In vitro-synthesized infectious RNA as an attenuated live vaccine in a flavivirus model

Abstract

Live virus vaccines have in many cases proven to be an extremely effective tool for the prevention of viral diseases^1,2. However, the production of conventional live vaccines in eukaryotic cell cultures has many disadvantages, including the potential for contamination with adventitious agents³ and genetic alterations during propagation, making it necessary to do extensive testing before distribution^4,5. Based on results obtained with a flavivirus⁶ (tick-borne encephalitis virus) in an experimental animal system, we propose a novel live attenuated virus vaccination strategy consisting of the application of in vitro-synthesized infectious RNA instead of the live virus itself. When administered using the GeneGun, less than 1 ng of RNA was required to initiate replication of virus that was attenuated by a specifically engineered deletion⁷ and this induced a protective immunity in laboratory mice. Because this approach uses RNA, it does not have the potential drawbacks of DNA vaccines^8,9,10 and thus combines the advantages of conventional live virus vaccines^1,2 (for example, mimicking natural infection and inducing long-lasting immunity) with those of nucleic acid-based vaccines^2,8,11,12 (for example, ease of production without a requirement for eukaryotic cell culture, stability and purity).