Technologies

The mRNA vaccines and their deployment during the COVID-19 pandemic have provided remarkable proof of their capabilities and feasibilities for human protection. However, mRNA vaccines still have certain limitations due to their inherent instability, susceptibility to degradation, immunogenicity without nucleoside modification, and short duration of expression for in vivo administration. In comparison to linear mRNA, circular RNAs (circRNAs) are single-stranded, covalently closed coding RNA with higher stability and resistant to exonuclease degradation. Moreover, circRNAs can be rapidly produced via in vitro transcription without nucleotide modification. As a proof of concept, Abnova has developed a SARS-CoV-2 vaccine using circRNA vaccine technologies. The main structure of the circRNAs includes internal ribosome entry site (IRES) and an open reading frame (ORF) for cap-independent translation of spike (S) protein for extended expression.