Immunization with recombinant subolesin does not reduce tick infection with tick-borne encephalitis virus nor protect mice against disease

Abstract

Tick-borne encephalitis (TBE) is a growing zoonotic disease caused by tick-borne encephalitis virus (TBEV) infection. Although effective vaccines for TBEV are available, on-going vaccination efforts are insufficient to prevent increase in TBE cases annually. Vaccination with arthropod vector antigens to reduce vector infestations and vector capacity allows control of several vector-borne diseases by targeting their common vector. Subolesin (SUB) is a tick protective antigen that has a role in tick innate immunity and other molecular pathways and has been shown to protect against tick infestations and infection by vector-borne pathogens. However, SUB expression and the effect of SUB immunization have not been evaluated for tick-borne viruses. Herein, we showed that SUB expression is downregulated during Ixodes ricinus tick feeding but induced in ticks infected with TBEV, thus supporting a role for this molecule in tick innate immune response to virus infection. Immunization with recombinant SUB reduced SUB mRNA levels in nymphs co-feeding with infected females and suggested and effect on tick infestations in mice. However, SUB immunization did not reduce tick infection with TBEV nor protect mice against TBE. These results suggested that SUB is not a good candidate antigen for vaccination against TBEV and support the characterization of tick-pathogen interactions to identify mechanisms that could be targeted to reduce TBEV infection and transmission by ticks.