CD40LG and tick-borne encephalitis: Suspecting encephalitis, appropriate serum and cerebrospinal fluid (CSF) tests were performed: herpes simplex virus 1/2 DNA, herpes 6 virus DNA, and herpes 8 virus DNA were negative; IgM and IgG antibodies against varicella-zoster, Lyme disease, and tick-borne encephalitis were negative (with a few exceptions of a positive IgG of tick-borne encephalitis after vaccination and IgG against varicella-zoster after varicella infection).