The drivers of viral evolution
Viruses affect humans, animals and plants alike, thereby constituting one of the most important groups of parasites capable of causing disease. The inherent ability of viruses to adapt to new hosts and/or environments is partly responsible for the existence of so many viral species. However, the precise mechanisms underlying such speciation events are not clear. To shed light on virus evolution, the EU-funded 'Analysis of speciation mechanisms in RNA viruses' (RNAVIRSPE) project analysed the contribution of various ecological factors. These were coupled with assessment of mutation rates, and gene expression profiles in three animal viruses and three plant virus groups. The rationale was that such analyses, apart from being scientifically informative, would provide insight into the emergence of important pathogens. Using state-of-the-art bioinformatics tools, scientists analysed large datasets of genomic sequences and generated phylogenetic reconstructions. Results indicated some viruses had congruent phylogenies with their hosts, but all the analysed viruses evolved at higher rates than their host. This suggests that adaptation to the host rather than host-virus co-divergence influences virus evolution. Interestingly, host migration was suggested as another driver of virus speciation. With the HIV epidemic in the Caribbean as an example, researchers could associate the genetic structure of a virus population with the country of origin. Human intervention and landscape heterogeneity also affect virus diversification, probably driven by the need to adapt to the new environment. Apart from ecological factors, it became evident that certain genetic factors could also mediate evolution of viruses. RNA viruses with overlapping genes exhibited reduced ability to generate new variants and form new species. The targeting of slow-evolving genes could, therefore, be utilised to increase the durability of vaccine-mediated protection. The information generated during RNAVIRSPE could be adapted to prevent the development of drug-resistant viral strains. Furthermore, to design efficient control strategies for viral diseases, the main viral host and its migration routes should be considered alongside the availability of alternative hosts.
Keywords
Virus speciation, evolution, genetic factors, ecological factors, viral disease, disease management
