Ex vivo-transduced autologous skin fibroblasts expressing human Lim mineralization protein-3 efficiently form new bone in animal models

Local gene transfer of the human Lim mineralization protein (LMP), a novel intracellular positive regulator of the osteoblast differentiation program, can induce efficient bone formation in rodents. To develop a clinically relevant gene therapy approach to facilitate bone healing, we have used primary dermal fibroblasts transduced ex vivo with Ad.LMP-3 and seeded on a hydroxyapatite/collagen matrix prior to autologous implantation. Here, we demonstrate that genetically modified autologous dermal fibroblasts expressing Ad.LMP-3 are able to induce ectopic bone formation following implantation of the matrix into mouse triceps and paravertebral muscles. Moreover, implantation of the Ad.LMP-3-modified dermal fibroblasts into a rat mandibular bone critical size defect model results in efficient healing, as determined by X-rays, histology and three-dimensional microcomputed tomography (3DmuCT). These results demonstrate the effectiveness of the non-secreted intracellular osteogenic factor LMP-3 in inducing bone formation in vivo. Moreover, the utilization of autologous dermal fibroblasts implanted on a biomaterial represents a promising approach for possible future clinical applications aimed at inducing new bone formation.

IL-12p70 and IL-18 gene-modified dendritic cells loaded with tumor antigen-derived peptides or recombinant protein effectively stimulate specific Type-1 CD4+ T-cell responses from normal donors and melanoma patients in vitro

Although CD4(+) Type-1T helper (Th1) cells secreting interferon-gamma (IFN-gamma) appear to play an essential role in promoting durable antitumor immunity, we have previously shown that patients with cancer exhibit dysfunctional Th1-type responses against epitopes derived from tumor antigens, such as MAGE-A6. Here, we engineered human dendritic cells (DCs) to secrete high levels of the IFN-gamma-inducing cytokines, interleukin (IL)-12p70 and IL-18, via recombinant adenoviral infection to generate an in vitro stimulus capable of promoting previously deficient patient Th1-type responses. Dendritic cells co-infected with Ad.IL-12 and Ad.IL-18 (DC.IL-12/18) were more effective at stimulating MAGE-A6-specific Th1-type CD4(+) T-cell responses than DCs infected with either of the cytokine vectors alone, control Ad.Psi5 virus or uninfected DCs. Furthermore, we show that DC.IL-12/18 loaded with recombinant MAGE-A6 protein (rMAGE) and used as in vitro stimulators promote Th1-type immunity that is frequently directed against multiple MAGE-A6-derived epitopes. The superiority of DC.IL-12/18-based stimulations in melanoma patients was independent of disease stage or current disease status. Based on these results, we believe this modality may prove clinically useful as a vaccine platform to promote the recovery of tumor antigen-specific, Th1-type CD4(+) T-cell responses in patients with cancer.

Sequential delivery of interferon-alpha gene and DCs to intracranial gliomas promotes an effective antitumor response

Effective presentation of tumor antigens by dendritic cells (DCs) is considered to be essential for the induction of antitumor T-cell responses. Apoptotic and necrotic tumors have been noted to be a robust antigen source for DCs. Because glioma cells undergo apoptosis after transfection with the type I interferon (IFN) gene and type I IFNs promote the stimulatory activity of DCs, we hypothesized that transfection of glioma cells with type I IFN genes and provision of DCs would promote particularly effective antitumor activity by both facilitating apoptosis of glioma cells and the presentation of the glioma antigens, thereby inducing specific immune responses against glioma cells. We have previously reported the proof of this hypothesis in vitro and in a subcutaneous tumor model. Here we report an extension of this approach in intracranial (i.c.) gliomas using adenoviral IFN-alpha (Ad-IFN-alpha) vector. Mice bearing day-5 i.c. GL261 glioma received sequential intratumoral (i.t.) delivery of Ad-IFN-alpha and bone marrow-derived syngeneic DCs. This treatment prolonged survival in that nine of 17 animals survived long term (> 60 days versus 0 of 10 control animals). Specific CTL activity was demonstrated following this regimen in the cervical lymph nodes, and the therapeutic efficacy was dependent upon CD8+ cells. Furthermore, these animals were protected against subsequent re-challenge with GL261 gliomas. DCs injected i.t. survived in the tumor and migrated into cervical lymph node. In vitro migration assays revealed the ability of DCs to migrate toward the tumor, suggesting that i.t. injected DCs migrate through the glioma. Taken together, this combination of gene therapy and cellular immunotherapy may be an effective future strategy for treating human gliomas.

Efficient bone formation by gene transfer of human LIM mineralization protein-3

LIM mineralization protein (LMP) is a novel positive regulator of the osteoblast differentiation program. In humans, three different LMP splice variants have been identified: LMP-1, LMP-2, and LMP-3. Gene transfer of human LMP-1 (hLMP-1) induces expression of genes involved in bone formation, including certain bone morphogenetic proteins (BMPs), promotes bone nodule formation in vitro, ectopic bone formation in vivo, and is therapeutic in animal models of posterior thoracic and lumbar spine fusion. To examine the osteoinductive properties of the LMP-3 in vitro and in vivo, we have generated plasmid and adenoviral vectors expressing codon-optimized hLMP-3. Here we demonstrate that gene transfer of hLMP-3 induces expression of the bone-specific genes osteocalcin, osteopontin, and bone sialoprotein and induced bone mineralization in preosteoblastic and fibroblastic cells. We also demonstrate that hLMP-3 is able to induce bone mineralization and the expression of the bone-specific genes, BMP-2, OSX, RunX2, and alkaline phosphatase in human mesenchymal stem cells in a dose-dependent manner. Finally, we demonstrate that direct gene transfer of hLMP-3 into murine skeletal muscle results in ectopic bone formation more efficiently than BMP-2. These results demonstrate that hLMP-3 gene transfer can be used to promote bone formation in cell culture and in vivo as or more efficiently than BMP-2, thus establishing feasibility and efficacy of direct gene delivery of hLMP-3 to produce bone in vivo. These results suggest that gene transfer of hLMP-3 could be developed as a bone-inductive therapeutic agent for clinical applications.

Human adenovirus type 35: nucleotide sequence and vector development

In this report, we describe the complete 34,794 base pair genomic sequence of the human adenovirus serotype 35 (Ad35) Holden strain. The viral genome exhibits a compact organization similar to other adenoviral serotypes, with overlapping genes on both strands. In all, 47 open reading frames (ORFs) were identified, including early (E1, 2, 3, 4) and late (L1, 2, 3, 4, 5) regions conserved among the adenoviridae family. In addition, 14 ORFs were identified that do not encode known adenoviral genes. Comparison of the predicted translational products of the conserved genes with those of other adenoviruses revealed that Ad35 has high homology to Ad7, Ad3, Ad21, Ad17, and simian Ads25. Based on the complete Ad35 DNA sequence, E3-, E1-, and E1/E3-deleted Ad35-based vector systems were developed. An HEK293-derived cell line was established for the propagation of the E1-deleted Ad35 vector, avoiding the emergence of replication-competent adenovirus. Moreover, production of the E1-deleted recombinant Ad35 vector was achieved by transient transduction of a plasmid encoding the Ad35 E1B gene in HEK293 cells. Testing showed that the Ad35-based vector efficiently infects both human and rhesus macaque dendritic cells. Our novel Ad35-based vectors and their corresponding packaging cell lines will provide a versatile and powerful system for DNA-based vaccine development and gene therapy applications.

Intra-articular adenoviral-mediated gene transfer of trail induces apoptosis of arthritic rabbit synovium

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that primarily affects joints. In rheumatoid joints there is extensive synovial proliferation with diseased synovium becoming highly aggressive, attaching to the articular cartilage and bone to form what is termed a pannus. The formation of active pannus is central to erosive disease and resulting joint destruction. In this study, we examined the ability to eliminate the hyperplastic synovium by adenoviral-mediated gene transfer of human TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF family that is able to induce apoptosis through interaction with receptors containing death domains, DR4 and DR5. Infection of synovial cells derived from RA patients with Ad.TRAIL resulted in significant apoptosis in three out of five lines. Moreover, primary rabbit synovial fibroblasts were also sensitive to Ad.TRAIL-mediated gene transfer. In a rabbit model of arthritis, intra-articular gene transfer of TRAIL induced apoptosis in cells within the synovial lining, reduced leukocytic infiltration and stimulated new matrix synthesis by cartilage. These results demonstrate that TRAIL can affect the viability of the cells populating the activated synovium in arthritic joints and suggest that the delivery of TRAIL to arthritic joints may represent a non-invasive mechanism for inducing pannus regression.

Genetic immunization with a melanocytic self-antigen linked to foreign helper sequences breaks tolerance and induces autoimmunity and tumor immunity

Mechanisms maintaining peripheral tolerance to self-antigens present a major obstacle for the development of antigen-specific melanoma vaccines, presumably because self-antigens are not able to stimulate a CD4 T-helper response. Using the melanosomal enzyme tyrosinase-related protein 2 (TRP2) expressed by melanocytes and most melanoma cells as a model self-antigen, we investigated whether linkage with a foreign immunogenic protein providing strong CD4 helper sequences would be able to circumvent tolerance and enhance the induction of antigen-specific tumor immunity. We found that genetic immunization of mice with cDNA encoding a fusion protein between enhanced green fluorescent protein (EGFP) from jellyfish and autologous murine TRP2 (EGFP.mTRP2) resulted in the stimulation of TRP2-reactive T cells in vivo. Importantly, immunization with EGFP.mTRP2 effectively protected mice against metastatic growth of B16 melanoma in the lungs and was associated with fur depigmentation as a sign of autoimmune-mediated destruction of melanocytes. Our results show that tumor vaccines consisting of self-antigens linked to immunogenic helper sequences can be successfully applied to the immunotherapy of melanoma and provide a scientific basis for the translation of this strategy in future clinical investigations.

Resistance to granzyme B-mediated cytochrome c release in Bak-deficient cells

Granzyme B (GrB), a serine protease with substrate specificity similar to the caspase family, is a major component of granule-mediated cytotoxicity of T lymphocytes. Although GrB can directly activate caspases, it induces apoptosis predominantly via Bid cleavage, mitochondrial outer membrane permeabilization, and cytochrome c release. To study the molecular regulators for GrB-mediated mitochondrial apoptotic events, we used a CTL-free cytotoxicity system, wherein target cells are treated with purified GrB and replication-deficient adenovirus (Ad). We report here that the Bcl-2 proapoptotic family member, Bak, plays a dominant role in GrB-mediated mitochondrial apoptotic events. A variant of Jurkat cells, deficient in Bak expression, was resistant to GrB/Ad-mediated apoptosis, as determined by lack of membranous phosphatidylserine exposure, lack of DNA breaks, lack of mitochondrial outer membrane permeabilization, and unchanged expression of inner mitochondrial membrane cardiolipin. The resistance of Bak-deficient cells to GrB/Ad cytotoxicity was reversed by transduction of the Bak gene into these cells. The requirement for both Bid and Bak, was further demonstrated in a cell-free system using purified mitochondria and S-100 cytosol. Purified mitochondria from Bid knockout mice, but not from Bax knockout mice, failed to release cytochrome c in response to autologous S-100 and GrB. Also, Bak-deficient mitochondria did not release cytochrome c in response to GrB-treated cytosol unless recombinant Bak protein was added. These results are the first to report a role for Bak in GrB-mediated mitochondrial apoptosis. This study demonstrates that GrB-cleaved Bid, which differs in size and site of cleavage from caspase-8-cleaved Bid, utilizes Bak for cytochrome c release, and therefore, suggests that deficiency in Bak may serve as a mechanism of immune evasion for tumor or viral infected cells.

A role for mitochondrial Bak in apoptotic response to anticancer drugs

In the present study a clonal Jurkat cell line deficient in expression of Bak was used to analyze the role of Bak in cytochrome c release from mitochondria. The Bak-deficient T leukemic cells were resistant to apoptosis induced by UV, staurosporin, VP-16, bleomycin, or cisplatin. In contrast to wild type Jurkat cells, these Bak-deficient cells did not respond to UV or treatment with these anticancer drugs by membranous phosphatidylserine exposure, DNA breaks, activation of caspases, or release of mitochondrial cytochrome c. The block in the apoptotic cascade was in the mitochondrial mechanism for cytochrome c release because purified mitochondria from Bak-deficient cells failed to release cytochrome c or apoptosis-inducing factor in response to recombinant Bax or truncated Bid. The resistance of Bak-deficient cells to VP-16 was reversed by transduction of the Bak gene into these cells. Also, the cytochrome c releasing capability of the Bak-deficient mitochondria was restored by insertion of recombinant Bak protein into purified mitochondria. Following mitochondrial localization, low dose recombinant Bak restored the mitochondrial release of cytochrome c in response to Bax; at increased doses it induced cytochrome c release itself. The function of Bak is independent of Bid and Bax because recombinant Bak induced cytochrome c release from mitochondria purified from Bax(-/-), Bid(-/-), or Bid(-/-) Bax(-/-) mice. Together, our findings suggest that Bak plays a key role in the apoptotic machinery of cytochrome c release and thus in the chemoresistance of human T leukemic cells.

Local high-capacity adenovirus-mediated mCTLA4Ig and mCD40Ig expression prolongs recombinant gene expression in skeletal muscle

Multiple forms of muscular dystrophy are due to the absence of cytoskeletal muscle proteins that normally protect the integrity of muscle cells. The lack of any adequate treatments for these devastating diseases propels research toward the development of strategies for gene delivery to skeletal muscle. High-capacity adenoviral vectors (HC-AdV) devoid of all viral coding sequences have been developed to avoid expression of viral proteins by the gene therapy vector. However, the capsid proteins that are an essential component of the input viral vector and any residual helper virus in the vector preparation could induce an immune response. Furthermore, the therapeutic protein provided by a gene transfer vector presents the potential to induce an immune response in a patient who does not express a normal cellular protein due to genetic mutation. Therefore, we hypothesize that some immune suppression will be required with therapeutic gene delivery designed for the treatment of patients with inherited muscle diseases. In this study, we constructed and rescued three HC-AdVs expressing murine CTLA4Ig, murine CD40Ig, or both. The backbone vector without a gene insert was rescued as a negative control vector. The production of relevant proteins from each vector was determined in vitro. In vivo function of each of the immunosuppressant vectors was assayed by co-injection with an enhanced green fluorescent protein (EGFP)-expressing first-generation adenoviral vector (AdEGFP) into the tibialis anterior muscle of C57BL/10 mice. Higher levels of muscle EGFP expression were observed in animals receiving an immunosuppressant vector. Furthermore, the production of total anti-AdV and anti-EGFP antibodies was reduced in mice treated with each of the three immunosuppressant vectors. A second intramuscular administration of AdEGFP alone 4 weeks after the initial co-injection was successful in all immunosuppressant vector-treated groups, but not in the negative control vector-treated group. All groups had a high antibody response to adenoviral proteins after the second injection of AdEGFP alone, indicating that the initial co-injection did not tolerize against vector capsid antigens.

Dendritic cells acquire antigens from live cells for cross-presentation to CTL

Dendritic cells (DC) can readily capture Ag from dead and dying cells for presentation to MHC class I-restricted CTL. We now show by using a primate model that DC also acquire Ag from healthy cells, including other DC. Coculture assays showed that fluorescently labeled plasma membrane was rapidly and efficiently transferred between DC, and transfer of intracellular proteins was observed to a lesser extent. Acquisition of labeled plasma membrane and intracellular protein was cell contact-dependent and was primarily a function of immature DC, whereas both immature and CD40L-matured DC could serve as donors. Moreover, immature DC could acquire labeled plasma membrane and intracellular proteins from a wide range of hemopoietic cells, including macrophages, B cells, and activated T cells. Notably, macrophages, which readily phagocytose apoptotic bodies, were very inefficient at acquiring labeled plasma membrane and intracellular proteins from other live macrophages or DC. With live-cell imaging techniques, we demonstrate that individual DC physically extract plasma membrane from other DC, generating endocytic vesicles of up to 1 microm in diameter. Finally, DC but not macrophages acquired an endogenous melanoma Ag expressed by live DC and cross-presented Ag to MHC class I-restricted CTL, demonstrating the immunological relevance of our finding. These data show for the first time that DC readily acquire Ag from other live cells. We suggest that Ag acquisition from live cells may provide a novel mechanism whereby DC can present Ag in the absence of direct infection, and may serve to expand and regulate the immune response in vivo.

Immunization with an antigen identified by cytokine tumor vaccine-assisted SEREX (CAS) suppressed growth of the rat 9L glioma in vivo

We have reported previously that s.c. immunization of rats with IL-4 transduced 9L gliosarcoma cells (9L-IL-4) induced a potent antitumor immunity against intracranial, parental 9L tumors. Subcutaneous implantation of 9L-IL-4 influenced the systemic humoral response, which was demonstrated by Th2-type isotype-switching and the induction of cellular immune responses, which played a critical role in the rejection of tumors. Serological analyses of recombinant cDNA expression libraries (SEREX), has recently emerged as a powerful method for serological identification of tumor-associated antigens (TAAs) and/or tumor rejection antigens (TRAs). Because IL-4 is known to activate B cells and to promote humoral responses, and inasmuch as induction of humoral responses by central nervous system tumors has been reported to be minimal, we investigated whether the induction of a potent humoral immune response against 9L TAAs or TRAs in rats immunized s.c. with 9L-IL4 could be demonstrated. Screening of 5 x 10(5) independent clones of 9L-expression cDNA library for the presence of reactive antibodies in the serum from a 91-IL-4 immunized rat led to the identification of three different TAAs. One 9L TAA (clone 29) was demonstrated to be calcyclin, a member of the S-100 family of calcium-binding proteins. The second 9L TAA (clone 37) was demonstrated to be the rat homologue of the J6B7 mouse immunomodulatory molecule. The third TAA (clones 158 and 171) was determined to be the rat homologue of the mouse Id-associated protein 1 (MIDA1), a DNA-binding, protein-associated protein. Northern blotting demonstrated that message for calcyclin was overexpressed in 9L cells. Message encoding MIDA1 was highly expressed in parental 9L cells and thymus and, to a lesser degree, in testis, suggesting that MIDA1 was comparable with the cancer/testis category of TAAs. Sera obtained from animals bearing 9L-IL-4 were found to have a higher a frequency and titer of antibodies to these antigens when compared with sera obtained from rats bearing sham-transduced 9L (9L-neo) cells. To determine whether immunization with these TAAs induced antitumor immunity, animals were immunized by intradermal injection with expression plasmids encoding calcyclin or MIDA1. Subsequent challenge of rats with parental 9L resulted in significant suppression of tumor growth in animals immunized with MIDA1, but not with calcyclin. These results indicate that MIDA1 is an effective 9L TRA and will be useful for the investigation of specific antitumor immunity in this glioma model. Furthermore, these results suggest that this approach, termed "cytokine-assisted SEREX (CAS)," may serve as an effective strategy for identification of TRAs for in animal-glioma models of cytokine gene therapy, and potentially in humans undergoing cytokine gene therapy protocols as well.

Immunogenicity of enhanced green fluorescent protein (EGFP) in BALB/c mice: identification of an H2-Kd-restricted CTL epitope

Enhanced green fluorescent protein (EGFP) is a novel marker gene product, which is readily detectable using techniques of fluorescence microscopy, flow cytometry, or macroscopic imaging. In the present studies, we have examined the immunogenicity of EGFP in murine models. A stable transfectant of the transplantable CMS4 sarcoma of BALB/c origin expressing EGFP, CMS4-EGFP-Zeo, was generated. Splenocytes harvested from mice immunized with a recombinant adenovirus expressing EGFP (Ad-EGFP) were restimulated in vitro with CMS4-EGFP-Zeo. Effector lymphocytes displayed strong cytotoxicity against CMS4-EGFP-Zeo, but not against mock-transfected CMS4-Zeo tumor cells. A number of candidate H2-Kd-binding peptides derived from the EGFP protein were chosen according to an epitope prediction program and synthesized. These peptides were tested for their ability to bind to H2-Kd molecules and stimulate IFNgamma-production by splenocytes harvested from Ad-EGFP-immunized mice. Using this methodology, the peptide, HYLSTQSAL (corresponding to EGFP200-208) which strongly binds to H2-Kd molecules, was identified as a naturally occurring epitope of EGFP. These results should facilitate the use of EGFP as a model tumor antigen in BALB/c mice.

Prevention of beta cell dysfunction and apoptosis activation in human islets by adenoviral gene transfer of the insulin-like growth factor I

Interleukin-1beta is a potent pro-inflammatory cytokine that has been shown to inhibit islet beta cell function as well as to activate Fas-mediated apoptosis in a nitric oxide-dependent manner. Furthermore, this cytokine is effective in recruiting lymphocytes that mediate beta cell destruction in IDDM onset. The insulin-like growth factor I (IGF-I) has been shown to block IL-1beta actions in vitro. We hypothesized that gene transfer of the insulin-like growth factor I to intact human islets could prevent IL-1beta-induced beta cell dysfunction and sensitization to Fas-triggered apoptosis activation. Intact human islets were infected with adenoviral vectors encoding IGF-I as well as beta-galactosidase and enhanced green fluorescent protein as controls. Adenoviral gene transfer of human IGF-I prevented IL-1beta-mediated nitric oxide production from human islets in vitro as well as the suppression of beta cell function as determined by glucose-stimulated insulin production. Moreover, IGF-I gene transfer prevented IL-1beta-induced, Fas-mediated apoptosis. These results suggest that locally produced IGF-I from cultured islets may be beneficial in maintaining beta cell function and promoting islet survival before and following islet transplantation as a potential therapy for type I diabetes.

Transduction of dendritic cells with Bcl-xL increases their resistance to prostate cancer-induced apoptosis and antitumor effect in mice

We have shown that prostate cancer (PCa) causes apoptosis of dendritic cells (DC), which might block the development of specific antitumor immune responses. Analysis of murine prostatic carcinoma tissues revealed the significant decrease in intratumoral DC number during tumor progression. We demonstrated that the cytokine-mediated increase in DC survival was accompanied by an elevated expression of the anti-apoptotic protein Bcl-xL. Next, we evaluated the resistance to tumor-induced apoptosis and the antitumor efficiency of genetically engineered DC overexpressing Bcl-xL. DC were transduced with an adenoviral vector encoding the murine Bcl-xL gene and injected intratumorally. Data analysis revealed that treatment of PCa-bearing mice with Bcl-xL-transduced DC resulted in significant inhibition of tumor growth compared with the administration of nontransduced DC. Thus, our data suggest that the protection of DC from PCa-induced apoptosis might significantly increase the efficacy of DC-based therapies in cancer even in the absence of available tumor-specific Ags.

Adenovirus-mediated gene therapy to liver grafts: successful gene transfer by donor pretreatment

BACKGROUND

We have previously shown excellent adenoviral (Ad) gene transfection to transplanted liver grafts with the clamp technique (CT) where viral vector was delivered ex vivo and trapped in cold preserved liver grafts. In this study, we adopted a new gene therapy approach to achieve early transgene expression by donor pretreatment with viral vector and compared the efficacy of these two methods by using Ad vector encoding enhanced green fluorescent protein (AdEGFP) marker gene.

METHODS

AdEGFP (1 x 10(9)plaque forming units) was delivered to the liver grafts by: (1) single intravenous injection to donor Lewis rats 48 hours before harvesting, (2) ex vivo cold infusion into the harvested liver with CT, or (3) a combination of both methods. Liver grafts were stored in University of Wisconsin solution at 4 degrees C for 18 hours and then orthotopically transplanted into syngeneic recipients, and the expression of EGFP was studied.

RESULTS

With intravenous pretreatment of donor liver grafts, EGFP-expressing cells were detected as early as 3 hours after transplant, and moderate expression was seen by 12 hours. In contrast, EGFP was not detected until 12 to 24 hours after transplant with CT. High levels of EGFP-producing cells were seen with each technique at 7 days ( approximately 30% transfection efficiency). A combination of both methods did not enhance infectivity. Liver preservation injury was comparable between groups.

CONCLUSIONS

Gene transfer by donor pretreatment with AdEGFP induces early and efficient gene transduction to liver grafts compared with back-table delivery with CT. This method is simple and provides early transgene expression in liver grafts that potentially could be used to deliver genes to decrease preservation injury or rejection.

Genetic approaches for biologic therapy of cancer

Recently, there has been an increase in the types of biological therapeutic approaches developed for the treatment of cancer. This rapid advance in the biological therapy of cancer is due in part to advances in the field of molecular and cell biology as well as in the development of gene transfer systems. In particular, a better understanding of the mechanism of antigen presentation and T lymphocyte activation has resulted in the development of new immunotherapeutic strategies targeting tumor-associated antigens (TAA). The discovery of dendritic cells (DC) as potent antigen presenting cells and the development of methods for their use in immunotherapeutic regimens has led to novel approaches for treating cancer. Furthermore, the identification of genes encoding TAA and their peptide products, which are recognized by T lymphocytes in the context of major histocompatibility complexes class I and class II molecules, has led to the development of DNA-based vaccines against defined tumor antigens. Cytokines have been shown to be important adjuvant tools for immunization protocols by directing a T helper response favorable for an adequate cytotoxic T lymphocyte-mediated immune response. Novel gene transfer technologies have made it possible to employ a wide range of gene delivery systems, either viral or nonviral based, in anticancer therapies. Current immunotherapeutic strategies, including the use of DC transduced with genes coding for tumor antigens and cytokines delivered by recombinant viral vectors, have shown promise in animal tumor models.

Dendritic cells transduced with an adenovirus vector encoding Epstein-Barr virus latent membrane protein 2B: a new modality for vaccination

Epstein-Barr virus (EBV) is a herpesvirus commonly associated with several malignancies, particularly in immunocompromised hosts. As a strategy for stimulating immunity against EBV for the treatment of EBV-associated tumors, we have genetically engineered dendritic cells (DC) to express EBV antigens, such as latent membrane protein 2B (LMP2B), using recombinant adenovirus vectors. CD8(+) T lymphocytes from HLA-A2.1(+), EBV-seropositive healthy donors were cultured with autologous DC infected with recombinant adenovirus vector AdEGFP, encoding an enhanced green fluorescent protein (EGFP), or AdLMP2B at a multiplicity of infection of 250. After 48 h, >95% of the DC were positive for EGFP expression as assessed by fluorescence-activated cell sorting analysis, indicating efficient gene transfer. AdLMP2-transduced DC were used to stimulate CD8(+) T cells. Responder CD8(+) T cells were tested for gamma interferon (IFN-gamma) release by enzyme-linked spot (ELISPOT) assay and cytotoxic activity. Prior to in vitro stimulation, the frequencies of T-cells directed against two HLA-A2-presented LMP2 peptides (LMP2 329-337 and LMP2 426-434) were very low as assessed by IFN-gamma spot formation (T-cell frequency, <0.003%). IFN-gamma ELISPOT assays performed at day 14 showed a significant (2-log) increase of the day 0 frequency of T cells reactive against the LMP2 329-337 peptide, from 0.003 to 0.3 (P < 0.001). Moreover, specific cytolytic activity was observed against the autologous EBV B-lymphoblastoid cell lines after 21 days of stimulation of T-cell responders with AdLMP2-transduced DC (P < 0.01). In summary, autologous mature DC genetically modified with an adenovirus encoding EBV antigens stimulate the generation of EBV-specific CD8(+) effector T cells in vitro, supporting the potential application of EBV-based adenovirus vector vaccination for the immunotherapy of the EBV-associated malignancies.

Dendritic cell-based genetic immunization in mice with a recombinant adenovirus encoding murine TRP2 induces effective anti-melanoma immunity

BACKGROUND

The induction of cellular immune responses to melanocyte-specific enzymes such as the tyrosinase family of proteins is the goal of various clinical studies for the immunotherapy of melanoma. Tyrosinase-related protein-2 (TRP2) is an attractive model antigen for preclinical studies in C57BL/6 mice because it is naturally expressed by the murine B16 melanoma and can be recognized by self-reactive cytolytic T lymphocytes (CTL). Here we describe efforts to develop genetic immunization with dendritic cells (DC) for the immunotherapy of melanoma in this clinically relevant system.

METHODS

Recombinant adenoviruses encoding green fluorescent protein (Ad-EGFP) and murine TRP2 (Ad-mTRP2) were constructed using Cre-loxP-mediated recombination. DC were generated in vitro from precursors in bone marrow and transduced with Ad-EGFP or Ad-mTRP2. Mice were immunized by direct injection of adenovirus or by injection of Ad-transduced DC. Induction of tumor immunity was assessed by intravenous challenge with B16 melanoma cells and enumeration of experimentally induced lung metastases.

RESULTS

Flowcytometric analysis of DC transduced with Ad-EGFP demonstrated endogenous fluorescence due to cytoplasmatic expression of EGFP in 30-60% of cells. Ad-EGFP-transduced DC simultaneously displayed the DC-specific marker NLDC145 and high levels of MHC and costimulatory molecules on their cell surface. Transduction of DC with Ad-mTRP2 resulted in strong intracellular expression of TRP2 which could be readily detected by immunostaining. Importantly, immunization of mice with cultured Ad-mTRP2-transduced DC completely prevented the development of lung metastases following an intravenous challenge with B16 melanoma cells. This striking protective effect was observed with both the intravenous and the subcutaneous route of DC immunization. In vivo depletion of T-cell subsets suggested that the protective effect of an immunization with Ad-mTRP2-transduced DC involved both CD8+ and CD4+ T-cells.

CONCLUSIONS

Our results demonstrate that DC-based genetic immunization of mice with TRP2, a clinically relevant melanocyte-specific self-antigen, induces effective cellular immunity and prevents metastatic growth of B16 melanoma cells in vivo.

Identification of naturally processed and HLA-presented Epstein-Barr virus peptides recognized by CD4(+) or CD8(+) T lymphocytes from human blood

The broad clinical implementation of cancer vaccines targeting the induction of specific T cell-mediated immunity is hampered because T cell defined tumor-associated peptides are currently available for only a restricted range of tumor types. Current epitope identification strategies require a priori the generation of T "indicator" cell lines that specifically recognize the tumor antigenic epitope in in vitro assay systems. An alternative to this strategy is the use of "memory" T cells freshly isolated from the peripheral blood of patients with cancer in concert with sensitive effector cell readout assays (such as the cytokine enzyme-linked immunospot assay) and MS to identify relevant peptide epitopes. In a model system, we have evaluated the capacity of natural Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell line-extracted peptides to activate "memory" viral-specific CD4(+) or CD8(+) T cells freshly isolated from the blood of an EBV-seropositive individual using the IFN-gamma enzyme-linked immunospot assay. After HPLC fractionation and loading onto autologous dendritic cells, multiple naturally processed HLA class I and II-associated lymphoblastoid cell line-derived peptides were isolated that were capable of inducing IFN-gamma spot production by "memory" T lymphocytes. Using MS analysis on a HPLC fraction recognized by CD8(+) T cells, we were able to sequence natural 9-, 10-, and 11-mer peptides naturally processed from the latent EBV antigen LMP-2 (latent membrane protein-2) and presented in the context of HLA-A2. This approach provides a useful methodology for the future identification of MHC-presented viral and tumor epitopes using freshly isolated patient materials.

Infection of intact human islets by a lentiviral vector

The transfer of genes encoding immunomodulatory proteins to islets can be used to improve islet function, block apoptosis, and inhibit rejection following transplantation. Adenoviral vectors have been shown to infect intact human islets, but the immunogenicity and transient gene expression of the current adenoviral vectors may hinder their use clinically for islet transplantation. In this report, we compared an HIV-1-based lentiviral vector with the E1-deleted adenoviral vehicle of the Ad5 type for gene transfer to human islets in vitro. We demonstrate that at similar viral particle concentrations per islet that an HIV-based lentiviral vector is able to infect beta-cells within an intact human islet at an efficiency similar to an adenoviral vector. In addition, both the adenoviral and lentiviral vectors were able to express significant levels of soluble interleukin-1 receptor antagonist (IL-1Ra) protein following infection of intact islets. More importantly, there was no impairment of islet beta-cell function following adenoviral and lentiviral infection in responding to glucose stimulation. These results support the utility of replication-defective lentiviral vectors as efficient gene delivery vehicles to islets to faciliate transplantation of islets for therapy of type I diabetes.

Adenoviral gene transfer of the interleukin-1 receptor antagonist protein to human islets prevents IL-1beta-induced beta-cell impairment and activation of islet cell apoptosis in vitro

The beta-cells in the pancreatic islets of Langerhans are the targets of autoreactive T-cells and are destroyed in type 1 diabetes. Macrophage-derived interleukin-1beta (IL-1beta) is important in eliciting beta-cell dysfunction and initiating beta-cell damage in response to microenvironmental changes within islets. In particular, IL-1beta can impair glucose-stimulated insulin production in beta-cells in vitro and can sensitize them to Fas (CD95)/FasL-triggered apoptosis. In this report, we have examined the ability to block the detrimental effects of IL-1beta by genetically modifying islets by adenoviral gene transfer to express the IL-1 receptor antagonist protein. We demonstrate that adenoviral gene delivery of the cDNA encoding the interleukin-1 receptor antagonist protein (IL-1Ra) to cultured islets results in protection of human islets in vitro against IL-1beta-induced nitric oxide formation, impairment in glucose-stimulated insulin production, and Fas-triggered apoptosis activation. Our results further support the hypothesis that IL-1beta antagonism in in situ may prevent intra-islet proinsulitic inflammatory events and may allow for an in vivo gene therapy strategy to prevent insulitis and the consequent pathogenesis of diabetes.

Direct adenoviral gene transfer of viral IL-10 to rabbit knees with experimental arthritis ameliorates disease in both injected and contralateral control knees

IL-10, a cytokine produced primarily by macrophages, B lymphocytes, and Th2 cells, has both immunostimulatory and immunosuppressive properties. A homologue of IL-10 encoded by EBV, known as viral IL-10 (vIL-10), is also able to suppress the immune response, but may lack some of the immunostimulatory properties of IL-10. To evaluate the potential of vIL-10 to block the progression of rheumatoid arthritis, we have utilized a replication-defective adenovirus vector to deliver the gene encoding vIL-10 to the knee joints of rabbits with Ag-induced arthritis. Intraarticular expression of vIL-10 significantly reduced leukocytosis, cartilage matrix degradation, and levels of endogenous rabbit TNF-alpha, as well as the degree of synovitis, while maintaining high levels of cartilage matrix synthesis. Interestingly, an antiarthritic effect was also observed in opposing contralateral control knee joints that received only a marker gene. An adenoviral vector carrying the enhanced green fluorescent protein marker gene was used to demonstrate that a morphologically similar subset of cells infected in the injected knee joint are able to traffic to the uninjected contralateral knee joint. Our results suggest that direct, local intraarticular delivery of the vIL-10 gene may have polyarticular therapeutic effects.

Inhibition of cytokine-induced nitric oxide synthase expression by gene transfer of adenoviral I kappa B alpha

BACKGROUND

Nitric oxide is overexpressed in nearly every organ during sepsis and it has profound biologic effects. Previously, we showed that maximal inducible nitric oxide synthase (iNOS) expression is up-regulated by a combination of cytokines and that this effect is mediated by the transcription factor NF-kappa B. Therefore the purpose of this study was to establish whether gene transfer of the inhibitory molecule I kappa B would result in the abrogation of cytokine-induced iNOS expression.

METHODS

Cultured hepatocytes were infected with an adenoviral vector containing the I kappa B alpha gene (Ad5I kappa B) and after an 18-hour recovery period were stimulated with the cytokine mixture of tumor necrosis factor-alpha (500 U/mL) plus interleukin 1 beta (200 U/mL) plus interferon gamma (100 U/mL).

RESULTS

As expected, cytokine mixture induced significant hepatocyte nitrite (NO2-) and iNOS messenger RNA production. Cells infected with the I kappa B alpha gene showed a dose-dependent decrease in NO2- and iNOS messenger RNA levels. Western blot analysis showed a marked decrease in iNOS protein levels in the presence of Ad5I kappa B alpha. Gel shift assays of nuclear extracts demonstrated that Ad5I kappa B alpha decreased the cytokine-induced DNA binding activity for NF kappa B.

CONCLUSIONS

NF kappa B is an important regulator of cytokine-induced NO expression. These results identify a novel therapeutic approach where gene transfer of the inhibitory molecule I kappa B alpha can be used to down-regulate cytokine-induced iNOS expression as well as other NF kappa B-dependent genes that are up-regulated during the inflammatory response.

Genetic engineering of dendritic cells to express immunosuppressive molecules (viral IL-10, TGF-beta, and CTLA4Ig)

There is growing evidence that, in addition to their role as initiators of immune responses, dendritic cells (DC) can exhibit tolerogenic properties. Immature DC deficient in cell surface costimulatory/accessory molecules can prolong organ and pancreatic islet allograft survival, whereas in vitro manipulation of DC by exposure to a variety of factors (e.g., viral interleukin-10; CTLA4Ig) can confer tolerogenic properties on these cells. Genetic engineering of DC to express immunosuppressive molecules is, in theory, an attractive approach to the therapy of allograft rejection and possibly, autoimmune disorders.

CD154 inhibits tumor-induced apoptosis in dendritic cells and tumor growth

We have recently demonstrated that murine and human tumors induce apoptosis of dendritic cells (DC). Here, we evaluated the effect of CD40 ligation on the survival of tumor-associated DC and tumor growth. Retroviral transduction of MC38 colon carcinoma cells with the CD154 gene resulted in inhibition of tumor growth. This effect was abrogated in IL-12 knockout mice. Immunohistochemical analysis revealed an increase in CD11c+ (N418) and CD8+ but not NLDC-145+ cells in CD154-transfected tumors in wild-type mice. This increase was less pronounced in IL-12-deficient mice. In vitro, overexpression of CD154 on tumor cells significantly decreased the level of tumor-induced DC apoptosis. Surprisingly, the CD154-induced protection of DC from tumor-induced apoptosis was IL-12 independent in vitro, suggesting an IL-12-dependent and an IL-12-independent mechanism of CD154-induced anti-tumor immunity. Thus, our data suggest a new strategy to improve immunotherapy of cancer by protecting DC from tumor-induced apoptosis.

Potent antitumor effects mediated by local expression of the mature form of the interferon-gamma inducing factor, interleukin-18 (IL-18)

IL-18 is produced during the acute immune response by macrophages and immature dendritic cells. IL-18 receptors are induced on T cells and NK cells by IL-12 and together they enhance a cellular immune response. We constructed retroviral and adenoviral vectors encoding the mature bioactive murine IL-18 in order to examine their immune and antitumor effects in murine tumor models. Secretion of bioactive IL-18 from murine tumor cells was facilitated by transfecting them with recombinant viral vectors carrying the prepro leader sequence of human parathyroid hormone fused to the 5' end of the mature murine IL-18 cDNA. Direct injection of the IL-18 recombinant adenoviral vector (Ad.PTH.IL-18) into an established MCA205 murine fibrosarcoma completely eradicated tumor in all animals with concomitant induction of protective systemic immunity. Co-administration of systemic IL-12 provided synergistic antitumor effects when combined with peritumoral injections of Ad.PTH.IL-18 without apparent side-effects as we observed with systemic administration of IL-18. Depletion of asialo GM-1+ cells completely abrogated the antitumor effects of Ad.PTH.IL-18, suggesting a major role for NK cells in mediating the anti-tumor effects of IL-18. Peritumoral injection of Ad.PTH.IL-18 was also associated with reduced numbers of CD8+ cells found within the tumor (HBSS versus Ad.PTH.IL-18, P < 0.0001). This suggests that IL-18 could be utilized as an alternative cancer gene therapy especially when combined with systemic administration of IL-12.

Adenoviral delivery of CTLA4Ig into myeloid dendritic cells promotes their in vitro tolerogenicity and survival in allogeneic recipients

Dendritic cells (DC) are highly specialized antigen-presenting cells (APC) that initiate and modulate immune responses. They are essential for naive T cell activation, but may also play roles both in central and peripheral tolerance. Blockade of costimulatory pathways that provide the crucial second signal for lymphocyte activation is one strategy to augment the potential tolerogenicity of DC. Here, in vitro propagated DC were transduced using an adenoviral (Ad) vector to express the gene encoding cytotoxic T lymphocyte antigen 4-immunoglobulin (CTLA4lg), which blocks interaction of CD80 and CD86 on DC with CD28 on T cells. Supernatants of AdCTLA4lg-transduced DC strikingly inhibited mixed leukocyte reactions (MLR) induced by non-transduced DC. Whereas transduction of marker genes (LacZ or enhanced green fluorescence protein (EGFP)) did not alter their potent allostimulatory activity, DC transduced with CTLA4lg exhibited striking reductions in cell surface staining for CD86, but not MHC class II, and were poor stimulators of T cell proliferation and cytotoxic T lymphocyte (CTL) responses. In addition, they induced alloantigen-specific T cell hyporesponsiveness. They were detected, following local injection, in significantly increased numbers in the lymphoid tissue of unmodified allogeneic recipients. This is the first report of the functional properties of DC genetically engineered to express CTLA4lg.

Co-delivery of T helper 1-biasing cytokine genes enhances the efficacy of gene gun immunization of mice: studies with the model tumor antigen beta-galactosidase and the BALB/c Meth A p53 tumor-specific antigen

DNA-based immunization is currently being investigated as a new method for the induction of cellular and humoral immunity directed against viral disease and cancer. In the present study we characterized and compared the immune responses induced in mice following particle-bombardment of the skin ('gene gun' immunization) with those elicited by intracutaneous injection of a recombinant adenoviral vector. Using the well characterized beta-galactosidase (beta gal) model Ag system we find that both in vivo gene transfer systems elicit potent and long-lasting anti-beta gal-specific CD8+ and CD4+ T cell responses. However, gene gun immunization predominantly promotes the production of anti-beta gal antibodies of the gamma 1 isotype, indicative of a Th2-biased immune response, while intradermal injection of recombinant adenovirus primarily leads to the production of anti-beta gal gamma 2a antibodies, indicative of a Th1-biased immune response. Since viral infections are generally associated with the production of large amounts of IFN-alpha and IL-12, we investigated whether administration of expression plasmids encoding these Th1-associated cytokines along with antigen-encoding cDNA can influence the nature of the immune response resulting from gene gun immunization. We observed that co-delivery of IFN-alpha or IL-12 resulted in increased production of anti-beta gal gamma 2a antibodies. This suggests a shift towards a Th1 phenotype of the resulting immune response, thus mimicking a viral infection. Importantly, gene gun immunization of mice with a naturally occurring tumor antigen, the tumor-specific p53 mutant antigen expressed by the chemically induced BALB/c Meth A sarcoma, required co-delivery of IL-12 for the induction of effective antitumor immunity. These results have important implications for the design of clinically relevant gene gun immunization strategies for tumor immunotherapy.

Induction of antitumor immunity by direct intratumoral injection of a recombinant adenovirus vector expressing interleukin-12

Direct intratumoral (i.t.) injection of adenoviruses (Ads) expressing specific immunostimulatory cytokines represents an attractive strategy for the clinical implementation of cytokine gene therapy of cancer. Interleukin-12 (IL-12) is a heterodimeric cytokine produced by antigen-presenting cells and promotes a T helper 1-like immune response. We have constructed an Ad vector (AdCMV-mIL-12) containing both chains of the murine IL-12 (mIL-12) gene linked by an internal ribosomal entry site sequence under the transcriptional control of the cytomegalovirus immediate-early gene promoter, which is able to mediate the transient expression of very high levels of biologically active mIL-12 both in vitro and in vivo. An i.t. injection of 4x10(8) plaque-forming units of AdCMV-mIL-12 resulted in a complete regression of day 7 established subcutaneous MC38 murine adenocarcinomas and MCA205 murine fibrosarcomas. Treated animals rejected a subsequent rechallenge with MC38 and MCA205, respectively, demonstrating the induction of long-lasting antitumor immunity. Specific antitumor cytotoxic T lymphocyte reactivity was detected in splenocytes harvested from treated animals. A significant increase in the numbers of both CD4+ and CD8+ T cells in the AdCMV-mIL-12-infected tumors was observed. Ad-mediated IL-12 gene therapy was also associated with measurable serum levels of mIL-12 and profound changes in the composition of splenic lymphocytes. Taken together, these results demonstrate the feasibility and efficacy of delivering IL-12 directly i.t. using a recombinant adenoviral vector.

Induction of tumor antigen-specific immunity using plasmid DNA immunization in mice

We have evaluated the ability of bioballistic "gene gun" immunization of mice with plasmid DNA encoding clinically relevant tumor antigens to induce protective antitumor immunity. Mice immunized with plasmid cDNA encoding the cervical carcinoma-associated human papillomavirus 16-E7 gene product exhibited potent anti-E7-specific cytotoxic T lymphocytes and were protected completely against a subsequent challenge with the E7+ C3 sarcoma. Of perhaps greater clinical interest, genetic immunization using cDNA encoding the normal, germline-encoded murine melanosomal protein tyrosinase-related protein-2 (TRP-2) resulted in delayed outgrowth of TRP-2+ B16 melanoma in mice and was associated with an in vivo activation of TRP-2-specific cytotoxic T lymphocytes. Codelivery of plasmid cDNA encoding TRP-2 and the T helper 1-biasing cytokine murine interleukin-12 considerably enhanced the antitumor efficacy of these gene-based melanoma vaccines.

Interferon-alpha gene therapy for cancer: retroviral transduction of fibroblasts and particle-mediated transfection of tumor cells are both effective strategies for gene delivery in murine tumor models

Stable transfection of tumor cells with IFN-alpha genes has been shown to result in abrogation of tumor establishment and induction of antitumor immunity. However, strategies suitable for the clinical application of IFN-alpha gene therapy for cancer have not been reported. In this study, we investigated two gene delivery systems capable of mediating the local paracrine production of high levels of biologically active IFN-alpha in murine tumor models: retroviral transduction of fibroblasts and particle-mediated transfection of tumor cells. In spite of the antiproliferative effects of IFN-alpha, it was possible to obtain stable retroviral producer cell lines and transduce a variety of murine tumor cells including syngeneic fibroblasts to stably secrete 2000-5000 U (40-100 ng) murine IFN-alpha/10(6) cells/24 h. IFN-alpha transduction of tumor cells abrogated tumorigenicity in establishment models and induced antitumor immunity in several murine tumor model systems. Importantly, IFN-alpha gene delivery using retrovirally transduced syngeneic fibroblasts was capable of suppressing the establishment of the poorly immunogenic TS/A mouse mammary adenocarcinoma and induced antitumor immunity. Particle mediated transient transfection of tumor cells using the gene gun led to the production of up to 20,000 U IFN-alpha/10(6) cells during the first 24 h and proved to be equally effective in suppressing establishment of TS/A adenocarcinoma and inducing antitumor immunity. These results suggest that retroviral transduction of autologous fibroblasts can serve as an effective gene delivery method for IFN-alpha gene therapy of cancer. Particle-mediated transfection of freshly isolated tumor cells may represent a clinically attractive alternative approach for nonviral gene delivery. Both strategies circumvent the difficulties in routinely establishing primary tumor cell lines from the vast majority of human cancers.

COACH syndrome: report of two brothers with congenital hepatic fibrosis, cerebellar vermis hypoplasia, oligophrenia, ataxia, and mental retardation

Congenital hepatic fibrosis (CHF) is probably the most common cause of non-icteric hepatosplenomegaly and is encountered mainly in children and young adults. We describe here two brothers from healthy, non-consanguineous parents. The patients showed early hepatosplenomegaly, portal hypertension, and no apparent kidney involvement. Clinical and laboratory findings were similar in both patients. Liver biopsies showed the presence of broad septa of fibrous tissue containing abundant bile ducts, portal tracts enlarged by fibrosis, and preserved lobular architecture. The histological findings were suggestive of CHF. Ophthalmological assessment demonstrated visual impairment with mild exotropia, nystagmus, and oculomotor apraxia. Neurological examination showed moderate mental retardation and cerebellar ataxia. Brain MRI confirmed cerebellar malformation with inferior vermis hypoplasia. This pattern of defects is consistent with COACH syndrome (Cerebellar vermis hypoplasia, Oligophrenia, congenital Ataxia, Coloboma, Hepatic fibrocirrhosis) which has previously been reported in five other cases. Our report may contribute to a better delineation of the COACH syndrome phenotype in the spectrum of oculo-encephalohepato-renal disorders.