Gamma-glutamylcysteine synthetase-based selection strategy for gene therapy of chronic granulomatous disease and graft-vs.-host disease

Electroporation formulation for cell therapy

Cell transfection efficiency often determines the success of cell-based gene therapy. Cell transfection via Nucleofector technology yields high transfection efficiency and low cytotoxicity. However, owing to trade secrecy, the components in each buffer are unknown, which not only increases the cost of electroporation studies but also limits the application of Nucleofector in clinical cell-based gene therapies. Thus, we developed a three-step method to determine the optimal conditions, including buffer, program, and additional polymer, in electroporation for multiple cancers and stem cell lines. This method could reduce the cost, allow researchers to find the optimal electroporation conditions for their cell lines of interest, and greatly boost the application potential of electroporation in clinical cell-based gene therapies.

Mitochondrial DNA ligase is dispensable for the viability of cultured cells but essential for mtDNA maintenance

Multiple lines of evidence support the notion that DNA ligase III (LIG3), the only DNA ligase found in mitochondria, is essential for viability in both whole organisms and in cultured cells. Previous attempts to generate cells devoid of mitochondrial DNA ligase failed. Here, we report, for the first time, the derivation of viable LIG3-deficient mouse embryonic fibroblasts. These cells lack mtDNA and are auxotrophic for uridine and pyruvate, which may explain the apparent lethality of the Lig3 knock-out observed in cultured cells in previous studies. Cells with severely reduced expression of LIG3 maintain normal mtDNA copy number and respiration but show reduced viability in the face of alkylating and oxidative damage, increased mtDNA degradation in response to oxidative damage, and slow recovery from mtDNA depletion. Our findings clarify the cellular role of LIG3 and establish that the loss of viability in LIG3-deficient cells is conditional and secondary to the ρ(0) phenotype.

Competitive electroporation formulation for cell therapy

Established cell transfection via nucleofection relies on nucleofection buffers with unknown and proprietary makeup due to trade secrecy, inhibiting the possibility of using this otherwise effective method for developing cell therapy. We devised a three-step method for discovering an optimal formulation for the nucleofection of any cell line. These steps include the selection of the best nucleofection program and known buffer type, selection of the best polymer for boosting the transfection efficiency of the best buffer and the comparison with the optimal buffer from an established commercial vendor (Amaxa). Using this three-step selection system, competitive nucleofection formulations were discovered for multiple cell lines, which are equal to or surpass the efficiency of the Amaxa nucleofector solution in a variety of cells and cell lines, including primary adipose stem cells, muscle cells, tumor cells and immune cells. Through the use of scanning electron microscopy, we have revealed morphological changes, which predispose for the ability of these buffers to assist in transferring plasmid DNA into the nuclear space. Our formulation may greatly reduce the cost of electroporation study in laboratory and boosts the potential of application of electroporation-based cell therapies in clinical trials.

A retro-lentiviral system for doxycycline-inducible gene expression and gene knockdown in cells with limited proliferative capacity

Currently, there is no reliable system for regulated gene expression and regulated gene knockdown in cells with finite lifespan. In this manuscript, we describe a vector system, consisting of a retrovirus for the delivery of rtTA, and a lentivirus for the delivery of either a transgene or a miR-shRNA for the modification of primary cells. Primary rat pulmonary microvascular endothelial cells (PMVEC) modified by these vectors for the inducible expression of Gaussia luciferase or DsRed Express demonstrated greater than 100-fold induction of the transgene expression with doxycycline. The system works reliably in both sequential and simultaneous infection modes, with about 95% of the sells selected with two antibiotics being inducible in each mode. The lentiviral vector for gene knockdown allows for the direct cloning of shRNA oligos using alpha-complementation, and for the monitoring of induction of RNA interference with fluorescent reporter, mCherry. The gene knockdown vector was validated by knocking down beta-actin expression in PMVECs, with two of the four constructs showing 59 and 75% knockdown, respectively, compared to uninduced controls. The vectors described here were successfully used for the modification of various primary and established cell lines for regulated gene expression and regulated knockdown.

Modern management of chronic granulomatous disease

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder of phagocytic cells resulting in failure to kill a characteristic spectrum of bacteria and fungi and in defective degradation of inflammatory mediators with concomitant granuloma formation. Current prophylaxis with trimethoprim-sulfamethoxazole, itraconazole and in selected cases additional interferon gamma is efficient, but imperfect. A significant recent progress towards new antibiotic (e.g. linezolid) and antifungal (e.g. voriconazole and posaconazole) therapy will allow survival of most patients into adulthood. Adolescent and adult CGD is increasingly characterized by inflammatory complications, such as granulomatous lung and inflammatory bowel disease, requiring immunosupressive therapy. Allogeneic haematopoietic stem cell transplantation from a human leucocyte antigen identical donor is currently the only proven curative treatment for CGD and can be offered to the selected patients. Gene-replacement therapy for patients lacking a suitable stem cell donor is still experimental and faces major obstacles and risks. However, it may offer some transitory benefits and has helped in a few cases to overcome life-threatening infections.

Gene therapy of inherited immunodeficiencies

BACKGROUND

Primary immunodeficiencies (PID) are a group of inherited diseases that affect the development or activity of the immune system. In severe cases allogeneic haematopoietic stem cell transplantation has proved to be a successful curative modality but it is limited by toxicity and reduced efficacy in mismatched donor settings.

OBJECTIVE

Gene therapy for PID has been developed as an alternative strategy and has entered the clinical arena. In this review we discuss the outcomes of recent gene therapy trials and some of the problems that remain to be tackled.

METHODS

Results from clinical trials for X-linked severe combined immunodeficiency (SCID-X1), adenosine deaminase deficient SCID (ADA-SCID), and X-linked chronic granulomatous disease (X-CGD) are discussed. In addition, other conditions are highlighted such as the Wiskott Aldrich Syndrome (WAS) for which gene therapy has shown considerable promise in preclinical studies, and are currently being translated into novel clinical approaches.

RESULTS/CONCLUSION

Whilst these encouraging results demonstrate that gene therapy can be used successfully to treat monogenic PID, the occurrence of vector-related side effects has highlighted the need for accurate assessment of the associated risks and a requirement for improvements in vector design.