A localizing nanocarrier formulation enables multi-target immune responses to multivalent replicating RNA with limited systemic inflammation

RNA vaccines possess significant clinical promise in counteracting human diseases caused by infectious or cancerous threats. Self-amplifying replicon RNA (repRNA) has been thought to offer the potential for enhanced potency and dose sparing. However, repRNA is a potent trigger of innate immune responses in vivo, which can cause reduced transgene expression and dose-limiting reactogenicity, as highlighted by recent clinical trials. Here, we report that multivalent repRNA vaccination, necessitating higher doses of total RNA, could be safely achieved in mice by delivering multiple repRNAs with a localizing cationic nanocarrier formulation (LION). Intramuscular delivery of multivalent repRNA by LION resulted in localized biodistribution accompanied by significantly upregulated local innate immune responses and the induction of antigen-specific adaptive immune responses in the absence of systemic inflammatory responses. In contrast, repRNA delivered by lipid nanoparticles (LNPs) showed generalized biodistribution, a systemic inflammatory state, an increased body weight loss, and failed to induce neutralizing antibody responses in a multivalent composition. These findings suggest that in vivo delivery of repRNA by LION is a platform technology for safe and effective multivalent vaccination through mechanisms distinct from LNP-formulated repRNA vaccines.

Evaluation of repRNA vaccine for induction and in utero transfer of maternal antibodies in a pregnant rabbit model

Mother-to-child transmission is a major route for infections in newborns. Vaccination in mothers to leverage the maternal immune system is a promising approach to vertically transfer protective immunity. During infectious disease outbreaks, such as the 2016 Zika virus (ZIKV) outbreak, rapid availability of vaccines can prove critical in reducing widespread disease burden. The recent successes of mRNA vaccines support their evaluation in pregnant animal models to justify their use in neonatal settings. Here we evaluated immunogenicity of self-amplifying replicon (repRNA) vaccines, delivered with our clinical-stage LION nanoparticle formulation, in pregnant rabbits using ZIKV and HIV-1 as model disease targets. We showed that LION/repRNA vaccines induced robust antigen-specific antibody responses in adult pregnant rabbits that passively transferred to newborn kits in utero. Using a matrixed study design, we further elucidate the effect of vaccination in kits on the presence of pre-existing maternal antibodies. Our findings showed that timing of maternal vaccination is critical in maximizing in utero antibody transfer, and subsequent vaccination in newborns maintained elevated antibody levels compared with no vaccination. Overall, our results support further development of the LION/repRNA vaccine platform for maternal and neonatal settings.