in repetitive arrays are being advanced as second-generation vaccine candidates, as they feature robust manufacturing characteristics and have shown promising immunogenicity in preclinical models. Here, we used previously reported deep mutational scanning (DMS) data to guide the design of stabilized variants of the RBD. The selected mutations fill a cavity in the RBD that has been identified as a linoleic acid binding pocket. Screening of several designs led to the selection of two lead candidates that expressed at higher yields than the wild-type RBD. These stabilized RBDs possess enhanced thermal stability and resistance to aggregation, particularly when incorporated into an icosahedral nanoparticle immunogen that maintained its integrity and antigenicity for 28 days at 35-40{degrees}C, while corresponding immunogens displaying the wild-type RBD experienced aggregation and loss of antigenicity. The stabilized immunogens preserved the potent immunogenicity of the original nanoparticle immunogen, which is currently being evaluated in a Phase I/II clinical trial. Our findings may improve the scalability and stability of RBD-based coronavirus vaccines in any format and more generally highlight the utility of comprehensive DMS data in guiding vaccine design.