Journal of Medical Virology 85:1155–1162 (2013) Hepatitis B Virus Reverse Transcriptase Mutations in Treatment Naı ¨ve Chronic Hepatitis B Patients Bhupesh Singla, 1 Anuradha Chakraborti, 2 Bal Krishan Sharma, 1 Shweta Kapil, 1 Yogesh K. Chawla, 1 * Sunil K. Arora, 3 Ashim Das, 4 Radha K. Dhiman, 1 and Ajay Duseja 1 1 Departments of Hepatology, Post Graduate Institute of Medical Education and Research, Chandigarh, India 2 Experimental Medicine and Biotechnology, Post Graduate Institute of Medical Education and Research, Chandigarh, India 3 Immunopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India 4 Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India Mutations in the reverse transcriptase (RT) region of the hepatitis B virus (HBV) genome lead to decreased susceptibility to nucleos(t) ide analogs approved for treatment of HBV infection. The aim of this study was to detect and analyze pre-existing HBV RT mutations in treatment naı¨ve patients with chronic hepatitis B. Seventy one chronic HBV treatment naı¨ve patients were enrolled from January 2009 to June 2011. HBV RT sequence analysis was done by using direct bidirectional sequencing of semi-nested PCR products. HBV genotypes were determined by multiplex PCR. Genotype D was found in 64 patients (90.1%) followed by genotype C and A which were present in 5 (7.0%) and 2 (2.8%) patients respectively. The results of the RT sequence analysis showed mutations in 34 (47.9%) patients. The rtH248N mutation was the most common mutation, accounting for 47.1% patients. Other common mutations included rtD263E/S, rtM129L, rtF122L/V/I, rtS135Y/H, rtQ149K, rtL91I, rtH126R, rtC256S/G, rtY257W, rtS259T and rtE271D, which were present in 26.5% (9/34), 29.4% (10/34), 20.6% (7/34), 20.6% (7/34), 20.6% (7/34), 17.6% (6/34), 14.7% (5/34), 14.7% (5/34), 11.8% (4/34), 11.8% (4/34) and 11.8% (4/34) patients respectively. The known primary drug resis- tance mutations were found in 3 (8.8%) pa- tients. The present study shows the presence of RT amino acid substitutions in treatment- naı ¨ve patients with chronic hepatitis B, which may decrease susceptibility to available oral antiviral drugs. On the basis of the finding of this study, genotypic testing is recommended before the start of therapy in naı¨ve patients, so that suitable antiviral drugs can be prescribed. J. Med. Virol. 85:1155–1162, 2013. # 2013 Wiley Periodicals, Inc. KEY WORDS: hepatitis B virus; chronic hepa- titis B; reverse transcriptase; genotype; nucleos(t)ide ana- logs; semi-nested PCR INTRODUCTION Despite the availability of hepatitis B virus (HBV) vaccines, HBV infection remains a major health problem, causing acute and chronic liver disease. If left untreated, chronic HBV infection may lead to complications such as cirrhosis and hepatocellular carcinoma. Currently, two types of drugs are ap- proved for the treatment of chronic HBV infection; immunomodulatory agents (interferon alpha [IFN-a] and pegylated interferon [Peg-IFN]) and oral nucleos (t)ide analogues (lamivudine [LMV], adefovir [ADV], tenofovir [TNF], telbivudine [LdT], and entecavir [ETV]) [Marcellin et al., 2003; Chang et al., 2006; Lai et al., 2006, 2007]. The major goals of antiviral drug therapy include (i) achieving hepatitis B e antigen (HBeAg) seroconversion; (ii) achieving undetectable levels of HBV DNA by real-time polymerase chain reaction (PCR); and (iii) persistent normalization of serum alanine transaminase (ALT) levels. HBV Grant sponsor: Indian Council of Medical Research (ICMR), New Delhi, India; Grant numbers: ICMR No: VIR/28/2010-ECD-I, 3/1/3JRF-2008/MPD. The authors declare that they have no competing interests.  Correspondence to: Prof. Yogesh K. Chawla, Department of Hepatology, Second Floor, D-Block Nehru Hospital, PGIMER, Chandigarh. E-mail: ykchawla@gmail.com Accepted 26 February 2013 DOI 10.1002/jmv.23608 Published online in Wiley Online Library (wileyonlinelibrary.com).  C 2013 WILEY PERIODICALS, INC.