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Updated: Aug 18, 2026
In Vitro ELISA Test to Evaluate Rabies Vaccine Potency
Published on: May 11, 2020
Characterization of P gene-deficient rabies virus: propagation, pathogenicity and antigenicity
Kinjiro Morimoto1, Youko Shoji, Satoshi Inoue
1Department of Virology I, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, Japan. kmorimot@nih.go.jp
Abstract:
The RNA polymerase of rabies virus (RV) is a two-protein complex composed of L (a large catalytic component) and P (a non-catalytic phosphoprotein cofactor) proteins. We generated a gene-deficient RV lacking the entire P gene from HEP-Flury (HEP) strain, one of the most attenuated RV strains, by the method of reverse genetics. This P gene-deficient (def-P) virus could replicate and produce progeny viruses with a slightly retarded rate in the cell lines that constitutively express the P protein. The def-P virus could perform the primary RNA transcription by the virion-associated polymerase even in the infected host without de novo P protein synthesis. However, the def-P virus required the newly synthesized P protein for the secondary RNA transcription and genome RNA replication of virus. No progeny virus was produced in the infected host that did not express P protein. The def-P virus was apathogenic in adult and suckling mice even when inoculated intracranially. On the other hand, inoculation of the def-P virus into mice induced a high titer of virus-neutralizing antibody and protected mice from lethal challenge with the CVS strain. These results demonstrated that the def-P virus could induce strong protective immunity against rabies virus without the production of progeny virus and the severe host damage. The def-P virus would be a potential resource of safe live-attenuated rabies vaccine.
Insights
A novel rabies virus (RV) lacking the P protein gene (def-P virus) replicates without causing disease. This safe def-P virus induces protective immunity, showing potential as a live-attenuated rabies vaccine.
Area of Science:
- Virology
- Immunology
- Vaccinology
Background:
- Rabies virus (RV) RNA polymerase is a complex of L and P proteins.
- The P protein is essential for viral transcription and replication.
- Attenuated RV strains are valuable for vaccine development.
Purpose of the Study:
- To generate and characterize a P gene-deficient RV (def-P virus).
- To assess the replication, pathogenicity, and immunogenicity of the def-P virus.
- To evaluate the potential of the def-P virus as a live-attenuated rabies vaccine.
Main Methods:
- Reverse genetics was used to create a P gene-deficient RV from the HEP-Flury strain.
- Replication kinetics were studied in cell lines expressing the P protein.
- Pathogenicity was assessed in adult and suckling mice via intracranial inoculation.
- Humoral immune response and protective efficacy against lethal CVS strain challenge were evaluated.
Main Results:
- The def-P virus replicated in cell lines expressing P protein but required de novo P synthesis for secondary transcription and replication.
- The def-P virus was apathogenic in mice, even after intracranial inoculation.
- Inoculation with def-P virus induced high titers of neutralizing antibodies.
- Mice inoculated with def-P virus were protected from lethal challenge with the virulent CVS strain.
Conclusions:
- The P gene-deficient RV (def-P virus) is replication-competent but apathogenic, inducing protective immunity.
- The def-P virus represents a promising candidate for a safe and effective live-attenuated rabies vaccine.
- This study highlights the critical role of the P protein in RV pathogenesis and viral replication.
