OBJECTIVETo identify the location of major immunodominant antigenic region and study the relationship between the gene heterogeneity and immunoreactivity via detecting antigenic reactivity of synthetic peptides deriving from immunodominant region in different genotypes of hepatitis C virus (HCV) NS5a gene.

METHODSIn total, 305 non-identical 30-mer long and overlapping by 15 aa peptides derived from HCV NS5a region from codon 2,182 to 2,343 among 45 unique published HCV sequences in GenBank corresponding to different genotype were designed and synthesized. The amino acid sequences of all peptides were compared with DNA Star software. The antigenic reactivity of those peptides was detected with indirect ELISA with both anti-HCV and anti-NS5 positive serum.

RESULTSThe sequences showed highly conserved among HCV genotype in regions 2,272-2,301 and 2,302-2,331 as compared to regions 2,212-2,241 and 2,257-2,286. The peptides basing on amino acid residues among 2,212-2,241, 2,272-2,301 and 2,302-2,331 showed stronger immunoreactivity than any other peptides. Eighteen peptides derived from this region showed a broad immunoreactivity, 3 of them could react with 96% of anti-HCV positive sera. Whereas the immunoreactivity of the peptides derived from the region showing highly variable among HCV genotype was found to react more strongly with homologous-genotype sera.

CONCLUSIONThe major linear antigenic region was located at amino acid residues among 2,212-2,241, 2,272-2,301 and 2,302-2,331; the short synthetic peptide derived from NS5a region at position 2,212-2,241, 2,272-2,301 and 2,302-2,331 can be used for efficient detection of HCV antibody; some peptides showed genotype specific immuunoreactivity.

Amino Acid Sequence ; Antigenic Variation ; Antigens, Viral ; blood ; immunology ; Epitope Mapping ; Genotype ; Hepacivirus ; classification ; genetics ; immunology ; Hepatitis C ; immunology ; virology ; Hepatitis C Antibodies ; blood ; immunology ; Humans ; Immunodominant Epitopes ; Peptides ; chemical synthesis ; immunology ; Recombinant Proteins ; genetics ; immunology ; Sequence Homology, Amino Acid ; Viral Nonstructural Proteins ; genetics ; immunology

Escherichia coli ; genetics ; Humans ; Recombinant Fusion Proteins ; immunology ; Viral Nonstructural Proteins ; genetics ; immunology

BACKGROUNDNumerous studies have reported a relationship between hepatitis C virus (HCV) genotype and the response to interferon therapy. Despite high sensitivity and specificity, genotyping methods can be performed only on HCV RNA positive samples. Serotyping might be a rapid and cost effective method for determining HCV genotypes, especially in patients with previously undetectable HCV RNA. In this study, an enzyme linked immunosorbent assay (ELISA) method for HCV serotyping with the genotype specific, synthetic peptides derived from HCV nonstructural 5a (NS5A) region was developed.

METHODSBased on 45 sequences, representing HCV genotypes 1 - 6 from Genebank, we synthesised 305 overlapping 30-mer peptides within NS5A region at positions 2182 - 2343 of HCV. All peptides for antigenic reactivity were tested by enzyme immunoassay with 69 human sera with antiHCV positive representing genotype 1 - 6. Forty hepatitis C patient sera were serotyped using serotype specific, synthetic peptides and genotyped by sequencing analysis.

RESULTSThe correspondence of amino acids in HCV NS5A region with amino acids in positions 2182 - 2343 was very low among different genotype peptides. The highly conserved sequences were residues 2182 - 2211 (R1), 2272 - 2301 (R7) and 2302 - 2331 (R9): the highly variable 2212 - 2241 (R3) and 2257 - 2286 (R6). Using 305 peptides, antigenic regions were located in R3, R7 and R9. Eighteen peptides from highly conserved region representing genotypes 1 to 6 showed broad immunoreactivity with sera containing antibody to all HCV genotypes. Immunoreactivity of the peptides from highly variable region was stronger with similar genotype sera. Twelve unique peptides showed highly, genotype specific, reactivity with types 1 and 3 sera. Type 2 genotype specific peptides had cross reaction with type 3 serum. No type 4, 5 or 6 specific peptides were selected. The serotyping results showed high agreement with sequencing analysis.

CONCLUSIONSThe major antigenic regions in HCV NS5A region were at 2212 - 2241 (R3), 2272 - 2301 (R7) and 2302 - 2331 (R9). Eighteen peptides from highly conserved region show genotype independent, immunoreactivity, useful for antiHCV antibody test. Twelve peptides from highly variable region show genotype 1 and 3 dependent immunoreactivity, useful for determining HCV serotype, especially for patients with previously undetectable HCV RNA.

Amino Acid Sequence ; Genotype ; Hepacivirus ; classification ; genetics ; Humans ; Molecular Sequence Data ; Serotyping ; Viral Nonstructural Proteins ; chemistry ; immunology