Size-variable strain-specific protective antigen for potomac horse fever

Abstract

An isolated and purified antigen which is expressed by a wild-type E. risticii strain and is specific to the strain. The present invention also relates to nucleic acid constructs which encode the antigen, expression vectors, transformed host cells, and methods for producing the antigen.

1 . An isolated and purified antigen which is expressed by a wild-type  E. risticii  strain and is specific to the wild-type  E. risticii  strain.  
     
     
         2 . The antigen of  claim 1 , which stimulates a protective immune response against infection by the wild-type  E. risticii  strain when a host is immunized with the antigen.  
     
     
         3 . The antigen of  claim 1 , which stimulates a protective immune response against infection by at least one other wild-type  E. risticii  strain when a host is immunized with the antigen.  
     
     
         4 . The antigen of  claim 1 , which has a molecular weight of about 40 to about 90 kDa.  
     
     
         5 . The antigen of  claim 1 , which is expressed by  E. risticii  strain 25-D.  
     
     
         6 . The antigen of  claim 1 , which is expressed by  E. risticii  strain 90-12.  
     
     
         7 . The antigen of  claim 1 , which is expressed by ATCC type  E. risticii  strain.  
     
     
         8 . The antigen of  claim 1 , which comprises the amino acid sequence shown in FIG. 2.  
     
     
         9 . The antigen of  claim 1 , which comprises the amino acid sequence shown in FIG. 3.  
     
     
         10 . The antigen of  claim 1 , which comprises the amino acid sequence shown in FIG. 4.  
     
     
         11 . An isolated and purified nucleic acid encoding the antigen of  claim 1 .  
     
     
         12 . An expression vector comprising the nucleic acid of  claim 6 .  
     
     
         13 . A host cell transformed with the expression vector of  claim 12 , wherein the transformed host produces the antigen.  
     
     
         14 . A method of produciLng an antigen which is expressed by a wild-type  E. risticii  strain and is specific to the wild-type  E. risticii  strain, comprising culturing the transformed host cell of  claim 13  in a suitable culrure medium, and isolating the antigen.  
     
     
         15 . An immunogenic pharmaceutical composition, comprising the antigen of  claim 1  and a pharmaceutically acceptable carrier.  
     
     
         16 . A method of inducing an immune response, comprising administering an effective amount of the immunogenic composition of  claim 15  to a host.  
     
     
         17 . An isolated and purified protein comprising an amino acid sequence selected from the group consisting of the amino acid sequence recited in FIG. 2, the amino acid sequence recited in FIG. 3 and the amino acid sequence recited in FIG. 4.  
     
     
         18 . The protein of  claim 17 , comprising the amino acid sequence recited in FIG. 2.  
     
     
         19 . The protein of  claim 17 , comprising the amino acid sequence recited in FIG. 3.  
     
     
         20 . The protein of  claim 17 , comprising the amino acid sequence recited in FIG. 4.  
     
     
         21 . The protein of  claim 17 , which consists of said amino acid sequence.  
     
     
         22 . An isolated and purified nucleic acid encoding the protein of  claim 17 .  
     
     
         23 . An expression vector comprising the nucleic acid of  claim 22 .  
     
     
         24 . A host cell transformed with the expression vector of  claim 23 , wherein the transformed host produces the protein.  
     
     
         25 . A method of producing a protein, comprising culturing the transformed host cell of  claim 24  in a suitable culture medium, and isolating the antigen.  
     
     
         26 . An immunogenic pharmaceutical composition, comprising the protein of  claim 17  and a pharmaceutically acceptable carrier.  
     
     
         27 . A method of inducing an immune response, comprising administering an effective amount of the immunogenic composition of  claim 26  to a host.