Circular mRNA against CleanCap linear mRNA vectors: comprehensive comparison, expression, active and passive immunization

ABSTRACT The mRNA platform has revolutionised vaccine technology by providing a universal, fast and easily scalable production process. There are two main types of mRNA – linear (cap-dependent) and circular (cap-independent), each with its own advantages. Although both vector types are continuously being improved, there has been no comprehensive comparative analysis of the most efficient existing vectors of each type. This paper provides a comparison of expression efficiency, protective and therapeutic activities of circular and linear mRNA vectors. We examined different combinations of linear vectors: containing either N1-methylpseudouridines or uridine and capped with either ARCA (m 7 G(5′)ppp(5′)G) or CleanCap (m 7 G(5′)ppp(5′)m 2 G). Circular vectors contained both commonly used IRES of coxsackievirus B3 and new a IRES of human rhinoviruses B6. Preliminary luciferase assay showed that modified linear vectors exhibited significantly higher expression levels both in vitro and in vivo . A similar but less dramatic difference was observed in expression of the target protein. At the same time, immunogenicity and protective activity of linear and circular vectors were equal.