Direct gene transfer for the understanding and treatment of human disease

Gene therapy in flap survival

Growth factors are members of a large functional group of polypeptide regulatory molecules that exert a powerful influence on all phases of wound healing and repair through interactions with specific cell surface receptors. The use of growth factors to improve wound healing and the viability of ischemic skin flaps has been well-documented throughout the last decade. In this article, we review the literature concerning the use gene therapy in flap survival, including the various methods employed to transplant plasmids or viruses capable of coding and producing growth factors in ischemic tissue.

Effects of additional sequences directly downstream from the AUG on the expression of GFP gene

We have studied the expression of the green fluorescent protein (GFP) gene to gain more understanding of the effects of additional nucleotide triplets (codons) downstream from the initiation codon on the translation of the GFP mRNA in CHO and Cos1 cells. A leader sequence of six consecutive identical codons (GUG, CUC, AGU or UCA) was introduced into a humanized GFP (hm gfp) gene downstream from the AUG to produce four GFP gene variants. Northern blot and RT-PCR analysis indicated that mRNA transcription from the GFP gene was not significantly affected by any of the additional sequences. However, immunoblotting and FACS analysis revealed that AGU and UCA GFP variants produced GFP at a mean level per cell 3.5-fold higher than the other two GFP variants and the hm gfp gene. [35S]-Methionine labeling and immunoprecipitation demonstrate that GFP synthesis was very active in UCA variant transfected-cells, but not in GUG variant and hm gfp transfected-cells. Moreover, proteasome inhibitor MG-132 treatment indicated that the GFPs encoded by each of the GFP variants and the hm gfp were equally stable, and this together with the comparable mRNA levels observed for each construct suggested that the different steady-state GFP concentrations observed reflected different translation efficiencies of the various GFP genes. In addition, the CUC GFP variant, when transiently transfected into CHO or COS-1 cells, did not produce any GFP expressing cells (fully green cells), and the GUG variant produced GFP expressing cells less than 10%, while AGU and UCA GFP variants up to 30-35% in a time course study from 8 to 36 h posttransfection. Analysis of the potential secondary structure of the GFP variant mRNAs especially in the translation initiation region suggested that the secondary structure of the GFP mRNAs was unlikely to explain the different translation efficiencies of the GFP variants. The present findings indicate that a change of the initiation context of the GFP gene by addition of extra coding sequence can alter the translation efficiency of GFP mRNA, providing a means of more efficient expression of GFP in eukaryotic cells.

Targeting of peptides to restenotic vascular smooth muscle cells using phage display in vitro and in vivo

Restenosis after angioplasty occurs in 30-40% of the treated patients. To develop a strategy to deliver drugs to restenotic lesions, we selected phages that bind to proliferating vascular smooth muscle cells (VSMC), from a random constraint 15-mer peptide phage display library. Phages were selected for binding to cultured primary aortic VSMC (in vitro biopanning) and selected for binding to denudated carotid arteries in mice (in vivo biopanning). In vitro biopanning did not result in a consensus sequence, but recurring FLGW and LASR amino acid motifs were identified. In vivo biopanning resulted in two consensus peptides 5G6 (CNIWGVVLSWIGVFPEC) and 5E5 (CESLWGGLMWTIGLSDC). Surprisingly, these two sequences were recovered after both in vitro and in vivo biopanning, but predominantly in vivo. Moreover, a strong recurring motif, IGR, was identified in the in vivo clones. The consensus phages 5G6 and 5E5 bind selectively to VSMC compared to other cell types. Furthermore, they bind preferentially to proliferating VSMC compared to VSMC that were growth arrested, and are effectively internalized by their target cells. The specific binding capacities of 5G6 and 5E5 phages suggest that these peptide sequences can be used for targeting of restenotic lesions, in which proliferating VSMC are the dominant cell type.

Immune-based approaches for control of HIV infection and viral-induced immunopathogenesis

Due to the limited efficacy of the current antiretroviral drug regimens in completely eradicating HIV and reconstituting the immune system, AIDS research is turning toward immune-based therapy to complement highly active antiretroviral therapy. Here we review potential mechanisms of protective cellular immunity and current HIV-specific immune-based strategies and discuss the rationale for novel hypothetical immunologic approaches for modulation of host antiviral immunity. One of the mechanisms by which the immune system exerts antiviral effects is via leukocyte generation of anti-HIV factors. Recent observations in this area of research suggest that non-HIV antigens can stimulate the in vitro production of anti-HIV activity by leukocytes from healthy uninfected individuals and HIV-infected patients. These findings may provide insights for the design of novel therapeutic or prophylactic approaches, which might contribute to modulating immune system control of HIV infection.

Gene therapy strategies for colon cancer

Colorectal cancer is the second most common cause of cancer mortality in Western countries. Gene therapy represents a novel approach to the treatment of colorectal cancer, and this review addresses the current strategies and ongoing clinical trials, including gene correction, immunomodulatory approaches and virus-directed enzyme-prodrug systems. Although the pre-clinical results for these strategies have been encouraging, clinical trials have not yet reflected these data. However, gene therapy for colorectal cancer is still in the early stages of development, and its potential, particularly in combination with conventional cancer therapies, warrants further investigation.

Pharmaceutical perspectives of nonviral gene therapy

The use of nonviral plasmid-based gene medicines represents an attractive in vivo gene transfer strategy that is simple and lacks many risks that are inherent to viral systems. Commercialization of gene medicines requires a thorough analysis of business opportunities, unmet clinical needs, competitive products under development, and issues related to intellectual property. Synthetic gene delivery systems are designed to control the location of a gene within the body by affecting distribution and access of a gene expression system to the target cell, and/or recognition by a cell surface receptor and uptake followed by intracellular and nuclear translocation. Plasmid-based gene expression systems are designed to control the level, fidelity, and duration of in vivo production of a therapeutic gene product. This review will provide insights into the potentials of plasmid-based gene therapy and critical evaluation of gene delivery sciences and clinical applications of gene medicines.

Genetic therapy. Past, present, and future

The early stages of genetic therapy present challenges for clinicians and basic scientists. Clinicians must become familiar with new terminology and concepts, and must keep a perspective on the new field in the face of inflated claims and high-profile failures. Basic scientists must continually return to disease models and to patients to determine what are the proper safety issues and relevant efficacy questions for specific diseases and vector systems. And in an era of instant information, all concerned parties must be careful about how progress is communicated to colleagues, patients, and the lay public.

Controlled delivery of antigens and adjuvants in vaccine development

Advances in the understanding of the pathogenesis of infectious diseases and cancer immunology have inspired many new approaches to vaccine development. Many subunit antigens and peptides that are effective for vaccination have been discovered. These subunit antigens in tum stimulate synthesis of effective adjuvants to enhance their immunogenicity. Controlled-release technology offers the potential of further improving the efficacy of conventional vaccine formulations by optimizing the temporal and spatial presentation of the-antigens and adjuvants to the immune system. The combination of sustained release and depot effect may also reduce the amount of antigens or adjuvants needed and eliminate the booster shots that are necessary for the success of many vaccinations. This review examines the contribution controlled release technology can make in various areas of vaccination, with an emphasis on tumor vaccines.

Adenovirus-mediated interferon-gamma transfer inhibits growth of transplanted HTLV-1 Tax tumors in mice

Human T cell leukemia virus type 1 (HTLV-1) causes adult T cell leukemia (ATL), and the virus-encoded trans-activator, Tax, plays an important role in T cell transformation. In the HTLV-1 long terminal repeat (LTR)-Tax transgenic mouse model, Tax expression causes fibroblastic tumors. A tumor-derived cell line (B line) obtained from an explant of a Tax-transformed tumor, was established. This line expresses high levels of many cytokines as a consequence of Tax activation. However, the tumors are not immunogenic when transplanted into syngeneic mice. Because B line cells do not express the immunogenic cytokine interferon-gamma (IFN-gamma), a replication-defective adenoviral vector was used to deliver the IFN-gamma gene to tumor cells. The recombinant IFN-gamma adenovirus (IFN-gamma/Ad) can efficiently infect B line cells, resulting in high levels of IFN-gamma expression and secretion. Local secretion of IFN-gamma from B line cells caused both CD(4+)- and CD(8+)-positive T cell infiltration, and completely inhibited local tumor development in transplanted mice. Immunization with these cells significantly delayed tumor development after subsequent challenges of parental tumor cells. Expression of IFN-gamma in B cells also partially inhibited the highly expressed immune suppressive cytokine, transforming growth factor-beta 1 (TGF-beta 1). This system provides us with a valuable tumor immune therapy model to evaluate the effects of cytokines in induction or inhibition of specific antitumor immunity.

Nucleic acid vaccination primes hepatitis B virus surface antigen-specific cytotoxic T lymphocytes in nonresponder mice

The efficiency of different vaccination techniques to prime in vivo major histocompatibility complex class I-restricted murine cytotoxic T-lymphocyte (CTL) precursors to hepatitis B virus small surface antigen (HBsAg) was investigated. Mice were immunized either by injection of a low dose of recombinant HBsAg protein preparations (native HBsAg particles or denatured HBsAg monomers) without adjuvants, by infection with recombinant vaccinia virus carrying an HBsAg-encoding gene, or by intramuscular transfer of plasmid DNA encoding HBsAg under appropriate promoter control. In H-2d mice, an Ld-restricted, S28-39-specific CTL response was efficiently primed by all alternative vaccination techniques tested, but the most potent priming of class I-restricted CTL to HBsAg in vivo was observed with DNA immunization. Priming of anti-HBsAg CTL in H-2b mice was not detectable after infection with a recombinant vaccinia virus or after injection with exogenous recombinant HBsAg preparations. After DNA immunization, however, both Kb- and Db-restricted CTL reactivity to HBsAg emerged in H-2b mice. Hence, nucleic acid immunization revealed class I-restricted CTL responsiveness to HBsAg in a mouse strain previously considered to be a nonresponder at the CTL level. These results demonstrate that the simple technique of nucleic acid immunization not only is extremely efficient but also reveals an extended spectrum of potentially immunogenic epitopes of protein antigens.

Cationic liposomes for direct gene transfer in therapy of cancer and other diseases

Cationic liposomes can mediate efficient delivery of DNA and DNA/protein complex to mammalian cells in vitro and in vivo. Cationic cholesterol derivatives mixed with phosphatidylethanolamine and sonicated to form small unilamellar vesicles can complex with DNA and mediate the entry into the cytosol from the endosome compartment. One of the liposome formulations, DC-Chol liposomes, is used in a gene therapy clinical trial for melanoma. Recently, we exploited these cationic liposomes for the delivery of trans-activating protein factors to regulate and control the expression of delivered transgenes in a protein dose-dependent manner. Bacteriophage T7 RNA polymerase was co-delivered with a reporter gene under the control of T7 promoter to allow cytoplasmic expression of the gene. Human immunodeficiency virus-1 transactivating protein was also codelivered with a reporter gene under the control of HIV-1 long terminal repeat. Finally, human tumor cells selected for cis-platin resistance or isolated from patients who have failed cis-platin therapy are highly transfectable with cationic liposomes. These results suggest a serial therapy protocol with cis-platin and gene therapy for malignancy.