Genetic characterisation of a tick-borne encephalitis virus isolated from the brain of a naturally exposed monkey (Macaca sylvanus)

In a recently published case study, we have described a clinical case of severe tick-borne encephalitis (TBE) in a monkey (Macaca sylvanus) after natural exposure (tick bite) in a TBE endemic area in Germany. Using histological, immunohistological, serological methods, and RT-PCR, the TBE virus infection was confirmed. Here, we describe the isolation of a TBE virus from the brain tissue in Vero-B4 cell cultures and the sequencing of the complete genome of that isolate. The isolated TBE virus strain (named "Salem") is closely related to the Kumlinge strain or strain Neudoerfl, the prototype of the Central European TBE virus subtype. However, a total of 268 nt changes were found in comparison with TBE virus strain Neudoerfl resulting in 28 amino acid changes, none of which affecting any of the known or supposed functional regions of the viral genome. Further investigation of the distribution of viral antigen in brain tissue and characterisation of the host's inflammatory reactions by immunohistology revealed similarities between the course of the TBE virus infection in the macaque and acute to peracute cases of TBE in humans.