Synonymous mutations in the core gene are linked to unusual serological profile in hepatitis C virus infection.

Agata Budkowska (1) , Athanassios Kakkanas (2) , Eric Nerrienet (3) , Olga Kalinina (4) , Patrick Maillard (1) , Srey Viseth Horm (3) , Geena Dalagiorgou (2) , Niki Vassilaki (2) , Urania Georgopoulou (2) , Michelle Martinot (5) , Amadou Alpha Sall (6) , Penelope Mavromara (2)

1 Hépacivirus et immunité innée
2 Institut Pasteur Hellénique
3 Institut Pasteur du Cambodge
4 Institut Pasteur de Saint-Pétersbourg
5 CRB3 - Centre de recherche biomédicale Bichat-Beaujon
6 Institut Pasteur de Dakar

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 antit-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.

Domaines: Biochimie, Biologie Moléculaire

Agata Budkowska, Athanassios Kakkanas, Eric Nerrienet, Olga Kalinina, Patrick Maillard, et al.. Synonymous mutations in the core gene are linked to unusual serological profile in hepatitis C virus infection.. PLoS ONE, 2011, 6 (1), pp.e15871. ⟨10.1371/journal.pone.0015871⟩. ⟨pasteur-00562342⟩