Detection of Borrelia burgdorferi-Specific CD8⁺ Cytotoxic T Cells in Patients with Lyme Arthritis

T cells are believed to play an important role in the pathogenesis of Lyme arthritis (LA), an inflammatory joint disease caused by the spirochete Borrelia burgdorferi (Bb). The presence or absence of certain Bb-specific CD4⁺ T helper cells has been associated with prognosis. Since recent observations suggested the activation of CD8⁺ T cells during infection with Bb, we searched for CD8⁺ cytotoxic T lymphocytes in patients with LA. CD8⁺ T cell lines were generated from peripheral blood and synovial fluid of five patients with LA. In addition, CD8⁺ T cells were expanded by Ag-specific stimulation in bulk cultures. A cytotoxicity assay was established using target cells infected with recombinant vaccinia viruses expressing the borrelial proteins outer surface protein (Osp) A, OspB, or flagellin. We found Bb-specific CTL lines derived from the peripheral blood of three patients with LA with specificity for flagellin, OspA, and OspB. All Bb-specific CTL lines were CD3⁺, CD8⁺, and TCRαβ⁺, and cytotoxic activity was HLA class I restricted. Moreover, CD8⁺ T cells expanded by Ag-specific stimulation in vitro demonstrated Bb-specific and HLA class I-restricted lysis toward individual borrelial proteins. Interestingly, Bb-specific lytic activity was only detected in patient samples obtained after the disappearance of arthritis. We report the detection of Bb-specific cytotoxic CD8⁺ T cells in patients with LA. The induction of specific CD8⁺ T cells may play an important role in disease control and may have important bearings for the development of effective vaccines against Lyme borreliosis.