An mRNA-based broad-spectrum antiviral inspired by ISG15 deficiency protects against viral infections in vitro and in vivo.

Type I interferons (IFN-Is) are cytokines with potent antiviral and inflammatory capacities. IFN-I signaling drives the expression of thousands of IFN-I-stimulated genes (ISGs), whose aggregate function results in the control of viral infections. A few of these ISGs are tasked with negatively regulating the IFN-I response to prevent overt inflammation. ISG15 is a negative regulator whose absence leads to persistent, low-grade elevation of ISG expression and concurrent, often self-resolving, mild autoinflammation. The limited breadth and low-grade persistence of ISGs expressed in ISG15 deficiency are sufficient to confer broad-spectrum antiviral resistance. Inspired by the antiviral state of humans with ISG15 deficiency, we identified a nominal collection of 10 ISGs that recapitulated the broad antiviral potential of the IFN-I system, which typically induces the expression of thousands of ISGs. The expression of this 10-ISG collection in an IFN-I-nonresponsive cell line increased cellular resistance to Zika virus, vesicular stomatitis virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A lipid nanoparticle-encapsulated messenger RNA (mRNA) formulation of this 10-ISG collection reduced influenza A virus plaque size in samples collected from infected mice when given prophylactically. Moreover, when used collectively and delivered prophylactically, the 10-ISG collection was able to protect hamsters against a lethal SARS-CoV-2 challenge, in contrast with the lack of efficacy when mRNAs were delivered individually. These findings suggest that these 10 ISGs have potential as a broad-spectrum antiviral prophylactic.