| Research Abstract |
Naturally processed peptides derived from Toxoplasma gondii (T.gondii) -infected cells were acid extracted and detected by cytotoxic T lymphocytes (C) induced from peripheral blood lymphocytes of a patient with chronic toxoplasmosis. The CTL lines were obtained by weekly in vitro stimulation with a T.gondii-infected human B lymphoma line, ARH,which shares HLA-A2 and Cw4 determinants with the patient. The lytic activity of these CTL lines against T.gondii-infected ARH and ARH pulsed with fraction 29 of a reversed-phase high-performance liquid chromatography (RP-HPLC) extract from T.gondii-infected ARH was inhibited by an anti-HLA-A,B,C monoclonal antibody (mAb) and an 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 CTL is mediated by HLA-A2 molecules. The peptides bound to HLA-A2 molecules were purified with an anti-HLA-A2 mAb-coupled immunoadsorbent column from T.gondii-infected ARH cell lysate. The peptides dissociated from the complex of HLA-A2 molecules and fractionated by RP-HPLC in fraction 29 were submitted for sequential NH_2-terminal Edman degradation. The amino acid sequence analysis of fraction 29 revealedthat a dominant leucine was found at position 2, isoleucine was found at position 3, phenylalanine was found at position 8, and methionine and phenylalanine were dominant at position 9. Thus, the amino acid sequence of the HLA-A2-bound peptide in fraction 29 was in part consistent with the predictive algorithm of HLA-A2-binding peptide motifs.
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