TNF and viral infectious disease: Host recognition of viral infection through these Pattern recognition receptors (PRRs) normally initiate signaling pathways that can lead to the activation of transcription factors NF-kB and the IRF-3 and IRF-7 [3], which often culminate in the induction of an array of antiviral cytokines, including type I IFN [4-6] and proinflammatory cytokines such as TNF, IL-6 and IL-8 [7,8].