THE SUPPOSEDLY ATTENUATED HY-HK VARIANT OF HIGHLY VIRULENT HYPR STRAIN OF TICK-BORNE ENCEPHALITIS VIRUS IS OBVIOUSLY A STRAIN OF LANGAT VIRUS

摘要

The pathogenesis of the disease caused by Tick-borne encephalitis virus (TBEV; the species Tick-borne encephalitis virus, the genus Flavivirus, the family Flaviviridae) (J) has been intensively studied in the 60s and 70s of the last century. Many of the classical studies were based on experimental attenuation of the virus and subsequent characteri/ation of biological properties of the attenuated virus under in vitro as well as in vivo conditions. In 1966 Mayer has reported a successful attenuation ofthe highly virulent strain Hypr of TBEV (2). The attenuated variant, designated Hy-HK, was obtained by passaging of the parental strain in cultures of a line of human amnion cells for more than 400 days, then in cultures in primary cultures of hamster kidney cells (HK cells; 28 passages), and finally in mouse brains (2 passages). Hy-HK formed small plaques in chick embryo cell cultures. In suckling mice, it did not cause a disease after subcutaneous (s.c.) administration, but it led to the developmentof encephalitis and death after intracerebral (i.e.) inoculation (2). More interestingly, Hy-HK exhibited strongly attenuated phenotype in Macaco, mullata monkeys; intrathalamical inoculation of Hy-HK did not cause any obvious symptoms of disease for atleast 48 days post infection (2).