Mutation of FMDV Lpro residues outside substrate binding domain drives viral attenuation

Authors: Diaz San Segundo, Fayna; Azzinaro, Paul; Zhu, James; Medina, Gisselle; De Los Santos, Teresa

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2022
Publication Date: 10/31/2022
Citation: Diaz San Segundo, F.C., Azzinaro, P.A., Zhu, J.J., Medina, G.N., De Los Santos, T.B. 2022. Mutation of FMDV Lpro residues outside substrate binding domain drives viral attenuation. Meeting Abstract. https://doi.org/10.3389/fvets.2022.1028077.
DOI: https://doi.org/10.3389/fvets.2022.1028077

Interpretive Summary:

Technical Abstract: The foot-and-mouth disease virus (FMDV) leader proteinase (Lpro) is a papain-like protease that cleaves FMDV polyprotein and several host factors affecting host cell translation and induction of innate immunity. Introduction of Lpro mutations ablating catalytic activity are not tolerated by the virus, however, complete deletion or targeted aminoacid substitutions render viable progeny. In proof-of-concept studies, we have previously identified and characterized FMDV Lpro mutants that are attenuated, while retaining their capacity for inducing a strong adaptive immunity in the natural host. Using molecular modeling, we have identified mutations outside of the substrate binding domain, in a highly conserved aminoacid residue, which rendered viable FMDV variants of reduced virulence in vitro and in vivo. Kinetics studies showed that mutant FMDV Lpro-H138L replicates similarly to wild type (WT) virus in cells with no immune selective pressure, but attenuation is observed in primary porcine epithelial cells. Western blot analysis revealed that while processing of translation factor eIF-4G was only slightly delayed, degradation of innate signaling molecules like G3BP2, IRF7 and NF-'B, among others, were significantly affected and higher levels of interferon (IFN) and IFN-induced gene (ISGs) expression were detected in comparison to WT infection. Consistently with in vitro results, Lpro-H138L showed a significantly attenuated phenotype in vivo in swine while inducing a strong serological immune response. These results suggest that Lpro continues to be the most reliable target to derive viable FMDV strains with potential for development as novel live attenuated FMD vaccine platforms.