Activation and regulation of interferon-β in immune responses

Endobiont viruses sensed by the human host - beyond conventional antiparasitic therapy

Wide-spread protozoan parasites carry endosymbiotic dsRNA viruses with uncharted implications to the human host. Among them, Trichomonas vaginalis, a parasite adapted to the human genitourinary tract, infects globally ∼250 million each year rendering them more susceptible to devastating pregnancy complications (especially preterm birth), HIV infection and HPV-related cancer. While first-line antibiotic treatment (metronidazole) commonly kills the protozoan pathogen, it fails to improve reproductive outcome. We show that endosymbiotic Trichomonasvirus, highly prevalent in T. vaginalis clinical isolates, is sensed by the human epithelial cells via Toll-like receptor 3, triggering Interferon Regulating Factor -3, interferon type I and proinflammatory cascades previously implicated in preterm birth and HIV-1 susceptibility. Metronidazole treatment amplified these proinflammatory responses. Thus, a new paradigm targeting the protozoan viruses along with the protozoan host may prevent trichomoniasis-attributable inflammatory sequelae.

The Akt1 isoform is required for optimal IFN-β transcription through direct phosphorylation of β-catenin

IFN-β is a critical antiviral cytokine that is capable of modulating the systemic immune response. The transcriptional induction of IFN-β is a highly regulated process, involving the activation of pattern recognition receptors and their downstream signaling pathways. The Akt family of serine/threonine kinases includes three isoforms. The specific role for the individual Akt isoforms in pattern recognition and signaling remains unclear. In this article, we report that the TLR3-mediated expression of IFN-β is blunted in cells that lack Akt1. The expression of IFN-β-inducible genes such as CCL5 and CXCL10 was also reduced in Akt1-deficient cells; the induction of TNF-α and CXCL2, whose expression does not rely on IFN-β, was not reduced in the absence of Akt1. Macrophages from Akt1(-/-) mice displayed deficient clearance of HSV-1 along with reduced IFN-β expression. Our results demonstrate that Akt1 signals through β-catenin by phosphorylation on Ser(552), a site that differs from the glycogen synthase kinase 3 β phosphorylation site. Stimulation of a chemically activated version of Akt1, in the absence of other TLR3-dependent signaling, was sufficient for accumulation and phosphorylation of β-catenin at Ser(552). Taken together, these results demonstrate that the Akt1 isoform is required for β-catenin-mediated promotion of IFN-β transcription downstream of TLR3 activation.