HCV core peptides

Details HCV core peptides HCV core peptides

2000-05-23

2003-12-23

Fredman, Jeffrey (Department: 1637)

Chemistry: natural resins or derivatives; peptides or proteins;

Peptides of 3 to 100 amino acid residues

C435S007100

Reexamination Certificate

active

06667387

ABSTRACT:

The technical problem underlying the present invention is to provide peptides corresponding to immunologically important epitopes on bacterial and viral proteins, as well as the use of said peptides in diagnostic or immunogenic compositions.
Recent developments in genetic engineering as well as the chemistry of solid phase peptide synthesis have led to the increasingly wider use of synthetic peptides in biochemistry and immunology. Protein sequences which become available as a result of molecular cloning techniques can be synthesized chemically in large quantities for structural, functional, and immunological studies. Peptides corresponding to immunologically important epitopes found on viral and bacterial proteins have also proven to be highly specific reagents which can be used for antibody detection and the diagnosis of infection.
Despite the many advantages synthetic peptides offer, there are a number of disadvantages associated with their use. Because of their relatively short size (generally less than 50 amino acids in length), their structure may fluctuate between many different conformations in the absence of the stabilizing influence of intramolecular interactions present in the full-length protein. Furthermore, the small size of these peptides means that their chemical properties and solubilities will frequently be quite different from those of the full-length protein and that the contribution of individual amino acids in the peptide sequence toward determining the overall chemical properties of the peptide will be proportionally greater.
Many immunological assays require that the antigen used for antibody detection be immobilized on a solid support. Most enzyme-linked immunosorbent assays (ELISA) make use of polystyrene as the solid phase. Many proteins can be stably adsorbed to the solid phase and present sequences which are accessible for subsequent interactions with antibodies. Because of their small size, direct adsorption of peptides to the solid phase frequently gives rise to unsatisfactory results for any of a number of reasons.
Firstly, the peptide may not possess the correct overall charge or amino acid composition which would enable the peptide to bind to the solid phase. Secondly, the same amino acid residues which are required for binding to the solid phase may also be required for antibody recognition and therefore not available for antibody binding. Thirdly, the peptide may become fixed in an unfavorable conformation upon binding to the solid phase which renders it unrecognizable to antibody molecules. In many cases, it is neither possible nor necessary to distinguish between these possibilities. Binding to the solid phase can be increased and made less sensitive to the specific chemical properties of a peptide by first coupling the peptide to a large carrier molecule. Typically, the carrier molecule is a protein.
While the amount of peptide bound to the solid phase, albeit indirectly, can in some cases be increased by this method, this approach suffers from the fact that the linkage between the peptide and the carrier protein frequently involves the side chains of internal trifunctional amino acids whose integrity may be indispensable for recognition by antibodies. The binding avidity of antisera for the internally modified peptide is frequently very much reduced relative to the unmodified peptide or the native protein.
The production of antisera to synthetic peptides also requires in most cases that the peptide be coupled to a carrier. Again, the coupling reaction between an internal trifunctional amino acid of the peptide and the carrier is likely to alter the immunogenic properties of the peptide.
There exist many methods for performing coupling reactions and most of the procedures in current use are discussed in detail in Van Regenmortel, M. H. V., Briand, J. P., Muller, S., and Plaue, S.; Laboratory Techniques in Biochemistry and Molecular Biology, vol. 19, Synthetic Polypeptides as Antigens, Elsevier Press, Amsterdam, New York, Oxford, 1988. In addition to these procedures, unprotected peptides can also be biotinylated using commercially available reagents such as N-hydroxysuccinimidobiotin or biotinamidocaproate N-hydroxysuccinimide ester. Many of these reagents are discussed in Billingsley, M. L., Pennypacker, K. R., Hoover, C. G., and Kincaid, R. L., Biotechniques (1987)5(1):22-31. Biotinylated peptides are capable of being bound by the proteins streptavidin and avidin, two proteins which exhibit extraordinarily high affinity binding to biotin.
In certain instances, it is possible to selectively couple biotin to an unprotected peptide or an unprotected peptide to a carrier. This may be accomplished by synthesizing the peptide with an additional trifunctional amino acid added to one of the ends which is capable of participating in the coupling reaction. This approach will only be successful, however, as long as this amino acid is not a critical residue in the immunogenic sequence of interest and as long as the coupling agent chosen is sufficiently selective. No single technique is applicable to all unprotected peptides regardless of their amino acid composition.
The etiological agent responsible for non-A, non-B hepatitis has been identified and termed hepatitis C virus (HCV). Patent application EP-A-0 318 216 discloses sequences corresponding to approximately 80% of the viral genome. The availability of these sequences rapidly led to the elucidation of the remainder of the coding sequences, particularly those located in the 5′ end of the genome (Okamoto; J. Exp. Med. 60, 167-177, 1990). The HCV genome is a linear, positive-stranded RNA molecule with a length of approximately 9400 nucleotides. With the exception of rather short untranslated regions at the termini, the genome consists of one large, uninterrupted, open reading frame encoding a polyprotein of approximately 3000 amino acids. This polyprotein has been shown to be cleaved co-translationally into individual viral structural and non-structural (NS) regions. The structural protein region is further divided into capsid (Core) and envelope(E1 and E2) proteins. The NS regions are divided into NS-1 to NS-5 regions.
A number of independent patent applications have employed a variety of strategies to determine the locations of diagnostically important amino acid sequences and many of these studies have led to the identification of similar regions of the HCV polyprotein.
The NS4 region has mainly been studied in EP-A-0 318 216, EP-A-0 442 394, U.S. Pat. No. 5,106,726, EP-A-0 489 986, EP-A-0 484 787, and EP-A-0 445 801. Unfortunately only 70% of HCV-infected individuals produce antibodies to NS4, neither the synthetic nor recombinant proteins containing sequences from this region are adequate for identifying all infected serum samples. The nucleocapsid or Core region has been studied in patent applications EP-A-0 442 394, U.S. Pat. No. 5,106,726, EP-A-0 489 986, EP-A-0 445 801, EP-A-0 451 891 and EP-A-0 479 376. It was found that these peptides often used as mixtures, were more frequently recognized by antibodies (85-90%) in sera from chronically infected individuals than were the peptides derived from NS4. The NS5 region was studied in patent applications EP-A-0 489 986 and EP-A-0 468 527. Depending on the serum panel used, more than 60% of NANB hepatitis can be shown to contain antibodies directed against these peptides. The NS3 region was also studied in patent application EP-A-0 468 527. All available evidence suggests that the most dominant epitope of NS3 are discontinuous in nature and cannot be adequately represented by synthetic peptides. The E1 region which is potentially interesting as a region from the outer surface of the virus particles (possible immunogenic epitopes) was studied in both patent applications EP-A-0 468 527 and EP-A-0 507 615. The E2/NS1 region was studied for the same reason as E1. Comparisons of this region from different HCV variants elucidated that this protein contains variable region which are reminiscent of the HIV V3 loop region of gp120 envelope prot

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