Dynamics of arthropod-borne virus evolution during transmission

Seminar Speaker: Nathan D. Grubaugh, PhD

Postdoctoral Fellow
Department of Immunology and Microbial Science
The Scripps Research Institute

Abstract:  Arthropod-borne viruses (arboviruses), such as Zika, chikungunya, and West Nile virus (WNV), pose as continuous threats to emerge and cause large epidemics. Often these events are associated with novel virus variants optimized for local transmission, which first arise as minorities within a host. Thus the conditions that regulate the frequency of intrahost variants are important determinants of emergence. For arboviruses, these conditions are complex as they cycle between the different environments of their arthropod vectors and vertebrate hosts. First, I will describe the forces that alter WNV genetic diversity during transmission. Next, we will explore the fitness costs and benefits of replicating different enzootic mosquito vectors and avian hosts. The general theme is that in mosquitoes, the WNV genetic repertoire dramatically changes due to repeated bottles and to escape the innate immune response, RNA interference. The consequence, however, is that the diversity generated in mosquitoes decreases its fitness in birds, and thus most WNV variants are rapidly purged upon transmission. Lastly, I will compare these results to a tick-borne virus (Powassan virus) to demonstrate how vector ecology can be a determinate of evolution. The results presented here highlight the complex evolutionary forces that a novel arbovirus variant must overcome to alter infection phenotypes at the population level.

Streaming video: the seminar will be broadcast live once the event has started. The video recording may also be viewed at a later date. [video link]

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