Self-replicative RNA vaccines elicit protection against influenza A virus,respiratory syncytial virus, and a tickborne encephalitis virus

In genetic vaccination, recipients are immunized with antigen-encoding nucl eic acid, usually DNA. This study addressed the possibility of using the re combinant alpha virus RNA molecule, which replicates in the cytoplasm of tr ansfected cells, as a novel approach for genetic vaccination. Mice were imm unized with recombinant Semliki Forest virus RNA-encoding envelope proteins from one of 3 viruses: influenza A virus, a tickborne flavivirus (louping ill virus), or respiratory syncytial virus (RSV). Serologic analyses showed that antigen-specific antibody responses were elicited. IgG isotyping indi cated that predominantly Th1 type immune responses were induced after immun ization with RSV F protein-encoding RNA, which is relevant for protection a gainst RSV infection. Challenge infection showed that RNA immunization had elicited significant levels of protection against the 3 model virus disease s.