Immunodominant human T-cell epitopes of hepatitis C virus

Details Immunodominant human T-cell epitopes of hepatitis C virus Immunodominant human T-cell epitopes of hepatitis C virus

1997-11-19

2004-02-10

Zeman, Mary K. (Department: 1631)

Drug, bio-affecting and body treating compositions

Antigen, epitope, or other immunospecific immunoeffector

Virus or component thereof

C424S185100, C424S186100, C424S189100, C424S192100, C424S204100, C530S300000, C530S328000, C530S350000, C530S806000, C530S826000, C435S005000

Reexamination Certificate

active

06689368

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to the production of novel synthetic immunogens related to the hepatitis C virus core, E1, E2 and NS3 regions and to the use thereof in the production of vaccines, therapeutic agents and the like. More specifically, the present invention relates to polypeptide compositions containing HCV core, E1, E2 and NS3 T cell determinants.
BACKGROUND OF THE INVENTION
In the few years since its discovery, Hepatitis C virus (HCV) has been shown to be a major cause of acute and chronic liver disease. HCV is a single-stranded RNA virus with a genome of approximately 9400 nucleotides that consists of a 5′ untranslated region (5′UR) of 341 nucleotides which precedes a single large open reading frame encoding a precursor polyprotein of about 3010 amino acids (Kato et al., 1990). The genetic organization of the viral genome is related to that of flavi-and pestiviruses, with the putative structural proteins located in the N-terminal region and a variety of non structural proteins located at the C-terminal end of the polyprotein. The structural proteins are the core protein (C, amino acids 1-191) followed by the putative envelope proteins E1 (amino acids 192-383) and E2/NS1 (amino acids 384-746). The terms E2 and NS1 are often used interchangeably. Another form of E2 is composed of amino acids 384 to 809 and a third form is associated with NS2. The non structural proteins are NS2, NS3, NS4 and NS5, of which at least NS4 and NS5 have been shown to be further processed into NS4A, NS4B, NS5A, and NS5B.
Structural analysis of HCV genomes revealed the existence of different genotypes that have been classified into types and subtypes (Stuyver et al., 1993). The sequence diversities are distributed along the whole genome including the 5′ untranslated region. The highest sequence variability has been observed in the NS2 and 3′ untranslated regions, and in the putative envelope regions encoding the E1 and E2 proteins. The core, NS3, and certain regions of the NS4 proteins displayed markedly less diversity (Okamoto et al., 1992).
HCV Humoral Response
Soon after the discovery of HCV, immunoassays for the detection of circulating antibodies against HCV proteins became widely available. These tools have led to an explosive increase of the knowledge in the field of the human humoral immune response to HCV in different conditions. Once it was demonstrated that HCV was the major cause of posttransfusional non-A, non-B hepatitis, the search for antibodies to HCV was added to the safety screening panel of blood products. This procedure not only increased the safety of blood transfusions but also enhanced the knowledge of the epidemiology of the virus. The fact that HCV is responsible for a large proportion of chronic hepatic infections in which blood transfusion or parenteral inoculation are excluded remains a major challenge for further epidemiological studies. The widespread use of the assays for the detection of antibodies to HCV has also led to the recognition of the regions with humoral antigenicity of the virus. The relationship between the kinetics and magnitude of the humoral immune response to the different proteins of HCV and the course and outcome of the disease remains to be established.
HCV T Cell Epitopes
The immune response to viral antigens is almost entirely T cell dependent. T cells are required both for antibody production and for some cytotoxic reactions. HCV-encoded proteins are immunogenic not only at the B cell level, but also at the T cell level.
Studies describing the cellular immune response to HCV are scarce. Lin et al. (1993) describe candidate T cell epitopes within absolutely conserved regions of HCV gene obtained by means of a computer search revealing a large number of potential T cell epitopes. It has also been reported that peripheral blood cell monocytes (PBMC) from HCV-infected individuals proliferate in response to HCV recombinant proteins and that peripheral responses to core protein correlate with a benign course of infection (Botarelli et al., 1993). In the liver of patients with chronic HCV infection HCV-specific, HLA class I- restricted cytotoxic T lymphocytes (CTL) have been identified and cloned that recognize epitopes in E1 and NS2 proteins. These investigators have mainly focused on obtaining T cell clones from individual patients, and on the localization of the immunoreactive domain for the single CTL clones. Such studies led to the discovery of the epitope ASRCWVAM (aa 235-242) (SEQ ID NO:167) (in the aminoterminal part of the E1 protein, and of the epitope LMALTLSPYYKRY (aa 826-838) (SEQ ID NO:168) from the NS2 region (Koziel et al., 1992). In patients with chronic HCV hepatitis intrahepatic CD4
+
T cells which specifically recognized the NS4 protein of HCV were observed. The clonotype of these T lymphocytes was not detectable in the PBMC from these subjects (Minutello et al., 1993). These studies demonstrate that in patients with HCV hepatitis, HCV-specific T lymphocytes can be isolated from the infected liver and the peripheral blood. Their role in the pathogenesis of the liver damage in HCV hepatitis and their relevance for the clearance or persistence of the virus remains to be established.
Although neutralization of certain viral infections is possible by humoral immunity only, most microbiological agents can only be cleared from the host with the aid of cellular immunity. Even when the neutralizing capacity of circulating antibodies is established in certain infections, T helper cell activity is generally required to allow B cells to produce the required levels of circulating antibodies, for achievement of neutralization and clearance of the infectious agent. However, certain infectious agents can only be neutralized by means of cellular immunity.
In the case of hepatitis C virus, it can be anticipated that T cell immunity may be required for clearance of the virus, since most patients enter into a chronic course of the disease, and since most patients infected with HCV have developed humoral immunity to most of the HCV antigens which can be employed for diagnosis of HCV infection, as described in patent applications no. EP-A-0 318 216, EP-A-0 388 232, EP-A-0 442 394, EP-A-0 484 787, EP-A-0 489 968. However, most of the antibody-positive patients have not been able to clear the virus from the circulation since they remain HCV-PCR positive and, consequently, the detected antibodies have not been protective neither sufficient to neutralize the virus. Possibly, antibodies to other epitopes which are currently not included in HCV diagnostic assays may be capable of neutralizing HCV infection. Such epitopes may be located on the viral membrane proteins E1 and E2, but protection against a wide range of different HCV species may be hampered by the hypervariability of HCV envelope regions.
The aim of the present invention is to provide T cell stimulating polypeptides and peptides derived from the HCV structural and NS3 regions.
Another aim of the present invention is to provide T cell stimulating polypeptides and peptides as defined above for use in the preparation of an HCV immunogenic composition.
Another aim of the present invention is to provide T cell stimulating peptides or polypeptides derived from the core region, the E1 region, the E2 region, or the NS3 region of HCV.
Another aim of the present invention is to provide T cell stimulating peptides or polypeptides from HCV as specified above which contain either T helper cell (CD4
+
) epitopes and/or CTL (CD8
+
) epitopes.
Another aim of the present invention is to provide recombinant polypeptides containing the same.
Another aim of the present invention is to provide therapeutic as well as prophylactic compositions comprising the same.
Another aim of the present invention is to provide prophylactic or therapeutic compositions comprising said polypeptides.
Another aim of the present invention is to provide methods for preventing or treating HCV infection based on the same.
DETAILED DESCRIPTION OF THE INVENTION

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