Re-programming Immunity Against Glioblastoma via RNA Nanoparticle Vaccines
Despite aggressive surgical resection, cytotoxic chemotherapy, and external beam radiotherapy, most cases of glioblastoma (GBM) remain recalcitrant. These outcomes necessitate novel developmental therapeutics that spare normal tissue. Immunotherapy is a promising novel adjuvant treatment that can harness the cytotoxic capacity of the immune system against tumor-associated antigens with exquisite specificity. To circumvent the challenges associated with the advancement of adoptive cellular immunotherapy, we developed a novel treatment platform, which leverages the use of commercially available and clinically translatable nanoparticles (NPs) that can be combined with tumor derived RNA to peripherally activate T cells against GBM antigens. Although cancer vaccines have suffered from weak immunogenicity, we have advanced a NP vaccine formulation that can reshape a host’s immune profile through combinatorial delivery of RNAs encoding for tumor antigens and RNAs encoding for immunomodulatory molecules to mediate long-lived T cell persistence.
We sought to assess if vaccination with amplified tumor derived RNA encapsulated in lipophilic NPs could be assembled to transfect antigen presenting cells (APCs) in vivo and induce therapeutic anti-tumor immunity in pre-clinical murine tumor models. We hypothesized that RNA encapsulated nanoliposomes would localize to reticuloendothelial organs such as the spleen and liver, transfect APCs therein and induce peripheral antigen specific T cell immunity against GBM. Since activated T cells can cross the blood brain barrier and exert their effector functions against GBM antigens, peripheral transfection of APCs by RNA-NPs represents an attractive vaccination approach for priming endogenous immunity against refractory brain tumors.
We screened several translatable NP formulations for their ability to transfect dendritic cells (DCs) in vitro with GFP mRNA. We demonstrated that the NP DOTAP was the most promising translatable formulation compared to alternative cationic liposomal preparations and linear polyethylenimine NPs with and without DC targeting mannose receptors. RNA-NP vaccines formulated in DOTAP were shown to induce in vivo gene expression and preserve RNA stability over time. We determined that intravenous (IV) injection of RNA-NPs was requisite for inducing functional antigen specific immunity, which was superior to standard peptide vaccines formulated in complete Freund’s adjuvant (CFA). IV administered RNA-NPs localized to splenic and hepatic white blood cells (WBCs); these cells expanded antigen specific T cells when transferred to naïve immunocompetent mice. RNA-NPs induced increased percentages of B7 co-stimulatory molecules, but also elicited compensatory PD-L1 expression. We enhanced the immunogenicity and anti-tumor efficacy of RNA-NP vaccines by combining RNA-NPs with immune checkpoint blockade against PD-L1. We also enhanced the immunogenicity and efficacy of this platform by simply combining mRNAs encoding for immunomodulatory cytokines (i.e. GM-CSF). Finally, we demonstrated that RNA-NP vaccines mediate anti-tumor efficacy against intracranial and subcutaneous melanomas and engender therapeutic anti-tumor efficacy in a cellular immunotherapy model against a radiation/temozolomide resistant invasive murine high-grade glioma.
GBM remains invariably associated with poor patient outcomes thus necessitating development of more targeted therapeutics. Clinically translatable RNA-NPs form stable complexes making them amenable to overnight shipping. They induce potent immune responses when administered systemically and mediate robust anti-tumor efficacy that can be enhanced through co-delivery of immunomodulatory RNAs.
This technology can simultaneously bypass the complexity of cellular therapeutics while cutting down the time to generation of personalized vaccines. Since RNA-NP vaccines can be made within days from a tumor biopsy, providing near immediate immune induction against GBM, these formulations can provide a more feasible and effective therapy with a wide range of applicability for all malignancies that can be targeted using RNA obtained from surgical resection of solid tumors.
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