Production of Lentivirus for the Establishment of CAR-T Cells

Advances and opportunities in process analytical technologies for viral vector manufacturing

Viral vectors are an emerging, exciting class of biologics whose application in vaccines, oncology, and gene therapy has grown exponentially in recent years. Following first regulatory approval, this class of therapeutics has been vigorously pursued to treat monogenic disorders including orphan diseases, entering hundreds of new products into pipelines. Viral vector manufacturing supporting clinical efforts has spurred the introduction of a broad swath of analytical techniques dedicated to assessing the diverse and evolving panel of Critical Quality Attributes (CQAs) of these products. Herein, we provide an overview of the current state of analytics enabling measurement of CQAs such as capsid and vector identities, product titer, transduction efficiency, impurity clearance etc. We highlight orthogonal methods and discuss the advantages and limitations of these techniques while evaluating their adaptation as process analytical technologies. Finally, we identify gaps and propose opportunities in enabling existing technologies for real-time monitoring from hardware, software, and data analysis viewpoints for technology development within viral vector biomanufacturing.

Development and Evaluation of a Shrimp Virus (IHHNV)-Mediated Gene Transfer and Expression System for Shrimps

An efficient gene transfer and expression tool is lacking for shrimps and shrimp cells. To solve this, this study has developed a shrimp DNA virus-mediated gene transfer and expression system, consisting of insect Sf9 cells for viral packaging, the shrimp viral vector of pUC19-IHHNV-PH-GUS and the baculoviral vector of Bacmid or Bacmid-VP28 encoding the shrimp WSSV envelope protein VP28. The pUC19-IHHNV-PH-GUS vector was constructed by assembling the genomic DNA of shrimp infectious hypodermal and hematopoietic necrosis virus (IHHNV), which has shortened inverted terminal repeats, into a pUC19 backbone, and then an expression cassette of baculoviral polyhedron (PH) promoter-driven GUS (β-glucuronidase) reporter gene was inserted immediately downstream of IHHNV for proof-of-concept. It was found that the viral vector of pUC19-IHHNV-PH-GUS could be successfully packaged into IHHNV-like infective virions in the Sf9 cells, and the gene transfer efficiency of this system was evaluated and verified in three systems of Sf9 cells, shrimp hemolymph cells and tissues of infected shrimps, but the GUS expression could only be detected in cases where the viral vector was co-transfected or co-infected with a baculovirus of Bacmid or Bacmid-VP28 due to the Bacmid-dependence of the PH promoter. Moreover, the packaging and infection efficiencies could be significantly improved when Bacmid-VP28 was used instead of Bacmid.

Generation and application of immortalized sheep fetal fibroblast cell line

BACKGROUND

Primary sheep fetal fibroblasts (SFFCs) have emerged as a valuable resource for investigating the molecular and pathogenic mechanisms of orf viruses (ORFV). However, their utilization is considerably restricted due to the exorbitant expenses associated with their isolation and culture, their abbreviated lifespan, and the laborious procedure.

RESULTS

In our investigation, the primary SFFCs were obtained and immortalized by introducing a lentiviral recombinant plasmid containing the large T antigen from simian virus 40 (SV40). The expression of fibronectin and vimentin proteins, activity of SV40 large T antigen, cell proliferation assays, and analysis of programmed cell death revealed that the immortalized large T antigen SFFCs (TSFFCs) maintained the same physiological characteristics and biological functions as the primary SFFCs. Moreover, TSFFCs demonstrated robust resistance to apoptosis, extended lifespan, and enhanced proliferative activity compared to primary SFFCs. Notably, the primary SFFCs did not undergo in vitro transformation or exhibit any indications of malignancy in nude mice. Furthermore, the immortalized TSFFCs displayed live ORFV vaccine susceptibility.

CONCLUSIONS

Immortalized TSFFCs present valuable in vitro models for exploring the characteristics of ORFV using various techniques. This indicates their potential for secure utilization in future studies involving virus isolation, vaccine development, and drug screening.

Advances in CAR-Engineered Immune Cell Generation: Engineering Approaches and Sourcing Strategies

Chimeric antigen receptor T-cell (CAR-T) therapy has emerged as a highly efficacious treatment modality for refractory and relapsed hematopoietic malignancies in recent years. Furthermore, CAR technologies for cancer immunotherapy have expanded from CAR-T to CAR-natural killer cell (CAR-NK), CAR-cytokine-induced killer cell (CAR-CIK), and CAR-macrophage (CAR-MΦ) therapy. Nevertheless, the high cost and complex manufacturing processes of ex vivo generation of autologous CAR products have hampered broader application. There is an urgent need to develop an efficient and economical paradigm shift for exploring new sourcing strategies and engineering approaches toward generating CAR-engineered immune cells to benefit cancer patients. Currently, researchers are actively investigating various strategies to optimize the preparation and sourcing of these potent immunotherapeutic agents. In this work, the latest research progress is summarized. Perspectives on the future of CAR-engineered immune cell manufacturing are provided, and the engineering approaches, and diverse sources used for their development are focused upon.

In Situ Programming of CAR-T Cells: A Pressing Need in Modern Immunotherapy

Chimeric antigen receptor-T (CAR-T) cell-based therapy has become a successful option for treatment of numerous hematological malignancies, but also raises hope in a range of non-malignant diseases. However, in a traditional approach, generation of CAR-T cells is associated with the separation of patient's lymphocytes, their in vitro modification, and expansion and infusion back into patient's bloodstream. This classical protocol is complex, time-consuming, and expensive. Those problems could be solved by successful protocols to produce CAR-T cells, but also CAR-natural killer cells or CAR macrophages, in situ, using viral platforms or non-viral delivery systems. Moreover, it was demonstrated that in situ CAR-T induction may be associated with reduced risk of the most common toxicities associated with CAR-T therapy, such as cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and "on-target, off-tumor" toxicity. This review aims to summarize the current state-of-the-art and future perspectives for the in situ-produced CAR-T cells. Indeed, preclinical work in this area, including animal studies, raises hope for prospective translational development and validation in practical medicine of strategies for in situ generation of CAR-bearing immune effector cells.

Targeted CD7 CAR T-cells for treatment of T-Lymphocyte leukemia and lymphoma and acute myeloid leukemia: recent advances

The high expression of CD7 targets in T-cell acute lymphoblastic leukemia (T-ALL) and T-lymphoma has attracted considerable attention from researchers. However, because CD7 chimeric antigen receptor (CAR) T-cells undergo fratricide, CD7 CAR T-cells develop an exhaustion phenotype that impairs the effect of CAR T-cells. There have been significant breakthroughs in CD7-targeted CAR T-cell therapy in the past few years. The advent of gene editing, protein blockers, and other approaches has effectively overcome the adverse effects of conventional methods of CD7 CAR T-cells. This review, in conjunction with recent advances in the 64^th annual meeting of the American Society of Hematology (ASH), provides a summary of the meaningful achievements in CD7 CAR T-cell generations and clinical trials over the last few years.

Education and Empowering Special Forces to Eradicate Secret Defectors: Immune System-Based Treatment Approaches for Mature T- and NK-Cell Malignancies

Mature T- and NK-cell leukemia/lymphoma (MTCL/L) constitute a heterogeneous group of, currently, 30 distinct neoplastic entities that are overall rare, and all present with a challenging molecular markup. Thus, so far, the use of first-line cancer treatment modalities, including chemotherapies, achieve only limited clinical responses associated with discouraging prognoses. Recently, cancer immunotherapy has evolved rapidly, allowing us to help patients with, e.g., solid tumors and also relapsed/refractory B-cell malignancies to achieve durable clinical responses. In this review, we systematically unveiled the distinct immunotherapeutic approaches available, emphasizing the special impediments faced when trying to employ immune system defense mechanisms to target 'one of their own-gone mad'. We summarized the preclinical and clinical efforts made to employ the various platforms of cancer immunotherapies including antibody-drug conjugates, monoclonal as well as bispecific antibodies, immune-checkpoint blockades, and CAR T cell therapies. We emphasized the challenges to, but also the goals of, what needs to be done to achieve similar successes as seen for B-cell entities.

Generation and application of immortalized sertoli cell line from sheep testis

Primary sheep testicular Sertoli cells (STSCs) are ideal for investigating the molecular and pathogenic processes of capripoxvirus. However, the high cost of isolation and culture of primary STSCs, time-consuming operation, and short lifespan greatly limit their real-world application. In our study, the primary STSCs were isolated and immortalized by transfection of a lentiviral recombinant plasmid containing simian virus 40 (SV40) large T antigen. Androgen-binding protein (ABP) and vimentin (VIM) protein expression, SV40 large T antigen activity, proliferation assays, and apoptosis analysis results showed that immortalized large T antigen STSCs (TSTSCs) still had the same physiological characteristics and biological functions as primary STSCs. Moreover, immortalized TSTSCs had strong anti-apoptosis ability, extended lifespan, and enhanced proliferative activity compared to primary STSCs, which had not transformed in vitro and showed any signs of malignancy phenotype in nude mice. Besides, immortalized TSTSCs were susceptible to goatpox virus (GTPV), lumpy skin disease virus (LSDV), and Orf virus (ORFV). In conclusion, immortalized TSTSCs are useful in vitro models to study GTPV, LSDV, and ORFV in a wide range of ways, suggesting that it can be safely used in virus isolation, vaccine and drug screening studies in future.

Vectored Immunoprophylaxis and Treatment of SARS-CoV-2 Infection

Vectored immunoprophylaxis was first developed as a means to establish engineered immunity to HIV through the use of an adeno-associated viral vector expressing a broadly neutralizing antibody. We have applied this concept to establish long-term prophylaxis against SARS-CoV-2 by adeno-associated and lentiviral vectors expressing a high affinity ACE2 decoy receptor. Administration of decoy-expressing AAV vectors based on AAV2.retro and AAV6.2 by intranasal instillation or intramuscular injection protected mice against high-titered SARS-CoV-2 infection. AAV and lentiviral vectored immunoprophylaxis was durable and active against recent SARS-CoV-2 Omicron subvariants. The AAV vectors were also effective when administered up to 24 hours post-infection. Vectored immunoprophylaxis could be of value for immunocompromised individuals for whom vaccination is not practical and as a means to rapidly establish protection from infection. Unlike monoclonal antibody therapy, the approach is expected to remain active despite continued evolution viral variants.

Harnessing the Potential of Chimeric Antigen Receptor T-Cell Therapy for the Treatment of T-Cell Malignancies: A Dare or Double Dare?

Historical standard of care treatments of T-cell malignancies generally entailed the use of cytotoxic and depleting approaches. These strategies are, however, poorly validated and record dismal long-term outcomes. More recently, the introduction and approval of chimeric antigen receptor (CAR)-T cell therapy has revolutionized the therapy of B-cell malignancies. Translating this success to the T-cell compartment has so far proven hazardous, entangled by risks of fratricide, T-cell aplasia, and product contamination by malignant cells. Several strategies have been utilized to overcome these challenges. These include the targeting of a selective cognate antigen exclusive to T-cells or a subset of T-cells, disruption of target antigen expression on CAR-T constructs, use of safety switches, non-viral transduction, and the introduction of allogeneic compounds and gene editing technologies. We herein overview these historical challenges and revisit the opportunities provided as potential solutions. An in-depth understanding of the tumor microenvironment is required to optimally harness the potential of the immune system to treat T-cell malignancies.

[Effects of sodium iodide symporter co-expression on proliferation and cytotoxic activity of chimeric antigen receptor T cells in vitro]

OBJECTIVE

To investigate the effects of co-expression of sodium iodide symporter (NIS) reporter gene on the proliferation and cytotoxic activity of chimeric antigen receptor (CAR)-T cells in vitro.

METHODS

T cells expressing CD19 CAR (CAR-T cells), NIS reporter gene (NIS-T cells), and both (NIS-CAR-T cells) were prepared by lentiviral infection. The transfection rates of NIS and CAR were determined by flow cytometry, and the cell proliferation rate was assessed using CCK-8 assay at 24, 48 and 72 h of routine cell culture. The T cells were co-cultured with Nalm6 tumor cells at the effector-target ratios of 1∶2, 1∶1, 2∶1 and 4∶1 for 24, 48 and 72 h, and the cytotoxicity of CAR-T cells to the tumor cells was evaluated using lactate dehydrogenase (LDH) assay. ELISA was used to detect the release of IFN-γ and TNF-β in the co-culture supernatant, and the function of NIS was detected with iodine uptake test.

RESULTS

The CAR transfection rate was 91.91% in CAR-T cells and 99.41% in NIS-CAR-T cells; the NIS transfection rate was 47.83% in NIS-T cells and 50.24% in NIS- CAR-T cells. No significant difference in the proliferation rate was observed between CAR-T and NIS-CAR-T cells cultured for 24, 48 or 72 h (P> 0.05). In the co-cultures with different effector-target ratios, the tumor cell killing rate was significantly higher in CAR-T group than in NIS-CAR-T group at 24 h (P < 0.05), but no significant difference was observed between the two groups at 48 h or 72 h (P>0.05). Higher IFN-γ and TNF-β release levels were detected in both CAR-T and NIS-CAR-T groups than in the control group (P < 0.05). NIS-T cells and NIS-CAR-T cells showed similar capacity of specific iodine uptake (P>0.05), which was significantly higher than that in the control T cells (P < 0.05).

CONCLUSION

The co-expression of the NIS reporter gene does not affect CAR expression, proliferation or tumor cell-killing ability of CAR-T cells.

Opportunities and obstacles for the melanoma immunotherapy using T cell and chimeric antigen receptor T (CAR-T) applications: a literature review

Chimeric antigen receptor T (CAR-T) cell therapy procedure includes taking personal T cells and processing or genetic engineering using specific antigens and in vitro expanding and eventually infusing into the patient's body to unleash immune responses. Adoptive cell therapy (ACT) includes lymphocytes taking, in vitro selection and expansion and processing for stimulation or activation and infusion into the patient's body. Immune checkpoint inhibitors (ICIs), ACT and CAR-T cell therapies have demonstrated acceptable results. However, rare CAR-T cells tissue infiltration, off-target toxicity and resistance development include main disadvantages of CAR-T cell based therapy. Selection of suitable target antigens and novel engineered immune cells are warranted in future studies using "surfaceome" analysis. Employment of cytokines (IL-2, IL-7) for T cells activation has been also associated with specific anti-melanoma function which overcome telomeres shortening and further T cells differentiation. In resistant cases, rapidly accelerated fibrosarcoma B-type and mitogen-activated extracellular signal-regulated kinase inhibitors have been mostly applied. The aim of this study was evaluation of CAR-T cell and adoptive cell therapies efficiency for the treatment of melanoma.

Optimization of SARS-CoV-2 Pseudovirion Production in Lentivirus Backbone With a Novel Liposomal System

Due to the fast mutating nature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the development of novel therapeutics, vaccines, and evaluating the efficacies of existing one’s against the mutated strains is critical for containing the virus. Pseudotyped SARS-CoV-2 viruses are proven to be instrumental in evaluating the efficiencies of therapeutics, owing to their ease in application and safety when compared to handling the live virus. However, a comprehensive protocol that includes selecting transfection reagents, validating different packaging systems for high-throughput screening of neutralizing antibodies, is still a requisite. To this end, we designed and synthesized amide linker-based cationic lipids with varying hydrophilic head groups from dimethyl (Lipo-DME) to methyl, ethylhydroxyl (Lipo-MeOH), and diethylhydroxyl (Lipo-DOH) keeping the hydrophobic tail, stearic acid, as constant. Among the liposomal formulations of these lipids, Lipo-DOH was found to be superior in delivering plasmids and demonstrated comparable transfection efficiencies with commercial standard Lipofectamine 3000. We further used Lipo-DOH for lentivirus and SARS-CoV-2 pseudovirion preparation. For comparing different lentivirus packaging systems, we optimized conditions using Addgene and BEI systems and found that the BEI lenti plasmid system was found to be efficient in making lentiviruses using Lipo-DOH. Using the optimized transfection reagent and the lentivirus system, we developed a robust protocol for the generation of SARS-CoV-2 pseudovirions and characterized their infectivity in human ACE2 expressing HEK-293T cells and neutralizing properties in IgG against spike protein of SARS-CoV-2 positive human sera from individuals recovered from COVID-19.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

Lentiviral Vectors for T Cell Engineering: Clinical Applications, Bioprocessing and Future Perspectives

Lentiviral vectors have played a critical role in the emergence of gene-modified cell therapies, specifically T cell therapies. Tisagenlecleucel (Kymriah), axicabtagene ciloleucel (Yescarta) and most recently brexucabtagene autoleucel (Tecartus) are examples of T cell therapies which are now commercially available for distribution after successfully obtaining EMA and FDA approval for the treatment of blood cancers. All three therapies rely on retroviral vectors to transduce the therapeutic chimeric antigen receptor (CAR) into T lymphocytes. Although these innovations represent promising new therapeutic avenues, major obstacles remain in making them readily available tools for medical care. This article reviews the biological principles as well as the bioprocessing of lentiviral (LV) vectors and adoptive T cell therapy. Clinical and engineering successes, shortcomings and future opportunities are also discussed. The development of Good Manufacturing Practice (GMP)-compliant instruments, technologies and protocols will play an essential role in the development of LV-engineered T cell therapies.

Modular Lentiviral Vectors for Highly Efficient Transgene Expression in Resting Immune Cells

Gene/cell therapies are promising strategies for the many presently incurable diseases. A key step in this process is the efficient delivery of genes and gene-editing enzymes to many cell types that may be resistant to lentiviral vector transduction. Herein we describe tuning of a lentiviral gene therapy platform to focus on genetic modifications of resting CD4⁺ T cells. The motivation for this was to find solutions for HIV gene therapy efforts. Through selection of the optimal viral envelope and further modification to its expression, lentiviral fusogenic delivery into resting CD4⁺ T cells exceeded 80%, yet Sterile Alpha Motif and HD domain 1 (SAMHD1) dependent and independent intracellular restriction factors within resting T cells then dominate delivery and integration of lentiviral cargo. Overcoming SAMHD1-imposed restrictions, only observed up to 6-fold increase in transduction, with maximal gene delivery and expression of 35%. To test if the biologically limiting steps of lentiviral delivery are reverse transcription and integration, we re-engineered lentiviral vectors to simply express biologically active mRNA to direct transgene expression in the cytoplasm. In this setting, we observed gene expression in up to 65% of resting CD4⁺ T cells using unconcentrated MS2 lentivirus-like particles (MS2-LVLPs). Taken together, our findings support a gene therapy platform that could be readily used in resting T cell gene editing.

In Situ Programming of CAR T Cells

Gene therapy makes it possible to engineer chimeric antigen receptors (CARs) to create T cells that target specific diseases. However, current approaches require elaborate and expensive protocols to manufacture engineered T cells ex vivo, putting this therapy beyond the reach of many patients who might benefit. A solution could be to program T cells in vivo. Here, we evaluate the clinical need for in situ CAR T cell programming, compare competing technologies, review current progress, and provide a perspective on the long-term impact of this emerging and rapidly flourishing biotechnology field.

The Advances and Challenges of NK Cell-Based Cancer Immunotherapy

Natural killer (NK) cells can be widely applied for cancer immunotherapy due to their ability to lyse tumor targets without prior sensitization or human leukocyte antigens-matching. Several NK-based therapeutic approaches have been attempted in clinical practice, but their efficacy is not sufficient to suppress tumor development mainly because of lacking specificity. To this end, the engineering of NK cells with T cell receptor along with CD3 subunits (TCR-NK) has been developed to increase the reactivity and recognition specificity of NK cells toward tumor cells. Here, we review recent advances in redirecting NK cells for cancer immunotherapy and discuss the major challenges and future explorations for their clinical applications.

Preclinical Development of Autologous Hematopoietic Stem Cell-Based Gene Therapy for Immune Deficiencies: A Journey from Mouse Cage to Bed Side

Recent clinical trials using patient’s own corrected hematopoietic stem cells (HSCs), such as for primary immunodeficiencies (Adenosine deaminase (ADA) deficiency, X-linked Severe Combined Immunodeficiency (SCID), X-linked chronic granulomatous disease (CGD), Wiskott–Aldrich Syndrome (WAS)), have yielded promising results in the clinic; endorsing gene therapy to become standard therapy for a number of diseases. However, the journey to achieve such a successful therapy is not easy, and several challenges have to be overcome. In this review, we will address several different challenges in the development of gene therapy for immune deficiencies using our own experience with Recombinase-activating gene 1 (RAG1) SCID as an example. We will discuss product development (targeting of the therapeutic cells and choice of a suitable vector and delivery method), the proof-of-concept (in vitro and in vivo efficacy, toxicology, and safety), and the final release steps to the clinic (scaling up, good manufacturing practice (GMP) procedures/protocols and regulatory hurdles).

Antibody-Based CAR T Cells Produced by Lentiviral Transduction

One promising approach to treat hematologic malignancies is the usage of patient-derived CAR T cells. There are continuous efforts to improve the function of these cells, to optimize their receptor, and to use them for the treatment of additional types of cancer and especially solid tumors. In this protocol, an easy and reliable approach for CAR T cell generation is described. T cells are first isolated from peripheral blood (here: leukoreduction system chambers) and afterwards activated for one day with anti-CD3/CD28 Dynabeads. The gene transfer is performed by lentiviral transduction and gene transfer rate can be verified by flowcytometric analysis. Six days after transduction, the stimulatory Dynabeads are removed. T cells are cultured in interleukin-2 conditioned medium for several days for expansion. There is an option to expand CAR T cells further by co-incubation with irradiated, antigen-expressing feeder cell lines. The CAR T cells are ready to use after 10 (without feeder cell expansion) to 24 days (with feeder cell expansion). © 2020 The Authors. Basic Protocol: Generation of CAR T cells by lentiviral transduction.