Evolution of wild type and mutants of the YMDD motif of hepatitis B virus polymerase during lamivudine therapy

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Journal of Gastroenterology and Hepatology

Volume 18 Issue 12 Page 1353 - December 2003

doi:10.1046/j.1440-1746.2003.03176.x

Evolution of wild type and mutants of the YMDD motif of hepatitis B virus

polymerase during lamivudine therapy

XINXIN ZHANG*,, CHUANMIAO LIU*, QIMING GONG*, SHENYING ZHANG*, DONGHUA

ZHANG*, ZHIMENG LU* AND YUAN WANG

Abstract

Background and Aim: Long-term lamivudine treatment for chronic hepatitis B

virus (HBV) infection induces the emergence of lamivudine resistant HBV YMDD

mutant strains. The aim of the present study was to observe the clone

evolution of YMDD wild type and mutant strains in pretreatment and

post-treatment samples during lamivudine therapy and analyze their clinical

significance.

Methods: Ten serum samples (five before and five after 48 weeks of therapy)

obtained from five patients chronically infected with HBV and treated with

lamivudine were studied. Part of the HBV polymerase gene flanking the YMDD

motif was sequenced after polymerase chain reaction (PCR) amplification.

Meanwhile, 20-24 clones were selected at random from each sample and YMDD

wild type and mutant strains were detected by real-time fluorimetry PCR

established in our laboratory.

Results: The YMDD mutants were not detectable in all five patients before

treatment and were found in four patients after 48 weeks of therapy by

sequencing directly on PCR products. Analysis of individual clones showed

that the ratios of mutant strains in each of the five patients were 0, 9.5,

0, 4.5 and 5.6%, respectively, before therapy and 100, 100, 65, 100 and 0%,

respectively, after 48 weeks of therapy. M552I was detected before therapy

in one patient but M552V became the domain strain after therapy. Until 52

weeks of therapy, serum HBV DNA and alanine aminotransferase (ALT)

breakthrough were found in two of the four patients with YMDD mutations. The

fifth patient experienced breakthrough of ALT but HBV DNA remained

undetectable.

Conclusions: The mutant strains of YMDD motif of HBV polymerase could be

found in patients before lamivudine treatment, indicating that antiviral

therapy allows the rapid selection of resistant strains. The replication

ability of the M552V mutant strain might be stronger than that of the M552I

mutant strain.

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Accepted for publication 17 April 2003.

Affiliations

*Department of Infectious Diseases, Rui Jin Hospital, Shanghai Second

Medical University, and

State Key Laboratory of Molecular Biology, Institute of Biochemistry and

Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy

of Sciences, Shanghai, China

Correspondence

Dr Xinxin Zhang, Department of Infectious Diseases, Rui Jin Hospital,

Shanghai Second Medical University, Shanghai 200025, China. Email:

zxinx2001@...

To cite this article

ZHANG, XINXIN, LIU, CHUANMIAO, GONG, QIMING, ZHANG, SHENYING, ZHANG,

DONGHUA, LU, ZHIMENG & WANG, YUAN (2003)

Evolution of wild type and mutants of the YMDD motif of hepatitis B virus

polymerase during lamivudine therapy.

Journal of Gastroenterology and Hepatology 18 (12), 1353-1357.

doi: 10.1046/

j.1440-1746.2003.03176.x