Induction of interferon synthesis and activation of interferon-stimulated genes by liposomal transfection reagents

Virion-incorporated CD14 enables HIV-1 to bind LPS and initiate TLR4 signaling in immune cells

HIV-1 has a broad range of nuanced interactions with the immune system, and the incorporation of cellular proteins by nascent virions continues to redefine our understanding of the virus-host relationship. Proteins located at the sites of viral egress can be selectively incorporated into the HIV-1 envelope, imparting new functions and phenotypes onto virions, and impacting viral spread and disease. Using virion capture assays and western blot, we show that HIV-1 can incorporate the myeloid antigen CD14 into its viral envelope. Virion-incorporated CD14 remained biologically active and able to bind its natural ligand, bacterial lipopolysaccharide (LPS), as demonstrated by flow virometry and immunoprecipitation assays. Using a Toll-like receptor 4 (TLR4) reporter cell line, we also demonstrated that virions with bound LPS can trigger TLR4 signaling to activate transcription factors that regulate inflammatory gene expression. Complementary assays with THP-1 monocytes demonstrated enhanced secretion of inflammatory cytokines like tumor necrosis factor alpha (TNF-α) and the C-C chemokine ligand 5 (CCL5), when exposed to LPS-loaded virus. These data highlight a new type of interplay between HIV-1 and the myeloid cell compartment, a previously well-established cellular contributor to HIV-1 pathogenesis and inflammation. Persistent gut inflammation is a hallmark of chronic HIV-1 infection, and contributing to this effect is the translocation of microbes across the gut epithelium. Our data herein provide proof of principle that virion-incorporated CD14 could be a novel mechanism through which HIV-1 can drive chronic inflammation, facilitated by HIV-1 particles binding bacterial LPS and initiating inflammatory signaling in TLR4-expressing cells.IMPORTANCEHIV-1 establishes a lifelong infection accompanied by numerous immunological changes. Inflammation of the gut epithelia, exacerbated by the loss of mucosal T cells and cytokine dysregulation, persists during HIV-1 infection. Feeding back into this loop of inflammation is the translocation of intestinal microbes across the gut epithelia, resulting in the systemic dissemination of bacterial antigens, like lipopolysaccharide (LPS). Our group previously demonstrated that the LPS receptor, CD14, can be readily incorporated by HIV-1 particles, supporting previous clinical observations of viruses derived from patient plasma. We now show that CD14 can be incorporated by several primary HIV-1 isolates and that this virion-incorporated CD14 can remain functional, enabling HIV-1 to bind to LPS. This subsequently allowed CD14+ virions to transfer LPS to monocytic cells, eliciting pro-inflammatory signaling and cytokine secretion. We posit here that virion-incorporated CD14 is a potential contributor to the dysregulated immune responses present in the setting of HIV-1 infection.

Initiation of a ZAKα-dependent ribotoxic stress response by the innate immunity endoribonuclease RNase L

RNase L is an endoribonuclease of higher vertebrates that functions in antiviral innate immunity. Interferons induce oligoadenylate synthetase enzymes that sense double-stranded RNA of viral origin leading to the synthesis of 2',5'-oligoadenylate (2-5A) activators of RNase L. However, it is unknown precisely how RNase L remodels the host cell transcriptome. To isolate effects of RNase L from other effects of double-stranded RNA or virus, 2-5A is directly introduced into cells. Here, we report that RNase L activation by 2-5A causes a ribotoxic stress response involving the MAP kinase kinase kinase (MAP3K) ZAKα, MAP2Ks, and the stress-activated protein kinases JNK and p38α. RNase L activation profoundly alters the transcriptome by widespread depletion of mRNAs associated with different cellular functions but also by JNK/p38α-stimulated induction of inflammatory genes. These results show that the 2-5A/RNase L system triggers a protein kinase cascade leading to proinflammatory signaling and apoptosis.

Rabies virus P protein binds to TBK1 and interferes with the formation of innate immunity-related liquid condensates

Viruses must overcome the interferon-mediated antiviral response to replicate and propagate into their host. Rabies virus (RABV) phosphoprotein P is known to inhibit interferon induction. Here, using a global mass spectrometry approach, we show that RABV P binds to TBK1, a kinase located at the crossroads of many interferon induction pathways, resulting in innate immunity inhibition. Mutations of TBK1 phosphorylation sites abolish P binding. Importantly, we demonstrate that upon RABV infection or detection of dsRNA by innate immunity sensors, TBK1 and its adaptor proteins NAP1 and SINTBAD form dynamic cytoplasmic condensates that have liquid properties. These condensates can form larger aggregates having ring-like structures in which NAP1 and TBK1 exhibit locally restricted movement. P binding to TBK1 interferes with the formation of these structures. This work demonstrates that proteins of the signaling pathway leading to interferon induction transiently form liquid organelles that can be targeted by viruses.

IFI16 restricts HSV-1 replication by accumulating on the hsv-1 genome, repressing HSV-1 gene expression, and directly or indirectly modulating histone modifications

Interferon-γ inducible factor 16 (IFI16) is a multifunctional nuclear protein involved in transcriptional regulation, induction of interferon-β (IFN-β), and activation of the inflammasome response. It interacts with the sugar-phosphate backbone of dsDNA and modulates viral and cellular transcription through largely undetermined mechanisms. IFI16 is a restriction factor for human cytomegalovirus (HCMV) and herpes simplex virus (HSV-1), though the mechanisms of HSV-1 restriction are not yet understood. Here, we show that IFI16 has a profound effect on HSV-1 replication in human foreskin fibroblasts, osteosarcoma cells, and breast epithelial cancer cells. IFI16 knockdown increased HSV-1 yield 6-fold and IFI16 overexpression reduced viral yield by over 5-fold. Importantly, HSV-1 gene expression, including the immediate early proteins, ICP0 and ICP4, the early proteins, ICP8 and TK, and the late proteins gB and Us11, was reduced in the presence of IFI16. Depletion of the inflammasome adaptor protein, ASC, or the IFN-inducing transcription factor, IRF-3, did not affect viral yield. ChIP studies demonstrated the presence of IFI16 bound to HSV-1 promoters in osteosarcoma (U2OS) cells and fibroblasts. Using CRISPR gene editing technology, we generated U2OS cells with permanent deletion of IFI16 protein expression. ChIP analysis of these cells and wild-type (wt) U2OS demonstrated increased association of RNA polymerase II, TATA binding protein (TBP) and Oct1 transcription factors with viral promoters in the absence of IFI16 at different times post infection. Although IFI16 did not alter the total histone occupancy at viral or cellular promoters, its absence promoted markers of active chromatin and decreased those of repressive chromatin with viral and cellular gene promoters. Collectively, these studies for the first time demonstrate that IFI16 prevents association of important transcriptional activators with wt HSV-1 promoters and suggest potential mechanisms of IFI16 restriction of wt HSV-1 replication and a direct or indirect role for IFI16 in histone modification.

Electroporation formulation for cell therapy

Cell transfection efficiency often determines the success of cell-based gene therapy. Cell transfection via Nucleofector technology yields high transfection efficiency and low cytotoxicity. However, owing to trade secrecy, the components in each buffer are unknown, which not only increases the cost of electroporation studies but also limits the application of Nucleofector in clinical cell-based gene therapies. Thus, we developed a three-step method to determine the optimal conditions, including buffer, program, and additional polymer, in electroporation for multiple cancers and stem cell lines. This method could reduce the cost, allow researchers to find the optimal electroporation conditions for their cell lines of interest, and greatly boost the application potential of electroporation in clinical cell-based gene therapies.

Induction of CC-chemokines with antiviral function in macrophages by the human T lymphotropic virus type 2 transactivating protein, Tax2

Recent data provide evidence that co-infection with human immunodeficiency virus type 1 (HIV-1) and human T lymphotropic virus type 2 (HTLV-2) delays progression to AIDS compared to isolated HIV-1 infection. These results were linked to expression of the HTLV-2 transcriptional activating gene known as Tax2. Preliminary studies in lymphocytic systems suggest that Tax2 is responsible for induction of CC-chemokines, which play a major role in innate immune responses against HIV-1. In this study, the effect of Tax2 on CC-chemokines (MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5) in monocyte-derived macrophages (MDMs) was evaluated. An immortalized human monocytic cell line (U937) and donor-derived MDMs were used to evaluate these interactions. These cells were cultured in vitro, allowed to mature into macrophages for 14 d, and treated with Tax2 or Tax1 (the transcriptional activator of HTLV-1) at three concentrations (1, 10, and 100 pM) daily thereafter. Extracellular bacterial extract (EBE) lacking the vector and untreated samples served as controls. An additional group of donor-derived MDMs were transduced with an adenovirus vector that expressed either Tax2 or green fluorescent protein (GFP). Liposomal transfection agents alone were used as controls. Supernatants were collected from each sample on multiple days post-maturation and evaluated for MIP-1α, MIP-1β, and RANTES, by enzyme-linked immunosorbent assay. Analysis of variance and Tukey's Honestly Significant Difference tests were used to analyze the results. In all systems, cells exposed to either Tax2 or Tax1 expressed significantly (p<0.01) higher concentrations of CC-chemokines than controls. There was no significant difference in chemokine expression between Tax1-treated and Tax2-treated samples, between EBE-treated and EBE-untreated samples, or between GFP-transduced MDMs and controls. This suggests that HTLV-2 could alter innate immune responses in macrophagic reservoirs of HIV-1 in HIV-1/HTLV-2 co-infected individuals, and could guide the development of HIV-1 treatments.

Cell fusion-induced activation of interferon-stimulated genes is not required for restriction of a herpes simplex virus VP16/ICP0 mutant in heterokarya formed between permissive and restrictive cells

Herpes simplex virus VP16 and ICP0 mutants replicate efficiently in U2OS osteosarcoma cells but are restricted in other cell types. We previously showed that the restrictive phenotype is dominant in a transient cell fusion assay, suggesting that U2OS cells lack an antiviral mechanism present in other cells. Recent data indicate that unscheduled membrane fusion events can activate the expression of interferon-stimulated genes (ISGs) in fibroblasts, raising the possibility that our earlier results were due to a fusion-induced antiviral state. However, we show here that the permissive phenotype is also extinguished following fusion with Vero cells in the absence of ISG induction.

Regulation of TLR2 expression and function in human airway epithelial cells

Toll-like receptor (TLR1-6) mRNAs are expressed in normal human bronchial epithelial cells with higher basal levels of TLR3. TLR2 mRNA and plasma membrane protein expression was enhanced by pretreatment with Poly IC, a synthetic double-stranded RNA (dsRNA) known to activate TLR3. Poly IC also enhanced mRNA expression of adaptor molecules (MyD88 and TIRAP) and coreceptors (Dectin-1 and CD14) involved in TLR2 signaling. Additionally, mRNA expression of TLR3 and dsRNA-sensing proteins MDA5 and RIG-I increased following Poly IC treatment. In contrast, basal mRNA expression of TLR5 and TLR2 coreceptor CD36 was reduced by 77% and 62%, respectively. ELISA of apical and basolateral solutions from Poly IC-stimulated monolayers revealed significantly higher levels of IL-6 and GM-CSF compared with the TLR2 ligand PAM(3)CSK(4). Pretreatment with anti-TLR2 blocking antibody inhibited the PAM(3)CSK(4)-induced increase in IL-6 secretion after Poly IC exposure. An increase in IL-6 secretion was also observed in cells stimulated with Alternaria extract after pretreatment with Poly IC. However, IL-6 secretion was not stimulated by zymosan or lipothechoic acid (LTA). These data demonstrated that upregulation of TLR2 following exposure to dsRNA enhances functional responses of the airway epithelium to certain (PAM(3)CSK(4)), but not all (zymosan, LTA) TLR2 ligands and that this is likely due to differences in coreceptor expression.

Host cell cytokines induced by Chlamydia pneumoniae decrease the expression of interstitial collagens and fibronectin in fibroblasts

Chlamydia pneumoniae infection has been associated with chronic obstructive airway disease (COPD), asthma, and atherosclerosis. Inflammation and airway remodeling in asthma and COPD result in subepithelial fibrosis that is characterized by the deposition of interstitial collagens and fibronectin. The progression of atherosclerosis is also accompanied by an increased production of interstitial collagens in the intima. As shown by reverse transcription-PCR and immunoblotting, infection of human fibroblasts and smooth muscle cells by C. pneumoniae TW-183 downregulated the expression of type I and III collagen and fibronectin, whereas the level of type IV collagen remained unchanged. Conditioned medium from infected fibroblasts as well as epithelial WISH cells also reduced the expression of interstitial collagens and fibronectin in uninfected cells. In experiments using blocking antibodies, beta interferon was found to contribute to the inhibitory effects of conditioned medium collected from infected fibroblasts. In contrast, downregulation of matrix protein expression by conditioned medium from epithelial cells was caused by interleukin-1alpha, which was not secreted from fibroblasts following chlamydial infection. C. pneumoniae-mediated inhibition of collagen and fibronectin expression was diminished following transfection of fibroblasts with specific small interfering RNA targeting the transcription factor CCAAT/enhancer-binding protein beta. The downregulation of interstitial collagens and fibronectin by the Chlamydia-induced host cell cytokine response may modulate tissue remodeling processes in airway diseases. In atherosclerosis the inhibition of collagen synthesis by C. pneumoniae infection may promote plaque vulnerability, thereby increasing the risk of plaque rupture.

poly(I:C) and LPS induce distinct IRF3 and NF-kappaB signaling during type-I IFN and TNF responses in human macrophages

Macrophages play major roles in the onset of immune responses and inflammation by inducing a variety of cytokines such as TNF and IFN-beta. The pathogen-associated molecular pattern, polyinosinic-polycytidylic acid [poly(I:C)], and LPS were used to study type-I IFN and TNF responses in human macrophages. Additionally, activation of the key signaling pathways, IFN-regulatory factor 3 (IRF3) and NF-kappaB, were studied. We found that TNF production occurred rapidly after LPS stimulation. LPS induced a strong IFN-beta mRNA response within a short time-frame, which subsided at 8 h. The IFN-stimulated genes (ISGs), ISG56 and IFN-inducible protein 10, were strongly induced by LPS. These responses were associated with NF-kappaB and IRF3 activation, as shown by IRF3 dimerization and by nuclear translocation assays. poly(I:C), on the other hand, induced a strong and long-lasting (>12 h) IFN-beta mRNA and protein response, particularly when transfected, whereas only a protracted TNF response was observed when poly(I:C) was transfected. However, these responses were induced in the absence of detectable IRF3 and NF-kappaB signaling. Thus, in human macrophages, poly(I:C) treatment induces a distinct cytokine response when compared with murine macrophages. Additionally, a robust IFN-beta response can be induced in the absence of detectable IRF3 activation.

Suicide gene and cytokines combined nonviral gene therapy for spontaneous canine melanoma

Canine spontaneous melanoma is a highly aggressive tumor resistant to current therapies. We evaluated the safety, efficacy and antitumor effects of direct intratumor injections of lipoplexes encoding herpes simplex thymidine kinase coadministrated with ganciclovir, and irradiated transgenic xenogeneic cells secreting 20-30 mug day(-1) of human granulocyte-macrophage colony-stimulating factor and interleukin-2. Toxicity was minimal or absent in all patients. This combined treatment (CT) induced tumor regression and a pronounced immune cell infiltration. The objective responses (47%: 21/45) averaged 80% of tumor mass loss. Local CT also induced systemic antitumor response evidenced by complete remission of one pulmonary metastasis and by the significantly higher percentage of metastasis-free patients (76: 34/45)) until the study ending compared to untreated (UC: 29%, 5/17), surgery-treated (CX: 48%, 11/23) or suicide gene-treated controls (SG: 56%, 9/16) (Fisher's exact test). CT significantly improved median survival time: 160 (57-509) days compared to UC (69 (10-169)), CX (82 (43-216)) or SG (94 (46-159)). CT also increased (P<0.00001, Kaplan-Meier analysis) metastasis-free survival: >509 (57-509) days with respect to UC: 41 (10-169), CX: 133 (43-216) and SG: >159 (41-159). Therefore, CT controlled tumor growth by delaying or preventing distant metastasis, thereby significantly extending survival and recovering the quality of life.

Vaccination with mRNAs encoding tumor-associated antigens and granulocyte-macrophage colony-stimulating factor efficiently primes CTL responses, but is insufficient to overcome tolerance to a model tumor/self antigen

Immunization of mice with dendritic cells transfected ex vivo with tumor-associated antigen (TAA)-encoding mRNA primes cytotoxic T lymphocytes (CTL) that mediate tumor rejection. Here we investigated whether direct injection of TAA mRNA, encapsulated in cationic liposomes, could function similarly as cancer immunotherapy. Intradermal and intravenous injection of ovalbumin (OVA) mRNA generated specific CTL activity and inhibited the growth of OVA-expressing tumors. Vaccination studies with DNA have demonstrated that co-administration of antigen (Ag)- and cytokine-encoding plasmids potentiate the T cell response; in analogous fashion, the inclusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA enhanced OVA-specific cytotoxicity. The ability of this GM-CSF-augmented mRNA vaccine to treat an established spontaneous tumor was evaluated in the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) mouse, using the SV40 large T Ag (TAg) as a model tumor/self Ag. Repeated vaccination elicited vigorous TAg-specific CTL activity in nontransgenic mice, but tumor-bearing TRAMP mice remained tolerant. Adoptive transfer of naïve splenocytes into TRAMP mice prior to the first vaccination restored TAg reactivity, and slowed tumor progression. The data from this study suggests that vaccination with TAA mRNA is a simple and effective means of priming antitumor CTL, and that immunogenicity of the vaccine can be augmented by co-delivery of GM-CSF mRNA. Nonetheless, limitations of such vaccines in overcoming tolerance to tumor/self Ag may mandate prior or simultaneous reconstitution of the autoreactive T cell repertoire for this form of immunization to be effective.

Induction of interferon synthesis by the PKR-inhibitory VA RNAs of adenoviruses

In virus-infected cells, double-stranded RNA (dsRNA) activates the transcription factor interferon (IFN) regulatory factor-3 (IRF-3), which stimulates type I IFN (IFN-alpha/beta) gene expression. In addition, dsRNA activates the enzyme RNA-activated protein kinase (PKR), which phosphorylates the eukaryotic initiation factor 2alpha (eIF2beta), thereby inhibiting mRNA translation. Adenoviruses express highly structured RNA molecules termed VA RNAs (VA(I)/VA(II)) known to specifically inhibit PKR. As PKR impairs expression from transfected cDNA constructs, plasmids encoding VA RNAs are widely used as enhancers of transgene expression. Here, we describe induction of IFN synthesis as a novel feature of VA RNAs. Transfection of a VA(I)/VA(II)-expressing plasmid was found to induce type I IFN production, resulting in activation of IFN-dependent genes, such as IFN-stimulated gene 56 (ISG56) or MxA, and the establishment of an antiviral state in transfected cells. Curiously, VA RNAs did not activate IRF-3, suggesting an alternative pathway of IFN induction. These data may be considered when using genetically modified adenoviruses as therapeutic agents and suggest caution in choosing VA RNA constructs as a means to increase expression of a gene of interest.

Type I interferons potently suppress gene expression following gene delivery using liposome(-)DNA complexes

Gene delivery by intravenous injection of cationic liposome-DNA complexes (LDC) can generate efficient transgene expression in the lungs and other organs, but the duration of expression is typically short. Previous studies have suggested a major role for interferon-gamma (IFN-gamma) and TNF in this process. However, plasmid DNA is also capable of eliciting production of type I IFNs. Therefore, we assessed the ability of LDC to elicit production of type I IFNs in vivo and assessed the effects of type I IFNs on suppression of transgene expression following in vivo gene delivery with LDC. Injection of LDC was found to induce production of high levels of both IFN-alpha and IFN-beta in vivo. Moreover, the levels of transgene expression following in vivo gene delivery were markedly increased in mice lacking functional type I IFN receptor genes, compared to wild-type mice or mice lacking IFN-gamma or TNF receptors. Addition of recombinant IFN-alpha and IFN-beta inhibited transgene expression by in vitro-transfected endothelial cells, and incubation of macrophages with LDC in vitro triggered production of both IFN-alpha and IFN-beta. Therefore, type I IFNs appear to play a key role in suppressing transgene expression in vivo following systemic nonviral gene delivery using LDC.

Absence of non-specific effects of RNA interference triggered by long double-stranded RNA in mouse oocytes

RNA interference (RNAi) is a conserved eukaryotic mechanism by which double-stranded RNA (dsRNA) triggers the sequence-specific degradation of homologous mRNAs. Recent concerns have arisen in mammalian systems about off-target effects of RNAi, as well as an interferon response. Most mammalian cells respond to long dsRNAs by inducing an antiviral response mediated by interferon that leads to general inhibition of protein synthesis and nonspecific degradation of mRNAs. Moreover, recent reports demonstrate that under certain conditions, short interfering RNAs (siRNAs, 21-25 bp) may activate the interferon system. Mouse oocytes and preimplantation embryos apparently lack this response, as potent and specific inhibition of gene expression triggered by long dsRNA is observed in these cells. In the present study, we analyzed the global pattern of gene expression by microarray analysis in transgenic mouse oocytes expressing long dsRNA and find no evidence of off-targeting. We also report that genes involved in the interferon response pathway are not expressed in mouse oocytes, even after exposure for an extended period of time to long dsRNA.

Crystal Structure of the Interferon-induced Ubiquitin-like Protein ISG15

The biological effects of the ISG15 protein arise in part from its conjugation to cellular targets as a primary response to interferon-alpha/beta induction and other markers of viral or parasitic infection. Recombinant full-length ISG15 has been produced for the first time in high yield by mutating Cys78 to stabilize the protein and by cloning in a C-terminal arginine cap to protect the C terminus against proteolytic inactivation. The cap is subsequently removed with carboxypeptidase B to yield mature biologically active ISG15 capable of stoichiometric ATP-dependent thiolester formation with its human UbE1L activating enzyme. The three-dimensional structure of recombinant ISG15C78S was determined at 2.4-A resolution. The ISG15 structure comprises two beta-grasp folds having main chain root mean square deviation (r.m.s.d.) values from ubiquitin of 1.7 A (N-terminal) and 1.0 A (C-terminal). The beta-grasp domains pack across two conserved 3(10) helices to bury 627 A2 that accounts for 7% of the total solvent-accessible surface area. The distribution of ISG15 surface charge forms a ridge of negative charge extending nearly the full-length of the molecule. Additionally, the N-terminal domain contains an apolar region comprising almost half its solvent accessible surface. The C-terminal domain of ISG15 was superimposed on the structure of Nedd8 (r.m.s.d. = 0.84 A) bound to its AppBp1-Uba3 activating enzyme to model ISG15 binding to UbE1L. The docking model predicts several key side-chain interactions that presumably define the specificity between the ubiquitin and ISG15 ligation pathways to maintain functional integrity of their signaling.

Inhibitory effects associated with use of modified Photinus pyralis and Renilla reniformis luciferase vectors in dual reporter assays and implications for analysis of ISGs

Luciferase reporter constructs are widely used for analysis of gene regulation when characterizing promoter and enhancer elements. We report that the recently developed codon-modified Renilla luciferase construct included as an internal standard for cotransfection must be used with great caution with respect to the amount of DNA transfected. Also, the dual-luciferase reporter vectors encoding Photinus pyralis firefly or Renilla reniformis luciferase showed a linear increase in dose-response with increasing amounts of transfected DNA, but at higher levels of transfected DNA, a reduction in expressed levels of luciferase activity resulted. In addition, treatment with type I interferon (IFN) was found to significantly reduce levels of P. pyralis firefly and Renilla luciferase activity. In contrast, cells transfected with a green fluorescent protein (GFP) reporter construct showed no significant IFN-associated change. The reduction in luciferase activity resulting from IFN treatment was not due to IFN-mediated cytotoxicity, as no change in cellular propidium iodide (PI) staining was observed by flow cytometry. IFN treatment did not alter the levels of firefly luciferase activity in cell culture supernatants or the luciferase mRNA levels determined by quantitative real-time RT-PCR analysis. Based on these results, it is probable that the IFN-induced reduction in levels of luciferase activity detected in reporter assays occurs via a posttranscriptional mechanism. Thus, it is important to be aware of these complications when using luciferase reporter systems in general or for analyzing cytokine-mediated responsive regulation of target genes, particularly by the type I IFNs.

Toxicity of Cationic Lipid‐DNA Complexes

As with any conventional drug, the body's response to cationic lipid-DNA complexes is highly dependent on both the dose administered and the route of delivery. At relatively low doses there is little to no effect on organ function or tissue architecture, but at higher doses, acute inflammation and tissue damage can occur that is sometimes quite profound. Of the two most common routes of delivery, intravenous (IV) or intrapulmonary, IV administration tends to cause more severe adverse effects and can be lethal at higher doses of complex. Both routes activate an innate immune response that includes the induction of proinflammatory cytokines and immune cell activation, a major portion of which has been attributed to the presence of immunostimulatory CpG motifs within the plasmid DNA vector. Removing CpGs from the plasmid vector reduces several, but not all of the acute inflammatory responses to cationic lipid-DNA complexes. Therefore, other strategies are required to improve the therapeutic potential of these vectors, such as transient immune suppression, aerosolization of the complex, and novel formulations that have increased efficiency of transduction and decreased interaction with immune cells.

Conditional expression of IFN-alpha and IFN-gamma activated by HBV as genetic therapy for hepatitis B

Chronic infection with hepatitis B virus (HBV) has potentially devastating consequences and is very difficult to treat. Therapy with recombinant interferons (IFN), especially IFN-alpha, may be effective. The blood IFN-alpha levels that are needed to maintain therapeutic IFN-alpha levels in the liver, however, often cause severe side effects. Gene delivery to the liver may provide a solution. Using a long-term expression construct could provide the desired levels of IFN locally without the need to maintain potentially problematic blood levels. Recombinant, Tag-deleted SV40-derived vectors transduce hepatocytes efficiently and provide permanent transgene expression. We designed an expression construct that was effective against HBV and whose activity was limited to HBV-infected cells. To do this, we exploited the ability of HBV X protein to activate NF-kappaB and, via NF-kappaB, to activate promoter activity of HIV long terminal repeat (LTR) in hepatocytes. Using HIVLTR as a conditional promoter upstream of human and murine IFN-alpha and IFN-gamma cDNAs, rSV40 vectors were used to test the responsiveness of IFN to HBV and the ability of these IFNs to inhibit HBV transcripts and protein production and to activate IFN signaling in neighboring untransduced cells. We found that in hepatocyte cell lines and in primary hepatocytes, HBV activated the promoter activity of the HIVLTR via NF-kappaB. When whole HBV genome was delivered to cells by transfection to simulate HBV infection, IFN expression was activated, IFNs were produced and secreted, and they protected cells from HBV. Levels of IFN proteins that were secreted in this context were comparable to targeted blood levels needed to control chronic hepatitis viral infection. Further, IFNs that were elicited and secreted in this manner were able to activate IFN-induced signaling pathways in neighboring, untransduced cells and so were likely to provide protection even to cells that the rSV40 vector did not transduce. Gene delivery using such rSV40 vectors expressing IFNs conditionally in response to HBV may be an attractive therapeutic option for the treatment of chronic hepatitis B.

Quantitative multiplex real-time PCR for the sensitive detection of interferon beta gene induction and viral suppression of interferon beta expression

Interferon-beta (IFN-beta) protein and activity can be detected by enzyme immunoassays and biological assays. However, precise quantification of low IFN-beta mRNA concentrations, which is advantageous for investigating IFN-beta gene expression in small tissue samples or during the early stage of a virus infection, remains a challenge. Therefore, we established a quantitative real-time PCR (qPCR) for IFN-beta and the housekeeping gene porphobilinogen deanimase (PBGD) in separated assays as well as in a multiplex procedure. Sensitivity for both the templates was less than 20 copies with an intra- and interassay variability of less than 5%. IFN-beta qPCR was utilized to optimize IFN-beta induction with dsRNA polyinosic-polycytidylic acid (poly I:C), delivered by a liposomal transfection agent for reproducible but low, non-cell-toxic IFN-beta concentrations. For studying coxsackievirus B3 (CVB3) interference with IFN-beta expression, CVB3 infected fibroblasts were induced with poly I:C. A significant reduction of IFN-beta mRNA but not PBGD mRNA was demonstrated 5 h after CVB3 infection, indicating a specific inhibition of IFN-beta expression by CVB3 on the mRNA level, in addition to previously reported effects on the translation/post-translation level. In conclusion, sensitive IFN-beta/PBGD multiplex qPCR proved to be a useful tool to study viral interaction with IFN-beta expression.

Innate cellular response to virus particle entry requires IRF3 but not virus replication

Mammalian cells respond to virus infections by eliciting both innate and adaptive immune responses. One of the most effective innate antiviral responses is the production of alpha/beta interferon and the subsequent induction of interferon-stimulated genes (ISGs), whose products collectively limit virus replication and spread. Following viral infection, interferon is produced in a biphasic fashion that involves a number of transcription factors, including the interferon regulatory factors (IRFs) 1, 3, 7, and 9. In addition, virus infection has been shown to directly induce ISGs in the absence of prior interferon production through the activation of IRF3. This process is believed to require virus replication and results in IRF3 hyperphosphorylation, nuclear localization, and proteasome-mediated degradation. Previously, we and others demonstrated that herpes simplex virus type 1 (HSV-1) induces ISGs and an antiviral response in fibroblasts in the absence of both interferon production and virus replication. In this report, we show that the entry of enveloped virus particles from diverse virus families elicits a similar innate response. This process requires IRF3, but not IRF1, IRF7, or IRF9. Following virus replication, the large DNA viruses HSV-1 and vaccinia virus effectively inhibit ISG mRNA accumulation, whereas the small RNA viruses Newcastle disease virus, Sendai virus, and vesicular stomatitis virus do not. In addition, we found that IRF3 hyperphosphorylation and degradation do not correlate with ISG and antiviral state induction but instead serve as a hallmark of productive virus replication, particularly following a high-multiplicity infection. Collectively, these data suggest that virus entry triggers an innate antiviral response mediated by IRF3 and that subsequent virus replication results in posttranslational modification of IRF3, such as hyperphosphorylation, depending on the nature of the incoming virus.

Role of interferon-stimulated gene factor 3gamma and beta interferon in HLA class I enhancement in synovial fibroblasts upon infection with Chlamydia trachomatis

Chlamydia trachomatis infection can cause reactive arthritis that is associated with the persistence of chlamydial organisms in the joint. Fibroblasts of the synovial membrane represent host cells for Chlamydia during articular infection. In this study we investigated the expression of HLA class I molecules in synovial fibroblasts following infection with C. trachomatis D. The expression of HLA class I heavy chain (HLA-I) was up-regulated in infected cultures as shown by reverse transcription-PCR and immunoblotting. The increase in cell surface expression of HLA-I and beta(2) microglobulin on infected fibroblasts was demonstrated by flow cytometric analysis. Suppression of enhanced production of interferon-stimulated gene factor 3gamma (ISGF3gamma) in infected cell cultures by antisense oligonucleotide treatment reduced the level of HLA-I. Blocking antibodies to beta interferon (IFN-beta) inhibited the Chlamydia-induced enhancement of both ISGF3gamma and HLA-I. These findings show that the up-regulation of HLA-I in synovial fibroblasts infected with C. trachomatis is caused by the induction of IFN-beta, which in turn stimulates the synthesis of ISGF3gamma, a transcription factor participating in the regulation of the HLA-I gene. The IFN-beta-mediated expression of HLA-I on Chlamydia-infected cells may be a regulatory factor in the immune response in chlamydial infections.

Molecular cloning of the fish interferon stimulated gene, 15 kDa (ISG15) orthologue: a ubiquitin-like gene induced by nephrotoxic damage

In mammals, the response to nephrotoxicant-induced renal injury is limited to repair of the proximal tubule by surviving epithelial cells. In contrast, bony fish are capable of both repair, and de novo production of nephrons in response to renal damage. Importantly, toxicant-induced nephron neogenesis in goldfish (Carassius auratus) parallels nephron development in the mammalian embryo, providing a vertebrate model for kidney development. We utilized this model system to identify genes induced by the renal toxicant, gentamicin, that may function in nephron neogenesis. A novel ubiquitin-like (UBL) gene, 40.1, was identified by differential display analysis of control and gentamicin-treated goldfish kidney. 40.1 was induced dramatically 3-7 days following a sublethal dose of gentamicin, and returned to basal level by 14 days post-treatment. The induction of 40.1 coincided with early renal injury in the proximal tubules of gentamicin-injected fish; however, expression was not restricted to the kidney, suggesting that 40.1 induction may be a more general response to cell injury. Sequence analysis revealed that 40.1 contains tandem UBL domains, and shares homology with ISG15, a 15 kD interferon-(IFN) stimulated UBL found in mammals. Analysis of the genome database for the pufferfish, Fugu rubrides, identified a goldfish ISG15 (gfISG15) homologue with an IFN-stimulated response element in the promoter region, providing further evidence that gfISG15 is the true teleost ISG15 orthologue. Zebrafish and catfish ISG15 genes were subsequently identified by sequence analysis. Consistent with its predicted function as a UBL, gfISG15 formed conjugates with cellular proteins in vitro and in transient transfections. Similar to the induction of mammalian ISG15 by microbial challenge, gfISG15 was induced in the spleen of mycobacteria-infected fish. These studies identified the first teleost ISG15 orthologue. The induction of gfISG15 as an early genetic event in response to a renal toxicant, and its conserved, stress-associated, expression in higher vertebrates suggests that ISG15 is an important component of the host response to diverse stress stimuli.

Cationic liposome-mediated enhanced generation of human HLA-restricted RSV-specific CD8+ CTL+

Generation of human CD8+ cytotoxic T-lymphocyte (CTL) activity against respiratory syncytial virus (RSV) using peripheral blood leukocytes (PBL) in vitro is inefficient. Lipofectamine, a polycationic liposome, previously shown to enhance the transfection efficiency of DNA in cells, was evaluated for enhancing RSV CTL activity. Stimulator cells were prepared by infecting human PBL with RSV with or without Lipofectamine for 3 hr and then transferred to responder cells. After 8 days of incubation, CTL lysis of autologous target cells infected with RSV (also treated with Lipofectamine) was determined in a 4-hr 5'chromium release assay. Lipofectamine treatment significantly enhanced HLA-restricted RSV-specific CD8+ CTL activity (up to sevenfold, P < 0.05-0.001). Lipofectamine treatment also enhanced cell surface RSV antigen expression and increased the frequencies of HLA-A,B,C+/RSV+ and HLA-DR+/RSV+ leukocytes as demonstrated by flow cytometry. These results demonstrate the usefulness of cationic liposomes in augmenting cell surface antigen expression and increasing the efficiency of generation of human RSV-specific CD8+ CTL activity.

Lipofection of early passages of cell cultures derived from murine adenocarcinomas: in vitro and ex vivo testing of the thymidine kinase/ganciclovir system

Early passages of cultured cells derived from four spontaneous Balb/c murine adenocarcinomas were used to explore the feasibility of a nonviral HSVtk-based suicide gene therapy system. After lipofection with pCMVtk, the transiently HSVtk expressing P07 (lung), M3, M05, and M38 (mammary gland) cells were, respectively, about 130-, 30-, 120-, and 170-fold more sensitive to ganciclovir (GCV) in vitro than their respective controls. Eighty percent of Balb/c mice subcutaneously inoculated with ex vivo pCMVtk-lipofected P07 cells, followed by intraperitoneal GCV injection for 7 days, displayed a complete inhibition of tumor growth for over 70 days. Control animals started to display tumors 13 days after inoculation. We present evidence showing that early passages of cultured tumor cells can efficiently express lipofected genes and that they are sensitive to the lipoplex-mediated HSVtk/GCV system.

Interferon-beta induction by Chlamydia pneumoniae in human smooth muscle cells

Clinical studies have suggested a causal or contributory role of Chlamydia pneumoniae infection in asthma and atherosclerosis. The activation of synthetic functions of smooth muscle cells (SMC) including the production of cytokines and growth factors plays a major role in the formation of fibrous atherosclerotic plaques as well as in structural remodelling of the airway wall in chronic asthma. In this study we demonstrated that C. pneumoniae induced the production of low levels of interferon (IFN)-beta in bronchial and vascular SMC when infected cells were treated with tumour necrosis factor-alpha (TNF-alpha). IFN-beta production was analysed by reverse transcription-PCR and enzyme-linked immunosorbent assay. The upregulation of IFN-beta was paralleled by an increase in mRNA levels of interferon regulatory factor-1 and interferon-stimulated gene factor 3gamma, two transcription factors activating the expression of the IFN-beta gene. In addition, C. pneumoniae infection enhanced the mRNA level of indoleamine 2,3-dioxygenase, an IFN-inducible factor mediating the restriction of intracellular chlamydial growth, in TNF-alpha-stimulated SMC. C. pneumoniae-induced IFN-beta production by SMC may modulate inflammation and tissue remodelling during respiratory and vascular infection.

Recent progress in gene delivery using non-viral transfer complexes

The delivery of genetic material into cells is a field that is expanding very rapidly. Non-viral delivery methods, especially ones that focus on the use of chemical agents complexed with genetic material, are the focus of this mini-review. More-recent uses of known transfection agents such as poly(ethylenimine), poly(L-lysine), and various liposomes are discussed, and some novel approaches (both chemical and methodical) are reviewed as well. A very brief look at how non-viral gene delivery research is being aimed at the clinic is also included.

The immune response to ocular herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) is a prevalent microbial pathogen infecting 60% to 90% of the adult world population. The co-evolution of the virus with humans is due, in part, to adaptations that the virus has evolved to aid it in escaping immune surveillance, including the establishment of a latent infection in its human host. A latent infection allows the virus to remain in the host without inducing tissue pathology or eliciting an immune response. During the acute infection or reactivation of latent virus, the immune response is significant, which can ultimately result in corneal blindness or fatal sporadic encephalitis. In fact, HSV-1 is one of the leading causes of infectious corneal blindness in the world as a result of chronic episodes of viral reactivation leading to stromal keratitis and scarring. Significant inroads have been made in identifying key immune mediators that control ocular HSV-1 infection and potentially viral reactivation. Likewise, viral mechanisms associated with immune evasion have also been identified and will be discussed. Lastly, novel therapeutic strategies that are currently under development show promise and will be included in this review. Most investigators have taken full advantage of the murine host as a viable working in vivo model of HSV-1 due to the sensitivity and susceptibility to viral infection, ease of manipulation, and a multitude of developed probes to study changes at the cellular and molecular levels. Therefore, comments in this review will primarily be restricted to those observations pertaining to the mouse model and the assumption (however great) that similar events occur in the human condition.

Poly(ethylenimine)-mediated gene delivery affects endothelial cell function and viability

Poly(ethylenimine) (PEI) was used to transfect the endothelial cell line EA.hy 926, and the secreted levels of three gene products, tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), and von Willebrand Factor (vWF), were assessed via ELISA. We found that the levels of these gene products in cell supernatants increased by factors up to 16.3 (tPA), 8.3 (PAI-1), or 6.7 (vWF) times the levels recorded for untreated cells, and roughly correlated with the percentage of cells that expressed the reporter plasmid. Transfections carried out using promotorless constructs of the same reporter plasmid also yielded increases in tPA, PAI-1, and vWF to similar extents. Additionally, data regarding cell viability were gathered and found to inversely relate to both the effectiveness of the PEI used for transfection and the secreted levels of the three mentioned products. There appeared to be two distinct types of cell death, resulting from the use of either free PEI (which acts within 2 h) or PEI/DNA complexes (which cause death 7-9 h after transfection). Cells were also transfected by poly(L-lysine) and liposomal carriers, and increases in secreted tPA similar to those seen with PEI-mediated transfection were observed for positively transfected cells. The results of these investigations indicate that non-viral gene delivery can induce a state of endothelial cell dysfunction, and that PEI-mediated transfection can lead to two distinct types of cell death.

Different subcellular localizations for the related interferon-induced GTPases, MuGBP-1 and MuGBP-2: implications for different functions?

The guanylate-binding proteins (GBPs) are a family of 65-67-kDa proteins induced by both type I and type II interferons (IFN). Members of the GBP family of GTPases are among the most abundant IFN-gamma-induced proteins. GBPs contain an unusual GTP binding site, which is consistent with GBP hydrolysis of GTP to both GDP and GMP. In addition, six of the eight known GBPs have a carboxy-terminal CaaX motif for the addition of isoprenyl lipids. Despite their abundance, however, little is known about the biologic function or cellular location of GBPs. We report here on studies to localize both a newly identified murine GBP (MuGBP-2) and its closely related family member, MuGBP-1. In both IFN-treated macrophages and fibroblasts, MuGBP-2 is found in both a granular distribution throughout the cytoplasm and localized to vesicle populations of heterogeneous sizes. The localization of MuGBP-2 to vesicles is dependent on its isoprenylation. Despite a high degree of sequence identity and the presence of an identical CaaX sequence, MuGBP-1 has a very homogeneous cytoplasmic distribution and fails to localize to intracellular vesicles. The different intracellular distribution of these two closely related family members suggests differential function(s).

Inducible expression of filaggrin increases keratinocyte susceptibility to apoptotic cell death

Filaggrin is an intermediate filament associated protein that aids the packing of keratin filaments during terminal differentiation of keratinocytes. Premature aggregation of keratin filaments is prevented by filaggrin expression as the inactive precursor, profilaggrin, which is localized in keratohyalin granules in vivo. We have previously shown that filaggrin constructs, when transiently transfected into epithelial cells, lead to a collapsed keratin cytoskeletal network and dysmorphic nuclei with features of apoptosis. The apparent transfection rate is low with filaggrin constructs, supporting their disruptive role but hindering further study. To bypass this problem, we generated stable keratinocyte cell lines that express mature human filaggrin using a tetracycline-inducible promoter system. We found that cell lines expressing filaggrin, but not control cell lines, exhibited increased sensitivity to multiple apoptotic stimuli as measured by morphologic and biochemical criteria. None of the cell lines showed an increase in endogenous expression of filaggrin in response to the same stimuli. Filaggrin expression alone was insufficient to induce apoptosis in these keratinocyte cell lines. We conclude that filaggrin, due to its keratin binding ability, primes cells for apoptosis. Because filaggrin is expressed at a level of the epidermis where keratinocytes are in transition between the nucleated granular and the anucleate cornified layers, we hypothesize that filaggrin aids in the terminal differentiation process by facilitating apoptotic machinery.

The antiviral enzymes PKR and RNase L suppress gene expression from viral and non-viral based vectors

Expression of transfected genes is shown to be suppressed by two intracellular enzymes, RNase L and protein kinase PKR, which function in interferon-treated cells to restrict viral replication. RNase L(-/-) or PKR(-/-) murine embryonic fibroblasts produced enhanced levels of protein from transfected genes compared with wild-type cells. Increased expression of exogenous genes in RNase L(-/-) cells correlated with elevated levels of mRNA and thus appeared to be due to enhanced mRNA stability. Plasmid encoding adenovirus VA RNAs was able to further enhance accumulation of the exogenous gene transcript and protein, even in cells lacking PKR. In contrast to the increased expression of transfected genes in cells lacking RNase L or PKR, expression of endogenous host genes was unaffected by the absence of these enzymes. In addition, a dominant-negative PKR mutant improved expression from a conventional plasmid vector and from a Semliki Forest virus derived, self-replicating vector. These results indicate that viral infections and transfections produce similar stress responses in mammalian cells and suggest strategies for selectively increasing expression of exogenous genes.