Research ArticleCancer

Systemic cancer therapy with engineered adenovirus that evades innate immunity

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Science Translational Medicine  25 Nov 2020:
Vol. 12, Issue 571, eabc6659
DOI: 10.1126/scitranslmed.abc6659

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De-livering an oncolytic virus

Oncolytic viruses, optimized for killing tumor cells, are a promising modality in cancer immunotherapy. However, there are some challenges that these viruses must overcome, including antiviral immune responses that can affect both the efficacy and the safety of these viruses. For example, naturally occurring immunoglobulin M (IgM) antibodies bind to human species C adenovirus, resulting in trapping of the virus in the liver. To overcome this, Atasheva et al. engineered a modified version of this adenovirus, with mutations in the binding site for IgM. This modified virus was not trapped in the liver and effectively suppressed tumor growth in mouse models without safety concerns.

Abstract

Oncolytic virus therapy is a cancer treatment modality that has the potential to improve outcomes for patients with currently incurable malignancies. Although intravascular delivery of therapeutic viruses provides access to disseminated tumors, this delivery route exposes the virus to opsonizing and inactivating factors in the blood, which limit the effective therapeutic virus dose and contribute to activation of systemic toxicities. When human species C adenovirus HAdv-C5 is delivered intravenously, natural immunoglobulin M (IgM) antibodies and coagulation factor X rapidly opsonize HAdv-C5, leading to virus sequestration in tissue macrophages and promoting infection of liver cells, triggering hepatotoxicity. Here, we showed that natural IgM antibody binds to the hypervariable region 1 (HVR1) of the main HAdv-C5 capsid protein hexon. Using compound targeted mutagenesis of hexon HVR1 loop and other functional sites that mediate virus-host interactions, we engineered and obtained a high-resolution cryo–electron microscopy structure of an adenovirus vector, Ad5-3M, which resisted inactivation by blood factors, avoided sequestration in liver macrophages, and failed to trigger hepatotoxicity after intravenous delivery. Systemic delivery of Ad5-3M to mice with localized or disseminated lung cancer led to viral replication in tumor cells, suppression of tumor growth, and prolonged survival. Thus, compound targeted mutagenesis of functional sites in the virus capsid represents a generalizable approach to tailor virus interactions with the humoral and cellular arms of the immune system, enabling generation of “designer” viruses with improved therapeutic properties.

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