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.

Persistence of tick-borne encephalitis virus in monkeys. V. Virus localization after subcutaneous inoculation.

In 28 Macaca rhesus monkeys inoculated subcutaneously (s.c.) with different strains and mutants of tick-borne encephalitis (TBE) virus and developing asymptomatic infection, TBE virus and the virus-specific antigen were found at different intervals up to 302 days post inoculation (p.i.) in the CNS and internal organs (liver, spleen, lymph nodes, kidneys). When cyclophosphane (CP) was used as an immunosuppressor, no significant changes in virus distribution were observed with the exception of more frequent isolations at early intervals from kidneys and at late intervals from spleen. With or without CP administration virus was found in the spinal cord at 3--6 days, in the cerebellum and subcortical ganglia at 11--14 days, in the cerebral cortex at 19 days p.i. Early after inoculation the virus was more frequently isolated from the CNS than from the internal organs; later (93--302 days p.i.) the persisting virus or virus-specific antigen were predominantly found in internal organs. The set of sensitive methods used facilitated to detect the persistence of TBE virus in noninfectious form in monkeys with asymptomatic infection.

Persistence of tick-borne encephalitis virus in monkeys. I. Features of experimental infection.

Sixty-seven Macaca rhesus monkeys were inoculated with 2 mutants and 3 virulent strains of tick-borne encephalitis (TBE) virus including strains isolated from patients with a chronic form of TBE. A model of the clinical course of acute, subacute, and chronic encephalitis was produced by intracerebral inoculation and that of asymptomatic infection was produced by subcutaneous inoculation [with or without administration of cyclophosphane (CP)]. Virus persistence developed after inoculation with all the strains, after non-fatal encephalitis and inapparent infection irrespective of CP administration. In monkeys recovering from encephalitis the virus persisted for at least 783 days. After asymptomatic infection, it persisted for 302 days; neither virus nor virus-specific antigen was detected at 356, 367, and 620 days.

Persistence of tick-borne encephalitis virus in monkeys. II. Effectiveness of methods used for virus detection.

Fifty monkeys (Macaca rhesus) inoculated with tick-borne encephalitis (TBE)virus intracerebrally or subcutaneously were examined. The efficiencies of different virus detection methods at 90 to 783 days after inoculation were: explantation of organs - 41.2%; co-cultivation of trypsinized organ cells and indicator cells in the presence of 5-bromo-2-iododeoxyuridine with detection of the virus-specific antigen by immunofluorescence - 43.7%, detection of infectious virus and complement-fixing antigen - 13.6%; immunofluorescence examination of organ impression smears - 29.3%; and examination of organ homogenates with detection of virus pathogenic for mice - 1.7%. the latter method was the least sensitive for the detection of persisting TBE virus, in spite of that in the first 3 weeks of infection its efficacy was 88.1% in examinations of clinically ill monkeys and 23.8% in the inapparent form of the infection.

[Gel filtration chromatography of tick-borne encephalitis virus on macropore glass]. / Gel'-filtratsionnaia khromatografiia virusa kleshchevogo éntsefalita na makroporistykh steklakh.

The capacity of some chemically treated porous glass to adsorb tissue culture virus of tick-borne encephalitis was studied. Chemical binding of albumin and succinanhydride with the porous glass matrix was found to eliminate virion adsorption on the carrier surface. This permitted to carry out gel filtration chromatography of several virus strains and to obtain highly purified preparations of tick-borne encephalitis virus. Gel filtration on modified porous glass with different pore sizes was used for the determinations of cromatographic radius of virus particle.