Activation of Early Proinflammatory Responses by TBEV NS1 Varies between the Strains of Various Subtypes

Tick-borne encephalitis (TBE) is an emerging zoonosis that may cause long-term neurological sequelae or even death. Thus, there is a growing interest in understanding the factors of TBE pathogenesis. Viral genetic determinants may greatly affect the severity and consequences of TBE. In this study, nonstructural protein 1 (NS1) of the tick-borne encephalitis virus (TBEV) was tested as such a determinant. NS1s of three strains with similar neuroinvasiveness belonging to the European, Siberian and Far-Eastern subtypes of TBEV were studied. Transfection of mouse cells with plasmids encoding NS1 of the three TBEV subtypes led to different levels of NS1 protein accumulation in and secretion from the cells. NS1s of TBEV were able to trigger cytokine production either in isolated mouse splenocytes or in mice after delivery of NS1 encoding plasmids. The profile and dynamics of TNF-alpha, IL-6, IL-10 and IFN-gamma differed between the strains. These results demonstrated the involvement of TBEV NS1 in triggering an immune response and indicated the diversity of NS1 as one of the genetic factors of TBEV pathogenicity.

Automated summary

Tick-borne encephalitis (TBE) is a zoonotic disease that can cause severe neurological complications or death. In this study, the nonstructural protein 1 (NS1) of the tick-borne encephalitis virus (TBEV) was investigated as a genetic determinant of TBE pathogenicity. The NS1 proteins of three TBEV strains belonging to different subtypes were found to have varying levels of accumulation and secretion in mouse cells. The NS1 proteins were also able to induce cytokine production and the profile of cytokines differed between the strains. These findings highlight the role of NS1 diversity in TBEV pathogenesis.