Foot-and-mouth disease virus (FMDV) is a pathogen of great agricultural and economic importance not just in the UK, but worldwide. The UK 2001 outbreak of foot-and-mouth disease resulted in billions of pounds of losses to the agriculture and tourism industries. Genome replication is a key step in the lifecycle of every virus and an understanding of the establishment and maintenance of sites of replication (replication complexes) can therefore lead to novel strategies of disease control. Yet it is clear that there are subtle but important differences between viruses. This project aims to dissect steps in the replication of FMDV at the biochemical level. The viral positive sense RNA genome is replicated via negative sense RNA intermediates. This is an essential step in viral replication, yet many steps in this process are poorly understood. Therefore, how this process might be targeted for therapeutic intervention is not known. We will define both the proteins and RNA elements that are involved in negative strand synthesis, the RNA intermediates formed in the process and how they are used to subsequently generate new positive sense RNA genomes. Our studies employ replicons - mini-genomes that allow the study of replication in a safe virus-free way, as the viral capsid proteins are replaced with reporter genes. Mutations which disable replication can be incorporated into virus to create safer vaccine strains for use in the production of inactivated vaccines in the future. Furthermore, the generation of an immutable virus could be employed as a live attenuated vaccine in outbreak situations.