UCLA researchers from the Department of Chemistry and Biochemistry have developed a novel virus-like particle (VLP) platform for the encapsulation of mRNA for efficient therapeutic delivery.
BACKGROUND: Messenger RNA (mRNA) technologies have emerged as powerful therapeutics in vaccines and gene therapies. While traditional methods of mRNA therapeutics utilize lipid nanoparticles (LNPs) as the delivery platform, existing systems are limited by several factors, including the encapsulation of uncontrolled numbers of RNA molecules per particle, variable biodistribution and rapid clearance, and undesirable immune responses due to their lipid composition. Additionally, LNPs are not thermally stable and do not provide structural precision or stoichiometric control over RNA packaging, limiting their ability to reproducibly deliver a single defined therapeutic to its target. Other alternative methods of mRNA delivery are limited by significant safety and immunogenicity concerns due to the use of viral vectors. The demand for precise and scalable mRNA delivery platforms has grown across gene therapy and vaccine applications, and there remains an unmet need for a stable, non-infectious, structurally defined, particle system that can encapsulate and deliver a single therapeutic RNA molecule to target tissues.
INNOVATION: UCLA researchers from the Department of Chemistry and Biochemistry have developed an innovative platform for in cellulo synthesis of stoichiometrically precise, monodisperse virus-like particles (VLPs) encapsulating a single copy of self-amplifying mRNA in cellulo. This innovation harnesses the capsid protein (CP) of tobacco mosaic virus (TMV) to form a protective shell around the gene target. The therapeutic construct consists of self-replicating mRNA containing a replicase gene to drive intracellular RNA amplification and engineered with the gene of interest (GOI) linked to a TMV packaging signal to ensure selective encapsidation into capsid particles. When cells are co-transfected with this replicon and a separate TMV CP-encoding mRNA, the self-amplifying therapeutic RNA is efficiently and exclusively encapsidated into VLPs because it is the only RNA molecule being amplified and the only one containing the packaging signal. This produces uniform and non-infectious particles that can be validated by RNA sequencing and subsequently used for therapeutic delivery. To enhance clinical translation, the VLPs can be further modified by PEGylation of the capsid proteins to reduce immunogenicity and functionalized with targeting antibodies. This innovation can revolutionize mRNA therapeutics by generating precisely packaged self-replicating RNA VLPs in mammalian cells for gene therapy and vaccine delivery.
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DEVELOPMENT-TO-DATE: UCLA researchers have designed a HIV-targeting CAR, in vitro reconstituted its mRNA into VLPs, conjugated these VLPs to an anti-CD3 antibody, quantified CAR expression in cytotoxic T cells resulting from their incubation with the VLPs, and demonstrated the killing of HIV-infected helper T cells by these CAR-transformed cytotoxic T cells.
KEYWORDS: virus-like particles; VLP; self-amplifying mRNA; replicase; TMV capsid protein; RNA packaging signal; antibody-targeted delivery; PEGylation; streptavidin–biotin functionalization; gene therapy; cancer immunotherapy; mRNA vaccines; non-infectious delivery system; in cellulo synthesis