Differential IFN-gamma stimulation of HLA-A gene expression through CRM-1-dependent nuclear RNA export

The Influence of Arginine Methylation in Immunity and Inflammation

Exploration in the field of epigenetics has revealed that protein arginine methyltransferases (PRMTs) contribute to disease, and this has given way to the development of specific small molecule compounds that inhibit arginine methylation. Protein arginine methylation is known to regulate fundamental cellular processes, such as transcription; pre-mRNA splicing and other RNA processing mechanisms; signal transduction, including the anti-viral response; and cellular metabolism. PRMTs are also implicated in the regulation of physiological processes, including embryonic development, myogenesis, and the immune system. Finally, the dysregulation of PRMTs is apparent in cancer, neurodegeneration, muscular disorders, and during inflammation. Herein, we review the functions of PRMTs in immunity and inflammation. We also discuss recent progress with PRMTs regarding the modulation of gene expression related to T and B lymphocyte differentiation, germinal center dynamics, and anti-viral signaling responses, as well as the clinical relevance of using PRMT inhibitors alone or in combination with other drugs to treat cancer, immune, and inflammatory-related diseases.

Free ISG15 and protein ISGylation emerging in SARS-CoV-2 infection

Interferon-simulated gene 15 (ISG15) belongs to the family of ubiquitin-like proteins. ISG15 acts as a cytokine and modifies proteins through ISGylation. This posttranslational modification has been associated with antiviral and immune response pathways. In addition, it is known that the genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) encodes proteases critical for viral replication. Consequently, these proteases are also central in the progression of coronavirus disease 2019 (COVID-19). Interestingly, the protease SARS-CoV-2-PLpro removes ISG15 from ISGylated proteins such as IRF3 and MDA5, affecting immune and antiviral defense from the host. Here, the implications of ISG15, ISGylation, and generation of SARS-CoV-2-PLpro inhibitors in SARS-CoV-2 infection are discussed.

Spatial Analysis and Clinical Significance of HLA Class-I and Class-II Subunit Expression in Non-Small Cell Lung Cancer

PURPOSE

To analyze the distribution, associated immune contexture, and clinical significance of human leukocyte antigen (HLA) class-I and HLA class-II subunits in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Using spatially resolved and quantitative multiplexed immunofluorescence we studied the tumor/stromal tissue distribution, cancer cell-specific defects, and clinicopathologic/survival associations of β2 microglobulin (β2M), HLA-A, and HLA-B,-C heavy chains, as well as HLA class-II β chain in >700 immunotherapy-naïve NSCLCs from four independent cohorts. Genomic analysis of HLA genes in NSCLC was performed using two publicly available cohorts.

RESULTS

Cancer cell-specific downregulation of HLA markers was identified in 30.4% of cases. β2M was downregulated in 9.8% (70/714), HLA-A in 9% (65/722), HLA-B,-C in 12.1% (87/719), and HLA class-II in 17.7% (127/717) of evaluable samples. Concurrent downregulation of β2M, HLA-B,-C, and HLA class-II was commonly identified. Deleterious mutations in HLA genes were detected in <5% of lung malignancies. Tumors with cancer cell-specific β2M downregulation displayed reduced T cells and increased natural killer (NK)-cell infiltration. Samples with cancer cell HLA-A downregulation displayed modest increase in CD8⁺ T cells and NK-cell infiltration. Samples with cancer cell-selective HLA-B,-C or HLA class-II downregulation displayed reduced T cells and NK-cell infiltration. There was limited association of the markers with clinicopathologic variables and KRAS/EGFR mutations. Cancer cell-selective downregulation of the HLA subunits was associated with shorter overall survival.

CONCLUSIONS

Our results reveal frequent and differential defects in HLA class-I and HLA class-II protein subunit expression in immunotherapy-naïve NSCLCs associated with distinct tumor microenvironment composition and patient survival.

Immune co-culture cell microarray - a feasible tool for high-throughput functional investigation of lymphocyte-cancer interactions

Omics analyses often result in dozens to hundreds of potential targets, requiring validation for their biological relevance. Current high-throughput functional investigation methods are frequently labor-intensive, expensive, and display low reproducibility. The Immune Co-Culture Cell Microarray (ICCM) is a formalin-fixed paraffin-embedded cell block microarray based on co-cultures of patient-derived tumor-infiltrating lymphocytes and their autologous melanoma cells. Each ICCM slide represents the same experiment and can be stained using standard immunohistochemistry and immunofluorescence techniques. Functional dynamics assessment of both proteins and microRNAs using ICCM stained slides demonstrated similar findings to flow cytometry assays and to previously published patient-derived biopsy reports.

Differential expression and molecular interactions of chromosome region maintenance 1 and calreticulin exportins in breast cancer cells

Chromosome region maintenance 1 (CRM-1) and calreticulin (CALR) are two proteins that act as exportins for some nuclear receptors, in addition to other critical functions for cellular homeostasis. In several cancer types, CRM-1 and CALR are upregulated suggesting an imbalance in their functions. However, the regulation of CRM-1 and CALR, and their biological implications, are not completely known. Here, we evaluated the interplay between the levels of CRM-1 and CALR, and estrogen receptor alpha (ERα) status, in breast cancer cells. CRM-1 and CALR were upregulated in mammary tumors relative to normal mammary tissue. Furthermore, the mRNA and protein levels of CRM-1 and CALR were higher in breast cancer cells lacking ERα, in comparison with those that express ERα. Additionally, both proteins were distributed in the nucleus and cytoplasm in the two cell types. Importantly, we identified novel interactions for these exportins. First, we showed an interaction between CRM-1 and CALR, and then we identified that SUN1 and SUN2, two proteins localized in the nuclear envelop, were able to interact specifically with CRM-1, but not CALR. Interestingly, SUN1 and SUN2 expression seemed to be decreased in breast cancer, thereby affecting the interactions of these proteins with CRM-1, and possibly its actions as an exportin. Thus, our data suggest that expression levels for CRM-1 and CALR, the interaction between these exportins, and specific interactions of SUN1 and SUN2 with CRM-1 but not CALR, may be central elements in nucleo-cytoplasmic transport. Furthermore, deregulation of these elements may have serious implications in the progression of breast and other types of cancer.

Serum cholinesterase activity is elevated in female diarrhea-predominant irritable bowel syndrome patients compared to matched controls

BACKGROUND

Micro-inflammation is involved in the pathogenesis of irritable bowel syndrome (IBS). The parasympathetic nervous system, via acetylcholine (ACh), and its hydrolytic enzymes, plays a role in regulating inflammation. Increased serum cholinesterase activity, named cholinergic Status (CS), is associated with decreased inflammatory inhibition (ie, pro-inflammation). We assessed the association between IBS diarrhea-predominant (IBS-D) symptoms, CS, and inflammatory biomarkers.

METHODS

Women with IBS-D were prospectively recruited. Serum acetylcholinesterase (AChE), CS, and high-sensitivity C-reactive protein (hs-CRP) levels were analyzed and fecal calprotectin (FC) in a subgroup of patients. The control group included women attending routine health checkups (matched by age and BMI).

KEY RESULTS

Ninety-four women with IBS-D were compared to matched controls (1:1). Serum CS, AChE, and the AChE/butyrylcholinesterase (BChE) ratios were significantly increased in the IBS-D group compared to matched controls (P = 0.018, P = 0.001, and P = 0.004, respectively). Using a multiple logistic regression model, IBS-D was almost twice as likely in women with high CS compared to women with low CS (adjusted OR=1.84 (95% CI: 1.01-3.33), P = 0.045). Furthermore, IBS-D patients with higher hs-CRP levels demonstrated lower CS and BChE activity and elevated AChE and AChE/BChE ratios compared to patients with lower hs-CRP levels (P = 0.026, P = 0.036, P = 0.002; and P = 0.0007, respectively). CS was not correlated with the IBS symptoms score.

CONCLUSIONS AND INFERENCES

This is the first study to explore the potential role of serum CS in IBS-D. The findings emphasize the possible role of the autonomic nervous system and its anti-inflammatory properties in IBS.

Interplay between interferon-stimulated gene 15/ISGylation and interferon gamma signaling in breast cancer cells

Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like protein that conjugates to its target proteins to modify them through ISGylation, but the relevance of ISG15 expression and its effects have been not completely defined. Herein, we examined the interplay between ISG15/ISGylation and the interferon-gamma (IFN-γ) signaling pathway in mammary tumors and compared it with that in normal mammary tissues. Our results indicated that mammary tumors had higher levels of ISG15 mRNA and ISG15 protein than the adjacent normal mammary tissue. Furthermore, the expression of IFN-γ signaling components was altered in breast cancer. Interestingly, IFN-γ treatment induced morphological changes in MCF-7 and MDA-MB-231 breast cancer cell lines due to cytoskeletal reorganization. This cellular process seems to be related to the increase in ISGylation of cytoplasmic IQ Motif Containing GTPase Activating Protein 1 (IQGAP1). Interactome analysis also indicated that IFN-γ signaling and the ISGylation system are associated with several proteins implicated in cytoskeletal remodeling, including IQGAP1. Thus, ISG15 may present a potential biomarker for breast cancer, and IFN-γ signaling and protein ISGylation may participate in the regulation of the cytoskeleton in breast cancer cells.

Posttranscriptional Regulation of HLA-A Protein Expression by Alternative Polyadenylation Signals Involving the RNA-Binding Protein Syncrip

Genomic variation in the untranslated region (UTR) has been shown to influence HLA class I expression level and associate with disease outcomes. Sequencing of the 3'UTR of common HLA-A alleles indicated the presence of two polyadenylation signals (PAS). The proximal PAS is conserved, whereas the distal PAS is disrupted within certain alleles by sequence variants. Using 3'RACE, we confirmed expression of two distinct forms of the HLA-A 3'UTR based on use of either the proximal or the distal PAS, which differ in length by 100 bp. Specific HLA-A alleles varied in the usage of the proximal versus distal PAS, with some alleles using only the proximal PAS, and others using both the proximal and distal PAS to differing degrees. We show that the short and the long 3'UTR produced similar mRNA expression levels. However, the long 3'UTR conferred lower luciferase activity as compared with the short form, indicating translation inhibition of the long 3'UTR. RNA affinity pull-down followed by mass spectrometry analysis as well as RNA coimmunoprecipitation indicated differential binding of Syncrip to the long versus short 3'UTR. Depletion of Syncrip by small interfering RNA increased surface expression of an HLA-A allotype that uses primarily the long 3'UTR, whereas an allotype expressing only the short form was unaffected. Furthermore, specific blocking of the proximal 3'UTR reduced surface expression without decreasing mRNA expression. These data demonstrate HLA-A allele-specific variation in PAS usage, which modulates their cell surface expression posttranscriptionally.

Protein arginine methyltransferase 1 (PRMT1) represses MHC II transcription in macrophages by methylating CIITA

Efficient presentation of alien antigens triggers activation of T lymphocytes and robust host defense against invading pathogens. This pathophysiological process relies on the expression of major histocompatibility complex (MHC) molecules in antigen presenting cells such as macrophages. Aberrant MHC II transactivation plays a crucial role in the pathogenesis of atherosclerosis. Class II transactivator (CIITA) mediates MHC II induction by interferon gamma (IFN-γ). CIITA activity can be fine-tuned at the post-translational level, but the mechanisms are not fully appreciated. We investigated the role of protein arginine methyltransferase 1 (PRMT1) in this process. We report here that CIITA interacted with PRMT1. IFN-γ treatment down-regulated PRMT1 expression and attenuated PRMT1 binding on the MHC II promoter. Over-expression of PRMT1 repressed MHC II promoter activity while PRMT1 depletion enhanced MHC II transactivation. Mechanistically, PRMT1 methylated CIITA and promoted CIITA degradation. Therefore, our data reveal a previously unrecognized role for PRMT1 in suppressing CIITA-mediated MHC II transactivation.

Epigenetic regulation of differential HLA-A allelic expression levels

MHC class I expression levels influence the strength of immune responses and represent another variable in determining outcome to disease beyond peptide binding alone. Identification of the HLA loci that vary in allelic expression levels and delineating the mechanism responsible for expression variation may provide the opportunity to modify their expression therapeutically. We have examined the expression levels of allelic lineages at the HLA-A locus in a sample of 216 European Americans using a real-time polymerase chain reaction assay, which amplifies all HLA-A lineages specifically with equal efficiency, and observed a gradient of expression that associates with HLA-A allelic lineage (R = 0.6, P = 5 × 10(-25)). DNA methylation of the HLA-A gene appears to contribute to the variation in HLA-A mRNA expression levels, as a significant inverse correlation was observed between HLA-A mRNA expression levels in untreated cells and the degree to which expression is increased after treatment of the cells with a DNA methyltransferase inhibitor (R = 0.6, P = 2.8 × 10(-6)). Further, deep-sequencing and immunoprecipitation assays revealed allelic lineage-specific methylation patterns within the HLA-A promoter region where increased DNA methylation levels correlated significantly with reduced HLA-A expression levels (R = 0.89, P = 3.7 × 10(-9)). These data demonstrate HLA-A allelic lineage-specific variation in expression levels, and DNA methylation as a likely factor in contributing to this variation.

Nucleoporins and nucleocytoplasmic transport in hematologic malignancies

Hematologic malignancies are often associated with chromosomal rearrangements that lead to the expression of chimeric fusion proteins. Rearrangements of the genes encoding two nucleoporins, NUP98 and NUP214, have been implicated in the pathogenesis of several types of hematologic malignancies, particularly acute myeloid leukemia. NUP98 rearrangements result in fusion of an N-terminal portion of NUP98 to one of numerous proteins. These rearrangements often follow treatment with topoisomerase II inhibitors and tend to occur in younger patients. They have been shown to induce leukemia in mice and to enhance proliferation and disrupt differentiation in primary human hematopoietic precursors. NUP214 has only a few fusion partners. DEK-NUP214 is the most common NUP214 fusion in AML; it tends to occur in younger patients and is usually associated with FLT3 internal tandem duplications. The leukemogenic activity of NUP214 fusions is less well characterized. Normal nucleoporins, including NUP98 and NUP214, have important functions in nucleocytoplasmic transport, transcription, and mitosis. These functions and their disruptions by oncogenic nucleoporin fusions are discussed.

Human inducible nitric oxide synthase (iNOS) expression depends on chromosome region maintenance 1 (CRM1)- and eukaryotic translation initiation factor 4E (elF4E)-mediated nucleocytoplasmic mRNA transport

Human inducible nitric oxide synthase (iNOS) is regulated on the expressional level mostly by post-transcriptional mechanisms modulating the mRNA stability. Another important step in the control of eukaryotic gene expression is the nucleocytoplasmic mRNA transport. Most cellular mRNAs are exported via the TAP/Nxt complex of proteins. However, some mRNAs are transported by a different mechanism involving the nuclear export receptor CRM1. Treatment of DLD-1 cells with the CRM1 inhibitor leptomycin B (LMB) or anti-CRM1 siRNAs reduced cytokine-induced iNOS expression. We could demonstrate that the iNOS mRNA is exported from the nucleus in a CRM1-dependent manner. Since CRM1 itself does not possess any RNA binding affinity, an adapter protein is needed to mediate CRM1-dependent mRNA export. Western blot experiments showed that the eukaryotic translation initiation factor eIF4E is retained in the nucleus after LMB treatment. Blockade of eIF4E by ribavirin or overexpression of the promyelocytic leukemia protein (PML) decreased iNOS expression due to reduced iNOS mRNA export from the nucleus. Transfection experiments provide evidence that the 3'-untranslated region of the iNOS mRNA is involved in eIF4E-mediated iNOS mRNA transport. In summary, CRM1 and eIF4E seem to play an important role in the nucleocytoplasmic export of human iNOS mRNA.

A novel post-transcriptional role for ubiquitin in the differential regulation of MHC class I allotypes

By providing ligands for Cytotoxic T-Lymphocytes (CTL) as well as Natural Killer (NK) cells, the HLA-A/B/C MHC class I molecules (MHC-I) play a central role in both innate and adaptive immunity. In addition to CTL-mediated recognition of MHC-peptide complexes, cell surface expression of MHC-I is closely monitored by NK cells, whose killer-cell immunoglobulin-like receptors encode activatory and inhibitory receptors with specificity for MHC-I. How the cell surface expression of MHC-I is tightly controlled is not well understood. In a functional siRNA ubiquitome screen to identify E3 ligases involved in MHC-I regulation we recently found that MEX-3C, a novel RNA-binding ubiquitin E3 ligase, is responsible for the post-transcriptional, HLA-A allotype-specific regulation of MHC-I. MEX-3C expression is increased upon NK cell activation and modulates the threshold of killing by these cells. We find that MEX-3C binds the 3′-untranslated region of HLA-A2 mRNA, inducing its RING-dependent degradation. The RING domain of MEX-3C is not required for HLA-A2 cell surface downregulation, but regulates the degradation of HLA-A2 mRNA. We have therefore uncovered a novel post-transcriptional pathway for regulation of HLA-A allotypes and provide a direct link between ubiquitination and mRNA decay.

Porcine MHC classical class I genes are coordinately expressed in superantigen-activated mononuclear cells

The expression of the major histocompatibility complex (MHC) classical class I genes is important for the adaptive immune response to target virus-infected cells and cancer cells. The up-regulation of the MHC is achieved by hormonal/cytokine signals including IFN-γ-inducible elements. The swine leukocyte antigen (SLA), the MHC class I region of pigs, consists of the duplicated classical class I genes, SLA-1, SLA-2 and SLA-3, but the molecular mechanisms involved in their up-regulation after T cell stimulation have not been fully elucidated. In order to better understand some of the putative regulatory mechanisms of SLA class I gene expression in activated T cells, we examined the coordinated expression of the SLA classical class I, IFN-γ and interferon regulatory factor-1 (IRF-1) genes in the peripheral blood mononuclear cells (PBMCs) of SLA homozygous Clawn miniature swine stimulated for 72 h with either IFN-γ or an enterotoxin produced by Staphylococcus aureus. This enterotoxin, toxic shock syndrome-1 (TSST-1), is known to act as a superantigen (sAG) to activate the T cells in various vertebrate species. We showed by using mAbs and flow cytometry that the CD4(+)CD25(+) cell number of swine PBMCs was also increased by TSST-1 and to a lesser degree by IFN-γ. Time course analyses of the expression of the IFN-γ, IRF-1 and the three classical class I genes, SLA-1, SLA-2, and SLA-3, in PBMCs by quantitative real-time PCR revealed a transitory response to TSST-1 or IFN-γ stimulation. The IFN-γ mRNA levels in the PBMCs were continuously up-regulated over the first 48 h by TSST-1 or IFN-γ. In contrast, SLA class I expression moderately increased at 24h and then decreased to a baseline level or less at 72 h of IFN-γ or TSST-1 stimulation. The three classical SLA class I genes showed similar expression kinetics, although SLA-3 mRNA level was consistently lower than those of SLA-1 and -2. The expression of IRF-1, a modulator of SLA expression, showed similar kinetics to those of the three classical SLA class I genes. The expression profiles detected by flow cytometry of the SLA molecules on the cell surface of PBMCs were maintained at a consistently high level during cell stimulation with either TSST-1 or IFN-γ, which was distinct from the kinetics of mRNA expression. These results showed that miniature swine SLA class I mRNA expression was effectively and equally up-regulated among the three loci and coordinately with IRF-1 gene expression after stimulation of T cell activation by sAG or IFN-γ.

Functional characterization of the HuR:CD83 mRNA interaction

Maturation of dendritic cells (DC) is characterized by expression of CD83, a surface protein that appears to be necessary for the effective activation of naïve T-cells and T-helper cells by DC. Lately it was shown that CD83 expression is regulated on the posttranscriptional level by interaction of the shuttle protein HuR with a novel posttranscriptional regulatory RNA element (PRE), which is located in the coding region of the CD83 transcript. Interestingly, this interaction commits the CD83 mRNA to efficient nuclear export via the CRM1 pathway. To date, however, the structural basis of this interaction, which potentially involves three distinct RNA recognition motifs (RRM1–3) in HuR and a complex three-pronged RNA stem-loop element in CD83 mRNA, has not been investigated in detail. In the present work we analyzed this interaction in vitro and in vivo using various HuR- and CD83 mRNA mutants. We are able to demonstrate that both, RRM1 and RRM2 are crucial for binding, whereas RRM3 as well as the HuR hinge region contributed only marginally to this protein∶RNA interaction. Furthermore, mutation of uridine rich patches within the PRE did not disturb HuR:CD83 mRNA complex formation while, in contrast, the deletion of specific PRE subfragments from the CD83 mRNA prevented HuR binding in vitro and in vivo. Interestingly, the observed inhibition of HuR binding to CD83 mRNA does not lead to a nuclear trapping of the transcript but rather redirected this transcript from the CRM1- towards the NXF1/TAP-specific nuclear export pathway. Thus, the presence of a functional PRE permits nucleocytoplasmic trafficking of the CD83 transcript via the CRM1 pathway.

Comparison of different methods for DNA-free RNA isolation from SK-N-MC neuroblastoma

Background

RNA quality and quantity are important factors for ensuring the accuracy of gene expression analysis and other RNA-based downstream applications. Extraction of high quality nucleic acids is difficult from neuronal cells and brain tissues as they are particularly rich in lipids. In addition, most common RNA extraction methods are phenol-based, resulting in RNA that may be incompatible with downstream applications such as gene expression.

Findings

In this work, a comparative analysis of the RNA quality obtained from SK-N-MC cells was performed using six commonly used RNA isolation kits: two phenol-based kits and four non-phenol based kits. The non-phenol based kits tested AxyPrep Multisource Total RNA Miniprep, RNeasy^® Mini, EasySpin and Ilustra RNAspin Mini RNA Isolation, all performed well and resulted in the isolation of high quality RNA, as evaluated by A₂₆₀/A₂₈₀. The RNA extracted with AxyPrep Multisource Total RNA Miniprep, RNeasy^® Mini and EasySpin provided the highest RNA yields. In particular, the RNA isolated by AxyPrep Multisource Total RNA Miniprep Kit did not show any detectable genomic DNA contamination even without previous DNase treatment or after RNA direct PCR amplification using universal 18S primers.

Conclusions

The RNA extracted from SK-N-MC cells with AxyPrep Multisource Total RNA Miniprep Kit was superior with respect to the RNA quality and concentration. This kit does not use aggressive organic solvents and RNA free of genomic DNA was isolated without the need for DNase treatment.

Impaired cell surface expression of HLA-B antigens on mesenchymal stem cells and muscle cell progenitors

HLA class-I expression is weak in embryonic stem cells but increases rapidly during lineage progression. It is unknown whether all three classical HLA class-I antigens follow the same developmental program. In the present study, we investigated allele-specific expression of HLA-A, -B, and -C at the mRNA and protein levels on human mesenchymal stem cells from bone marrow and adipose tissue as well as striated muscle satellite cells and lymphocytes. Using multicolour flow cytometry, we found high cell surface expression of HLA-A on all stem cells and PBMC examined. Surprisingly, HLA-B was either undetectable or very weakly expressed on all stem cells protecting them from complement-dependent cytotoxicity (CDC) using relevant human anti-B and anti-Cw sera. IFNgamma stimulation for 48-72 h was required to induce full HLA-B protein expression. Quantitative real-time RT-PCR showed that IFNgamma induced a 9-42 fold increase of all six HLA-A,-B,-C gene transcripts. Interestingly, prior to stimulation, gene transcripts for all but two alleles were present in similar amounts suggesting that post-transcriptional mechanisms regulate the constitutive expression of HLA-A,-B, and -C. Locus-restricted expression of HLA-A, -B and -C challenges our current understanding of the function of these molecules as regulators of CD8(+) T-cell and NK-cell function and should lead to further inquiries into their expression on other cell types.

Generation of human dendritic cells that simultaneously secrete IL-12 and have migratory capacity by adenoviral gene transfer of hCD40L in combination with IFN-gamma

Dendritic cells (DCs) are professional antigen presenting cells and have key functions in the initiation of immune responses. Hence, antigen-loaded DCs have become important tools for active-specific immunotherapy. In addition to defining strategies for antigen loading, effective T-cell activation by DCs will depend on vaccination protocols that facilitate DC migration to secondary lymphoid tissues and expression of costimulatory molecules and cytokines. Adenoviral gene transfer has been successfully implemented for genetic antigen loading of DCs. In this study, we exploit an adenoviral vector encoding human CD40 ligand (CD40L), Ad5hCD40L, to establish DCs that feature both migration potential and prolonged secretion of the key T-helper 1 cytokine interleukin-12p70 (IL-12p70). Transduction of human monocyte-derived DCs with Ad5hCD40L resulted in efficient CD40L expression, which was detected only intracellularly, and in secretion of IL-12p70. Addition of recombinant interferon (IFN)-gamma shortly after DC transduction substantially increased IL-12p70 secretion. Maturation of DCs was achieved with a standard cytokine maturation cocktail (MC) containing prostaglandin E2 which, however, abolished IL-12p70 secretion by Ad5hCD40L-transduced cells in the absence of IFN-gamma. Only DCs treated with Ad5hCD40L, MC, and IFN-gamma migrated efficiently towards CCL19 and continued to secrete IL-12p70. Finally, DCs transduced with both Ad5hCD40L and an adenoviral vector encoding the melanoma antigen MelanA/MART-1 and treated with MC and IFN-gamma efficiently primed naive autologous CD8+ T cells into antigen-specific cytotoxic T lymphocyte. This strategy to generate DCs that exert both migration capacity and prolonged IL-12p70 secretion after intracellular CD40L expression and IFN-gamma treatment has the potential to further improve current DC vaccination protocols.

Human DEAD-box protein 3 has multiple functions in gene regulation and cell cycle control and is a prime target for viral manipulation

The human DEAD-box RNA helicase DDX3 has been implicated to play a role in the whole repertoire of processes regulating gene expression, including transcription, splicing, mRNA export and translation. It has also been suggested to be involved in cell cycle control and the regulation of apoptosis. In addition, DDX3 was recently shown to be part of innate immune signalling pathways and to contribute to the induction of anti-viral mediators, such as type I interferon. Interestingly, DDX3 appears to be a prime target for viral manipulation: at least four different viruses, namely Hepatitis C virus (HCV), Hepatitis B virus (HBV), Human Immunodeficiency Virus (HIV) and poxviruses, encode proteins that interact with DDX3 and modulate its function. HIV and HCV seem to co-opt DDX3 and require it for their replication. It has therefore been suggested that DDX3 could be a novel target for the development of drugs against these two viruses, both of which still pose major global health threats. However, in the light of the apparent multifunctionality of DDX3 in the cell, drug development strategies targeting DDX3 will have to be carefully evaluated. This review summarises the available data on the cellular functions of DDX3 and discusses their manipulation by the different viruses known to target DDX3. Understanding the viral strategies for manipulating or co-opting DDX3 in functional and molecular detail can provide valuable insights for the development of strategies to therapeutically target DDX3.