This was a single-arm, multicenter, open-label phase I trial. Lentiviral vectors (LV) carrying the ABCD1 gene (LV-ABCD1) was directly injected into the brain of patients with childhood cerebral adrenoleukodystrophy (CCALD), and multi-site injection was performed. The injection dose increased from 200 to 1600 μL (vector titer: 1×109 transduction units per mL (TU/mL)), and the average dose per kilogram body weight ranges from 8 to 63.6 μL/kg. The primary endpoint was safety, dose-exploration and immunogenicity and the secondary endpoint was initial evaluation of efficacy and the expression of ABCD1 protein. A total of 7 patients participated in this phase I study and were followed for 1 year. No injection-related serious adverse event or death occurred. Common adverse events associated with the injection were irritability (71%, 5/7) and fever (37.2-38.5 ℃, 57%, 4/7). Adverse events were mild and self-limited, or resolved within 3 d of symptomatic treatment. The maximal tolerable dose is 1600 μL. In 5 cases (83.3%, 5/6), no lentivirus associated antibodies were detected. The overall survival at 1-year was 100%. The ABCD1 protein expression was detected in neutrophils, monocytes and lymphocytes. This study suggests that the intracerebral injection of LV-ABCD1 for CCALD is safe and can achieve successful LV transduction in vivo; even the maximal dose did not increase the risk of adverse events. Furthermore, the direct LV-ABCD1 injection displayed low immunogenicity. In addition, the effectiveness of intracerebral LV-ABCD1 injection has been preliminarily demonstrated while further investigation is needed. This study has been registered in the Chinese Clinical Trial Registry (https://www.chictr.org.cn/, registration number: ChiCTR1900026649).

Lentiviral vectors have markedly enhanced gene therapy efficiency in treating congenital diseases, but their long-term safety remains controversial. Most gene therapies for congenital eye diseases need to be carried out at early ages, yet the assessment of related risks to ocular development posed by lentiviral vectors is challenging. Utilizing single-cell transcriptomic profiling on human retinal organoids, this study explored the impact of lentiviral vectors on the retinal development and found that lentiviral vectors can cause retinal precursor cells to shift toward photoreceptor fate through the up-regulation of key fate-determining genes such as PRDM1. Further investigation demonstrated that the intron and intergenic region of PRDM1 was bound by PHLDA1, which was also up-regulated by lentiviral vectors exposure. Importantly, knockdown of PHLDA1 successfully suppressed the lentivirus-induced differentiation bias of photoreceptor cells. The findings also suggest that while lentiviral vectors may disrupt the fate determination of retinal precursor cells, posing risks in early-stage retinal gene therapy, these risks could potentially be reduced by inhibiting the PHLDA1-PRDM1 axis.

Clustered regularly interspersed short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has revolutionized the field of gene therapy as it has enabled precise genome editing with unprecedented accuracy and efficiency, paving the way for clinical applications to treat otherwise incurable genetic disorders. Typically, precise genome editing requires the delivery of multiple components to the target cells that, depending on the editing platform used, may include messenger RNA (mRNA), protein complexes, and DNA fragments. For clinical purposes, these have to be efficiently delivered into transplantable cells, such as primary T lymphocytes or hematopoietic stem and progenitor cells that are typically sensitive to exogenous substances. This challenge has limited the broad applicability of precise gene therapy applications to those strategies for which efficient delivery methods are available. Electroporation-based methodologies have been generally applied for gene editing applications, but procedure-associated toxicity has represented a major burden. With the advent of novel and less disruptive methodologies to deliver genetic cargo to transplantable cells, it is now possible to safely and efficiently deliver multiple components for precise genome editing, thus expanding the applicability of these strategies. In this review, we describe the different delivery systems available for genome editing components, including viral and non-viral systems, highlighting their advantages, limitations, and recent clinical applications. Recent improvements to these delivery methods to achieve cell specificity represent a critical development that may enable in vivo targeting in the future and will certainly play a pivotal role in the gene therapy field.

UNASSIGNED: The present study examined the protective potential of human adipose tissue-derived mesenchymal stem cells (hASCs) modified to overexpress alpha-1 antitrypsin (AAT), in a mouse model of the liver fibrosis.
UNASSIGNED: For the treatment of end-stage liver diseases, cell therapy has emerged as a promising noninvasive alternative to liver transplantation. Mesenchymal stem cells (MSCs) are being evaluated due to their dual capabilities of promoting liver regeneration and modulating the pathogenic inflammation of the immune system.
UNASSIGNED: Liver fibrosis was induced in mice via the intraperitoneal injection of carbon tetrachloride (CCl4). MSCs were extracted from the human adipose tissue. After stemness confirmation, the cells were transduced with the lentiviruses containing the AAT gene, and then injected into the mice\'s tail vein. Fourteen days\' post-transplantation, mice were sacrificed, and blood and tissue samples were collected for analysis. Important liver enzymes, including alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin, and total bilirubin (TB), were measured. Histological studies were carried out using the hematoxylin and eosin (H&E), as well as Masson\'s trichrome (MT) staining.
UNASSIGNED: Compared to hASCs, treatment with AAT-hASCs resulted in greater reductions in ALT, AST, ALP, and TB, as well as normalized albumin levels. AAT-hASCs promoted enhanced liver regeneration histologically, likely attributable to anti-inflammatory and anti-proteolytic properties of AAT.
UNASSIGNED: These findings indicate AAT-engineered hASCs as a promising cell-gene therapy candidate for further study in liver cirrhosis models.

Lentiviral gene transfer represents a versatile and powerful method for genetic transduction of many cell lines and primary cells including \"hard-to-transfect\" cells. As a consequence of the integration of the recombinant lentiviral vector into the cellular genome, the transgene is stably maintained, and long-term producing cells are established. Here, we describe the current state of the art and give details for lab-scale production of lentiviral vectors as well as for infection and titration of the viral vectors.

Successful cell and gene therapy clinical trials have resulted in the US Food and Drug Administration and European Medicines Agency approving their use for treatment of patients with certain types of cancers and monogenetic diseases. These novel therapies, which rely heavily on lentiviral vectors to deliver therapeutic transgenes to patient cells, have driven additional investigations, increasing demand for both pre-clinical and current Good Manufacturing Practices-grade viral vectors. To better support novel studies by improving current production methods, we report the development of a genetically modified HEK293T-based cell line that is null for expression of both Protein Kinase R and Beta-2 microglobulin and grows in suspension using serum-free media, SJ293TS-DPB. Absence of Protein Kinase R increased anti-sense lentiviral vector titers by more than 7-fold, while absence of Beta-2 microglobulin, a key component of major histocompatibility complex class I molecules, has been reported to reduce the immunogenicity of lentiviral particles. Furthermore, we describe an improved methodology for culturing SJ293TS-DPB that facilitates expansion, reduces handling, and increases titers by 2-fold compared with previous methods. SJ293TS-DPB stably produced lentiviral vectors for over 4 months and generated lentiviral vectors that efficiently transduce healthy human donor T cells and CD34+ hematopoietic stem cells.

In this editorial we comment on the article by Wei et al, published in the recent issue of the World Journal of Clinical Oncology. The authors investigated the role of Transmembrane 9 superfamily member 1 (TM9SF1) protein in bladder cancer (BC) carcinogenesis. Lentiviral vectors were used to achieve silencing or overexpression of TM9SF1 gene in three BC cell lines. These cell lines were then subject to cell counting kit 8, wound-healing assay, transwell assay, and flow cytometry. Proliferation, migration, and invasion of BC cells were increased in cell lines subjected to TM9SF1 overexpression. TM9SF1 silencing inhibited proliferation, migration and invasion of BC cells. The authors conclude that TM9SF1 may be an oncogene in bladder cancer pathogenesis.

Lentiviral vectors (LV) are efficient vehicles for in vivo gene delivery to the liver. LV integration into the chromatin of target cells ensures their transmission upon proliferation, thus allowing potentially life-long gene therapy following a single administration, even to young individuals. The glycoprotein of the vesicular stomatitis virus (VSV.G) is widely used to pseudotype LV, as it confers broad tropism and high stability. The baculovirus-derived GP64 envelope protein has been proposed as an alternative for in vivo liver-directed gene therapy. Here, we perform a detailed comparison of VSV.G- and GP64-pseudotyped LV in vitro and in vivo. We report that VSV.G-LV transduced hepatocytes better than GP64-LV, however the latter showed improved transduction of liver sinusoidal endothelial cells (LSEC). Combining GP64-pseudotyping with the high surface content of the phagocytosis inhibitor CD47 further enhanced LSEC transduction. Coagulation factor VIII (FVIII), the gene mutated in hemophilia A, is naturally expressed by LSEC, thus we exploited GP64-LV to deliver a FVIII transgene under the control of the endogenous FVIII promoter and achieved therapeutic amounts of FVIII and correction of hemophilia A mice.

Patients with stress-triggered major depression disorders (MDD) can often seek comfort or temporary relief through alcohol consumption, as they may turn to it as a means of self-medication or coping with overwhelming emotions. The use of alcohol as a coping mechanism for stressful events can escalate, fostering a cycle where the temporary relief it provides from depression can deepen into alcohol dependence, exacerbating both conditions. Although, the specific mechanisms involved in stress-triggered alcohol dependence and MDD comorbidities are not well understood, a large body of literature suggests that the serotonin transporter (SERT) plays a critical role in these abnormalities. To further investigate this hypothesis, we used a lentiviral-mediated knockdown approach to examine the role of hippocampal SERT knockdown in social defeat stress-elicited depression like behavior and ethanol-induced place preference (CPP). The results showed that social defeat stress-pro depressant effects were reversed following SERT knockdown demonstrated by increased sucrose preference, shorter latency to feed in the novelty suppressed feeding test, and decreased immobility time in the tail suspension and forced swim tests. Moreover, and most importantly, social stress-induced ethanol-CPP acquisition and reinstatement were significantly reduced following hippocampal SERT knockdown using short hairpin RNA shRNA-expressing lentiviral vectors. Finally, we confirmed that SERT hippocampal mRNA expression correlated with measures of depression- and ethanol-related behaviors by Pearson\'s correlation analysis. Taken together, our data suggest that hippocampal serotoninergic system is involved in social stress-triggered mood disorders as well as in the acquisition and retrieval of ethanol contextual memory and that blockade of this transporter can decrease ethanol rewarding properties.

While studying transgene expression after systemic administration of lentiviral vectors, we found that splenic B cells are robustly transduced, regardless of the types of pseudotyped envelope proteins. However, the administration of two different pseudotypes resulted in transduction of two distinct B cell populations, suggesting that each pseudotype uses unique and specific receptors for its attachment and entry into splenic B cells. Single-cell RNA sequencing analysis of the transduced cells demonstrated that different pseudotypes transduce distinct B cell subpopulations characterized by specific B cell receptor (BCR) genotypes. Functional analysis of the BCRs of the transduced cells demonstrated that BCRs specific to the pseudotyping envelope proteins mediate viral entry, enabling the vectors to selectively transduce the B cell populations that are capable of producing antibodies specific to their envelope proteins. Lentiviral vector entry via the BCR activated the transduced B cells and induced proliferation and differentiation into mature effectors, such as memory B and plasma cells. BCR-mediated viral entry into clonally specific B cell subpopulations raises new concepts for understanding the biodistribution of transgene expression after systemic administration of lentiviral vectors and offers new opportunities for BCR-targeted gene delivery by pseudotyped lentiviral vectors.