title: Synonymous mutations in the core gene are linked to unusual serological profile in hepatitis C virus infection.
abstract: The biological role of the protein encoded by the alternative open reading frame (core+1/ARF) of the Hepatitis C virus (HCV) genome remains elusive, as does the significance of the production of corresponding antibodies in HCV infection. We investigated the prevalence of anti-core and anti-core+1/ARFP antibodies in HCV-positive blood donors from Cambodia, using peptide and recombinant protein-based ELISAs. We detected unusual serological profiles in 3 out of 58 HCV positive plasma of genotype 1a. These patients were negative for anti-core antibodies by commercial and peptide-based assays using C-terminal fragments of core but reacted by Western Blot with full-length core protein. All three patients had high levels of anti-core+1/ARFP antibodies. Cloning of the cDNA that corresponds to the core-coding region from these sera resulted in the expression of both core and core+1/ARFP in mammalian cells. The core protein exhibited high amino-acid homology with a consensus HCV1a sequence. However, 10 identical synonymous mutations were found, and 7 were located in the aa(99-124) region of core. All mutations concerned the third base of a codon, and 5/10 represented a T>C mutation. Prediction analyses of the RNA secondary structure revealed conformational changes within the stem-loop region that contains the core+1/ARFP internal AUG initiator at position 85/87. Using the luciferase tagging approach, we showed that core+1/ARFP expression is more efficient from such a sequence than from the prototype HCV1a RNA. We provide additional evidence of the existence of core+1/ARFP in vivo and new data concerning expression of HCV core protein. We show that HCV patients who do not produce normal anti-core antibodies have unusually high levels of anti-core+1/ARFP and harbour several identical synonymous mutations in the core and core+1/ARFP coding region that result in major changes in predicted RNA structure. Such HCV variants may favour core+1/ARFP production during HCV infection.
authors.affiliation: Institut Pasteur, Hépacivirus et Immunité Innée, CNRS URA 3015, Paris, France. agata.budkowska@pasteur.fr
authors.forename: Agata
authors.initials: A
authors.lastname: Budkowska
authors.forename: Athanassios
authors.initials: A
authors.lastname: Kakkanas
authors.forename: Eric
authors.initials: E
authors.lastname: Nerrienet
authors.forename: Olga
authors.initials: O
authors.lastname: Kalinina
authors.forename: Patrick
authors.initials: P
authors.lastname: Maillard
authors.forename: Srey Viseth
authors.initials: SV
authors.lastname: Horm
authors.forename: Geena
authors.initials: G
authors.lastname: Dalagiorgou
authors.forename: Niki
authors.initials: N
authors.lastname: Vassilaki
authors.forename: Urania
authors.initials: U
authors.lastname: Georgopoulou
authors.forename: Michelle
authors.initials: M
authors.lastname: Martinot
authors.forename: Amadou Alpha
authors.initials: AA
authors.lastname: Sall
authors.forename: Penelope
authors.initials: P
authors.lastname: Mavromara
mesh_terms: D016174:Hepacivirus / Q000235:genetics* / Q000276:immunology; D006526:Hepatitis C / Q000276:immunology / Q000821:virology*; D018937:Hepatitis C Antibodies / Q000097:blood*; D006801:Humans; D009154:Mutation; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D020641:Polymorphism, Single Nucleotide; D012367:RNA, Viral / Q000737:chemistry; D014758:Viral Core Proteins / Q000235:genetics* / Q000276:immunology
chemical_list: D018937:Hepatitis C Antibodies; D012367:RNA, Viral; D014758:Viral Core Proteins