Modified forms of pseudomonas exotoxin a

Abstract

Pseudomonas exotoxin A or “PE” is a 66 kD, highly potent, cytotoxic protein secreted by the bacterium Pseudomonas aeruginosa . Various forms of PE have been coupled to other proteins, such as antibodies, to generate therapeutically useful cytotoxin conjugates that selectively target cells of a desired phenotype (such as tumor cells). In the present invention, peptides spanning the sequence of an approximately 38 kD form of Pseudomonas exotoxin A protein were analyzed for the presence of immunogenic CD4+ T cell epitopes. Six immunogenic T cell epitopes were identified. Residues were identified within each epitope for introduction of targeted amino acid substitutions to reduce or prevent immunogenic T-cell responses in PE molecules which may be administered to a heterologous host.

1 . A polypeptide having at least one  Pseudomonas  exotoxin A (PE-A) biological activity, wherein said polypeptide comprises one or more amino acid substitutions compared to a wild-type PE-A polypeptide, wherein said one or more amino acid substitutions is a substitution of a different amino acid at one or more positions corresponding to amino acid residues in the polypeptide of SEQ ID NO: 1, wherein said substitution positions are selected from the group consisting of:
 a) isoleucine (I) at position 141;   b) arginine (R) at position 146;   c) glycine (G) at position 147;   d) glutamine (Q) at position 149;   e) asparagine (N) at position 150;   f) threonine (T) at position 152;   g) valine (V) at position 189;   h) arginine (R) at position 192;   i) glutamine (Q) at position 194;   j) aspartic acid (D) at position 197;   k) serine (S) at position 241;   l) isoleucine (I) at position 321; and   m) glutamine (Q) at position 326.   
     
     
         2 . The polypeptide of  claim 1 , wherein said one or more amino acid substitutions is a conservative amino acid substitution. 
     
     
         3 . The polypeptide of  claim 1 , wherein said one or more amino acid substitutions is selected from the group consisting of:
 a) isoleucine (I) at position 141 is substituted with alanine (A), threonine (T), or histidine (H);   b) arginine (R) at position 146 is substituted with glutamine (Q) or alanine (A);   c) glycine (G) at position 147 is substituted with serine (S);   d) glutamine (Q) at position 149 is substituted with threonine (T);   e) asparagine (N) at position 150 is substituted with alanine (A);   f) threonine (T) at position 152 is substituted with alanine (A) or arginine (R);   g) valine (V) at 189 is substituted with alanine (A);   h) arginine (R) at position 192 is substituted with alanine (A) or glutamine (Q);   i) glutamine (Q) at position 194 is substituted with arginine (R);   j) aspartic acid (D) at position 197 is substituted with lysine (K);   k) serine (S) at position 241 is substituted with threonine (T), asparagine (N), lysine (K), or proline (P);   l) isoleucine (I) at position 321 is substituted with alanine (A), asparagine (N), histidine (H), threonine (T), or glutamine (Q); and   m) glutamine (Q) at position 326 is substituted with glutamic acid (E).   
     
     
         4 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution for isoleucine (I) at position 141, a substitution for threonine (T) at position 152, a substitution for arginine (R) at position 192, a substitution for aspartic acid (D) at position 197, a substitution for serine (S) at position 241, and a substitution for glutamine (Q) at position 326. 
     
     
         5 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of threonine (T) or alanine (A) for isoleucine (I) at position 141, a substitution alanine (A) or arginine (R) for threonine (T) at position 152, a substitution of alanine (A) for arginine (R) at position 192, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         6 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of threonine (T) for isoleucine (I) at position 141, a substitution alanine (A) for threonine (T) at position 152, a substitution of alanine (A) for arginine (R) at position 192, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         7 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of alanine (A) for isoleucine (I) at position 141, a substitution alanine (A) for threonine (T) at position 152, a substitution of alanine (A) for arginine (R) at position 192, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         8 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution for isoleucine (I) at position 141, a substitution for threonine (T) at position 152, a substitution for aspartic acid (D) at position 197, a substitution for serine (S) at position 241, and a substitution for glutamine (Q) at position 326. 
     
     
         9 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution for isoleucine (I) at position 141, a substitution for threonine (T) at position 152, a substitution for arginine (R) at position 192, a substitution for aspartic acid (D) at position 197, and a substitution for serine (S) at position 241. 
     
     
         10 . The isolated polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of alanine (A) or threonine (T) for isoleucine (I) at position 141, a substitution of arginine (R) or alanine (A) for threonine (T) at position 152, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         11 . The isolated polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of alanine (A) for isoleucine (I) at position 141, a substitution of arginine (R) for threonine (T) at position 152, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         12 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of alanine (A) for isoleucine (I) at position 141, a substitution of alanine (A) for threonine (T) at position 152, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         13 . The polypeptide of  claim 1 , wherein said polypeptide comprises a substitution of threonine (T) for isoleucine (I) at position 141, a substitution of alanine (A) for threonine (T) at position 152, a substitution of lysine (K) for aspartic acid (D) at position 197, a substitution of threonine (T) for serine (S) at position 241, and a substitution of glutamic acid (E) for glutamine (Q) at position 326. 
     
     
         14 . The polypeptide of  claim 1 , wherein the at least one  Pseudomonas  exotoxin A (PE-A) biological activity comprises the ability to inhibit in vitro transcription/translation compared to a corresponding wild-type or non-substituted PE-A polypeptide, wherein said ability to inhibit in vitro transcription/translation is in an amount selected from the group consisting of:
 (a) at least 5% inhibition;   (b) at least 10% inhibition;   (c) at least 15% inhibition;   (d) at least 20% inhibition;   (e) at least 25% inhibition;   (f) at least 30% inhibition;   (g) at least 40% inhibition;   (h) at least 50% inhibition;   (i) at least 60% inhibition;   (j) at least 70% inhibition;   (k) at least 80% inhibition;   (l) at least 90% inhibition;   (m) at least 100% inhibition;   (n) about 100% inhibition; and   (o) 100% inhibition.   
     
     
         15 . The polypeptide of  claim 1 , comprising a number of amino acid substitutions selected from the group consisting of:
 a) 1 amino acid substitution;   b) 2 amino acid substitutions;   c) 3 amino acid substitutions;   d) 4 amino acid substitutions;   e) 5 amino acid substitutions; and   f) 6 amino acid substitutions.   
     
     
         16 . The polypeptide of  claim 1 , wherein said polypeptide comprises one or more amino acid substitutions which prevent or reduce host immunogenic responses compared to the same polypeptide without said one or more amino acid substitutions. 
     
     
         17 . The polypeptide of  claim 16 , wherein host immunogenic responses are prevented or reduced in a human host. 
     
     
         18 . The polypeptide of  claim 1 , wherein the last five or six amino acids in said polypeptide comprise one or more amino acid sequences selected from the group consisting of:
 (i) Arg-Glu-Asp-Leu-Lys;   (ii) Arg-Glu-Asp-Leu;   (iii) Lys-Asp-Glu-Leu;   (iv) Glu-Asp-Leu-Lys; and   (v) a dimer, trimer, pentamer, hexamer, septamer, or octamer of (i), (ii), or (iii), or any combination thereof.   
     
     
         19 . The polypeptide of  claim 1 , wherein said polypeptide has one or more biological activities selected from the group consisting of:
 a) eukaryotic cell killing activity (cell cytotoxicity);   b) inhibits translation elongation factor EF-2 biological activity;   c) induces or catalyzes ADP-ribosylation of EF-2; and   d) inhibits protein synthesis.   
     
     
         20 . The polypeptide of  claim 1 , wherein said one or more amino acid substitutions prevent or reduce host immunogenic responses compared to the same polypeptide without the corresponding said one or more amino acid substitutions. 
     
     
         21 .- 56 . (canceled)