Review
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World J Med Genet. May 27, 2014; 4(2): 19-26
Published online May 27, 2014. doi: 10.5496/wjmg.v4.i2.19
Molecular epidemiology of hepatitis B virus in Asia
Takako Utsumi, Yoshihiko Yano, Hak Hotta
Takako Utsumi, Indonesia-Japan Collaborative Research Center for Emerging and Re-emerging Infectious Diseases, Institute of Tropical Disease, Airlangga University, Surabaya 60115, Indonesia
Takako Utsumi, Yoshihiko Yano, Hak Hotta, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
Author contributions: All the authors contributed substantially to the conception and design, acquisition of data described in the articles, drafting the article, designing the figures of the manuscript, revising it critically for important intellectual content, and gave approval for the final version to be published.
Supported by The Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan; The Ministry of Health, Labour and Welfare, Japan, and a SATREPS Grant from Japan Science and Technology Agency and Japan International Cooperation Agency
Correspondence to: Hak Hotta, MD, PhD, Center for Infectious Diseases, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan. hotta@kobe-u.ac.jp
Telephone: +81-78-3825500 Fax: +81-78-3825519
Received: December 17, 2013
Revised: February 25, 2014
Accepted: March 13, 2014
Published online: May 27, 2014
Processing time: 152 Days and 19.6 Hours
Abstract

Although safe and effective vaccines against hepatitis B virus (HBV) have been available for three decades, HBV infection remains the leading cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) worldwide, especially in Asian countries. HBV has been classified into at least 9 genotypes according to the molecular evolutionary analysis of the genomic DNA sequence and shown to have a distinct geographical distribution. Novel HBV genotypes/subgenotypes have been reported, especially from Southeast Asian countries. The clinical characteristics and therapeutic effectiveness of interferon (IFN) and nucleos(t)ide analogues vary among different HBV genotypes. Mutations at T1653C in subgenotype C2 from Japan and South Korea, C/A1753T and C1858T in subgenotype C1 from Vietnam, and C1638T and T1753V in subgenotype B3 from Indonesia were reported to be associated with advanced liver diseases including HCC. Genotype distribution in Japan has been changed by an increasing ratio of subgenotype A2 in chronic hepatitis B. While a large number of epidemiological and clinical studies have been reported from Asian countries, most of the studies were conducted in developed countries such as Taiwan, China, South Korea and Japan. In this review, the most recent publications on the geographical distribution of genetic variants of HBV and related issues such as disease progression and therapy in Asia are updated and summarized.

Keywords: Hepatitis B virus; Genotype; Subgenotype; Molecular epidemiology; Asia; Pathogenicity; Drug resistance

Core tip: Chronic hepatitis B virus (HBV) infection usually progresses to liver cirrhosis and hepatocellular carcinoma. The variation of the HBV genotype is related to the geographical distribution. Also, the clinical characteristics and therapeutic effectiveness of interferon and nucleos(t)ide analogue vary among different HBV genotypes. A large number of epidemiological and clinical studies have been reported from Asian countries. However, most of the studies were conducted in developed countries such as Taiwan, China, South Korea and Japan. In this review, epidemiologically and clinically important aspects of HBV genotypes/subgenotypes found in East and Southeast Asian countries are updated and summarized.