Improved Titer and Gene Transfer by Lentiviral Vectors Using Novel, Small ß-Globin Locus Control Region Elements.

ß-globin lentiviral vectors (ß-LV) have faced challenges in clinical translation for gene therapy of sickle cell disease (SCD) due to low titer and sub-optimal gene transfer to hematopoietic stem and progenitor cells (HSPCs). To overcome the challenge of preserving efficacious expression while increasing vector performance, we used published genomic and epigenomic data available through ENCODE to redefine enhancer element boundaries of the ß-globin locus control region (LCR) to construct novel ENCODE core sequences. These novel LCR elements were used to design a ß-LV of reduced proviral length, termed CoreGA-AS3-FB, produced at higher titers and possessing superior gene transfer to HSPCs when compared to the full-length parental ß-LV at equal MOI. At low vector copy number, vectors containing the ENCODE core sequences were capable of reversing the sickle phenotype in a mouse model of SCD. These studies provide a ß-LV that will be beneficial for gene therapy of SCD by significantly reducing the cost of vector production and extending the vector supply.

SARS-CoV-2 infection of primary human lung epithelium for COVID-19 modeling and drug discovery.

Coronavirus disease 2019 (COVID-19) is the latest respiratory pandemic caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). Although infection initiates in the proximal airways, severe and sometimes fatal symptoms of the disease are caused by infection of the alveolar type 2 (AT2) cells of the distal lung and associated inflammation. In this study, we develop primary human lung epithelial infection models to understand initial responses of proximal and distal lung epithelium to SARS-CoV-2 infection. Differentiated air-liquid interface (ALI) cultures of proximal airway epithelium and alveosphere cultures of distal lung AT2 cells are readily infected by SARS-CoV-2, leading to an epithelial cell-autonomous proinflammatory response with increased expression of interferon signaling genes. Studies to validate the efficacy of selected candidate COVID-19 drugs confirm that remdesivir strongly suppresses viral infection/replication. We provide a relevant platform for study of COVID-19 pathobiology and for rapid drug screening against SARS-CoV-2 and emergent respiratory pathogens.

Dosing and Re-Administration of Lentiviral Vector for In Vivo Gene Therapy in Rhesus Monkeys and ADA-Deficient Mice.

Adenosine deaminase (ADA)-deficient mice and healthy rhesus monkeys were studied to determine the impact of age at treatment, vector dosage, dosing schedule, repeat administration, biodistribution, and immunogenicity after systemic delivery of lentiviral vectors (LVs). In Ada -/- mice, neonatal treatment resulted in broad vector marking across all tissues analyzed, whereas adult treatment resulted in marking restricted to the liver, spleen, and bone marrow. Intravenous administration to infant rhesus monkeys also resulted in dose-dependent marking in the liver, spleen, and bone marrow. Using an ELISA to monitor anti-vector antibody development, Ada -/- neonatal mice did not produce an antibody response, whereas Ada -/- adult mice produced a strong antibody response to vector administration. In mice and monkeys with repeat administration of LV, a strong anti-vector antibody response was shown in response to the second LV administration, which resulted in LV inactivation. Three separate doses administered to immune competent mice resulted in acute toxicity. Pegylation of the vesicular stomatitis virus G protein (VSV-G)-enveloped LVs showed a less robust anti-vector response but did not prevent the inactivation of the second LV administration. These studies identify important factors to consider related to age and timing of administration when implementing systemic delivery of LVs as a potential therapeutic agent.

Gene Therapy for Sickle Cell Disease: A Lentiviral Vector Comparison Study.

Sickle cell disease (SCD) is an inherited blood disorder caused by a single amino acid substitution in the ß-globin chain of hemoglobin. Gene therapy is a promising therapeutic alternative, particularly in patients lacking an allogeneic bone marrow (BM) donor. One of the major challenges for an effective gene therapy approach is the design of an efficient vector that combines high-level and long-term ß-globin expression with high infectivity in primary CD34+ cells. Two lentiviral vectors carrying an anti-sickling ß-globin transgene (AS3) were directly compared: the Lenti/ßAS3-FB, and Globe-AS3 with and without the FB insulator. The comparison was performed initially in human BM CD34+ cells derived from SCD patients in an in vitro model of erythroid differentiation. Additionally, the comparison was carried out in two in vivo models: First, an NOD SCID gamma mouse model was used to compare transduction efficiency and ß-globin expression in human BM CD34+ cells after transplant. Second, a sickle mouse model was used to analyze ß-globin expression produced from the vectors tested, as well as hematologic correction of the sickle phenotype. While minor differences were found in the vectors in the in vitro study (2.4-fold higher vector copy number in CD34+ cells when using Globe-AS3), no differences were noted in the overall correction of the SCD phenotype in the in vivo mouse model. This study provides a comprehensive in vitro and in vivo analysis of two globin lentiviral vectors, which is useful for determining the optimal candidate for SCD gene therapy.