ウイルス学：遺伝的に安定した新規ポリオワクチン候補でポリオ根絶を試みる

Two new polio vaccine candidates that induce immune responses in mice and may increase the possibility of eradicating polio are presented in Nature this week. The candidates, based on a weakened version of the poliovirus, are less likely to result in vaccine-derived virulent poliovirus variants than some previous vaccines.

Polio is caused by three different versions (or serotypes) of the poliovirus. Wild poliovirus (WPV) types 2 and 3 have been eradicated in the past decade, owing to the development of vaccines that either use an inactivated version of the virus or attenuated polioviruses (versions that are sufficiently weakened so as not to cause disease but still provoke an immune response). However, WPV type 1 still causes disease in Afghanistan and Pakistan, and two other types of poliovirus that arise from the evolution of the virus in the vaccine to a virulent form continue to circulate.

The recently developed novel oral type 2 polio vaccine (nOPV2) that uses a live attenuated virus has been shown to be effective at inducing an immune response, while remaining genetically stable, and has been used against vaccine-derived poliovirus variants. This stability is thanks to the inclusion of specific genetic components that constrain the virus from regaining virulence. Building on this approach, Raul Andino, Andrew Macadam and colleagues develop vaccines for WPV types 1 and 3 (nOPV1 and nOPV3, respectively). Animal experiments and deep sequencing confirm that the vaccine candidates remain attenuated even if small mutations occur after vaccination. They also report that nOPV1 and nOPV3 proved to be very safe in mice. Joint administration of nOPV1, nOPV2 and nOPV3 in mice resulted in the production of antibodies against all three types of poliovirus and the mice were protected against disease.