A Trans-amplifying RNA Vaccine Strategy for Induction of Potent Protective Immunity

Abstract

Here, we present a potent RNA vaccine approach based on a novel bipartite vector system using trans-amplifying RNA (taRNA). The vector cassette encoding the vaccine antigen originates from an alphaviral self-amplifying RNA (saRNA), from which the replicase was deleted to form a transreplicon. Replicase activity is provided in trans by a second molecule, either by a standard saRNA or an optimized non-replicating mRNA (nrRNA). The latter delivered 10-to 100-fold higher transreplicon expression than the former. Moreover, expression driven by the nrRNA-encoded replicase in the taRNA system was as efficient as in a conventional monopartite saRNA system. We show that the superiority of nrRNAover saRNA-encoded replicase to drive expression of the transreplicon is most likely attributable to its higher translational efficiency and lack of interference with cellular translation. Testing the novel taRNA system in mice, we observed that doses of influenza hemagglutinin antigen-encoding RNA as low as 50 ng were sufficient to induce neutralizing antibodies and mount a protective immune response against live virus challenge. These findings, together with a favorable safety profile, a simpler production process, and the universal applicability associated with this bipartite vector system, warrant further exploration of taRNA.

The Potential of Self-amplifying RNA Vaccines for Infectious Diseases and COVID-19

“…Minimizing IFN responses could be a useful strategy to increase vaccine potency. This could be achieved by co-administration of compounds able to block IFN responses, like for example vaccinia virus immune evasion proteins [80]. A different approach to boost saRNA vaccines has been based on in vitro evolution of RNA replicons in IFN-competent cells [119].…”

“…In another vaccine study on influenza viru the flavivirus classical swine fever virus (CSFV) RNA expressing influenza virus encapsulated in liposome nanoparticles elicited immune responses both in vitro and in vivo {79]. Additionally, a novel bipartite vector system applying trans-amplifying RNA (taRNA) has been engineered based on the SFV saRNA vector by deletion of replicon [80]. The replicase function is provided by a standard saRNA or an optimized non-replicating mRNA (nrRNA).…”

Self-amplifying RNA vaccines for infectious diseases

“…Here the saRNA is split into two transcripts, the first encoding the nsP1-4 replicon complex and the second encoding the gene of interest as a "transreplicon" (Fig. 1) [60][61][62]. This approach was recently adopted by Beissert et al [62] who generated an influenza vaccine transreplicon based on a SFV saRNA design.…”

“…1) [60][61][62]. This approach was recently adopted by Beissert et al [62] who generated an influenza vaccine transreplicon based on a SFV saRNA design. The transamplifying strategy worked best when the replicon was delivered as a sequence-modified mRNA transcript and not as an saRNA.…”

A new generation of vaccines based on alphavirus self-amplifying RNA

“… Plurifunctional CD4+ and CD8+ T cells [ 12 ] ta-SFV Nak. RNA ID HA Protection from influenza virus challenge [ 41 •• ] VEEV EP & LNP Luc Expression: EP, days 3−10; LNP, peak 24h [ 16 ] EP Pig High expression for 12 days [ 17 • ] Mouse Optimal expression in tail base versus flank [ 19 • ] EP+RNase inh. RNase inh.…”