Attenuated vaccines to protect against tick-borne ehrlichia species infections

Abstract

Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0660, Ech_0379, and Ech_0230, and their homologs of other related rickettsial pathogens.

1 . An immunogenic composition useful to elicit an immune response against  Ehrlichia  infection in a subject, said composition comprising live, attenuated  E. chaffeensis  dispersed in a pharmaceutically-acceptable carrier, said live, attenuated  E. chaffeensis  comprising a mutation in one or more target genes that results in attenuated growth of the bacterium in a vertebrate host organism. 
     
     
         2 . The composition of  claim 1 , wherein said  E. chaffeensis  is  E. chaffeensis  str. Arkansas. 
     
     
         3 . The composition of  claim 1 , wherein said infection is rickettsial infection. 
     
     
         4 . The composition of  claim 1 , wherein said infection is tick-transmitted  E. chaffeensis  infection. 
     
     
         5 . The composition of  claim 1 , wherein said host organism is selected from the group consisting of human, canine, and deer. 
     
     
         6 . The composition of  claim 1 , wherein said mutation is an insertion or deletion in a protein coding region of said target gene. 
     
     
         7 . The composition of  claim 1 , wherein said one or more target genes are selected from the group consisting of Ech_0660 (SEQ ID NO:2), Ech_0379 (SEQ ID NO:4), and Ech_0230 (SEQ ID NO:6). 
     
     
         8 . The composition of  claim 1 , wherein said mutation does not attenuate growth of said bacterium in an invertebrate host organism. 
     
     
         9 . The composition of  claim 1 , wherein said mutation results in inhibition and/or inactivation of transcription and/or translation of a gene product selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, and SEQ ID NO:7. 
     
     
         10 . The composition of  claim 1 , wherein said mutation comprises an insertion of a recombinant sequence into said target gene. 
     
     
         11 . The composition of  claim 10 , wherein said mutation is an insertion, wherein said insertion sequence comprises at least one heterologous sequence, and optionally at least one reporter gene stably incorporated therein. 
     
     
         12 . The composition of  claim 1 , wherein said mutation comprises insertion of SEQ ID NO:8 or SEQ ID NO:9 into the target gene. 
     
     
         13 . The composition of  claim 1 , wherein said mutation in one or more target genes results in a mutated gene selected from the group consisting of SEQ ID NO:10, SEQ ID NO:11, and SEQ ID NO:12. 
     
     
         14 . The composition of  claim 1 , wherein said carrier is selected from the group consisting of normal saline, phosphate buffered saline, sterile water, aqueous dextrose solutions, aqueous glycerol solutions, ethanol, normal allantoic fluid, oil-in-water or water-in-oil emulsions, dimethyl sulfoxide, and mixtures thereof. 
     
     
         15 . A method of inducing an immune response against  Ehrlichia  infection in a subject, said method comprising administering an immunogenic composition according to  claim 1  to said subject. 
     
     
         16 . The method of  claim 15 , wherein said administering reduces the severity of symptoms of rickettsemia when the subject is exposed to  Ehrlichia.    
     
     
         17 . The method of  claim 15 , wherein said administering comprising injecting said vaccine composition intramuscularly, subcutaneously, intradermally, or intravenously using a needle and syringe, or a needleless injection device. 
     
     
         18 . The method of  claim 15 , wherein said vaccine composition is administered as a unit dosage form. 
     
     
         19 . The method of  claim 15 , wherein said subject is a non-human mammal. 
     
     
         20 . The method of  claim 15 , wherein said subject is a human. 
     
     
         21 . The method of  claim 15 , which said immune response in said subject is selected from the group consisting of pathogen-specific humoral immunity, production of pathogen-specific serum IgG, pathogen-specific cellular immunity, production of pathogen-specific IFNγ, and/or production of IL-17, after exposure to  Ehrlichia  infection. 
     
     
         22 . A kit for inducing an immune response against  Ehrlichia  infection in a subject, said kit comprising:
 an immunogenic composition according to  claim 1 ; and   instructions for administering said immunogenic composition to said subject.   
     
     
         23 . (canceled)