Investigating the foot-and-mouth disease virus 3A protein

Abstract

Foot-and-Mouth Disease Virus (FMDV) is a globally important pathogen responsible for causing Foot-and-Mouth Disease (FMD) in wildlife and domestic livestock species and has significant economic impacts. FMD is difficult to control due to its highly infectious nature, wide diversity of host species and the existence of multiple serotypes; therefore, understanding the processes of FMDV infection and viral RNA replication are key to the development of improved diagnostics and vaccines. This thesis investigates the potential roles of the FMDV 3A non-structural protein using a combination of sub-genomic replicons, recombinant viruses and proteomics techniques. The picornavirus 3A protein has previously been linked with roles in replication complex formation, virulence and determining viral host range. This thesis presents findings showing that a naturally occurring deletion in 3A had differing effects on replication in cells lines derived from different natural hosts thereby supporting the conclusion that 3A has an important role in viral host range. Proteomic (immunoprecipitation and mass spectroscopy) investigations were carried out to identify potential cellular interaction partners of FMDV 3A, and the impact on infection and replication of reducing expression of two selected cellular proteins Rab7L1 and TBC1D20 was investigated. The 3A protein of FMDV was shown to include a conserved FFAT motif (which bind the ER resident protein VAP) in its N terminal domain. A role for this motif was also investigated with the results suggesting that the 3A FFAT motif is important for efficient viral replication. Finally, the potential role of 3A to act as the donor of 3B during replication was investigated. Key findings from experiments using FMDV replicons and recombinant viruses showed that full-length P3 and the processing intermediate 3ABBB are not required for viral RNA replication suggesting that the preferred donor of 3B for uridylation is likely a 3BC containing precursor protein.