Current Gene Therapy - Volume 8, Issue 4, 2008

The immunogenicity and cytotoxicity associated with early generations of adenoviral vectors provided a strong incentive for the development of helper-dependent adenovirus, a last generation of adenoviral vectors that is devoid of all viral coding sequences. These vectors have shown to mediate longer high-level transgene expression in vivo with reduced toxicity and thus offer enormous potential for human gene therapy. In addition, they possess a considerably larger cloning capacity than conventional adenoviral vectors making the transfer of large cDNAs, multiple transgenes and longer tissuespecific or regulable promoters possible. In this article, we review the progress made with helper-dependent adenoviral vectors. The development and optimization of scalable production processes and strategies for helper removal will be presented. Current chromatography options available for vector purification and the new challenges facing researchers for the separation of empty particles and/or helper viruses will be discussed. Finally, we will describe recent advances made in our understanding of their interaction with the immune system and their potential as gene delivery vehicles in vivo for the treatment of diseases affecting liver, skeletal muscle and brain.

Since the RNAi mechanisms were established in 1990, the rapid progression of RNAi application from animal to clinical trails in human diseases has shown its enormous therapeutic potential. In this review, RNAi therapeutics in allergic diseases is discussed, from RNAi mechanisms and design to challenges and potential targets in allergic diseases. Current reported studies on investigating RNAi therapy in vitro and in vivo are also reviewed. Although there are promising studies in RNAi-based therapy, understanding further the detailed mechanisms of RNAi-based therapy and investigating more effective delivery methods are required for future development.

Prognosis of multiple myeloma (MM) remains insufficient despite the intervention of high dose chemotherapy with auto- or allo- hematopoietic stem cell transplantation and the advent of molecular target drugs such as thalidomide, lenalidomide, and bortezomib. Further development or new concepts of therapeutic approaches are still required for MM treatment. Current standard protocol for MM treatment does not include gene delivery method or oncolytic virus approaches. Since MM is a disorder originated from B cell lineage, it involves immunological aspects in both pathogenesis and clinical manifestations. Therefore, the comprehension of immunology as well as oncology is essential to exploit new therapeutic approaches. Recently, novel therapeutic concepts for MM have been emerging. In this review, we present current progress of gene therapy related to MM treatments as well as the overview of MM treatment history.

Oxidative cell damage is a natural occurring phenomenon due to the aerobic conditions where cells are embedded; however, such injury can efficiently be controlled and repaired by the inherent antioxidants of the cell. When the oxidant/antioxidant balance is disrupted towards the former by any chemical, biological or physical insult a pathological state could be developed, therefore, an extensive list of compounds with proved or assumed antioxidants properties has largely been used for improving or restoring the health status. Pharmacological therapies as well as dietary or complementary therapies are continuously being investigated for the counteracting of the harmful or damaging effects of oxidation in cells or tissues. However, critical antioxidant levels are not always achieved at the target damaged cells by these approaches; on the other side, the expression of recombinant antioxidant genes specifically directed to the afflicted cell by gene delivery has shown remarkable results. In this review we summarize the literature focused on some of the current antioxidant molecular pharmacological strategies with particular emphasis to the gene transfer protocols involved in the treatment of oxidative stress-related disorders.

Acquired immune deficiency syndrome (AIDS) is caused by a lentivirus, human immunodeficiency virus type- 1 (HIV-1). Viral entry is mediated by specific interaction of the viral envelope (Env) glycoprotein with a cell surface molecule CD4 which serves as the primary receptor and a chemokine (C-C or C-X-C motif) receptor CCR5 or CXCR4 which serves as a co-receptor. The viral Env, the cellular CD4 receptor, or the CCR5/CXCR4 co-receptors may be the targets of therapeutic interventions. Compared to the high variability of the viral Env protein, lack of variability in the CD4 receptor and the CCR5 or CXCR4 co-receptor makes them better targets to prevent viral entry. Downregulation of CD4 or CXCR4 is likely to have harmful consequences for the immune function or cellular maturation and homing. In contrast, individuals who lack functional CCR5 have no apparent immune defects, and show decreased susceptibility to HIV-1 infection and delayed progression to AIDS. CCR5 is essential for HIV-1 infection through all routes of transmission. Therefore, its downregulation may not only prevent disease progression, but also the spread of HIV-1 transmission. To block CCR5 function, a number of molecules were developed, including low molecular weight compounds, chemokines, Nterminally- modified chemokine analogues, chemokine-derived molecules, chemokine-based synthetic peptides, and anti- CCR5 monoclonal antibodies. Gene therapy strategies were developed using intrakines and intrabodies to prevent cell surface expression of CCR5 and zinc finger-nucleases, or using small interfering RNAs, antisense RNAs, or ribozymes to decrease co-receptor synthesis. This review describes the importance of targeting CCR5 and summarizes the status of various anti-CCR5 gene therapy strategies.

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

Attempts have been made by conventional gene therapy to suppress hepatic fibrogenesis, but potential oncogenic activity may prevent its clinical use. Recently, a novel major approach has been developed for resolution of liver fibrosis and cirrhosis: inactivation of hepatic stellate cells (HSC) using the endogenous expressing gene, which could mediate the homeostatic adaptation of liver. Cytoglobin (Cygb), originally identified in cultured rat HSC, is in a new class of heme containing proteins known as the hexacoordinate globin superfamily. These proteins exhibit peroxidase activity against hydrogen peroxides and lipid hydroperoxides. Considerable attention has been focused on the potential benefits of use of Cygb in fibrosis therapy, as up-regulation of Cygb expression could reduce oxidant stress, suppress HSC differentiation to a myofibroblast-like phenotype and eventually prevent the progress of liver fibrosis. Cygb has also been found to be a candidate tumor suppressor gene that might provide a new option for cancer gene therapy. In this review we systematically analyze the potential of Cygb as a prospective gene medicine for curing fibrosis, cancer, and other diseases such as diabetes. The molecular structure, regulation and subcellular location of Cygb are reviewed as well.