Absence of central tolerance in Aire-deficient mice synergizes with immune-checkpoint inhibition to enhance antitumor responses.

The endogenous anti-tumor responses are limited in part by the absence of tumor-reactive T cells, an inevitable consequence of thymic central tolerance mechanisms ensuring prevention of autoimmunity. Here we show that tumor rejection induced by immune checkpoint blockade is significantly enhanced in Aire-deficient mice, the epitome of central tolerance breakdown. The observed synergy in tumor rejection extended to different tumor models, was accompanied by increased numbers of activated T cells expressing high levels of Gzma, Gzmb, Perforin, Cxcr3, and increased intratumoural levels of Cxcl9 and Cxcl10 compared to wild-type mice.

Viral Fitness Landscapes in Diverse Host Species Reveal Multiple Evolutionary Lines for the NS1 Gene of Influenza A Viruses.

Influenza A viruses (IAVs) have a remarkable tropism in their ability to circulate in both mammalian and avian species. The IAV NS1 protein is a multifunctional virulence factor that inhibits the type I interferon host response through a myriad of mechanisms. How NS1 has evolved to enable this remarkable property across species and its specific impact in the overall replication, pathogenicity, and host preference remain unknown.

Genome-wide CRISPR/Cas9 Screen Identifies Host Factors Essential for Influenza Virus Replication.

The emergence of influenza A viruses (IAVs) from zoonotic reservoirs poses a great threat to human health. As seasonal vaccines are ineffective against zoonotic strains, and newly transmitted viruses can quickly acquire drug resistance, there remains a need for host-directed therapeutics against IAVs. Here, we performed a genome-scale CRISPR/Cas9 knockout screen in human lung epithelial cells with a human isolate of an avian H5N1 strain.

DAI Senses Influenza A Virus Genomic RNA and Activates RIPK3-Dependent Cell Death.

Influenza A virus (IAV) is an RNA virus that is cytotoxic to most cell types in which it replicates. IAV activates the host kinase RIPK3, which induces cell death via parallel pathways of necroptosis, driven by the pseudokinase MLKL, and apoptosis, dependent on the adaptor proteins RIPK1 and FADD. How IAV activates RIPK3 remains unknown.

Engineered Mammalian RNAi Can Elicit Antiviral Protection that Negates the Requirement for the Interferon Response.

Although the intrinsic antiviral cell defenses of many kingdoms utilize pathogen-specific small RNAs, the antiviral response of chordates is primarily protein based and not uniquely tailored to the incoming microbe. In an effort to explain this evolutionary bifurcation, we determined whether antiviral RNAi was sufficient to replace the protein-based type I interferon (IFN-I) system of mammals. To this end, we recreated an RNAi-like response in mammals and determined its effectiveness to combat influenza A virus in vivo in the presence and absence of the canonical IFN-I system.

In Vivo RNAi Screening Identifies MDA5 as a Significant Contributor to the Cellular Defense against Influenza A Virus.

Responding to an influenza A virus (IAV) infection demands an effective intrinsic cellular defense strategy to slow replication. To identify contributing host factors to this defense, we exploited the host microRNA pathway to perform an in vivo RNAi screen. To this end, IAV, lacking a functional NS1 antagonist, was engineered to encode individual siRNAs against antiviral host genes in an effort to rescue attenuation.

An in vivo RNAi screening approach to identify host determinants of virus replication.

RNA interference (RNAi) has been extensively used to identify host factors affecting virus infection but requires exogenous delivery of short interfering RNAs (siRNAs), thus limiting the technique to nonphysiological infection models and a single defined cell type. We report an alternative screening approach using siRNA delivery via infection with a replication-competent RNA virus. In this system, natural selection, defined by siRNA production, permits the identification of host restriction factors through virus enrichment during a physiological infection.