Abraham Bout

Replication-Deficient Human Adenovirus Type 35 Vectors for Gene Transfer and Vaccination: Efficient Human Cell Infection and Bypass of Preexisting Adenovirus Immunity

ABSTRACT Replication-deficient human adenovirus type 5 (Ad5) can be produced to high titers in complementing cell lines, such as PER.C6, and is widely used as a vaccine and gene therapy vector. However, preexisting immunity against Ad5 hampers consistency of gene transfer, immunological responses, and vector-mediated toxicities. We report the identification of human Ad35 as a virus with low global prevalence and the generation of an Ad35 vector plasmid system for easy insertion of heterologous genes. In addition, we have identified the minimal sequence of the Ad35-E1B region (molecular weight, 55,000 [55K]), pivotal for complementation of fully E1-lacking Ad35 vector on PER.C6 cells. After stable insertion of the 55K sequence into PER.C6 cells a cell line was obtained (PER.C6/55K) that efficiently transcomplements both Ad5 and Ad35 vectors. We further demonstrate that transduction with Ad35 is not hampered by preexisting Ad5 immunity and that Ad35 efficiently infects dendritic cells, smooth muscle cells, and synoviocytes, in contrast to Ad5.

Exploiting the Natural Diversity in Adenovirus Tropism for Therapy and Prevention of Disease

ABSTRACT Since targeting of recombinant adenovirus vectors to defined cell types in vivo is a major challenge in gene therapy and vaccinology, we explored the natural diversity in human adenovirus tissue tropism. Hereto, we constructed a library of Ad5 vectors carrying fibers from other human serotypes. From this library, we identified vectors that efficiently infect human cells that are important for diverse gene therapy approaches and for induction of immunity. For several medical applications (prenatal diagnosis, artificial bone, vaccination, and cardiovascular disease), we demonstrate the applicability of these novel vectors. In addition, screening cell types derived from different species revealed that cellular receptors for human subgroup B adenoviruses are not conserved between rodents and primates. These results provide a rationale for utilizing elements of human adenovirus serotypes to generate chimeric vectors that improve our knowledge concerning adenovirus biology and widen the therapeutic window for vaccination and many different gene transfer applications.

Highly Efficient Transduction of Human Monocyte-Derived Dendritic Cells with Subgroup B Fiber-Modified Adenovirus Vectors Enhances Transgene-Encoded Antigen Presentation to Cytotoxic T Cells

The efficiency of dendritic cells (DC) as immunotherapeutic vaccines critically depends on optimal delivery of target Ags. Although DC modified by subgroup C type 5 recombinant adenoviruses (rAd5) provide encouraging results, their clinical application is hampered by the need for high viral titers to achieve sufficient gene transfer, due to the lack of the Ad5 fiber receptor. We now demonstrate that rAd5 carrying subgroup B Ad fibers are up to 100-fold more potent than classical rAd5 for gene transfer and expression in human DC, rAd5 with a type 35 fiber (rAd5F35) being the most efficient vector. This improvement relates to a greater and faster virus entry and to an increased transgene expression especially following DC maturation. Furthermore, these new vectors possess enhanced synergistic effects with other activation signals to trigger DC maturation. Consequently, rAd5F35-infected DC engineered to express the gp100 melanoma-associated Ag largely exceed rAd5-infected DC in activating gp100-specific CTL. Finally, the DC infection pattern of rAd5F35 is fully conserved when DC are in the vicinity of primary skin-derived fibroblasts, suggesting this vector as a candidate for in vivo targeting of DC. Thus, subgroup B fiber-modified rAd5 constitute a major breakthrough in the exploitation of ex vivo rAd-targeted DC as clinically relevant vaccines and may also be suitable for in vivo genetic modification of DC.

High-level expression of recombinant IgG in the human cell line PER.C6

The number of therapeutic monoclonal antibodies in production is expected to rise rapidly in the next few years. As a result, there is much focus on the optimization of antibody expression platforms. Several issues are important including the speed of transition from bench to manufacturing, yield of IgG, and quality (particularly of the glycan structures present on immunoglobulins). We have characterized the human cell line PER.C6 for its ability to produce recombinant IgG. Production yields are still being optimized, but in nonfed batch culture, PER.C6 is able to grow to a cell density of 5 × 106 cells/mL and produce 300–500 mg/L IgG; this is likely to increase significantly in fed batch cultures. The generation of antibody‐producing cell lines is fast, as rounds of amplification of inserted genes are not required for high production yields. The gene copy number of inserted genes is in the region of 1–10 copies per genome. In addition, PER.C6 is a human cell line, and so does not add glycans, which are immunogenic in humans. A core fucose molecule is essentially always present, and galactose residues are present at a physiological level (0, 1, and 2 galactose residues per glycan are present at a ratio of 1:2:1). No hybrid or high‐mannose structures are seen.

Improved Adenovirus Vectors for Infection of Cardiovascular Tissues

ABSTRACT To identify improved adenovirus vectors for cardiovascular gene therapy, a library of adenovirus vectors based on adenovirus serotype 5 (Ad5) but carrying fiber molecules of other human serotypes, was generated. This library was tested for efficiency of infection of human primary vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Based on luciferase, LacZ, or green fluorescent protein (GFP) marker gene expression, several fiber chimeric vectors were identified that displayed improved infection of these cell types. One of the viruses that performed particularly well is an Ad5 carrying the fiber of Ad16 (Ad5.Fib16), a subgroup B virus. This virus showed, on average, 8- and 64-fold-increased luciferase activities on umbilical vein ECs and SMCs, respectively, compared to the parent vector. GFP andlacZ markers showed that approximately 3-fold (ECs) and 10-fold (SMCs) more cells were transduced. Experiments performed with both cultured SMCs and organ cultures derived from different vascular origins (saphenous vein, iliac artery, left interior mammary artery, and aorta) and from different species demonstrated that Ad5.Fib16 consistently displays improved infection in primates (humans and rhesus monkeys). SMCs of the same vessels of rodents and pigs were less infectable with Ad5.Fib16 than with Ad5. This suggests that either the receptor for human Ad16 is not conserved between different species or that differences in the expression levels of the putative receptor exist. In conclusion, our results show that an Ad5-based virus carrying the fiber of Ad16 is a potent vector for the transduction of primate cardiovascular cells and tissues.

In vitro and in vivo gene transfer to pulmonary cells mediated by cationic liposomes

Cationic liposomes have been proposed as alternative to adenovirus in the treatment of cystic fibrosis lung disease. Therefore, we have investigated the efficiency of two lipid mixtures in mediating gene transfer in in vitro and in vivo models. The cationic lipid DOTMA (N-(1-(2,3(dioleyloxy)propyl)-n,n,n-trimethylammoniumchloride++ +) and DOGS (dioctadecylamidoglycylspermine) were used in combination with the neutral lipid DOPE (dioleoylphosphatidylethanolamine). The relative transfection efficiencies of the two cationic liposomes were tested using the bacterial beta-galactosidase (lacZ) and the firefly luciferase genes. Gene expression was detected in both cell limes and primary culture of rhesus monkey airway epithelium after transfection with plasmid DNA complexed with DOGS/DOPE or DOTMA/DOPE. Transfection efficiency of both types of lipids was higher in the mouse fibroblast 3T3 cell line as compared to human carcinoma A549 cells and primary epithelial cultures. Administration of DNA-liposome complexes via intratracheal instillation resulted in expression of the lacZ and luciferase marker gene in the mouse airways. In vivo transfection mediated by both types of liposomes were proven to be far less efficient than adenovirus treatment.

Feasibility of Adenovirus-Mediated Nonsurgical Synovectomy in Collagen-Induced Arthritis-Affected Rhesus Monkeys

Gene transfer to synovial tissue by adenoviral vectors (Ad) was studied in vitro in cultured human synoviocytes and in vivo in seven primates with arthritis. Hyperplastic synovium was efficiently transduced with Ad.lacZ in vitro and in vivo in rhesus monkeys with collagen-induced arthritis, whereas chondrocytes were not transduced. Intraarticular injection of recombinant Ad harboring the luciferase gene showed the presence of reporter gene products only in Ad-injected joints. In addition, the feasibility of synovectomy by Ad harboring the herpes simplex virus thymidine kinase gene (tk) was studied. In vitro infection of synovium from rheumatoid arthritis patients with Ad.TK, followed by administration of ganciclovir, resulted in death of >90% of the synoviocytes. By mixing Ad.TK-infected with noninfected cells, it appeared that the presence of 10% infected synoviocytes resulted in the killing of more than 85% of the synoviocytes, demonstrating a substantial bystander effect. Intraarticular injection of Ad.TK in the knees of rhesus monkeys with arthritis, followed by treatment with ganciclovir for 14 days, resulted in increased apoptotic cell death in the synovium of Ad.TK-injected as compared with noninjected joints and ablation of the synovial lining layer. The procedure revealed no toxic side effects. These data suggest that nonsurgical synovectomy by tK gene therapy is feasible.

Infection efficiency of type 5 adenoviral vectors in synovial tissue can be enhanced with a type 16 fiber

OBJECTIVE To obtain an adenoviral vector with increased infection efficiency in the synovial tissue compared with conventional vectors based on adenovirus serotype 5 (Ad5), without compromising the specificity of infection. METHODS Coxsackie adenovirus receptor (CAR) expression was assessed in cultured synoviocytes. Chimeric adenoviruses based on Ad5 but carrying the DNA encoding the fiber of adenovirus from subgroup B (Adll, 16, 35) or D (Ad24, 28, 33, 45, or 47) were constructed and produced on PER.C6 cells. The gene transfer efficiency of these chimera was tested on cultured synoviocytes and peripheral blood mononuclear cells (PBMC). RESULTS No surface expression of CAR protein was observed on synoviocytes. CAR messenger RNA expression of synoviocytes was found to be low. Of all fiber chimeric vectors tested, vectors carrying the fiber of Ad16 (Ad5.fib16) were most potent, yielding approximately150 times increased transgene expression in cultured synoviocytes compared with those of Ad5. Flow cytometry showed that the increase in transgene expression was caused by the transduction of higher percentages of synoviocytes and higher gene expression per synoviocyte. Experiments with 500 virus particles/cell of Ad5.GFP or Ad5.fib16.GFP resulted in an infection efficiency of 0.6% and 1% in PBMC and 43% and 76% in synoviocytes, respectively. CONCLUSION Synoviocytes hardly express CAR, which hampers Ad5-mediated gene transfer. Ad5.fib16 is superior to Ad5 vectors for transducing synoviocytes, without compromising the specificity of infection. Our data suggest that Ad5.fib16-mediated gene transfer to synovial tissue improves the therapeutic window.

Assignment of the human UDP glucuronosyltransferase gene (UGT1A1) to chromosome region 2q37

UDP glucuronosyltransferases (UGTs) comprise a multigene family of drug-metabolizing enzymes. The sub-family of UGTs that conjugate bilirubin and phenolic compounds with glucuronic acid has been termed UGT1A1. In man, UGT1A1 isoforms are encoded by a single gene, UGT1A1. Protein isoforms encoded by UGT1A1 originate by alternative splicing. In the present study, we used the cDNA of UGT1A1*4, a bilirubin-conjugating isoform, to localize the UGT1A1 locus in the human genome. The UGT1A1 gene was assigned by in situ hybridization to chromosome region 2q37.

The influence of synovial fluid on adenovirus-mediated gene transfer to the synovial tissue

OBJECTIVE To determine the effect of synovial fluid (SF) from rheumatoid arthritis (RA) patients on adenovirus type 5 (Ad5)-mediated gene transfer to synoviocytes, and to explore new strategies for vector development based on the neutralization data obtained. METHODS SF was derived from 63 randomly selected R4 patients. Ten samples were used to study the effect of SF on Ad5-mediated gene transfer in synoviocytes. IgG and <100-kd fractions were purified from these 10 SF, and their effect on gene transfer was determined. Neutralizing activity against wild-type Ad5 (wt-Ad5), wt-Ad26, wt-Ad34, wt-Ad35, and wt-Ad48 was tested in the SF from the remaining 53 patients. RESULTS Seven of 10 SF samples inhibited Ad5-mediated gene transfer. Purified antibodies exhibited inhibition patterns similar to those seen with unfractionated SF. In 5 of 10 SF samples, low molecular weight fractions inhibited gene transfer at low dilutions. Neutralization of wt-Ad35 by SF from RA patients was less frequent than neutralization of other wt-Ad tested (4% versus 42-72%; n = 53). CONCLUSION SF from 70% of the RA patients contained neutralizing antibodies that hamper Ad5-mediated gene transfer to synoviocytes. The activity of neutralizing antibodies may be circumvented in the majority of RA patients when vectors based on an Ad35 backbone are used.