Development of a targeted, adenoviral gene therapy platform for optimized delivery of SARS-CoV-2 interventions to the lung

1. Project summary. A novel human coronavirus, SARS-CoV-2, originating in Wuhan, China, has caused a worldwide pandemic of COVID-19 for which there is no existing vaccine or cure1. As a response, researchers are rapidly developing new strategies to elicit immunity against the virus and/or reduce infection rates before COVID-19 overburdens global healthcare systems. According to the World Health Organization (WHO) DRAFT landscape of COVID-19 candidate vaccines published on 13 March 2020, adenoviral-based vectors have been identified from several developers as candidate delivery platforms for COVID-19 vaccines2 and as of mid-May 2020, an (untargeted) Ad5 vector and an (untargeted) chimpanzee adenoviral vector are currently in clinical vaccine trials. Our research group has a core expertise in protein engineering and has developed a robust and highly versatile platform for generating engineered non-replicative, high-capacity 'gutless' adenoviruses (AdVs) that can be (1) retargeted to transduce specific cell subtypes using interchangeable adapters that target tropism to cell-surface biomarkers4,5, (2) used to deliver large payload(s) of up to 36 kb, such as secreted neutralizing antibodies (nAbs) and/or complex vaccine cocktails, (3) generated at high titers with extremely high purities (<0.00001% contamination of helper virus), unprecedented in the scientific literature, and (4) coated with an engineered 'shield' that reduced immune-based clearance due to pre-existing immunity to the vector6. Projects developing this system for applications in cancer therapy have been our primary focus to date; however, we believe the current global health crisis warrants the development of our technology for applications to combat and prevent COVID-19 and other pandemic diseases that synergize with other approaches being developed in the international scientific community. In this proposal, we aim to adapt our delivery platform for two applications to combat COVID-19: First, we aim to target adenoviral tropism to key antigen-presenting cell (APC) types in the human lung using our bispecific adapter system. We propose that retargeted viruses encoding SARS-CoV-2 vaccines could then be administered intranasally or intrapulmonary as aerosols and thus more efficiently target key cell types involved in developing robust mucosal immunity and memory responses against SARS-CoV-2 infection. Second, we aim to use the Ad delivery platform to infect airway epithelia with genes encoding secreted, neutralizing antibodies against the SARS-CoV-2 spike protein as a way to prevent infection and/or gain time, and thus reduce viral spread and transmission. Hypotheses. We hypothesize that bispecific adapters can be used to mediate specific infection of airway APCs by SARS-CoV-2 vaccine-encoding adenoviral vectors, enhancing mucosal immunity and eliciting higher protection, and (2) the adenoviral delivery platform can be used for airway-localized production of SARS-CoV-2 neutralizing antibodies to prevent or reduce viral spread at the site of infection. We will pursue aspects of both strategies on the onset of the project, focusing in on the promising approach as the project develops.Specific Aim 1. Development of adenoviral retargeting adaptors for biomarkers present on airway epithelial cells (AECs) and antigen presenting cell (APC) subtypes. From our existing pool of retargeting adapters, we have identified several in our portfolio that can already be applied in the mucosal SARS-CoV-2 applications described here (i.e. retargeting to HER3, FAP, CSFR1). As an additional aim, we will generate new adapters to target discrete populations of lung dendritic cells (DCs) and macrophages (Mf) for vaccine delivery applications (e.g. CD11c, CD206 and DEC-205).Specific Aim 2. Generation of high-capacity 'gutless' adenoviruses encoding SARS-CoV-2 vaccines and/or secreted neutralizing antibodies to block SARS-CoV-2 entry and propagation. We will generate retargeted and shielded 'gutless' adenoviruses to deliver two COVID-19 interventions: (1) we will encode a vaccine based on the SARS-CoV-2 spike protein to elicit an antiviral immune response and prevent viral entry, and (2) we will encode a secreted neutralizing antibody against SARS-CoV-2 that will be produced locally in the lung epithelia. Additionally, as more neutralization and vaccine approaches are described by, we will adapt our system to robustly deliver interventions developed by others to the optimal cell types and tissues in the lung. We are in contact with experts with whom we are planning to collaborate on developing our technology, including (1) Mario Roederer at the NIH National Institute of Allergy and Infectious Diseases who is an expert in vaccine immunology and respiratory mucosa immunization8,9, and (2) Michael Schindler at the University of Tübingen, who is a molecular virologist specializing in novel immunotherapeutic approaches against viral pathogens and equipped to test our approach in an S3 lab approved for experiments with live SARS-CoV-2.Specific Aim 3. Optimizing intranasal, aerosol-based delivery of retargeted adenoviruses. Our previous work with our delivery platform has focused on developing intravenous, sub-cutaneous and intra-tissue administration of retargeted viral particles. In collaboration with James Friend (UCSD), we will establish aerosol-based systems to delivery viral particles to the alveolar surface. As adenovirus exists naturally as a respiratory virus, it is well-suited for this route of administration10.