Hepatitis E virus antigens and uses therefor

Abstract

Antigens are provided which are derived from the enterically transmitted non-A/non-B viral hepatitis agent, known as hepatitis E virus (HEV). The HEV antigens and in particular, soluble species of the capsid protein encoded by the carboxy terminal region of HEV ORF2, are immunoreactive with sera from individuals infected with HEV. In one embodiment, these antigens may be produced by a baculovirus expression vector and form virus-like particles (VLPs). The antigens are useful as diagnostic reagents in diagnostic methods and kits for determining infection of an individual with HEV. The antigens are also useful in vaccine compositions effective in methods for preventing HEV infection.

It is claimed:  
     
         1 . A Hepatitis E Virus (HEV) polypeptide composition, consisting of at least one polypeptide derived from the carboxy-terminal 549 amino acids of HEV open reading frame (ORF) 2.  
     
     
         2 . A polypeptide composition of  claim 1 , where at least one polypeptide contains a carboxy terminal deletion of up to about 24 carboxy terminal amino acids of said 549 amino acid HEV ORF2 polypeptide.  
     
     
         3 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:15 or a homologous sequence thereto.  
     
     
         4 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:16 or a homologous sequence thereto.  
     
     
         5 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:25 or a homologous sequence thereto.  
     
     
         6 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:26 or a homologous sequence thereto.  
     
     
         7 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:27 or a homologous sequence thereto.  
     
     
         8 . A polypeptide composition of  claim 1 , where said composition contains a polypeptide having the sequence presented as SEQ ID NO:28 or a homologous sequence thereto.  
     
     
         9 . A polypeptide composition of  claim 1 , where said composition contains two polypeptides having the sequences presented as SEQ ID NO:25 and SEQ ID NO:27, or homologous sequences thereto.  
     
     
         10 . A polypeptide composition of  claim 1 , where said composition contains two polypeptides having the sequences presented as SEQ ID NO:26 and SEQ ID NO:28, or homologous sequences thereto.  
     
     
         11 . A substantially isolated nucleic acid sequence encoding a polypeptide derived from the carboxy-terminal 549 amino acids of HEV open reading frame 2.  
     
     
         12 . An expression vector for producing a Hepatitis E Virus polypeptide antigen composition, comprising, 
 a nucleic acid sequence encoding a polypeptide derived from the carboxy-terminal 549 amino acids of HEV open reading frame 2, said nucleic acid sequence inserted into an expression vector, where said nucleic acid sequence is operably linked to a promoter able to initiate transcription in a selected host cell.    
     
     
         13 . An expression system for producing a Hepatitis E Virus polypeptide antigen composition, comprising, 
 a nucleic acid sequence encoding a polypeptide derived from the carboxy-terminal 549 amino acids of HEV open reading frame 2, said nucleic acid sequence inserted into an expression vector, wherein said nucleic acid sequence is operably linked to a promoter able to initiate transcription in a selected host cell, and    said expression vector is carried within the host cell.    
     
     
         14 . An expression system of  claim 13 , where said expression vector is a baculovirus expression vector and said host cell is an insect cell.  
     
     
         15 . A Hepatitis E Virus (HEV) polypeptide composition produced by a process comprising, 
 culturing an insect cell containing an expression vector of  claim 11  under conditions sufficient to express a polypeptide encoded by said nucleic acid.    
     
     
         16 . A composition of  claim 15 , wherein at least one polypeptide of the composition has an amino acid sequence selected from the group consisting of SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, and homologous sequences therewith.  
     
     
         17 . A Hepatitis E Virus (HEV) polypeptide composition produced by a process comprising, 
 a) obtaining an HEV capsid derived antigen having at least 549 carboxy terminal amino acids of an HEV capsid protein; and    b) incubating the antigen with a baculoviral infected lysate under conditions sufficient to cleave carboxy terminal sequences of the HEV capsid derived antigen.    
     
     
         18 . A method of producing a Hepatitis E Virus (HEV) polypeptide composition, comprising the steps of: 
 culturing a cell containing the expression vector of  claim 11  under conditions sufficient to express a polypeptide sequence encoded by said nucleic acid.    
     
     
         19 . A method of detecting hepatitis E virus infection in an individual, comprising: 
 a) reacting a serum sample taken from the individual with the Hepatitis E Virus (HEV) polypeptide composition of  claim 1;  and    b) examining a polypeptide of the composition for the presence of bound antibody.    
     
     
         20 . The method of  claim 18 , wherein polypeptides of the HEV polypeptide composition are attached to a solid support, said reacting includes contacting such serum with the support and said examining includes reacting the support and bound antibody with a reporter-labeled anti-human antibody.  
     
     
         21 . A kit for ascertaining the presence of antibodies to HEV in a serum sample taken from an individual, comprising: 
 a solid support with surface-bound antigens wherein the surface-bound antigens are polypeptides of the HEV polypeptide composition of  claim 1 .    
     
     
         22 . A vaccine composition used in immunizing an individual against Hepatitis E Virus (HEV) comprising, 
 an HEV polypeptide composition of  claim 1  in a pharmacologically acceptable carrier.    
     
     
         23 . A vaccine composition of  claim 22 , where at least one polypeptide of the composition has an amino acid sequence selected from the group consisting of SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, and homologous sequences therewith.  
     
     
         24 . A method of inhibiting infection of an individual by HEV, comprising: 
 administering to the subject a vaccine composition of  claim 22  in a therapeutically effective amount.