Ideally, an oncolytic virus will replicate preferentially in malignant cells, have the ability to treat disseminated metastases, and ultimately be cleared by the patient. Here we present evidence that the attenuated vesicular stomatitis strains, AV1 and AV2, embody all of these traits. We uncover the mechanism by which these mutants are selectively attenuated in interferon-responsive cells while remaining highly lytic in 80% of human tumor cell lines tested. AV1 and AV2 were tested in a xenograft model of human ovarian cancer and in an immune competent mouse model of metastatic colon cancer. While highly attenuated for growth in normal mice, both AV1 and AV2 effected complete and durable cures in the majority of treated animals when delivered systemically.

Summary Interferons (IFNs) are produced in response to virus infection, and induce an anti-viral state in virtually all cell types. In addition to upregulating the transcription of genes that inhibit virus replication, type I (or −α/β) IFNs also act to orchestrate the adaptive immune response to virus infection. Recently a new family of anti-viral cytokines, the type III (or −λ) IFNs, has been identified which activate the same anti-viral pathways via a distinct receptor. Although the identical transcription factor, IFN Stimulated Gene Factor 3 (ISGF3), is activated by either IFN-α/β or IFN-λ signaling, differences in the induction and action of these two cytokine families are beginning to be appreciated. In this article we review this emerging body of literature on the differing roles these cytokines play in host defense of the mucosal surface. Although many viruses enter the body through the respiratory and gastrointestinal tracts, we have focused the discussion on influenza A virus (IAV), respiratory syncytial virus (RSV) and rotavirus (RV), three ubiquitous human pathogens that target the epithelial lining and are associated with a major disease burden.

Type I (IFN-α/β) and type III (IFN-λ) interferons (IFNs) exert shared antiviral activities through distinct receptors. However, their relative importance for antiviral protection of different organ systems against specific viruses remains to be fully explored. We used mouse strains deficient in type-specific IFN signaling, STAT1 and Rag2 to dissect distinct and overlapping contributions of type I and type III IFNs to protection against homologous murine (EW-RV strain) and heterologous (non-murine) simian (RRV strain) rotavirus infections in suckling mice. Experiments demonstrated that murine EW-RV is insensitive to the action of both types of IFNs, and that timely viral clearance depends upon adaptive immune responses. In contrast, both type I and type III IFNs can control replication of the heterologous simian RRV in the gastrointestinal (GI) tract, and they cooperate to limit extra-intestinal simian RRV replication. Surprisingly, intestinal epithelial cells were sensitive to both IFN types in neonatal mice, although their responsiveness to type I, but not type III IFNs, diminished in adult mice, revealing an unexpected age-dependent change in specific contribution of type I versus type III IFNs to antiviral defenses in the GI tract. Transcriptional analysis revealed that intestinal antiviral responses to RV are triggered through either type of IFN receptor, and are greatly diminished when receptors for both IFN types are lacking. These results also demonstrate a murine host-specific resistance to IFN-mediated antiviral effects by murine EW-RV, but the retention of host efficacy through the cooperative action by type I and type III IFNs in restricting heterologous simian RRV growth and systemic replication in suckling mice. Collectively, our findings revealed a well-orchestrated spatial and temporal tuning of innate antiviral responses in the intestinal tract where two types of IFNs through distinct patterns of their expression and distinct but overlapping sets of target cells coordinately regulate antiviral defenses against heterologous or homologous rotaviruses with substantially different effectiveness.

The type I alpha/beta interferons (IFN-␣/␤) are known to play an important role in host defense against influenza A virus infection, but we have now discovered that the recently identified type III IFNs (IFN-) constitute the major response to intranasal infection with this virus. Type III IFNs were present at much higher levels than type I IFNs in the lungs of infected mice, and the enhanced susceptibility of STAT2 ؊/؊ animals demonstrated that only signaling through the IFN-␣/␤ or IFN-pathways was sufficient to mediate protection. This finding offers a possible explanation for the similar levels of antiviral protection found in wild-type (WT) mice and in animals lacking a functional type I IFN receptor (IFNAR ؊/؊ ) but also argues that our current understanding of type III IFN induction is incomplete. While murine IFN-production is thought to depend on signaling through the type I IFN receptor, we demonstrate that intranasal influenza A virus infection leads to the robust type III IFN induction in the lungs of both WT and IFNAR ؊/؊ mice. This is consistent with previous studies showing that IFNAR-mediated protection is redundant for mucosal influenza virus infection and with data showing that the type III IFN receptor is expressed primarily by epithelial cells. However, the overlapping effects of these two cytokine families are limited by their differential receptor expression, with a requirement for IFN-␣/␤ signaling in combating systemic disease.Type I interferons (IFNs) were first recognized for their ability to interfere with influenza virus replication (31) and are now recognized as an early and powerful host defense against virus infection. In all cell types that have been investigated, virus infection results in the synthesis and secretion of the type I alpha/beta interferons (IFN-␣/␤). Once secreted, IFN-␣/␤ acts in an autocrine or paracrine manner by binding the ubiquitously expressed IFN-␣/␤ receptor (IFNAR). Receptor binding activates the Jak-STAT signaling cascade leading to transcriptional upregulation of the IFN-stimulated genes which mediate the biological effects of IFN (10,18).IFN induction by influenza A virus involves recognition of viral components by both cytoplasmic receptors and TLR7, although the precise mechanism used depends upon the infected cell type. In fibroblasts, epithelial cells, and conventional dendritic cells (cDCs), IFN-␤ gene expression is largely dependent upon virus activation of the RNA helicase retinoic acid-induced gene I (RIG-I) (26), with the subsequent phosphorylation of IFN regulatory factor 3 (IRF3) by IB kinase ε (IKKε)/TANK-binding kinase 1 (TBK1). Once IFN-␤ (as well as IFN-␣4 in mouse) has been synthesized and secreted, signaling through the Jak-STAT pathway upregulates production of IRF7, which then mediates the transcription of additional 33,45). In this way, an amplification pathway is established wherein early, IRF3-mediated production of IFN-␤ promotes the synthesis of multiple IFN-␣ subtypes.Type III IFNs were very recently discovered and are designated ...