Interleukin 33 is a guardian of barriers and a local alarmin.

Interleukin 33 (IL-33) is a member of the IL-1 family of cytokines with a growing number of target cells and a plethora of biological functions. Although it has commonalities with other IL-1 cytokines, IL-33 exhibits some unique features. Here we review the biology of IL-33 and its receptor and develop a working model that describes two 'lives' for IL-33-one intracellular and one extracellular. Under healthy conditions, constitutively produced, intracellular IL-33 participates in maintaining barrier function by regulating gene expression as a nuclear protein. In parallel, nuclear IL-33 functions as a stored alarmin that is released when barriers are breached. Extracellular IL-33 coordinates immune defense and repair mechanisms while also initiating differentiation of helper T cells as the adaptive immune response is triggered.

Single-dose replicating poxvirus vector-based RBD vaccine drives robust humoral and T cell immune response against SARS-CoV-2 infection.

The coronavirus disease 2019 (COVID-19) pandemic requires the continued development of safe, long-lasting, and efficacious vaccines for preventive responses to major outbreaks around the world, and especially in isolated and developing countries. To combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we characterize a temperature-stable vaccine candidate (TOH-Vac1) that uses a replication-competent, attenuated vaccinia virus as a vector to express a membrane-tethered spike receptor binding domain (RBD) antigen. We evaluate the effects of dose escalation and administration routes on vaccine safety, efficacy, and immunogenicity in animal models. Our vaccine induces high levels of SARS-CoV-2 neutralizing antibodies and favorable T cell responses, while maintaining an optimal safety profile in mice and cynomolgus macaques. We demonstrate robust immune responses and protective immunity against SARS-CoV-2 variants after only a single dose. Together, these findings support further development of our novel and versatile vaccine platform as an alternative or complementary approach to current vaccines.

Nanoluciferase complementation-based bioreporter reveals the importance of N-linked glycosylation of SARS-CoV-2 S for viral entry.

The ongoing COVID-19 pandemic has highlighted the immediate need for the development of antiviral therapeutics targeting different stages of the SARS-CoV-2 life cycle. We developed a bioluminescence-based bioreporter to interrogate the interaction between the SARS-CoV-2 viral spike (S) protein and its host entry receptor, angiotensin-converting enzyme 2 (ACE2). The bioreporter assay is based on a nanoluciferase complementation reporter, composed of two subunits, large BiT and small BiT, fused to the S receptor-binding domain (RBD) of the SARS-CoV-2 S protein and ACE2 ectodomain, respectively. Using this bioreporter, we uncovered critical host and viral determinants of the interaction, including a role for glycosylation of asparagine residues within the RBD in mediating successful viral entry. We also demonstrate the importance of N-linked glycosylation to the RBD's antigenicity and immunogenicity. Our study demonstrates the versatility of our bioreporter in mapping key residues mediating viral entry as well as screening inhibitors of the ACE2-RBD interaction. Our findings point toward targeting RBD glycosylation for therapeutic and vaccine strategies against SARS-CoV-2.

Characterization of Critical Determinants of ACE2-SARS CoV-2 RBD Interaction.

Despite sequence similarity to SARS-CoV-1, SARS-CoV-2 has demonstrated greater widespread virulence and unique challenges to researchers aiming to study its pathogenicity in humans. The interaction of the viral receptor binding domain (RBD) with its main host cell receptor, angiotensin-converting enzyme 2 (ACE2), has emerged as a critical focal point for the development of anti-viral therapeutics and vaccines. In this study, we selectively identify and characterize the impact of mutating certain amino acid residues in the RBD of SARS-CoV-2 and in ACE2, by utilizing our recently developed NanoBiT technology-based biosensor as well as pseudotyped-virus infectivity assays. Specifically, we examine the mutational effects on RBD-ACE2 binding ability, efficacy of competitive inhibitors, as well as neutralizing antibody activity. We also look at the implications the mutations may have on virus transmissibility, host susceptibility, and the virus transmission path to humans. These critical determinants of virus-host interactions may provide more effective targets for ongoing vaccines, drug development, and potentially pave the way for determining the genetic variation underlying disease severity.

Oncolytic Virus Combination Therapy: Killing One Bird with Two Stones.

Over the last 60 years an eclectic collection of microbes has been tested in a variety of pre-clinical models as anti-cancer agents. At the forefront of this research are a number of virus-based platforms that have shown exciting activity in a variety of pre-clinical models and are collectively referred to as oncolytic viruses. Our true understanding of the potential and limitations of this therapeutic modality has been substantially advanced through clinical studies carried out over the last 25 years. Perhaps not surprising, as with all other cancer therapeutics, it has become clear that current oncolytic virus therapeutics on their own are unlikely to be effective in the majority of patients. The greatest therapeutic gains will therefore be made through thoughtful combination strategies built upon an understanding of cancer biology.

A T cell-targeted multi-antigen vaccine generates robust cellular and humoral immunity against SARS-CoV-2 infection.

SARS-CoV-2, the etiological agent behind the coronavirus disease 2019 (COVID-19) pandemic, has continued to mutate and create new variants with increased resistance against the WHO-approved spike-based vaccines. With a significant portion of the worldwide population still unvaccinated and with waning immunity against newly emerging variants, there is a pressing need to develop novel vaccines that provide broader and longer-lasting protection. To generate broader protective immunity against COVID-19, we developed our second-generation vaccinia virus-based COVID-19 vaccine, TOH-VAC-2, encoded with modified versions of the spike (S) and nucleocapsid (N) proteins as well as a unique poly-epitope antigen that contains immunodominant T cell epitopes from seven different SARS-CoV-2 proteins. We show that the poly-epitope antigen restimulates T cells from the PBMCs of individuals formerly infected with SARS-CoV-2. In mice, TOH-VAC-2 vaccination produces high titers of S- and N-specific antibodies and generates robust T cell immunity against S, N, and poly-epitope antigens. The immunity generated from TOH-VAC-2 is also capable of protecting mice from heterologous challenge with recombinant VSV viruses that express the same SARS-CoV-2 antigens. Altogether, these findings demonstrate the effectiveness of our versatile vaccine platform as an alternative or complementary approach to current vaccines.

Engineering Rapalog-Inducible Genetic Switches Based on Split-T7 Polymerase to Regulate Oncolytic Virus-Driven Production of Tumour-Localized IL-12 for Anti-Cancer Immunotherapy.

The approval of different cytokines as anti-neoplastic agents has been challenged by dose-limiting toxicities. Although reducing dose levels affords improved tolerability, efficacy is precluded at these suboptimal doses. Strategies combining cytokines with oncolytic viruses have proven to elicit potent survival benefits in vivo, despite promoting rapid clearance of the oncolytic virus itself. Herein, we developed an inducible expression system based on a Split-T7 RNA polymerase for oncolytic poxviruses to regulate the spatial and temporal expression of a beneficial transgene. This expression system utilizes approved anti-neoplastic rapamycin analogues for transgene induction. This treatment regimen thus offers a triple anti-tumour effect through the oncolytic virus, the induced transgene, and the pharmacologic inducer itself. More specifically, we designed our therapeutic transgene by fusing a tumour-targeting chlorotoxin (CLTX) peptide to interleukin-12 (IL-12), and demonstrated that the constructs were functional and cancer-selective. We next encoded this construct into the oncolytic vaccinia virus strain Copenhagen (VV-iIL-12mCLTX), and were able to demonstrate significantly improved survival in multiple syngeneic murine tumour models through both localized and systemic virus administration, in combination with rapalogs. In summary, our findings demonstrate that rapalog-inducible genetic switches based on Split-T7 polymerase allow for regulation of the oncolytic virus-driven production of tumour-localized IL-12 for improved anti-cancer immunotherapy.

Synthetic virology approaches to improve the safety and efficacy of oncolytic virus therapies.

The large coding potential of vaccinia virus (VV) vectors is a defining feature. However, limited regulatory switches are available to control viral replication as well as timing and dosing of transgene expression in order to facilitate safe and efficacious payload delivery. Herein, we adapt drug-controlled gene switches to enable control of virally encoded transgene expression, including systems controlled by the FDA-approved rapamycin and doxycycline. Using ribosome profiling to characterize viral promoter strength, we rationally design fusions of the operator element of different drug-inducible systems with VV promoters to produce synthetic promoters yielding robust inducible expression with undetectable baseline levels. We also generate chimeric synthetic promoters facilitating additional regulatory layers for VV-encoded synthetic transgene networks. The switches are applied to enable inducible expression of fusogenic proteins, dose-controlled delivery of toxic cytokines, and chemical regulation of VV replication. This toolbox enables the precise modulation of transgene circuitry in VV-vectored oncolytic virus design.

CRISPR-mediated rapid arming of poxvirus vectors enables facile generation of the novel immunotherapeutic STINGPOX.

Poxvirus vectors represent versatile modalities for engineering novel vaccines and cancer immunotherapies. In addition to their oncolytic capacity and immunogenic influence, they can be readily engineered to express multiple large transgenes. However, the integration of multiple payloads into poxvirus genomes by traditional recombination-based approaches can be highly inefficient, time-consuming and cumbersome. Herein, we describe a simple, cost-effective approach to rapidly generate and purify a poxvirus vector with multiple transgenes. By utilizing a simple, modular CRISPR/Cas9 assisted-recombinant vaccinia virus engineering (CARVE) system, we demonstrate generation of a recombinant vaccinia virus expressing three distinct transgenes at three different loci in less than 1 week. We apply CARVE to rapidly generate a novel immunogenic vaccinia virus vector, which expresses a bacterial diadenylate cyclase. This novel vector, STINGPOX, produces cyclic di-AMP, a STING agonist, which drives IFN signaling critical to the anti-tumor immune response. We demonstrate that STINGPOX can drive IFN signaling in primary human cancer tissue explants. Using an immunocompetent murine colon cancer model, we demonstrate that intratumoral administration of STINGPOX in combination with checkpoint inhibitor, anti-PD1, promotes survival post-tumour challenge. These data demonstrate the utility of CRISPR/Cas9 in the rapid arming of poxvirus vectors with therapeutic payloads to create novel immunotherapies.

A chimeric poxvirus with J2R (thymidine kinase) deletion shows safety and anti-tumor activity in lung cancer models.

Oncolytic viruses have shown excellent safety profiles in preclinical and clinical studies; however, in most cases therapeutic benefits have been modest. We have previously reported the generation of a chimeric poxvirus (CF33), with significantly improved oncolytic characteristics, through chimerization among different poxviruses. Here we report the sequence analysis of CF33 and oncolytic potential of a GFP-encoding CF33 virus (CF33-GFP) with a J2R deletion in lung cancer models. Replication of CF33-GFP and the resulting cytotoxicity were higher in cancer cell lines compared to a normal cell line, in vitro. After infection with virus, cancer cells expressed markers for immunogenic cell death in vitro. Furthermore, CF33-GFP was safe and exerted potent anti-tumor effects at a dose as low as 1000 plaque forming units in both virus-injected and un-injected distant tumors in A549 tumor xenograft model in mice. Likewise, in a syngeneic model of lung cancer in mice, the virus showed significant anti-tumor effect and was found to increase tumor infiltration by CD8+ T cells. Collectively, these data warrant further investigation of this novel chimeric poxvirus for its potential use as a cancer bio-therapeutic.

Implications for SARS-CoV-2 Vaccine Design: Fusion of Spike Glycoprotein Transmembrane Domain to Receptor-Binding Domain Induces Trimerization.

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presents an urgent need for an effective vaccine. Molecular characterization of SARS-CoV-2 is critical to the development of effective vaccine and therapeutic strategies. In the present study, we show that the fusion of the SARS-CoV-2 spike protein receptor-binding domain to its transmembrane domain is sufficient to mediate trimerization. Our findings may have implications for vaccine development and therapeutic drug design strategies targeting spike trimerization. As global efforts for developing SARS-CoV-2 vaccines are rapidly underway, we believe this observation is an important consideration for identifying crucial epitopes of SARS-CoV-2.

Pre-surgical neoadjuvant oncolytic virotherapy confers protection against rechallenge in a murine model of breast cancer.

The use of oncolytic viruses (OVs) for cancer treatment is emerging as a successful strategy that combines the direct, targeted killing of the cancer with the induction of a long-lasting anti-tumor immune response. Using multiple aggressive murine models of triple-negative breast cancer, we have recently demonstrated that the early administration of oncolytic Maraba virus (MRB) prior to surgical resection of the primary tumor is sufficient to minimize the metastatic burden, protect against tumor rechallenge, cure a fraction of the mice and sensitize refractory tumors to immune checkpoint blockade without the need for further treatment. Here, we apply our surgical model to other OVs: Vesicular stomatitis virus (VSV), Adenovirus (Ad), Reovirus (Reo) and Herpes simplex virus (HSV) and show that all of the tested OVs could positively change the outcome of the treated animals. The growth of the primary and secondary tumors was differently affected by the various OVs and most of the viruses conferred survival benefits in this neoadjuvant setting despite the absence of direct treatment following rechallenge. This study establishes that OV-therapy confers long-term protection when administered in the pre-operative window of opportunity.

Molecular retargeting of antibodies converts immune defense against oncolytic viruses into cancer immunotherapy.

Virus-neutralizing antibodies are a severe obstacle in oncolytic virotherapy. Here, we present a strategy to convert this unfavorable immune response into an anticancer immunotherapy via molecular retargeting. Application of a bifunctional adapter harboring a tumor-specific ligand and the adenovirus hexon domain DE1 for engaging antiadenoviral antibodies, attenuates tumor growth and prolongs survival in adenovirus-immunized mice. The therapeutic benefit achieved by tumor retargeting of antiviral antibodies is largely due to NK cell-mediated triggering of tumor-directed CD8 T-cells. We further demonstrate that antibody-retargeting (Ab-retargeting) is a feasible method to sensitize tumors to PD-1 immune checkpoint blockade. In therapeutic settings, Ab-retargeting greatly improves the outcome of intratumor application of an oncolytic adenovirus and facilitates long-term survival in treated animals when combined with PD-1 checkpoint inhibition. Tumor-directed retargeting of preexisting or virotherapy-induced antiviral antibodies therefore represents a promising strategy to fully exploit the immunotherapeutic potential of oncolytic virotherapy and checkpoint inhibition.

Targeting polysialic acid-abundant cancers using oncolytic adenoviruses with fibers fused to active bacteriophage borne endosialidase.

Genetic replacement of adenoviral fiber knobs by ligands that enable tumor specific targeting of oncolytic adenoviruses is challenging because the fiber knob contributes to virus assembly. Here, we present a novel concept by describing stable recombinant adenoviruses with tumor specific infection mode. The fiber knob was replaced by endosialidaseNF (endoNF), the tailspike protein of bacteriophage K1F. EndoNF recognizes polysialic acid, an oncofetal antigen characteristic for high malignant tumors of neuroendocrine origin. An intramolecular chaperone contained in endoNF warrants folding and compensates for the knob function in virus assembly. Obtained recombinant viruses demonstrated polysialic acid dependent infection modes, strong oncolytic capacity with polysialic acid positive cells in culture and a high potential to inhibit tumor growth in a therapeutic mouse model of subcutaneous neuroblastoma. With a single genetic manipulation we achieved ablation of the fiber knob, introduction of a tumor specific ligand, and folding control over the chimeric fiber construct.

Brief Communication; A Heterologous Oncolytic Bacteria-Virus Prime-Boost Approach for Anticancer Vaccination in Mice.

Anticancer vaccination is becoming a popular therapeutic approach for patients with cancers expressing common tumor antigens. One variation on this strategy is a heterologous virus vaccine where 2 viruses encoding the same tumor antigen are administered sequentially to prime and boost antitumor immunity. This approach is currently undergoing clinical investigation using an adenovirus (Ad) and the oncolytic virus Maraba (MRB). In this study, we show that Listeria monocytogenes can be used in place of the Ad to obtain comparable immune priming efficiency before MRB boosting. Importantly, the therapeutic benefits provided by our heterologous L. monocytogenes-MRB prime-boost strategy are superior to those conferred by the Ad-MRB combination. Our study provides proof of concept for the heterologous oncolytic bacteria-virus prime-boost approach for anticancer vaccination and merits its consideration for clinical testing.

Neoadjuvant oncolytic virotherapy before surgery sensitizes triple-negative breast cancer to immune checkpoint therapy.

Triple-negative breast cancer (TNBC) is an aggressive disease for which treatment options are limited and associated with severe toxicities. Immunotherapeutic approaches like immune checkpoint inhibitors (ICIs) are a potential strategy, but clinical trials have demonstrated limited success in this patient cohort. Clinical studies using ICIs have revealed that patients with preexisting anticancer immunity are the most responsive. Given that oncolytic viruses (OVs) induce antitumor immunity, we investigated their use as an ICI-sensitizing approach. Using a therapeutic model that mimics the course of treatment for women with newly diagnosed TNBC, we demonstrate that early OV treatment coupled with surgical resection provides long-term benefits. OV therapy sensitizes otherwise refractory TNBC to immune checkpoint blockade, preventing relapse in most of the treated animals. We suggest that OV therapy in combination with immune checkpoint blockade warrants testing as a neoadjuvant treatment option in the window of opportunity between TNBC diagnosis and surgical resection.

PolySia-Specific Retargeting of Oncolytic Viruses Triggers Tumor-Specific Immune Responses and Facilitates Therapy of Disseminated Lung Cancer.

Polysialic acid (polySia) is expressed on several malignant tumors of neuroendocrine origin, including small cell lung cancer. In this study, we investigated the therapeutic efficacy of tumor-directed T-cell responses, elicited by polySia-retargeted oncolytic adenovirus infection, in an orthotopic murine model of disseminated polySia-positive lung cancer. In several cell lines, we demonstrated highly polySia-selective retargeting of adenoviral infection using a bispecific adapter comprising the ectodomain of the coxsackievirus/adenovirus receptor and a polySia-recognizing single-chain antibody domain. PolySia-dependent systemic infection in vivo facilitated effective uptake of viruses in subcutaneous polySia-expressing human tumors, whereas hepatic viral load and hepatotoxicity were significantly reduced. The impact and nature of antitumoral immune responses triggered by systemic delivery of polySia-retargeted oncolytic adenoviruses were investigated in an orthotopic model of disseminated lung cancer. Interestingly, improved transduction by polySia-retargeted oncolytic adenoviruses led to CD45-positive cell infiltrates in close association with large lytic areas. Consistently, enhanced tumor regression and prolonged survival was only observed in immunocompetent mice, but not in T-cell-deficient mice. To investigate whether improved systemic infection by polySia retargeting would elicit a tumor-specific T-cell response, we screened the used lung cancer cells for mutated oncogenes by complete exon sequencing. In agreement with our other results, only retargeted oncolysis was able to induce a significant response specific for the tumor-associated neoepitope Gsta2-Y9H. In conclusion, we demonstrated that effective retargeting of oncolytic adenovirus against polySia-expressing tumors elicits an effective tumor-directed T-cell response after systemic virus delivery and facilitates therapy of disseminated lung cancer.