Lentivector gene therapy for X-linked chronic granulomatous disease (X-CGD) has proven to be a viable approach, but random vector integration and subnormal protein production from exogenous promoters in transduced cells remain concerning for long-term safety and efficacy. A previous genome editing-based approach using SpCas9 and an oligodeoxynucleotide donor to repair genetic mutations demonstrated the capability to restore physiological protein expression, but lacked sufficient efficiency in quiescent CD34+ hematopoietic cells for clinical translation. Here, we show transient inhibition of p53-binding protein 1 (53BP1) significantly increased (2.3-fold) long-term homology directed repair (HDR) to achieve highly efficient (80% gp91phox+ cells compared to healthy donor control) long-term correction of X-CGD CD34+ cells.
MMA amplifies TWA compared to traditional spectral analyses, but both likely reflect similar pathophysiology. Validation in larger populations will enable MMA-TWA to be widely applied to stratify risk for sudden cardiac arrest.
X-linked chronic granulomatous disease is an immunodeficiency characterized by defective production of microbicidal reactive oxygen species (ROS) by phagocytes. Causative mutations occur throughout the 13 exons and splice sites of the
CYBB
gene, resulting in loss of gp91
phox
protein. Here we report gene correction by homology-directed repair in patient hematopoietic stem/progenitor cells (HSPCs) using CRISPR/Cas9 for targeted insertion of
CYBB
exon 1–13 or 2–13 cDNAs from adeno-associated virus donors at endogenous
CYBB
exon 1 or exon 2 sites. Targeted insertion of exon 1–13 cDNA did not restore physiologic gp91
phox
levels, consistent with a requirement for intron 1 in
CYBB
expression. However, insertion of exon 2–13 cDNA fully restored gp91
phox
and ROS production upon phagocyte differentiation. Addition of a woodchuck hepatitis virus post-transcriptional regulatory element did not further enhance gp91
phox
expression in exon 2–13 corrected cells, indicating that retention of intron 1 was sufficient for optimal
CYBB
expression. Targeted correction was increased ~1.5-fold using i53 mRNA to transiently inhibit non-homologous end joining. Following engraftment in NSG mice, corrected HSPCs generated phagocytes with restored gp91
phox
and ROS production. Our findings demonstrate the utility of tailoring donor design and targeting strategies to retain regulatory elements needed for optimal expression of the target gene.
X-linked Severe Combined Immunodeficiency (SCID-X1) due to IL2RG mutations is potentially fatal in infancy where ‘emergency’ life-saving stem cell transplant may only achieve incomplete immune reconstitution following transplant. Salvage therapy SCID-X1 patients over 2 years old (NCT01306019) is a non-randomized, open-label, phase I/II clinical trial for administration of lentiviral-transduced autologous hematopoietic stem cells following busulfan (6 mg/kg total) conditioning. The primary and secondary objectives assess efficacy in restoring immunity and safety by vector insertion site analysis (VISA). In this ongoing study (19 patients treated), we report VISA in blood lineages from first eight treated patients with longer follow up found a > 60-fold increase in frequency of forward-orientated VIS within intron 3 of the High Mobility Group AT-hook 2 gene. All eight patients demonstrated emergence of dominant HMGA2 VIS clones in progenitor and myeloid lineages, but without disturbance of hematopoiesis. Our molecular analysis demonstrated a cryptic splice site within the chicken β-globin hypersensitivity 4 insulator element in the vector generating truncated mRNA transcripts from many transcriptionally active gene containing forward-oriented intronic vector insert. A two base-pair change at the splice site within the lentiviral vector eliminated splicing activity while retaining vector functional capability. This highlights the importance of functional analysis of lentivectors for cryptic splicing for preclinical safety assessment and a redesign of clinical vectors to improve safety.
'X-linked MAGT1 deficiency with increased susceptibility to Epstein-Barr virus-infection and N-linked glycosylation defect' (XMEN) disease is a recently described primary immunodeficiency marked by defective T and Natural Killer (NK) cells. Potentially curative hematopoietic stem cell transplant is associated with high mortality rates. We sought to develop an ex vivo targeted gene therapy approach for XMEN patients using CRISPR/Cas9/adeno-associated vector (AAV) to insert a therapeutic MAGT1 gene at the constitutive locus under the regulation of the endogenous promoter. Clinical translation of CRISPR/Cas9/AAV-targeted gene editing (GE) is hampered by low engraftable GE hematopoietic stem/progenitor cells (HSPCs). Here, we optimized GE conditions by transient enhancement of homology-directed repair while suppressing AAV-associated DNA damage response to achieve highly efficient (>60%) genetic correction in engrafting XMEN HSPCs in transplanted mice. Restored MAGT1-glycosylation function in human NK and CD8+ T cells restored NKG2D expression and function in XMEN lymphocytes for potential treatment of infections, and corrected HSPCs for long-term gene therapy, thus offering two efficient therapeutic options for XMEN poised for clinical translation.
It is concluded that in patients with bidirectional CTI block, pacing from the CS may be associated with TC mimicking a conduction leak through the isthmus. Pacing just outside the CS os helps distinguish pseudo from true isthmus block.
In electrically stimulated skeletal muscle, force production is downregulated when oxygen delivery is compromised and rapidly restored upon restoration of oxygen delivery in the absence of cellular disturbance. Whether this 'oxygen-conforming' response of force occurs and is exercise intensity dependent during stable voluntary muscle activation in humans is unknown. In 12 participants (six female), handgrip force, forearm muscle activation (EMG), muscle oxygenation and forearm blood flow (FBF)were measured during rhythmic handgrip exercise at forearm EMG achieving 50, 75 or 90% critical impulse (CI). Four minutes of brachial artery compression to reduce FBF by ∼60% (Hypoperfusion) or sham compression (adjacent to artery; Control) was performed during exercise. Sham compression had no effect. Hypoperfusion rapidly reduced muscle oxygenation at all exercise intensities, resulting in contraction force per muscle activation (force/EMG) progressively declining over 4 min by ∼16% at both 75 and 90% CI. No force/EMG decline occurred at 50% CI. Rapid restoration of muscle oxygenation after compression was closely followed by force/EMG such that it was not different from Control within 30 s for 90% CI and after 90 s for 75% CI. Our findings reveal that an oxygen-conforming response does occur in voluntary exercising muscle in humans. Within the exercise modality and magnitude of fluctuation of oxygenation in this study, the oxygen-conforming response appears to be exercise intensity dependent. Mechanisms responsible for this oxygen-conforming response have implications for exercise tolerance and warrant investigation.
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