Modified Ad Vector Research Articles

Adenovirus Vector-Induced IL-6 Promotes Leaky Adenoviral Gene Expression, Leading to Acute Hepatotoxicity.

Adenovirus (Ad) vector-mediated transduction can cause hepatotoxicity during two phases, at ∼2 and 10 days after administration. Early hepatotoxicity is considered to involve inflammatory cytokines; however, the precise mechanism remains to be clarified. We examined the mechanism of early Ad vector-induced hepatotoxicity by using a conventional Ad vector, Ad-CAL2, and a modified Ad vector, Ad-E4-122aT-CAL2. Ad-E4-122aT-CAL2 harbors sequences complementary to the liver-specific miR-122a in the 3' untranslated region of E4, leading to significant suppression of leaky Ad gene expression in the liver via posttranscriptional gene silencing and a significant reduction in late-phase hepatotoxicity. We found that Ad-E4-122aT-CAL2 transduction significantly attenuated acute hepatotoxicity, although Ad-E4-122aT-CAL2 and Ad-CAL2 induced comparable cytokine expression levels in the liver and spleen. IL-6, a major inflammatory cytokine induced by Ad vectors, significantly enhanced leaky Ad gene expression and cytotoxicity in primary mouse hepatocytes following Ad-CAL2 but not Ad-E4-122aT-CAL2 transduction. Furthermore, leaky Ad gene expression and cytotoxicity in Ad-CAL2-treated hepatocytes in the presence of IL-6 were significantly suppressed upon inhibition of JAK and STAT3. Ad vector-mediated acute hepatotoxicities and leaky Ad expression were significantly reduced in IL-6 knockout mice compared with those in wild-type mice. Thus, Ad vector-induced IL-6 promotes leaky Ad gene expression, leading to acute hepatotoxicity.

Epitope Capsid-Incorporation: New Effective Approach for Vaccine Development for Chagas Disease

Background:Previously we reported that a hexon-modified adenovirus (Ad) vector containing the invasive neutralizing epitope of Trypanosoma cruzi (T. cruzi) trypomastigote gp83 (Ad5-gp83) provided immunoprotection against T. cruzi infection. The purpose of this work was to design an improved vaccine for T. cruzi using a novel epitope capsid incorporation strategy. Thus, we evaluated the immunoprotection raised by co-immunization with Ad5-gp83 and an Ad vector containing an epitope (ASP-M) of the T. cruzi amastigote surface protein 2.Methods:Protein IX (pIX)-modified Ad vector (Ad5-pIX-ASP-M) was generated, characterized, and validated. C3H/He mice were immunized with Ad5-pIX-ASP-M and Ad5-gp83 and the cell-mediated responses were evaluated by enzyme-linked immunospot (ELISPOT) assay and intracellular staining. Immunized mice were challenged with T. cruzi to evaluate the vaccine efficacy.Results:Our findings indicate that Ad5-pIX-ASP-M was viable. Specific CD8+ T-cell mediated responses prior to the challenge show an increase in IFNγ and TNFα production. A single immunization with Ad5-pIX-ASP-M provided protection from T. cruzi infection, but co-immunizations with Ad5-pIX-ASP-M and Ad5-gp83 provided a higher immunoprotection and increased survival rate of mice.Conclusions:Overall, these results suggest that the combination of gp83 and ASP-M specific epitopes onto the capsid-incorporated adenoviruses would provide superior protection against Chagas disease as compared with Ad5-gp83 alone.

Towards Gene Therapy of Postoperative Adhesions: Fiber and Transcriptional Modifications Enhance Adenovirus Targeting towards Human Adhesion Cells

Postoperative abdominal/pelvic peritoneal adhesions are a major source of morbidity (bowel obstruction, infertility, ectopic gestation as well as chronic pelvic pain) in women. In this study, we screened various transduction and transcription modifications of adenovirus (Ad) to identify those that support maximal Ad-mediated gene delivery to human adhesion fibroblasts, which in turn would enhance the efficacy of this novel treatment/preventative strategy for postoperative adhesions. We transduced primary cultures of human peritoneal adhesion fibroblasts with fiber-modified Ad vectors Ad5-RGD-luc, Ad5-Sigma-luc, Ad5/3-luc and Ad5-CAV2-luc as well as transcriptional targeting viruses Ad5-survivin-luc, Ad5-heparanase-luc, Ad5-mesothelin (MSLN)-CRAd-luc and Ad5-secretory leukoprotease inhibitor (SLPI)-luc, and compared their activity to wild-type Ad5-luc. At 48 h, luciferase activity was measured and normalized to the total protein content in the cells. Among the fiber-modified Ad vectors, Ad5-Sigma-luc and among the transcriptional targeting modified Ad vectors, Ad5-MSLN-CRAd-luc showed significantly increased expression levels of luciferase activity at 5, 10 and 50 plaque forming units/cell in adhesion fibroblast cells compared with wild-type Ad5-luc (p < 0.05). Specific modifications of Ad improve their gene delivery efficiency towards human peritoneal adhesion fibroblasts. Developing a safe localized method to prevent/treat postoperative adhesion formation would have a major impact on women health.

Enzyme-responsive liposomes modified adenoviral vectors for enhanced tumor cell transduction and reduced immunogenicity

Limitations of adenoviral (Ad) vectors for cancer gene therapy could be overcome by their combination with pharmaceutical technologies. Here we show that an enzyme-responsive liposomal formulation could significantly enhance the tumor cell transduction abilities and reduce the immunogenicity of Ad vectors. In the current research, the enzymatically cleavable PEG-lipids composed of a PEG/matrix metalloproteinase (MMP)-substrate peptide/cholesterol (PPC) were synthesized and characterized by 1H NMR and TOF MS ES+. The obtained MMP-cleavable lipids were inserted into the anionic liposomal Ad vectors (AL-Ad) by the post-insertion method. The results of in vitro infection assays indicated that the enzymatically cleavable formulation (PPC-AL-Ad) displayed a much higher gene expression than naked Ad5 and the non-cleavable PEG-lipid modified Ad vectors in tumor cells. More importantly, PPC-AL-Ad induces a lower production of neutralizing antibody and lower innate immune response, as well as significantly reduced liver toxicity in vivo. These findings suggest that PPC-AL-Ad is a promising system for gene delivery in tumor therapy.

A paclitaxel-conjugated adenovirus vector for targeted drug delivery for tumor therapy

Tumor-targeted drug delivery is an attractive strategy in cancer treatment. Our previous study demonstrated that modified adenovirus has strong tumor targeting ability and less toxicity to surrounding normal tissue. In this study, Paclitaxel (PTX), a widely used clinical anticancer drug, was conjugated to folate-modified adenovirus (Ad) nanoparticles by using succinic anhydride and Fmoc-Glu(OtBu)–OH linkers to form two prodrugs, FA-Ad-Suc-PTX and FA-Ad-ICG02-Glu-PTX. Near-infrared (NIR) fluorescent dye ICG-Der-02 was attached to –NH 2–Glu(OtBu)-PTX for in vivo optical imaging. In vitro and acute toxicity study demonstrates the low toxicity of the prodrug FA-Ad-Suc-PTX and FA-Ad-ICG02-Glu-PTX compared to the free drug. The dynamic behaviors and targeting ability of FA-Ad-ICG02-Glu-PTX on MDA-MB-231 tumor-bearing mice were investigated by NIR fluorescence imaging. The result show that PTX-conjugated Ad vector could enhance the targeting and residence time in tumor site. In vitro and in vivo studies demonstrate that Coxsackie adenovirus receptor (CAR) or foliate receptor (FR)-mediated uptake of FA-Ad-loaded PTX induced highly anti-tumor activity. The results support the potential of using chemically modified Ad vector as drug-loaded tumor-targeting delivery system.

Adenoviral Producer Cells

Adenovirus (Ad) vectors, in particular those of the serotype 5, are highly attractive for a wide range of gene therapy, vaccine and virotherapy applications (as discussed in further detail in this issue). Wild type Ad5 virus can replicate in numerous tissue types but to use Ad vectors for therapeutic purposes the viral genome requires modification. In particular, if the viral genome is modified in such a way that the viral life cycle is interfered with, a specific producer cell line is required to provide trans-complementation to overcome the modification and allow viral production. This can occur in two ways; use of a producer cell line that contains specific adenoviral sequences incorporated into the cell genome to trans-complement, or use of a producer cell line that naturally complements for the modified Ad vector genome. This review concentrates on producer cell lines that complement non-replicating adenoviral vectors, starting with the historical HEK293 cell line developed in 1977 for first generation Ad vectors. In addition the problem of replication-competent adenovirus (RCA) contamination in viral preparations from HEK293 cells is addressed leading to the development of alternate cell lines. Furthermore novel cell lines for more complex Ad vectors and alternate serotype Ad vectors are discussed.

Lac-regulated system for generating adenovirus 5 vaccine vectors expressing cytolytic human immunodeficiency virus 1 genes

Adenovirus (Ad) vectors have been developed as human immunodeficiency-1 (HIV-1) vaccine vectors because they consistently induce immune responses in preclinical animal models and human trials. Strong promoters and codon-optimization are often used to enhance vaccine-induced HIV-1 gene expression and immunogenicity. However, if the transgene is inherently cytotoxic in the cell line used to produce the vector, and is expressed at high levels, it is difficult to rescue a stable Ad HIV-1 vaccine vector. Therefore we hypothesized that generation of Ad vaccine vectors expressing cytotoxic genes, such as HIV-1 env, would be more efficient if expression of the transgene was down-regulated during Ad rescue. To test this hypothesis, a Lac repressor–operator system was applied to regulate expression of reporter luciferase and HIV-1 env transgenes during Ad rescue. The results demonstrate that during Ad rescue, constitutive expression of the Lac repressor in 293 cells reduced transgene expression levels to approximately 5% of that observed in the absence of regulation. Furthermore, Lac-regulation translated into more efficient Ad rescue compared to traditional 293 cells. Importantly, Ad vectors rescued with this system showed high levels of transgene expression when transduced into cells that lack the Lac repressor protein. The Lac-regulated system also facilitated the rescue of modified Ad vectors that have non-native receptor tropism. These tropism-modified Ad vectors infect a broader range of cell types than the unmodified Ad, which could increase their effectiveness as a vaccine vector. Overall, the Lac-regulated system described here (i) is backwards compatible with Ad vector methods that employ bacterial-mediated homologous recombination, (ii) is adaptable for the engineering of tropism-modified Ad vectors, and (iii) does not require co-expression of regulatory genes from the vector or the addition of exogenous chemicals to induce or repress transgene expression. This system therefore could facilitate the development of Ad-based vaccine candidates that otherwise would not be feasible to generate.

Construction of Adenovirus Vectors with RGD-Modified Fiber for Transductional Targeting

INTRODUCTIONTherapeutic gene transfer strategies aim to maximize gene transfer and expression in target cells. However, gene delivery systems often fail to preferentially transduce target cells in mixed cell populations. In addition, limitations in vector specificity can lead to transduction of non-target cells, resulting in untoward toxicity, even with compartmental dosing. Thus, vector optimization is critical for the development of efficient genetic experiments. The life cycle and biology of adenovirus (Ad) infection and transgene expression in cells have been thoroughly characterized. Ad infection is initiated by recognition of the native Ad5 receptor, coxsackievirus-adenovirus receptor (CAR), on target cells by the carboxy-terminal portion (i.e., knob) of the fiber protein. The development of genetically modified Ad vectors with transductional specificity for a single cell type requires “retargeting”: the ablation of endogenous tropism and the introduction of novel tropism determinants for target cells. This protocol describes the construction of chimeric fibers. Homologous recombination between the pAdEasy-1 and the fiber shuttle plasmid (pFiber-dE3-RGD) is used to generate a rescue plasmid with a mutant fiber that inserts Arg-Gly-Asp (RGD) at the carboxyl terminus of the fiber knob region. The resultant fiber-modified rescue plasmid (pAdEasy-RGD) is isogenic to AdEasy-1 (except the fiber region) and can therefore be used for another round of homologous recombination with pShuttle-promoter-Luc to make a final Ad vector construct that expresses the luciferase gene and contains an RGD-modified fiber knob. This construct can then be tested for targeting efficacy against cells expressing αv integrin cell surface receptors.

Construction of Adenovirus Vectors for Transcriptional Targeting

INTRODUCTIONThe balance between target and nontarget cell toxicity determines the efficacy of any therapeutic agent. Therapeutic gene transfer strategies aim to maximize gene transfer and expression in target cells. However, gene delivery systems often fail to preferentially transduce target cells in mixed cell populations. In addition, limitations in vector specificity can lead to transduction of nontarget cells, resulting in untoward toxicity, even with compartmental dosing. Thus, vector optimization is critical for the development of efficient genetic experiments. The life cycle and biology of adenovirus (Ad) infection and transgene expression in cells have been thoroughly characterized. While genetically modified Ad vectors with transductional specificity for a single cell type can be generated by direct or indirect modifications of the carboxyl terminus of the vectors’ receptor recognition site, Ad vectors can also be targeted at the level of protein expression of the transgene in the targeted cells (i.e., transcription/translation). Target-cell-specific gene expression is accomplished using tissue-specific promoters (TSPs), DNA elements that restrict expression to specific cellular subsets. The major drawback of transcriptional retargeting is that pathological change in target tissues or organs, such as degeneration or malignant transformation, can ectopically activate TSPs. In this protocol, recombinant Ad vectors that express the luciferase gene are constructed through homologous recombination in Escherichia coli. TSPs are placed in front of the luciferase gene for selective expression.

Construction of Fusion Proteins for Transductional Targeting: Figure 1.

INTRODUCTIONTherapeutic gene transfer strategies aim to maximize gene transfer and expression in target cells. However, gene delivery systems often fail to preferentially transduce target cells in mixed cell populations. In addition, limitations in vector specificity can lead to transduction of nontarget cells, resulting in untoward toxicity, even with compartmental dosing. Thus, vector optimization is critical for the development of efficient genetic experiments. The life cycle and biology of adenovirus (Ad) infection and transgene expression in cells have been thoroughly characterized. Ad infection is initiated by recognition of the native Ad5 receptor, coxsackievirus-adenovirus receptor (CAR), on target cells by the carboxy-terminal portion (i.e., knob) of the fiber protein. The development of genetically modified Ad vectors with transductional specificity for a single cell type requires “retargeting:” the ablation of endogenous tropism and the introduction of novel tropism determinants for target cells. One strategy for accomplishing such retargeting does so indirectly, by using bifunctional adapter molecules. One element of the bispecific adapter binds to the Ad fiber knob, blocking its interaction with CAR and, thus, its native tropism. The second component of the adapter introduces specificity for the target cells and is chemically or genetically conjugated to the knob-binding portion. Recombinant fusion proteins offer a number of technological advantages over chemical conjugates, including simplified production and purification. In this protocol, a recombinant fusion protein is generated that ablates the vector’s native tropism by blocking the CAR receptor and retargets the vector to cells expressing epidermal growth factor (EGF).

Assessment of Genetic Shielding for Adenovirus Vectors

Development of adenovirus (Ad) vectors in the clinical context has highlighted that vector efficacy may be limited by the host humoral response due to pre-existing titers of neutralizing antibodies against the vector itself in humans. Further, multiple dosing of Ad vectors based on serotype 5 would be limited. Current immune evasion strategies being investigated by other laboratories are only applicable to non-replicating vectors. Therefore we have proposed ge- netic shielding as an alternate that would be applicable to both non-replicating and conditionally replicating Ad vectors. Genetic shielding would encapsulate fusion of a self-protein to Ad minor capsid protein, pIX, as a means to cloak immu- nogenic capsid epitopes and prevent neutralization of Ad vectors through Ad specific antibodies. In the development of a suitably shielded Ad vector we choose several self-proteins that we attempted to fuse to pIX. We have also used an indirect method to conjugate albumin to the capsid through an albumin binding domain fused to pIX. Despite attaining novel pIX modified Ad vectors we found that none of the pIX attached molecules in this study prevented neutralizing an- tibodies from halting gene transfer.

321. Twenty-Fold Increased In Vivo Liver Gene Transfer with a Geneti-Chemically Modified Ad Vector Carrying a High-Affinity Protein Ligand on the Hexon Capsomere

321. Twenty-Fold Increased In Vivo Liver Gene Transfer with a Geneti-Chemically Modified Ad Vector Carrying a High-Affinity Protein Ligand on the Hexon Capsomere

Modification of pIX or hexon based on fiberless Ad vectors is not effective for targeted Ad vectors

Adenovirus (Ad) vector application in gene therapy is limited by its naïve tropism. We previously developed protein IX (pIX)-modified and hexon-modified Ad vectors in order to alter Ad vector tropism. However, these modified Ad vectors failed to infect cells with the foreign ligands displayed in the pIX or hexon. We hypothesized that steric hindrance by fiber proteins might have prevented the ligand-mediated transduction, as fibers are the outmost capsid proteins of Ad vectors. Therefore, we generated a series of fiberless Ad vectors and investigated their gene expression properties. Unexpectively, however, pIX- or hexon-modified fiberless Ad vector did not achieve any gene expression (the gene expression level by these vectors was similar to the background level). These results might be caused by the fact that the fiberless particles were weaker against physical burdens. To the best of our knowledge, this study is the first reported attempt to develop fiberless Ad vectors containing foreign ligands in the pIX or hexon region. The drawback of the lower stability of fiberless Ad vectors must be overcome to develop targeted Ad vectors based on such vectors. This study could provide basic information for the development of effective targeted Ad vectors.

Gene delivery into malignant glioma by infectivity-enhanced adenovirus: In vivo versus in vitro models

Adenoviral (Ad) vectors demonstrate several attributes of potential utility for glioma gene therapy. Although Ad infection is limited in vitro by low expression levels of the coxsackie-adenoviral receptor (CAR), in vivo studies have shown the efficacy of Ad vectors as gene delivery vectors. To evaluate the in vivo utility of CAR-independent, infectivity-enhanced Ad vectors, we employed genetically modified Ad vectors in several experimental models of human gliomas. We used three capsid-modified Ad vectors: (1) a chimeric Ad vector with a human Ad backbone and a fiber knob of a canine Ad, (2) an Ad vector with a polylysine motif incorporated into the fiber gene, and (3) a double-modified Ad vector incorporating both an RGD4C peptide and the polylysine motif. These three modified Ad vectors target, respectively, the putative membrane receptor(s) of the canine Ad vector, heparan sulfate proteoglycans (HSPGs), and both integrins and HSPGs. Our in vitro studies indicated that these retargeting strategies all enhanced CAR-independent infectivity in both established and primary low-passage glioma cells. Enhancement of in vitro gene delivery by the capsid-modified vectors correlated inversely with the levels of cellular CAR expression. However, in vivo in orthotopic human glioma xenografts, the unmodified Ad vector was not inferior relative to the capsid-modified Ad vector. Although genetic strategies to circumvent CAR deficiency in glioma cells could reproducibly expand the cellular entry mechanisms of Ad vectors in cultured and primary glioma cells, these approaches were insufficient to confer in vivo significant infectivity enhancement over unmodified Ad vectors. Other factors, probably the extracellular matrix, stromal cells, and the three-dimensional tumor architecture, clearly play important roles in vivo and interfere with Ad-based gene delivery into glioma tumors.

Mesenchymal stem cells selectively engraft into tumor stroma and produce potent antitumor proteins in situ

3025 Background: The formation of stroma is essential for tumor growth and involves complex interactions between malignant cells and non-tumor stromal cells. We have previously demonstrated that IV injected bone marrow derived mesenchymal stem cells (MSC) integrate into solid tumors as stromal elements (Cancer Res 62:3603, 2002; JNCI 96:1593, 2004). Methods: MSC were labeled by a fiber modified Ad vector expressing firefly luciferase (AdLux-F/RGD), injected into normal or tumor-bearing SCID mice, and biodistributed MSC-Lux were imaged utilizing the Xenogen IVIS system. Results: After IP injection, no hMSC-LUX were detected in normal animals after 7 days, while strong punctate regions of LUX-activity were observed in ovarian tumors. Tumor cells transduced with renilla luciferase constructs co- localized with firefly luciferase MSC. Next, we examined whether hMSC-producing interferon-beta (IFNβ-MSC) could inhibit the growth of metastatic tumors in the lungs of SCID mice. When injected IV (4 doses of 106 MSC/week) into SCID mice with pulmonary metastases of carcinomas or melanomas, tumor growth was significantly inhibited as compared with untreated or vector-control MSC controls (p= 0.007). IV injected IFNb-MSC prolonged the survival of mice bearing metastatic breast carcinomas (p=0.001). In an orthotopic, chemoresistant breast cancer model in syngeneic immunocompetent mice, MSC producing IFN-β completely abrograted tumor growth. Localized low-dose XRT to tumors significantly increased the number of tumor-resident MSC. Conclusions: The data suggest that systemically administered gene-modified MSC selectively engraft into the tumor microenvironment and remain resident as part of the tumor architecture. MSC-expressing IFN-β inhibit the growth of melanomas, gliomas, metastatic breast and ovarian cancers in vivo and prolong the survival of mice bearing established tumors. Clinical trials are in preparation. No significant financial relationships to disclose.

Fiber-Modified Adenovirus Vectors Decrease Liver Toxicity through Reduced IL-6 Production

Adenovirus (Ad) vectors are one of the most commonly used viral vectors in gene therapy clinical trials. However, they elicit a robust innate immune response and inflammatory responses. Improvement of the therapeutic index of Ad vector gene therapy requires elucidation of the mechanism of Ad vector-induced inflammation and cytokine/chemokine production as well as development of the safer vector. In the present study, we found that the fiber-modified Ad vector containing poly-lysine peptides in the fiber knob showed much lower serum IL-6 and aspartate aminotransferase levels (as a maker of liver toxicity) than the conventional Ad vector after i.v. administration, although the modified Ad vector showed higher transgene production in the liver than the conventional Ad vector. RT-PCR analysis showed that spleen, not liver, is the major site of cytokine, chemokine, and IFN expression. Splenic CD11c(+) cells were found to secret cytokines. The tissue distribution of Ad vector DNA showed that spleen distribution was much reduced in this modified Ad vector, reflecting reduced IL-6 levels in serum. Liver toxicity by the conventional Ad vector was reduced by anti-IL-6R Ab, suggesting that IL-6 signaling is involved in liver toxicity and that decreased liver toxicity of the modified Ad vector was due in part to the reduced IL-6 production. This study contributes to an understanding of the biological mechanism in innate immune host responses and liver toxicity toward systemically administered Ad vectors and will help in designing safer gene therapy methods that can reduce robust innate immunity and inflammatory responses.

Mesenchymal Stem Cells Selectively Engraft into Tumor Stroma and Produce Potent Antitumor Proteins In Situ.

The formation of stroma is essential for tumor growth and involves complex interactions between malignant tumor cells, and non-tumor stromal cells. We have previously demonstrated that mesenchymal stem cells (MSC) integrate into solid tumors as stromal elements (Cancer Res 62:3603, 2002; JNCI 96:1593, 2004,), suggesting the development of anti-cancer therapies based on the intratumoral production of agents by gene-modified MSC. However, no direct evidence has demonstrated this migration and selective engraftment into the tumor microenvironment. Therefore, we noninvasively visualized MSC using luciferase bioluminescence. MSC were labeled by a fiber modified Ad vector expressing firefly luciferase (AdLux-F/RGD) and these MSC-Lux were injected into normal (healthy) SCID mice or mice bearing established metastatic breast or ovarian tumors. Biodistributed MSC-Lux were imaged utilizing the Xenogen IVIS detection system. In normal mice, human MSC (hMSC) migrated to the lungs where they remained resident for 7–10 days. In animals bearing established metastatic lung tumors, IV injected hMSC again migrated to the lungs. However, in contrast to control mice, the Lux signal remained strong over a 15-day period with only a slight decrease over the first 10 days. After IP injection, hMSC-LUX were detected in the peritoneum, and after 7 days, no hMSC-LUX was detected in normal animals, while strong punctate regions of LUX-activity were observed in ovarian tumors. In contrast to SCID mice injected with hMSC, healthy Balb/C mice injected with Balb/C derived MSC-LUX initially migrated to the lungs and within 2.5 hrs had exited the lungs to remain liver and spleen resident for 5–7 days. When tumor cells were transduced with renilla luciferase constructs, the co-localization and dynamic interactions of firefly luciferase MSC and renilla luciferase tumors could be examined in detail. Mechanisms regulating the MSC-tumor interactions involve TGF-beta, HGF/c-Met, and EGFR and will be discussed. We then examined whether hMSC-producing interferon-beta (IFNb-MSC) could inhibit the growth of metastatic tumors in the lungs of SCID mice. When injected IV (4 doses of 106 MSC/week) into SCID mice bearing pulmonary metastases of carcinomas or melanomas, tumor growth was significantly inhibited as compared to untreated or vector-control MSC controls (p= 0.007), while recombinant IFNb protein (50,000 IU qod) was ineffective (p=0.14). IV injected IFNb-MSC prolonged the survival of mice bearing metastatic breast carcinomas (p=0.001) Intraperitoneal (IP) injections of IFN-MSC into mice carrying ovarian carcinomas resulted in doubling of survival in SKOV-3, and cures in 70% of mice carrying OVAR-3 tumors. MSC injected into the ipsilateral or contralateral carotid artery were found to localize to glioma xenografts in mice and IFNb-MSC significantly (p<0.05) prolonged survival of these mice. These data suggest that systemically administered gene-modified MSC selectively engraft into the tumor microenvironment and remain resident as part of the tumor architecture. MSC-expressing IFN-b inhibit the growth of melanomas, gliomas, metastatic breast and ovarian cancers in vivo and prolong the survival of mice bearing established tumors. Clinical trials are in preparation.

Characterization of capsid-modified adenovirus vectors containing heterologous peptides in the fiber knob, protein IX, or hexon

Adenovirus (Ad) vectors are widely used in gene therapy and in vitro/in vivo gene transfer because of their high transduction efficiency. However, Ad vector application in the gene therapy field is limited by poor transduction into cells not expressing the primary receptor, coxsackievirus and adenovirus receptor. To overcome this problem, several types of capsid-modified Ad vectors have been developed. The HI loop or C-terminus of the fiber knob, the C-terminus of the protein IX (pIX) and the hypervariable region 5 of the hexon are promising candidate locations for displaying foreign peptide sequences. In the present study, we constructed Ad vectors in which each of the above region was modified by a simple in vitro ligation-based method, and examined the characterization of each Ad vector containing the FLAG tag (DYKDDDDK) or RGD (CDCRGDCFC) peptide. Enzyme-linked immunosorbent assay examining the surface expression of foreign peptides on the virus suggested that foreign peptides are exposed on virion surfaces in all types vectors and that the hexon was the most efficiently reacted, reflecting the copy number of the modification. However, in the case of the transduction efficiency of Ad vectors containing the RGD peptides, the modification of pIX and the hexon showed no effect. The modification of the HI loop of the fiber knob was the most efficient, followed by the modification of the C-terminus region of the fiber knob. These comparative analyses, together with a simple construction method for each modified Ad vector, could provide basic information for the generation of capsid-modified Ad vectors.

Modified Adenoviral Vectors Ablated for Coxsackievirus–Adenovirus Receptor,αv Integrin, and Heparan Sulfate Binding ReduceIn VivoTissue Transduction and Toxicity

Coxsackievirus and adenovirus receptor (CAR), alphav integrins, and heparan sulfate glycosaminoglycans (HSGs) are the tropism determinants of adenoviral (Ad) vectors in vivo. For the development of a targeted Ad vector, its broad tropism needs to be blocked (or reduced). We have previously developed Ad vectors with ablation of CAR, alphav integrin, and HSG binding by mutation of the FG loop in the fiber knob (deletion of T489, A490, Y491, and T492 of the fiber protein), deletion of the RGD motif of the penton base, and substitution of the fiber shaft domain for that derived from Ad type 35, respectively, and have shown that this triple-mutant Ad vector [Ad/deltaF(FG)deltaP-S35-L2] exhibits significantly lower transduction in mouse liver compared with the conventional Ad vector [Koizumi, N., Mizuguchi, H., Sakurai, F., Yamaguchi, T., Watanabe, Y., and Hayakawa, T. (2003). J. Virol. 77, 13062-13072]. In the present study, we optimized the fiber knob mutation for further reduced in vivo transduction and examined toxicity of the modified Ad vectors. Ad/deltaF(AB)deltaPS35- L2, a triple-mutant Ad vector containing a mutation of the AB loop in the fiber knob (R412S, A415G, E416G, and K417G), mediated approximately 15,000- and 500-fold lower mouse liver transduction by intravenous and intraperitoneal administration, respectively, than the conventional Ad vector, and mediated 10- fold lower mouse liver transduction than did Ad/deltaF(FG)deltaP-S35-L2. Ad/deltaF(AB)deltaP-S35-L2 also exhibited lower transduction of other organs compared with Ad/deltaF(FG)deltaP-S35-L2 and the conventional Ad vector. Levels of both liver serum enzymes (aspartate transferase [AST] and alanine transferase (ALT)] and interleukin (IL)-6 in mouse serum after intravenous administration of Ad/deltaF(AB)deltaP-S35-L2 were similar to those in the nontreatment mouse serum, whereas the conventional Ad vector led to high levels of AST, ALT, and IL-6. We therefore succeeded in further improving the mutant Ad vector, abolishing both viral natural tropism and toxicity. This new Ad vector appears to be a fundamental vector for targeted gene delivery.

871. Surface Modification of Adenovectors with TAT- and Antp-Containing Polymers Protects Them from Neutralizing Antibodies and Increases Expression of Reporter Genes In Vitro and In Vivo

The relative inefficiency of adenovirus (Ad)-based transduction vectors in cardiovascular tissues is related to the low expression of the CAR receptor on the surface of endothelial and smooth muscle cells as well as to the rapid neutralization of Ad by anti-Ad antibodies. Polymer modification of Ad surface potentially addresses these problems by masking Ad particles from neutralizing antibodies and providing a convenient platform for the conjugation of ligands possessing transduction-facilitating properties, such as TAT and Antp peptides. Our present studies investigated the hypothesis that by surface modifying Ad using photoreactive polymers to attach either TAT or Antp increased transduction could be achieved while reducing susceptibility to neutralizing antibodies. This was studied with reporter gene transduction with surface-modified Ad vectors in cell culture and in vivo, in rat carotid arteries. A series of fluorescently labeled polyallylamine (PAA)-based photochemically activatable (either via benzophenone, or azide chemistry) thiol reactive linear polymers were custom synthesized and conjugated with TAT-SH or Antp-SH. Ad-GFP or Ad-Luc were suspended in PBS x5 and admixed with either TAT-, Antp-derivatized or unmodified polymers to obtain the final polymer/Ad ratios ranging from 1:60 to 1:10 (w/w). Cellular uptake of vectors and ensuing transgene expression in rat aortic smooth muscle cell line (A10), primary bovine aortic endothelial cells (BAEC) and human alveolar epithelial cell line (A549) were examined by the fluorescence microscopy and fluorometry. Additionally, naïve and surface- modified Ad vectors were exposed to escalating concentrations of neutralizing anti-knob antibodies (50 to 500 nM) prior to the cell infection. 6x108 pfu of either naïve or polymeric TAT-conjugated Ad-Luc were locally delivered to the balloon-injured common carotid arteries of SD rats (n=6). The transgene expression was assessed 2 days after gene delivery by bioluminescence imaging. Model experiments have shown faster kinetics of photochemical polymer attachment to the capsid proteins with azide-compared to benzophenone-containing polymers. The surface modification of Ad-GFP with TAT- and Antp-derivatized polymers resulted in 3–10-fold increase of GFP expression in the studied cell types. 15 min incubation of naïve Ad with neutralizing antibodies resulted in a 94% decrease of GFP expression in A10 cells, while the surface modification of Ad with TAT- and Antp-containing polymers bestowed protection against neutralizing antibodies in proportion with the extent of surface modification (59%, 14% and 6% inhibition for the polymer/Ad ratios of 1:60, 1:30 and 1:10, respectively). In the initial in vivo experiments local delivery of polymeric TAT- conjugated Ad resulted in 4.4-fold enhancement of luciferase activity in comparison with unmodified Ad. In conclusion, light-induced covalent conjugation of TAT- and Antp-modified PAA-based polymers to Ad capsid proteins protects adenovectors from preformed neutralizing antibodies and significantly augments gene transduction both in vitro and in vivo.