Investigating the Impact of Delivery System Design on the Efficacy of Self-Amplifying RNA Vaccines

Abstract

messenger RNA (mRNA)-based vaccines combine the positive attributes of both live-attenuated and subunit vaccines. In order for these to be applied for clinical use, they require to be formulated with delivery systems. However, there are limited in vivo studies which compare different delivery platforms. Therefore, we have compared four different cationic platforms: (1) liposomes, (2) solid lipid nanoparticles (SLNs), (3) polymeric nanoparticles (NPs) and (4) emulsions, to deliver a self-amplifying mRNA (SAM) vaccine. All formulations contained either the non-ionizable cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or dimethyldioctadecylammonium bromide (DDA) and they were characterized in terms of physico-chemical attributes, in vitro transfection efficiency and in vivo vaccine potency. Our results showed that SAM encapsulating DOTAP polymeric nanoparticles, DOTAP liposomes and DDA liposomes induced the highest antigen expression in vitro and, from these, DOTAP polymeric nanoparticles were the most potent in triggering humoral and cellular immunity among candidates in vivo.

mRNA vaccine for cancer immunotherapy

“…To further improve transgene expression and immunity of SAM vaccines, several approaches have been attempted: Manara has reported the co-administration of GM-CSF expressing RNA with SAM to improve the potency against a lethal influenza virus challenge in mice [ 71 ]. Moreover, Lou et al and Anderluzzi et al both evaluated different cationic lipid formulations including liposomes, LNPs, polymeric nanoparticles and emulsions to encapsulate rabies virus glycoprotein G (SAM-RVG), and noticed that DOTAP containing polymeric nanoparticles and LNPs were the most potent in triggering humoral and cellular immunity [ 72 , 73 ]. Lastly, SAM has been truncated into two transcripts (smaller in size) to address the concerns of inefficient delivery [ 74 ].…”

Self-amplifying RNA vaccines for infectious diseases

“…With so many different nonviral formulations available, Anderluzzi et al sought to compare liposomes, solid LNPs, polymeric nanoparticles, and emulsions for the delivery of an saRNA vaccine-encoding the rabies virus glycoprotein [ 59 ]. In their hands, low-dose saRNA nanoparticles complexed with the non-ionizable cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) initially resulted in similar antibody titres to Rabipur (RabAvert), a commercially licensed rabies vaccine.…”

“…In their hands, low-dose saRNA nanoparticles complexed with the non-ionizable cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) initially resulted in similar antibody titres to Rabipur (RabAvert), a commercially licensed rabies vaccine. However, the proprietary cationic nanoemulsion (CNE) 56 from GlaxoSmithKline (GSK, Rockville, MD, USA) outperformed all DDA and DOTAP formulations [ 59 ]. Comparing delivery approaches in side-by-side studies such as this would assist in determining the usefulness of each formulation.…”

“…The saRNA-derived rabies RNA was detected up to 2 months after a single injection, emphasizing the durability of the approach. A second study evaluated immunogenicity in mice using the licensed inactivated rabies virus vaccine Rabipur (RabAvert) as a benchmark for immunization [ 59 ]. Positive protective antibody responses similar to Rabipur were observed following a single IM injection of DOTAP nanoparticle-encapsulated or CNE56-absorbed saRNAs (0.5 and 1.5 µg).…”

“…Positive protective antibody responses similar to Rabipur were observed following a single IM injection of DOTAP nanoparticle-encapsulated or CNE56-absorbed saRNAs (0.5 and 1.5 µg). A second injection boosted antigen-specific IgG titres in all encapsulation formulations (DOTAP nanoparticles, DOTAP liposomes, and DDA liposomes) but only high-dose CNEs elicited responses comparable to the licensed vaccine [ 59 ]. The first clinical trial of GSKs CNE formulated RG-SAM vaccine (NCT04062669) will establish the safety of a 3-dose IM regimen and determine the immunogenicity of saRNAs in humans.…”