Meeting Abstract
7.2 Tuesday, Jan. 4 The Influence of Host Genetic Diversity on Patterns of Pathogen Adaptation and Virulence Evolution KUBINAK, J.L.; University of Utah jason.kubinak@utah.edu
Host-pathogen co-evolutionary arms races are thought to be one of the most potent selective forces influencing the nature of genetic diversity for both host and pathogen. In this co-evolutionary model, the fitness benefit accrued through adaptation by one species increases the intensity of selection on the other which in turn leads to counter-adaptive responses. While this hypothesis has been classically used to explain the evolution and maintenance of high levels of genetic diversity at immunologically important loci in host populations, it can also be applied as a model of pathogen adaptation and virulence (disease severity) evolution. Three fundamental predictions regarding patterns of pathogen adaptation and virulence evolution that emerge from this model are that host exploitation (i.e. pathogen fitness) will be positively correlated with virulence, pathogen adaptation will be host genotype-specific, and reduced host genetic diversity will facilitate pathogen adaptation leading to an increase in the severity of infectious disease. Using serial passage, a proven approach for inducing pathogen evolution in experimental time, we now provide the first direct empirical support for the above predictions using a vertebrate model. Our data demonstrates that serial passage of a virus through genetically identical hosts produces a pathogen population with enhanced ability to exploit its host resulting in an extreme increase in the severity of disease. Moreover, we show that virus stocks become most fit and virulent on their host-of-passage indicating genotype-specific patterns of pathogen adaptation. Finally, we show that increased host genetic diversity is an impediment to pathogen adaptation. An important implication from our work is that low genetic diversity makes host populations more susceptible to exploitation by their rapidly evolving pathogens, which for endangered species increases the likelihood of extinction.
