Characterization of potential antiviral resistance mutations in hepatitis B virus reverse transcriptase sequences in treatment-naïve Chinese patients
Introduction
Chronic hepatitis B virus (HBV) infection remains a serious public health problem in China (Chinese Medical Association, 2007). Although antiviral therapy using nucleos(t)ide analogues (NAs) is known as an effective control measure (Leung et al., 2001, Marcellin et al., 2003), the obstacles are limited kinds of NAs available and inevitable emergence of antiviral resistance conferred by viral mutations during long-term treatment (Locarnini et al., 2004, Locarnini and Mason, 2006). Thus, understanding of the mechanisms of the evolutionary basis of the drug resistance mutants is of importance for prevention and control of them.
Anti-HBV NAs approved currently in China include lamivudine (LMV), adefovir dipivoxil (ADV), entecavir (ETV) and telbivudine (LdT). They exclusively target the activity of the reverse transcriptase (RT) of HBV polymerase (Locarnini and Mason, 2006, Chinese Medical Association, 2007). In line with this, all reported potential antiviral resistance mutations are localized into the RT region (Locarnini and Mason, 2006, Lok et al., 2007). It is well-known that nucleos(t)ide-selected classical antiviral resistance mutations with in vitro phenotypic confirmation are classified into two categories (Locarnini and Mason, 2006, Lok et al., 2007). The first category contains primary drug resistance mutations resulting in amino acid (AA) substitutions directly reducing susceptibility to monotherapy or even a group of multiple antiviral agents, for example, rtM204I refractory to LMV and LdT (Shaw et al., 2006, Langley et al., 2007, Lok et al., 2007, Locarnini, 2008). The other category is referred to as secondary/compensatory mutations contributing to AA substitutions restoring functional defects in RT activity associated with primary drug resistance, for instance, rtV173L combined with rtM204V + rtL180M (Lai et al., 2005, Lok et al., 2007).
Besides, the AA changes at some other positions of RT have been reported in NA resistance (NAr) studies. Firstly, several types of AA changes have been reported to be selected during prolonged NA therapy and potentially associated with NAr or replication compensation, although the functional relevancies have not been clarified thoroughly in vitro or in vivo, for example, rtV191I and rtS213T (Fu and Cheng, 1998, Ogura et al., 1999, Pichoud et al., 1999, Torresi et al., 2002, Wakil et al., 2002, Yang et al., 2002, Ciancio et al., 2004, Colonno et al., 2006, Sheldon et al., 2006, Sheldon et al., 2007, Yim et al., 2006, Kim et al., 2008, Nguyen et al., 2008, Svicher et al., 2009). This group of AA substitutions was named as “putative NAr mutations” in this study. Secondly, other types of AA substitutions have been reported in NA-naïve patients but their relationships with antiviral resistance development have not been clarified yet. In this study we called them “pretreatment mutations” (Ogura et al., 1999, Kim et al., 2008). Thus, totally we discovered 42 potential NAr AA positions scattered in the full-length RT sequences reported so far and grouped them into 4 categories, i.e. primary drug resistance mutation (Category 1), secondary/compensatory mutation (Category 2), putative NAr mutation (Category 3) and pretreatment mutation (Category 4) (Table 1).
Puzzled by so many reported potential NAr mutations, we wondered how often they presented as naturally occurring polymorphic mutations in NA-naïve chronic hepatitis B (CHB) patients and whether those belonging to Categories 3 and 4 (Table 1) contributed to the antiviral resistance property of HBV. As we know, many of the previous investigations on NA-naïve patients focused on classical primary and secondary mutations and on A- or D-genotype infections, and the results on the presence of drug-resistant mutations as natural genome variability were different among various studies (Kobayashi et al., 2001, Matsuda et al., 2004, Ramezani et al., 2008). Therefore, this study aims to characterize the AA substitutions at the aforementioned 42 potential NAr mutation positions in HBV RT sequences in a cohort of 192 Chinese NA-naïve CHB patients commonly with B- or C-genotype infections.
Section snippets
Patients
The study was approved by the Ethics Committee of Peking University Health Science Center in accordance with the Helsinki Declaration. Informed consent was obtained from each patient. One hundred and ninety-two Chinese CHB patients from outpatient clinics in 4 hospitals were consecutively enrolled in a period from December 2007 to August 2008 with the inclusion criteria of hepatitis B surface antigen (HBsAg) positive, HBV DNA positive, as well as LMV, ADV, ETV and LdT treatment-naïve. Exclusion
Patient characteristics
HBV RT sequences were determined in all 192 patients with 28.65% (55/192) B-genotype and 71.35% (137/192) C-genotype infections, respectively (P < 0.0001), with a prevalent characteristic representative of HBV genotype distribution in northern China (Chinese Medical Association, 2007). HBeAg positive rate was 71.35% (137/192). The main characteristics of the HBeAg-positive and -negative patients were compared in Table 2, showing that HBeAg-negative patients were significantly older (P < 0.0001) and
Discussion
With the wide use of NAs, potential NAr mutation positions in HBV RT region have been reported increasingly but presented with many puzzles nowadays (Zoulim et al., 2009). Based on publication reviewing, various potential NAr mutation positions in RT region reported so far were grouped into 4 categories in this study (Table 1). Similar to some previous reports (Pollicno et al., 2007, Nguyen et al., 2008), the primary drug resistance mutations and secondary mutations were not found in this
Acknowledgements
This study was supported by the financial grants from Chinese National Key Basic Research Project (2005CB523104) and Major Science and Technology Special Project of China Eleventh Five-year Plan (2008ZX10002-004 and 2009ZX10004-314).
References (41)
- et al.
Pooled analysis of amino acid changes in the HBV polymerase in patients from four major adefovir dipivoxil clinical trials
J. Hepatol.
(2007) - et al.
Is hepatitis B virus subtype testing useful in predicting virological response and resistance to lamivudine?
J. Hepatol.
(2002) - et al.
Role of additional mutations outside the YMDD motif of hepatitis B virus polymerase in L(−)SddC (3TC) resistance
Biochem. Pharmacol.
(1998) - et al.
Hepatitis B virus quasispecies in the polymerase gene in treatment-naïve chronic hepatitis B patients
J. Hepatol.
(2008) - et al.
Detection of YMDD motif mutations in some lamivudine-untreated asymptomatic hepatitis B virus carriers
J. Hepatol.
(2001) - et al.
A 1-year trial of telbivudine, lamivudine, and the combination in patients with hepatitis B e antigen-positive chronic hepatitis B
Gastroenterology
(2005) - et al.
Extended lamivudine treatment in patients with chronic hepatitis B enhances hepatitis B e antigen seroconversion rates: results after 3 years of therapy
Hepatology
(2001) - et al.
Cellular and virological mechanisms of HBV drug resistance
J. Hepatol.
(2006) - et al.
Rate of YMDD motif mutants in lamivudine-untreated Iranian patients with chronic hepatitis B virus infection
Int. J. Infect. Dis.
(2008) - et al.
HBV drug resistance: mechanisms, detection and interpretation
J. Hepatol.
(2006)
Nomenclature for antiviral-resistant human hepatitis B virus mutations in the polymerase region
Hepatology
The profile of mutational clusters associated with lamivudine resistance can be constrained by HBV genotypes
J. Hepatol.
Restoration of replication phenotype of lamivudine-resistant hepatitis B virus mutants by compensatory changes in the “fingers” subdomain of the viral polymerase selected as a consequence of mutations in the overlapping S gene
Virology
Resistance surveillance in chronic hepatitis B patients treated with adefovir dipivoxil for up to 60 weeks
Hepatology
Guideline on prevention and treatment of chronic hepatitis B in China
Chin. Med. J. (Engl)
Comparisons of the HBV and HIV polymerase, and antiviral resistance mutations
Antivir. Ther.
Identification of HBV DNA sequences that are predictive of response to lamivudine therapy
Hepatology
Entecavir resistance is rare in nucleoside naive patients with hepatitis B
Hepatology
Hepatitis B virus containing the I233V mutation in the polymerase reverse-transcriptase domain remains sensitive to inhibition by adefovir
J. Infect. Dis.
EASL International Concensus Conference on Hepatitis B. 13-14 September 2002, Geneva, Switzerland. Consensus statement
J. Hepatol.
Cited by (86)
Resistant mutations within the hepatitis B virus reverse transcriptase sequence in treatment failure patients with chronic HBV infection in Vietnam
2023, Journal of Global Antimicrobial ResistanceThe modulation of HBsAg level by sI126T is affected by additional amino acid substitutions in the S region of HBV
2019, Infection, Genetics and Evolution