Current potency tests for inactivated poliovirus vaccine (IPV) measure either antigen (Ag) content in vitro or serum neutralizing antibody (NAb) responses in animals. The recent establishment of transgenic (Tg) mouse strains carrying the gene for the human poliovirus receptor (PVR) allowed investigation of the correlation of potency tests with protection of animals against disease caused by poliovirus. Studies conducted at LMD showed that IPV could protect Tg PVR mice against lethal challenge with a type-3 wild poliovirus strain. NAb level correlated with protection, different vaccination regimens differed in protective effect, and poliovirus C Ag did not induce protection. Administration of immune mouse serum protected mice against type-3 challenge. Trivalent IPV was less protective than monovalent IPV administered at the same doses. These findings have been accepted for publication in the Journal of Infectious Diseases (Taffs et al., Inactivated poliovirus vaccine protects Tg PVR mice against type 3 poliovirus challenge). The relationship of vaccine dose to protective response and NAb levels was also determined for type-1 poliovirus. Experiments to complete the model with type-2 challenges are in progress. The Tg PVR mouse protection test may provide important information relevant to the adoption of new immunization protocols for combined vaccines containing IPV and the efficacy of vaccination schedules involving sequential administration of IPV and OPV.
