Adaptive genetic diversifications among tick-borne encephalitis virus subtypes: A genome-wide perspective.

Tick-borne encephalitis (TBE) is a severe neurological illness in humans. Tick-borne encephalitis virus (TBEV), the causative agent, can be grouped into Far Eastern, Siberian, and (Western) European subtypes. These subtypes are characterized by diverse vector specificity, host range and clinical manifestations. To provide hints for the decisive genetic factors underlying their epidemic and pathogenic diversities, we performed a genome-wide evolutionary study to evaluate the genetic diversity accompanied with the segregations of TBEV subtypes. The results show that adaptive selection has driven the diversification among these subtypes. Furthermore, the adaptive divergence-related changes have taken place on the proteins C, NS1, and/or NS2A. These results highlight candidate genes for the epidemic and pathogenic diversities, and will be useful in understanding the epidemic and pathogenic features of TBE.