Big Is Beautiful: Enhanced saRNA Delivery and Immunogenicity by a Higher Molecular Weight, Bioreducible, Cationic Polymer.

Anna K Blakney,Robin J Shattock,Clément R Bouton,Jiaqing Tang,Paul F Mckay,Jonathan Yeow,Christopher L Grigsby,Kai Hu,Karnyart Samnuan,Molly M Stevens,Yunqing Zhu

doi:10.1021/acsnano.0c00326

Anna K Blakney, Robin J Shattock + Show 9 more

Open Access

https://doi.org/10.1021/acsnano.0c00326

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Journal: ACS nano	Publication Date: Apr 8, 2020
Citations: 98	License type: cc-by

Affiliation: Imperial College London, Karolinska Institutet

Abstract

Self-amplifying RNA (saRNA) vaccines are highly advantageous, as they result in enhanced protein expression compared to mRNA (mRNA), thus minimizing the required dose. However, previous delivery strategies were optimized for siRNA or mRNA and do not necessarily deliver saRNA efficiently due to structural differences of these RNAs, thus motivating the development of saRNA delivery platforms. Here, we engineer a bioreducible, linear, cationic polymer called “pABOL” for saRNA delivery and show that increasing its molecular weight enhances delivery both in vitro and in vivo. We demonstrate that pABOL enhances protein expression and cellular uptake via both intramuscular and intradermal injection compared to commercially available polymers in vivo and that intramuscular injection confers complete protection against influenza challenge. Due to the scalability of polymer synthesis and ease of formulation preparation, we anticipate that this polymer is highly clinically translatable as a delivery vehicle for saRNA for both vaccines and therapeutics.

Highlights

Self-amplifying RNA vaccines are highly advantageous, as they result in enhanced protein expression compared to Messenger RNA (mRNA), minimizing the required dose
Bioreducible poly(amido amine)s, such as poly(CBA-co-4-amino-1butanol (ABOL)) (pABOL), have been used as polycations for the intracellular delivery of plasmid DNA (pDNA) and mRNA16 but previously have been synthesized up to a molecular weight of only ∼5−20 kDa. pABOLs are synthesized by aza-Michael polyaddition, which is a wellknown method for making poly(amido amine)s
We show that increasing the molecular weight of a cationic, bioreducible polymer above 5 kDa enhances the delivery efficiency for Self-amplifying RNA (saRNA)

Summary

Introduction

Self-amplifying RNA (saRNA) vaccines are highly advantageous, as they result in enhanced protein expression compared to mRNA (mRNA), minimizing the required dose. Messenger RNA (mRNA) has several advantages as a nucleic acid platform compared to DNA; there is no risk of integration into the host genome, innate sensing can be modulated through base modifications and delivery vehicles, and it is the minimal genetic vector.[3−6] constructs targeting strain diversity or multiple infectious diseases can be combined.[7] Self-amplifying mRNA (saRNA), derived from the alphavirus genome,[8] is advantageous as a vaccine platform, as it self-replicates upon delivery into the cytoplasm, which results in augmented protein expression and a minimum required dose of RNA.[9−11] because saRNA is a relatively large (∼9500 nt), negatively charged molecule, it requires a delivery vehicle for efficient cellular uptake. Previous reports on pAMAMs have largely been limited to relatively low molecular weights of 5 to 20 kDa, which are oligomeric in nature.[16−22] systematic studies on the effect of molecular weight have been rare due to the difficulty in synthesizing high molecular weight pAMAMs

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