Expression of heterologous proteins

Abstract

An expression system which provides heterologous proteins expressed by a non-native host organism but which have native-protein-like biological activity and/or structure. Disclosed are vectors, expression hosts and methods for expressing the heterologous proteins. The expression system involves co-expression of protein factor(s) which is/are capable of catalyzing disulphide bond formation and desired heterologous protein(s). The expression system is presented using yeast cells as the preferred host, protein disulphide isomerase (PDI) and thioredoxin (TRX) as the preferred examples of the protein factors and HCV-E2 715 envelope glycoprotein and human FIGF as the preferred examples of the heterologous proteins.

1 . A vector comprising an expression cassette comprising a DNA sequence encoding a protein capable of catalyzing disulphide bond formation.  
     
     
         2 . A vector according to  claim 1 , wherein the protein capable of catalyzing disulphide bond formation is protein disulphide isomerase (PDI) or thioredoxin (TRX).  
     
     
         3 . A vector according to  claim 1  or  claim 2 , wherein the vector further comprises DNA sequencers) encoding one or more leader peptides for secretion.  
     
     
         4 . A vector according to any one of  claims 1  to  3 , wherein the vector further comprises an expression cassette comprising DNA sequence(s) encoding one or more heterologous proteins.  
     
     
         5 . A vector according to  claim 4 , wherein the heterologous protein is hepatitis C virus (HCV) E2 715  envelope glycoprotein or human c-fos-induced growth factor (FIGF).  
     
     
         6 . A vector according to any one of  claims 1  to  5 , wherein the vector is capable of integrating into the genome of a host organism.  
     
     
         7 . A host organism transformed with a vector according to any one of  claims 1  to  6 .  
     
     
         8 . A host organism according to  claim 7  further transformed with a vector comprising an expression cassette comprising DNA sequencers) encoding one or more heterologous proteins.  
     
     
         9 . A host organism according to  claim 8 , wherein the heterologous protein is hepatitis C virus (HCV) E2 715  envelope glycoprotein or human FIGF.  
     
     
         10 . A host organism according to any one of  claims 7  to  9 , wherein the host organism is a yeast.  
     
     
         11 . A method of producing a host organism according to  claim 7 , comprising transforming a host organism with a vector of any one of  claims 1  to  6 .  
     
     
         12 . A method of producing a host organism according to  claim 8 , comprising further transforming a host organism of  claim 7  either subsequently or simultaneously with a vector comprising an expression cassette comprising DNA sequence(s) encoding one or more heterologous proteins.  
     
     
         13 . A method of producing a host organism according to  claim 9 , comprising further transforming a host organism of  claim 7  either subsequently or simultaneously with a vector comprising an expression cassette comprising DNA sequence(s) encoding hepatitis C virus (HCV) E2 715  envelope glycoprotein or human FIGF.  
     
     
         14 . A method for expressing biologically active and/or correctly structured heterologous protein(s) in a host organism, comprising the steps of: 
 (a) transforming a host organism with one or more vectors according to any one of  claims 1  to  6 ;    (b) further transforming the host organism resulting from step (a) either subsequently or simultaneously with one or more vectors comprising DNA sequence(s) encoding one or more heterologous proteins; and    (c) culturing the host organism of step (b) in conditions suitable for expression of the one or more heterologous proteins.    
     
     
         15 . A method for expressing biologically active and/or correctly structured heterologous protein(s) in a host organism, comprising: 
 (a) transforming a host organism according to  claim 7  either subsequently or simultaneously with one or more vectors comprising DNA sequence(s) encoding one or more heterologous proteins; and    (b) culturing the host organism of step (a) in conditions suitable for expression of the one or more heterologous proteins.    
     
     
         16 . A method for expressing biologically active and/or correctly structured heterologous protein(s) in a host organism, comprising the step of culturing a host organism according to  claim 8  in conditions suitable for expression of the one or more heterologous proteins.  
     
     
         17 . A method according to any one of  claims 14  to  16 , wherein the heterologous protein is HCV-E2 715  envelope glycoprotein or human FIGF.  
     
     
         18 . A method for the preparation of an immunogenic composition, comprising bringing HCV-E2 715  envelope glycoprotein or human FIGF produced by the method of  claim 17  into association with a pharmaceutically carrier and optionally an adjuvant.