CRISPR-targeted MAGT1 insertion restores XMEN patient hematopoietic stem cells and lymphocytes

XMEN disease, defined as "X-linked MAGT1 deficiency with increased susceptibility to Epstein-Barr virus infection and N-linked glycosylation defect," is a recently described primary immunodeficiency marked by defective T cells and natural killer (NK) cells. Unfortunately, a potentially curative hematopoietic stem cell transplantation is associated with high mortality rates. We sought to develop an ex vivo targeted gene therapy approach for patients with XMEN using a 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 gene-edited hematopoietic stem and 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 NK group 2 member D (NKG2D) expression and function in XMEN lymphocytes for potential treatment of infections, and it corrected HSPCs for long-term gene therapy, thus offering 2 efficient therapeutic options for XMEN poised for clinical translation.

Development of human hepatocellular carcinoma in X-linked severe combined immunodeficient pigs: An orthotopic xenograft model

Hepatocellular carcinoma (HCC) is the fifth most common primary tumor and the third leading cause of cancer-related deaths worldwide. Rodent models of HCC have contributed to the advancement of studies investigating liver carcinogenesis, tumor-host interactions, and drug screening. However, their small size renders them unsuitable for surgical or clinical imaging studies, necessitating the development of larger-size HCC models. Here, we developed a xenograft model of human HCC in X-linked interleukin-2 receptor gamma chain gene (Il2rg)-targeted severe combined immunodeficient (SCID) pigs. HepG2 cell suspension in serum-free medium containing 50% membrane matrix was directly injected into the liver parenchyma of eight X-linked Il2rg-targeted SCID pigs (6.6–15.6 kg) via ultrasonography-guided percutaneous puncture. Tumor engraftment was evaluated weekly using ultrasonography, and cone-beam computed tomography was performed during arterial portography (CTAP) and hepatic arteriography (CTHA) to evaluate the hemodynamics of engrafted tumors. The engrafted tumors were histologically analyzed following necropsy and assessed for pathological similarities to human HCCs. Macroscopic tumor formation was observed in seven of the eight pigs (simple nodular tumors in three and multinodular tumors in four). Engrafted tumors were identified as low-echoic upon ultrasonography and as perfusion-defect nodules on the CTAP images. Meanwhile, CTHA showed that the tumors were hyperattenuating. Further, histopathological findings of the engrafted tumors were consistent with those of human HCC. In conclusion, the porcine model of human HCC, successfully generated herein, might help develop more effective therapeutic strategies for HCC.

Impact of Day 14 Peripheral Blood Chimerism after Allogeneic Hematopoietic Stem Cell Bone Transplantation on the Treatment Outcome of Non-Malignant Disease

BACKGROUND

The impact of early peripheral blood chimerism on the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unclear. We aimed to determine whether day 14 peripheral blood chimerism after allo-HSCT predicts outcomes in patients with non-malignant diseases.

METHODS

Data from 56 patients who received allo-HSCT between April 2007 and March 2016 were retrospectively analyzed. Chimerism was evaluated using short-tandem repeat polymerase chain reaction, with mixed chimerism (MC) defined as greater than 1% recipient cells which was further categorized into low-level MC (> 1% and < 15% of recipient-derived cells) and high-level MC (≥ 15% of the recipient-derived cells).

RESULTS

Thirty-six patients showed complete donor chimerism (CC), 14 low-level MC, and 6 high-level MC at day 14 post-transplant. The estimated 5-year event-free survival (EFS) was higher in the CC or low-level MC groups than in the high-level MC group (86.1% vs. 71.4% vs. 33.3%; P = 0.001). In BM or peripheral blood stem cell (BM/PBSC) transplants, the 5-year EFS was higher in the CC or low-level MC group than in the high-level MC group (93.1% vs. 66.7% vs. 0%; P < 0.001). However, in cord blood transplants, the 5-year OS and EFS according to the day 14 peripheral blood chimerism did not reach statistical significance.

CONCLUSION

Although CC is not always necessary after allo-HSCT for non-malignant diseases, our data suggest that day 14 peripheral blood chimerism may predict outcomes in patients with non-malignant diseases who underwent BM/PBSC transplants.

X-linked severe combined immunodeficiency (X-SCID) rats for xeno-transplantation and behavioral evaluation

BACKGROUND

To evaluate the in vivo function of human dopaminergic (DA) neurons, Parkinson's disease (PD) model rats made by the hemi-lateral injection of 6-hydroxydopamine (6-OHDA) are widely used as host animals. In the case of such xeno-transplantation, however, immunosuppression is needed for good survival of the grafted cells.

NEW METHODS

In order to determine whether human mature neurons can survive in X-linked severe combined immunodeficiency (X-SCID) rats without immunosuppression, we grafted human embryonic stem cell (ESC)-derived DA neurons into the striatum of X-SCID rats. We next treated the X-SCID rats with 6-OHDA and grafted mouse fetal DA neurons or human induced pluripotent stem cell (iPSC)-derived DA neurons to examine whether these rats can be used as PD model rats.

RESULTS

X-SCID rats did not elicit immune responses against human ESC-derived DA neurons and consequently resulted in good survival of the cells without immunosuppression. Furthermore, 6-OHDA-lesioned X-SCID rats exhibited rotational behavior, which was recovered by grafting mouse fetal DA neurons or human iPSC-derived DA neurons.

COMPARISON WITH EXISTING METHODS

Immunosuppression by drugs such as Cyclosporine A requires daily injection, which is stressful for rats and moreover may cause renal or hepatic failure. Furthermore, blood levels of the drug may not be stable, which weakens the reliability of the data.

CONCLUSIONS

Our results provide a more accessible and reliable method to evaluate the in vivo function of human DA neurons, potentially offering a pre-clinical study for the application of pluripotent stem cells.

FBP17 Mediates a Common Molecular Step in the Formation of Podosomes and Phagocytic Cups in Macrophages

Macrophages act to protect the body against inflammation and infection by engaging in chemotaxis and phagocytosis. In chemotaxis, macrophages use an actin-based membrane structure, the podosome, to migrate to inflamed tissues. In phagocytosis, macrophages form another type of actin-based membrane structure, the phagocytic cup, to ingest foreign materials such as bacteria. The formation of these membrane structures is severely affected in macrophages from patients with Wiskott-Aldrich syndrome (WAS), an X chromosome-linked immunodeficiency disorder. WAS patients lack WAS protein (WASP), suggesting that WASP is required for the formation of podosomes and phagocytic cups. Here we have demonstrated that formin-binding protein 17 (FBP17) recruits WASP, WASP-interacting protein (WIP), and dynamin-2 to the plasma membrane and that this recruitment is necessary for the formation of podosomes and phagocytic cups. The N-terminal EFC (extended FER-CIP4 homology)/F-BAR (FER-CIP4 homology and Bin-amphiphysin-Rvs) domain of FBP17 was previously shown to have membrane binding and deformation activities. Our results suggest that FBP17 facilitates membrane deformation and actin polymerization to occur simultaneously at the same membrane sites, which mediates a common molecular step in the formation of podosomes and phagocytic cups. These results provide a potential mechanism underlying the recurrent infections in WAS patients.

A progressive, fatal dystonia-Parkinsonism syndrome in a patient with primary immunodeficiency receiving chronic IVIG therapy

X-linked agammaglobulinemia (XLA) is a primary immunodeficiency disorder caused by a mutation in the Bruton agammaglobulinemia tyrosine kinase gene that results in severe B-cell deficiency. So far, neurological complications of XLA have been primarily related to acute and/or chronic central nervous system enteroviral infections. In the last few years a progressive neurodegenerative syndrome of unknown etiology has been described in XLA patients. We describe and present a video of an XLA patient who developed a fatal dementing, dystonia-Parkinsonism syndrome 14 years into his immune disorder. Physician awareness of this rare syndrome may lead to its better characterization and management.

New Insights and Unresolved Issues Regarding Insertional Mutagenesis in X-linked SCID Gene Therapy

The oncogenic potential of retrovirus-mediated gene therapy has been re-emphasized because four patients developed T-cell acute lymphoblastic leukemia (T-ALL)-like disease from an otherwise successful gene therapy trial for X-linked severe combined immunodeficiency (X-linked SCID). X-linked SCID, a disease caused by inactivating mutations in the IL2Rgamma gene, is part of a heterogeneous group of SCIDs characterized by the lack of T cells in conjunction with the absence of B and/or natural killer (NK) cells. Gene therapy approaches are being developed for this group of diseases. In this review we discuss the various forms of SCID in relation to normal T-cell development. In addition, we consider the possible role of LMO2 and other T-ALL oncogenes in the development of adverse effects as seen in the X-linked SCID gene therapy trial. Furthermore, we debate whether the integration near the LMO2 locus is sufficient to result in T-ALL-like proliferations or whether the gamma-retroviral viral expression of the therapeutic IL2RG gene contributes to leukemogenesis. Finally, we review some newly developed murine models that may have added value for gene therapy safety studies.

Severe food allergy as a variant of IPEX syndrome caused by a deletion in a noncoding region of the FOXP3 gene

BACKGROUND & AIMS

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX; OMIM 304930) syndrome is a congenital syndrome characterized by autoimmune enteropathy, endocrinopathy, dermatitis, and other autoimmune phenomena. In the present work, we aimed to uncover the molecular basis of a distinct form of IPEX syndrome presenting at the edge of autoimmunity and severe allergy.

METHODS

The FOXP3 gene was sequenced, FOXP3 messenger RNA (mRNA) was quantified by real-time polymerase chain reaction (PCR), and protein expression in peripheral blood lymphocytes was analyzed by flow cytometry after intracellular staining. In coculture experiments (CD4(+)CD25(-) and CD4(+)CD25(+) cells), the functions of regulatory T cells were analyzed. Expression of interferon gamma and interleukin 2 and 4 mRNA within the inflamed intestinal mucosa was quantified by real-time PCR.

RESULTS

Here, we describe a distinct familial form of IPEX syndrome that combines autoimmune and allergic manifestations including severe enteropathy, food allergies, atopic dermatitis, hyper-IgE, and eosinophilia. We have identified a 1388-base pair deletion (g.del-6247_-4859) of the FOXP3 gene encompassing a portion of an upstream noncoding exon (exon -1) and the adjacent intron (intron -1). This deletion impairs mRNA splicing, resulting in accumulation of unspliced pre-mRNA and alternatively spliced mRNA. This causes low FOXP3 mRNA levels and markedly decreased protein expression in peripheral blood lymphocytes of affected patients. Numbers of CD4(+)CD25(+)FOXP3(+) regulatory T cells are extremely low, and the CD4(+)CD25(+) T cells that are present exhibit little regulatory function.

CONCLUSIONS

A new mutation within an upstream noncoding region of FOXP3 results in a variant of IPEX syndrome associating autoimmune and severe immunoallergic symptoms.