Tick-Borne Encephalitis virus (TBEV) causes dangerous central nervous system 
diseases in humans. General infection leads to the development of meningitis or 
encephalitis, which is characterized by swelling of the brain due to 
inflammation. Tetracyclines may act locally to moderate inflammation in the CNS. 
In this study, we investigated the potential clinical benefits of administering 
tetracycline hydrochloride to patients hospitalized due to suspected TBEV 
infection presenting with fever and evidence of a recent tick bite. We also 
characterized an acute immune response to TBEV by profiling certain cytokines 
and soluble receptors in Tetracycline-treated and untreated patients. Increased 
serum levels of TNF-alpha, IL-1 alpha and IL-6 were found in all patients at 
admission. Soluble receptors presented in the serum of patients in a magnitude 
higher levels than the corresponding cytokines and were increasing during first 
weak of hospitalization. Levels of IL-10 were also rising during that period. In 
our study tetracycline hydrochloride acted as an immunomodulator, which was able 
to reduce manifestations of inflammation response during TBE course; this action 
led to quicker improvement of symptoms and, consequently, to a faster clinical 
recovery. The positive result of tetracycline hydrochloride treatment was 
accompanied by certain particularities in the dynamics of studied cytokines and 
receptors: the concentrations of IL-6, IL-1 beta, TNF-alpha dropped quicker and 
reached lower levels, and the concentrations of sIL-6R, IL-1RA, sTNFR1 increased 
faster and reached higher maximum levels in the tetracycline-treated groups. 
Children had the highest levels of IL-6, which were not neurotoxic.