title: T-ceIl recognition of discrete regions of the thrombolytic drug streptokinase.
abstract: Streptokinase (SK) is a bacterial protein used clinically as a thrombolytic agent in humans. Administration of SK causes a rapid increase in the frequency of anti-SK T cells and the titre of specific anti-SK antibodies that, on subsequent administration of SK, may neutralize the activity of the drug or elicit allergic-type reactions. By locating and modifying the immunogenic T-cell epitopes within the SK protein, it is possible that an agent with reduced immunogenicity but equal efficacy may be produced. We have investigated the T-cell epitopes within SK using nine non-overlapping, recombinant peptide fragments of SK. We investigated the proliferative T-cell response of peripheral blood mononuclear cells obtained from patients before and 6 days after administration of SK for myocardial infarction. We also examined the response of cultured anti-SK T-cell lines derived from patients 6 days after treatment with SK. Before administration of SK, peripheral blood mononuclear cells from six of nine patients showed a proliferative response to SK. The response was significantly higher 6 days after administration of SK (P = 0.0004). Cultured T-cell lines showed similar proliferative responses to clinical-grade SK and recombinant SK. Marked differences in T-cell responses were apparent in response to each recombinant SK fragment (P = 0.04). The mean proliferative response exceeded background to only two peptides, peptide 2 (P = 0.04) and peptide 3 (P = 0.009). Peptide 3, representing amino acids 100-150 of mature SK, was recognized preferentially in the majority of assays. Marked variation in the T-cell response to SK following treatment with this agent was observed between subjects. Despite these differences, peptides 2 and 3 induced T-cell proliferation at a level significantly above background in the majority of subjects. These epitopes may represent a region of enhanced immunogenicity within SK.
authors.affiliation: Centre for Mechanisms of Human Toxicity, Institute for Lung Health, University of Leicester, UK.
authors.forename: W J
authors.initials: WJ
authors.lastname: Lawley
authors.forename: S
authors.initials: S
authors.lastname: Fletcher
authors.forename: I B
authors.initials: IB
authors.lastname: Squire
authors.forename: K L
authors.initials: KL
authors.lastname: Woods
authors.forename: C R
authors.initials: CR
authors.lastname: Hewitt
mesh_terms: D000704:Analysis of Variance; D001483:Base Sequence; D018929:Cell Culture Techniques; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000032:analysis*; D005343:Fibrinolytic Agents / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D013300:Streptokinase / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D018076:DNA, Complementary; D018984:Epitopes, T-Lymphocyte; D005343:Fibrinolytic Agents; D010446:Peptide Fragments; D013300:Streptokinase