Enabling mRNA medicine for brain tumors

mRNA is a new class of drugs that has the potential to revolutionize the treatment of brain tumors. Thanks to the COVID-19 mRNA vaccines and numerous therapy-based clinical trials, it is now clear that lipid nanoparticles (LNPs) are a clinically viable means to deliver RNA therapeutics. However, LNP-mediated mRNA delivery to brain tumors remains elusive. Over the past decade, numerous studies have shown that tumor cells communicate with each other via small extracellular vesicles, which are around 100 nm in diameter and consist of lipid bilayer membrane similar to synthetic lipidbased nanocarriers. We hypothesized that rationally designed LNPs based on extracellular vesicle mimicry would enable efficient delivery of RNA therapeutics to brain tumors without undue toxicity. We synthesized LNPs using four components similar to the formulation used in the mRNA COVID19 vaccines (Moderna and Pfizer): ionizable lipid, cholesterol, helper lipid and polyethylene glycol (PEG)-lipid. For the in vitro screen, we tested ten classes of helper lipids based on their abundance in extracellular vesicle membranes, commercial availability, and large-scale production feasibility while keeping rest of the LNP components unchanged. The transfection kinetics of GFP mRNA encapsulated in LNPs and doped with 16 mol% of helper lipids was tested using GL261, U87 and SIM-A9 cell lines. Several LNP formations resulted in stable transfection (upto 5 days) of GFP mRNA in all the cell lines tested in vitro. The successful LNP candidates (enabling >80% transfection efficacy) were then tested in vivo to deliver luciferase mRNA to brain tumors via intrathecal administration in a syngeneic glioblastoma (GBM) mouse model, which confirmed luciferase expression in brain tumors in the cortex. LNPs were then tested to deliver Cre recombinase mRNA in syngeneic GBM mouse model genetically modified to express tdTomato under LoxP marker cassette that enabled identification of LNP targeted cells. mRNA was successfully delivered to tumor cells (70-80% transfected) and a range of different cells in the tumor microenvironment, including tumor-associated macrophages (80-90% transfected), neurons (31- 40% transfected), neural stem cells (39-62% transfected), oligodendrocytes (70-80% transfected) and astrocytes (44-76% transfected). Then, LNP formulations were assessed for delivering Cas9 mRNA and CD81 sgRNA (model protein) in murine syngeneic GBM model to enable gene editing in brain tumor cells. Sanger sequencing showed that CRISPR-Cas9 editing was successful in ~94% of brain tumor cells in vivo. In conclusion, we have developed a library of safe LNPs that can transfect GBM cells in vivo with high efficacy. This technology can potentially be used to develop novel mRNA therapies for GBM by delivering single or multiple mRNAs and holds great potential as a tool to study brain tumor biology.

Exosomes/EVs: IMMUNOMODULATORY EFFECTS OF AMNITOIC FLUID EXTRACELLULAR VESICLES IN AN IN-VITRO MODEL OF IMMUNE ACTIVATION

Background & Aim: Amniotic fluid (AF)-derived EVs are currently under investigation for use as anti-inflammatory therapeutics in COVID-19 and COVID-19 long haulers. The dysregulation of the immune response induced by SARS-COV-2 is a key driver of both acute COVID-19 induced lung injury and long term COVID-19 sequela. There is a clear need to identify therapeutics that suppress excessive inflammation and reduce immune cell exhaustion to improve patient short term and long-term outcomes. Amniotic fluid (AF)- derived extracellular vesicles (EVs) have previously been shown to deliver anti-inflammatory and immune-modulatory signals to diverse cellular targets. We aimed to test if AF-EVs carry immune-suppressive molecules and can suppress T-cell immune activation and exhaustion in vitro. Methods, Results & Conclusion(s): The AF-EV biologic tested was derived from AF collected from consenting donors during planned, fullterm cesarean sections. AF was centrifuged and filtered to remove cellular debris and create a product containing AF-EVs and soluble extracellular components. Fluorescent EXODOT analysis was performed to demonstrate the presence of EV markers CD9, CD81, ALIX, and immune suppressive molecule PD-L1. T-cell activation/exhaustion was induced in vitro by treating human peripheral blood mononuclear cells with activation agent PHA for 3 days with the addition of AF-EVs or saline control. Immune activation/exhaustion was measured by flow cytometry to determine the expression of PD-1 on CD3+ T-cells. The AF-EV biologic was characterized to contain EVs with positive expression of CD9, CD81, ALIX, and PL-L1. T-cell activation/exhaustion was upregulated in response to PHA and was significantly reduced by 8% in AF-EV treated T-cells compared to saline control (77.7% vs 85.7%, respectively P<0.05). These findings demonstrate that AF-EVs do express PD-L1, a surface marker that has previously been demonstrated to contribute to exosome-mediated immunosuppression. Furthermore, we confirmed in vitro that AF-EVs suppress T-cell activation/ exhaustion in the presence of a T-cell activation agent. COVID-19 long haulers have been described to have upregulated and pro-longed immune activation and T-cell exhaustion, marked by an increase in PD1+ T-cells. Therefore, this finding serves as a starting point for the development of a potential mechanism of action that may describe AF-EV's therapeutic effect in COVID-19 long hauler patients.Copyright © 2023 International Society for Cell & Gene Therapy

Exosomes/EVs: QUANTIFICATION OF CD81+ AND CD133+ EXTRACELLULAR VESICLE POPULATIONS DERIVED FROM AMNIOTIC FLUID

Background & Aim: Amniotic fluid (AF)-derived extracellular vesicles (EVs) are currently being studied within clinical trials as a novel therapeutic drug for acute and chronic diseases such as COVID-19, osteoarthritis, and chronic obstructive pulmonary disease (COPD). Recently, AF has been characterized to contain harvestable EVs that reduce cytokine expression and protect from high oxygen tissue injury. However, the reproducibility of EV populations derived from AF samples has yet to be fully explored. Here within, we present results of a fluorescent nanoparticle tracking analysis that characterizes the reproducibility of CD81+ and CD133+ populations of EVs. Methods, Results & Conclusion: AF was collected from consenting adults during planned, full term cesarean sections and then processed via filtration and ultracentrifugation to precipitate the nanoparticle population. Prior to fluorescent analysis, a MACSPlex exosome kit (Miltenyi Biotec) was used to identify potential exosome surface markers. Nine independent samples of AF-derived nanoparticles were used for Zetaview analysis. Each pellet was resuspended in saline and stained with CD133-AF488 and CD81-DyLight55 antibodies. Fluorescent nanoparticle tracking analysis was completed using the Zetaview Quatt (Particle Metrix). Subsequent videos of stained and total particles were recorded to determine the percentage of positive stained nanoparticles. Exosome surface marker analysis revealed 10 out of the 37 tested surface markers to be present with the most intense surface markers being CD81 and CD133. Furthermore, detection of CD81+ and CD133+ nanoparticles via Zetaview was found in all samples (n=9). The AF- derived nanoparticles were CD81+ and CD133+ at 73.51 ± 18.35 % and 30.41 ± 14.06 % (Mean ± SD), respectively. A high percentage of the nanoparticles were CD81+ with a smaller yet apparent display of CD133+ nanoparticles throughout the samples. Fluorescent characterization of the AF-derived samples demonstrated the reproducibility of both CD81+ and CD133+ nanoparticles. Studying the nature of these nanoparticle populations helps researchers to characterize samples consistently and could lead to understanding their therapeutic potential as a novel biologic.

The Tetraspanin CD81 Is a Host Factor for Chikungunya Virus Replication.

Chikungunya virus (CHIKV) is an arthritogenic reemerging virus replicating in plasma membrane-derived compartments termed "spherules." Here, we identify the human transmembrane protein CD81 as host factor required for CHIKV replication. Ablation of CD81 results in decreased CHIKV permissiveness, while overexpression enhances infection. CD81 is dispensable for virus uptake but critically required for viral genome replication. Likewise, murine CD81 is crucial for CHIKV permissiveness and is expressed in target cells such as dermal fibroblasts, muscle and liver cells. Whereas related alphaviruses, including Ross River virus (RRV), Semliki Forest virus (SFV), Sindbis virus (SINV) and Venezuelan equine encephalitis virus (VEEV), also depend on CD81 for infection, RNA viruses from other families, such as coronaviruses, replicate independently of CD81. Strikingly, the replication-enhancing function of CD81 is linked to cholesterol binding. These results define a mechanism exploited by alphaviruses to hijack the membrane microdomain-modeling protein CD81 for virus replication through interaction with cholesterol. IMPORTANCE In this study, we discover the tetraspanin CD81 as a host factor for the globally emerging chikungunya virus and related alphaviruses. We show that CD81 promotes replication of viral genomes in human and mouse cells, while virus entry into cells is independent of CD81. This provides novel insights into how alphaviruses hijack host proteins to complete their life cycle. Alphaviruses replicate at distinct sites of the plasma membrane, which are enriched in cholesterol. We found that the cholesterol-binding ability of CD81 is important for its function as an alphavirus host factor. This discovery thus broadens our understanding of the alphavirus replication process and the use of host factors to reprogram cells into virus replication factories.

Tetraspanins: Host Factors in Viral Infections.

Tetraspanins are transmembrane glycoproteins that have been shown increasing interest as host factors in infectious diseases. In particular, they were implicated in the pathogenesis of both non-enveloped (human papillomavirus (HPV)) and enveloped (human immunodeficiency virus (HIV), Zika, influenza A virus, (IAV), and coronavirus) viruses through multiple stages of infection, from the initial cell membrane attachment to the syncytium formation and viral particle release. However, the mechanisms by which different tetraspanins mediate their effects vary. This review aimed to compare and contrast the role of tetraspanins in the life cycles of HPV, HIV, Zika, IAV, and coronavirus viruses, which cause the most significant health and economic burdens to society. In doing so, a better understanding of the relative contribution of tetraspanins in virus infection will allow for a more targeted approach in the treatment of these diseases.