Evolution and adaptation of dengue virus in response to high-temperature passaging in mosquito cells

The incidence of arboviral diseases like dengue, chikungunya, and yellow fever continues to rise in association with the expanding geographic ranges of their vectors, Aedes aegypti and Aedes albopictus. The distribution of these vectors is believed to be driven in part by climate change and increasing urbanization. Arboviruses navigate a wide range of temperatures as they transition from ectothermic vectors (from 15°C to 35°C) to humans (37°C) and back again, but the role that temperature plays in driving the evolution of arboviruses remains largely unknown. Here, we passaged replicate dengue serotype-2 virus populations 10 times at either 26°C (Low) or 37°C (High) in C6/36 Aedes albopictus cells to explore the differences in adaptation to these thermal environments. We then deep-sequenced the resulting passaged dengue virus populations and tested their replicative fitness in an all-cross temperature regime. We also assessed the ability of the passaged viruses to replicate in the insect vector. While viruses from both thermal regimes accumulated substitutions, only those reared in the 37°C treatments exhibited nonsynonymous changes, including several in the E, or envelope protein, and multiple non-structural genes. Passaging at the higher temperature also led to reduced replicative ability at 26°C in both cells and mosquitoes. One of the mutations in the E gene involved the loss of a glycosylation site previously shown to reduce infectivity in the vector. These findings suggest that viruses selected for growth at higher ambient temperatures may experience tradeoffs between thermostability and replication in the vector. Such associations might also have implications for the suitability of virus transmission under a changing climate.