Current Gene Therapy - Volume 18, Issue 6, 2018

Diamond Blackfan Anemia (DBA) is an inherited erythroid aplasia with onset in childhood. Patients carry heterozygous mutations in one of 19 Ribosomal Protein (RP) genes, that lead to defective ribosome biogenesis and function. Standard treatments include steroids or blood transfusions but the only definitive cure is allogeneic Hematopoietic Stem Cell Transplantation (HSCT). Although advances in HSCT have greatly improved the success rate over the last years, the risk of adverse events and mortality is still significant. Clinical trials employing gene therapy are now in progress for a variety of monogenic diseases and the development of innovative stem cell-based strategies may open new alternatives for DBA treatment as well. In this review, we summarize the most recent progress toward the implementation of new therapeutic approaches for this disorder. We present different DNA- and RNA-based technologies as well as new candidate pharmacological treatments and discuss their relevance and potential applicability for the cure of DBA.

Exosomes play a critical role in intercellular communication between cancer cells and their environments. These secreted nanovesicles can transfer different cargos such as mRNAs, proteins and microRNA (miRNA) to recipient cells. Exosomal miRNAs (exomiRs) derived from tumor cells have emerged as key players in cancer promotion via impairment of the immune system response, tumor growth, metastasis, angiogenesis, and chemotherapeutic drug resistance. Moreover, since dysregulation of miRNA expression in tumor cells can be reflected by distinct profiles of exomiRs extracted from the bodily fluids of cancer patients, they can be considered as non-invasive diagnostic, prognostic and predictive biomarkers. Additionally, due to the critical roles of exomiRs in cancer promotion, targeting of various aspects of exosome biogenesis, miRNA sorting or loading has been suggested as a novel approach for cancer therapy. Firstly, this review aims to describe the biosynthesis and trafficking of exosomes as well as their isolation, characterization and content. Next, the recent advances on the role of exomiRs in cancer promotion as well as the application of exomiR as a cancer biomarker and therapeutic target are reviewed.

Erectile Dysfunction (ED) is one of the most common conditions affecting middle-aged and older men. Over the past few decades, oral phosphodiesterase type 5 inhibitors have been used to treat ED. However, these oral medications require on-demand access and are not effective in some hard-totreat populations. Moreover, there are no effective alternative treatments for ED. Based on results from preclinical models designed to provide long-term improvement of ED and other related conditions, gene therapy has shown great potential as a novel therapy for clinical management of ED. Gene therapy refers to the use of viral and non-viral vectors to deliver therapeutic genes to tissues via direct or transduced cell-mediated approaches. With the growing knowledge on the molecular mechanisms involved in the pathophysiology of ED, a number of therapeutic gene strategies have been extensively tested and proven to be effective in many animal models. However, only a few of them have been evaluated in clinical trials. This is due to safety concerns that need to be addressed before the clinical application can be considered. In this review, we summarize the key advancements in gene therapy for ED treatment, with an emphasis on the emerging stem cell-based approaches as well as other combinational strategies. The challenges facing the clinical application of gene therapy for ED treatment are also discussed.

Introduction: Oncolytic virus therapy is currently considered as a promising therapeutic approach for cancer treatment. Adenovirus is well-known and extensively characterized as an oncolytic agent. The increasing number of clinical trials using this virus generates the demand for the development of a well-established purification approach. Triton X-100 is commonly used in cell lysis buffer preparations. The addition of this surfactant in the list of substances with the very high concern of the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation promoted the research for effective alternatives. Methods: In this work, a purification strategy for oncolytic adenovirus compatible with phase I clinical trials, using an approved surfactant – Polysorbate 20 was developed. The proposed downstream train, composed by clarification, concentration using tangential flow filtration, intermediate purification with anion exchange chromatography, followed by a second concentration and a final polishing step was evaluated for both Triton X-100 and Polysorbate 20 processes. The impact of cell lysis with Polysorbate20 and Triton X-100 for each downstream step was evaluated in terms of product recovery and impurities removal. Overall, 61 ± 4% of infectious viral particles were recovered. Depletion of host cell proteins and ds-DNA was 99.9% and 97.1%, respectively. Results & Conclusion: The results indicated that Polysorbate 20 can be used as a replacement for Triton X-100 during cell lysis with no impact on product recovery, potency, and purity. Moreover, the developed process is scalable and able to provide a highly purified product to be used in phase I and II clinical trials.

Objective: Immunotherapy based on induction of T-cell responses is a promising approach to cancer treatment. The study aims to design artificial epitope-based immunogens, DNA vaccine candidates against melanoma and evaluate their ability to stimulate tumor cytotoxicity of ex vivo generated T-cells. Methods: The original computational methods were used for predicting T-cell epitopes and designing polyepitope melanoma antigens. Artificial genes encoding the target antigens were cloned into DNA vaccine plasmid vector. Target gene expression was confirmed both at transcriptional and translational level in HEK-293T cells transfected with DNA-vaccine constructs. Dendritic cells were generated from adherent peripheral blood mononuclear cells of HLA-A*02:01+ donors. Cytotoxic activity of effector lymphocytes stimulated in co-culture with autologous antigen-presenting dendritic cells towards melanoma Mel Is cells was assessed with lactate dehydrogenase release assay. The proportion of granzyme B producing CD8+ T-cells was estimated using intracellular cytokine staining and flow cytometry. Results: Two DNA vaccine constructions were created - pMEL-TCI and pMEL-A0201 - encoding polypeptides containing T-cell epitopes of six immunodominant melanoma antigens (NY-ESO-1, MART1, MAGE-A1, MAGE-A11, MAGE-A3, and MAGE-C1). Dendritic cells transfected with DNA vaccine constructs were found to stimulate both tumor cytotoxicity mediated by autologous lymphocytes and granzyme B production by CD8+ T-cells, and pMEL-A0201 was found to be the most efficient. Conclusion: The described approach may become a common platform for designing immunotherapeutic vaccines against oncological diseases.

Background: Leber's hereditary optic neuropathy is a hereditary mitochondrial disease. No effective treatment has so far been established, with gene therapy currently being the most promising. Because of the possibility of spontaneous visual acuity recovery in this disease, we screened patients before gene therapy, excluding those with spontaneous visual acuity improvement, and prepared for the subsequent gene therapy. Objective: To clinically observe the course of Leber's hereditary optic neuropathy for 6 months prior to gene therapy. Methods: Sixty-six patients with Leber's hereditary optic neuropathy were enrolled in the study. Patients were classified based on the duration of disease: less than 24 months and over 24 months. Three clinical follow-up examinations were conducted over 1 year. We assessed intraocular pressure, visual acuity, visual field, retinal nerve fiber layer thickness, fundus photographs, and visual evoked potential. Results: Eighty-two eyes displayed stable visual acuity, including both eyes in 34 patients and one eye in 14 patients; 33 eyes of 22 patients displayed decrease in visual acuity (less than 24 months: 24 eyes; over 24 months: nine eyes); and 17 eyes of 12 patients showed improvement in visual acuity (less than 24 months: four eyes; over 24 months: 13 eyes). Visual acuity and visual field indices decreased over 24 months from disease onset and appeared stable after 24 months. Conclusion: Most patients with Leber's hereditary optic neuropathy gradually stabilize visual function with prolonged onset time, and the lower possibility of spontaneous vision recovery provides a basis for future evaluation of the effectiveness of gene therapy.