Expression of Immunoregulatory Receptors on T-Cells in CSF and Blood Samples of Patients with TBE

● Introduction: Tick-borne encephalitis (TBE) is a viral neuroinfection caused by the tick-borne encephalitis virus (TBEV), a Flavivirus, transmitted by Ixodes ticks in Europe and Asia. Infection progresses from a flu-like stage to neurological involvement, potentially leading to encephalitis and long-term complications. This study investigates T-cell cycle regulatory surface proteins in blood and cerebrospinal fluid (CSF) of TBE-infected patients, focusing on CD152 (CTLA-4) and CD279 (PD-1) expression on CD4+ and CD8+ T-cell subsets to assess immune regulation and exhaustion in the CNS. ● Aim of the Study: To compare the expression of CD152 and CD279 on CD4+ and CD8+ T-cell subsets in blood and CSF samples of 24 TBE-infected patients, analyzing their median percentages, median fluorescence intensity index (MFIx), and potential immune trends. ● Material and Methods: This study included 24 TBE patients (average age: 45.7 years, 15 males, 9 females). Flow cytometry was used to analyze CD8+CD152+, CD8+CD279+, CD4+CD152+, and CD4+CD279+ subsets in blood and CSF. Median values of % parent, median fluorescence, and MFIx were calculated. ● Results: The median percentage of CD8+ cells positive for CD152+ was 49.55% in blood and 43.45% in CSF, while CD4+CD152+ tended to be higher in CSF (58.0%) than in blood (51.9%), suggesting increased regulatory T-cell activity in the CNS. CD279+ expression remained low in both compartments, with CD8+CD279+ % parent at 4.7% (blood) and 2.05% (CSF). Albumin levels (median: 44.75 mg/dL) correlated with immune marker trends, suggesting a link between blood-brain barrier integrity and T-cell activation. ● Conclusion: These descriptive findings may provide insights into T-cell activation in TBE infection but require further research and validation.