Inhibition of chemokine expression by adenovirus early region three (E3) genes

High-Capacity Adenoviral Vectors: Expanding the Scope of Gene Therapy

The adaptation of adenoviruses as gene delivery tools has resulted in the development of high-capacity adenoviral vectors (HC-AdVs), also known, helper-dependent or "gutless". Compared with earlier generations (E1/E3-deleted vectors), HC-AdVs retain relevant features such as genetic stability, remarkable efficacy of in vivo transduction, and production at high titers. More importantly, the lack of viral coding sequences in the genomes of HC-AdVs extends the cloning capacity up to 37 Kb, and allows long-term episomal persistence of transgenes in non-dividing cells. These properties open a wide repertoire of therapeutic opportunities in the fields of gene supplementation and gene correction, which have been explored at the preclinical level over the past two decades. During this time, production methods have been optimized to obtain the yield, purity, and reliability required for clinical implementation. Better understanding of inflammatory responses and the implementation of methods to control them have increased the safety of these vectors. We will review the most significant achievements that are turning an interesting research tool into a sound vector platform, which could contribute to overcome current limitations in the gene therapy field.

RID: Evaluation of the Possible Inhibiting Effect of the Proinflammatory Signaling Induced by TNF-α through NF-κβ and AP-1 in Two Cell Lines of Breast Cancer

Receptor internalization and degradation (RID), is a transmembrane protein coded within the E3 region expression cassette of adenoviruses. RID downregulates the cell surface expression of epidermal growth factor receptor (EGFR), tumor necrosis factor receptor (TNFR), and apoptosis antigen 1 (FAS), causing a reduction of the effects of their respective ligands. In addition, RID inhibits apoptosis by decreasing the secretion of TNF-related apoptosis-inducing ligand (TRAIL) by normal tissue cells. In this article, we report that RID inhibited chemokine expression in human breast cancer cell line MDA-MB-231 but showed no effect in cell line MCF7. These dissimilar results may be due to the different molecular and functional properties of both cell lines. Therefore, it is necessary to replicate this study in other breast cancer cell models.

Pathogenesis and management of adenoviral keratoconjunctivitis

Human adenovirus (HAdV) is a ubiquitous virus that infects the mucosa of the eye. It is the most common cause of infectious conjunctivitis worldwide, affecting people of all ages and demographics. Pharyngoconjunctival fever outbreak is due to HAdV types 3, 4, and 7, whereas outbreaks of epidemic keratoconjunctivitis are usually caused by HAdV types 8, 19, 37, and 54. Primary cellular receptors, such as CAR, CD46, and sialic acid interact with fiber-knob protein to mediate adenoviral attachment to the host cell, whereas adenoviral penton base–integrin interaction mediates internalization of adenovirus. Type 1 immunoresponse to adenoviral ocular infection involves both innate immunity mediated by natural killer cells and type 1 interferon, as well as adaptive immunity mediated mainly by CD8 T cells. The resulting ocular manifestations are widely variable, with pharyngoconjunctival fever being the most common, manifesting clinically with fever, pharyngitis, and follicular conjunctivitis. Epidemic keratoconjunctivitis, however, is the severest form, with additional involvement of the cornea leading to development of subepithelial infiltrates. Because there is currently no US Food and Drug Administration-approved treatment for adenoviral ocular infection, current management is palliative. The presence of sight-threatening complications following ocular adenoviral infection warrants the necessity for developing antiadenoviral therapy with enhanced therapeutic index. Future trends that focus on adenoviral pathogenesis, including adenoviral protein, which utilize host receptors to promote infection, could be potential therapeutic targets, yielding shorter active disease duration and reduced disease burden.

The oncolytic virus dl922-947 reduces IL-8/CXCL8 and MCP-1/CCL2 expression and impairs angiogenesis and macrophage infiltration in anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human solid tumor and current treatments are ineffective in increasing patients' survival. Thus, the development of new therapeutic approaches for ATC is needed. We have previously shown that the oncolytic adenovirus dl922-947 induces ATC cell death in vitro and tumor regression in vivo. However, the impact of dl922-947 on the pro-tumorigenic ATC microenvironment is still unknown. Since viruses are able to regulate cytokine and chemokine production from infected cells, we sought to investigate whether dl922-947 virotherapy has such effect on ATC cells, thereby modulating ATC microenvironment. dl922-947 decreased IL-8/CXCL8 and MCP-1/CCL2 production by the ATC cell lines 8505-c and BHT101-5. These results correlated with dl922-947-mediated reduction of NF-κB p65 binding to IL8 promoter in 8505-c and BHT101-5 cells and CCL2 promoter in 8505-c cells. IL-8 stimulates cancer cell proliferation, survival and invasion, and also angiogenesis. dl922-947-mediated reduction of IL-8 impaired ATC cell motility in vitro and ATC-induced angiogenesis in vitro and in vivo. We also show that dl922-947-mediated reduction of the monocyte-attracting chemokine CCL2 decreased monocyte chemotaxis in vitro and tumor macrophage density in vivo. Interestingly, dl922-947 treatment induced the switch of tumor macrophages toward a pro-inflammatory M1 phenotype, likely by increasing the expression of the pro-inflammatory cytokine interferon-γ. Altogether, we demonstrate that dl922-947 treatment re-shape the pro-tumorigenic ATC microenvironment by modulating cancer-cell intrinsic factors and the immune response. An in-depth knowledge of dl922-947-mediated effects on ATC microenvironment may help to refine ATC virotherapy in the context of cancer immunotherapy.

Infection with host-range mutant adenovirus 5 suppresses innate immunity and induces systemic CD4+ T cell activation in rhesus macaques

Ad5 is a common cause of respiratory disease and an occasional cause of gastroenteritis and conjunctivitis, and seroconversion before adolescence is common in humans. To gain some insight into how Ad5 infection affects the immune system of rhesus macaques (RM) 18 RM were infected with a host-range mutant Ad5 (Ad5hr) by 3 mucosal inoculations. There was a delay of 2 to 6 weeks after the first inoculation before plasmacytoid dendritic cell (pDC) frequency and function increased in peripheral blood. Primary Ad5hr infection suppressed IFN-γ mRNA expression, but the second Ad5hr exposure induced a rapid increase in IFN-gamma mRNA in peripheral blood mononuclear cells (PBMC). Primary Ad5hr infection suppressed CCL20, TNF and IL-1 mRNA expression in PBMC, and subsequent virus exposures further dampened expression of these pro-inflammatory cytokines. Primary, but not secondary, Ad5hr inoculation increased the frequency of CXCR3+ CD4+ T cells in blood, while secondary, but not primary, Ad5hr infection transiently increased the frequencies of Ki67+, HLADR+ and CD95+/CCR5+ CD4+ T cells in blood. Ad5hr infection induced polyfunctional CD4 and CD8+ T cells specific for the Ad5 hexon protein in all of the animals. Thus, infection with Ad5hr induced a complex pattern of innate and adaptive immunity in RM that included transient systemic CD4+ T cell activation and suppressed innate immunity on re-exposure to the virus. The complex effects of adenovirus infection on the immune system may help to explain the unexpected results of testing Ad5 vector expressing HIV antigens in Ad5 seropositive people.

STAT1 interaction with E3-14.7K in monocytes affects the efficacy of oncolytic adenovirus

Oncolytic viruses based on adenovirus type 5 (Ad5) have been developed as a new class of therapeutic agents for cancers that are resistant to conventional therapies. Clinical experience shows that these agents are safe, but virotherapy alone has not achieved long-term cure in cancer patients. The vast majority of oncolytic adenoviruses used in clinical trials to date have deletion of the E3B genes. It has been demonstrated that the antitumor potency of the E3B-deleted mutant (dl309) is inferior to adenovirus with E3B genes intact. Tumors treated with dl309 show markedly greater macrophage infiltration than E3B-intact adenovirus. However, the functional mechanisms for this were not previously known. Here, we demonstrate that deletion of E3B genes increases production of chemokines by monocytes after adenovirus infection and increases monocyte migration. The E3B 14,700-Da protein (E3B-14.7K) inhibits STAT1 function by preventing its phosphorylation and nuclear translocation. The STAT1 inhibitor, fludarabine, rescues the effect of E3B-14.7K deletion by downregulating target chemokine expression in human and murine monocytes and results in an enhanced antitumor efficacy with dl309 in vivo. These findings have important implications for clinical use of E3B-deleted oncolytic adenovirus and other E3B-deleted adenovirus vector-based therapy.

Vaccines within vaccines: the use of adenovirus types 4 and 7 as influenza vaccine vectors

Adenovirus Types 4 and 7 (Ad4 and Ad7) are associated with acute respiratory distress (ARD). In order to prevent widespread Ad-associated ARD (Ad-ARD) the United States military immunizes new recruits using a safe and effective lyophilized wildtype Ad4 and Ad7 delivered orally in an enteric-coated capsule. We cloned Ad4 and Ad7 and modified them to express either a GFP-Luciferase (GFPLuc) fusion gene or a centralized influenza H1 hemagglutinin (HA1-con). BALB/c mice were injected with GFPLuc expressing viruses intramuscularly (i.m.) and intranasally (i.n.). Ad4 induced significantly higher luciferase expression levels as compared with Ad7 by both routes. Ad7 transduction was restored using a human CD46+ transgenic mouse model. Mice immunized with serial dilutions of viruses expressing the HA1-con influenza vaccine gene were challenged with 100 MLD 50 of influenza virus. Ad4 protected BALB/c mice at a lower dose by i.m. immunization as compared with Ad7. Unexpectedly, there was no difference in protection by i.n. immunization. Although Ad7 i.m. transduction was restored in CD46+ transgenic mice, protection against influenza challenge required even higher doses as compared with the BALB/c mice. However, Ad7 i.n. immunized CD46+ transgenic mice were better protected as compared with Ad4. Interestingly, the restoration of Ad7 transduction in CD46+ mice did not increase vaccine efficacy and indicates that Ad7 may transduce a different subset of cells through alternative receptors in the absence of CD46. These data indicate that both Ad4 and Ad7 can effectively induce anti-H1N1 immunity against a heterologous challenge using a centralized H1 gene. Future studies in non-human primates or human clinical trials will determine the overall effectiveness of Ad4 and Ad7 as vaccines for influenza.

Cytokine patterns associated with a serotype 8 fowl adenovirus infection

This study examined cytokine gene expression patterns associated with fowl adenovirus (FAdV) infection. The selected cytokine mRNA was quantified by quantitative real-time reverse transcription-PCR in spleen, liver, and cecal tonsil during the course of infection of chickens with a serotype 8 FAdV (FAdV-8). Compared to uninfected chickens, infected birds had higher mRNA expression of interleukin (IL)-18 and IL-10 in spleen and liver, respectively. Interferon gamma (IFN-γ) mRNA expressed in spleen and liver of infected chickens was significantly upregulated, while the expression of IL-8 mRNA in spleen and liver of infected chickens was significantly downregulated. There was no significant difference between infected and uninfected groups in terms of cytokine gene expression in cecal tonsil. These results indicate that these four cytokines might play an important role in driving the immune responses following FAdV-8 infection.

A novel hybrid adenoretroviral vector with more extensive E3 deletion extends transgene expression in submandibular glands

Salivary glands are an attractive target for gene transfer. Salivary epithelial cells are considered to be highly differentiated and have low rates of cell division (~6 months), affording the opportunity to obtain relatively long-term transgene expression in the absence of genomic integration. Here, we report a novel modified hybrid adenoretroviral vector, which provides stable transgene expression in salivary epithelial cells in vivo for up to 6 months in the absence of genomic integration. This modified hybrid vector, Ad(ΔE1/3)LTR(2)EF1α-hEPO, encodes human erythropoietin (hEPO) and differs from a previously developed hybrid vector, AdLTR(2)EF1α-hEPO, by having more extensive E3 gene deletion. Following direct salivary gland gene transfer by retroductal cannulation, rats transduced with Ad(ΔE1/3)LTR(2)EF1α-hEPO had sustained, elevated serum hEPO levels and hematocrits for 6 months (length of experiment), as compared with ~2 months for animals administered the AdLTR(2)EF1α-hEPO vector. Immunohistochemistry demonstrated that this novel vector could transduce both acinar and ductal cells. Interestingly, the Ad(ΔE1/3)LTR(2)EF1α-hEPO vector evoked much weaker local (salivary gland) immune responses than seen after AdLTR(2)EF1α-hEPO vector delivery, which likely permits its significantly lengthened transgene expression in this tissue.

Chemotactic antiviral cytokines promote infectious apical entry of human adenovirus into polarized epithelial cells

Mucosal epithelia provide strong barriers against pathogens. For instance, the outward facing apical membrane of polarized epithelial cells lacks receptors for agents, such as hepatitis C virus, herpesvirus, reovirus, poliovirus or adenovirus. In addition, macrophages eliminate pathogens from the luminal space. Here we show that human adenovirus type 5 engages an antiviral immune response to enter polarized epithelial cells. Blood-derived macrophages co-cultured apically on polarized epithelial cells facilitate epithelial infection. Infection also occurs in the absence of macrophages, if virus-conditioned macrophage-medium containing the chemotactic cytokine CXCL8 (interleukin-8), or recombinant CXCL8 are present. In polarized cells, CXCL8 activates a Src-family tyrosine kinase via the apical CXCR1 and CXCR2 receptors. This activation process relocates the viral co-receptor ανβ3 integrin to the apical surface, and enables apical binding and infection with adenovirus depending on the primary adenovirus receptor CAR. This paradigm may explain how other mucosal pathogens enter epithelial cells.

Studying how pathogens enter polarized epithelial cells is important for understanding infection. Here, activation of chemokine receptors on the apical membrane of epithelial cells, is shown to engage Src family tyrosine signalling, resulting in relocation of the viral co-receptor αvβ3 to the apical membrane and adenovirus entry.

The host response to adenovirus, helper-dependent adenovirus, and adeno-associated virus in mouse liver

Understanding host responses to viral gene therapy vectors is necessary for the development of safe and efficacious in vivo gene transfer agents. We describe the use of high-density spotted complementary DNA microarrays in monitoring the in vivo host transcriptional responses in mouse liver upon administration of either a "first-generation"adenoviral (Ad) vector, a helper-dependent "gutless" adenoviral (HD) vector, or an adeno-associated viral (AAV) vector containing human factor IX (hFIX) expression cassettes. Since HD and AAV do not contain any viral genes, they allow us to assess the host response to the viral capsid and packaged nonviral DNA in whole animals. Comparison of the host response to Ad and HD helps assess the importance of leaky adenoviral gene expression. While all three vectors induced characteristic temporally sequenced programs of gene expression, the gene expression programs induced by the Ad and HD adenovirus vectors were remarkably similar, including the induction of a prominent type I interferon (IFN)-dependent cluster within 6 hours of administration. In contrast, the AAV-based vector caused far fewer alterations of host-gene expression. Our results indicate that recognition of the Ad capsid or double-stranded DNA (of nonviral origin) in the vector elicits a robust type I IFN response that is, however, not elicited by AAV-derived vector transduction.

Cytotoxicity of NF-κB inhibitors Bay 11-7085 and caffeic acid phenethyl ester to Ramos and other human B-lymphoma cell lines

OBJECTIVE

The viability of normal and malignant B-cells was shown to depend on the constitutive activation of the nuclear factor (NF)- kappaB pathway. Thus, attempts to find efficient inhibitors of NF-kappaB play a central role in the search for novel anti-B lymphoma therapies. We studied the effects of two NF-kappaB inhibitors, Bay 11-7085 (BAY) and caffeic acid phenethyl ester (CAPE), on the viability of B-lymphoma cell lines.

METHODS

We investigated the mechanism(s) of the cytotoxic effect of the NF-kappaB inhibitors, BAY, and CAPE on human-lymphoma and nonhematological cell lines.

RESULTS

BAY and CAPE were shown to kill Ramos-Burkitt's lymphoma cells with IC(50) values of 0.7 microM and 4 microM, respectively. The rapid killing by BAY (h) vs the slower killing by CAPE (1-3 days), and their differential effects on the stages of the cell cycle, indicated that these drugs induce killing by different mechanisms. BAY and CAPE induced a loss of the cytoplasmic compartment and generated pyknotic nuclei, which lacked nuclear or nucleosomal fragmentation, features characteristic of necrosis rather than apoptosis. BAY also induced a rapid loss of the mitochondrial potential and rapid inhibition of p65 NF-kappaB binding to its kappaB motif without reducing the level of nuclear p65.

CONCLUSION

Our results indicate that BAY causes a necrotic rather than apoptotic cell death, either through its effect on the NF-kappaB pathway and/or by affecting additional molecular targets. The high sensitivity of B-lymphoma cell lines to the cytotoxicity of BAY, justify further research to explore its potential therapeutic effect on human B lymphomas.

Porcine adenovirus type 3 E1B large protein downregulates the induction of IL-8

Replication-defective (E1-E3 deleted) adenovirus vector based gene delivery results in the induction of cytokines including IL-8, which may contribute to the development of inflammatory immune responses. Like other adenoviruses, E1 + E3 deleted porcine adenovirus (PAdV) 3 induces the production of IL-8 in infected cells. In contrast, no IL-8 production could be detected in cells infected with wild-type or mutant PAdV-3s containing deletion in E1A + E3 (PAV211) or E1B^small + E3 (PAV212). Expression of PAdV-3 E1B^large inhibited the NF-κB dependent transcription of luciferase from IL-8 promoter. Imunofluorescence and electrophoretic mobility shift assays suggested that constitutive expression of PAdV-3 E1B^large inhibited the nuclear translocation of NF-κB and its subsequent binding to DNA. These results suggest that E1B^large interacts with NF-κB to prevent transcription and down regulate proinflammatory cytokine IL-8 production.

Adenovirus RIDalphabeta complex inhibits lipopolysaccharide signaling without altering TLR4 cell surface expression

The transmembrane heterotrimer complex 10.4K/14.5K, also known as RID (for "receptor internalization and degradation"), is encoded by the adenovirus E3 region, and it down-regulates the cell surface expression of several unrelated receptors. We recently showed that RID expression correlates with down-regulation of the cell surface expression of the tumor necrosis factor (TNF) receptor 1 in several human cells. This observation provided the first mechanistic explanation for the inhibition of TNF alpha-induced chemokines by RID. Here we analyze the immunoregulatory activities of RID on lipopolysaccharide (LPS) and interleukin-1 beta (IL-1beta)-mediated responses. Although both signaling pathways are strongly inhibited by RID, the chemokines up-regulated by IL-1beta stimulation are only marginally inhibited. In addition, RID inhibits signaling induced by LPS without affecting the expression of the LPS receptor Toll-like receptor 4, demonstrating that RID need not target degradation of the receptor to alter signal transduction. Taken together, our data demonstrate the inhibitory effect of RID on two additional cell surface receptor-mediated signaling pathways involved in inflammatory processes. The data suggest that RID has intracellular targets that impair signal transduction and chemokine expression without evidence of receptor down-regulation.

Direct adenovirus-mediated IGF-I gene transduction of synovium induces persisting synovial fluid IGF-I ligand elevations

Insulin-like growth factor-I (IGF-I) is one of the most influential growth factors in cartilage repair. Maintenance of adequate IGF-I levels after articular repair procedures is complicated by the short biological half-life of IGF-I in vivo. This study investigated the potential for more prolonged IGF-I delivery through direct adenoviral mediated transduction of synovial tissues in the metacarpophalangeal (MCP) joints of horses. The use of a large animal model provided a structurally similar and metabolically relevant corollary to the human knee. The complete IGF-I coding sequence was packaged into an E1-E3 deleted adenovirus-5 vector under cytomegalovirus promoter control (AdIGF-I), and injected at varying total joint doses to the MCP joints of 14 horses. Direct injection of 20 and 50 x 10(10) AdIGF-I resulted in significant elevations of IGF-I in synovial fluid for approximately 21 days. Synovial tissue taken from injected joints at day 35 following injection and compared to tissue taken preinjection from the same joints revealed elevated synoviocyte IGF-I mRNA levels for the highest viral dose by in situ hybridization and real-time PCR techniques. AdIGF-I injections did not result in significant lameness, joint effusion or elevated total protein concentrations in the synovial fluid. Mild mononuclear infiltration of white blood cells was evident in histologic sections of the synovium in the second highest adenoviral IGF-I dose of 20 x 10(10) particles. Cartilage biopsies taken from all injected joints did not reveal any significant changes in proteoglycan levels nor in histological morphology, which included chondrocyte cloning, architecture, cell type or toluidine blue staining, when compared to control joints. Based on these findings, gene transfer of IGF-I to the synovium of joints can result in significant and persistent elevations of IGF-I ligand in synovial fluid with minimal detrimental effects. Direct IGF-I gene therapy may offer a simple approach in treating patients with acute cartilage injury.

Adenovirus immunoregulatory E3 proteins prolong transplants of human cells in immunocompetent mice

The majority of proteins encoded in the early 3 (E3) region of human subgroup C adenoviruses function to modulate the host immune response. For example, gp19K, one of these E3 proteins, prevents the major histocompatibility complex type I (MHC-I) from presenting viral antigens on the surface of the infected cell. Other E3 proteins, such as the RID and 14.7K proteins, counteract the effector phase of the cellular immune response. In order to study further the effects of these proteins, we constructed an E1-/E3- adenovirus vector, Ad/E3, that contains all the E3 genes with the exception of the cytolytic adp gene, inserted into the deleted E1 region. The transcription of the E3 genes in this vector is driven by a CMV promoter in place of the native E3 promoter. Ad/E3 expressed close to wild-type adenovirus levels of all E3 proteins, and these proteins appear to function normally in cell culture. For example, in Ad/E3-infected cells, surface expression of MHC-I was down-regulated, as was cell surface display of death receptors Fas and TRAIL Receptor 1. A human cell line of lung origin (A549), which was rapidly rejected after transplantation into C57BL/6 mice, was protected for an extended time from the host immune response after infection with an Ad/E3, and went through a number of divisions in immunocompetent mice. These latter results indicate that the E3 proteins protect cells from destruction by the immune system.

Interference with the IL-1-signaling pathway improves the toxicity profile of systemically applied adenovirus vectors

The safety of gene therapy vectors is a major concern when novel viral or nonviral therapeutics are proposed for applications in humans. Adenovirus (Ad) vectors have been extensively used as efficient gene delivery vehicles in vitro over the last two decades. However, upon i.v. application, they elicit robust innate and inflammatory responses that may be fatal for the host. To date, the primary cytokines and chemokines involved in the initiation of these host responses remain illusive. In this study, we demonstrate that IL-1 is a major mediator involved in the initiation of immediate host responses toward i.v. applied Ad vectors. Using mice in which IL-1 signaling was genetically eliminated (IL-1RI-KO), or wild-type animals for which signaling was blocked by anti-IL-1 Abs, we found that i.v. applied Ad vectors elicited dramatically reduced acute inflammatory responses when compared with control animals. Importantly, the efficiency of Ad gene transfer in vivo was not significantly affected by interfering with IL-1 signaling. Using an in situ hybridization technique, we found that hepatocytes and Kupffer cells trigger IL-1 transcription in liver tissue after i.v. Ad vector administration. We also found that expression of the MIP-2 chemokine gene (which is responsible for recruitment of neutrophils to the liver) depends on IL-1 activation. Our data indicate that immediate innate and inflammatory host responses toward i.v. applied Ad vectors can be pharmacologically controlled through interference with IL-1 signaling pathways.

Adenoviral-mediated transduction of human pancreatic islets: importance of adenoviral genome for cell viability and association with a deficient antiviral response

As adenoviral vectors are extensively used for genetic manipulation of insulin-producing cells in vitro, there is an increasing need to evaluate their effects on the function, morphology, and viability of transduced pancreatic islets. In the present study we observed that specific adenoviral genotypes, carrying E4 and E1/E3 deletions, correlate with differential induction of necrosis in pancreatic islet cells. In particular, the adenovirus death protein encoded from the E3 region of the adenoviral genome was able to modulate the changes induced in the morphology and viability of the transduced cells. We also propose a putative role for the transcriptional regulator pIX. Although human islet cells showed an increased resistance in terms of viral concentrations required for the induction of cell toxicity, our results showed that they were unable to build up an efficient antiviral response after transduction and that their survival was dependent on the exogenous addition of alpha-interferon. An intact and fully functional beta-cell is crucial for the successful application of gene therapy approaches in type 1 diabetes, and therefore, the implications of our findings need to be considered when designing vectors for gene transfer into pancreatic beta-cells.

Inhibition of tumor necrosis factor (TNF) signal transduction by the adenovirus group C RID complex involves downregulation of surface levels of TNF receptor 1

Adenoviruses employ multiple genes to inhibit the host antiviral responses. There is increasing evidence that these immunoregulatory genes may function either during lytic or latent infection. Adenovirus early transcription region 3 (E3) encodes at least seven proteins, five of which block the acquired or innate immune response. Previous findings from this laboratory demonstrated that the E3 proteins 10.4K and 14.5K, which form a complex in the plasma membrane, inhibit tumor necrosis factor (TNF)-induced activation of NF-kappaB and the synthesis of chemokines. To determine the mechanism of inhibition of these pathways by the adenovirus E3 10.4K/14.5K proteins, we have examined the effects of this viral complex on the inhibition of AP-1 and NF-kappaB activation by TNF and found a reduction in assembly of the TNF receptor 1 (TNFR1) signaling complex at the plasma membrane accompanied by downregulation of surface levels of TNFR1.

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.

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.

Mechanisms of E3 Modulation of Immune and Inflammatory Responses

Adenoviruses contain genes that have evolved to control the host immune and inflammatory responses; however, it is not clear whether these genes function primarily to facilitate survival of the virus during acute infection or during its persistent phase. These issues have assumed greater importance as the use of adenoviruses as vectors for gene therapy has been expanded. This review will focus on the mechanism of immune evasion mediated by the proteins encoded within the early region 3 (E3) transcription region, which affect the functions of a number of cell surface receptors including Fas, intracellular cell signaling events involving NF-kappaB, and the secretion of pro-inflammatory molecules such as chemokines. The successful use of E3 genes in facilitating allogeneic transplantation and in preventing autoimmune diabetes in several transgenic mouse models will also be described.

Adenovirus early region 3 antiapoptotic 10.4K, 14.5K, and 14.7K genes decrease the incidence of autoimmune diabetes in NOD mice

Genes in the early region 3 (E3) of the adenovirus genome allow the virus to evade host immune responses by interfering with major histocompatibility (MHC) class I-mediated antigen presentation and tumor necrosis factor-alpha (TNF-alpha)- or Fas-induced apoptosis of infected cells. Autoimmune type 1 diabetes (T1D) is inhibited in NOD mice transgenically expressing all E3 genes under control of a rat insulin promoter (RIPE3/NOD). For dissecting the protective mechanisms afforded by various E3 genes, they were subdivided into RIP-driven transgene constructs. Strong T1D protection mediated at the beta-cell level characterized DL704/NOD mice lacking the E3 gp19K gene suppressing MHC class I expression but retaining the 10.4K, 14.5K, and 14.7K genes inhibiting Fas- or TNF-alpha-induced apoptosis and TNF-alpha-induced NF-kB activation. Much weaker protection characterized DL309/NOD mice expressing the gp19K but not the 10.4K, 14.5K, and 14.7K genes. While RIPE3/NOD splenocytes had an unexpected decrease in ability to adoptively transfer T1D, splenocytes from both the DL704 and DL309 stocks efficiently did so. These findings indicate that all E3 genes must be expressed to inhibit the diabetogenic potential of NOD immune cells. They also demonstrate that the antiapoptotic E3 genes most effectively protect pancreatic beta-cells from diabetogenic immune responses.

The impact of adenovirus infection on the immunocompromised host

Adenovirus (Ad) infections in immunocompromised hosts have increased in frequency as the number of patients with transplants of bone marrow, liver, kidney, heart and other organs increase in number and survive longer. The numbers of such patients have also increased because of the emergence of the HIV epidemic. Ad infections with the 51 different serotypes recognised to date have few pathognomonic signs and symptoms, and thus require a variety of laboratory-based procedures to confirm infection. These viruses have the ability to target various organs with relative serotype specificity and can cause diverse manifestations including serious life-threatening diseases characteristic of the organs involved. Ads have cytolytic and immunoregulatory properties. The clinical dilemma remains the prompt recognition of Ad-related disease, the differentiation of Ad infection from Ad disease and the differentiation from other causative agents. Since the armamentarium of effective antiviral agents available to treat Ads is unproven by controlled trials and the virus is often not acquired de novo, it is difficult to prevent reactivation in immunodeficient hosts or new acquisition from donor organs. Timely discontinuation of immunosuppressive agents is necessary to prevent morbid outcomes. The clinical diseases, diagnostic tests, antiviral agents and biological aspects of the Ads as pathogens in immunocompromised patients are discussed in the context of this review. Some of the newer diagnostic tests are based on the well-studied molecular biology of Ads, which also have been attenuated by selective viral DNA deletions for use as vectors in numerous gene therapy trials in humans.

A potential role for CXCR3 chemokines in the response to ocular HSV infection

Corneal infection with herpes simplex virus (HSV) leads to the recruitment of immune cells to the eye itself, the trigeminal ganglion and the brainstem. In addition, some resident cells in these target tissues are infected by HSV, activated during the inflammatory response or both. Chemokine signaling is an important component of the regulatory circuit governing the host immune response to virus infection. This review discusses chemokine responses in relation to HSV infection of the cornea emphasizing the role of CXCR3 chemokine signaling by the IFN-gamma inducible ligands MIG, IP10 and I-TAC and includes discussion of their potential role in immunopathology in the nervous system.

Human synapsin 1 gene promoter confers highly neuron-specific long-term transgene expression from an adenoviral vector in the adult rat brain depending on the transduced area

Targeting therapeutic transgene expression to defined tissues is a major task in the development of safe and efficient gene therapy protocols. Recombinant adenovirus is an attractive vector because it can be prepared in huge quantity and new generation vectors possess very large cloning capacities combined with reduced immunogenicity. In the brain, adenovirus transduces mainly glial cells, making it difficult to use this vector system in applications that need expression of therapeutic proteins in neurons. Here, we show that by using a small fragment of the human synapsin 1 gene promoter, we were able to restrict transgene expression from an adenoviral vector exclusively to neurons. Furthermore, we obtained stable long-term transgene expression from this vector in striatum and thalamus at appropriate vector dose. Other promoters like the CMV and U1snRNA promoters also mediated transgene expression over several months, but mainly in glial cells. Although the NSE promoter was relatively neuron specific, it still expressed in glial cells also, and was clearly outperformed by the synapsin promoter with respect to transcriptional neuronal targeting. As an important feature of adenoviral-mediated gene transfer to the brain, we demonstrate that dopaminergic neurons of the substantia nigra do not allow for long-term expression from adenoviral vectors. Strikingly, these neurons appeared to specifically attenuate transgene expression by deleting the adenoviral genome.