Lentiviral Vector-Mediated Gene Transfer Restores CD18 Expression in Long-Term Repopulating Hematopoietic Stem and Progenitor Cells Isolated from a Patient with Leukocyte Adhesion Deficiency Type 1

Leukocyte adhesion deficiency type 1 (LAD-1) is an inherited primary immunodeficiency caused by loss-of-function mutation within the ITGB2 gene, which encodes the beta2 integrin subunit CD18. Individuals with LAD-1 experience significant loss of neutrophil-mediated innate cellular immune function, resulting in delayed wound healing, severe periodontitis, and life-long bouts of bacterial infection. LAD-1 is a prime candidate for lentiviral vector-mediated genetic intervention as i) it is an intractable, potentially life-threatening disease with limited treatment options, ii) it is amenable to current ex vivo gene therapy procedures, and iii) partial phenotypic correction would present a high likelihood of significant clinical benefit. Allogeneic stem cell transplant can be curative, but suffers from matched donor availability and the potential for graft-versus-host disease. Autologous ex vivo gene therapy may provide a viable alternative to allogeneic transplant in LAD-1 patients. We have evaluated the ability of a CD18-expressing lentiviral vector (LV-hCD18) to mediate ex vivo transduction of LAD-1 patient-derived CD34+ hematopoietic stem and progenitor cells (HSPCs) and subsequent long-term LAD-1 HSPC engraftment in immunodeficient NOD-scid IL2Rg null (NSG) mice. An open reading frame encoding human CD18 was placed under the transcriptional control of the MND promoter (a modified retroviral promoter associated with high levels of stable transgene expression) and packaged in VSV-G-pseudotyped lentiviral particles. After 1 day of pre-stimulation, LAD-1 HSPCs were transduced with LV-hCD18 (MOI = 10) in the presence or absence of transduction-enhancing adjuvants, poloxamer 407 (P407) and prostaglandin E2 (PGE 2), for 24 hours. Sublethally irradiated NSG mice (7 mice/group) were transplanted with either mock-transduced LAD-1 HSPCs, LAD-1 HSPCs transduced in the absence of adjuvants, or LAD-1 HSPCs transduced in the presence of P407/PGE 2. Bone marrow was harvested at ~5.5 months post-transplant for flow cytometric analyses of engraftment efficiency, transgene marking, and human blood cell lineage reconstitution. Bone marrow from mice that received mock-transduced LAD-1 HSPCs showed an average total of 6.45 ± 2.54% (mean ± SEM) CD45+ human cells. Mice that received LAD-1 HSPCs transduced in the absence of adjuvants showed 7.99 ± 1.82% CD45+ human cells, whereas mice transplanted with LAD-1 HSPCs transduced in the presence of adjuvants showed 7.33 ± 1.90% CD45+ cells. A Kruskal-Wallis statistical test indicated no significant difference in the level of human cell engraftment among the recipient groups (P=0.72). Consistent with the LAD-1 phenotype, human myeloid cells from mice that received mock-transduced LAD-1 HSPCs displayed only background levels of CD18 marking (0.13 ± 0.06% CD45+CD13+CD18+ cells). Mice that received LAD-1 HSPCs transduced in the absence of adjuvants showed 4.05 ± 0.40% CD18+ human myeloid cells (range 2.19% to 5.50%), whereas mice that received LAD-1 HSPCs transduced in the presence of P407/PGE 2 showed 9.56 ± 0.96% CD18+ human myeloid cells (range 4.63% to 13.10%), thus representing a >2-fold increase in in vivo, vector-mediated transgene marking levels when adjuvant was used. Moreover, vector-mediated expression of CD18 rescued endogenous expression of a major CD18 heterodimerization partner in neutrophils, CD11b. In mock-transduced LAD-1 HSPC recipients, CD13+ human myeloid cells were devoid of cell surface CD11b expression (0.01 ± 0.01% CD45+CD13+CD11b+ cells). In contrast, CD13+ human myeloid cells in mice that received LAD-1 HSPCs transduced in the absence of adjuvant showed detectable levels of CD11b expression (2.62 ± 0.19% of CD18-expressing human myeloid cells), and CD11b levels were increased to 6.90 ± 0.98% in LAD-1 HSPCs transduced in the presence of P407/PGE 2. Multilineage engraftment, as evidenced by the presence of CD3+ T cells and CD20+ B cells, was noted within all groups; however, human myeloid cells represented the most prominent human blood cell compartment observed. Colony-forming-unit assays of transduced cells and non-transduced control cells pre-transplant showed similar clonogenic output and colony diversity. In sum, successful transduction, engraftment, transgene marking, CD11b rescue, and multilineage reconstitution supports further development of lentiviral vector-mediated gene therapy for LAD-1. Disclosures No relevant conflicts of interest to declare.

Gene Therapy for Neuronopathic Mucopolysaccharidoses: State of the Art

The need for long-lasting and transformative therapies for mucopolysaccharidoses (MPS) cannot be understated. Currently, many forms of MPS lack a specific treatment and in other cases available therapies, such as enzyme replacement therapy (ERT), do not reach important areas such as the central nervous system (CNS). The advent of newborn screening procedures represents a major step forward in early identification and treatment of individuals with MPS. However, the treatment of brain disease in neuronopathic MPS has been a major challenge to date, mainly because the blood brain barrier (BBB) prevents penetration of the brain by large molecules, including enzymes. Over the last years several novel experimental therapies for neuronopathic MPS have been investigated. Gene therapy and gene editing constitute potentially curative treatments. However, despite recent progress in the field, several considerations should be taken into account. This review focuses on the state of the art of in vivo and ex vivo gene therapy-based approaches targeting the CNS in neuronopathic MPS, discusses clinical trials conducted to date, and provides a vision for the future implications of these therapies for the medical community. Recent advances in the field, as well as limitations relating to efficacy, potential toxicity, and immunogenicity, are also discussed.

Gene therapy with hematopoietic stem and progenitor cell for monogenic disorders: a systematic review and meta-analysis

To provide an assessment of the safety of ex-vivo gene therapy (GT) with hematopoietic stem and progenitor cells (HSPC), we reviewed in a systematic manner the literature on monogenic diseases to describe survival, genotoxicity and engraftment of gene corrected HSPC, across vector platforms and diseases. From 1995 to 2020, 55 trials for 14 diseases met inclusion criteria and 406 patients with primary immunodeficiencies (55.2%), metabolic diseases (17.0%), haemoglobinopathies (24.4%) and bone marrow failures (3.4%) were treated with gammaretroviral vector (γRV) (29.1%), self-inactivating γRV (2.2%) or lentiviral vectors (LV) (68.7%). The pooled overall incidence rate of death was 0.9 per 100 person-years of observation (PYO) (95%CI = 0.37–2.17). There were 21 genotoxic events out of 1504.02 PYO. All these events occurred in γRV trials (0.99 events per 100 PYO, 95%CI = 0.18–5.43) for primary immunodeficiencies. Pooled rate of engraftment was 86.1% (95%CI = 66.9–95.0%) for γRV and 99.0% (95%CI = 95.1–99.8%) for LV HSPC-GT (p = 0.002). A comprehensive meta-analysis on HSPC-GT showed stable reconstitution of haematopoiesis in most recipients with superior engraftment and safer profile in patients receiving LV-transduced HSPC.

A Simple, Safe and Effective Approach for Personalized Precision Ex Vivo Gene Therapy Based on Autoinfusion of Gene-Modified Leucoconcentrate (GML) Prepared from Routine Unit of Patient's Peripheral Blood

Nowadays gene and cell therapy become the basic methods in regenerative medicine. However only few gene and cell products are currently approved for clinical usage. Biosafety problems, complexity of cell and gene technologies and high cost of manufacturing are the main reasons for the slow introduction of such approaches in practical medicine. Treatment of hereditary diseases of the immune system based on the correction of the mutant gene by delivering functional recombinant gene into WBC is the first successfully employed in the clinical practice approach of cell-mediated or ex vivo gene therapy. Earlier we have reported the strategy of the cell-mediated gene therapy based on umbilical cord blood mononuclear cells transduced with adenoviral vectors carrying recombinant genes encoding neurotrophic factors for treatment neurodegenerative diseases, neurotrauma and stroke. Significant disadvantage of this method is the usage of the umbilical cord blood mononuclear cells as a cell carrier for the therapeutic genes. Considering immunodeficiency treatment and our own data we developed a new approach of recombinant gene delivery for personalized ex vivo gene therapy. The method is based on autoinfusion of patient's WBC transduced with recombinant therapeutic genes for correction of certain pathological conditions. In the present study for the first time the human gene-modified leucoconcentrate (GML) producing recombinant reporter gene encoding green fluorescent protein (GFP) was obtained without culturing WBC in vitro. The routine unit of peripheral blood (450 ml) was collected into the plastic blood bag and the leucocyte- and platelet-rich concentrates (50 ml) were obtained by standard method using Macopress Smart (Macopharma, France). Afterwards the equal volume of hydroxyethyl starch 6% was added into the plastic blood bag which was centrifuged (DP-2065 R PLUS, Centrifugal Presvac RV; Presvac, Buenos Aires, Argentina) at 350 rpm for 10 min at 10°C. The obtained supernatant was transferred into the new plastic blood bag using manual plasma extractor FK-01 (Leadcore, Russia) and 200 ml of saline was added into the bag which was centrifuged at 1300 rpm for 10 min at 10°C and the supernatant was expressed out of the bag so that the remaining solution in the bag (30 ml) contained leucoconcentrate (WBC - 45.56 ± 23.93 × 106/ml and RBC - 1.76 ± 3.33 × 109/ml). Transduction of WBC with chimeric adenoviral vector (Ad5/35) carrying GFP gene was performed in the plastic bag with MOI 5 according to the count of WBC in the leucoconcentrate. After transduction for 12 hours, 200 ml of saline was added to the bag with leucoconcentrate, the mixture was centrifuged at 1000 rpm for 10 min at 10°C and the supernatant was squeezed out of the bag. The remained in the bag solution (30 ml) was considered as gene-modified leucoconcentrate carrying GFP gen (WBC - 22.63 ± 8.90 × 106/ml and RBC - 1.77 ± 1.21 × 109/ml). For in vitro study of GFP gene expression the samples of GML-GFP were cultivated for 60 hours after GML-GFP preparation. Fluorescent microscopy in the cytoplasm of the transduced WBC showed specific intensive green fluorescence. Flow cytometry analysis demonstrated that 2.5% of WBC from the GML-GFP efficiently expressed GFP. Thus leucoconcentrate after 72 h of transduction with Ad5/35-GFP with MOI 5 resulted in 2.5% of the GFP-positive cells. Thus the results of this study represent a simple, safe and effective approach for preparation of GML for personalized ex vivo gene therapy aimed at temporary production of the specific recombinant biologically active molecules for pathogenetic therapy of the varied nosological form, such as trauma, ischemic, degenerative, autoimmune, infection and other diseases. This study was supported by the grant of Russian Science Foundation 19-75-10030. Disclosures No relevant conflicts of interest to declare.