Mutants of streptococcal toxin A and methods of use

Abstract

This invention is directed to mutant SPE-A toxins or fragments thereof, vaccine and pharmaceutical compositions, and methods of using the vaccine and pharmaceutical compositions. The preferred SPE-A toxin has at least one amino acid change and is substantially non-lethal compared with the wild type SPE-A toxin. The mutant SPE-A toxins can form vaccine compositions useful to protect animals against the biological activities of wild type SPE-A toxin.

1 . A mutant SPE-A toxin or fragment thereof, wherein the mutant has at least one amino acid change and is substantially nonlethal compared with a protein substantially corresponding to wild type SPE-A toxin.  
     
     
         2 . A mutant SPE-A toxin according to  claim 1 , wherein the mutant SPE-A toxin comprises one to six amino acid substitutions; and 
 wherein at least one of the substituted amino acids is positioned in N-terminal alpha helix  3 , in domain B beta strand  1 , in domain B beta strand  2 , in domain B beta strand  3 , in domain A beta strand  6 , in domain A beta strand  8 , in domain A beta strand  9 , in domain A beta strand  10 , or is a cysteine.    
     
     
         3 . A mutant SPE-A toxin according to  claim 1 , wherein the mutant SPE-A toxin comprises one to six amino acid substitutions; and 
 wherein at least one of the substituted amino acids is asparagine-20, aspartic acid  45 , lysine-157, or cysteine-98.    
     
     
         4 . The mutant SPE-A toxin of  claim 3 , wherein the at least one amino acid substitution comprises the substitution of asparagine-20 to aspartic acid, glutamic acid, lysine or arginine; the substitution of cysteine 98 to serine, alanine, glycine, or threonine; the substitution of lysine-157 to glutamic acid or aspartic acid; or the substitution of aspartic acid-45 to asparagine, glutamine, serine, threonine, or alanine.  
     
     
         5 . The mutant SPE-A toxin of  claim 4 , wherein the at least one amino acid substitution comprises asparagine-20 to aspartic acid, cysteine 98 to serine, aspartic acid-45 to asparagine, or lysine-157 to glutamic acid.  
     
     
         6 . The mutant SPE-A toxin of  claim 3 , wherein the at least one amino acid substitution comprises substitution of asparagine-20.  
     
     
         7 . The mutant SPE-A toxin of  claim 6 , wherein the substitution is asparagine-20 to aspartic acid.  
     
     
         8 . The mutant SPE-A toxin of  claim 6 , further comprising substitution of cysteine-98, or lysine-157.  
     
     
         9 . The mutant SPE-A toxin of  claim 8 , wherein the substitution is cysteine 98 to serine, or lysine-157 to glutamic acid.  
     
     
         10 . The mutant SPE-A toxin of  claim 6 , further comprising substitution of cysteine-98 and aspartic acid-45.  
     
     
         11 . The mutant SPE-A toxin of  claim 10 , wherein the cysteine-98 is substituted to serine and aspartic acid-45 is substituted to asparagine.  
     
     
         12 . The mutant SPE-A toxin of  claim 1 , wherein the mutant has at least one of the following characteristics: the mutant has a decrease in mitogenicity for T-cells, the mutant does not substantially enhance endotoxin shock, the mutant is not lethal, or the mutant is nonlethal but retains mitogenicity comparable to that of the wild type SPE-A toxin.  
     
     
         13 . A vaccine for protecting animals against at least one biological activity of wild-type SPE-A comprising: an effective amount of at least one mutant SPE-A toxin according to  claim 1 .  
     
     
         14 . A pharmaceutical composition comprising: a mutant SPE-A according to  claim 1  in admixture with a physiologically acceptable carrier.  
     
     
         15 . A DNA sequence encoding a mutant SPE-A toxin according to  claim 1 .  
     
     
         16 . A stably transformed host cell comprising a DNA sequence according to  claim 15 .  
     
     
         17 . A method for protecting an animal against at least one biological activity of a wild type SPE-A comprising: administering a vaccine according to  claim 13  to an animal.  
     
     
         18 . A method for reducing symptoms associated with toxic shock comprising: 
 administering a vaccine according to  claim 13  to an animal.