IKKepsilon is an IKK (inhibitor of nuclear factor kappaBkinase)-related kinase implicated in virus induction of interferon-beta (IFNbeta). We report that, although mice lacking IKKepsilon produce normal amounts of IFNbeta, they are hypersusceptible to viral infection because of a defect in the IFN signaling pathway. Specifically, a subset of type I IFN-stimulated genes are not activated in the absence of IKKepsilon because the interferon-stimulated gene factor 3 complex (ISGF3) does not bind to promoter elements of the affected genes. We demonstrate that IKKepsilon is activated by IFNbeta and that IKKepsilon directly phosphorylates signal transducer and activator of transcription 1 (STAT1), a component of ISGF3. We conclude that IKKepsilon plays a critical role in the IFN-inducible antiviral transcriptional response.
Naturally occurring strains of Newcastle disease virus (NDV) have shown oncolytic therapeutic efficacy in preclinical studies and are currently in clinical trials. Here, we have evaluated the possibility to enhance the cancer therapeutic potential of NDV by means of reverse genetics. Mice bearing s.c. implanted CT26 tumors were treated with intratumoral (i.t.) injections of a recombinant NDV modified to contain a highly fusogenic F protein. These treated mice exhibited significant reduction in tumor development compared with mice treated with the unmodified virus. Furthermore, mice in a CT26 metastatic tumor model treated with an i.v. injection of the genetically engineered NDV exhibited prolonged survival compared with wild-type control virus. In addition, we examined whether the oncolytic properties of NDV could be improved by expression of immunostimulatory molecules. In this regard, we engineered several NDVs to express granulocyte macrophage colony-stimulating factor, IFN-;, interleukin 2 (IL-2), or tumor necrosis factor A, and evaluated their therapeutic potential in an immunocompetent colon carcinoma tumor model. Mice bearing s.c. CT26 tumors treated with i.t. injections of recombinant NDV expressing IL-2 showed dramatic reductions in tumor growth, with a majority of the mice undergoing complete and long-lasting remission. Our data show the use of reverse genetics to develop enhanced recombinant NDV vectors as effective therapeutic agents for cancer treatment. [Cancer Res 2007;67(17):8285-92]
Influenza A virus leads to yearly epidemics and sporadic pandemics. Present prophylactic strategies focus on egg-grown, live, attenuated influenza vaccines (LAIVs), in which attenuation is generated by conferring temperature sensitivity onto the virus. Here we describe an alternative approach to attenuating influenza A virus based on microRNA-mediated gene silencing. By incorporating nonavian microRNA response elements (MREs) into the open-reading frame of the viral nucleoprotein, we generate reassortant LAIVs for H1N1 and H5N1 that are attenuated in mice but not in eggs. MRE-based LAIVs show a greater than two-log reduction in mortality compared with control viruses lacking MREs and elicit a diverse antibody response. This approach might be combined with existing LAIVs to increase attenuation and improve vaccine safety.
A coordinated innate and adaptive immune response, orchestrated by antigen presenting cells (APCs), is required for effective clearance of influenza A virus (IAV). Although IAV primarily infects epithelial cells of the upper respiratory tract, APCs are also susceptible. To determine if virus transcription in these cells is required to generate protective innate and adaptive immune responses, we engineered IAV to be selectively attenuated in cells of hematopoietic origin. Incorporation of hematopoietic-specific miR-142 target sites into the nucleoprotein of IAV effectively silenced virus transcription in APCs, but had no significant impact in lung epithelial cells. Here we demonstrate that inhibiting IAV replication in APCs in vivo did not alter clearance, or the generation of IAV-specific CD8 T cells, suggesting that cross-presentation is sufficient for cytotoxic T lymphocyte activation. In contrast, loss of in vivo virus infection, selectively in APCs, resulted in a significant reduction of retinoic acid-inducible gene I-dependent type I IFN (IFN-I). These data implicate the formation of virus replication intermediates in APCs as the predominant trigger of IFN-I in vivo. Taking these data together, this research describes a unique platform to study the host response to IAV and provides insights into the mechanism of antigen presentation and the induction of IFN-I.
MicroRNAs (miRNAs) are short noncoding RNAs that exert posttranscriptional gene silencing and regulate gene expression. In addition to the hundreds of conserved cellular miRNAs that have been identified, miRNAs of viral origin have been isolated and found to modulate both the viral life cycle and the cellular transcriptome. Thus far, detection of virus-derived miRNAs has been largely limited to DNA viruses, suggesting that RNA viruses may be unable to exploit this aspect of transcriptional regulation. Lack of RNA virus-produced miRNAs has been attributed to the replicative constraints that would incur following RNase III processing of a genomic hairpin. To ascertain whether the generation of viral miRNAs is limited to DNA viruses, we investigated whether influenza virus could be designed to deliver functional miRNAs without affecting replication. Here, we describe a modified influenza A virus that expresses cellular microRNA-124 (miR-124). Insertion of the miR-124 hairpin into an intron of the nuclear export protein transcript resulted in endogenous processing and functional miR-124. We demonstrate that a viral RNA genome incorporating a hairpin does not result in segment instability or miRNA-mediated genomic targeting, thereby permitting the virus to produce a miRNA without having a negative impact on viral replication. This work demonstrates that RNA viruses can produce functional miRNAs and suggests that this level of transcriptional regulation may extend beyond DNA viruses.
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