Summary
Staphylokinase is a potent highly fibrin-selective thrombolytic agent, but it induces
a humoral immune response in most treated patients. Staphylokinase-specific T-lymphocytes
can be found in normal healthy individuals, from whom a large panel of staphylokinasespecific
T-cells were cloned. The staphylokinase amino acid sequence 71-87 was widely recognized,
as it induced proliferation of T-cell clones isolated from 90% of the donors. Computer
modeling of this area, threaded as 11-mer peptides within the peptide-binding groove
of the major HLA-DR alleles, indicated two putative partially overlapping binding
sequences. The region-(71-87)-specific T-cell clones recognized either one or the
other minimal peptide, confirming that both sequences could be functional T-cell epitopes.
Furthermore, to guide the mutagenesis to eliminate T-cell reactivity, the contribution
of each residue to the HLA-DR-anchoring and T-cell receptor exposure was evaluated
for both binding motifs. Computer calculations combined with functional assays resulted
in the design of staphylokinasevariants, including 2 to 4 amino acid substitutions
in the region 71-87. These variants were no longer recognized by the region-(71-87)specific
T-cell clones, and importantly no new staphylokinase-variantspecific cellular immune
response could be measured.
Keywords
Staphylokinase - human - T-cell epitope - T-helper lymphocytes - de-immunization
