Modified Chimeric superantigens and their use
A conjugate between a target-seeking moiety and a modified superantigen, characterized in that the superantigen is a wild-type superantigen (SA I) in which an amino acid residue in a superantigen region (region I) determining binding to TCR, preferably TCRVβ, and T cell activation have been replaced by another amino acid residue while retaining the ability to activate a subset of T cells. In preferred embodiment the modified superantigen is a chimer between at least two wild-type superantigens (SA I, SA II etc) characterized in that one or more amino acid residues in a region determining binding to TCR and T cell activation have been interchanged between various wild-type superantigens. A therapeutic method making use of modified/chimeric superantigens as defined in the preceding paragraphs. An antibody preparation in which the cysteine residues that provide for interchain disulfide bonds have been mutated so as to forbid interchain disulfide bridges, preferably to serine residues, for use as pharmaceutical.
1. A conjugate comprising a bacterial superantigen and an immunoglobulin, wherein the superantigen comprises Staphylococcal enterotoxin E, SEQ ID NO: 8, mutated in the following positions relative to SEQ ID NO: 8, at position 20, a glycine or a conserved substitution of glycine; at position 21, a threonine or a conserved substitution of threonine; at position 24, a glycine or a conserved substitution of glycine; at position 27, a lysine or a conserved substitution of lysine, and at position 225 and/or 227, an alanine or a conserved substitution of alanine, such that the modified superantigen induces increased cytotoxicity relative to unmodified Staphylococcal enterotoxin E, and reduced binding to endogenous antibodies relative to Staphylococcal enterotoxin A.
2. The conjugate of claim 1 , wherein the Staphylococcal enterotoxin has a glycine at position 20.
3. The conjugate of claim 1 , wherein the Staphylococcal enterotoxin has a threonine at position 21.
4. The conjugate of claim 1 , wherein the Staphylococcal enterotoxin has a glycine at position 24.
5. The conjugate of claim 1 , wherein the Staphylococcal enterotoxin has a lysine at position 27.
6. The conjugate of claim 1 , wherein the immunoglobulin is an antibody or an antigen-binding fragment of an antibody.
7. The conjugate of claim 6 , wherein the immunoglobulin is an antibody.
8. The conjugate of claim 1 , wherein the immunoglobulin is an antigen-binding fragment of a monoclonal antibody to the 5T4 antigen.
9. The conjugate of claim 8 , wherein the Vkappa chain of the antigen-binding fragment of the monoclonal antibody to the 5T4 antigen comprises SEQ ID NO:6 having the following amino acid substitutions in SEQ ID NO:6, a serine or a conserved substitution of serine at position 10, a lysine or a conserved substitution of lysine at position 45; a serine or a conserved substitution of serine at position 63, a serine or a conserved substitution of serine at position 67, a leucine or a conserved substitution of leucine at position 73, a serine or a conserved substitution of serine at position 77, a valine or a conserved substitution of valine at position 78.