Borrelial CNS co-infection was found in 6.7% and 2.3% of our patients with TBE, depending on the inclusion or exclusion of the 25 patients in whom borrelial CNS co-infection was defined by intrathecal synthesis of borrelial IgM, respectively (since this parameter is reported to have low diagnostic value in Lyme neuroborreliosis [30]), which is in the range of 1.9% to 18.8% in previous reports [4,5,8,9,10,12]. Here, CD40LG is linked to Lyme disease.