Trans-amplifying RNA expressing functional miRNA mediates target gene suppression and simultaneous transgene expression.

The co-delivery of microRNAs (miRNAs) and protein-coding RNA presents an opportunity for a combined approach to gene expression and gene regulation for therapeutic applications. Protein delivery is established using long mRNA, self-, and trans-amplifying RNA (taRNA), whereas miRNA delivery typically uses short synthetic oligonucleotides rather than incorporating it as a precursor into long RNA. Although miRNA delivery into the cell cytoplasm using long genomes of RNA viruses has been described, concerns have remained regarding low processing efficiency. However, miRNA precursors can be released from long cytoplasmic alphaviral RNA by a cytoplasmic fraction of Drosha. taRNA, a promising vector platform for infectious disease vaccination, uses a nonreplicating mRNA expressing an alphaviral replicase to amplify a protein-coding short transreplicon-RNA (STR) in trans. To investigate the possibility of simultaneously delivering protein expression and gene silencing, we tested whether a taRNA system can carry and release functional miRNA to target cells. Here, we show that mature miRNA is released from STRs and silences specific targets in a replication-dependent manner for several days without compromising the expression of STR-encoded proteins. Our findings suggest that incorporating miRNAs into the taRNA vector platform has the potential for gene regulation alongside the expression of therapeutic genes.

Improving mRNA-Based Therapeutic Gene Delivery by Expression-Augmenting 3' UTRs Identified by Cellular Library Screening.

Synthetic mRNA has emerged as a powerful tool for the transfer of genetic information, and it is being explored for a variety of therapeutic applications. Many of these applications require prolonged intracellular persistence of mRNA to improve bioavailability of the encoded protein. mRNA molecules are intrinsically unstable and their intracellular kinetics depend on the UTRs embracing the coding sequence, in particular the 3' UTR elements. We describe here a novel and generally applicable cell-based selection process for the identification of 3' UTRs that augment the expression of proteins encoded by synthetic mRNA. Moreover, we show, for two applications of mRNA therapeutics, namely, (1) the delivery of vaccine antigens in order to mount T cell immune responses and (2) the introduction of reprogramming factors into differentiated cells in order to induce pluripotency, that mRNAs tagged with the 3' UTR elements discovered in this study outperform those with commonly used 3' UTRs. This approach further leverages the utility of mRNA as a gene therapy drug format.

Recombinant messenger RNA technology and its application in cancer immunotherapy, transcript replacement therapies, pluripotent stem cell induction, and beyond.

In recent years, the interest in using messenger RNA (mRNA) as a therapeutic means to tackle different diseases has enormously increased. This holds true not only for numerous preclinical studies, but mRNA has also entered the clinic to fight cancer. The advantages of using mRNA compared to DNA were recognized very early on, e.g., the lack of risk for genomic integration, or the expression of the encoded protein in the cytoplasm without the need to cross the nuclear membrane. However, it was generally assumed that mRNA is just not stable enough to give rise to sufficient expression of the encoded protein. Yet, an initially small group of mRNA aficionados could demonstrate that the stability of mRNA and the efficiency, by which the encoded protein is translated, can be significantly increased by selecting the right set of cis-acting structural elements (including the 5'-cap, 5'- and 3'-untranslated regions, poly(A)-tail, and modified building blocks). In parallel, significant advances in RNA packaging and delivery have been made, extending the potential for this molecule. This paved the way for further work to prove mRNA as a promising therapeutic for multiple diseases. Here, we review the developments to optimize mRNA regarding stability, translational efficiency, and immune-modulating properties to enhance its functionality and efficacy as a therapeutic. Furthermore, we summarize the current status of preclinical and clinical studies that use mRNA for cancer immunotherapy, for the expression of functional proteins as so-called transcript (or protein) replacement therapy, as well as for induction of pluripotent stem cells.

Genome-wide analysis displays marked induction of EBI3/IL-27B in IL-18-activated AML-derived KG1 cells: critical role of two kappaB binding sites in the human EBI3 promotor.

The cell line KG1 is derived from a patient with acute myeloid leukemia. Activation of KG1 cells by interleukin (IL)-18 is associated with induction of key Th1 signature parameters such as T-bet and interferon-gamma. Here we set out to characterize the genome-wide mRNA expression profile under the condition of short-term stimulation (4h) with IL-18 using the Affymetrix GeneChip((R)) Array System. Besides the chemokines CXCL10, CXCL11, and CCL1 we identified Epstein-Barr virus induced gene-3 (EBI3)/IL-27B as being among those genes that are profoundly upregulated by IL-18 in KG1 cells. Thorough investigation revealed that IL-18-induced EBI3 mRNA efficiently translates into protein. Electromobility shift analysis and mutational analysis of the human EBI3 promoter identified two nuclear factor-kappaB binding sites as being crucial for induction by pro-inflammatory cytokines like IL-18. In addition, we demonstrate that KG1 cells express the Type A IL-27 receptor chain (WSX-1) and display STAT-1, -3 activation as well as induction of SOCS-3 under the influence of IL-27. IL-18 shows therapeutic potential in murine leukemia and is currently being evaluated in phase II clinical trials for the treatment of immunologically sensitive cancers. Since IL-27 mediates anti-cancer bioactivity in animal models, data presented herein may add a novel facet to tumorsuppressive characteristics of IL-18.

Interleukin-18 directly activates T-bet expression and function via p38 mitogen-activated protein kinase and nuclear factor-kappaB in acute myeloid leukemia-derived predendritic KG-1 cells.

The leukemic cell line KG-1 was isolated from a patient with acute myeloid leukemia and is regarded a cellular model of human dendritic cell progenitors. The T helper type 1 cytokine interleukin (IL)-18 has been shown to induce the maturation of these cells towards a dendritic phenotype and, moreover, is able to mediate IFNgamma production in this model. Because T-box expressed in T cells (T-bet) is considered to be of paramount importance for dendritic cell function, the effects of IL-18 on this transcription factor have been investigated in the current study. Here, we show that activation of KG-1 cells by IL-18 induces T-bet mRNA and protein within 4 to 6 h of incubation. This hitherto unrecognized function of IL-18 was suppressed by the inhibition of p38 mitogen-activated protein kinase activity and nuclear factor-kappaB function. Blockage of translation by cycloheximide, usage of neutralizing antibodies, and the inability of IFNgamma to mediate significant p38 mitogen-activated protein kinase activation in KG-1 cells clearly revealed that activation of T-bet was not via autocrine IFNgamma. T-bet function was evaluated by short interfering RNA technology. Notably, specific suppression of T-bet induction impaired secretion of IFNgamma by KG-1 cells under the influence of IL-18. Therapeutic application of IL-18 has the potential to profoundly affect the biology of acute myeloid leukemia predendritic cells such as KG-1 cells. Under these conditions, activation of T-bet may play a key role in processes that have the potential to correct the T helper type 1 deficiency associated with leukemia-mediated immunosuppression.

Expanding extracellular zinc beyond levels reflecting the albumin-bound plasma zinc pool potentiates the capability of IL-1beta, IL-18, and IL-12 to Act as IFN-gamma-inducing factors on PBMC.

The mixed cell population of freshly isolated peripheral blood mononuclear cells (PBMCs) is a widely used cell culture model for studying human cytokine networks, in particular production of immunoregulatory interferon-gamma (IFN-gamma). Here, we demonstrate that nontoxic concentrations of zinc (15 muM), employed as zinc chloride (ZnCl(2)), that are about 2-fold of the readily accessible pool of albumin-bound zinc in the plasma, strongly enhance the potential of interleukin-1beta (IL-1beta) to act as an IFN-gamma-inducing factor on PBMCs. In contrast, zinc supplementation approximately resembling the albumin-bound plasma pool (7.5 muM) did not significantly affect cytokine-induced IFN-gamma secretion. ZnCl(2) also amplified IFN-gamma production under the influence of IL-12 or IL-18, whereas IL-1beta-induced IL-8 expression was not enhanced by the addition of ZnCl(2), indicating that the effect observed on cytokine-induced IFN-gamma is not of a general and unspecific nature. The current observation not only agrees with the immunoregulatory aspects of zinc as seen in vivo but also indicates that modulating the extracellular pool of accessible zinc may dramatically affect cytokine biology, as observed in experimental cell research.

Interleukin-18 secretion and Th1-like cytokine responses in human peripheral blood mononuclear cells under the influence of the toll-like receptor-5 ligand flagellin.

Flagellin is the major protein component of the flagella from motile bacteria and was identified as the ligand for toll-like receptor (TLR)-5. Whereas its effects on epithelial cells have been studied in detail, activation of human peripheral blood mononuclear cells (PBMC) by flagellin is characterized only partially. By using the recombinant protein of Salmonella muenchen we confirm the proinflammatory nature of flagellin as detected by nuclear factor-kappaB activation and interleukin (IL)-8 production. Aim of the current study was to elucidate in PBMC effects of flagellin on IL-18 and Th1-like cytokine responses. We report that flagellin in pathophysiologically relevant concentrations augmented release of mature IL-18 by THP-1 monocytes, PBMC, and whole blood stimulated with nigericin or by ATP-mediated P2X7 purinergic receptor activation. Further key functions of the IL-18/IL-12/interferon-gamma (IFNgamma) pathway were upregulated by flagellin. Flagellin synergized with IL-12 for production of IFN-gamma and augmented secretion of interferon-inducible protein-10, a CXC-chemokine that is key to the generation of Th1-type responses. In contrast, neither IL-18-binding protein nor IL-4 was affected. Taken together, the present data demonstrate for the first time that flagellin at concentrations that are detectable in the blood compartment during sepsis efficiently enhances the IL-18/IL-12/IFNgamma pathway and thus Th1-like cytokine responses in PBMC.