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Vol. 55, No. 1, 2012
Issue release date: November 2011
Intervirology 2012;55:1–11
(DOI:10.1159/000322219)

Polymorphisms of Hepatitis C Virus Non-Structural Protein 5A and Core Protein and Clinical Outcome of Pegylated-Interferon/Ribavirin Combination Therapy

El-Shamy A.a, c · Kim S.-R.b · Ide Y.-H.a · Sasase N.b · Imoto S.b · Deng L.a · Shoji I.a · Hotta H.a
aDivision of Microbiology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, and bDivision of Gastroenterology, Kobe Asahi Hospital, Kobe, Japan; cDepartment of Virology, Suez Canal University Faculty of Veterinary Medicine, Ismalia, Egypt
email Corresponding Author

Abstract

Objective: Hepatitis C virus (HCV genome) polymorphisms are thought to influence the outcome of pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy. This study aimed to examine non-structural protein 5A (NS5A) polymorphisms, e.g. IFN/RBV resistance-determining region (IRRDR) and IFN sensitivity-determining region (ISDR), and core protein polymorphism as predictive therapeutic markers. Methods: Pretreatment sequences of NS5A and core regions were analyzed in 68 HCV-1b-infected patients treated with PEG-IFN/RBV. Results: Of 24 patients infected withHCV having an IRRDR with 6 or more mutations (IRRDR≧6), 18 (75%) patients achieved sustained virological response (SVR), whereas only 11 (25%) of 44 patients infected with HCV having IRRDR≤5 did. IRRDR≧6 was significantly associated with SVR (p < 0.0001). On the other hand, ISDR≧2 was significantly associated with relapse (either before [breakthrough] or after end-of-treatment response [ETR[-]relapse]) (p < 0.05) and a point mutation of the core protein from Arg to Gln at position 70 (Gln70) was significantly associated with null-response (p < 0.05). Multivariate analysis identified IRRDR≧6 as the only viral genetic factor that independently predicted SVR. Conclusion: NS5A (IRRDR and ISDR) and core protein polymorphisms are associated with the outcome of PEG-IFN/RBV therapy for chronic hepatitis C. In particular, IRRDR≧6 is a useful marker for prediction of SVR.


 goto top of outline Key Words

  • Hepatitis C virus
  • Non-structural protein 5A
  • Interferon/ribavirin resistance-determining region
  • Interferon sensitivity-determining region
  • Core protein
  • Sustained virological response
  • Prediction

 goto top of outline Abstract

Objective: Hepatitis C virus (HCV genome) polymorphisms are thought to influence the outcome of pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy. This study aimed to examine non-structural protein 5A (NS5A) polymorphisms, e.g. IFN/RBV resistance-determining region (IRRDR) and IFN sensitivity-determining region (ISDR), and core protein polymorphism as predictive therapeutic markers. Methods: Pretreatment sequences of NS5A and core regions were analyzed in 68 HCV-1b-infected patients treated with PEG-IFN/RBV. Results: Of 24 patients infected withHCV having an IRRDR with 6 or more mutations (IRRDR≧6), 18 (75%) patients achieved sustained virological response (SVR), whereas only 11 (25%) of 44 patients infected with HCV having IRRDR≤5 did. IRRDR≧6 was significantly associated with SVR (p < 0.0001). On the other hand, ISDR≧2 was significantly associated with relapse (either before [breakthrough] or after end-of-treatment response [ETR[-]relapse]) (p < 0.05) and a point mutation of the core protein from Arg to Gln at position 70 (Gln70) was significantly associated with null-response (p < 0.05). Multivariate analysis identified IRRDR≧6 as the only viral genetic factor that independently predicted SVR. Conclusion: NS5A (IRRDR and ISDR) and core protein polymorphisms are associated with the outcome of PEG-IFN/RBV therapy for chronic hepatitis C. In particular, IRRDR≧6 is a useful marker for prediction of SVR.

Copyright © 2011 S. Karger AG, Basel


 goto top of outline References
  1. Bialek SR, Terrault NA: The changing epidemiology and natural history of hepatitis C virus infection. Clin Liver Dis 2006;10:697–715.
  2. Williams R: Global challenges in liver disease. Hepatology 2006;44:521–526.
  3. Fried MW, Shiffman ML, Reddy KR, Smith C, Marinos G, Goncales FL Jr, Haussinger D, Diago M, Carosi G, Dhumeaux D, Craxi A, Lin A, Hoffman J, Yu J: Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975–982.
  4. Backus LI, Boothroyd DB, Phillips BR, Mole LA: Predictors of response of US veterans to treatment for the hepatitis C virus. Hepatology 2007;46:37–47.
  5. Welker MW, Hofmann WP, Welsch C, von Wagner M, Herrmann E, Lengauer T, Zeuzem S, Sarrazin C: Correlation of amino acid variations within nonstructural 4B protein with initial viral kinetics during interferon-α-based therapy in HCV-1b-infected patients. J Viral Hepat 2007;14:338–349.
  6. Enomoto N, Sakuma I, Asahina Y, Kurosaki M, Murakami T, Yamamoto C, Ogura Y, Izumi N, Marumo F, Sato C: Mutations in the nonstructural protein 5A gene and response to interferon in patients with chronic hepatitis C virus 1b infection. N Engl J Med 1996;334:77–81.
  7. El-Shamy A, Nagano-Fujii M, Sasase N, Imoto S, Kim SR, Hotta H: Sequence variation in hepatitis C virus nonstructural protein 5A predicts clinical outcome of pegylated interferon/ribavirin combination therapy. Hepatology 2008;48:38–47.
  8. Akuta N, Suzuki F, Kawamura Y, Yatsuji H, Sezaki H, Suzuki Y, Hosaka T, Kobayashi M, Kobayashi M, Arase Y, Ikeda K, Kumada H: Predictive factors of early and sustained responses to peginterferon plus ribavirin combination therapy in Japanese patients infected with hepatitis C virus genotype 1b: amino acid substitutions in the core region and low-density lipoprotein cholesterol levels. J Hepatol 2007;46:403–410.
  9. Akuta N, Suzuki F, Sezaki H, Suzuki Y, Hosaka T, Someya T, Kobayashi M, Saitoh S, Watahiki S, Sato J, Matsuda M, Kobayashi M, Arase Y, Ikeda K, Kumada H: Association of amino acid substitution pattern in core protein of hepatitis C virus genotype 1b high viral load and non-virological response to interferon-ribavirin combination therapy. Intervirology 2005;48:372–380.
  10. Okamoto H, Sugiyama Y, Okada S, Kurai K, Akahane Y, Sugai Y, Tanaka T, Sato K, Tsuda F, Miyakawa Y, et al: Typing hepatitis C virus by polymerase chain reaction with type-specific primers: application to clinical surveys and tracing infectious sources. J Gen Virol 1992;73:673–679.
  11. El-Shamy A, Sasayama M, Nagano-Fujii M, Sasase N, Imoto S, Kim SR, Hotta H: Prediction of efficient virological response to pegylated interferon/ribavirin combination therapy by NS5A sequences of hepatitis C virus and anti-NS5A antibodies in pretreatment sera. Microbiol Immunol 2007;51:471–482.
  12. Ogata S, Nagano-Fujii M, Ku Y, Yoon S, Hotta H: Comparative sequence analysis of the core protein and its frameshift product, the F protein, of hepatitis C virus subtype 1b strains obtained from patients with and without hepatocellular carcinoma. J Clin Microbiol 2002;40:3625–3630.
  13. Shirakawa H, Matsumoto A, Joshita S, Komatsu M, Tanaka N, Umemura T, Ichijo T, Yoshizawa K, Kiyosawa K, Tanaka E: Pretreatment prediction of virological response to peginterferon plus ribavirin therapy in chronic hepatitis C patients using viral and host factors. Hepatology 2008;48:1753–1760.
  14. Okanoue T, Itoh Y, Hashimoto H, Yasui K, Minami M, Takehara T, Tanaka E, Onji M, Toyota J, Chayama K, Yoshioka K, Izumi N, Akuta N, Kumada H: Predictive values of amino acid sequences of the core and NS5A regions in antiviral therapy for hepatitis C: a Japanese multi-center study. J Gastroenterol 2009;44:952–963.
  15. Kau A, Vermehren J, Sarrazin C: Treatment predictors of a sustained virologic response in hepatitis B and C. J Hepatol 2008;49:634–651.
  16. Ge D, Fellay J, Thompson AJ, Simon JS, Shianna KV, Urban TJ, Heinzen EL, Qiu P, Bertelsen AH, Muir AJ, Sulkowski M, McHutchison JG, Goldstein DB: Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature 2009;461:399–401.
  17. Suppiah V, Moldovan M, Ahlenstiel G, Berg T, Weltman M, Abate ML, Bassendine M, Spengler U, Dore GJ, Powell E, Riordan S, Sheridan D, Smedile A, Fragomeli V, Muller T, Bahlo M, Stewart GJ, Booth DR, George J: IL28B is associated with response to chronic hepatitis C interferon-α and ribavirin therapy. Nat Genet 2009;41:1100–1104.
  18. Tanaka Y, Nishida N, Sugiyama M, Kurosaki M, Matsuura K, Sakamoto N, Nakagawa M, Korenaga M, Hino K, Hige S, Ito Y, Mita E, Tanaka E, Mochida S, Murawaki Y, Honda M, Sakai A, Hiasa Y, Nishiguchi S, Koike A, Sakaida I, Imamura M, Ito K, Yano K, Masaki N, Sugauchi F, Izumi N, Tokunaga K, Mizokami M: Genome-wide association of IL28B with response to pegylated interferon-α and ribavirin therapy for chronic hepatitis C. Nat Genet 2009;41:1105–1109.
  19. Murakami T, Enomoto N, Kurosaki M, Izumi N, Marumo F, Sato C: Mutations in nonstructural protein 5A gene and response to interferon in hepatitis C virus genotype 2 infection. Hepatology 1999;30:1045–1053.
  20. Akuta N, Suzuki F, Hirakawa M, Kawamura Y, Yatsuji H, Sezaki H, Suzuki Y, Hosaka T, Kobayashi M, Kobayashi M, Saitoh S, Arase Y, Ikeda K, Kumada H: Association of amino acid substitution pattern in core protein of hepatitis C virus genotype 2a high viral load and virological response to interferon-ribavirin combination therapy. Intervirology 2009;52:301–309.
  21. Tsai YH, Kuang WF, Lu TY, Kao JH, Lai MY, Liu CJ, Chen PJ, Hwang LH: The non-structural 5A protein of hepatitis C virus exhibits genotypic differences in interferon antagonism. J Hepatol 2008;49:899–907.
  22. Macdonald A, Harris M: Hepatitis C virus NS5A: tales of a promiscuous protein. J Gen Virol 2004;85:2485–2502.
  23. Moradpour D, Evans MJ, Gosert R, Yuan Z, Blum HE, Goff SP, Lindenbach BD, Rice CM: Insertion of green fluorescent protein into nonstructural protein 5A allows direct visualization of functional hepatitis C virus replication complexes. J Virol 2004;78:7400–7409.
  24. Appel N, Pietschmann T, Bartenschlager R: Mutational analysis of hepatitis C virus nonstructural protein 5A: potential role of differential phosphorylation in RNA replication and identification of a genetically flexible domain. J Virol 2005;79:3187–3194.
  25. Yuan HJ, Jain M, Snow KK, Gale Jr M, Lee WM: Evolution of hepatitis C virus NS5A region in breakthrough patients during pegylated interferon and ribavirin therapy. J Viral Hepat 2009;17:208–216.
  26. Enomoto N, Maekawa S: HCV genetic elements determining the early response to peginterferon and ribavirin therapy. Intervirology 2010;53:66–69.
  27. Hughes M, Griffin S, Harris M: Domain III of NS5A contributes to both RNA replication and assembly of hepatitis C virus particles. J Gen Virol 2009;90:1329–1334.
  28. Appel N, Zayas M, Miller S, Krijnse-Locker J, Schaller T, Friebe P, Kallis S, Engel U, Bartenschlager R: Essential role of domain III of nonstructural protein 5A for hepatitis C virus infectious particle assembly. PLoS Pathog 2008;4:e1000035.
  29. Masaki T, Suzuki R, Murakami K, Aizaki H, Ishii K, Murayama A, Date T, Matsuura Y, Miyamura T, Wakita T, Suzuki T: Interaction of hepatitis C virus nonstructural protein 5A with core protein is critical for the production of infectious virus particles. J Virol 2008;82:7964–7976.
  30. Gale M Jr, Foy EM: Evasion of intracellular host defence by hepatitis C virus. Nature 2005;436:939–945.

 goto top of outline Author Contacts

Hak Hotta, MD, PhD
Division of Microbiology, Center for Infectious Diseases
Kobe University Graduate School of Medicine
7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017 (Japan)
Tel. +81 78 382 5500, Fax +81 78 382 5519, E-Mail hotta@kobe-u.ac.jp


 goto top of outline Article Information

Received: May 12, 2010
Accepted after revision: October 14, 2010
Published online: February 4, 2011
Number of Print Pages : 11
Number of Figures : 2, Number of Tables : 7, Number of References : 30


 goto top of outline Publication Details

Intervirology (International Journal of Basic and Medical Virology)

Vol. 55, No. 1, Year 2012 (Cover Date: November 2011)

Journal Editor: Liebert U.G. (Leipzig)
ISSN: 0300-5526 (Print), eISSN: 1423-0100 (Online)

For additional information: http://www.karger.com/INT


Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Abstract

Objective: Hepatitis C virus (HCV genome) polymorphisms are thought to influence the outcome of pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy. This study aimed to examine non-structural protein 5A (NS5A) polymorphisms, e.g. IFN/RBV resistance-determining region (IRRDR) and IFN sensitivity-determining region (ISDR), and core protein polymorphism as predictive therapeutic markers. Methods: Pretreatment sequences of NS5A and core regions were analyzed in 68 HCV-1b-infected patients treated with PEG-IFN/RBV. Results: Of 24 patients infected withHCV having an IRRDR with 6 or more mutations (IRRDR≧6), 18 (75%) patients achieved sustained virological response (SVR), whereas only 11 (25%) of 44 patients infected with HCV having IRRDR≤5 did. IRRDR≧6 was significantly associated with SVR (p < 0.0001). On the other hand, ISDR≧2 was significantly associated with relapse (either before [breakthrough] or after end-of-treatment response [ETR[-]relapse]) (p < 0.05) and a point mutation of the core protein from Arg to Gln at position 70 (Gln70) was significantly associated with null-response (p < 0.05). Multivariate analysis identified IRRDR≧6 as the only viral genetic factor that independently predicted SVR. Conclusion: NS5A (IRRDR and ISDR) and core protein polymorphisms are associated with the outcome of PEG-IFN/RBV therapy for chronic hepatitis C. In particular, IRRDR≧6 is a useful marker for prediction of SVR.



 goto top of outline Author Contacts

Hak Hotta, MD, PhD
Division of Microbiology, Center for Infectious Diseases
Kobe University Graduate School of Medicine
7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017 (Japan)
Tel. +81 78 382 5500, Fax +81 78 382 5519, E-Mail hotta@kobe-u.ac.jp


 goto top of outline Article Information

Received: May 12, 2010
Accepted after revision: October 14, 2010
Published online: February 4, 2011
Number of Print Pages : 11
Number of Figures : 2, Number of Tables : 7, Number of References : 30


 goto top of outline Publication Details

Intervirology (International Journal of Basic and Medical Virology)

Vol. 55, No. 1, Year 2012 (Cover Date: November 2011)

Journal Editor: Liebert U.G. (Leipzig)
ISSN: 0300-5526 (Print), eISSN: 1423-0100 (Online)

For additional information: http://www.karger.com/INT


Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

References

  1. Bialek SR, Terrault NA: The changing epidemiology and natural history of hepatitis C virus infection. Clin Liver Dis 2006;10:697–715.
  2. Williams R: Global challenges in liver disease. Hepatology 2006;44:521–526.
  3. Fried MW, Shiffman ML, Reddy KR, Smith C, Marinos G, Goncales FL Jr, Haussinger D, Diago M, Carosi G, Dhumeaux D, Craxi A, Lin A, Hoffman J, Yu J: Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975–982.
  4. Backus LI, Boothroyd DB, Phillips BR, Mole LA: Predictors of response of US veterans to treatment for the hepatitis C virus. Hepatology 2007;46:37–47.
  5. Welker MW, Hofmann WP, Welsch C, von Wagner M, Herrmann E, Lengauer T, Zeuzem S, Sarrazin C: Correlation of amino acid variations within nonstructural 4B protein with initial viral kinetics during interferon-α-based therapy in HCV-1b-infected patients. J Viral Hepat 2007;14:338–349.
  6. Enomoto N, Sakuma I, Asahina Y, Kurosaki M, Murakami T, Yamamoto C, Ogura Y, Izumi N, Marumo F, Sato C: Mutations in the nonstructural protein 5A gene and response to interferon in patients with chronic hepatitis C virus 1b infection. N Engl J Med 1996;334:77–81.
  7. El-Shamy A, Nagano-Fujii M, Sasase N, Imoto S, Kim SR, Hotta H: Sequence variation in hepatitis C virus nonstructural protein 5A predicts clinical outcome of pegylated interferon/ribavirin combination therapy. Hepatology 2008;48:38–47.
  8. Akuta N, Suzuki F, Kawamura Y, Yatsuji H, Sezaki H, Suzuki Y, Hosaka T, Kobayashi M, Kobayashi M, Arase Y, Ikeda K, Kumada H: Predictive factors of early and sustained responses to peginterferon plus ribavirin combination therapy in Japanese patients infected with hepatitis C virus genotype 1b: amino acid substitutions in the core region and low-density lipoprotein cholesterol levels. J Hepatol 2007;46:403–410.
  9. Akuta N, Suzuki F, Sezaki H, Suzuki Y, Hosaka T, Someya T, Kobayashi M, Saitoh S, Watahiki S, Sato J, Matsuda M, Kobayashi M, Arase Y, Ikeda K, Kumada H: Association of amino acid substitution pattern in core protein of hepatitis C virus genotype 1b high viral load and non-virological response to interferon-ribavirin combination therapy. Intervirology 2005;48:372–380.
  10. Okamoto H, Sugiyama Y, Okada S, Kurai K, Akahane Y, Sugai Y, Tanaka T, Sato K, Tsuda F, Miyakawa Y, et al: Typing hepatitis C virus by polymerase chain reaction with type-specific primers: application to clinical surveys and tracing infectious sources. J Gen Virol 1992;73:673–679.
  11. El-Shamy A, Sasayama M, Nagano-Fujii M, Sasase N, Imoto S, Kim SR, Hotta H: Prediction of efficient virological response to pegylated interferon/ribavirin combination therapy by NS5A sequences of hepatitis C virus and anti-NS5A antibodies in pretreatment sera. Microbiol Immunol 2007;51:471–482.
  12. Ogata S, Nagano-Fujii M, Ku Y, Yoon S, Hotta H: Comparative sequence analysis of the core protein and its frameshift product, the F protein, of hepatitis C virus subtype 1b strains obtained from patients with and without hepatocellular carcinoma. J Clin Microbiol 2002;40:3625–3630.
  13. Shirakawa H, Matsumoto A, Joshita S, Komatsu M, Tanaka N, Umemura T, Ichijo T, Yoshizawa K, Kiyosawa K, Tanaka E: Pretreatment prediction of virological response to peginterferon plus ribavirin therapy in chronic hepatitis C patients using viral and host factors. Hepatology 2008;48:1753–1760.
  14. Okanoue T, Itoh Y, Hashimoto H, Yasui K, Minami M, Takehara T, Tanaka E, Onji M, Toyota J, Chayama K, Yoshioka K, Izumi N, Akuta N, Kumada H: Predictive values of amino acid sequences of the core and NS5A regions in antiviral therapy for hepatitis C: a Japanese multi-center study. J Gastroenterol 2009;44:952–963.
  15. Kau A, Vermehren J, Sarrazin C: Treatment predictors of a sustained virologic response in hepatitis B and C. J Hepatol 2008;49:634–651.
  16. Ge D, Fellay J, Thompson AJ, Simon JS, Shianna KV, Urban TJ, Heinzen EL, Qiu P, Bertelsen AH, Muir AJ, Sulkowski M, McHutchison JG, Goldstein DB: Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature 2009;461:399–401.
  17. Suppiah V, Moldovan M, Ahlenstiel G, Berg T, Weltman M, Abate ML, Bassendine M, Spengler U, Dore GJ, Powell E, Riordan S, Sheridan D, Smedile A, Fragomeli V, Muller T, Bahlo M, Stewart GJ, Booth DR, George J: IL28B is associated with response to chronic hepatitis C interferon-α and ribavirin therapy. Nat Genet 2009;41:1100–1104.
  18. Tanaka Y, Nishida N, Sugiyama M, Kurosaki M, Matsuura K, Sakamoto N, Nakagawa M, Korenaga M, Hino K, Hige S, Ito Y, Mita E, Tanaka E, Mochida S, Murawaki Y, Honda M, Sakai A, Hiasa Y, Nishiguchi S, Koike A, Sakaida I, Imamura M, Ito K, Yano K, Masaki N, Sugauchi F, Izumi N, Tokunaga K, Mizokami M: Genome-wide association of IL28B with response to pegylated interferon-α and ribavirin therapy for chronic hepatitis C. Nat Genet 2009;41:1105–1109.
  19. Murakami T, Enomoto N, Kurosaki M, Izumi N, Marumo F, Sato C: Mutations in nonstructural protein 5A gene and response to interferon in hepatitis C virus genotype 2 infection. Hepatology 1999;30:1045–1053.
  20. Akuta N, Suzuki F, Hirakawa M, Kawamura Y, Yatsuji H, Sezaki H, Suzuki Y, Hosaka T, Kobayashi M, Kobayashi M, Saitoh S, Arase Y, Ikeda K, Kumada H: Association of amino acid substitution pattern in core protein of hepatitis C virus genotype 2a high viral load and virological response to interferon-ribavirin combination therapy. Intervirology 2009;52:301–309.
  21. Tsai YH, Kuang WF, Lu TY, Kao JH, Lai MY, Liu CJ, Chen PJ, Hwang LH: The non-structural 5A protein of hepatitis C virus exhibits genotypic differences in interferon antagonism. J Hepatol 2008;49:899–907.
  22. Macdonald A, Harris M: Hepatitis C virus NS5A: tales of a promiscuous protein. J Gen Virol 2004;85:2485–2502.
  23. Moradpour D, Evans MJ, Gosert R, Yuan Z, Blum HE, Goff SP, Lindenbach BD, Rice CM: Insertion of green fluorescent protein into nonstructural protein 5A allows direct visualization of functional hepatitis C virus replication complexes. J Virol 2004;78:7400–7409.
  24. Appel N, Pietschmann T, Bartenschlager R: Mutational analysis of hepatitis C virus nonstructural protein 5A: potential role of differential phosphorylation in RNA replication and identification of a genetically flexible domain. J Virol 2005;79:3187–3194.
  25. Yuan HJ, Jain M, Snow KK, Gale Jr M, Lee WM: Evolution of hepatitis C virus NS5A region in breakthrough patients during pegylated interferon and ribavirin therapy. J Viral Hepat 2009;17:208–216.
  26. Enomoto N, Maekawa S: HCV genetic elements determining the early response to peginterferon and ribavirin therapy. Intervirology 2010;53:66–69.
  27. Hughes M, Griffin S, Harris M: Domain III of NS5A contributes to both RNA replication and assembly of hepatitis C virus particles. J Gen Virol 2009;90:1329–1334.
  28. Appel N, Zayas M, Miller S, Krijnse-Locker J, Schaller T, Friebe P, Kallis S, Engel U, Bartenschlager R: Essential role of domain III of nonstructural protein 5A for hepatitis C virus infectious particle assembly. PLoS Pathog 2008;4:e1000035.
  29. Masaki T, Suzuki R, Murakami K, Aizaki H, Ishii K, Murayama A, Date T, Matsuura Y, Miyamura T, Wakita T, Suzuki T: Interaction of hepatitis C virus nonstructural protein 5A with core protein is critical for the production of infectious virus particles. J Virol 2008;82:7964–7976.
  30. Gale M Jr, Foy EM: Evasion of intracellular host defence by hepatitis C virus. Nature 2005;436:939–945.