Link:  Pharm/Biotech Resources

Title:  Antigenic structural peptide, antigenic and immunogenic compounds, and uses for detecting, preventing and treating an HCV infection

United States Patent:  6,964,852

Issued:  November 15, 2005

Inventors:

Jolivet; Michel (Bron, FR); Penin; Francois (Decines, FR); Dalbon; Pascal (Lyons, FR); Ladaviere; Laurent (Villeurbanne, FR); Lacoux; Xavier (Lyons, FR)

Assignee:  Bio Merieux (Marcy, FR)

Appl. No.:  367677

Filed:  February 19, 2003

The invention concerns a structural peptide, identified by antibodies directed against a polypeptide, comprising the 2-45 amino acid sequence of the N-terminal end of the Core or nucleocapsid (p21) protein of the hepatitis C virus (HCV), excluding any protein or peptide compound comprising or consisting of the N-terminal end. The invention is characterized in that it comprises a tertiary structure consisting of at least a first peptide fragment having a secondary structure in α helix, a second peptide fragment having secondary structure in α helix and a third peptide bond fragment linking the two α helices, these two α helices being substantially perpendicular to each other in space. This peptide can be used for detecting antibodies directed against the p21 protein of HCV, for detecting all of part of the RNA of HCV and for preparing a diagnostic, prophylactic or therapeutic composition for detecting, preventing or treating an HCV infection.

The present invention relates to the characterization of an antigenic site belonging to an immunodominant multiepitope region located in the N-terminal end of the Core or nucleocapsid protein (or p21 protein) of the hepatitis C virus (HCV), [B. Hosein et al., Proc. Natl. Acad. Sci. USA, 88, 3647-51 (1991)] as well as to the applications resulting therefrom, in particular in the diagnosis, treatment or prevention of an HCV infection.

In accordance with the document EP-A-0 569 309, in the name of the Applicant, a peptide is known which extends from the amino acid at position 2 to the amino acid at position 45 of the N-terminal end of the HCV nucleocapsid protein, and whose sequence is identified by SEQ ID NO: 1. This peptide determines an immunodominant region which is sufficient, on its own, for obtaining the same sensitivity and specificity, in terms of detection of antibodies directed against HCV, as with the nucleocapsid protein in its entirety.

Continuing its work on the peptide defined above, the Applicant has discovered that:

Thus, the invention relates to a structural peptide, recognized by the antibodies directed against a polypeptide comprising the sequence of amino acids 2-45 of the N-terminal end of the Core protein (p21) of the hepatitis C virus (HCV), which comprises, or consists of, a tertiary structure consisting of at least a first peptide fragment having a secondary structure in the form of an α helix, a second peptide fragment having a secondary structure in the form of an α helix and a third joining peptide fragment linking the two α helices, these two α helices being substantially perpendicular to each other in space. The angle formed by the two α helices is advantageously 90°±10°.

As used herein, the phrase "hepatitis C virus" includes all of the naturally occurring forms of hepatitis C virus.

The third joining peptide fragment is preferably chosen from loops and elbow-shaped secondary structures, in particular β elbows.

According to the present invention, are excluded from the preceding definition, and from the following definitions, all protein or peptide compounds comprising or consisting of the N-terminal end of the p21 protein, this end being considered as starting at the amino acids at position 1 or the amino acid at position 2. The excluded portion preferably includes at least the first 5 amino acids of the N-terminal end of the p21 protein (the first 4 amino acids of the N-terminal end of SEQ ID NO:1); more preferably at least the first 8 amino acids of the N-terminal end of the p21 protein (the first 7 amino acids of the N-terminal end of SEQ ID NO:1); even more preferably at least the first 11 amino acids of the N-terminal end of the p21 protein (the first 10 amino acids of SEQ ID NO:1); and most preferably the first 14 amino acids of the N-terminal end of the p21 protein (the first 13 amino acids of the N-terminal end of SEQ ID NO:1).

Advantageously, the peptide sequence of the peptide of the invention is chosen from any peptide sequence equivalent to SEQ ID NO: 2, such as SEQ ID NO: 3 to 10.

Preferably, the peptide contains fewer than 45 amino acids. More preferably, the peptide contains no more than 35 amino acids. Even more preferably the peptide contains no more than 30 amino acids. Most preferably, the peptide contains about 25 amino acids.

Advantageously, the peptide of the invention is different from the sequence SEQ ID NO: 11 (Gln Arg Lys Thr Lys Arg Asn Thr Asn Arg Arg Pro Gln Asp Val Lys Phe Pro Gly Gly Gly Gln Val Val Gly Gly Val Tyr Leu Leu Pro Arg).

Preferably, the peptide of the invention is different from fragment 4-39 of SEQ ID NO:1.

Before describing the present invention in greater detail and presenting the importance and the applications thereof, a definition of terms used in the description and the claims is given below.

Conformational epitope is understood to mean a protein region recognized by antibodies and determined in particular by amino acids which may be distant in the protein sequence but which, because of the folding of the polypeptide chain, become close to each other in space and may thus form a unit capable of being recognized by the antibody.

Peptide designates a stretch of amino acids which is obtained by chemical synthesis or by genetic recombination techniques. The peptides according to the invention may be obtained by conventional synthesis methods, for example with an automated peptide synthesizer, or by genetic engineering techniques comprising the insertion of a DNA sequence encoding said peptide into an expression vector such as a plasmid or a virus, and the transformation of eukaryotic or prokaryotic cells with this expression vector and culturing of these cells.

Peptide sequence equivalent to a reference peptide sequence (such as SEQ ID NO: 2 in the case of the present invention), said reference peptide sequence having a reference unit, is understood to mean an amino acid sequence modified by insertion and/or deletion and/or substitution and/or extension and/or shortening and/or chemical modification of one or more amino acids, as long as these modifications, on the one hand, substantially preserve, or even amplify, the antigenic properties of said reference peptide sequence and, on the other hand, essentially conserve the reference tertiary structure of said reference peptide sequence.

Thus, "equivalent sequence" is understood to mean in particular the sequences in which one or more amino acids are substituted by one or more other amino acids; the sequences in which one or more amino acids of the L series are replaced by one or more amino acids of the D series; the sequences into which there has been introduced a modification of the amino acid side chains, such as an acetylation of the amine functions, a carboxylation of the thiol functions, an esterification of the carboxyl functions, a substitution of an oxygen atom by a sulfur atom, and the like; a modification of the peptide bonds, such as carba, retro, inverse, retro-inverse, reduced and methyleneoxy bonds.

Peptide sequences equivalent to SEQ ID NO: 2 also comprise those of mimotope peptides which have a very different peptide sequence from SEQ ID NO: 2, while having the same antigenic properties and potentially the same tertiary structure as SEQ ID NO: 2.

Peptide sequences equivalent to SEQ ID NO: 2 also comprise those of mimotope peptides which have a peptide sequence little different from SEQ ID NO: 2, while having the same tertiary structure and the same antigenic properties as SEQ ID NO: 2. These mimotope peptides are described as an example by the peptide sequences SEQ ID NO: 3 to 10.

The secondary structure of a peptide fragment is defined as a three-dimensional structure essentially stabilized by hydrogen bonds involving the atoms which form the primary structure. Several types of secondary structures, and in particular the structure in the form of an α helix and the structure in the form of a β elbow, can be distinguished.

The α helix has been described by Pauling et al. [L. Pauling, Proc. Natl. Acad. Sci. USA, 37, 205-211 (1951)], and corresponds to a right-handed helix. The α helix is essentially stabilized by hydrogen bonds between the oxygen of the carbonyl group of the amino acid at position i and the hydrogen of the amide group of the amino acid at position i+4. These hydrogen bonds are almost parallel to the longitudinal axis of the helix, and the N, H and O involved in the hydrogen bond are practically colinear. The neighboring amino acid residues are 1.5 Å apart on the axis of the α helix, and a complete turn corresponds to 3.6 amino acid residues. The movement along the axis of the helix is therefore 5.4 Å per turn.

The parameters of the α-helix structure are the following:

Angles in degrees: