Production of High-Titer Retrovirus and Lentivirus Vectors

WAVE3 Facilitates the Tumorigenesis and Metastasis of Tongue Squamous Cell Carcinoma via EMT

Wiskott-Aldrich syndrome protein family verprolin-homologous domain-containing protein 3 (WAVE3) is reported as an oncogene regulating cell proliferation and motility in multiple malignancies, while its role in tongue squamous cell carcinoma (TSCC) remains unknown. This study aimed to explore the expression and mechanism of WAVE3 in TSCC. We enrolled 64 TSCC patients admitted between June 2013 and February 2014 and collected their cancerous and adjacent normal tissues to determine WAVE3 expression by immunohistochemistry. The correlation of WAVE3 expression with TSCC patients' pathological characteristics was analyzed. Then, a 7-year follow-up was conducted to observe the value of WAVE3 in evaluating patient outcomes. In addition, human TSCC SCC9, SCC25, and CAL27 cells were purchased and detected by Cell Counting Kit-8 (CCK-8), Transwell, and scratch-wound assays for their proliferation, invasion, and migration capacities, while real-time quantitative PCR (qRT-PCR) and Western blotting were utilized to quantify WAVE3 and epithelial-mesenchymal transition (EMT)-related protein expression, respectively. The most active cell lines were selected to be infected with lentiviral vectors that silenced WAVE3 (named WAVE3-sh group) and overexpressed WAVE3 cDNA (named WAVE3-OE group) to observe the impacts of interfering WAVE3 expression on TSCC cell biological behavior. The positive expression of WAVE3 in TSCC tissue was found to be obviously enhanced and predominantly located in the cytoplasm. In addition, close correlations were identified between WAVE3 and T staging, clinical staging, lymphatic metastasis, distant metastasis, and differentiation degree (P < 0.05). Increased WAVE3 expression predicted an elevated risk of death, as indicated by the follow-up analysis (P < 0.05). SCC9 was selected for subsequent experiments among various TSCC cell lines studied because it showed the most potent ability to proliferate, invade, and migrate (P < 0.05). Silencing WAVE3 expression in SCC9 cells decreased cell proliferation, invasion, migration, and EMT-related protein expression (P < 0.05), while increasing WAVE3 expression promoted SCC9 viability. WAVE3, which was highly expressed in TSCC, promoted EMT in tumor cells and accelerated their proliferation, invasion, and migration, which might provide a new theoretical basis for molecular targeted therapy of TSCC in the future.

NCOA4 initiates ferritinophagy by binding GATE16 using two highly avid short linear interaction motifs

Cells carefully regulate cytosolic iron, which is a vital enzymatic cofactor, yet is toxic in excess. In mammalian cells, surplus iron is sequestered in ferritin cages that, in iron limiting conditions, are degraded through the selective autophagy pathway ferritinophagy to liberate free iron. Prior work identified the ferritinophagy receptor protein NCOA4, which links ferritin and LC3/GABARAP-family member GATE16, effectively tethering ferritin to the autophagic machinery. Here, we elucidate the molecular mechanism underlying this interaction, discovering two short linear motifs in NCOA4 that each bind GATE16 with weak affinity. These binding motifs are highly avid and, in concert, support high-affinity NCOA4•GATE16 complex formation. We further find the minimal NCOA4383-522 fragment bearing these motifs is sufficient for ferritinophagy and that both motifs are necessary for this activity. This work suggests a general mechanism wherein selective autophagy receptors can distinguish between the inactive soluble pools of LC3/GABARAPs and the active membrane-conjugated forms that drive autophagy. Finally, we find that iron decreases NCOA4383-522's affinity for GATE16, providing a plausible mechanism for iron-dependent regulation of ferritinophagy.

Unraveling the Nrf2-ARE Signaling Pathway in the DF-1 Chicken Fibroblast Cell Line: Insights into T-2 Toxin-Induced Oxidative Stress Regulation

The T-2 toxin (T2) poses a major threat to the health and productivity of animals. The present study aimed to investigate the regulatory mechanism of Nrf2 derived from broilers against T2-induced oxidative damage. DF-1 cells, including those with normal characteristics, as well as those overexpressing or with a knockout of specific components, were exposed to a 24 h treatment of 50 nM T2. The primary objective was to evaluate the indicators associated with oxidative stress and the expression of downstream antioxidant factors regulated by the Nrf2-ARE signaling pathway, at both the mRNA and protein levels. The findings of this study demonstrated a noteworthy relationship between the up-regulation of the Nrf2 protein and a considerable reduction in the oxidative stress levels within DF-1 cells (p < 0.05). Furthermore, this up-regulation was associated with a notable increase in the mRNA and protein levels of antioxidant factors downstream of the Nrf2-ARE signaling pathway (p < 0.05). Conversely, the down-regulation of the Nrf2 protein was linked to a marked elevation in oxidative stress levels in DF-1 cells (p < 0.05). Additionally, this down-regulation resulted in a significant decrease in both the mRNA and protein expression of antioxidant factors (p < 0.05). This experiment lays a theoretical foundation for investigating the detrimental impacts of T2 on broiler chickens. It also establishes a research framework for employing the Nrf2 protein in broiler chicken production and breeding. Moreover, it introduces novel insights for the prospective management of oxidative stress-related ailments in the livestock and poultry industry.

Rescue of GM3 synthase deficiency by spatially controlled, rAAV-mediated ST3GAL5 delivery

GM3 synthase deficiency (GM3SD) is an infantile-onset epileptic encephalopathy syndrome caused by biallelic loss-of-function mutations in ST3GAL5. Loss of ST3GAL5 activity in humans results in systemic ganglioside deficiency and severe neurological impairment. No disease-modifying treatment is currently available. Certain recombinant adeno-associated viruses (rAAVs) can cross the blood-brain barrier to induce widespread, long-term gene expression in the CNS and represent a promising therapeutic strategy. Here, we show that a first-generation rAAV-ST3GAL5 replacement vector using a ubiquitous promoter restored tissue ST3GAL5 expression and normalized cerebral gangliosides in patient-derived induced pluripotent stem cell neurons and brain tissue from St3gal5-KO mice but caused fatal hepatotoxicity when administered systemically. In contrast, a second-generation vector optimized for CNS-restricted ST3GAL5 expression, administered by either the intracerebroventricular or i.v. route at P1, allowed for safe and effective rescue of lethality and behavior impairment in symptomatic GM3SD mice up to a year. These results support further clinical development of ST3GAL5 gene therapy.

Therapeutical Significance of Serpina3n Subsequent Cerebral Ischemia via Cytotoxic Granzyme B Inactivation

Ischemic stroke is a devastating CNS insult with few clinical cures. Poor understanding of underlying mechanistic network is the primary limitation to develop novel curative therapies. Extracellular accumulation of granzyme B subsequent ischemia promotes neurodegeneration. Inhibition of granzyme B can be one of the potent strategies to mitigate neuronal damage. In present study, we investigated the effect of murine Serpina3n and human (homolog) SERPINA3 against cerebral ischemia through granzyme B inactivation. Recombinant Serpina3n/SERPINA3 were expressed by transfected 293 T cells, and eluted proteins were examined for postischemic influence both in vitro and in vivo. During in vitro test, Serpina3n was found effective enough to inhibit granzyme B, while SERPINA3 was ineffectual to counter cytotoxic protease. Treatment of hypoxic culture with recombinant Serpina3n/SERPINA3 significantly increased cell viability in dosage-dependent manner, recorded maximum at the highest concentration (4 mM). Infarct volume analysis confirmed that 50 mg/kg dosage of exogenous Serpina3n was adequate to reduce disease severity, while SERPINA3 lacked behind in analeptic effect. Immunohistochemical test, western blot analysis, and protease activity assay’s results illustrated successful diffusion of applied protein to the ischemic lesion and reactivity with the target protease. Taken together, our findings demonstrate therapeutic potential of Serpina3n by interfering granzyme B-mediated neuronal death subsequent cerebral ischemia.

Modulating immune responses to AAV by expanded polyclonal T-regs and capsid specific chimeric antigen receptor T-regulatory cells

Immune responses to adeno-associated virus (AAV) capsids limit the therapeutic potential of AAV gene therapy. Herein, we model clinical immune responses by generating AAV capsid-specific chimeric antigen receptor (AAV-CAR) T cells. We then modulate immune responses to AAV capsid with AAV-CAR regulatory T cells (Tregs). AAV-CAR Tregs in vitro display phenotypical Treg surface marker expression, and functional suppression of effector T cell proliferation and cytotoxicity. In mouse models, AAV-CAR Tregs mediated continued transgene expression from an immunogenic capsid, despite antibody responses, produced immunosuppressive cytokines, and decreased tissue inflammation. AAV-CAR Tregs are also able to bystander suppress immune responses to immunogenic transgenes similarly mediating continued transgene expression, producing immunosuppressive cytokines, and reducing tissue infiltration. Taken together, AAV-CAR T cells and AAV-CAR Tregs are directed and powerful immunosuppressive tools to model and modulate immune responses to AAV capsids and transgenes in the local environment.

Production of lentiviral vectors in suspension cells using low proportion of supercoiled circular plasmid DNA

The supercoiled circular (SC) topology form of plasmid DNA has been regarded to be advantageous over open circular or linearized analogue in transfection and expression efficiency, and therefore are largely demanded in the biopharmaceutical manufacturing. However, production of high-purity SC plasmid DNA would result in high manufacturing cost. The effect of SC proportion in plasmid DNA on the quality of packaged lentiviral vectors has never been reported. In this study, we established an efficient system for production of high-titer lentiviral vectors using suspension HEK293SF cells in serum-free media, and the lentiviral titer was not associated with the proportion of SC plasmid DNA. Plasmids DNA with different proportion of SC, open-circular, and linearized forms were prepared using the thermal denaturation method, and were transfected to adherent HEK293T or suspension HEK293SF cells for packaging of lentiviral vectors. The titer of lentiviral vectors from HEK293T cells, but not from HEK293SF cells, was significantly impaired when the proportion of SC plasmid DNA decreased from 60-80% to 30-40%. Further decrease of SC plasmid proportion to 3% led to a dramatic reduction of lentiviral titer no matter the packaging cell line was. However, lentiviral vectors from HEK293SF cells still showed a high titer even when the proportion of SC plasmid DNA was 3%. This study demonstrated that extremely high proportion of SC plasmid DNA was not required for packaging of high-titer lentiviral vector in HEK293SF cells, at least under our manufacturing process.

Organ-on-chip model shows that ATP release through connexin hemichannels drives spontaneous Ca2+ signaling in non-sensory cells of the greater epithelial ridge in the developing cochlea

Prior work supports the hypothesis that ATP release through connexin hemichannels drives spontaneous Ca2+ signaling in non-sensory cells of the greater epithelial ridge (GER) in the developing cochlea; however, direct proof is lacking. To address this issue, we plated cochlear organotypic cultures (COCs) and whole cell-based biosensors with nM ATP sensitivity (ATP-WCBs) at the bottom and top of an ad hoc designed transparent microfluidic chamber, respectively. By performing dual multiphoton Ca2+ imaging, we monitored the propagation of intercellular Ca2+ waves in the GER of COCs and ATP-dependent Ca2+ responses in overlying ATP-WCBs. Ca2+ signals in both COCs and ATP-WCBs were inhibited by supplementing the extracellular medium with ATP diphosphohydrolase (apyrase). Spontaneous Ca2+ signals were strongly depressed in the presence of Gjb6-/- COCs, in which connexin 30 (Cx30) is absent and connexin 26 (Cx26) is strongly downregulated. In contrast, spontaneous Ca2+ signals were not affected by replacement of Panx1-/- with Panx1+/+ COCs in the microfluidic chamber. Similar results were obtained by estimating ATP release from COCs using a classical luciferin-luciferase bioluminescence assay. Therefore, connexin hemichannels and not pannexin 1 channels mediate the release of ATP that is responsible for Ca2+ wave propagation in the developing mouse cochlea. The technological advances presented here have the potential to shed light on a plethora of unrelated open issues that involve paracrine signaling in physiology and pathology and cannot be addressed with standard methods.

Introducing Genes into Mammalian Cells: Viral Vectors

Over the years, many different viral vector systems have been developed to take advantage of the specific biological properties and tropisms of a large number of mammalian viruses. As a result, researchers wanting to introduce and/or express genes in mammalian cells have many options, as discussed here.

Rescue and characterization of a recombinant HY12 bovine enterovirus carrying a foreign HA epitope in the 3A nonstructural protein

Full-length infectious cDNA clones for recombinant HY12 bovine enteroviruses designated as rHY12-3A-2-HA, rHY12-3A-3-HA, and rHY12-3A-9-HA were constructed by the insertion of an epitope from influenza virus hemagglutinin (HA) at the N-terminus of the HY12-encoded 3A protein at amino acid positions 2, 3, and 9. The recombinant HY12 viruses expressing the HA epitope were rescued and characterized using immunoperoxidase monolayer assay, western blotting, and electron microscopy. The three rescued recombinant marker viruses showed similar characteristics, such as TCID₅₀ titer, plaque size, and growth properties, to those of parental rHY12 virus. Comparative analysis of the nucleotide sequences demonstrated the three recombinant marker viruses remained stable for 15 passages with no genetic changes. The recombinant viruses remained viable in various permissive cell lines, including BHK-21, Vero, and PK15 cells, suggesting that the insertion of the HA epitope tag had no effect on virus infectivity. Mice infected with the recombinant marker viruses and the parental virus produced anti-HY12-virus antibodies, while the recombinant marker viruses also produced anti-HA-epitope-tag antibodies. Taken together, these results demonstrate that HY12 viruses containing genetic markers may be useful tools for future investigations of the mechanisms of viral pathogenesis and virus replication, as well as for vaccine development.

A Flow Cytometry-Based Approach to Unravel Viral Interference with the MHC Class I Antigen Processing and Presentation Pathway

MHC class I molecules are an important component of the cell-mediated immune defense, presenting peptides to surveilling CD8⁺ cytotoxic T cells. During viral infection, MHC class I molecules carry and display viral peptides at the cell surface. CD8⁺ T cells that recognize these peptides will eliminate the virus-infected cells. Viruses counteract this highly sophisticated host detection system by downregulating cell surface expression of MHC class I molecules.In this chapter, we describe a flow cytometry-based method that can be used for the identification of viral gene products potentially responsible for evasion from MHC class I-restricted antigen presentation. The gene(s) of interest are expressed constitutively through lentiviral transduction of cells. Subsequently, MHC I surface expression is monitored using MHC class I-specific antibodies. Once the viral gene product responsible for MHC I downregulation has been identified, the same cells can be used to elucidate the mechanism of action. The stage at which interference with antigen processing occurs can be identified using specific assays. An essential step frequently targeted by viruses is the translocation of peptides into the ER by the transporter associated with antigen processing, TAP. TAP function can be measured using a highly specific in vitro assay involving flow cytometric evaluation of the import of a fluorescent peptide substrate.The protocol described in this chapter enables the identification of virus-encoded MHC class I inhibitors that hinder antigen processing and presentation. Subsequently, their mechanism of action can be unraveled; this knowledge may help to rectify their actions.

Titration of Lentivirus Vectors

The titer of a lentivirus vector is often expressed in transducing units per milliliter. This is a functional titer that reflects the lentivirus' ability to transduce a particular cell line under specific conditions. Transduction of other cell lines is likely to be different and will require optimization. 293T cells are used for production of lentivirus stocks, and they can be easily transduced with vesicular stomatitis virus glycoprotein (VSV-G) pseudotyped lentivirus vectors. Consequently, this cell line is commonly used to determine the functional titer of lentivirus vector stocks produced with this envelope. For lentivirus vectors encoding fluorescent proteins under the control of promoters functional in these cells, titration can be performed using the limiting dilution method or a flow cytometry-based method. For lentivirus vectors lacking a fluorescent marker, or for those carrying promoters that may not be functional in 293T cells, titer can be determined either by real-time polymerase chain reaction (PCR) quantification of viral genomes in genomic DNA from transduced cells or a p24 ELISA-based assay.

Monitoring Lentivirus Vector Stocks for Replication-Competent Viruses

The potential emergence of replication-competent lentiviruses (RCLs) during vector production and the significant biosafety risk that this represents has led to the development of lentivirus vector production systems to minimize the risk of generating RCLs. Second- and third-generation lentivirus vector production systems appear to be safe, because there are no reports of RCL generation in either system. Screening of lentivirus vector stocks for RCLs involves serial passaging of transduced cells for 30 d with weekly monitoring of p24 levels in supernatants using an ELISA Kit.