Persistence of tick-borne encephalitis virus IV. Virus localization after intracerebral inoculation.

Tick-borne encephalitis (TBE) virus was isolated from the brains and spinal cords, blood, livers, lymph nodes and kidneys from Macaca rhesus monkeys showing acute and subacute fatal encephalitis. In subacute encephalitis, virus titres in the CNS were lower than in acute disease (3.0--6.2 against 3.8--8.3 log LD50/ml). TBE virus localization in chronic encephalitis was largely the same as in acute and subacute disease. In monkeys with a chronic course and stable paralysis of the upper extremity, infectious TBE virus was isolated on day 383 from subcortical ganglia and spinal cord. In lymph nodes and spleen, it could be detected only by a combination of methods (co-cultivation in association with fluorescent antibody technique and complement-fixation test, explantation of organ fragments) more sensitive than is the inoculation of mice with organ homogenates. TBE virus was detected by the same methods on day 90 in the CNS and internal organs of a monkey with chronic encephalitis in the stage of remission.