Introduction: CRISPR/Cas9 nuclease has gained popularity as a genome editing tool due to its straight-forward mechanism. However, there are concerns that CRISPR nuclease would cause off-target and toxicity. The CRISPR/ Cas9 D10A nickase was designed to enhance genome editing. Nevertheless, this raised the question of whether the efficiency of nickase is compromised compared to CRISPR/Cas9 nuclease. Targeting HIV genes, we investigated if CRISPR nuclease performed better than the nickase in efficacy and safety. Methods: CRISPR nucleases and nickases were designed to target Gag, Pol, Rev, Vif, Tat and LTR. HIV latently infected cell line, ACH-2, was transfected with the nucleases and nickases. Changes to viral load after CRISPR treatment was measured using p24 ELISA. Safety of nuclease and nickase was monitored using GFP expression with fluorescence microscopy and flow cytometry. Targeting two sites within the same gene, and targeting multiple genes concurrently were also studied to determine efficacy of CRISPR in reducing viral load. Results: A 44.9 to 68.1% and a 34.4 to 49.7% decrease in viral load was seen in CRISPR nuclease and nickase respectively. Microscopy and flow cytometry results showed that the nickase system was slightly toxic with a 0.31 to 0.7-fold cell death. There was a 34% decrease in viral load when two sites were targeted within a gene, and the largest decrease was seen when all the nucleases were combined, giving a 75.4% decrease in viral load at day 5. Conclusion: The knowledge gained from this study will be employed to im- prove genome editing in other disease models.
Gene therapy revolves around modifying genetic makeup by inserting foreign nucleic acids into targeted cells via gene delivery methods to treat a particular disease. While the genes targeted play a key role in gene therapy, the gene delivery system used is also of utmost importance as it determines the success of gene therapy. As primary cells and stem cells are often the target cells for gene therapy in clinical trials, the delivery system would need to be robust, and viral-based entries such as lentiviral vectors work best at transporting the transgene into the cells. However, even within lentiviral vectors, several parameters can affect the functionality of the delivery system. Using cardiac-derived c-kit expressing cells (CCs) as a model system, this study aims to optimize lentiviral production by investigating various experimental factors such as the generation of the lentiviral system, concentration method, and type of selection marker. Our findings showed that the 2nd generation system with pCMV-dR8.2 dvpr as the packaging plasmid produced a 7.3-fold higher yield of lentiviral production compared to psPAX2. Concentrating the virus with ultracentrifuge produced a higher viral titer at greater than 5 × 105 infectious unit values/ml (IFU/ml). And lastly, the minimum inhibitory concentration (MIC) of puromycin selection marker was 10 μg/mL and 7 μg/mL for HEK293T and CCs, demonstrating the suitability of antibiotic selection for all cell types. This encouraging data can be extrapolated and applied to other difficult-to-transfect cells, such as different types of stem cells or primary cells.
A major characteristic of Candida biofilm cells that differentiates them from free-floating cells is their high tolerance to antifungal drugs. This high resistance is attributed to particular biofilm properties, including the accumulation of extrapolymeric substances, morphogenetic switching, and metabolic flexibility.