ISOLATION OF NATURALLY PROCESSED PEPTIDES FROM A TOXOPLASMA GONDII-INFECTED HUMAN B-LYMPHOMA CELL-LINE THAT ARE RECOGNIZED BY CYTOTOXIC T-LYMPHOCYTES

Naturally processed peptides derived from Toxoplasma gondii (T. gondii ) were acid extracted from T. gondii-infected cells and detected by cy totoxic T lymphocytes (CTL) derived from peripheral blood lymphocytes of a patient with chronic toxoplasmosis. The CTL lines were obtained b y weekly in vitro stimulation with a T. gondii-infected human B cell l ymphoma line, ARH, which shares HLA-A2 and -Cw4 determinants with the patient. The lytic activity of these CTL lines against T. gondii-infec ted ARH and ARH pulsed with fraction 29 of a reversed-phase high-perfo rmance liquid chromatography (HPLC) extract from T. gondii-infected AR H was inhibited by an anti-HLA-A, B, C monoclonal antibody (mAb) and a n anti-HLA-A2 mAb. Anti-HLA-DR mAb failed to block the lytic activity. Thus, the presentation of peptides by T. gondii-infected cells for CT L is mediated by HLA-A2 molecules. Interestingly, antigen presentation of ARH pulsed with naturally processed HPLC fraction 29 peptides was not inhibited by treatment with brefeldin A. The amino acid sequence o f the HLA-AZ-bound peptide in fraction 29 was in part consistent with the predictive algorithm of HLA-A2-binding peptide motifs.