Bogovič et al.
Low virus-specific IgG antibodies in adverse clinical course and outcome of tick-borne encephalitis.
Microorganisms. 2021; 9(2):332,

Clinical manifestations of TBE are believed to be the result of a combination of direct viral cytolytic effects and immune-mediated tissue damage, involving both humoral and cellular immune response. Findings from animal models indicate that low TBE neutralizing antibody titers are associated with higher fatality. Corresponding analyses in TBE patients are limited. A Slovenian team has analyzed in greater detail the relationship between TBE antibodies during the early phase of meningoencephalitis and the clinical course and outcome in a cohort of 691 patients, aged ≥ 18 years, who have been hospitalized during 2007 to 2012.

All patients lived in Slovenia and were most likely to be infected by the European subtype. Median duration of the meningoencephalitis phase prior to hospitalization was 4 days, with 62% of patients having meningoencephalitis, 33% meningitis, and 5% meningoencephalomyelitis. The median IgG serum level was 37.3 U/ml, ranging from not detectable to 896 U/ml.

Patients with low TBE antibody titers had a more severe illness. Seronegative patients were hospitalized longer compared to seropositive patients (13 vs. 8 days) and more often needed treatment in the intensive care unit (22% vs. 8%). The case fatality rate was higher, too. Patients with meningoencephalomyelitis and meningoencephalitis had lower antibody titers than those with meningitis, indicating that some patients did not develop a robust immune response which was associated with a more difficult disease course. For 401 patients, information was available for the long-term outcome 2 to 7 years after TBE. IgG seronegative patients tended to have more often post-encephalitic syndrome.

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