Experimental Evolution of West Nile Virus at Higher Temperatures Facilitates Broad Adaptation and Increased Genetic Diversity

Abstract

West Nile virus (WNV, Flaviviridae, Flavivirus) is a mosquito-borne flavivirus introduced to North America in 1999. Since 1999, the Earth’s average temperature has increased by 0.6 °C. Mosquitoes are ectothermic organisms, reliant on environmental heat sources. Temperature impacts vector–virus interactions which directly influence arbovirus transmission. RNA viral replication is highly error-prone and increasing temperature could further increase replication rates, mutation frequencies, and evolutionary rates. The impact of temperature on arbovirus evolutionary trajectories and fitness landscapes has yet to be sufficiently studied. To investigate how temperature impacts the rate and extent of WNV evolution in mosquito cells, WNV was experimentally passaged 12 times in Culex tarsalis cells, at 25 °C and 30 °C. Full-genome deep sequencing was used to compare genetic signatures during passage, and replicative fitness was evaluated before and after passage at each temperature. Our results suggest adaptive potential at both temperatures, with unique temperature-dependent and lineage-specific genetic signatures. Further, higher temperature passage was associated with significantly increased replicative fitness at both temperatures and increases in nonsynonymous mutations. Together, these data indicate that if similar selective pressures exist in natural systems, increases in temperature could accelerate emergence of high-fitness strains with greater phenotypic plasticity.

West Nile Virus diffusion in temperate regions and climate change. A systematic review

“…In Europe 315 human cases of WNV infection were observed during the 2020 transmission season, but some countries reporting low numbers of infections had detected higher numbers of human WNV infections (e.g., Austria, Hungary, Serbia, Romania) in previous years, probably due to the herd immunization enhanced by highlevel circulation in earlier periods. It is notable that the high temperature favors the selection of mutant strains that can evade host immune response and support WNV outbreak in previously apparently protected areas [45,46].…”

Patterns of West Nile Virus in the Northeastern United States Using Negative Binomial and Mechanistic Trait‐Based Models

“…This rests on the assumption of no evolution. However, temperature‐dependent evolution of the WNV has been shown in the lab (Fay et al., 2021 ) and in the field (Bialosuknia et al., 2022 ). A further caveat is this research was purely from the standpoint of WNV.…”

Adaptive evolution of West Nile virus facilitated increased transmissibility and prevalence in New York State

“…tarsalis in the US and other Culex species implicated in enhanced WNV transmission in Europe [ 23 , 58 , 59 ]. Additionally, changes to the environment, particularly increases in temperature associated with climate change, may facilitate broad adaptation, perhaps expanding the host and geographical range of the virus [ 60 ]. Importantly, while our previous studies only identified the NY10 genotype in NYS, it is now present throughout the continental US, suggesting that it may have a broad adaptive advantage that could drive similar increases in WNV activity in other regions (nextstrain.org/wnv/na).…”