Genetic Determinants of Altered Virulence of Type O Foot-and-Mouth Disease Virus

Abstract

Under different circumstances, the alteration of several viral genes may give an evolutionary advantage to the virus to maintain its prevalence in nature. In this study, a 70-nucleotide deletion in the small fragment (S fragment) of the viral 5′-untranslated region (5′-UTR) together with one amino acid insertion in the leader protein (Lpro) that naturally occurred in several serotype O foot-and-mouth disease virus (FMDV) strains in China was identified. The properties of two field serotype O FMDV strains, with or without the 70-nucleotide deletion in the S fragment and the amino acid insertion in Lpro, were compared in vitro and in vivo. Clinical manifestations of FMD were clearly observed in cattle and pigs infected by the virus without the mutations. However, the virus with the mentioned mutations caused FMD outcomes only in pigs, not in cattle. To determine the role of the 70-nucleotide deletion in the S fragment and the single amino acid insertion in Lpro in the pathogenicity and host range of FMDV, four recombinant viruses, with complete genomes and a 70-nucleotide deletion in the S fragment, a single amino acid insertion in Lpro, or both mutations, were constructed and rescued. It showed that deletion of 70 nucleotides in the S fragment or insertion of one amino acid (leucine) at position 10 of Lpro partly decreased the viral pathogenicity of Mya-98 lineage virus in cattle and pigs. However, the virus with dual mutations caused clinical disease only in pigs, not in cattle. This suggested that the S fragment and Lpro are significantly associated with the virulence and host specificity of FMDV. The naturally occurring dual mutation in the S fragment and Lpro is a novel determinant of viral pathogenicity and host range for serotype O FMDV. IMPORTANCE FMD is probably the most important livestock disease in the world due to the severe economic consequences caused. The alteration of several viral genes may give the virus selective advantage to maintain its prevalence in nature. Here, we identified that a 70-nucleotide deletion in the S fragment combined with a single leucine insertion in the leader protein (Lpro) is a novel determinant of restricted growth on bovine cells, which significantly contributes to the altered virulence of serotype O FMDV in cattle. A synergistic and additive effect of the 70-nucleotide deletion in the S fragment and the single leucine insertion in Lpro on the virulence and host specificity of the virus was determined. These results will benefit efforts to understand the vial pathogenicity mechanism and molecular characteristics of FMDV.

The RNA pseudoknots in foot-and-mouth disease virus are dispensable for genome replication, but essential for the production of infectious virus

“…The cre region is involved in templating uridylation of the RNA primer peptide, VPg (also known as 3B), and the IRES determines the initiation of translation of the viral polyprotein [ 17 , 18 ]. The roles of the S-fragment, the poly-C tract and the PKs in viral replication have not been fully elucidated, however, recent studies have shown that truncations to the S-fragment can affect the ability to control aspects of innate immune response to viral infection [ 19 – 21 ]. It has also recently been reported that viruses with a deletion within the PK region exhibited an attenuated phenotype in bovine but not in porcine cells, suggesting a role for the PKs in determining viral tropism [ 22 ].…”

An anti-picornaviral strategy based on the crystal structure of foot-and-mouth disease virus 2C protein

“…STAR+METHODS generated using site-directed mutagenesis. The full-length infectious clone containing the FMDV O/BY/CHA/2010 sequence was generated based on the reverse-genetics system (Yang et al, 2020). All constructed plasmids were analyzed and verified by DNA sequencing.…”

Foot-and-Mouth Disease Virus 3B Protein Interacts with Pattern Recognition Receptor RIG-I to Block RIG-I–Mediated Immune Signaling and Inhibit Host Antiviral Response

“…The construction strategy for the r3B-FMDV and r3B-A/E-FMDV infectious clones was based on the reverse-genetics system that has been developed by our laboratory previously (35). A synonymous substitution led to no changes in amino acids in the 2C was introduced into the viral genome of O/BY/CHA/2010 (mutation of the 691-696 region in 2C from 59-ATTGAC-39→59-ATCGAT-39) to generate a unique ClaI restriction enzyme site.…”

“…All of the constructed plasmids were sequenced. The viral rescue and identification was then performed as described previously (35).…”