Tumor necrosis factor alpha plays a central role in immune-mediated clearance of adenoviral vectors

Tumor necrosis factor-α polymorphism and risk of primary nephrotic syndrome: A case-control study and meta-analysis

BACKGROUND

The current study aims to explore the relationship between tumor necrosis factor-α (TNF-α) polymorphism and the risk of primary nephrotic syndrome (PNS).

METHODS

A total of 250 PNS patients were selected for this study, as well as 300 volunteers serving as the control group. TNF-α polymorphism were assessed using the polymerase chain reaction-restriction fragment length polymorphism method. In addition, a meta-analysis was conducted to analyze previously published literature on this topic.

RESULTS

No significant differences were observed in the genotypes frequency or alleles frequency among the study populations. Meta-analysis results revealed a positive association between TNF-α rs1800629 polymorphism and allele contrast in African populations (p = 0), homozygote comparison (p = .007), heterozygote comparison (p = .026), recessive genetic model (p = .011), and dominant genetic model (p = .000).

CONCLUSIONS

TNF-α rs1800629 polymorphism does not appear to confer any increased risk for PNS.

Engineering chitosan nano-cocktail containing iron oxide and ceria: A two-in-one approach for treatment of inflammatory diseases and tracking of material delivery

In this study, modular two-in-one nano-cocktails were synthesised to provide treatment of inflammatory diseases and also enable tracking of their delivery to the disease sites. Chitosan nano-cocktails loaded with treatment module (cerium oxide nanoparticles) and imaging module (iron oxide nanoparticles) were synthesised by electrostatic self-assembly (Chit-IOCO) and ionic gelation method (Chit-TPP-IOCO), respectively. Their MRI capability, anti-inflammatory and anti-fibrosis ability were investigated. Results demonstrated that Chit-IOCO significantly reduced the expression of TNF-α and COX-2, while Chit-TPP-IOCO reduced IL-6 in the LPS-stimulated macrophages RAW264.7. Cytotoxicity studies showed that the nano-cocktails inhibited the proliferation of macrophages. Additionally, Chit-IOCO exhibited higher in vitro MRI relaxivity than Chit-TPP-IOCO, indicating that Chit-IOCO is a better MRI contrast agent in macrophages. It was possible to track the delivery of Chit-IOCO to the inflamed livers of CCl₄-treated C57BL/6 mice, demonstrated by a shortened T₂^⁎ relaxation time of the livers after injecting Chit-IOCO into mice. In vivo anti-inflammatory and blood tests demonstrated that Chit-IOCO reduced inflammation-related proteins (TNF-a, iNOS and Cox-2) and bilirubin in CCl₄ treated C57BL/6. Histology images indicated that the nano-cocktails at the treatment doses did not affect the organs of the mice. Importantly, the nano-cocktail reduced fibrosis of CCl₄-treated mouse liver. This is the first reported data on the anti-inflammation and anti-fibrosis efficacy of Chit-IOCO in C57BL/6 mouse liver inflammation model. Overall, Chit-IOCO nanoparticles have shown great potential in MR imaging/detecting and treating/therapeutic capabilities for inflammatory diseases.

Consensus M2e peptide conjugated to gold nanoparticles confers protection against H1N1, H3N2 and H5N1 influenza A viruses

The extracellular domain of influenza A ion channel membrane matrix protein 2 (M2e) is considered to be a potential candidate to develop a universal influenza A vaccine. However poor immunogenicity of M2e presents a significant roadblock. We have developed a vaccine formulation comprising of the consensus M2e peptide conjugated to gold nanoparticles (AuNPs) with CpG as a soluble adjuvant (AuNP-M2e + sCpG). We demonstrate that intranasal delivery of AuNP-M2e + sCpG in mice induces lung B cell activation and robust serum anti-M2e immunoglobulin G (IgG) response, with stimulation of both IgG1 and IgG2a subtypes. Using Madin-Darby canine kidney (MDCK) cells infected with A/California/04/2009 (H1N1pdm) pandemic strain, or A/Victoria/3/75 (H3N2), or the highly pathogenic avian influenza virus A/Vietnam/1203/2004 (H5N1) as immunosorbants we further show that the antibodies generated are also capable of binding to the homotetrameric form of M2 expressed on infected cells. Lethal challenge of vaccinated mice with A/California/04/2009 (H1N1pdm) pandemic strain, A/Victoria/3/75 (H3N2), and the highly pathogenic avian influenza virus A/Vietnam/1203/2004 (H5N1) led to 100%, 92%, and 100% protection, respectively. Overall, this study helps to lay the foundation of a potential universal influenza A vaccine.

Unabated adenovirus replication following activation of the cGAS/STING-dependent antiviral response in human cells

The cGAS/STING DNA sensing complex has recently been established as a predominant pathogen recognition receptor (PRR) for DNA-directed type I interferon (IFN) innate immune activation. Using replication-defective adenovirus vectors and replication-competent wild-type adenovirus, we have modeled the influence of the cGAS/STING cascade in permissive human cell lines (A549, HeLa, ARPE19, and THP1). Wild-type adenovirus induced efficient early activation of the cGAS/STING cascade in a cell-specific manner. In all responsive cell lines, cGAS/STING short hairpin RNA (shRNA) knockdown resulted in a loss of TBK1 and interferon response factor 3 (IRF3) activation, a lack of beta interferon transcript induction, loss of interferon-dependent STAT1 activation, and diminished induction of interferon-stimulated genes (ISGs). Adenoviruses that infect through the coxsackievirus-adenovirus receptor (CAR) (Ad2 and Ad5) and the CD46 (Ad35) and desmoglein-2 (Ad7) viral receptors all induce the cGAS/STING/TBK1/IRF3 cascade. The magnitude of the IRF3/IFN/ISG antiviral response was strongly influenced by serotype, with Ad35>Ad7>Ad2. For each serotype, no enhancement of viral DNA replication or virus production occurred in cGAS or STING shRNA-targeted cell line pools. We found no replication advantage in permissive cell lines that do not trigger the cGAS/STING cascade following infection. The cGAS/STING/TBK1/IRF3 cascade was not a direct target of viral antihost strategies, and we found no evidence that Ad stimulation of the cGAS/STING DNA response had an impact on viral replication efficiency.

IMPORTANCE

This study shows for the first time that the cGAS DNA sensor directs a dominant IRF3/IFN/ISG antiviral response to adenovirus in human cell lines. Activation of cGAS occurs with viruses that infect through different high-affinity receptors (CAR, CD46, and desmoglein-2), and the magnitude of the cGAS/STING DNA response cascade is influenced by serotype-specific functions. Furthermore, activation of the cGAS cascade occurred in a cell-specific manner. Activation of the cGAS/STING response did not impact viral replication, and viral immune evasion strategies did not target the cGAS/STING/TBK1/IRF3 cascade. These studies provide novel insight into the early innate recognition response to adenovirus.

Peptide-based technologies to alter adenoviral vector tropism: ways and means for systemic treatment of cancer

Due to the fundamental progress in elucidating the molecular mechanisms of human diseases and the arrival of the post-genomic era, increasing numbers of therapeutic genes and cellular targets are available for gene therapy. Meanwhile, the most important challenge is to develop gene delivery vectors with high efficiency through target cell selectivity, in particular under in situ conditions. The most widely used vector system to transduce cells is based on adenovirus (Ad). Recent endeavors in the development of selective Ad vectors that target cells or tissues of interest and spare the alteration of all others have focused on the modification of the virus broad natural tropism. A popular way of Ad targeting is achieved by directing the vector towards distinct cellular receptors. Redirecting can be accomplished by linking custom-made peptides with specific affinity to cellular surface proteins via genetic integration, chemical coupling or bridging with dual-specific adapter molecules. Ideally, targeted vectors are incapable of entering cells via their native receptors. Such altered vectors offer new opportunities to delineate functional genomics in a natural environment and may enable efficient systemic therapeutic approaches. This review provides a summary of current state-of-the-art techniques to specifically target adenovirus-based gene delivery vectors.

Japonicone A antagonizes the activity of TNF-α by directly targeting this cytokine and selectively disrupting its interaction with TNF receptor-1

Anti-TNF biologics are effective therapies for various inflammatory diseases. Unfortunately, their clinical use is associated with an increased risk of infections. Selectively inhibiting TNF receptor-1 (TNFR1)-mediated signaling while preserving TNFR2 signaling may reduce inflammation yet maintain host immune response to pathogens. However, few small molecules that selectively target the TNF/TNFR system have been discovered. In the present study, we identified Japonicone A (Jap A), a nature compound derived from Inula japonica Thunb, as a novel TNF-α antagonist, as it reduced the TNF-α-mediated cytotoxicity on L929 cells and inhibited the binding of (125)I-labeled TNF-α to L929 cell surface. Furthermore, Jap A could directly bind to TNF-α rather than TNFR1 as determined by surface plasmon resonance. More importantly, Jap A could effectively inhibit the binding of TNF-α to TNFR1, while displaying only marginal inhibitory effects on that to TNFR2. Jap A also could block TNFR1-mediated signaling as it inhibited TNF-α-induced NF-κB activation in 293 cells. In addition, Jap A suppressed TNF-α-induced expressions of adhesion molecules (ICAM-1, VCAM-1) and chemokine (MCP-1) in the endothelial cells by blocking TNF-α-triggered multiple signaling pathways. Data from in vivo experiments demonstrated that Jap A protected mice from acute hepatitis induced by TNF-α/d-galactosamine, but did not compromise host antiviral immunity in adenovirus-infected mice. These results indicate that Jap A can directly target TNF-α, selectively disrupt its interaction with TNFR1, and antagonize its pro-inflammatory activities without compromising host defense against virus, thus emphasizing the potential of Jap A as an interesting lead compound for development of new anti-inflammatory drugs.

Tetradecylthioacetic acid modulates cardiac transcription in Atlantic salmon, Salmo salar L., suffering heart and skeletal muscle inflammation

Heart and skeletal muscle inflammation (HSMI) is a disease causing considerable mortality in farmed Atlantic salmon. We have previously reported that pre-feeding of tetradecylthioacetic acid (TTA) reduces the mortality during a natural outbreak of HSMI. In the present paper we show that in the cardiac ventricle, during HSMI infection, pre-feeding TTA increases the expression of the immune genes: TNFα, VCAM-1, IgM and CD8α. We also show that TTA increases the cardiosomatic index potentially by elevating cardiomyogenesis through activation of the cardiac transcription factors MEF2C and Nkx2.5. Using the recently published genomic sequence of a HSMI associated piscine reovirus (PRV), we could show that the PRV levels have no confounding effects on the mRNA expression of the investigated genes. The results suggest that TTA induced cardiac growth, together with an elevated cardiac recruitment of immune cells, which might lead to increased robustness during HSMI infection.

Persistence and the state of bovine and porcine adenoviral vector genomes in human and nonhuman cell lines

The state of vector genome in transduced cells influences the duration of transgene expression and can be a safety concern if it gets integrated randomly into the host genome. Although human adenovirus (Ad) serotype 5 (HAd5) mainly persists in a linear episomal form, information regarding the state of bovine Ad serotype 3 (BAd3) and porcine Ad serotype 3 (PAd3) vector genomes in human and nonhuman cells is currently unknown. To address this issue, MDA-MB-231 (human), MDBK (bovine), PK-15 (porcine), MT1A2 (mouse) and NIH-3T3 (mouse) cell lines were infected with replication-defective BAd3, PAd3 or HAd5 vectors carrying the green fluorescent protein (GFP) gene. The persistence and the state of vector genome were assessed by quantitative real-time PCR and Southern blot hybridization, respectively. Levels of transgene and Ad gene expressions were quantified using real-time RT-PCR. Persistence of BAd3 or PAd3 vectors was comparable to that of HAd5 vector. Only the linear episomal form of the vector genome was observed with each vector. In addition, expression levels of transgene as well as viral genes by all three vectors were comparable and correlated with their transduction levels in each cell type. These results indicate comparable biologic behavior of BAd3, PAd3 and HAd5 vectors in cell culture.

Active targeting and safety profile of PEG-modified adenovirus conjugated with herceptin

PEGylation of adenovirus (Ad) increases plasma retention and reduces immunogenicity, but decreases the accessibility of virus particles to target cells. We tested whether PEGylated Ad conjugated to Herceptin (Ad-PEG-HER) can be used to treat Her2/neu-positive cells in vitro and in vivo to demonstrate the therapeutic feasibility of this Ad formulation. Ad-PEG-HER transduced Her2/neu-overexpressing cancer cells through a specific interaction between Herceptin and Her2/neu. Ad-PEG-HER treatment resulted in higher plasma retention and lower neutralizing antibody and IL-6 production than naked Ad. This formulation was extended to generate a Her2/neu-targeted, PEGylated oncolytic Ad (DWP418-PEG-HER). DWP418-PEG-HER specifically killed Her2/neu-positive cells and performed better than non-targeted and naked Ad in vivo. DWP418-PEG-HER showed a 10(10)-fold increase in the liver to tumor biodistribution compared with naked Ad. Immunohistochemical staining confirmed accumulation of Ad E1A in tumors. These data suggest that targeted gene therapy with the PEGylated Ad conjugated with Herceptin might shed a light on its therapeutic application for metastatic cancer in the future.

Maturation-dependent licensing of naive T cells for rapid TNF production

The peripheral naïve T cell pool is comprised of a heterogeneous population of cells at various stages of development, which is a process that begins in the thymus and is completed after a post-thymic maturation phase in the periphery. One hallmark of naïve T cells in secondary lymphoid organs is their unique ability to produce TNF rapidly after activation and prior to acquiring other effector functions. To determine how maturation influences the licensing of naïve T cells to produce TNF, we compared cytokine profiles of CD4⁺ and CD8⁺ single positive (SP) thymocytes, recent thymic emigrants (RTEs) and mature-naïve (MN) T cells during TCR activation. SP thymocytes exhibited a poor ability to produce TNF when compared to splenic T cells despite expressing similar TCR levels and possessing comparable activation kinetics (upregulation of CD25 and CD69). Provision of optimal antigen presenting cells from the spleen did not fully enable SP thymocytes to produce TNF, suggesting an intrinsic defect in their ability to produce TNF efficiently. Using a thymocyte adoptive transfer model, we demonstrate that the ability of T cells to produce TNF increases progressively with time in the periphery as a function of their maturation state. RTEs that were identified in NG-BAC transgenic mice by the expression of GFP showed a significantly enhanced ability to express TNF relative to SP thymocytes but not to the extent of fully MN T cells. Together, these findings suggest that TNF expression by naïve T cells is regulated via a gradual licensing process that requires functional maturation in peripheral lymphoid organs.

Infectious pulmonary complications in patients treated with anti-TNF-alpha monoclonal antibodies and soluble TNF receptor

Tumor necrosis factor (TNF)-alpha inhibitors (infliximab, adalimumab, and etanercept) used in immune-mediated inflammatory diseases such as rheumatoid arthritis, Crohn's disease, or psoriatic arthritis have the potential to increase the risk of infectious complications. Pulmonary infections are one of the most frequent complications associated with the use of TNF inhibitors. This article provides an overview of the distinct types of infectious pulmonary complications seen in patients using these anticytokine drugs.

Type I interferon: a new player in TNF signaling

TNF and type I interferons (IFNs) are induced by microbial stimuli and mediate innate immune responses. They are also involved in the pathogenesis of chronic inflammatory diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Activated macrophages are an important driving force of inflammatory reactions and one of the major producers of TNF in innate immunity and chronic inflammation. Despite the fact that cells at sites of damage are continuously exposed to both cytokines, little is known about mechanisms regulating TNF and type I IFN interactions during inflammation. In this review, we discuss the role of an IFN-beta-mediated autocrine loop in the regulation of gene expression program induced by TNF in myeloid cells.

Targeted gene delivery to selected liver segments via isolated hepatic perfusion

BACKGROUND

Development of targeted gene transfer technologies is essential for in vivo gene therapy. In this study, we examined the feasibility of physically targeting an adenoviral vector to selected liver segments in rats by isolating the hepatic perfusion (IHSP) and clamping the portal vein between the upper and lower segments.

MATERIALS AND METHODS

The rats were divided into two groups: IHSP group and the inferior vena cava (IVC) group. The adenoviral vector, which harbored the beta-galactosidase (beta-gal) gene, was administered via the portal vein, after which unbound vector particles were washed out with phosphate-buffered saline (PBS) and removed via the cannulated inferior vena cava (IVC) in IHSP group, while the IVC group received the transgene directly via the IVC without isolation of the hepatic perfusion.

RESULTS

With this configuration (IHSP group), >99% of the beta-gal activity was limited to the targeted hepatic lobes, findings which were confirmed by histochemical staining with X-gal. We also found there to be significant differences in transgene expression among the hepatic lobes in the IVC group.

CONCLUSIONS

Taken together, these results indicate that the IHSP technique is useful for local gene delivery to selected liver segments, and that when evaluating the efficacy of IHSP in the treatment of liver disease (e.g., nonresectable tumors), interlobar differences must be given careful consideration to ensure that sufficient drug or vector is delivered to all targeted hepatic lobes.

A20 attenuates allergic airway inflammation in mice

TNF receptor 1 can activate signaling pathways leading to the activation of NF-kappaB. A20, an NF-kappaB-inducible protein, negatively regulates these signaling pathways and acts as an anti-inflammatory mediator. Therefore, A20 is viewed as a potential therapeutic target for inflammatory disease. In this study, we examined the effect of A20 on an OVA-induced allergic airway inflammation model in mice. We used an adenovirus containing A20 cDNA (Ad-A20) that was delivered intratracheally before OVA challenge. Single administration of Ad-A20 reduced airway inflammatory cell recruitment and peribronchiolar inflammation and suppressed the production of various cytokines in bronchoalveolar fluid. In addition, Ad-A20 suppressed mucus production and prevented the development of airway hyperresponsiveness. The protective effect of Ad-A20 was mediated by the inhibition of the NF-kappaB signaling pathway. Taken together, our results suggest that the development of an immunoregulatory strategy based on A20 may have therapeutic potential for the treatment of allergic asthma.

Adenovirus induction of IRF3 occurs through a binary trigger targeting Jun N-terminal kinase and TBK1 kinase cascades and type I interferon autocrine signaling

Pathogen recognition is a critical function of immune sentinel cells. Naïve macrophages or dendritic cells (DCs) undergo pathogen-directed activation and maturation, and as mature antigen-presenting cells (APCs), they contribute essential functions to both innate and adaptive immunity. Using recombinant adenovirus (rAdV) as a model for murine APC activation by DNA viruses, we demonstrate a critical role for stress kinase activation in cell intrinsic and extrinsic antiviral signaling cascades. We propose two viral triggers, viral capsid and viral DNA, are required for APC activation. Endosomal escape and presentation of cytosolic rAdV DNA induces phosphorylation of TANK-binding kinase 1 (TBK1) at serine 172 but does not induce IkappaB kinase epsilon activity as determined by in vitro kinase assays. However, induction of TBK1 alone is not sufficient for interferon regulatory factor 3 (IRF3) phosphorylation. We show that capsid-dependent activation of Jun N-terminal kinase (JNK) stress kinase is a necessary step, licensing TBK1 phosphorylation of IRF3 at Ser 396. A second later phase of JNK activity is required to coordinate phosphorylation of JNK-dependent transcription factors (c-Jun/ATF2) with activated IRF3 in the induction of primary IRF3-responsive transcripts. Finally, we demonstrate that maximal JNK/TBK1/IRF3 stimulation by rAdV depends on an intact type I interferon (IFN) signaling cascade. By requiring multiple viral triggers and type I IFN autocrine regulation, APCs have an inherent fail-safe mechanism against inappropriate activation and maturation.

Comparative analysis of vector biodistribution, persistence and gene expression following intravenous delivery of bovine, porcine and human adenoviral vectors in a mouse model

Nonhuman adenoviruses including bovine adenovirus serotype 3 (BAd3) and porcine adenovirus serotype 3 (PAd3) can circumvent pre-existing immunity against human adenovirus serotype 5 (HAd5) and are being developed as alternative vectors for gene delivery. To assess the usefulness of these vectors for in vivo gene delivery, we compared biodistribution, persistence, state of vector genome, and transgene and vector gene expression by replication-defective BAd3 and PAd3 vectors with those of HAd5 vector in a FVB/n mouse model following intravenous inoculation. BAd3 vector efficiently transduced the heart, kidney and lung in addition to the liver and spleen and persisted for a longer duration compared to PAd3 or HAd5 vectors. Biodistribution of PAd3 vector was comparable to that of HAd5 vector but showed more rapid vector clearance. Only linear episomal forms of BAd3, PAd3, and HAd5 vector genomes were detected. All three vectors efficiently expressed the green fluorescent protein (GFP) transgene proportionate to the vector genome copy number in various tissues. Furthermore, leaky expression of vector genes, both the early (E4) and the late (hexon) was observed in all three vectors and gradually declined with time. These results suggest that BAd3 and PAd3 vectors could serve as an alternative or supplement to HAd5 for gene delivery applications.

The impact of treatment with tumour necrosis factor-alpha antagonists on the course of chronic viral infections: a review of the literature

Biologics that antagonize the biological activity of tumour necrosis factor (TNF)-alpha, namely infliximab, etanercept and adalimumab, are increasingly used for treatment of immune-mediated inflammatory diseases, including psoriasis, worldwide. TNF-alpha antagonists are known to increase the risk of reactivation and infection, particularly of infections with intracellular bacteria such as Mycobacterium tuberculosis. More frequently these agents are given to patients with viral infections. Viral hepatitis and human immunodeficiency virus infections are often present in these patients, with a considerable geographical variation. Other concomitant viral infections such as herpes, cytomegalovirus and varicella zoster virus may occur much more frequently than tuberculosis or leprosy. General recommendations about the management related to possible problems associated with anti-TNF-alpha treatment and these viral infections are lacking. This short review will give an overview of the most recent data available on the effects of anti-TNF-alpha therapy on viral infections with a particular focus on patient management and screening recommendations.

Incorporation of membrane-anchored flagellin into influenza virus-like particles enhances the breadth of immune responses

We have designed a membrane-anchored form of the Toll-like receptor 5 ligand flagellin, the major proinflammatory determinant of enteropathogenic Salmonella, which was found to be glycosylated and expressed on cell surfaces. A chimeric influenza virus-like particle (cVLP) vaccine candidate containing A/PR8/34 (H(1)N(1)) hemagglutinin (HA), matrix protein (M1), and the modified flagellin as a molecular adjuvant was produced. The immunogenicity, including the serum antibody levels and cellular immune responses, and the protective efficacy against homologous and heterologous live virus challenge of the resulting VLPs were tested after intramuscular administration in a mouse model. The results demonstrated that flagellin-containing VLPs elicited higher specific immunoglobulin G (IgG) responses than standard HA and M1 VLPs, indicating the adjuvant effect of flagellin. Enhanced IgG2a and IgG2b but not IgG1 responses were observed with flagellin-containing VLPs, illuminating the activation of Th1 class immunity. The adjuvant effects of flagellin were also reflected by enhanced specific cellular responses revealed by the secretion of cytokines by freshly isolated splenocyte cultures when stimulated with pools of major histocompatibility complex class I or II peptides. When immunized mice were challenged with homologous live PR8 virus, complete protection was observed for both the standard and cVLP groups. However, when a heterosubtypic A/Philippines (H(3)N(2)) virus was used for challenge, all of the standard VLP group lost at least 25% of body weight, reaching the experimental endpoint. In contrast, for the cVLP group, 67% of mice survived the challenge infection. These results reveal that cVLPs designed by incorporating flagellin as a membrane-anchored adjuvant induce enhanced cross-protective heterosubtypic immune responses. They also indicate that such cVLP vaccines are a promising new approach for protection against pandemic influenza viruses.

TNF activates an IRF1-dependent autocrine loop leading to sustained expression of chemokines and STAT1-dependent type I interferon-response genes

Rapid induction of inflammatory genes by tumor necrosis factor (TNF) has been well studied, but little is known about delayed and chronic TNF responses. Here we investigated the kinetics of primary macrophage responses to TNF and discovered that TNF initiates an interferon-beta-mediated autocrine loop that sustains expression of inflammatory genes and induces delayed expression of interferon-response genes such as those encoding the transcription factors STAT1 and IRF7, which enhance macrophage responses to stimulation of cytokines and Toll-like receptors. TNF-induced interferon-beta production depended on interferon-response factor 1, and downstream gene expression was mediated by synergy between small amounts of interferon-beta and canonical TNF-induced signals. Thus, TNF activates a 'feed-forward' loop that sustains inflammation but avoids the potential toxicity associated with the high interferon production induced by stimulation of Toll-like receptors.

PEGylated adenovirus for targeted gene therapy

Bifunctional polyethylene glycol (PEG) molecules provide a novel approach to retargeting viral vectors without the need to genetically modify the vector. Modification of the surface of adenovirus with heterofunctional PEG allows further modification of the capsid with ligands. In addition, heterofunctional PEG modification ablates the normal tropism of the virus and reduces transduction of non-target tissues in vivo. Moreover, the addition of PEG chains to the surface of the virus shields antigen-binding sites, significantly reducing the susceptibility of the virus to antibody neutralization. Finally, T cell subsets from mice exposed to the PEGylated vector demonstrate a marked decrease in Th1 and Th2 responses, suggesting that PEG modification may help reduce the immune response to the vector.

One-year expression from high-capacity adenoviral vectors in the brains of animals with pre-existing anti-adenoviral immunity: clinical implications

The main challenge of gene therapy is to provide long-term, efficient transgene expression. Long-term transgene expression from first generation adenoviral vectors (Advs) delivered to the central nervous system (CNS) is elicited in animals not previously exposed to adenovirus (Ad). However, upon systemic immunization against Ad, transgene expression from a first generation Adv is abolished. High-capacity Advs (HC-Advs) provide sustained very long-term transgene expression in the brain, even in animals pre-immunized against Ad. In this study, we tested the hypothesis that a HC-Adv in the brain would allow for long-term transgene expression, for up to 1 year, in the brain of mice immunized against Ad prior to delivery of the vector to the striatum. In naïve animals, the expression of beta-galactosidase from Adv or HC-Adv was sustained for 1 year. In animals immunized prior to vector delivery, expression from a first generation Adv was abolished. These results point to a very long-term HC-Adv-mediated transgene expression in the brain, even in animals that had been immunized systemically against Ad before the delivery of HC-Adv into the brain. This study therefore indicates the utility of HC-Adv as a powerful gene therapy vector for chronic neurological disorders, even in patients who had been pre-exposed to Ad prior to gene therapy.

Application of a disease-regulated promoter is a safer mode of local IL-4 gene therapy for arthritis

The application of disease-regulated promoters in local gene therapy for rheumatoid arthritis potentiates the development of a sophisticated treatment that relies on a restricted and fine-tuned supply of biologicals. Although several studies have investigated regulated promoters for achieving effective transgene expression during arthritis, none have explored their potential for minimizing deleterious effects arising from constitutive overexpression of transgenes under naive conditions. Using naive and collagen-induced arthritic mice, we examined the applicability of a hybrid interleukin-1 enhancer/interleukin-6 proximal promoter for achieving efficacious murine interleukin-4 gene therapy under arthritic conditions, while minimizing interleukin-4-induced inflammation under naive conditions. We found strong upregulation of transgene expression in virally transduced knee joints under arthritic conditions compared to levels in naive animals. Besides its responsiveness, the promoter strength proved sufficient for generating therapeutically efficacious levels interleukin-4, as demonstrated by the successful protection against cartilage erosion in collagen-induced arthritis. Most importantly, promoter-mediated restriction of the potent chemotactic interleukin-4 in naive animals strongly reduced the amounts of inflammatory cell influx. This study suggests the suitability of the interleukin-1 enhancer/interleukin-6 proximal promoter for the development of a local gene therapy strategy for rheumatoid arthritis that requires fine-tuned and restricted expression of transgenes with a pleiotrophic nature.

A phase I trial of intravenous infusion of ONYX-015 and enbrel in solid tumor patients

ONYX-015 is an attenuated chimeric human group C adenovirus, which preferentially replicates in and lyses tumor cells that are p53 negative. The purpose of this phase I, dose-escalation study was to determine the safety and feasibility of intravenous infusion with ONYX-015 in combination with enbrel in patients with advanced carcinoma. Enbrel is a recombinant dimer of human tumor-necrosis factor (TNF)-alpha receptor, previously shown to reduce the level of functional TNF. Nine patients, three in each cohort received multiple cycles of ONYX-015 infusion (1 x 10(10), 1 x 10(11) and 1 x 10(12) vp weekly for 4 weeks/cycle) in addition to subcutaneous enbrel (only during cycle 1) injections per FDA-indicated dosing. Of the nine patients, four had stable disease. No significant adverse events were attributed to the experimental regimen, confirming that enbrel can be safely administered along with oncolytic virotherapy. Two of the three patients in cohort 3 had detectable viral DNA at days 3 and 8 post-ONYX-015 infusion. Their detectable circulating viral DNA was markedly higher during cycle 1 (with enbrel coadministration) as compared with cycle 2 (without enbrel) at the same time points. Area under the curve determinations indicate a marked higher level of TNF-alpha induction and accelerated clearance at cycle 2 in the absence of enbrel. Further assessment is recommended.

Respective roles of TNF-alpha and IL-6 in the immune response-elicited by adenovirus-mediated gene transfer in mice

The immunogenicity of recombinant adenoviruses (Ad) constitutes a major concern for their use in gene therapy. Antibody- and cell-mediated immune responses triggered by adenoviral vectors hamper long-term transgene expression and efficient viral readministration. We previously reported that interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha play an essential role in both the acute phase and antibody response against Ad, respectively. As TNF-alpha controls the immune response and the development of the immune system, we examined here the consequence of blockade of TNF-alpha activity through Ad-mediated gene delivery of a dimeric mouse TNFR1-IgG fusion protein on transgene expression from a second Ad. Ad encoding TNFR1-IgG (AdTNFR1-Ig) was injected intravenously along with Ad encoding beta-galactosidase or alpha1-antitrypsin transgene in wild-type (IL-6(+/+)) but also in IL-6-deficient mice (IL-6(-/-)) to analyze how TNF-alpha and IL-6 diminish liver gene transfer efficacy. Blockade of TNF-alpha leads to increased transgene expression in both wild-type and IL-6(-/-) mice due to a reduced inflammatory response and to diminished recruitment of macrophages and NK cells towards the liver. Antibody responses against adenoviral particles and expressed transgenes were only delayed in AdTNFR1-Ig-treated wild-type mice, but were markedly reduced in AdTNFR1-Ig-treated IL-6(-/-) mice. Finally, treatment of mice with etanercept, a clinically approved anti-TNF-alpha drug, confirmed the importance of controlling proinflammatory cytokines during gene therapy by adenoviral vectors.

In vivo analysis of adenovirus-specific cytotoxic T lymphocyte response in mice deficient in CD28, fas ligand, and perforin

Adenoviruses (Ad) have been extensively studied as gene delivery vectors in gene therapy and as vaccine carriers. The cell-mediated cytotoxicity induced by Ad is of great interest in both applications. However, the mechanism underlying Ad-specific cytotoxic T lymphocyte (CTL) generation and effector function remains unclear. In this study, we used a novel MHC class I tetramer and an in vivo CTL assay to examine the role of CD28, perforin, Fas ligand (FasL), and TNF-alpha in the generation and function of Ad-specific CTLs in vivo. During the primary response, there was a significant defect in both the generation and in vivo effector function of Ad-specific CTLs in CD28-/- mice, but not in CD4+ T cell-depleted mice or CD4-/- mice. The relative role of CTL effector molecules was assayed by in vivo CTL assay in perforin- or FasL-mutant mice, using donor cells from Fas-deficient or TNFR1/TNFR2-deficient mice. The results indicated that the in vivo CTL activity is mediated mainly by perforin. In the absence of perforin, production of FasL, but not TNF-alpha, by the CTLs results in lower level Ad-specific killing of target cells. These results provide important implications concerning the development of safe and effective Ad vectors for gene therapy and vaccines.

Adenoviral vector saturates Akt pro-survival signaling and blocks insulin-mediated rescue of tumor necrosis-factor-induced apoptosis

Recombinant adenoviruses are used extensively as delivery vectors in clinical gene therapy and in molecular biology, but little is known about how the viral carrier itself contributes to cellular responses. Here we show that infection with an E1/E3-deleted adenoviral vector (Adv) sensitizes human epithelial cells to tumor necrosis factor (TNF)-induced apoptosis. To explore the mechanism of Adv-mediated sensitization, we measured activity time courses for three protein kinases (MK2, IKK and JNK1) centrally involved in the TNF-receptor signaling network, as well as two kinases (Akt and ERK) activated by growth factors. Both the pro-apoptotic signal MK2 and the anti-apoptotic signal Akt were upregulated when Adv-infected cells were stimulated with TNF, and MK2 and Akt each contributed significantly to TNF-induced cell fate. Surprisingly, further activation of Akt in Adv-infected cells via insulin treatment did not significantly reduce apoptosis or MK2 activity. We show that the ineffectiveness of insulin-mediated anti-apoptotic signaling through Akt is due to saturation of Akt-effector substrate phosphorylation in Adv-infected cells. Normalizing Akt signaling relative to its Adv-induced baseline activity identified a global dose-response curve that relates Akt signaling to cellular survival. Thus, the background Akt activity induced by Adv limits the transmission of anti-apoptotic signals in response to further cytokine or growth-factor stimulation. The phenotypic and intracellular synergy between Adv and TNF may have implications for interpreting cellular responses in gene-therapy and laboratory applications.

NK cell-mediated immunopathology during an acute viral infection of the CNS

Natural killer (NK) and cytotoxic T (Tc) cells are prime effector populations in the antiviral response of the host. Tc cells are essential for recovery from many viral diseases but may also be responsible for immunopathology. The role of NK cells in recovery from viral infections is less well established. We have studied acute virulent Semliki Forest virus (vSFV) infection of the central nervous system in C57BL/6J mice, which was mainly controlled by NK cells without marked Tc cell involvement. We show that mice with defects in the Fas and/or granule exocytosis pathways of cytotoxicity are more resistant to lethal vSFV infection than wild-type mice. On the other hand, mice defective in the IFN-gamma response are more sensitive than wild-type mice, whereas mice lacking the Tc cell compartment (beta-2 microglobulin-deficient mice) exhibit susceptibility similar to wild-type mice. The additional finding that depletion of NK cells significantly delayed the mean time to death but did not prevent mortality in SFV-infected B6 mice suggests that cytolytic activity of NK cells is detrimental, while IFN-gamma production is beneficial for recovery from SFV infection. This is the first study illustrating an NK cell-mediated immunopathological outcome to an acute viral infection.

Modulation of TNFalpha, a determinant of acute toxicity associated with systemic delivery of first-generation and helper-dependent adenoviral vectors

Understanding the determinants of the host innate immune response to systemic administration of adenoviral (Ad) vectors is critical for clinical gene therapy. Acute toxicity occurs within minutes to hours after vector administration and is characterized by activation of innate immune responses. Our data indicate that in mice, indicators of vector toxicity include elevations of cytokine levels, liver transaminase levels and thrombocytopenia. To discern potential targets for blunting this host response, we evaluated genetic factors in the host response to systemically administered first-generation Ad vectors (FGV) and helper-dependent Ad vectors (HDV) containing beta-galactosidase expression cassettes. A preliminary screen for modulation of vector-induced thrombocytopenia revealed no role for interferon-gamma, mast cells or perforin. However, vector-induced thrombocytopenia and interleukin 6 (IL-6) expression are less evident in tumor necrosis factor alpha (TNFalpha)-deficient mice. Moreover, we also demonstrated that TNFalpha blockade via antibody or huTNFR:Fc pretreatment attenuates both thrombocytopenia (>40% increase in platelet count) and IL-6 expression (>80% reduction) without affecting interleukin 12 , liver enzymes, hematological indices or vector transduction in a murine model. Our data indicate that the use of HDV, in combination with clinically approved TNFalpha immunomodulation, may represent an approach for improving the therapeutic index of Ad gene therapy for human clinical trials.

Blockade of TNF-alpha decreases both inflammation and efficacy of intrapulmonary Ad.IFNbeta immunotherapy in an orthotopic model of bronchogenic lung cancer

Adenoviral immuno-gene therapy using interferon-beta has been effective in an orthotopic model of lung cancer. However, pulmonary inflammation induced by adenoviral (Ad) vectors will almost certainly limit the maximally tolerated dose. On the other hand, the strong innate immune response generated by the vector may be helpful in initiating the adaptive immune response required for efficacy. The goals of this study were to develop an effective approach to inhibit Ad.IFNbeta-mediated acute pulmonary inflammation and to determine whether this reduction of Ad-mediated inflammation decreased the therapeutic efficacy of Ad.IFNbeta in a mouse model of bronchioloalveolar cancer. Our data show that anti-TNF-alpha antibodies can blunt the innate pulmonary immune response induced by Ad vectors, even in sensitized animals. However, this effect also inhibited the ability of the animal to generate anti-tumor immune responses and reduced survival in an orthotopic lung cancer model responsive to Ad.IFNbeta treatment. Interestingly, in a flank model of tumor using a cell line derived from the lung tumor, TNF-alpha blockade did not inhibit efficacy. These data suggest that the innate immune response to adenovirus in the lung may be important in immuno-gene therapy of lung cancer. Therapeutic application of anti-inflammatory therapy in immuno-gene therapy strategies should thus be undertaken with caution.

Adenoviral delivery of the β2-adrenoceptor gene in sepsis: a subcutaneous approach in rat for kidney protection

Successful gene therapy requires gene delivery that is efficient, has an optimal route of administration and has biosafety. The aims of the present study were to evaluate the safety and applicability of the subcutaneous delivery route for adenoviral transgenes containing the human β2-adrenoceptor (adeno-β2-AR) and to investigate whether this approach prevented renal dysfunction in a rat model of endotoxaemic shock induced by LPS (lipopolysaccharide). Subcutaneous administration of adeno-β2-AR (a total of 1010 viral particles) significantly increased β-AR density in the kidney, lung and liver, but was without effect on physiological and plasma biochemical parameters. Moreover, this dose of virus did not cause any of the potential toxic responses of viral administration, such as inflammation and tissue TNF (tumour necrosis factor)-α expression. Although the LPS challenge caused a decrease in glomerular filtration rate, fractional excretion of sodium and renal β-AR density in all groups, the reduction in renal function was significantly less in the rats given adeno-β2-AR compared with non-treated rats. Thus, although further evaluation will be required, this initial study demonstrated that the subcutaneous injection of adeno-β2-AR was efficient, comparatively non-pathogenic and potentially therapeutic to deal with acute renal failure associated with sepsis.

Rapid Production of TNF-α following TCR Engagement of Naive CD8 T Cells

The acquisition of effector functions by naive CD8 T cells following TCR engagement is thought to occur sequentially with full functionality being gained only after the initiation of division. We show that naive CD8 T cells are capable of immediate effector function following TCR engagement, which stimulates the rapid production of TNF-alpha. Stimulation of splenocytes from naive mice of differing genetic backgrounds with anti-CD3epsilon mAb resulted in significant production of TNF-alpha by naive CD8 T cells within 5 h. Moreover, naive lymphocytic choriomeningitis virus-specific TCR-transgenic CD8 T cells stimulated with either their cognate peptide ligand or virus-infected cells produced TNF-alpha as early as 2 h poststimulation, with production peaking by 4 h. Naive CD8 T cells produced both membrane-bound and soluble TNF-alpha. Interfering with TNF-alpha activity during the initial encounter between naive CD8 T cells and Ag loaded dendritic cells altered the maturation profile of the APC and diminished the overall viability of the APC population. These findings suggest that production of TNF-alpha by naive CD8 T cells immediately after TCR engagement may have an unappreciated impact within the local environment where Ag presentation is occurring and potentially influence the development of immune responses.

IFN-γ: A Cytokine Essential for Rejection of CTL-Resistant, Virus-Infected Cells

We recently demonstrated differential susceptibility of cells expressing viral antigen to killing by antigen-specific cytotoxic T lymphocytes (CTLs). In addition, interferon-gamma (IFN-gamma) has been implicated in the clearance of some viruses from tissues. We explored the role of IFN-gamma in the cytotoxicity of Sendai virus-specific CTLs against virus-infected RL(male symbol)1 (T cell leukemia) or Meth A (fibrosarcoma) cells, as well as the growth of subcutaneously (s.c.) transplanted, virus-infected cells in IFN-gamma(+/+) or IFN-gamma(/) mice of the syngeneic strain (BALB/c). Sendai virus-specific CTLs were cytotoxic against virus-infected RL(male symbol)1 cells, and s.c. transplanted, virus-infected RL(male symbol)1 cells were acutely rejected from IFN-gamma(+/+) or IFN-gamma(/) mice. In contrast, the CTLs were inactive toward virus-infected Meth A cells, but s.c. transplanted, virus-infected Meth A cells were acutely rejected from IFN-gamma(+/+) but not IFN-gamma(/) mice. The s.c. growth of virus-infected Meth A cells in the mutant mice was markedly inhibited by s.c. injections of IFN-gamma, and the rejection from IFN-gamma(+/+) mice was delayed after specific elimination of macrophages by intravenous (i.v.) injections of dichloromethylene diphosphonatecontaining liposomes. These results suggest an essential role of IFN-gamma and involvement of macrophage in the rejection of CTL-resistant, virus-infected cells.

Functional interactions of antiapoptotic proteins and tumor necrosis factor in the context of a replication-competent adenovirus

Replication-selective oncolytic adenoviruses hold promise, but novel mechanisms must be identified to maximize intratumoral virus persistence, spread and therapeutic transgene-carrying capacity while maintaining safety. One of the main approaches to engineering cancer-selectivity has been to delete a viral gene that is theoretically expendable in cancer cells. Results with this approach have been mixed, however, as evidenced by controversy over Onyx-015 (E1B-55kD(-)) selectivity. We hypothesized that the functional redundancy between viral gene products might limit selectivity and/or potency with this approach. Antiviral immune inducers of apoptosis (eg TNF-alpha) have not been thoroughly investigated in previous studies. We therefore explored whether deletion of functionally redundant viral genes, E1B-19kD and E3B, both independently antagonize TNF-alpha, could lead to enhanced oncolytic potency while maintaining selectivity. Since tumors have numerous blocks in apoptotic pathways, we hypothesized that deletion of one or both gene regions would result in cancer-selectivity in the presence of TNF-alpha. We have previously shown that the E1B-19kD deletion resulted in enhanced viral spread in vitro and in immunocompetent tumor models in vivo. In contrast, the impact of E3B deletion, especially its in vitro selectivity and potency, was not thoroughly characterized, although it resulted in rapid immune-mediated viral clearance in vivo. Furthermore, previous publications indicated that double-deleted mutants have selectivity but unsatisfactory efficacy. We compared the selectivity and potency of E1B-19kD(-), E3B(-) and E1B-19kD(-)/E3B(-) mutants to wild-type adenovirus. In cancer cells, the E1B-19kD(-) mutant had superior replication, spread and cytolysis (+) or (-) TNF-alpha; deletion of both E1B-19kD and E3B was relatively deleterious. In normal cells without TNF-alpha, similar results were obtained. In contrast, all three mutants were significantly inhibited in the presence of TNF-alpha. In immunocompetent mice, all three mutants were significantly inhibited in normal tissue. In tumors, only the E1B-19kD(-) mutant demonstrated enhanced replication, spread and antitumoral efficacy. Therefore, E1B-19kD deletion and E3B retention should be incorporated in oncolytic adenoviruses for enhanced safety and efficacy. In addition, functional redundant viral genes and their biological mediators/targets need to be carefully examined for the next generation of gene-deleted oncolytic viruses.

Approaches to improving the kinetics of adenovirus-delivered genes and gene products

Adenovirus (Ad) vectors have been expected to play a great role in gene therapy because of their extremely high transduction efficiency and wide tropism. However, due to the intrinsic deficiency of their immunogenic toxicities, Ad vectors are rapidly cleared from the host, transgene expression is transient, and readministration of the same serotype Ad vectors is problematic. As a result, Ad vectors are continually undergoing refinement to realize their potential for gene therapy application. Even after 1999, when a patient fatally succumbed to the toxicity associated with Ad vector administration at a University of Pennsylvania (U.S.) experimental clinic, enthusiasm of gene therapists for Ad vectors has not waned. With great efforts from various research groups, significant advances have been achieved through comprehensive approaches to improving the kinetics of Ad vector-delivered genes and gene products.

Influence of recombinant adenovirus on liver injury in endotoxicosis and its modulation by IL-10 expression

Adenovirus-based gene therapy offers a unique opportunity to target gene expression to the liver by systemic delivery. However, systemic administration of a first generation adenoviral construct elicits an inflammatory response leading to TNF-alpha-dependent liver injury. The aim of this study was to evaluate whether the systemic administration of recombinant adenovirus exacerbates a subsequent TNF-alpha-dependent liver injury induced by D-galactosamine and lipopolysaccharide. Surprisingly, low-dose adenovirus administration (10(5) particles) protects, while high-dose adenovirus (10(10) particles) is associated with an exaggerated hepatic inflammatory response from a subsequent D-galactosamine and lipopolysaccharide challenge. This exacerbation is TNF-alpha dependent, since treatment with a TNF inhibitor fully protects against the liver injury. Moreover, intravenous administration of an adenoviral construct expressing the anti-inflammatory protein interleukin-10 reduces TNF-alpha appearance and attenuates the increased hepatocyte injury. Taken together, this report demonstrates potential additive effects of TNF-alpha responses induced by adenovirus and other inflammatory signals, and suggests that the response can be mitigated by relative adenovirus particle dose or by inhibitors, such as TNF-binding protein or interleukin 10.

Oncolytic viral therapies

Molecular research has vastly advanced our understanding of the mechanism of cancer growth and spread. Targeted approaches utilizing molecular science have yielded provocative results in the treatment of cancer. Oncolytic viruses genetically programmed to replicate within cancer cells and directly induce toxic effect via cell lysis or apoptosis are currently being explored in the clinic. Safety has been confirmed and despite variable efficacy results several dramatic responses have been observed with some oncolytic viruses. This review summarizes results of clinical trials with oncolytic viruses in cancer.

Immune responses against adenoviral vectors and their transgene products: a review of strategies for evasion

Human adenoviruses have been adopted as attractive vectors for in vivo gene therapy since they have a well-characterized genomic organization, can be grown to high titres and efficiently transduce a wide spectrum of dividing and non-dividing cells. However, the first-generation of adenoviral (Ad) vectors yielded only transient expression of the transgene in most immunocompetent mice. This constituted a major limitation of this early vector type. In contrast, persistent transgene expression can be established in immunodeficient mice. This suggests that the immunogenicity of adenoviral vectors limits the effective period of adenovirus-based gene therapy. Much effort has been put in devising strategies to circumvent the limitations imposed onto gene therapy by the immune system. Improvements in vector design have significantly improved the performance of the adenovirus vectors. Based on these results it is reasonable to anticipate that new modifications of the vectors will overcome some of the immunological barriers and will further expand the applicability of adenovirus-derived vectors.

Fas and TNFR1, but not cytolytic granule-dependent mechanisms, mediate clearance of murine liver adenoviral infection

After intravenous injection of replication-deficient adenovirus, hepatocytes are transduced and express high levels of adenovirus-encoded genes. However, adenovirally encoded gene expression is ablated rapidly by CD8+ T-cell-dependent mechanisms. Thus, this model is suitable for examining intrahepatic cytotoxic T lymphocyte (CTL) effector mechanisms. In the present studies, recombinant adenoviruses encoding secreted (human apolipoprotein A-I) or intracellular (beta-galactosidase) gene products were infused into mice with genetic deficiencies affecting the granule exocytosis-, Fas-, or tumor necrosis factor receptor 1 (TNFR1)-mediated pathways of CTL and natural killer cell effector function; the rates of clearance of adenovirus-encoded gene products were assessed. Clearance of secreted or intracellular adenoviral gene products was not delayed in perforin-deficient mice or dipeptidyl peptidase I-deficient mice, which fail to process and activate granzyme A or granzyme B. TNFR1-deficient mice also exhibited no delay in clearance of adenoviral gene products. However, adenoviral clearance from Fas-deficient mice was delayed, and such delays were much greater in mice deficient in both TNFR1 and Fas. In contrast, chimeric mice lacking both hepatic Fas and lymphocyte perforin function exhibited no greater delay in adenoviral clearance than chimeras deficient only in hepatic Fas expression. In conclusion, Fas-dependent mechanisms are required for efficient clearance of virally infected hepatocytes and, in Fas-deficient animals, TNFR1-dependent mechanisms provide an alternative mechanism for hepatic adenovirus clearance. In contrast, perforin- and granule protease-dependent cytotoxicity mechanisms play no apparent role in clearance of adenovirus from the liver.

The Innate Immune Response to Adenovirus Vectors

Gene therapy is a clinical strategy that may potentially treat an array of genetic and nongenetic diseases, as well as a novel method for drug delivery and vaccination. To these ends, adenovirus vectors are a promising means to deliver specific genes of interest into the patient. A major limitation of the use of adenovirus vectors is the host immune response. Adenovirus vectors induce the innate arm of the immune system that results in inflammation of transduced tissues and efficient clearance of administered vectors. Unlike adaptive immunity, the innate response is mediated by the adenovirus particle and does not require viral transcription. In vivo, the innate immune response involves the induction of cytokines and activation of effector leukocytes that comprise the host response to these agents. A number of interactions with leukocytes and with epithelial and endothelial cells are essential in triggering the host response to adenovirus vectors. Signal transduction via MAP kinases and NF-kappaB-mediated gene transcription are triggered during early virus-cell interactions and are key events in the innate recognition of adenovirus vector transduction. This review aims to describe data examining cellular and molecular mechanisms involved in the adenovirus-mediated innate immune response.

Defective Clearance of Adenovirus in IRF-1-/- Mice Associated with Defects in NK and T Cells but not Macrophages

A replication-defective adenovirus-LacZ recombinant virus (AdLacZ) was injected intravenously into IRF-1(-/-) mice and wild-type mice to characterize the contribution of IRF-1 to the immune-mediated clearance of Ad vector. Compared with wild-type mice, IRF-1(-/-) mice expressed higher levels of the LacZ gene product in the liver. After infusion of the AdLacZ, the expression of IRF-1 mRNA was upregulated in the liver of wild-type mice, but not in IRF-1(-/-) mice. Both spleen and liver mononuclear cells from IRF-1(-/-) mice initially exhibited a markedly lower number of NK, NK-T and CD8 T cells. At day 7 after the administration of AdLacZ, there was a significantly increased population of NK, NK-T and CD8 T cells in both spleen and liver, and also CD11b(+) cells in liver of IRF-1(-/-) mice, compared with the increased in wild-type mice. As IRF-1 is an important signal for production of IFN-gamma by CD8 T and NK cells as well as production of IL-12 by CD11b(+) cells, we determined whether there were lower levels of these cytokines in IRF-1(-/-) mice after Ad challenge. Surprisingly, there were lower levels of IL-12, but higher levels of IFN-gamma and IL-18 in IRF-1(-/-) compared with wild-type mice at day 7 after administration with AdLacZ. These results indicate that delayed clearance of Ad is associated with partial correction of defects of the NK, NK-T and CD8 T cells and increased production of IFN-gamma and IL-18 in IRF-1(-/-) mice.

TRAIL and viral infection

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family that can induce apoptosis when binding to either of two receptors bearing an intracellular death domain. The physiologic function of the TRAIL system, which also comprises three receptors not mediating a death signal has just begun to be elucidated. Expression of TRAIL, mostly upon stimulation by interferons, in different cytotoxic immune cells suggested it has a role as an important effector molecule in immune surveillance. In addition to its ability to induce apoptosis in transformed tumor cells, TRAIL has attracted attention for its possibly critical role in the defense against viral infection. Viruses may induce TRAIL expression in host and?or immune cells and sensitize host cells toward TRAIL-mediated apoptosis. On the other hand, viruses have evolved a variety of strategies to prevent TRAIL-mediated host cell death early in infection, which may contribute to allowing their replication and the spread of viral progeny. The knowledge of the molecular mechanisms leading to modification of TRAIL sensitivity in virus-host cell interactions may also impact upon future (virus-based) strategies to increase TRAIL sensitivity of tumor cells.

Antiviral Cytokines Induce Hepatic Expression of the Granzyme B Inhibitors, Proteinase Inhibitor 9 and Serine Proteinase Inhibitor 6

Expression of the granzyme B inhibitors, human proteinase inhibitor 9 (PI-9), or the murine orthologue, serine proteinase inhibitor 6 (SPI-6), confers resistance to CTL or NK killing by perforin- and granzyme-dependent effector mechanisms. In light of prior studies indicating that virally infected hepatocytes are selectively resistant to this CTL effector mechanism, the present studies investigated PI-9 and SPI-6 expression in hepatocytes and hepatoma cells in response to adenoviral infection and to cytokines produced during antiviral immune responses. Neither PI-9 nor SPI-6 expression was detected by immunoblotting in uninfected murine or human hepatocytes. Similarly, human Huh-7 hepatoma cells were found to express only very low levels of PI-9 relative to levels detected in perforin- and granzyme-resistant CTL or lymphokine-activated killer cells. Following in vivo adenoviral infection or in vitro culture with IFN-alphabeta or IFN-gamma, SPI-6 expression was induced in murine hepatocytes. Similarly, after culture with IFN-alpha, induction of PI-9 mRNA and protein expression was observed in human hepatocytes and Huh-7 cells. IFN-gamma and TNF-alpha also induced 4- to 10-fold higher levels of PI-9 mRNA expression in Huh-7 cells, whereas levels of mRNA encoding a related serine proteinase inhibitor, proteinase inhibitor 8, were unaffected by culture of Huh-7 cells with IFN-alpha, IFN-gamma, or TNF-alpha. These findings indicate that cytokines that promote antiviral cytopathic responses also regulate expression of the cytoprotective molecules, PI-9 and SPI-6, in hepatocytes that are potential targets of CTL and NK effector mechanisms.

Adenovirus-induced maturation of dendritic cells through a PI3 kinase-mediated TNF-alpha induction pathway

Systemic administration of adenovirus and adenovirus vectors induces a robust innate and adaptive immune response in a variety of animal models. In tumor necrosis factor (TNF)(-/-) mice, a diminished immune response to adenovirus (Ad) infection has been attributed to compromised dendritic cell (DC) maturation. In this report, we investigated the mechanisms responsible for Ad-mediated activation and maturation of DC. Ad infection induced high levels of TNF-alpha expression by murine bone marrow-derived DC, comparable to levels observed with lipopolysaccharide exposure. Ad-induced TNF-alpha production was necessary for DC maturation and acts in an autocrine manner. Unlike TNF-alpha production associated with exposure to lipopolysaccharide, Ad induction of TNF-alpha was not dependent on the MyD88 signaling pathway. In contrast, Ad-induced TNF-alpha production and DC maturation were dependent on signaling by phosphoinositide-3-OH kinase (PI3K), as determined by wortmannin and LY294002 blocking experiments. The adenovirus capsid protein penton contains a well characterized arginine-glycine-aspartic acid integrin-binding domain that stimulates PI3K in fibroblast cell lines. When this region of the penton was mutated, TNF-alpha expression and bone marrow-derived DC maturation were attenuated. We propose that integrin-mediated PI3K induction of NF-kappaB activates an autocrine TNF-alpha pathway required for DC maturation in response to Ad.

An inflammation-inducible adenoviral expression system for local treatment of the arthritic joint

To achieve a disease-regulated transgene expression for physiologically responsive gene therapy of arthritis, a hybrid promoter was constructed. The human IL-1 beta enhancer region (-3690 to -2720) upstream of the human IL-6 promoter region (-163 to +12) was essential in mounting a robust response in HIG-82 synovial fibroblasts and in RAW 264,7 macrophages. A replication-deficient adenovirus was engineered with luciferase (Luc) controlled by the IL-1/IL-6 promoter (Ad5.IL-1/IL-6-Luc). LPS caused a 23- and 4.6-fold induction of Luc. activity in RAW cells infected with Ad5.IL-1/IL-6-Luc or the conventional Ad5.CMV-Luc construct, respectively. Next, adenoviruses (10(6) ffu) were injected into the knees of C57Bl/6 mice. An intra-articular injection of zymosan, 3 days after Ad5.IL-1/IL-6-Luc, increased Luc. activity by 39-fold but had no effect in the Ad5.CMV-Luc joints. The constitutive CMV promoter was rapidly silenced and could not be reactivated in vivo. In contrast, the IL-1/IL-6 promoter could be reactivated by Streptococcal cell wall (SCW)-induced arthritis up to 21 days after infection. Next the IL-1/IL-6 promoter was compared to the C3-Tat/HIV-LTR two-component system in wild-type, IL-6(-/-) and IL-1(-/-) gene knockout mice. Both systems responded well to LPS-, zymosan- and SCW-induced arthritis. However, the basal activity of the IL-1/IL-6 promoter was lower and IL-6 independent. This study showed that the IL-1/IL-6 promoter is feasible to achieve disease-regulated transgene expression for treatment of arthritis.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

Adenovirus encoding soluble tumor necrosis factor alpha receptor immunoglobulin prolongs gene expression of a cotransfected reporter gene in rat lung

OBJECTIVE

Because almost all pulmonary diseases are not caused by one gene, multiple gene transfection is required for current gene therapy. Adenovirus is an important gene therapy vector, but a short duration and the inability of repeated administration remain limitations. The aims of this study were to evaluate whether adenoviral vector encoding soluble tumor necrosis factor alpha receptor immunoglobulin and beta-galactosidase cotransfection prolongs gene expression and facilitates repeated vector administration to investigate the feasibility of a cotransfection strategy.

METHODS

F344 rats received intratracheal administration of 1 x 10(9) plaque-forming units of adenoviral vector encoding beta-galactosidase or both adenoviral vector encoding beta-galactosidase and adenoviral vector encoding soluble tumor necrosis factor alpha receptor immunoglobulin. In the expression study beta-galactosidase gene expression in the lung was examined by means of enzyme-linked immunosorbent assay on days 2, 7, 14, 28, and 56 (n = 4/day). In the repeated transfection study, soluble tumor necrosis factor alpha receptor immunoglobulin and beta-galactosidase were readministered once (7 days after the first adenovirus administration) or twice (on days 7 and 14; n = 4/day). A 2-way factorial analysis of variance was used for statistical analysis.

RESULTS

Soluble tumor necrosis factor alpha receptor immunoglobulin and beta-galactosidase cotransfection prolonged the duration of beta-galactosidase expression. However, antiadenovirus antibody production was significantly increased in the cotransfection group. In addition, there was no increase in beta-galactosidase expression after readministration of soluble tumor necrosis factor alpha receptor immunoglobulin and beta-galactosidase.

CONCLUSION

Adenoviral vector encoding soluble tumor necrosis factor alpha receptor immunoglobulin and beta-galactosidase cotransfection prolongs beta-galactosidase expression but does not increase beta-galactosidase expression after repeated administration. These results suggest that tumor necrosis factor alpha is one of the most important factors in regulating the duration of gene expression. The cotransfection approach is feasible, but the increase of antiadenovirus antibodies might make repeated cotransfection unfeasible.