COS 44-8
Experimental evolution of viral strains in response to coinfection
Infection of a single host by multiple, interacting pathogens has been hypothesized to be an important driver of pathogen evolution. Competition or facilitation between pathogens can change which genotypes in a population are the fittest, potentially leading to changes in pathogen aggressiveness and disease severity. The prevailing hypothesis is that coinfection should always lead to greater virulence when pathogens compete at the within-host level, since benefits of increased host utilization are accrued individually while costs of coincident host damage are shared by all. The majority of studies on this topic are based on mathematical modeling, and there is a dearth of empirical data that address the effects of coinfection on pathogen evolution in live hosts. In order to gain a better understanding of how coinfection influences pathogen evolution, strains of barley yellow dwarf and cereal yellow dwarf viruses (BYDV and CYDV) that had been maintained in single infections for years were transmitted singly or together for several host generations.
Results/Conclusions
Depending on the virus, we observed a range of changes in within-host concentration, from decreased concentration in coinfections to an increase in concentration in both single infections and coinfections when strains had a history of coinfection in comparison to strains with a history of single infections. There were also significant differences between independently evolved strains in response to a history of coinfections. Preliminary data show no significant changes in virulence associated with these changes in viral accumulation. However, there is some indication that virus transmissibility can change in response to sequential coinfections. These data demonstrate that viral evolution in response to coinfection is much more complex than previously assumed.