IMMUNOGENIC COMPOSITION OF HEPATITIS C AND METHODS OF USE THEREOF

Abstract: The present invention provides truncated HCV E2 polypepides. The invention HCV E2 polypeptides lack the HVR1 region that provides immune protection against HCV. The present invention also provides immunogenic compositions of such polypeptides and the methods of use thereof.

Description: IMMUNOGENIC COMPOSITION OF HEPATITIS C AND METHODS OF USE THEREOF FIELD OF THE INVENTION This invention relates generally to the field of viral proteins and more specifically to variants of hepatitis C having truncated E2 proteins. BACKGROUND OF THE INVENTION Hepatitis C Virus (HCV), the etiological agent of post-transfusion and community-acquired non-A, non-B hepatitis is responsible for approximately 20% of all cases of acute hepatitis, 70% of chronic hepatitis and 30% of end-stage liver disease in the United States (Hoofiiagle, J. H., Hepatology 26:15S-20S (1997)). Of those chronically infected individuals, 15-30% will develop cirrhosis and 10-30% of these patients will progress to hepatocellular carcinoma and end-stage liver disease. No vaccine is currently available to prevent the disease and treatment options are limited. Development of a safe and efficacious vaccine is hampered by the lack of "correlates of protective immunity", the inability to propagate the virus in cμlture, and the absence of a small animal model. Based on its genome structure, hepatitis C virus, has been placed in the family Flaviviridae as a separate genus Hepacivirus. The HCV genome is a single positive- stranded RNA of approximately 9,500 nucleotides containing short 5 1 and 3' untranslated regions, and a single long open reading frame. The polyprotein is organized in the order, C (core or nucleocapsid), El (envelopel), E2 (E2/NS1, envelope2), P7 (small protein of unknown function), NS2 (nonstructural), NS3, NS4A, NS4B, NS5A, and NS5B. The mature viral proteins are processed from the polyprotein by co- and post-translational proteolytic cleavage by either viral or host cell proteases. Phylogenic analysis has identified six distinct HCV genotypes (clades) and multiple minor genetic groups. Infection and recovery from disease caused by one virus genotype does not protect from reinfection by homologous or heterologous virus. Infection and recovery, therefore, does not induce protective immunity. Vaccine development has focused on two viral structural proteins, El and E2 (e.g. US Patent Nos. 5,942,234; 6,121,020; and 6,150,134). One region of the E2 protein, localized to the N-terminal 30 amino acids (hypervariable region 1 [HVRl]) has been found to be the most heterogeneous region among different virus isolates. Patients with high titer anti-HVRl antibodies are known to clear the virus, suggesting that there is at least 1 protective epitope within this region, but also suggesting that this region is under direct selective pressure. Anti-HVRl antibodies are sequence specific, and, therefore, offer no protection from heterologous challenge. The HCV E2 protein has been shown to bind to the major extracellular loop of CD81 , a 25-kDa molecule belonging to the tetraspanin family. The presence of antibodies which inhibit binding to CD 81 have been correlated with protection from disease. Epitope mapping studies have suggested that multiple sites within the glycoprotein are responsible for this binding. One epitope lies within the HVRl, while it is clear that a number of others lie outside the HVRl. Monoclonal antibodies isolated from a chronically infected HCV patient were able to inhibit the binding of HCV E2 genotype la, lb, 2a, and 2b recombinant proteins to CD81. These epitopes must lie outside the HVRl and, therefore, are more conserved across HCV genotypes. The viral genomic sequence of HCV is known, as are methods for obtaining the sequence. See, e.g., International Publication Nos. WO 89/04669; WO 90/11089; and WO 90/14436. In particular, HCV has a 9.5 kb positive-sense, single-stranded RNA genome and is a member of the Flaviridae family of viruses. Currently, there are 6 distinct, but related genotypes of HCV based on phylogenetic analyses (Simmonds et al., J. Gen. Virol. (1993) 74:2391-2399). The virus encodes a single polyprotein having more than 3000 amino acid residues (Choo et al., Science (1989) 244:359-362; Choo et al., Proc. Natl. Acad. Sci. USA (1991) 88:2451-2455; Han et al., Proc. Natl. Acad. Sci. USA (1991) 88:1711-1715). The polyprotein is processed co- and post- translationally into both structural and non-structural (NS) proteins. In particular, there are three putative structural proteins, consisting of the N- terminal nucleocapsid protein (termed "core") and two envelope glycoproteins, "El " (also known as E) and "E2" (also known as E2/NS1). (See, Houghton et al., Hepatology (1991) 14:381-388, for a discussion of HCV proteins, including El and E2.) El is detected as a 32-35 kDa species and is converted into a single endo H- sensitive band of approximately 18 kDa. By contrast, E2 displays a complex pattern upon immunoprecipitation consistent with the generation of multiple species. The HCV envelope glycoproteins El and E2 form a stable complex that is co- immunoprecipitable. The HCV El and E2 glycoproteins are of considerable interest because they have been shown to be protective in primate studies. The envelope of the HCV virion remains uncharacterized. Thus, expression studies using recombinant cDNA templates are the only means currently available to study envelope biosynthesis. El and E2 are retained within cells and lack complex carbohydrate when expressed stably or in a transient Vaccinia virus system. Since the El and E2 proteins are normally membrane-bound in these expression systems, it would be desirable to produce secreted forms to facilitate purification of the proteins for further use and to produce variants that are antigenic and induce a protective immune response. SUMMARY OF THE INVENTION The present invention is based on the seminal discovery that epitopes outside of HVRl region of HCV E2 protein are sufficient to induce immune response to HCV and provide immune protection against HCV. The invention provides a recombinant cell system that allows the production of recombinant N- and C-terminally truncated Hepatitis C Virus E2 protein in insect cells. Purification of this extracellularly secreted recombinant protein is described herein. Utilization of this recombinant protein for production of an immunogenic response in vivo to purified E2 protein is also provided herein. In a first embodiment, the invention provides a secreted polypeptide which is a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, and further comprising a deletion in at least a portion of its N-terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). In a preferred aspect, the secreted polypeptide is a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, wherein said E2 polypeptide lacks at least a portion of its C-terminus beginning at about amino acid residue 662 and at least a portion of its N- terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). The invention also provides polynucleotides encoding the polypeptides of the invention. An exemplary polynucleotide is set forth in SEQ ID NO:l. The invention also provides antibodies that specifically bind to a secreted polypeptide which is a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, and further comprising a deletion in at least a portion of its N-terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). An exemplary polypeptide is set forth in SEQ ID NO:8. In another embodiment, the invention provides a method for preparing an immunogenic composition for treatment of HCV. The method includes (a) forming an immunogenic polypeptide composition comprising a polypeptide of the invention, wherein the immunogenic polypeptide composition is suitable for treating HCV; (b) providing a suitable excipient; and (c) mixing the immunogenic composition of (a) with the excipient of (b). The invention also includes a method of producing anti-HCV antibodies comprising admimstering to a mammal an effective amount of an immunogenic polypeptide composition comprising a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, and further comprising a deletion in at least a portion of its N-terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). In one embodiment, the present invention provides an immunogenic polypeptide. The immunogenic polypeptide contains an amino acid sequence wherein the amino acid sequence encodes an HCV E2 polypeptide and is not adjacent to an HCV amino acid sequence naturally adjacent to the HCV E2 polypeptide, wherein the HCV E2 polypeptide does not contain hypervariable region 1 of HCV E2 protein and wherein the immunogenic polypeptide provides immune protection against HCV. In another embodiment, the present invention provides a method of treating HCV infection. The method comprises administering to a subject having or at risk of having HCV (e.g., a recipient of a blood transfusion or a hospital worker), an effective amount of the immunogenic polypeptide of the present invention or the composition thereof. In still another embodiment, the present invention provides a method of making an HCV E2 immunogenic polypeptide. The method comprises expressing a polynucleotide sequence encoding the HCV E2 immunogenic polypeptide in an insect cell line. The invention also provides a method of detecting the presence of HCV in a sample comprising contacting the sample with an antibody of the invention and detecting binding of the antibody to the polypeptide, wherein formation of a complex between the antibody and the E2 polypeptide is indicative of the presence of HCV in the sample. Preferably, the antibody is detectably labeled. BRIEF DESCRIPTION OF THE FIGURES Figures 1A, IB, and 1C show the analysis of expressed ΔE2 and ΔΔE2 in culture medium. Culture medium from stable S2 cell lines transfected with p78mttHCVE2ΔN (genotype la), ρ78mttHCVE2ΔNΔC (genotype la), p85mttHCVlbE2ΔC (genotype lb), or p85mttHCVlbH2ΔNΔC were induced with 200 μM of CuSO 4 . Cells were pelleted by centrifugation, and the media filtered to remove all traces of cells and debries. Ten microliters of filtered medium was loaded onto an SDS-polyacrylamide gel and the proteins separated by electrophoresis. One gel was stained with Coomassie Brilliant Blue and a second gel electrotransferred to nitrocellulose and probed with monoclonal antibodies Al 1 and 119. Figure 1 A shows Coomassie Brilliant Blue stain gel of genotype la recombinant proteins. Figure IB shows companion Western Blot of genotype la recombinant proteins. Figure 1C shows Western blot of genotype lb recombinant proteins. Figures 2 A and 2B show the glycosylation status of recombinant ΔE2 and ΔΔE2 proteins expressed in Drosophila S2 cells. Culture medium from S2 cell lines transfected with plasmids described in Figure 1 were induced with CuSO and harvested after 7 days growth. Media proteins were denatured with SDS and treated with EndoHf (E), or PNGaseF (P), or no enzyme (-). The samples were loaded onto an SDS polyacrylamide gel and separated via electrophoresis. The gel was electrotransferred onto nitrocellulose and probed with monoclonal antibodies Al 1 and 119. Figure 2A shows the glycosylation status of recombinant proteins from culture medium from two different cell lines expressing ΔE2 and ΔΔE2 protein, treated with or without PNGaseF. Figure 2B shows the glycosylation status of recombinant protein from culture medium from a single cell line expressing ΔE2 protein treated with or without EndoH f or PNGaseF. Figures 3 A and 3B show the analysis of ΔΔE2 protein and purification. Figure 3A shows silver stained SDS-PAGE. Figure 3B shows companion Western Blot probed with anti-E2 antibodies Al 1 and 119. All lanes represent 1 μg total protein/well. Lane 1 : Culture medium; lane 2: proteins eluted from the Phenyl Sepharose column; lane 3: proteins eluted from the Galanthus Nivalis lectin column; lane 4: pooled fractions containing ΔΔE2 protein from the sepharcryl 100 column. Figure 4 shows antigen-specific T-cells are induced in mice immunized with mixtures of antigen and different adjuvants. Balb/c mice were immunized with formulations containing 10 μg of antigen and different adjuvants as indicated in the figure (see Example 7). Splenocytes of vaccinated mice were restimulated in vitro in the presence of purified S2 derived ΔΔE2 protein or baculovirus derived protein as indicated. Cell proliferation was assessed by measureing [ 3 H]thymidine incorporation. Antigen-specific cell proliferation is expressed by stimulation indices calculated from the incorporated radioactivity in the presence of antigen minus medium blank, divided by the activity incorporated in cells cultured in medium only minus medium blank. Data represents the arithmetic mean of quadruplicate determinations. Figure 5 shows anti-E2 specific antibodies were induced by immunization with antigen/QS21 adjuvant combination. Anti-E2 antibody response of animals immunized with ΔΔE2 /QS-21 or control animals immunized without antigen to wells coated with E2 isolated from Drosophila S2 cells (S2 E2) or commercially available Baculovirus expressed E2 (Bac E2). Balb/c mice were immunized twice with vaccine containing 10 μg of antigen mixed with different adjuvants (see Example 7). Twelve days following the second immunization the animals were sacrificed and blood collected. The pooled sera were evaluated for anti-E2 antibodies in an indirect ELISA. Figure 6 is the cDNA and corresponding amino acid sequence of ΔΔE2 genotype la. Yanagi et al, 1997, PNAS 94:8738 describe the cloning of the full length infectious clone of HCV and the accession numbers listed are GenBank AF011751-AFOl 1753 (herein incorporated by reference in their entirety) (see also SEQ ID NO:9 for a representative amino acid sequence). These are three full-length clones that a consensus sequence for H77 was derived. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates in general to immunogenic polypeptides of HCV E2 protein. The invention is based on the discovery that epitopes outside of hypervariable region are sufficient to induce immune response to HCV and provide immune protection against HCV, e.g., multiple HCV genotypes. By an "E2 polypeptide" is meant a molecule derived from an HCV E2 region. Such a molecule can be physically derived from the region or produced recombinantly or synthetically, based on the known sequence. The mature E2 region of HCV is believed to begin at approximately amino acid 384-385, and end approximately at amino acid 747. The mature E2 protein contains a C-terminal membrane anchor at approximately amino acids 715-730. Further, the mature E2 protein contains a hydrophobic tail region which inhibits efficient folding and secretion of C-terminally truncated recombinant proteins from mammalian cells. By an "N- and C-terminally truncated E2 polypeptide" is meant a recombinant protein in which N-terminal HVRl sequences spanning the first 25-30 amino acids and the C-terminal 86 amino acids. Research has demonstrated that recombinant HCV E2 polypeptides devoid of its membrane anchor and hydrophobic tail regions can be secreted into the medium (deletions through amino acids 688, 704 and 715), but that these proteins are incorrectly folded by virtue of recognition by conformationally sensitive monoclonal antibody H2 (Michalak et al. 1997). Furthermore, recombinant E2 ending at 715 was secreted into the medium, but this protein was not recognized by monoclonal antibody H2 and was found in large aggregrates. Expression of a recombinant E2 protein ending in amino acid 664 was efficiently secreted by CHO cells (Lesniewski et al. 1995). The present invention provides a method to effectively and efficiently produce recombinant HCV E2 proteins for prophylactic and therapeutic purposes. The present applicants have found that recombinantly-engineered amino- and carboxy terminally truncated HCV envelope protein 2, corresponding to amino acids 412-661, is efficiently secreted by an insect cell host, in a form that permits processing to mimic the native conformation of the protein. The efficient secretion of the proteins into the culture medium facilitates purification. Furthermore, the high level of expression permits facile purification of the monomers. In addition, the secreted form is able, especially when administered in the presence of certain modern adjuvants to elicit antibodies and stimulate the production of cytokines from splenocytes of immunized animals. Thus, this protein represents a useful component of a vaccine for protecting subjects against HCV infection. Truncated E2 protein has been produced using a variety of expression systems including E. coli (Mita et al. 1992), Spodoptera frugiperda (Chien et al. 1992, Matsuura et al. 1992, Lanford et al. 1993, Nishihara et al. 1993), Chinese Hamster Ovary (CHO e.g. U.S. Patent 5,854,001; Spaete et al. 1992, Harada et al. 1995, Lesniewski et al. 1995, friudoh et al. 1996), vaccinia (e.g. U.S. Patent 6,245,503) and Sindbis (Ralston et al. 1993, Dubuisson and Rice 1996, Deleersnyder et al. 1997, Michalak et al. 1997). While the expression level of truncated protein has not been reported in most of the above references, expression levels of 6- 10 mg/L in CHO cell line has been reported (Lesniewski et al. 1995; Lee et al., 1997). The truncated E2 protein forms multimeric aggregates, and only the monomer appears to be folded correctly and capable of eliciting antibodies which inhibit E2 binding to CD81 (Heile et al. 2000). However, the monomeric fraction represents a minority of the expressed protein. The level of expression of the monomer in this invention is 20-50 mg/L. This level far exceeds that reported for total E2 protein found in the media. This invention, thus, not only seeks to describe a system for the efficient expression of protein, but also an efficient method to purify the monomer. However, efficient expression and secretion into the media alone does not constitute a viable vaccine; the protein must have native conformation. Traditionally, native conformation was measured by the reactivity of the recombinant protein to patient sera under native (e.g. ELISA) and non-native (Western blot of reduced and denatured recombinant protein). No documentation of the present invention exists in the literature, and, therefore, it was unknown whether it would be recognized by patient serum. Of 43 patient sera evaluated using an ELISA format, 35 recognized the unpurified, recombinant N- and C-terminally truncated HCV E2 protein substantiating that the polypeptide had native conformation. In the same assay, a commercially available recombinant E2 polypeptide was recognized by only two patient sera. However, due to the polyclonal nature of serum, a better judge of native conformation is recognition by conformationally sensitive monoclonal antibodies. Again, the truncated E2 protein described in this invention was recognized by a set of conformationally sensitive monoclonal antibodies, while, the commercial E2 protein was not. The commercial E2 protein was only recognized by conformationally insensitive monoclonal antibodies; these monoclonal antibodies were isolated from ammals immimized with reduced and denatured E2 protein (Dubuisson et al. 1994). These two experiments confirm the authenticity of the invention. Hydrophobicity plots of highly divergent HVRl sequences are similar and detailed sequence analysis of the region indicates that folding of the HVRl may be constrained. However, in the context of an infectious cDNA clone, deletion of HVRl sequences is not lethal, and animals infected with this infectious clone succumb to illness (Forns et al. 2000b). Thus, within virus replication, maturation, and infection, HVRl sequences are unnecessary if the entire genome is expressed. In addition, expression of a membrane anchored HCV E2 protein devoid of HVRl sequences is recognized by conformationally sensitive monoclonal antibodies and binds CD81 (Forns et al. 2000a). However, neither of these references teach whether expression of the isolated, secreted E2 protein will result in a correctly folded protein, nor the level of expression within the cell, nor whether the protein will be secreted into the media, nor its stability within culture media. The uniqueness of the invention is due, in part, to its expression in the Drosophila S2 cell line (U.S. Patent 5,550,043; 5,681,713; 5,705,359; 6,046,025). The invention embodied herein makes use of the Drosophila S2 system to produce recombinant HCV N- and C-terminally truncated E2 polypeptide. Despite the fact that an expression system may be reported to be effective for production of one recombinant protein, predictions on efficacy of expression of other recombinant products do not always hold, and, therefore, requires careful evaluation. For example, although the baculovirus expression system has been reported to yield high levels of correctly folded protein, expression of HIV gpl20 resulted limited amounts of ill- folded protein (Moore et al. 1990, Murphy et al. 1993), whereas, expression of the same protein in Drosophila S2 cell line resulted in large amounts of well-folded protein (Ivey-Hoyle et al. 1991). Expression of dengue virus envelope protein in Drosophila S2 cell line, again, produced a protein of higher quality as judged by its ability to elicit a potent neutralizing antibody titers, than that produced in the baculovirus expression system (U.S. patent 6,136,561). Expression of HCV E2 protein in Chinese Hamster Ovary cell line (CHO) but not E2 expressed in yeast or the baculovirus system bound CD81 (Rosa et al. 1996), but dengue envelope protein expressed in CHO cell line was poorly secreted and poorly antigenic compared with that expressed in Drosophila S2 cell line. Accordingly, the present invention provides immunogenic polypeptides of truncated HCV E2 protein. In one embodiment, the immunogenic polypeptide of the present invention contains an amino acid sequence encoding an HCV E2 polypeptide that does not contain hypervariable region 1 (HVRl). The amino acid sequence encoding the HCV E2 polypeptide of the immunogenic polypeptide of the present invention is not surrounded by or adjacent to an amino acid sequence that naturally surrounds or adjacent to it in HCV. According to another embodiment of the present invention, the immunogenic polypeptide of the present invention contains an HCV E2 polypeptide with both N- terminal and C-terminal truncations of HCV E2 protein, e.g., does not contain the HVRl region and the C-terminal region of HCV E2 protein. The mature HCV E2 protein contains a C-terminal membrane spanning region starting from about amino acid 718 and ending at about amino acid 746. The HCV C-terminal hydrophobic tail region in general is from about amino acid 663 to about amino acid 746. A mature E2 protein is encoded by HCV amino acid sequence starting from about amino acid 384 and ending at about amino acid 746. Hypervariable region 1 (HVRl) is at the N-terminal of HCV E2 protein and is highly variable among HCV isolates. Usually HVRl contains epitopes that are specific to HCV isolates and induce neutralizing antibodies that are epitope specific, thus provide little protection from infection by HCV of a different HVRl sequence. In one aspect, the HVRl region includes the N-terminal amino acids of HCV E2 protein, e.g., from about 384 to 411 amino acids of HCV E2 protein. It should be understood that one of skill in the art could remove a single or multiple amino acid residues as long as the functional features of the polypeptide of the invention are retained, i.e., secreted when produced recombinantly in host cells and immunogenic stimulating a protective immune response in a subject. In one aspect, the invention truncated E2 polypeptide includes C-terminal amino acids that deletion of which enables the truncated E2 polypeptide to be secreted outside of cell and recognizable by conformation sensitive monoclonal antibody, e.g., H2. In a particular illustrative example, the immunogenic polypeptide of the present invention contains an HCV E2 polypetide having an amino acid sequence as shown in SEQ ID NO:8. For purposes of the present invention, the El and E2 regions are defined with respect to the amino acid number of the polyprotein encoded by the genome of HCV1, with the initiator methionine being designated position 1. However, it should be noted that the term an an "E2 polypeptide" as used herein is not limited to the HCV1 sequence. In this regard, the corresponding E2 regions in another HCV isolate can be readily determined by aligning sequences from the two isolates in a manner that brings the sequences into maximum alignment. This can be performed with any of a number of computer software packages, such as ALIGN 1.0, available from the University of Virginia, Department of Biochemistry (Attn: Dr. William R. Pearson). See, Pearson et al., Proc. Natl. Acad. Sci. USA (1988) 85:2444-2448. Furthermore, an "E2 polypeptide" as defined herein is not limited to a polypeptide having the exact sequence depicted in the Figures or Sequence Listing. Indeed, the HCV genome is in a state of constant flux and contains several variable domains which exhibit relatively high degrees of variability between isolates. As will become evident herein, all that is important is that the region which serves to anchor the polypeptide to the endoplasmic reticulum be identified such that the polypeptide can be modified to remove all or part of this sequence for secretion. It is readily apparent that the terms encompass E2 polypeptides from any of the various HCV isolates including isolates having any of the genotypes of HCV described in Simmonds et al., J. Gen. Virol. (1993) 74:2391-2399). Furthermore, the term encompasses any such E2 protein regardless of the method of production, including those proteins recombinantly and synthetically produced. Additionally, the term "E2 polypeptide" or "truncated E2 polypeptide" encompasses proteins which include additional modifications to the native sequence, such as additional internal deletions, additions and substitutions (generally conservative in nature). These modifications may be deliberate, as through site- directed mutagenesis, or may be accidental, such as through naturally occurring mutational events. All of these modifications are encompassed in the present invention so long as the modified E2 polypeptides function for their intended purpose. Thus, for example, if the E2 polypeptides are to be used in vaccine compositions, the modifications must be such that immunological activity (i.e., the ability to elicit an antibody response to the polypeptide) is not lost. Similarly, if the polypeptides are to be used for diagnostic purposes, such capability must be retained. An E2 polypeptide "lacking all or a portion of its membrane spanning domain" is an E2 polypeptide, which has been C-terminally truncated to delete all or a part of the membrane anchor sequence which functions to associate the polypeptide to the endoplasmic reticulum. Such a polypeptide is therefore capable of secretion into growth medium in which an organism expressing the protein is cultured. The truncated polypeptide need only lack as much of the membrane anchor sequence as necessary in order to effect secretion. Secretion into growth media is readily determined using a number of detection techniques, including, e.g., polyacrylamide gel electrophoresis and the like and immunological techniques such as immunoprecipitation assays as described in the examples. Furthermore, the C-terminal truncation can extend beyond the transmembrane spanning domain towards the N-terminus. Thus, for example, E2 truncations occurring at positions lower than, e.g., 411 are also encompassed by the present invention. All that is necessary is that the truncated E2 polypeptides be secreted and remain functional for their intended purpose. However, particularly preferred E2 constructs will be those with C-terminal truncations that do not extend beyond amino acid position 661 and N-terminal truncations that do not extend beyond 411. A "secreted E2 polypeptide" refers to a truncated E2 protein lacking all or a portion of the membrane spanning domain, as described above. Two polynucleotides or protein molecules are "substantially homologous" when at least about 40-50%, preferably at least about 70-80%, and most preferably at least about 85-95%, of the nucleotides or amino acids from the molecules match over a defined length of the molecule. As used herein, substantially homologous also refers to molecules having sequences which show identity to the specified nucleic acid or protein molecule. Nucleic acid molecules that are substantially homologous can be identified in a Southern hybridization experiment under, for example, stringent conditions, as defined for that particular system. Defining appropriate hybridization conditions is within the skill of the art. See, e.g., Sambrook et al., supra; DNA Cloning, vols I & II, supra; Nucleic Acid Hybridization, supra. An "isolated" protein or polypeptide is a protein which is separate and discrete from a whole organism with which the protein is normally associated in nature. Thus, a protein contained in a cell free extract would constitute an "isolated" protein, as would a protein synthetically or recombinantly produced. Likewise, an "isolated" polynucleotide is a nucleic acid molecule separate and discrete from the whole organism with which the sequence is found in nature; or a sequence devoid, in whole or part, of sequences normally associated with it in nature; or a sequence, as it exists in nature, but having heterologous sequences in association therewith. A "coding sequence" or a sequence which "encodes" a selected protein, is a nucleic acid sequence which is transcribed (in the case of DNA) and translated (in the case of mRNA) into a polypeptide in vitro or in vivo when placed under the control of appropriate regulatory sequences. The boundaries of the coding sequence are determined by a start codon at the 5' (amino) terminus and a translation stop codon at the 3' (carboxy) terminus. A coding sequence can include, but is not limited to cDNA from viral nucleotide sequences as well as synthetic DNA sequences. A transcription termination sequence may be located 3' to the coding sequence. A "polynucleotide" can include, but is not limited to, viral sequences, procaryotic sequences, viral RNA, eucaryotic mRNA, cDNA from eucaryotic mRNA, genomic DNA sequences from eucaryotic (e.g., mammalian) DNA, and even synthetic DNA sequences. "Recombinant" as used herein to describe a nucleic acid molecule means a polynucleotide of genomic, cDNA, semisynthetic, or synthetic origin which, by virtue of its origin or manipulation: (1) is not associated with all or a portion of the polynucleotide with which it is associated in nature; and/or (2) is linked to a polynucleotide other than that to which it is linked in nature. The term "recombinant" as used with respect to a protein or polypeptide means a polypeptide produced by expression of a recombinant polynucleotide. Recombinant host cells," "host cells," "cells," "cell lines," "cell cultures," and other such terms denoting procaryotic microorganisms or eucaryotic cell lines cultured as unicellular entities, are used interchangeably, and refer to cells which can be, or have been, used as recipients for recombinant vectors or other transfer DNA, and include the progeny of the original cell which has been transfected. It is understood that the progeny of a single parental cell may not necessarily be completely identical in morphology or in genomic or total DNA complement to the original parent, due to accidental or deliberate mutation. Progeny of the parental cell which are sufficiently similar to the parent to be characterized by the relevant property, such as the presence of a nucleotide sequence encoding a desired peptide, are included in the progeny intended by this definition, and are covered by the above terms. The term "subject" as used herein refers to any subject capable of being infected by HCV. Preferably, the subject of the invention is a human. However, as used herein, the term is meant to include humans and other primates, including non- human primates such as chimpanzees and other apes and monkey species; farm animals such as cattle, sheep, pigs, goats and horses; domestic mammals such as dogs and cats; laboratory animals including rodents such as mice, rats and guinea pigs; birds, including domestic, wild and game birds such as chickens, turkeys and other gallinaceous birds, ducks, geese, and the like. The term does not denote a particular age. Thus, both adult and newborn individuals are intended to be covered. According to the present invention, the immunogenic polypeptide of the present invention provides immune protection against HCV. The immune protection against HCV provided by the immunogenic polypeptide can be any immune response, cellular or humoral, that either inhibits or helps to prevent HCV infection. For example, the immunogenic polypeptide of the present invention can bind to CD81, induce antibodies associated with resolving HCV infection, induce production of cytokines, induce antibodies that can neutralize HCV binding to host cells, or prime an immune system against secondary HCV infection or exposure. The immune protection provided by the immunogenic polypeptide of the present invention is preferably protective against more than one HCV genotypes. The immunogenic polypeptide of the present invention can be a recombinant polypeptide or a synthetic polypeptide. In one embodiment, the immunogenic polypeptide is made in an expression system that preserves or mimics the native conformation of the HCV E2 protein, e.g., recognizable by HCV patient sera under native condition or by conformation sensitive monoclonal antibody. For example, the immunigenic polypeptide of the present invention can be made in a mammalian cell line or an insect cell line, including without limitation, Drosophila S2 cell line. In another embodiment, the immunogenic polypeptide of the present invention is a monomer, e.g., with monomeric expression at a level of 20-50 mg/1. In still another embodiment, the immunogenic polypeptide of the present invention is glycosylated, e.g., at a level similar to the glycosylation obtained in Drosophila S2 cell line. The present invention also provides an immunogenic composition containing the immunogenic polypeptide of the present invention and an excipient. The compositions of the present invention are useful for treating HCV infection, e.g., by inducing production of neutralizing antibodies. For therapeutic treatment of HCV infection, the compositions of the present invention can be administered alone or in a composition with a suitable pharmaceutical carrier, e.g., water, saline, glycerol, ethanol, etc. The compositions of the present invention can also be administered in combination with other therapeutic agents including, without limitation, immunoregulatory agents, immunoglobulin, cytokines, lymphokines, and chemokines, e.g., IL-2, modified IL-2 (changing cysl25 to serl25), GM-CSF, IL-12, gamma-interferon, IP-10, MlPlβ, or RANTES. An effective amount of the compositions to be administered can be determined on a case-by-case basis. Factors should be considered usually include age, body weight, stage of the condition, other disease conditions, duration of the treatment, and the response to the initial treatment. In one embodiment, an effective amount includes an amount of the composition of the present invention that induces an immunological response as measured by 1) the production of antibodies from any of the immunological classes, e.g., immunoglobulins A, D, E, G, or M, 2) the proliferation of B and T lymphocytes, 3) the provision of activation, growth, and differentiation signals to immunological cells, and 4) the expansion of helper T cell, suppressor T cells, and/or cytotoxic T cell and/or gamma-delta-T cell populations. Typically, the compositions are prepared as an injectable, either as a liquid solution or suspension. However, solid forms suitable for solution in, or suspension in, liquid vehicles prior to injection can also be prepared. The composition can also be formulated into an enteric-coated tablet or gel capsule according to known methods in the art. The compositions of the present invention may be administered in any way which is medically acceptable which may depend on the disease condition or injury being treated. Possible administration routes include injections, by parenteral routes such as intravascular, intravenous, intraepidural or others, as well as oral, nasal, ophthalmic, rectal, topical, or pulmonary, e.g., by inhalation. The compositions may also be directly applied to tissue surfaces, e.g., during surgery. Sustained release administration is also specifically included in the invention, by such means as depot injections or erodible implants. According to another feature of the present invention, the immunogenic polypeptide of the present invention can be used as a vaccine to provide immune protection against subsequent HCV infection or exposure. The present invention provides an immunogenic composition or a vaccine comprising the immunogenic polypeptide of the present invention and an adjuvant. The immunogenic polypeptide of the present invention can be with any suitable adjuvant for stimulating immune response, e.g., providing immune protection. For example, it can be a particulate or a non-particulate adjuvant. A particulate adjuvant usually includes, without limitation, aluminum salts, calcium salts, water-in-oil emulsions, oil-in water emulsion, immune stimulating complexes (ISCOMS) and ISCOM matrices (U.S. patent 5,679,354), liposomes, nano-and microparticles, proteosomes, virosomes, stearyl tyrosine, and (-friulin. A non- particulate adjuvant usually includes, without limitation, muramyl dipeptide (MDP) and derivatives, e.g., treonyl MDP or murametide, non-ionic block copolymers, saponins, e.g., Quil A and QS21, lipid A or its derivative 4' monophosphoryl lipid A (MPL), trehalose dimycolate (TDM), various cytokines including (-interferon and interleukins 2 or 4, carbohydrate polymers, derivatized polysaccharides, e.g., diethylaminoeytyl dextran, and bacterial toxins, e.g., cholera toxin or E. coli labil toxin. In one embodiment, the immunogenic polypeptide of the present invention is used with adjuvant QS-21. The immunogenic polypeptides of the present invention can also be used with adjuvant formulations that are combinations of various components designed to maximize specific immune responses. For example, in U.S. patent 6,146,632, the combination of QS21 , 3-De-O-acylated monophysphoryl lipid A alpha tocopherol, TWEEN 80, and water adjuvant was shown to be the most effective in mediating humoral and cell immunity. In one embodiment, the immunogenic polypeptide of the present invention is used with other HCV proteins to form a multi-component HCV vaccine for prophylactic or therapeutic treatment of HCV infection. In another embodiment, the vaccine of the present invention is combined with other vaccines including, without limitation other modes of HCV vaccines, e.g., plasmid DNA. The present invention provides immunoassays for detecting the presence of HCV in a sample containing, or suspected of containing HCV. The immunoassays of the mvention can be "sandwich" assays, wherein a second antibody is used to detect specific binding of a first antibody and HCV polypeptides (e.g., SEQ ID NO:8) or can be competition assays, wherein binding of a competitor HCV polypeptide by the "first" antibody is indicative of the presence of HCV in a sample. For example, sera from a subject suspected of containing anti-HCV antibodies can be contacted with a polypeptide of the invention and formation of a complex can be identified, indicating that the subject has been infected with HCV. The term "antibody" is used broadly herein to include polyclonal and monoclonal antibodies, as well as antigen binding fragments of such antibodies. Depending on the particular method of the invention, antibodies having various specificities can be useful, including an antibody, or antigen binding fragment thereof, that specifically binds a polypeptide of the invention (e.g., SEQ ID NO:8). The term "specifically binds" or "specifically interacts," when used in reference to an antibody means that an interaction of the antibody and a particular epitope has a dissociation constant of at least about 1 x 10 " , generally at least about 1 x 10 "7 , usually at least about 1 x 10 "8 , and particularly at least about 1 x 10 "9 or 1 x 10 "10 or less. As such, Fab, F(ab') 2 , Fd and Fv fragments of an antibody that retain specific binding activity for an HCV polpeptide of the invention epitope are included within the definition of an antibody. . The term "specifically binds" or "specifically interacts" is used similarly herein to refer to the interaction of members of a specific binding pair, as in SEQ ID NO: 8 and an antibody. The term "antibody" as used herein includes naturally occurring antibodies as well as non-naturally occurring antibodies, including, for example, single chain antibodies, cbimeric antibodies, bifunctional antibodies and humanized antibodies, as well as antigen-binding fragments thereof. Such non-naturally occurring antibodies can be constructed using solid phase peptide synthesis, can be produced recombinantly or can be obtained, for example, by screening combinatorial libraries consisting of variable heavy chains and variable light chains (see Huse et al., Science 246:1275-1281, 1989). These and other methods of making, for example, chimeric, humanized, CDR-grafted, single chain, and bifunctional antibodies are well known to those skilled in the art (Winter and Harris, Immunol. Today 14:243-246, 1993; Ward et al, Nature 341:544-546, 1989; Harlow and Lane, Antibodies: A laboratory manual (Cold Spring Harbor Laboratory Press, 1988); Hilyard et al., Protein Engineering: A practical approach (IRL Press 1992); Borrabeck, Antibody Engineering.2d ed. (Oxford University Press 1995)). The term "antibody" as used in this invention includes intact molecules as well as fragments thereof, such as Fab, F(ab')2, and Fv which are capable of binding to an epitopic determinant present in an invention polypeptide. Such antibody fragments retain some ability to selectively bind with its antigen or receptor. An antibody having a desired specificity can be obtained using well known methods. For example, an antibody having substantially the same specific binding activity of H2 can be prepared using methods as described by Liabeuf et al. (supra, 1981) or otherwise known in the art (Harlow and Lane, "Antibodies: A laboratory manual" (Cold Spring Harbor Laboratory Press 1988)). Where a peptide portion of an HCV polypeptide of the invention used as the immunogen is non-immunogenic, it can be made immunogenic by coupling the hapten to a carrier molecule such as bovine serum albumin (BSA) or keyhole limpet hemocyanin (KLH), or by expressing the peptide portion as a fusion protein. Various other carrier molecules and methods for coupling a hapten to a carrier molecule are well known in the art (see, for example, by Harlow and Lane, supra, 1988). Methods for raising polyclonal antibodies, for example, in a rabbit, goat, mouse or other mammal, are well known in the art (see, for example, Green et al., "Production of Polyclonal Antisera," in Immunochemical Protocols (Manson, ed., Humana Press 1992), pages 1-5; Coligan et al., "Production of Polyclonal Antisera in Rabbits, Rats, Mice and Hamsters," in Curr. Protocols Immunol. (1992), section 2.4.1). Monoclonal antibodies also can be obtained using methods that are well known and routine in the art (Kohler and Milstein, Nature 256:495, 1975; Coligan et al., supra, 1992, sections 2.5.1-2.6.7; Harlow and Lane, supra, 1988). For example, spleen cells from a mouse immunized with 62-microglobulin, or an epitopic fragment thereof, can be fused to an appropriate myeloma cell line such as SP/02 myeloma cells to produce hybridoma cells. Cloned hybridoma cell lines can be screened using, for example, labeled HCV polypeptide to identify clones that secrete monoclonal antibodies having the appropriate specificity, and hybridomas expressing antibodies having a desirable specificity and affinity can be isolated and utilized as a continuous source of the antibodies. Polyclonal antibodies similarly can be isolated, for example, from serum of an immunized animal. Such antibodies, in addition to being useful for performing a method of the invention, also are useful, for example, for preparing standardized kits. A recombinant phage that expresses, for example, a single chain antibody also provides an antibody that can used for preparing standardized kits. Monoclonal antibodies, for example, can be isolated and purified from hybridoma cultures by a variety of well established techniques, including, for example, affinity chromatography with Protein-A SEPHAROSE gel, size exclusion chromatography, and ion exchange chromatography (Barnes et al., in Meth. Mol. Biol. 10:79-104 (Humana Press 1992); Coligan et al., supra, 1992, see sections 2.7.1-2.7.12 and sections 2.9.1-2.9.3). Methods of in vitro and in vivo multiplication of monoclonal antibodies are well known. For example, multiplication in vitro can be carried out in suitable culture media such as Dulbecco's Modified Eagle Medium or RPMI 1640 medium, optionally replenished by a mammalian serum such as fetal calf serum or trace elements and growth sustaining supplements such as normal mouse peritoneal exudate cells, spleen cells, bone marrow macrophages. Production in vitro provides relatively pure antibody preparations and allows scale-up to yield large amounts of the desired antibodies. Large scale hybridoma cultivation can be carried out by homogenous suspension culture in an airlift reactor, in a continuous stirrer reactor, or in immobilized or entrapped cell culture. Multiplication in vivo can be carried out by injecting cell clones into mammals histocompatible with the parent cells, for example, syngeneic mice, to cause growth of antibody-producing tumors. Optionally, the animals can be primed with a hydrocarbon, for example, an oil such as pristane (tetramethylpentadecane) prior to injection. After one to three weeks, the desired monoclonal antibody is recovered from the body fluid of the animal. An antigen binding fragment of an antibody can be prepared by proteolytic hydrolysis of a particular antibody such as H2, or by expression in E. coli of DNA encoding the fragment. Antibody fragments can be obtained by pepsin or papain digestion of whole antibodies by conventional methods. For example, antibody fragments can be produced by enzymatic cleavage of antibodies with pepsin to provide a 5S fragment denoted F(ab')2. This fragment can be further cleaved using a thiol reducing agent, and optionally a blocking group for the sulfhydryl groups resulting from cleavage of disulfide linkages, to produce 3.5S Fab' monovalent fragments. Alternatively, an enzymatic cleavage using pepsin produces two monovalent Fab' fragments and an Fc fragment directly (see, for example, Goldenberg, U.S. Patent No. 4,036,945 and U.S. Pat. No. 4,331,647; Nisonhoff et al., Arch. Biochem. Biophvs. 89:230. 1960; Porter, Biochem. J. 73:119, 1959; Εdelman et al., Meth. Εnzymol.. 1:422 (Academic Press 1967); Coligan et al., supra, 1992, see sections 2.8.1-2.8.10 and 2.10.1-2.10.4). Other methods of cleaving antibodies, such as separation of heavy chains to form monovalent light/heavy chain fragments, further cleavage of fragments, or other enzymatic, chemical, or genetic techniques can also be used, provided the fragments specifically bind to the antigen that is recognized by the intact antibody. For example, Fv fragments comprise an association of variable heavy (VJJ) chains and variable light (VjJ chains, which can be a noncovalent association (fribar et al., Proc. Natl. Acad. Sci.. USA 69:2659, 1972). Alternatively, the variable chains can be linked by an intermolecular disulfide bond or cross-linked by chemicals such as glutaraldehyde (Sandhu, Crit. Rev. Biotechnol. 12:437, 1992). Preferably, the Fv fragments comprise VJJ and V chains connected by a peptide linker. These single-chain antigen binding proteins (sFv) are prepared by constructing a structural gene comprising DNA sequences encoding the VJJ and Vτ_ domains connected by an oligonucleotide. The structural gene is inserted into an expression vector, which is subsequently introduced into a host cell such as E. coli. The recombinant host cells synthesize a single polypeptide chain with a linker peptide bridging the two V domains. Methods for producing sFvs are well known (see, for example, by Whitlow et al., "Methods: A Companion to Methods in Enzymology" 2:97, 1991; Bird et al., Science 242:423-426, 1988; Ladner et al., U.S. Pat. No. 4,946,778; Pack et al., Bio/Technology 11:1271- 1277, 1993; Sandhu, supra, 1992). Another example of an antigen binding fragment of an antibody is a peptide coding for a single complementarity determimng region (CDR). CDR peptides can be obtained by constructing polynucleotides encoding the CDR of an antibody of interest. Such polynucleotides can be prepared, for example, using the polymerase chain reaction to synthesize a variable region encoded by RNA obtained from antibody-producing cells (see, for example, Larrick et al., Methods: A Companion to Methods in Enzymology 2: 106, 19 1, which is incorporated herein by reference). The antibodies of the invention are suited for use, for example, in immunoassays in which they can be utilized in liquid phase or bound to a solid phase carrier. In addition, the antibodies in these immunoassays can be detectably labeled in various ways. Examples of types of immunoassays which can utilize antibodies of the invention are competitive and non-competitive immunoassays in either a direct or indirect format. Examples of such immunoassays are the radioimmunoassay (RIA) and the sandwich (immunometric) assay. Detection of the antigens using the antibodies of the invention can be done utilizing immunoassays which are run in either the forward, reverse, or simultaneous modes, including immunohistochemical assays on physiological samples. Those of skill in the art will know, or can readily discern, other immunoassay formats without undue experimentation. Methods of making these fragments are known in the art. (See for example, Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, New York (1988), incorporated herein by reference). Monoclonal antibodies are made from antigen containing fragments of the protein by methods well known to those skilled in the art (Kohler & Milstein, Nature 256:495 (1975); Coligan et al., sections 2.5.1-2.6.7; and Harlow et al., Antibodies: A Laboratory Manual, page 726 (Cold Spring Harbor Pub. 1988), which are hereby incorporated by reference. Briefly, monoclonal antibodies can be obtained by injecting mice with a composition comprising an antigen/ligand, verifying the presence of antibody production by analyzing a serum sample, removing the spleen to obtain B lymphocytes, fusing the B lymphocytes with myeloma cells to produce hybridomas, cloning the hybridomas, selecting positive clones that produce antibodies to the antigen, and isolating the antibodies from the hybridoma cultures. Monoclonal antibodies can be isolated and purified from hybridoma cultures by a variety of well-established techniques. Such isolation techniques include affinity chromatography with Protein-A Sepharose, size- exclusion chromatography, and ion-exchange chromatography. See, e.g., Coligan et al., sections 2.7.1-2.7.12 and sections 2.9.1-2.9.3; Barnes et al., "Purification of Immunoglobulin G (IgG)" in Methods In Molecular Biology, Vol. 10, pages 79-104 (Humana Press 1992). Antibodies that bind to an invention polypeptide can be prepared using an intact polypeptide or fragments containing small peptides of interest as the immunizing antigen (e.g., SEQ ID NO: 8). It may also be desirable to produce antibodies that specifically bind to the amino- or carboxyl-terminal domains of an invention polypeptide. For the preparation of polyclonal antibodies, the polypeptide or peptide used to immunize an animal is derived from translated cDNA or chemically synthesized and can be conjugated to a carrier protein, if desired. Commonly used carrier proteins which may be chemically coupled to the immunizing peptide include keyhole limpet hemocyanin (KLH), thyroglobulin, bovine serum albumin (BSA), tetanus toxoid, and the like. Invention polyclonal or monoclonal antibodies can be further purified, for example, by binding to and elution from a matrix to which the polypeptide or a peptide to which the antibodies were raised is bound. Those of skill in the art will know of various techniques common in the immunology arts for purification and/or concentration of polyclonal antibodies, as well as monoclonal antibodies (See, for example, Coligan, et al., Unit 9, Current Protocols in Immunology, Wiley friterscience, 1994, incorporated herein by reference). The antibodies of the invention can be bound to many different carriers and used to detect the presence of an antigen comprising the polypeptides of the invention. Examples of well-known carriers include glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, agaroses and magnetite. The nature of the carrier can be either soluble or insoluble for purposes of the invention . Those skilled in the art will know of other suitable carriers for binding antibodies, or will be able to ascertain such, using routine experimentation. There are many different labels and methods of labeling known to those of ordinary skill in the art. Examples of the types of labels which can be used in the present invention include enzymes, radioisotopes, fluorescent compounds, colloidal metals, chemiluminescent compounds, phosphorescent compounds, and bioluminescent compounds. Those of ordinary skill in the art will know of other suitable labels for binding to the antibody, or alternatively to the antigen, or will be able to ascertain such, using routine experimentation. Another feature of the present invention provides a kit containing one or more immunogenic polypeptides of the present invention in a container and an instruction describing the method of using such immunogenic polypeptides. For example, the instruction can describe how to use the immunogenic polypeptide of the present invention or the compositions thereof to treat or immunize a subject for HCV infection. The kit may further comprise an excipient, an adjuvant or a pharmaceutically acceptable carrier. EXAMPLES The following examples are intended to illustrate but not to limit the invention in any manner, shape, or form, either explicitly or implicitly. While they are typical of those that might be used, other procedures, methodologies, or techniques known to those skilled in the art may alternatively be used. Example 1 Preparation of HCV Genotype la and lb 5' and 3' deleted E2 cDNA expression clones To construct the N- and C-terminally truncated HCV E2 protein, the following considerations were made. HCV E2 is a membrane anchored protein, which if expressed as the full-length protein is retained in the endoplasmic reticulum (Cocquerel, L., J Virol 72:2183-91 (1998)). Secreted versions of this glycoprotein required the removal of the hydrophobic anchor domain through at least amino acid 718. However, although recombinant E2 proteins ending at amino acids 688, 704, or 715 are found in the medium only protein ending at amino acid 661 appeared correctly folded by virtue of recognition by conformationally sensitive monoclonal antibody H2 (Michalak, J.P., J Gen Virol 78:2299-306 (1997)). Expression of a recombinant E2 protein ending in amino acid 664 was efficiently secreted by CHO cells (Lesniewski, R., et al., J Med Virol 45:415-22 (1995)). Based on these observations, a cDNA of a recombinant HCV protein Δ)E2, with its C-terminus at amino acid 661 for genotype la was designed. The N-terminal approximately 30 amino acids of HCV E2 protein exhibits the highest degree of genetic heterogeneity within the viral genome (HVRl) (Hijikata, M., et al., Biochem Biophys Res Commun 175:220-8 (1991), and Ogata, N., et al., Proc Natl Acad Sci U S A 88:3392-6 (1991)), contains an immunodominant neutralizing epitope which is under direct selective pressure (Kato, N., J Virol 67:3923-30 (1993)), and has been proposed to act as an "immunologic decoy" to target the immune response away from more conserved regions of the molecule (Ray, S.C., et al., J Virol 73:2938-46 (1999)). Deletion of this region, between amino acids 384 and 411, thus, will produce a polypeptide devoid of this "imunologic decoy", capable of guiding the humoral response to conserved epitopes of the protein (Rosa, D., et al., Proc Natl Acad Sci U S A 93:1759-63 (1996); Lechner, S., et al., Virology 243:313-321 (1998); Flint, M., et al., J Virol 73:6235-44 (1999); and Hadlock, K.G., et al., J Virol 74:10407-16 (2000)), thereby providing the opportunity for broader protection against a variety of HCV isolates. The expression vector constructed to secrete Δ)E2 recombinant protein (SEQ ID NO. 1) from Drosophila melanogaster S2 cells is based on the pMttbns vector (Gulp, J.S., et al., Biotechnology (N Y) 9:173-7 (1991)). The vector pMttbns contains a Drosophila metallothionein gene promoter ( Λ . the human tissue plasminogen activator leader sequence (tPAr,), and the SV40 early polyadenylation signal (Gulp, J.S., et al., Biotechnology (N Y) 9:173-7 (1991)). A 15 bp BamΕΑ DNA fragment containing axiXhol site was deleted from pMttbns to make pMtt)Xho, in which the BglE and Xhol restriction endonuclease sites are unique. This change was confirmed by sequence analysis. Ligation into the BglJl site fuses the insert to the tPAτ_ sequence. During normal maturation of tissue plasminogen activator leader sequence the 20 amino acid pre-peptide region of the leader sequence is removed by signalase in the endoplasmic reticulum and the 11 amino acid pro-peptide region is enzymatically removed in the Golgi. To prepare cDNA of HCV E2 genotype la, Polymerase Chain Reaction (PCR) primers 78E2-1575p and 78E2-2324m were used to amplify E2 sequences from plasmid A+5 (obtained from Dr. Robert Purcell, NIH). Plasmid A+5 contains HCV cDNA encoding amino acids 1-882 of genotype la cloned into the eukaryotic expression vector pcDNA3.1 (Invitrogen). This plasmid was derived from sequences within the infectious cDNA clone of strain H77 (genotype la) (Yanagi, M., et al., Virology 244:161-72 (1998)). The number indicates the location of the primer in the reported sequence, and the notation shows whether the oligonucleotide primes the plus (p) or the minus (m) stand synthesis. The sequence of the primers corresponding to HCV cDNA are written in uppercase letters, non-HCV sequences are written in lowercase letters. Two stop codons are placed after the 661th codon of HCV E2. 78E2-1575p (Bgϊfϊ) 5'-caagatagatctCAACTGATCAACACCAACGGC-3' (SEQ ID NO:2) 5'-ctactttctaga tta eta CTCGGACCTGTCCCTGTCTTC-3' (SEQ ID NO:3) The PCR conditions were 99 °C for 45 seconds, 60 °C for 1 minute and 70 °C for 2 min for 25 cycles. The PCR products and pMtt)Xho vector were digested with Bgl H and Xba I and ligated together under standard conditions. The ligated construct was used to transform E.coli strain XL-1 Blue. Individual colonies were picked and the presence of HCV sequences verified by restriction endonuclease digestion. The resulting plasmid, p78mttHCVE2ΔN)C, was confirmed by sequence analysis. The strategy to subclone HCV E2 genotype lb cDNA followed that described above. Infectious HCV lb clone (Yanagi et al. 1998) was used as template for this work. PCR primer/adaptors 85E2-lbl491p and 85E2-lb2324m were used to amplify E2 cDNA sequences. As describe above, the expressed protein lacks the membrane anchor and hydrophobic tail. The identity of the resulting plasmid, p85mttHCVlbE2ΔNΔC was confirmed by sequence analysis. 85E2-lbl575p (_5g II) 5 , -caagatagatctCAGCTTGTGAATACCAACGGC3- , (SEQ. ID. NO:4) 85E2-lb2324m (Xbaϊ) 5'-ctactttctaga tta eta TTCTGACCTATCCCTGTCCTC-3' (SEQ. ID. NO:5) cDNA clones of C-terminally truncated HCV E2 genotype la and lb proteins with an intact N-terminus were constructed using a strategy similar to that described above. The 5' PCR primer/adaptor used for amplification of la sequences were 78E2- 1491p and the 3' PCR primer/adaptor was 78E2-2324m. The sequence of 78E2- 1491p is given below: 78E2-1491p (Bglϊf) 5 , -attgaaagatctGAAACCCACGTCACCGGGGGAAATG-3 , (SEQ. ID. NO:6) The 5' PCR primer/adaptor used for amplificaton of lb sequences were 85E2- lbl491p and 85E2-lb2324m. The sequence of 85E2-lbl491p is given below: 85E2-lbl491p (Bgt ) 5'-gttgaaagatctGAGACCCACACGACGGGGAG-3' (SEQ. ID. NO:6) The resulting plasmids, p78mttHCVE2ΔC and ρ85mttHCVlbE2ΔC were confirmed by sequence analysis. Example 2 Transfection of Drosophila Cells with Expression Plasmids The Drosophila expression system (U.S. patent 6,046,025, 5,550,043, 5,705,359, 5,681,713) is based on the cotransfection of S2 cells with the expression plasmid containing the gene of interest and a selection plasmid. Both plasmids integrate at high copy number into the genome. The selection plasmid used in our system, the pCoHygro (van der Staten, A., et al., M. Mol. Cell Bio. 1:1-8 (1989); Glaxo SmithKline; U.S. patent 5,681,713) encodes the E. coli hygromycin B phosphotransferase gene under the transcriptional control of the D. melanogaster copia transposable element long terminal repeat and confers resistance to hygromycin B. Drosophila melanogaster Schneider-2 cells (S2; American Type Culture Collection) were plated at 1 x 10 6 cells/ml in 4 ml of Schneiders medium (Invitrogen) supplemented with 10% fetal bovine serum (65 °C, 30'; FBS; Hyclone) one day prior to transfection. The cells were transfected with plasmid DNA at a weight ratio of 20:1 using the calcium phosphate coprecipitation method (U.S. Patent 4,634,665; (Wigler, M., et al., Proc Natl Acad Sci U S A 76:1373-6 (1979); Invitrogen). Briefly, 20 μg of expression plasmid (e.g. p78mttHCVE2ΔNΔC) and 1 μg of selection plasmid, pCoHygro, were combined with a calcium solution. This mixture was slowly added to an equal volume of HEPES buffered saline containing phosphate to give a fine calcium phosphate - DNA precipitate. The precipitate was plated onto the S2 cells and incubated overnight. After approximately 16 hours the transfected cells were washed with two changes of medium and replated in 5 ml of fresh Schneiders medium containing 10% FBS. Three days following addition of DNA, 250 μg/ml hygromycin B (Roche Molecular Biochemicals) was added to the cells. All cells were maintained at 26 °C in a humidified chamber. Following significant outgrowth, and adaptation to serum-free medium (IPL-41 medium supplemented with lipids, yeastolate, and Pluronic F68; Invitrogen; 300 μg/ml hygromycin;), transfectants were plated at a cell density of 2 X 10° cell/ml and induced with 200 mM CuSO . The media were harvested after 7 days of induction. Example 3 Characterization of the secreted HCV ΔE2 and ΔΔE2 structural proteins A. Recombinant HCV ΔE2 and ΔΔE2 of genotypes la and lb are found in the medium. Stable Drosophila S2 cell line transfectants were induced with 200 μM CuSO 4 and grown for seven days at 26 °C. Media from induced cultures were harvested, cells pelleted, fluid filtered, and loaded onto a SDS-polyacrylamide gel. The proteins were separated via electrophoresis and electrotransferred to nitrocellulose. The blots were probed with a combination of anti-E2 monoclonal antibodies Al 1 and 119 (Dubuisson, J., et al., J Virol 70:778-86 (1994)). A clearly visible Coomassie Brilliant Blue staining band for genotype lb ΔE2 and ΔΔE2 is shown in Figure 2, suggesting at least 5 μg/ml of recombinant protein can be found in the medium. Comparison of the cell associated recombinant protein and that found in the media suggests that the proteins are efficiently secreted (data not shown). We are not the first to demonstrate secretion of transmembrane anchorless envelope proteins, however, the level of secreted product was surprising in view of literature (Nishihara, T., et al., Gene 129:207-14 (1993)). In view of the fact that this concentration of protein is from a non-clonal population of cells, the amount of secreted protein is much higher than any reported for other stable mammalian cell transfectants. B. Recombinant HCVAE2 and ΔAE2 are glycosylated. HCV E2 contains eleven potential N inked glycosylation sites. Multiple glycosylation forms of E2 have been described(Lanford, R.E., et al., Virology 197:225-35 (1993)). As shown in Figure 3, treatment with Endoglycosidase Hf (Endo Hf) and PNGase F (New England Biolabs) demonostiates that both recombinant E2 proteins are glycosylated. Endo Hf cleaves only high mannose and hybrid structures, while PNGase F cleaves all N- glycan chains. A loss of Endo Hf sensitivity has been associated with maturation processing of glycoproteins in mammalian cells, while these glycoproteins remain sensitive to PNGase F digestion. A complex shift was observed for both recombinant E2 proteins (Figure 3 and data not shown). N-glycosylation systems for Drosophila melanogaster S2 cells have not been reported but those of Spodoptera frugiperda (Sf9) cells have been reported (Hooker, 1999 #15, Inudoh, M., et al., Vaccine 14:1590-6 (1996)). By inference, then, the glycosylation pattern of S2 cells will be less complex compared to mammalian cells, and the presence of high mannose seen in CHO cell expressed E2 proteins probably does not exist. Sf9 cells have been reported to produce proteins with truncated glycans, notably tri-mannosyl core structures (Kuroda, K., et al. Virology 174:418-29 (1990)) which are resistant to Endo H f C. Recombinant ΔE2 and ΔΔE2 genotype la proteins are recognized by HCV patient serum. Forty-three HCV-positive serum samples were obtained from the Hawaii State Department of Health. These samples had tested positive in both the third generation ELISA and RIB A. The infecting genotype was not known for any of these patients, and it is thought that most of these patients have chronic HCV. For the Western blot analysis, culture medium was separated on a 12% SDS-PAGE, and electrotransferred to nitrocellulose. All serum samples were diluted 1:200 in 0.25% BSA in PBS (BPT) and applied to the blot. Bound human-anti-HCV antibodies were detected with alkaline phosphatase conjugated anti-human IgG mouse monoclonal antibody (Sigma) diluted to 1:2000 and nitro-blue-tetrazolium (NBT) and 5-bromo-4- chloro-3-indolyl-phosphate (BCJP, Promega). A sample was judged to be positive if a fuzzy immunoreactive band of appropriate molecular weight could be clearly identified. Alternatively, an indirect ELISA format was used based on Galanthus nivalis (snow drop) lectin capture (Sigma) to assess the reactivity of the patient serum to native protein. Microtiter wells were coated with the lectin at 5 μg/ml, and buffer- exchanged (PBS) culture medium from induced cultures was added to each well. In addition, a commercially available E2 was tested at 1 μg/ml concentration (baculovirus expressed 70kD E2, nmunoDiagnostics, Inc). The wells were blocked with 1% BSA in PBS and the diluted serum (1:500) was added to the wells. Bound antibody was detected using the same mouse anti-human IgG monoclonal antibody diluted to 1:8000 and p-nitro-phenylphosphate. The reaction was read after 30 minutes for recombinant HCV E2 proteins and 60 minutes for the commercially available E2. Media from induced S2 cells transfected with pCoHygro was used as background control. Positive reactivity was determine as any sample with a reading twice the negative serum control background As seen in Table 1, the majority of the samples recognized native recombinant E2 protein and not denatured recombinant E2 protein. This would corroborate reports by other researchers that the majority of patient antibodies recognized conformational epitopes (Lanford, R.E., et al., Virology 197:225-35 (1993) and Harada, S., et al, J Gen Virol 76:1223-31 (1995)). We did not test the immunoreactivity of the commercially available E2 in a Western blot format. In the ELISA format, 34/43 and 35/43 samples recognized ΔE2 and ΔΔE2 recombinant protein respectively (Table 1). The reactivity of the commercially available E2 proteins in the ELISA format was very disappointing. Only two samples could be considered positive. Based on these results and under non-optimal conditions, recombinant proteins ΔE2 or ΔΔE2 represent the best candidates to screen patient sera for anti-HCV envelope antibodies. The recombinant structural proteins were not recognized by Patients #15, 31, 32, 33, 34, and 44 sera. This is not uncommon, as both chronic and acute patients have been reported to have restricted antibody responses to HCV proteins. In addition, the reactivity of anti-E antibodies has been reported to be genotype specific, and since the infecting genotype is unknown, this could account for the some of the results seen here. Table 1. Immunoreactivity of Patient Sera to Recombinant E2 proteins. D. Recombinant ΔE2 and ΔΛE2 genotype la proteins are recognized by a panel of monoclonal antibodies. The antigenic properties of the recombinant E2 proteins were investigated by ELISA. Conformationally sensitive and insensitive monoclonal antibodies were used to assess the conformation of the recombinant structural proteins. Using the ELISA format as described above, mouse monoclonal antibody (1:10 4 -1:10 5 dilution) was added in place of the human serum and bound antibody was detected using alkaline phosphatase conjugated polyclonal anti-mouse (H + L) antibody (Caltag) and p-nitro phenylphosphate. Again the commercially available baculovirus system expressed HCV E2 protein served as a control. Table 2. describes the immunoreactivity observed. Specificities for the individual monoclonal antibodies are described in the table. All of the monoclonal antibodies, conformationally sensitive (H2, H53, CBH4D, CBH4G, and CBH7) or conformationally insensitive (Al 1, 119, and MO12) bound captured recombinant ΔE2 or ΔΔE2 genotype la protein. The commercially available baculovirus E2 was not recognized by H2, H53, or the human conformationally sensitive monoclonal antibodies. Interestingly the baculovirus E2 was not recognized by monoclonal antibody II 9, a monoclonal antibody which performs very well in Western blot formats. This result demonstrates that the deletion of the HVRl does not alter epitopes recognized by this panel of antibodies, suggesting that the shape of the N- and C-terminally truncated protein and the C-terminally truncated protein are similar. Table 2. Immunoreactivity of recombinant HCV proteins. a= mouse anti-HCV E2 monoclonal antibodies (Dubuisson, J., et al., J Virol 68:6147- 60) b= rat anti-HCV E2 monoclonal antibody (Inudoh, M., et al., Microbol Immunol 42:875-7 (1998)) c= human anti-HCV E2 monoclonal antibodies (Hadlock, K., et al., J Virol 74:10407- 16 (2000)) Example 4 Subcloning of Transfected S2 cells by limiting dilution hnmunofluorescence analysis of transfected bulk culture cells expressing ))E2 protein indicated that no more than 5% of the bulk culture was positive for the expression of recombinant protein. Obtaining a pure population of antigen expressing cells (subcloning), Therefore, should increase the total amount of secreted protein. Subcloning these transfectants was accomplished by plating the cells in 96 well plates at the following densities, 150 cells/well, 100 cells/well, 50 cells/well and 25 cells/well. The cells were resuspended in media containing the following components: 1/3 5-7 day conditioned media; 1/3 IPL-41 (Invitrogen Gibco) supplimented with yeastolate and 20% Fetal Bovine Serum; 1/3 fully supphmented IPL-41. Wells were fed every five - seven days. At the first feeding, 100 μl of plating medium was added. Thereafter, 100 μl of medium was remove from each well and 100 μl of supplimented IPL-41 was added. When sigmficant outgrowth had occurred, approximately 25 μl of cells was transferred to wells containing 200 μl of supplimented IPL-41 containing 200 μM CuSO 4 . Following one week induction, the media was harvested and expression was analyzed by standard dot blot techniques probing with anti-HCV E2 monoclonal antibody H53 (Cocquerel, L., et al., J Virol 72:2183-91 (1998)). The best expressors were then expanded and evaluated in under standard induction conditions. Media proteins were separated by SDS-PAGE and electrotransferred to nitrocellulose, and probed with anti-E2 monoclonal antibodies as described in Example 3. Contrary to intuition, wells plated at lower cell density did not always result in subclones expressing a greater amount of recombinant protein. The subclone which expressed the greatest amount of protein was identified from a 50 cell/well plating. We estimate that this subclone expresses approximately 50-100 mg L of recombinant ))E2 protein. Example 5 Purification of HCV ΔΔE2 la antigen Purification of monomeric ΔΔE2 protein was accomplished in three steps. One goal of the purification procedure was to separate disulfide bonded multimeric, aggregated E2 protein from the monomeric recombinant protein as it has been reported that only monomeric E2 protein binds CD81 (Heile, J.M., et al., J Virol 74:6885-92 (2000)), and therefore, only the monomer presents protective epitopes. Due to this requirement, a large proportion of the total expressed E2 protein was discarded during the purification process. Drosophila melanogaster Schneider-2 cells transfected with plasmid p78mttHCVE2ΔNΔC, subclone 8E were cultured in spinner flasks at 1 x 10 6 cells/ml and induced for 5 days with 0.5 mM CuSO 4 . Three hundred milliliters of harvested media (total protein concentration of 630 μg/ml) was mixed with 300 ml of 2 M sodium sulfate (Aldrich) in 20 mM sodium phosphate pH 6.5 (Dibasic sodium phosphate, Fisher; Monobasic sodium phosphate, Sigma). The 1 M sodium sulfate mixture was put through a 0.45 μm Nalgene filter (Nalge Nunc). ΔΔE2 1 a protein was captured and concentrated using a 5 ml packed Phenyl Sepharose high performance matrix column (Pharmacia Biotech). To prepare the column, 10 bed volumes of distilled water, followed by 5 bed volumes of 0.5 M sodium sulfate-20mM sodium phosphate pH 6.5, and finally TM sodium sulfate- 20mM sodium phosphate pH 6.5 at a flow rate of 2 ml min was used to wash the column. The column was loaded with 600 mis of the 1 M sodium sulfate- 20mM sodium phosphate pH 6.5 filtered mixture, washed with 6 bed volumes of 1 M sodium sulfate-20 mM sodium phosphate pH 6.5, and finally protein was eluted with 10 bed volumes of 20 mM sodium phosphate pH 6.5. The total protein concentration was 900 μg/ml in 50 mis which was a 1.4 fold purification. The eluted fraction as next loaded onto a Galanthus Nivalis lectin column (cross linked to 4% agarose; Sigma). This column was chosen based on the glycosylation status of ΔΔE2 la. Ten milliliters of the eluted fraction from the phenyl sepharose column was incubated with 3.5 ml lectin (packed volume) for 1 hour at room temperature. The mixture was poured into a column, flow through collected, and the column was washed with 4 bed volumes of phosphate buffered saline (PBS) at a flow rate of 1 ml/min. ΔΔE2 la was eluted with 1 M methyl α-D-mannopyranoside (Sigma) in PBS. The total protein concentration was 130 μg/ml in 15 ml which contained about 50 % pure ΔΔE2 la (Figure 4). In the final purification step, 12 mis of the lectin purified ΔΔE2 la was concentrated to 1 ml using a Centriplus 10,000 MW filter (Millipore), and loaded on a Sephacryl S-100 HR column (Sigma), which had been equilibrated with PBS. The column size had a total volume of Vr=173 ml and a void volume of V 0 = 61 ml. A pump was added to produce a flow rate of 0.5 ml/min, and fractions were collected following flowed through of approximately 60 ml of PBS. Six hundred microliter fractions were taken and analyzed by SDS-PAGE and Western blot analysis. Fractions containing ΔΔE2 la monomer were pooled and concentrated through a Centricon 10,000 MW filter (Millipore). The total protein concentration was 150 μg/ml, which contained 80% pure ΔΔE2 1 a. As can be seen in Figure 4, the purified recombinant E2 fraction does not contain multimeric aggregrates of the E2 protein. Example 6 Purified HCV ΔΔE2 genotype la protein is recognized by a Panel of Monoclonal Antibodies To assess whether the recombinant N- and C-terminally truncated E2 protein had retained its native conformation following purification, its immunoreactivity with anti-HCV E2 monoclonal antibodies was analyzed in an indirect ELISA (Dubuisson, J., et al., J Virol 68:6147-60 (1994); Deleersnyder, V., et al, J Virol 71:697-704 (1997); Cocquerel, L., et al., J Virol 72:2183-91 (1998); Inudoh, M., et al., Microbiol Immunol 42:875-7 (1998); and Hadlock, K., et al, J Virol 74:10407-16 (2000)). The results of this assay are presented in Table 3 below. Specificities for the individual monoclonal antibodies are described in the table. Significantly, the recombinant protein was recognized by the conformationally sensitive monoclonal antibodies, while the baculovirus expressed E2 protein was not, confirming the results of sandwich ELISA presented in Example 3 above. Hadlock et al. (2000) have determined whether their human monoclonal antibodies block the binding of E2 to CD81, thus, the fact that human monoclonal CBH-7, a monoclonal antibody which blocks E2 binding to CD81 (an NOB monoclonal antibody), is notable, as it implies that the recombinant protein presents a critical protective epitope. The indirect ELISA protocol is presented below. 1) Microtiter plate wells (96-well Lnmulon 2 plates, Dynex Technologies, Inc.) were coated with 75 μl of coating antigens S2-expressed HCV E2 or Baculovirus expressed HCV E2 (ImmunoDiagnostics, Inc.) at 15 μg/ml in phosphate- buffered saline (PBS), overnight at 4EC. 2) Coating antigen solutions were discarded and 75 μl of 10-fold serial dilutions (starting at 1:500) of the mouse monoclonal antibody in PBS containing 0.05% Tween-20 detergent and 0.1% bovine serum albumin (PBST/BSA). The plates were incubated at room temperature for 2 hours. 3) The sera was discarded from the plates and the wells washed 3 times with PBS containing 0.05% Tween-20 detergent (PBST ). 4) 75 μl of Goat anti-Mouse IgG alkaline phosphatase conjugate (Southern Biotechnology Associates) diluted 1:2,000 in PBST/BSA was then added to each well and the plates incubated for 1 hour at room temperature. 5) The Goat anti-Mouse IgG alkaline phosphatase conjugate was discarded and the wells washed 4 times with PBST. 6) 100 microliters of -nitrophenylphosphate (pNPP; Sigma Chemical Co.) at 1 mg/ml in a buffer consisting of 100 mM Tris-HCl; 100 mM NaCl, 5mM MgCl 2 , pH 9.5 was then added to each well and the plates were incubated at room temperature for 30 minutes. 7) 50 μl of 2.5 N NaOH was then added to each well to stop the reaction. 8) The absorbance at 405 nm of the solution in each well was then determined using an automated microplate reader (spectrophotometer). 9) Reactions were deemed positive it the absorbance values at 405 nm were greater than two fold above the background control absorbance. Table 3. Immune reactivity of various anti-HCV E2 monoclonal antibodies with the purified, recombinant ΔΔE2 protein and baculovirus expressed E2. a= mouse anti-HCV E2 monoclonal antibodies (Dubuisson, J., et al., J Virol 68:6147-60 (1994); Deleersynder, V., et al., J Virol 71 :697-704 (1997); and Cocquerel, L., et al., J Virol 72:2183-91 (1998)) b= rat anti-HCV E2 monoclonal antibody (Inudoh, M., et al, Microbiol Immunol 42:875-7 (1998)) c= human anti-HCV E2 monoclonal antibodies (Hadlock, K., et al, J Virol 74:10407-16 (2000)) Example 7 Immunization of Mice with Purified HCV ΔΔE2 protem Six groups of five 8 week old, female, Balb/c mice (Simonsen Laboratories) each were immunized with purified ΔΔE2 la protein in a variety of modern and traditional adjuvants. All animals were given a primary vaccination, followed three weeks later by a booster vaccination with identical antigen/adjuvant combinations by the same route. Spleens were harvested four and seven days following the second immunization for analysis of cellular immune responses, and sera was taken twelve days following the second immunization for determination of antigen specific antibody response. The following adjuvants were evaluated: alum (Pierce Chemical Co.), QS-21 (Antigenics/AquilaBiopharmaceuticals), MPL-TDM (Corixia Corp.), QS-21 + alum, MPL/TDM + alum. Group 1: 10 μg of HCV ΔΔE2/10 μg of adjuvant QS-21 in 0.2 ml, administered subcutaneously; Group 2: 10 μg of HCV ΔΔE2/2.25 mg alum (AlO(OH)+Mg(OH) 2 ; in 0.2 ml, administered subcutaneously; Group 3: 10 μg of HCV ΔΔE2/10 μg QS-21 + 2.25 mg alum in 0.2 ml, administered subcutaneously; Group 4: 10 μg of HCV ΔΔE2/[50 μg Monophosphoryl Lipid A (MPL) / 50 μg Synthetic Trehalose Dicorynomycolate (TDM) in 0.2 ml, administered intraperitoneally; Group 5: 10 μg of HCV ΔΔE2/(50 μg MPL / 50 μg TDM + 2.25 mg alum) in 0.2 ml, administered intraperitoneally; Group 6: 10 μg QS-21 + 2.25 mg alum in 0.2 ml, administered subcutaneously. Preparation of antigen/adjuvant mixtures [all solutions/suspensions were made in phosphate-buffered saline (PBS), pH 7]: 1) equal volumes of QS-21 (100 μg/ml) and ΔΔE2 (100 μg/ml) were mixed together; 2) an equal volume of alum (22.5 mg/ml in the form of a slurry) was added dropwise to an equal volume of ΔΔE2 (100 μg/ml) while continuously swirling, followed by mixing for 30 min. at room temp.; 3) one half volume of QS-21 (200 μg/ml) was mixed with one volume of ΔΔE2 (100 μg/ml), followed by addition of one half volume of alum (45 mg/ml in the form of a slurry) dropwise while continuously swirling, followed by mixing for 30 min. at room temp.; 4) MPL/TDM (in dry form) was reconstituted at a concentration of 0.5 mg each/ml in PBS by vigorous vortex mixing, as directed by the manufacturer's instructions, followed by addition of an equal volume of ΔΔE2 (100 μg/ml) and further vortex mixing; 5) MPL/TDM (in dry form) was reconstituted at a concentration of 1.0 mg each/ml in PBS by vigorous vortex mixing, as directed by the manufacturer's instructions, followed by addition of two volumes of ΔΔE2 (100 μg/ml) with further vortex mixing, followed by addition of one volume of alum (45 mg/ml in the form of a slurry) dropwise while continuously swirling, followed by mixing for 30 min. at room temp.; 6) one volume of alum (22.5 mg/ml in the form of a slurry) was added to one volume of QS-21 (100 μg/ml) dropwise while continuously swirling followed by mixing for 30 min. at room temp. Example 8 Preparation of Mouse Spleen Cell Suspensions for the Evaluation of the Cellular Immune Response to Purified HCV ΔΔE2 Protein One mouse from each group listed under Example 7 above was sacrificed on the seventh day post vaccination. Splenectomies were performed and splenocyte suspensions were prepared from each spleen in cell culture medium (RPMI 1640 supplemented with 10% heat-inactivated fetal bovine serum, 2 mM L-glutamine, 50 units of penicillin/ml, 50 μg streptomycin/ml, and 50 μg gentamicin/ml). Membraneous debris were allowed to settle out and the cell suspension aspirated and centrifuged. The supernatant was discarded and the cell pellet resuspended in an erythrocyte lysis solution composed of 0.15 M NH CI, 10 mM NaHCO 3 , 0.1 mM EDTA, pH 7.3 (previously filter sterilized). The cell suspension in lysis solution was allowed to remain at room temp, for 10 min. and then centrifuged. The supernatant was discarded and the cell pellet resuspended in supplemented cell culture medium as above. Cell counts were performed on each suspension using a hemacytometer, and diluted to 4 x 10 6 cells/ml with culture medium Example 9 Evaluation of T-Cell Proliferation in Mice Immunized with Purified TTCV ΛΛF/2 Protein Using Several Different Adjuvants Aliquots (0.1 ml) of each cell suspension prepared in Example 8 above were dispensed into wells of a 96-well cell culture plate. Aliquots (0.1 ml) of the stimulants listed below were then dispensed into wells containing each of the cell suspensions (in quadruplicate). Cultures were then incubated at 37° C/5% CO 2 /humidified for specified times (3 days for mitogemc stimulation, 7 days for stimulation with recall antigens). One microcurie of [ H]thymιdine was then added to each well (in a volume of 0.01 ml), and incubation continued for 18 hrs. After that period of time, the cell cultures were harvested onto a glass fiber filtration plate and washed extensively using a vacuum driven harvester system (Filtermate Plate Harvester, Packard Instrument Co.). The filtration plate was then analyzed for radioactivity using the TopCount Microplate Scintillation and Luminescence Counter (Packard Instrument Co.). The following stimulants were used: a) HCV E2, expressed in Drosophila S2 cells as described above; b) HCV E2, Baculovirus expressed (ImmunoDiagnostics, Inc.), c) Phaseolus vulgaris lectin (phytohemagglutinin (PHA), a T cell mitogenic stimulant; Sigma Chemical Co.), d) no stimulant (cell control; culture medium only plus cells). S2 expressed ΔΔE2 was used at 5 μg/ml and PHA at 10 μg/ml (final concentrations). The results of these assays are shown in Figure 5, and demonstrate that Drosophila S2 cell expressed HCV E2 was effective in in vitro stimulation of immune splenocytes from mice vaccinated with HCV E2 in association with some, but not all of the adjuvants tested. The adjuvants that were the most efficacious in engendering splenocytes capable of responding to in vitro stimulation were QS-21 and MPL/TDM. Alum proved to be ineffective for this purpose. Addition of alum to the QS-21 adjuvanted antigen mixture seemed to depress the stimulation of immune splenocytes, while the addition of alum to MPL/TDM had less of an effect. The Baculovirus expressed HCV E2 protein did not stimulate these immune splenocytes to any significant extent, suggesting that this protem did not contain the appropriate configuration of epitopes required for recognition by the responding immune lymphocyte population. Example 10 Evaluation of the Cytokine Response of Purified HCV E2 protein in Mice Using Several Different Adjuvants Aliquots (0.4 ml) of each cell suspension prepared in Example 8 above were dispensed into wells of a 24-well cell culture plate. Aliquots (0.4 ml) of the stimulants listed below were then dispensed into wells containing each of the cell suspensions. Cultures were then incubated for 5 days at 37° C/5% CO 2 /humidified. The culture supernatants were then harvested and frozen for analysis for specific cytokines at a later date. The cytokines interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were assayed by an enzyme-linked immunosorbent assay (ELISA) technique as follows. 1) Microtiter plate wells (96-well hnmulon 2 plates, Dynex Technologies, Inc.) were coated with 75 μl each of capture antibodies (anti-mouse IFN-gamma or anti-mouse IL-4; BD Pharmingen Research Products) at 5 μg/ml in phosphate- buffered saline (PBS), overnight at 4° C. 2) Coating antibody solutions were discarded and 200 μl of culture medium (RPMI 1640; Sigma Chemical Co.) containing 10% fetal bovine serum (FBS; Sigma Chemical Co.) were added to each well and the plates incubated at room temperature for 1 hr. 3) The RPMI 1640+10% FBS (blocking solution) was then discarded and the wells washed 3 times with PBS containing 0.05% Tween 20 detergent (PBST). 4) 75 μl of culture supernatants or standards of IFN-gamma (varying from 1- 10 ng/ml) or IL-4 (varying from 0.25-5 ng/ml) diluted in RPMI 1640/10% FBS were then added to designated wells on the microtiter plates and the plates incubated at room temperature for 2 hrs. 5) The culture supernatants or standards were then discarded and the wells washed 3 times with PBST. 6) 75 μl of detection antibodies (biotinylated anti-mouse IFN-gamma or biotinylated anti-mouse IL-4; BD Pharmingen Research Products) at 2 μg/ml in PBST containing 0.1% bovine serum albumin (PBST/BSA) were then added to the appropriate wells on the microtiter plates and the plates incubated at room temperature for 2 hrs., or overnight at 4° C. 7) The detection antibodies were then discarded and the wells washed 3 times with PBST. 8) 75 μl of streptavidin-alkaline phosphatase conjugate (Southern Biotechnology Associates), diluted 1:2000 in PBST/BSA, was then added to each well and the plates incubated at room temperature for 1 hr. or overnight at 4° C. 9) The streptavidin-alkaline phosphatase was then discarded and the wells washed 4 times with PBST. 10) 100 μl of j-nitrophenylphosphate (pNPP; Sigma Chemical Co.) at 1 mg/ml in a buffer consisting of lOOmM Tris-HCl, 100 mM NaCl, 5 mM MgCl 2 , pH 9.5, were then added to each well and the plates incubated at room temperature in the dark for 15 min. 11) 50 μl of 2.5 N NaOH were then added to each well to stop the reaction. 12) The absorbance at 405 nm of the solution in each well was then determined using an automated microplate reader (spectrophotometer). 13) The absorbance values obtained from the IFN-gamma and IL-4 standards were used to establish a "standard curve" for each of these cytokines. The absorbance values obtained from the culture supernatant samples were then used to assign values of cytokine concentration to each sample by interpolation of the standard curves. The results of these assays are shown in Tables 4 and 5, and indicate that the Drosophila S2 cell expressed HCV ΔΔE2 was capable of stimulating immune splenocytes to produce the cytokines IFN-gamma and IL-4 in vitro, if the splenocytes were taken from mice vaccinated with the S2 cell expressed E2 in association with the adjuvant QS-21. The splenocytes taken from mice vaccinated with S2 cell expressed ΔΔE2 using alum or MPL + TDM as adjuvants did not produce these cytokines when stimulated in vitro. Again, the Baculovirus expressed E2 did not stimulate any of the immune splenocyte populations, including the QS-21 adjuvanted population, to produce cytokines in vitro, consistent with Example 10 above. Table 4. Effect of Different Antigen/Adjuvant Combinations on the Release of Interleukin-4. Table 4. Balb/c mice were immunized and boosted as described in Example 7. Spleens were harvested 7 days after the second immunization. Splenocytes were cultured in the presence of stimulant and supernatants harvested 5 days later. Results are presented as the concentration of IL-4 in ng/ml. Table 5. Effect of Different Antigen/ Adjuvant Combinations on the Release of Interferron-gamma. Table 5. Spleens of immunized Balb/c mice were harvested, and immune splenocytes stimulated with different antigens as described in the table. Results are given as the concentration of INF-γ in ng/ml. Example 11 Evaluation of the Humoral Immune Response of Purified ΔHCV E2 protein in Mice Using Several Different Adjuvants Twelve days after the booster immunization as described in Example 7 above, three mice from each group were bled and serum obtained. Serum samples were pooled from the mice in each group. Sera were analyzed for antibody (IgG) to purified HCV ΔΔE2 protein by an enzyme-linked immunosorbent assay (ELISA) technique as described in Example 6. Pooled sera from immunized mice were serially diluted in PBST/BSA and added to Drosophila S2 cell expressed HCV ΔΔE2 or commercially available Baculovirus expressed E2 and blocked wells. Signal was generated by the addition of goat anti-mouse-alkaline phosphatase conjugate andp- nitrophenylphosphate. Absorbance values at 405 nm were graphed against the log of the antiserum dilution and a titering curve constructed among the data antiserum points for each mouse group. The titer was determined from these titering curves to be the serum dilution which produced an absorbance of 0.5 at 405 nm. The antibody titrations for the serum sample obtained from mice vaccinated with the recombinant soluble ΔΔE2/QS-21 adjuvant combination are depicted in Figure 6. The antibody titers obtained from this sample were 1:112 against the Drosophila S2 cell expressed ΔΔE2 and 1 :22 against the Baculovirus expressed E2. This result suggests that while the antibody elicited by vaccination with the S2 cell expressed E2 in association with QS-21 would react with the Baculovirus expressed E2 protein, a preference for reaction with the S2 cell expressed ΔΔE2 is evident. No other antigen adjuvant combination resulted in a specific anti-ΔΔE2 antibody response. Based on the results of the lymphocyte stimulation experiment and the cytokine data, we expected the specific anti-antigen antibody level would be higher. In addition, we predicted that mice immunized with the antigen/antigen combination of ΔΔE2-MPL/TDM would have resulted in antibody production. The fact that this combination resulted in poor antibody production would not have been predicted from the lymphocyte stimulation data and the cytokine data. 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Claims: What is claimed is: 1. A secreted polypeptide comprising: a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, and further comprising a deletion in at least a portion of its N-terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO: 9). 2. A secreted polypeptide comprising: a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, wherein said E2 polypeptide lacks at least a portion of its C-terminus beginning at about amino acid residue 662 and at least a portion of its N- terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). 3. A purified immunogenic polypeptide comprising the polypeptide of claim 1. 4. The immunogenic polypeptide of claim 3, wherein the amino acid sequence is set forth in SEQ ID NO.8. 5. The immunogenic polypeptide of claim 3, wherein the host cells are insect cells. 6. The immunogenic polypeptide of claim 5, wherein the insect cells are Drosophila cells. 7. The immunogenic polypeptide of claim 6, wherein the insect cells are S2 cells. 8. The immunogenic polypeptide of claim 1, wherein the immunogenic polypeptide is a monomer. 9. The immunogenic polypeptide of claim 1, wherein the immunogenic polypeptide is glycosylated. 10. A composition comprising an immunogenic polypeptide of claim 1 and a pharmaceutically acceptable carrier. 11. A composition comprising an immunogenic polypeptide of claim 1 and an adjuvant. 12. The composition of claim 11, wherein the adjuvant is QS-21. 13. A kit useful for providing immune protection for HCV comprising a container containing a polypeptide of claim 1 and a pharmaceutically acceptable carrier. 14. A immunoprotective composition comprising the polypeptide of claim 3. 15. The composition of claim 14, further comprising an immunomodulatory agent. 16. The composition of claim 15, wherein the immunomodulatory agent is IL-2, GM-CSF, IL-12, gamma-interferon, IP-10, MlPlβ, or RANTES. 17. A method of treating HCV infection comprising administering to a subject having or at risk of having HCV infection an effective amount of the immunogenic polypeptide of claim 3, thereby treating the infection. 18. The method of claim 17, further comprising administering an immunomodulatory agent. 19. The method of claimlδ, wherein the immunomodulatory agent is IL-2, GM- CSF, IL-12, gamma-interferon, IP-10, MlPlβ, or RANTES. 20. A method of providing immune protection against HCV comprising administering to a subject in need of protection an effective amount of the immunogenic polypeptide of claim 3, thereby providing protection from HCV infection. 21. The method of claim 20 further comprising administering an immunomodulatory agent. 22. The method of claim 21, wherein the immunomodulatory agent is IL-2, GM- CSF, IL-12, gamma-interferon, IP-10, MlPlβ, or RANTES. 23. A method of preparing an HCV E2 immunogenic polypeptide of claim 1 comprising expressing a polynucleotide sequence encoding the HCV E2 immunogenic polypeptide in an insect cell line and culturing the cells under conditions which provide HCV E2 polypeptide of claim 1. 24. The method of claim 23, wherein the insect cell line is Drosophila S2 cell line. 25. The method of claim 24, wherein the HCV E2 polypeptide is lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, wherein said E2 polypeptide lacks at least a portion of its C-terminus beginning at about amino acid residue 662 and at least a portion of its N terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). 26. A method for preparing an immunogenic composition for treatment of HCV comprising: (a) forming an immunogenic polypeptide composition comprising a polypeptide of claim 1 , wherein the immunogenic polypeptide composition is suitable for treating HCV; (b) providing a suitable excipient; and (c) mixing the immunogenic composition of (a) with the excipient of (b). 27. A method of producing anti-HCV antibodies comprising administering to a mammal an effective amount of an immunogenic polypeptide composition comprising a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, and further comprising a deletion in at least a portion of its N-terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9). 28. A polyclonal antibody composition made according to the method of claim 27. 29. A purified antibody that specifically binds to a polypeptide of claim 1. 30. A secreted polypeptide comprising: a hepatitis C virus (HCV) E2 polypeptide, lacking all or a portion of its membrane spanning domain such that said E2 polypeptide is capable of secretion into growth medium when expressed recombinantly in a host cell, wherein said E2 polypeptide lacks at least a portion of its C-terminus beginning at about amino acid residue 662 and at least a portion of its N- terminus ending at about amino acid residue 411, numbered with reference to the HCV E2 amino acid sequence (SEQ ID NO:9), wherein said polypeptide is produced recombinantly in insect host cells. 31. The polypeptide of claim 30, wherein the insect cells are Drosophila cells. 32. An isolated polynucleotide encoding a polypeptide of claim 1. 33. The polynucleotide of claim 32, wherein the polynucleotide is set forth in SEQ ID NO:l. 34. The polynucleotide of claim 32, wherein the polypeptide has an amino acid sequence as set forth in SEQ ID NO: 8. 35. A method of detecting the presence of HCV in a sample comprising contacting the sample with an antibody of claim 29 and detecting binding of the antibody to the polypeptide, wherein formation of a complex between the antibody and the E2 polypeptide is indicative of the presence of HCV in the sample. 36. The method of claim 35, wherein the antibody is detectably labeled. 37. A method of detecting HCV infection comprising contacting a biological sample with the immunogenic polypeptide of claim 3 under conditions which allow formation of an antibody-antigen complex and detecting said complex. 38. The method of claim 37, wherein the antigen is detectably labeled.

Inventors: CLEMENTS DAVID E, HUMPHREYS TOM, NAKANO EILEEN T, CLEMENTS, DAVID, E., HUMPHREYS, TOM, NAKANO, EILEEN, T.
Applicants: CLEMENTS DAVID E, HAWAII BIOTECH GROUP, HUMPHREYS TOM, NAKANO EILEEN T, CLEMENTS, DAVID, E., HAWAII BIOTECHNOLOGY GROUP, INC., HUMPHREYS, TOM, NAKANO, EILEEN, T.
Application year: 2001
Main classification: A61K38
IPC codes: A61K38, A61K39, C07K14, C12N5