Successful gene therapy via intraarticular injection of adenovirus vector containing CTLA4IgG in a murine model of type II collagen-induced arthritis

Systemic gene transfer of binding immunoglobulin protein (BiP) prevents disease progression in murine collagen-induced arthritis

Summary Recombinant human binding immunoglobulin protein (BiP) has previously demonstrated anti-inflammatory properties in multiple models of inflammatory arthritis. We investigated whether these immunoregulatory properties could be exploited using gene therapy techniques. A single intraperitoneal injection of lentiviral vector containing the murine BiP (Lenti-mBiP) or green fluorescent protein (Lenti-GFP) transgene was administered in low- or high-dose studies during early arthritis. Disease activity was assessed by visual scoring, histology, serum cytokine and antibody production measured by cell enzyme-linked immunosorbent assay (ELISA) and ELISA, respectively. Lentiviral vector treatment caused significant induction of interferon (IFN)-γ responses regardless of the transgene; however, further specific effects were directly attributable to the BiP transgene. In both studies Lenti-mBiP suppressed clinical arthritis significantly. Histological examination showed that low-dose Lenti-mBiP suppressed inflammatory cell infiltration, cartilage destruction and significantly reduced pathogenic anti-type II collagen (CII) antibodies. Lenti-mBiP treatment caused significant up-regulation of soluble cytotoxic T lymphocyte antigen-4 (sCTLA-4) serum levels and down-regulation of interleukin (IL)-17A production in response to CII cell restimulation. In-vitro studies confirmed that Lenti-mBiP spleen cells could significantly suppress the release of IL-17A from CII primed responder cells following CII restimulation in vitro, and this suppression was associated with increased IL-10 production. Neutralization of CTLA-4 in further co-culture experiments demonstrated inverse regulation of IL-17A production. In conclusion, these data demonstrate proof of principle for the therapeutic potential of systemic lentiviral vector delivery of the BiP transgene leading to immunoregulation of arthritis by induction of soluble CTLA-4 and suppression of IL-17A production.

Self in vivo production of a synthetic biological drug CTLA4Ig using a minicircle vector

Cytotoxic T lymphocyte-associated antigen 4 immunoglobulin fusion protein (CTLA4Ig, abatacept) is a B7/CD28 costimulation inhibitor that can ward off the immune response by preventing the activation of naïve T cells. This therapeutic agent is administered to patients with autoimmune diseases such as rheumatoid arthritis. Its antiarthritic efficacy is satisfactory, but the limitations are the necessity for frequent injection and high cost. Minicircles can robustly express the target molecule and excrete it outside the cell as an indirect method to produce the protein of interest in vivo. We inserted the sequence of abatacept into the minicircle vector, and by successful in vivo injection the host was able to produce the synthetic protein drug. Intravenous infusion of the minicircle induced spontaneous production of CTLA4Ig in mice with collagen-induced arthritis. Self-produced CTLA4Ig significantly decreased the symptoms of arthritis. Injection of minicircle CTLA4Ig regulated Foxp3(+) T cells and Th17 cells. Parental and mock vectors did not ameliorate arthritis or modify the T cell population. We have developed a new concept of spontaneous protein drug delivery using a minicircle vector. Self in vivo production of a synthetic protein drug may be useful when biological drugs cannot be injected because of manufacturing or practical problems.

Targeting co-stimulatory pathways in gene therapy

Gene therapy with recombinant viral vectors such as adenovirus and adenovirus-associated virus holds great promise in treating a wide range of diseases because of the high efficiency with which the viruses transfer their genomes into host cells in vivo. However, the activation of the host immune responses remains a major hurdle to successful gene therapy. Studies in the past two decades have elucidated the important role co-stimulation plays in the activation of both T and B cells. This review summarizes our current understanding of T cell co-stimulatory pathways, and strategies targeting these co-stimulatory pathways in gene therapy applications as well as potential future directions.

Intra-articular gene delivery and expression of interleukin-1Ra mediated by self-complementary adeno-associated virus

BACKGROUND

The adeno-associated virus (AAV) has many safety features that favor its use in the treatment of arthritic conditions; however, the conventional, single-stranded vector is inefficient for gene delivery to fibroblastic cells that primarily populate articular tissues. This has been attributed to the inability of these cells to convert the vector to a double-stranded form. To overcome this, we evaluated double-stranded self-complementary (sc) AAV as a vehicle for intra-articular gene delivery.

METHODS

Conventional and scAAV vectors were used to infect lapine articular fibroblasts in culture to determine transduction efficiency, transgene expression levels, and nuclear trafficking. scAAV containing the cDNA for interleukin (IL)-1 receptor antagonist (Ra) was delivered to the joints of naïve rabbits and those with IL-1beta-induced arthritis. From lavage of the joint space, levels of transgenic expression and persistence were measured by enzyme-linked immunosorbent assay. Infiltrating leukocytes were quantified using a hemocytometer.

RESULTS

Transgene expression from scAAV had an earlier onset and was approximately 25-fold greater than conventional AAV despite the presence of similar numbers of viral genomes in the nuclei of infected cells. Fibroblasts transduced with scAAV produced amounts of IL1-Ra comparable to those transduced with adenoviral and lentiviral vectors. IL1-Ra was present in lavage fluid of most animals for 2 weeks in sufficient quantities to inhibit inflammation of the IL-1beta-driven model. Once lost, neither subsequent inflammatory events, nor re-administration of the virus could re-establish transgene expression.

CONCLUSIONS

scAAV-mediated intra-articular gene transfer is robust and similarly efficient in both normal and inflamed joints; the resulting transgenic expression is sufficient to achieve biological relevance in joints of human proportion.

Intervention of an inflammation amplifier, triggering receptor expressed on myeloid cells 1, for treatment of autoimmune arthritis

OBJECTIVE

Triggering receptor expressed on myeloid cells 1 (TREM-1) is inducible on monocyte/macrophages and neutrophils and accelerates tissue destruction by propagating inflammatory responses in disease related to bacterial infections. Its blockade rescues the hosts in murine models of sepsis, to clear the bacteria without impairing the host defense. The aim of this study was to investigate the involvement of TREM-1 in an autoimmune, noninfectious disease.

METHODS

Synovial tissue specimens from the joints of patients with rheumatoid arthritis (RA) and the joints of mice with collagen-induced arthritis (CIA) were examined for TREM-1 expression, using flow cytometric analysis. Expression of TREM-1 on macrophages was induced by lipopolysaccharide, with or without a cyclooxygenase inhibitor. Rheumatoid synovial cells were stimulated with agonistic anti-TREM-1 antibodies. Recombinant adenovirus encoding the extracellular domain of TREM-1 fused with IgG-Fc (AxCATREM-1 Ig) or synthetic TREM-1 antagonistic peptides were injected to treat CIA, and the clinical manifestations of the antigen-specific T cell and B cell responses were evaluated.

RESULTS

TREM-1 was expressed on CD14+ cells in rheumatoid synovial tissue and synovial macrophages from mice with CIA. Unlike murine macrophages, human monocyte/macrophages did not depend on prostaglandin E2 for up-regulation of TREM-1. Agonistic anti-TREM-1 antibodies promoted tumor necrosis factor alpha production from rheumatoid synovial cells. Blockade of TREM-1 using AxCATREM-1 Ig and antagonistic peptides ameliorated CIA without affecting the serum levels of anti-type II collagen antibodies or the proliferative responses of splenocytes to type II collagen.

CONCLUSION

TREM-1 ligation contributes to the pathology of autoimmune arthritis. The results of this study implied that blockade of TREM-1 could be a new approach to rheumatic diseases that is safer than the presently available immunosuppressive treatments.

Attenuation of experimental autoimmune myocarditis by blocking T cell activation through 4-1BB pathway

4-1BB, a member of the tumor necrosis factor receptor (TNFR) family, binds the 4-1BB ligand (4-1BBL), works as a costimulatory molecule, and regulates T cell-mediated immune responses. Although inflammation is an essential pathological feature of myocarditis, the role of 4-1BB in experimental autoimmune myocarditis (EAM) remains unclear. Lewis rats were immunized on day 0 with purified porcine cardiac myosin to establish EAM. 4-1BB-immunoglobulin (4-1BBIg) was administered intraperitoneally (n=6) a total of 9 times (3 times per week). Rats were killed on day 21 to study effects of 4-1BB/4-1BBL pathway blockade. For controls, isotype-matched human IgG was administered in other EAM rats (n=6). Histologic and echocardiographic examination showed development of EAM attenuated by 4-1BBIg. Suppression of mRNA expression for IL-1alpha, IL-1beta, IL-4, IL-6, and TNF-alpha was noted in the heart tissue treated with 4-1BBIg. Treatment with 4-1BBIg reduced production of Th1-type cytokines, and inhibited T cell proliferation in vitro. In the 4-1BB signaling pathway in splenocytes, 4-1BBIg suppressed JNK, p38, and IkappaB activity but not that of ERK1/2. Blockade of T cell activation through the 4-1BB/4-1BBL pathway regulates development of EAM; therefore, 4-1BB may be an effective target for treating myocarditis.

Perspectives on the use of gene therapy for chronic joint diseases

Advances in molecular and cellular biology have identified a wide variety of proteins including targeted cytokine inhibitors, immunomodulatory proteins, cytotoxic mediators, angiogenesis inhibitors, and intracellular signalling molecules that could be of great benefit in the treatment of chronic joint diseases, such as osteo- and rheumatoid arthritis. Unfortunately, protein-based drugs are difficult to administer effectively. They have a high rate of turnover, requiring frequent readministration, and exposure in non-diseased tissue can lead to serious side effects. Gene transfer technologies offer methods to enhance the efficacy of protein-based therapies, enabling the body to produce these molecules locally at elevated levels for extended periods. The proof of concept of gene therapies for arthritis has been exhaustively demonstrated in multiple laboratories and in numerous animal models. This review attempts to condense these studies and to discuss the relative benefits and limitations of the methods proposed and to discuss the challenges toward translating these technologies into clinical realities.

Gene therapy for arthritis

Arthritis is among the leading causes of disability in the developed world. There remains no cure for this disease and the current treatments are only modestly effective at slowing the disease's progression and providing symptomatic relief. The clinical effectiveness of current treatment regimens has been limited by short half-lives of the drugs and the requirement for repeated systemic administration. Utilizing gene transfer approaches for the treatment of arthritis may overcome some of the obstacles associated with current treatment strategies. The present review examines recent developments in gene therapy for arthritis. Delivery strategies, gene transfer vectors, candidate genes, and safety are also discussed.

Primer: pitfalls of aspiration and injection

This review on joint aspiration and injection focuses on three common clinical problems: how to deal with 'dry taps', especially when a septic joint is suspected in the differential diagnosis; how to avoid rare complications associated with these techniques; and how to reduce pain in patients who are particularly sensitive. Solutions to these problems are proposed, and although no new data or insights are provided, this article could be used as a noncomprehensive check list for trainee rheumatologists. This review focuses on the knee, because of the common appearance of septic joints in the differential diagnosis of inflammatory knee effusion, and the paramount importance of septic joints in this setting. The five reasons for failing to aspirate fluid from a difficult knee joint that are discussed here could be applied to other more problematic joints, such as the elbow or ankle. Some additional time-consuming techniques involving more than one syringe and two operators might not be cost effective in many situations, but these should be taught for use in selected cases in which pain hinders aspiration. Training should also be provided to ensure that rheumatologists never inject against pressure, and that they switch to the lateral approach when aspirating the knee if their first attempt fails, especially if a septic joint is suspected and fluid must be obtained for diagnosis.

Intraarticular interferon-beta gene therapy ameliorates adjuvant arthritis in rats

Interferon (IFN)-beta has significant immunomodulatory properties and has received much interest as a potentially therapeutic agent for rheumatoid arthritis (RA). Systemic IFN-beta treatment of patients with RA was not effective, probably because of pharmacokinetic issues. Therefore, we studied the effect of local IFN-beta production by adenovirus-mediated gene transfer to the ankle joints of arthritic rats. Adjuvant arthritis (AA) in rats was used as a model to study intraarticular gene therapy with an adenoviral vector encoding the rat IFN-beta gene (Ad.IFN-beta). The effect on paw swelling was measured by water displacement plethysmometry. Synovial tissue of the hind paws was examined by immunohistochemistry. Bone destruction was analyzed on the basis of radiographs. In addition, quantitative real-time polymerase chain reaction was used to assess IFN-beta expression. Levels of IFN-beta mRNA and protein peaked 2 days after intraarticular injection and declined thereafter. Local delivery of Ad.IFN-beta after the onset of disease reduced paw swelling significantly. This was accompanied by a reduction in synovial inflammation. The clinical effects in rat AA lasted up to 9 days. Strikingly, Ad.IFN-beta treatment protected bone from erosion, reduced levels of c-Cbl and Cbl-b (both signaling molecules essential for osteoclast activity), and reduced the matrix metalloproteinase-3:tissue inhibitor of metalloproteinase-1 ratio in the joint. Immunohistochemical analysis of the synovial tissue revealed a clear shift toward a more antiinflammatory cytokine profile. Local overexpression of IFN-beta inhibits arthritis progression and protects against bone destruction in rat AA. These findings validate IFN-beta as a therapeutic molecule for intraarticular gene therapy of arthritis.

CTLA-4IG suppresses reactive oxygen species by preventing synovial adherent cell-induced inactivation of rap1, a ras family GTPASE mediator of oxidative stress in rheumatoid arthritis T cells

OBJECTIVE

Oxidative stress contributes to the inflammatory properties of rheumatoid arthritis (RA) synovial T lymphocytes. This study was undertaken to investigate the mechanisms leading to production of reactive oxygen species (ROS) and oxidative stress in RA synovial T lymphocytes.

METHODS

ROS production in T lymphocytes from the peripheral blood (PB) of healthy donors and from the PB and synovial fluid (SF) of RA patients was measured by ROS-dependent fluorescence of 6-carboxy-2',7'-dichlorofluorescein. Rap1 GTPase activation was assessed by activation-specific probe precipitation. Proliferation of RA PB and SF T lymphocytes was assayed by 3H-thymidine incorporation. In some experiments, RA PB T cells were preincubated with autologous SF or with PB or SF adherent cells. Experiments were performed in the absence or presence of transwell membranes or CTLA-4Ig fusion proteins. Short- and long-term stimulations of healthy donor PB T lymphocytes were performed with inflammatory cytokines, in the absence or presence of activating anti-CD28 antibodies.

RESULTS

T lymphocyte ROS production and Rap1 inactivation were mediated by cell-cell contact with RA synovial adherent cells, and this correlated with T cell mitogenic hyporesponsiveness. CTLA4-Ig blockade of synovial adherent cell signaling to CD28 T cells reversed the inhibition of Rap1 activity and prevented induction of ROS. Introduction of active RapV12 into T cells also prevented induction of ROS production. Coincubation of T cells with stimulating anti-CD28 antibodies and inflammatory cytokines synergistically increased T cell ROS production.

CONCLUSION

Cell-cell contact between T cells and RA synovial adherent cells mediates Rap1 inactivation and subsequent ROS production in T lymphocytes following exposure to inflammatory cytokines. This process can be blocked by CTLA4-Ig fusion protein.

Exosomes Derived from IL-10-Treated Dendritic Cells Can Suppress Inflammation and Collagen-Induced Arthritis

We have demonstrated previously that local, adenoviral-mediated gene transfer of viral IL-10 to a single joint of rabbits and mice with experimental arthritis can suppress disease in both the treated and untreated contralateral joints. This contralateral effect is mediated in part by APCs able to traffic from the treated joint to lymph nodes as well as to untreated joints. Moreover, injection of dendritic cells (DC) genetically modified to express IL-4 or Fas ligand was able to reverse established murine arthritis. To examine the ability of exosomes derived from immunosuppressive DCs to reduce inflammation and autoimmunity, murine models of delayed-type hypersensitivity and collagen-induced arthritis were used. In this study, we demonstrate that periarticular administration of exosomes purified from either bone marrow-derived DCs transduced ex vivo with an adenovirus expressing viral IL-10 or bone marrow-derived DCs treated with recombinant murine IL-10 were able to suppress delayed-type hypersensitivity responses within injected and untreated contralateral joints. In addition, the systemic injection of IL-10-treated DC-derived exosomes was able suppress the onset of murine collagen-induced arthritis as well as reduce severity of established arthritis. Taken together, these data suggest that immature DCs are able to secrete exosomes that are involved in the suppression of inflammatory and autoimmune responses. Thus DC-derived exosomes may represent a novel, cell-free therapy for the treatment of autoimmune diseases.

Gene therapy in animal models of rheumatoid arthritis: are we ready for the patients?

Rheumatoid arthritis (RA) is a chronic inflammatory disease of the synovial joints, with progressive destruction of cartilage and bone. Anti-tumour necrosis factor-α therapies (e.g. soluble tumour necrosis factor receptors) ameliorate disease in 60–70% of patients with RA. However, the need for repeated systemic administration of relatively high doses in order to achieve constant therapeutic levels in the joints, and the reported side effects are downsides to this systemic approach. Several gene therapeutic approaches have been developed to ameliorate disease in animal models of arthritis either by restoring the cytokine balance or by genetic synovectomy. In this review we summarize strategies to improve transduction of synovial cells, to achieve stable transgene expression using integrating viruses such as adeno-associated viruses, and to achieve transcriptionally regulated expression so that drug release can meet the variable demands imposed by the intermittent course of RA. Evidence from animal models convincingly supports the application of gene therapy in RA, and the feasibility of gene therapy was recently demonstrated in phase I clinical trials.

Differential requirement for the CD40-CD154 costimulatory pathway during Th cell priming by CD8 alpha+ and CD8 alpha- murine dendritic cell subsets

Dendritic cells (DCs) regulate the development of distinct Th populations and thereby provoke appropriate immune responses to various kinds of Ags. In the present work, we investigated the role CD40-CD154 interactions play during the process of Th cell priming by CD8 alpha(+) and CD8 alpha(-) murine DC subsets, which have been reported to differently regulate the Th response. Adoptive transfer of Ag-pulsed CD8 alpha(+) DCs induced a Th1 response and the production of IgG2a Abs, whereas transfer of CD8 alpha(-) DCs induced Th2 cells and IgE Abs in vivo. Induction of distinct Th populations by each DC subset was also confirmed in vitro. Although interruption of CD80/CD86-CD28 interactions inhibited Th cell priming by both DC subsets, disruption of CD40-CD154 interactions only inhibited the induction of the Th1 response by CD8 alpha(+) DCs in vivo. CD40-CD154 interactions were not required for the proliferation of Ag-specific naive Th cells stimulated by either DC subset, but were indispensable in the production of IL-12 from CD8 alpha(+) DCs and their induction of Th1 cells in vitro. Taken together, in our immunization model of Ag-pulsed DC transfer, CD40-CD154 interactions play an important role in the development of CD8 alpha(+) DC-driven Th1 responses but not CD8 alpha(-) DC-driven Th2 responses to protein Ags.

Multiple functions for CD28 and cytotoxic T lymphocyte antigen-4 during different phases of T cell responses: implications for arthritis and autoimmune diseases

Chronic T cell responses, as they occur in rheumatoid arthritis, are complex and are likely to involve many mechanisms. There is a growing body of evidence that, in concert with the T cell antigen receptor signal, CD28 and cytotoxic T-lymphocyte antigen-4 (CTLA-4; CD152) are the primary regulators of T cell responses. Whereas CD28 primarily activates T cell processes, CTLA-4 inhibits them. The mechanism for this dichotomy is not fully understood, especially as CD28 and CTLA-4 recruit similar signalling molecules. In addition, recent studies demonstrate that CD28 and CTLA-4 have multiple functions during T cell responses. In particular, CTLA-4 exerts independent distinct effects during different phases of T cell responses that could be exploited for the treatment of rheumatoid arthritis.

Costimulation Blockade in the Treatment of Rheumatic Diseases

The autoimmune response is executed via cognate interactions between effector immune cells and antigen presenting cells. Cognate interactions provide the immune effectors with specific signals generated through the antigen receptor as well as with second, non-specific signals, generated from the interaction of pairs of cell-surface molecules (costimulatory molecules) present on their plasma membrane. Disruption of this second, non-specific costimulatory signal results in the interruption of the productive (auto)immune response, leading to anergy, a state of immune unresponsiveness. The CD28:B7 families of molecules and the CD40:CD40L pair of molecules are considered as critical costimulatory elements. Disruption of the CD28:B7 interaction using a genetically engineered soluble form of the inhibitory molecule CTLA4 in vitro, as well as in experimental models of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), led to the inhibition of the autoimmune response. Similarly, promising data stem from the use of an anti-CD40L monoclonal antibody (mAb) in murine SLE. While such treatments prevent the development of autoimmunity in animal models, this preventive approach is inapplicable to human diseases. However, the rational bench-to-bedside approach led investigators to clinical trials of CTLA4-Ig and of two different humanized anti-human CD40L mAbs in patients with RA and SLE, respectively. Initial experience with the use of CTLA4-Ig in patients with RA is encouraging, since in one short-term trial the construct was well-tolerated and produced clinically meaningful improvement of the disease in a significant proportion of those treated. Surprisingly, the anti-CD40L mAb treatment approach in human lupus was not fruitful, since short-term administration of the anti-CD40L mAb ruplizumab in lupus nephritis was correlated with life-threatening prothrombotic activity despite initial encouraging data in the serology and renal function of the patients. Also, IDEC-131 anti-CD40L mAb treatment did not prove to be clinically effective in human SLE, despite being well tolerated. Precise tailoring of the administration schemes for these novel therapeutic modalities is awaited.Finally, conceptually different approaches to block costimulation by inhibiting the induced expression of costimulatory molecules or the transmission of their specific intracytoplasmic signal have already produced encouraging preliminary results.

Ocular transfer of retinal glial cells transduced ex vivo with adenovirus expressing viral IL-10 or CTLA4-Ig inhibits experimental autoimmune uveoretinitis

Gene transfer using immunomodulatory molecules is a promising tool for in vivo regulation of immune responses. Experimental autoimmune uveitis (EAU), which serves as a model for human ocular inflammation, is induced by systemic immunization with autoantigens, but its expression is restricted to the eye. Previously, we reported protection of rodents against EAU by intravenous or/and periocular injection of vIL-10-expressing adenovirus. Here, the expression of vIL-10 was targeted into the rat Lewis eye, by intravitreal injection of either the free virus or ex vivo transfected retinal Müller glial cells (RMG-vIL-10). As shown using GFP-expressing adenovirus, a longer expression of transgene was observed in the eye after transfer of transfected syngeneic RMG cells than was seen after injection of free virus. Intravitreal injection of RMG-vIL-10 led to significant decrease in ocular pathological manifestations, compared to control RMG cells. This was observed when cells were injected simultaneously with autoantigen, but also after a delayed administration of transfected cells. Finally, injection of RMG cells transfected with adenovirus expressing CTLA4 had a strongly protective effect. In conclusion, inhibition of antigen presentation at the site of expression of the autoimmune disorders represents an attractive alternative to treat ocular inflammation, and the transfer of ex vivo genetically modified cells provides a promising method to target the factor of interest into the eye.

Adenoviral delivery of soluble VEGF receptor 1 (sFlt-1) abrogates disease activity in murine collagen-induced arthritis

The angiogenic factor VEGF promotes synovitis and bone erosion in rheumatoid arthritis (RA). Previously, we have demonstrated that VEGF expression correlates with disease severity in RA patients and in murine collagen-induced arthritis (CIA). In this study, we adopted an adenoviral gene delivery system expressing soluble VEGF receptor 1 (sFlt-1) to further study the role of VEGF in CIA. Arthritis was induced in DBA/1 mice by injection of bovine collagen. Adenoviruses expressing human soluble VEGF receptor 1 (AdvsFlt-1), or without transgene (Adv0), were injected intravenously on the first day of arthritis. We found that disease severity and paw swelling were significantly suppressed in mice receiving AdvsFlt-1, when compared to untreated or Adv0-treated mice. Expression of sFlt-1 peaked 24 h after injection, with protein detectable in the liver, synovial issue and serum, but rapidly decreased by 72 h. The effect of sFlt-1 expression on signs of disease was paralleled by reduced joint destruction and decreased expression of the vascular marker von Willebrand factor. In summary, adenoviral delivery of human soluble VEGF receptor type 1 significantly suppressed disease activity in CIA. The actions of AdvsFlt-1 are likely to be mediated by reduced synovial neovascularization, and these results support the concept that VEGF blockade may be an effective therapeutic adjunct for the treatment of RA.

Gene transfer as a future therapy for rheumatoid arthritis

Inhibiting key pathogenic processes within the rheumatoid synovium is a most attractive goal to achieve, and the number of potential intra- and extracellular pathways operative in rheumatoid arthritis (RA) that could be used for a gene therapy strategy is increasing continuously. Gene transfer or gene therapy might also be one of the approaches to solve the problem of long-term expression of therapeutic genes, in order to replace the frequent application of recombinant proteins, in the future. However, at present, gene therapy has not reached a realistic clinical stage, which is mainly due to severe side effects in humans, the complexity of RA pathophysiology and the current state of available gene transfer techniques. On the other hand, novel gene delivery systems are not restricted to vectors or certain types of cells, as mobile cells including macrophages, dendritic cells, lymphocytes and multipotent stem cells can also be used as smart gene transfer vehicles. Moreover, the observation in animal models that application of viral vectors into a joint can exert additional therapeutic effects in nearby joints might also facilitate the transfer from animal to human gene therapy. Future strategies will also examine the potential of novel long-term expression vectors such as lentiviruses and cytomegalovirus (CMV)-based viruses as a basis for future clinical trials in RA.

Gene therapy for arthritis

Rheumatoid arthritis is an autoimmune disease with intra-articular inflammation and synovial hyperplasia that results in progressive degradation of cartilage and bone, in severe cases it causes systemic complications. Recently, biological agents that suppress the activities of proinflammatory cytokines have shown efficacy as antiarthritic drugs, but require frequent administration. Thus, gene transfer approaches are being developed as an alternative approach for targeted, more efficient and sustained delivery of inhibitors of inflammatory cytokines as well as other therapeutic agents. Indeed, the efficacy of gene transfer for the treatment of arthritis has been demonstrated in mouse, rat, rabbit, and horse models of disease whereas the feasibility of the approach has been demonstrated in Phase I clinical trials. In this review, the current status of both preclinical and clinical arthritis gene therapy is presented. In addition, the advantages and disadvantages of different types of vectors, target cells and therapeutic genes being developed for the treatment of arthritis are summarized. Finally, the future directions of the rapidly developed field of arthritis gene therapy are outlined.

Systemic delivery of a high-capacity adenoviral vector expressing mouse CTLA4Ig improves skeletal muscle gene therapy

Adenoviral vectors (AdV) are promising vectors for gene transfer of skeletal muscle. To alleviate humoral and cellular immune responses that limit successful gene transfer, the present study determined the route of administration of AdmCTLA4Ig (an adenovirus that encodes a fusion protein of mouse cytotoxic T lymphocyte-associated protein 4 (CTLA4) and the Fc protion of immunoglobulin G (IgG), CTLA4Ig) that provided optimal AdV-mediated immunosuppression. AdmCTLA4Ig was administered either intramuscularly (i.m.), intravenously (i.v.), or in the footpad (f.p.) of mice that simultaneously received an i.m. injection of an AdV encoding enhanced green fluorescent protein (AdEGFP). EGFP expression in muscle and serum levels of CTLA4Ig were higher in the i.v. and f.p. groups than the i.m. group 30 days after treatment. The i.v. and f.p. groups showed lower levels of CD4(+) and CD8(+) T-cell infiltration and decreased interferon-gamma (IFN-gamma) and interleukin 2 (IL-2) production by splenocytes. The T helper cell (Th) 2 cytokine, interleukin 4 (IL-4), was increased 30 days after treatment in the i.v. group. Neutralizing antibodies to AdV were lower in the i.v. and f.p. groups, whereas total antibodies to AdV and EGFP were lower only in the f.p. group. Our results suggest that the optimal route of administration of AdmCTLA4Ig is i.v., providing at least 2 months of stable transgene expression in muscle. The inhibition of the cellular immune response, especially the Th1 response, appeared to play a critical role in prolonging transgene expression. These results suggest that AdV-mediated delivery of targeted immune suppression will be a useful adjunct to muscle gene delivery.