Recombinant Bacterium and Uses Thereof

Abstract

The present invention relates to a recombinant bacterium expressing an antigen that is translocated to the cytosol of a host organism, and uses thereof. To this end, the present invention provides a recombinant bacterium comprising a nucleic acid encoding an antigen that is translocated to the cytosol of a host cell utilizing Type III secretion system. The recombinant bacterium is generally chosen from intracellular pathogens that reside in the phagosome and fail to induce rapid T cell activation. The translocated antigen may be a viral antigen, a bacterial antigen, or a tumour antigen. Methods of imparting immunity using the recombinant bacterium are also provided.

1 . A recombinant bacterium, comprising a nucleic acid encoding an antigen that is translocated to the cytosol of a host cell. 
     
     
         2 . The recombinant bacterium of  claim 1 , wherein the bacterium is an intracellular bacterium such as  Salmonella, Mycobacteria, Brucella,  or  Leishmania.    
     
     
         3 . The recombinant bacterium of  claim 1 , wherein the bacterium is  Salmonella.    
     
     
         4 . The recombinant bacterium of  claim 1 , wherein the antigen is a viral antigen, a bacterial antigen, or a tumour antigen. 
     
     
         5 . The recombinant bacterium of  claim 1 , wherein the antigen is a fusion protein comprising an antigen and a translocation domain from a type III secretion system. 
     
     
         6 . The recombinant bacterium of  claim 5 , wherein the translocation protein is YopE, SopE, SptP, or a fragment thereof. 
     
     
         7 . The recombinant bacterium of  claim 5 , wherein the fusion protein further comprises a chaperone. 
     
     
         8 . The recombinant bacterium of  claim 7 , wherein the chaperone is derived from type Ill secretion systems. 
     
     
         9 . The recombinant bacterium of  claims 8 , wherein the chaperone is SycE or HSP70. 
     
     
         10 . The recombinant bacterium of  claim 1 , wherein the nucleic acid is comprised in a vector. 
     
     
         11 . The recombinant bacterium of  claim 10 , wherein the vector is a pHR vector. 
     
     
         12 . The recombinant bacterium of  claim 10 , wherein the vector is pHR-241. 
     
     
         13 . The recombinant bacterium of  claim 1 , wherein the antigen is tyrosinase related protein 2 (TRP-2), MART-1, melanoma associated antigen 1 (MAGE1), or Her-2/neu, gp100, or other viral or bacterial antigens. 
     
     
         14 . A method of imparting immunity against naturally-occurring bacterium or virus in a subject, the method comprising administering the recombinant bacterium of  claim 1  to said subject. 
     
     
         15 . A method of imparting immunity against tumors in a subject, the method comprising administering the recombinant bacterium of  claim 13  to said subject. 
     
     
         16 . The method of  claim 14 , wherein the recombinant bacterium is administered through intravenous, oral or subcutaneous routes of immunization. 
     
     
         17 . The use of the recombinant bacterium of  claim 1  as a vaccine. 
     
     
         18 . The method of  claim 15 , wherein the recombinant bacterium is administered through intravenous, oral or subcutaneous routes of immunization.