Lighting the way to personalized mRNA immune cell therapies

mRNA nanodelivery systems: targeting strategies and administration routes

With the great success of coronavirus disease (COVID-19) messenger ribonucleic acid (mRNA) vaccines, mRNA therapeutics have gained significant momentum for the prevention and treatment of various refractory diseases. To function efficiently in vivo and overcome clinical limitations, mRNA demands safe and stable vectors and a reasonable administration route, bypassing multiple biological barriers and achieving organ-specific targeted delivery of mRNA. Nanoparticle (NP)-based delivery systems representing leading vector approaches ensure the successful intracellular delivery of mRNA to the target organ. In this review, chemical modifications of mRNA and various types of advanced mRNA NPs, including lipid NPs and polymers are summarized. The importance of passive targeting, especially endogenous targeting, and active targeting in mRNA nano-delivery is emphasized, and different cellular endocytic mechanisms are discussed. Most importantly, based on the above content and the physiological structure characteristics of various organs in vivo, the design strategies of mRNA NPs targeting different organs and cells are classified and discussed. Furthermore, the influence of administration routes on targeting design is highlighted. Finally, an outlook on the remaining challenges and future development toward mRNA targeted therapies and precision medicine is provided.

Hydroxycholesterol substitution in ionizable lipid nanoparticles for mRNA delivery to T cells

Delivery of nucleic acids, such as mRNA, to immune cells has become a major focus in the past decade with ionizable lipid nanoparticles (LNPs) emerging as a clinically-validated delivery platform. LNPs-typically composed of ionizable lipids, cholesterol, phospholipids, and polyethylene glycol lipids -have been designed and optimized for a variety of applications including cancer therapies, vaccines, and gene editing. However, LNPs have only recently been investigated for delivery to T cells, which has various therapeutic applications including the engineering of T cell immunotherapies. While several LNP formulations have been evaluated for mRNA delivery, recent work has demonstrated that the utilization of cholesterol analogs may enhance mRNA delivery. Other studies have shown that cholesterols modified with hydroxyl groups can alter endocytic recycling mechanisms. Here, we engineered a library of LNPs incorporating hydroxycholesterols to evaluate their impact on mRNA delivery to T cells by leveraging endosomal trafficking mechanisms. Substitution of 25% and 50% 7α-hydroxycholesterol for cholesterol in LNPs enhanced mRNA delivery to primary human T cells ex vivo by 1.8-fold and 2.0-fold, respectively. Investigation of endosomal trafficking revealed that these modifications also increase late endosome production and reduce the presence of recycling endosomes. These results suggest that hydroxyl modification of cholesterol molecules incorporated into LNP formulations provides a mechanism for improving delivery of nucleic acid cargo to T cells for a range of immunotherapy applications.