Method for rendering streptokinase less immunogenic to a human
Protein, or parts of proteins, may be rendered non-immunogenic, or less immunogenic, to a given species by identifying in their amino acid sequences one or more potential epitopes for T-cells of the given species and modifying the amino acid sequence to eliminate at least one of the T-cell epitopes. This eliminates or reduces the immunogenicity of the protein when exposed to the immune system of the given species. Monoclonal antibodies and other immunoglobulin-like molecules can particularly benefit from being de-immunised in this way: for example, mouse-derived immunoglobulins can be de-immunised for human therapeutic use.
1. A method of rendering streptokinase non-immunogenic or less immunogenic when exposed to the immune system of a human, the method comprising the steps of:
(a) identifying a first set of potential T-cell epitope sequences within the amino acid residue sequence of streptokinase (SEQ ID NO: 252) by (i) analysing said amino acid sequence for the presence of MHC class II binding motifs, and (ii) comparing the MHC class II binding motifs in the streptokinase amino acid residue sequence with human MHC binding motifs available from an MHC database;
(b) comparing the first set of potential T-cell epitope sequences identified in step (a) with human immunoglobulin variable region germ line amino acid residue sequences available from a human germ-line sequence database to identify a subset of potential T-cell epitopes within the streptokinase amino acid residue sequence that are not present in human immunoglobulin variable region germ-line sequences; and
(c) preparing a de-immunized streptokinase polypeptide having the amino acid residue sequence of SEQ ID NO: 252 but including at least one amino acid residue substitution that eliminates from the streptokinase amino acid residue sequence at least one epitope sequence from the subset identified in step (b), wherein the de-immunized streptokinase polypeptide has the amino acid residue sequence of SEQ ID NO: 253.