Location: Foreign Animal Disease ResearchTitle: Attenuation of foot-and-mouth disease virus by engineered viral polymerase fidelity Author
|Rai, Devendra - University Of Connecticut|
|Diaz-san Segundo, Fayna - University Of Connecticut|
|Campagnola, Grace - Colorado State University|
|Kloc, Anna - Oak Ridge Institute For Science And Education (ORISE)|
|Keith, Anna - Colorado State University|
|De Los Santos, Teresa|
|Peersen, Olve - Colorado State University|
|Rieder, Aida - Elizabeth|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2017
Publication Date: 5/7/2017
Citation: Rai, D.K., Diaz-San Segundo, F., Campagnola, G., Schafer, E.A., Kloc, A., Keith, A., De Los Santos, T.B., Peersen, O., Rieder, A.E. 2017. Attenuation of foot-and-mouth disease virus by engineered viral polymerase fidelity. Journal of Virology. doi: 10.1128/JVI.00081-17.
Interpretive Summary: Foot-and-mouth disease virus (FMDV) is a small RNA virus that causes devastating disease in cattle and other cloven-hoofed animals worldwide. Like other RNA viruses, FMDV is genetically highly variable as a result of an error-prone (i.e. low fidelity) RNA polymerase called 3D, the viral enzyme responsible for making copies of the virus during replication. Previous reports using other RNA virus (polio virus) showed that increasing the fidelity of the polio RNA polymerase resulted in decrease ability of this virus to cause disease. In this study, we identified amino acid residues involved on the 3D enzyme fidelity and upon mutation of these residues we demonstrated increased fidelity of the 3D polymerase and this resulted in a mutant virus with low virulence in animals. This knowledge of the virus-unique replication processes have potential for the development of disease control strategies such as better vaccines.
Technical Abstract: The foot-and-mouth disease virus (FMDV) RNA dependent RNA polymerase (RdRp or 3Dpol) catalyzes viral RNA synthesis. The 3Dpol is a low fidelity enzyme incapable of proofreading which results in a high mutation frequencies that allow the virus to rapidly adapt to different environments. In this study, we used the crystal structure of FMDV 3Dpol to design point mutation in motif A that would alter replication fidelity based on prior results in similar picornaviral polymerases. Using biochemical and genetic characterization, we identified W237F as a high fidelity variant and W237I and W237L as low fidelity variants. These three mutant viruses show similar in vitro growth kinetics and plaque morphologies to the wildtype virus and exhibited ability to survive (fitness) upon coinfection with the wildtype virus. When exposed to the mutagenic nucleoside analog ribavirin, the high fidelity W237F virus was more resistant than wildtype virus while the low fidelity W237I and W237L variants exhibited higher resistance. In a mouse model for FMD, the mutant viruses were significantly attenuated compared to wildtype virus, with the comparable attenuation from both high and low fidelity phenotypes. The data indicate that attenuating FMDV by increasing 3Dpol fidelity could be be exploited to reduce reversion to virulence, which has potential uses for the development of safer vaccine candidates.