Ehrlichia chaffeensis 28 kDa outer membrane protein multigene family

Abstract

The 28-kDa outer membrane proteins (P28) of Ehrlichia chaffeensis are encoded by a multigene family consisting of 21 members located in a 23-kb DNA fragment in the genome of E. chaffeensis . Fifteen of these proteins are claimed herein as novel sequences. The amino acid sequence identity of the various P28 proteins was 20-83%. Six of 10 tested p28 genes were actively transcribed in cell culture grown E. chaffeensis . RT-PCR also indicated that each of the p28 genes was monocistronic. These results suggest that the p28 genes are active genes and encode polymorphic forms of the P28 proteins. The P28s were also divergent among different isolates of E. chaffeensis . The large repertoire of the p28 genes in a single ehrlichial organism and antigenic diversity of the P28 among the isolates of E. chaffeensis suggest that the P28s may be involved in immune avoidance.

What is claimed is:  
     
         1 . DNA encoding one or more P28 proteins from  Ehrlichia chaffeensis , wherein said proteins have amino acid sequences selected from the group consisting of SEQ ID No. 1, SEQ ID No.2, SEQ ID No. 3, SEQ ID No. 4, SEQ ID No. 5, SEQ ID No. 6, SEQ ID No. 7, SEQ ID No. 8, SEQ ID No. 9, SEQ ID No. 10, SEQ ID No 11, SEQ ID No. 12, SEQ ID No. 13, SEQ ID No. 20 and SEQ ID No. 21, and wherein said DNA is selected from the group consisting of: 
 (a) isolated DNA which encodes said P28 proteins;    (b) isolated DNA which hybridizes to isolated DNA of (a) above under high stringency conditions consisting of hybridization at 42° C. in the presence of about 50% formamide, a first wash at 65° C. with 2×SSC containing 1% SDS and a second wash at 65° C. with 0.1×SSC, and which encodes said P28 proteins; and    (c) isolated DNA differing from the isolated DNAs of (a) and (b) above in codon sequence due to the degeneracy of the genetic code, and which encodes said P28 proteins.    
     
     
         2 . The DNA of  claim 1 , wherein said DNA is selected from the group consisting of GenBank accession number AF230642 and GenBank accession number AF230643.  
     
     
         3 . The DNA of  claim 1 , wherein said DNA consists of a single locus of  Ehrlichia chaffeensis  encoding said P28 proteins.  
     
     
         4 . The DNA sequences of  claim 3 , wherein said locus is a multigene locus of 23 kb length.  
     
     
         5 . A vector comprising the DNA of  claim 1  and regulatory elements necessary for expression of the DNA in a cell.  
     
     
         6 . A host cell transfected with the vector of  claim 5 , said vector expressing a P28 protein.  
     
     
         7 . The host cell of  claim 6 , wherein said cell is selected from group consisting of bacterial cells, mammalian cells, plant cells and insect cells.  
     
     
         8 . The host cell of  claim 7 , wherein said bacterial cell is  E. coli.    
     
     
         9 . An isolated and purified  Ehrlichia chaffeensis  P28 surface protein encoded by the DNA of  claim 1 .  
     
     
         10 . An isolated and purified P28 protein having a n amino acid sequence selected from the group consisting of SEQ ID No. 1, SEQ ID No.2, SEQ ID No. 3, SEQ ID No. 4, SEQ ID No. 5, SEQ ID No. 6, SEQ ID No. 7, SEQ ID No. 8, SEQ ID No. 9, SEQ ID No. 10, SEQ ID No 11, SEQ ID No. 12, SEQ ID No. 13, SEQ ID No. 20 and SEQ ID No. 21.  
     
     
         11 . An antibody directed against the P28 protein of  claim 10 .  
     
     
         12 . The antibody of  claim 11 , wherein said antibody is a monoclonal antibody.  
     
     
         13 . A vaccine against  Ehrlichia chaffeensis  comprising one or more of the proteins of claim  10 .