An alternative approach is to preclude IFN production by disarming or degrading the transcription factors involved in the expression of IFN, such as interferon regulatory factor 3 (IRF3)/IRF7, nuclear factor-κB (NF-κB), or ATF-2/c-jun, or by inducing a general block on host cell transcription. Viruses also oppose IFN signalling, both by disturbing the type I IFN receptor and by impeding JAK/STAT signal transduction upon IFN receptor engagement.
In addition, the global expression of IFN-stimulated genes (ISGs) can be obstructed via interference with epigenetic signalling, and specific ISGs can also be selectively targeted for inhibition. Finally, some viruses disrupt IFN responses by co-opting negative regulatory systems, whereas others use antiviral mechanisms drug discovery to their own advantage. Here, we review recent developments in this field. Despite almost constant exposure to pathogens, mammals are only rarely infected to the point where disease Trichostatin A purchase becomes evident. The first line of defence consists of the interferon (IFN) family of soluble cytokines. The IFNs have anti-cancer, anti-proliferative, anti-viral and immunomodulatory functions through the expression of more than 300 IFN-stimulated genes (ISGs). There are three classes of IFNs which are produced by different cell types, bind unique receptors and have distinctive biological actions. Here,
we focus on the type I IFNs, which are produced 4��8C by most cell types and have potent, inherent antiviral activity. The type I IFN response is bimodal: first, detection of an invading virus leads to IFN production and secretion and second, IFN acts in an autocrine and paracrine manner to induce ISGs, the products of which work collectively to disrupt viral replication and
spread. To generate a productive infection, viruses must overcome antiviral responses, and accordingly, every aspect of these defences is targeted for inhibition. Here, we describe the IFN response and viral immune evasion strategies. As this topic has been extensively reviewed previously, we will focus on the most recent advances. In the first step of the biphasic type I IFN response, virus is detected through the recognition of pathogen-associated molecular patterns (PAMPs), highly conserved structural features found in broad classes of pathogens. PAMPs are sensed by pattern recognition receptors (PRRs), including the toll-like receptors (TLRs). The TLRs recognize viral components including glycoproteins and nucleic acids such as dsRNA or CpG DNA. Via their cytoplasmic Toll/interleukin-1 receptor (TIR) domains, TLRs recruit TIR-containing adaptors such as MyD88, TIR-domain-containing adapter-inducing IFN-β (TRIF), Mal and TRIF-related adaptor molecule (TRAM), leading to the activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3) (Fig. 1). Recently, several viruses have been found to disrupt TLR signalling by interfering with the adaptor molecule TRIF.