title: Two subtypes (subgenotypes) of hepatitis B virus genotype C: A novel subtyping assay based on restriction fragment length polymorphism.
abstract: Recently hepatitis B virus genotype C (HBV/C) has been classified into geographically typical two subtypes (subgenotypes); HBV/C1 in Southeast Asia (Cs) and HBV/C2 in East Asia (Ce). Our aim is to develop a rapid subtyping assay and to examine the virological features of these two subtypes. Based on 171 HBV/C strains retrieved from the database, 17 single nucleotides polymorphisms (SNPs) were found between two subtypes. Taking advantage of five SNPs in non-overlapping polymerase region, a restriction fragment length polymporphism method with three endonucleases was newly developed for distinguishing between HBV/Cs and HBV/Ce. The method was applied to 49 HBV/C carriers from Japan and Hong Kong. The 24 in Hong Kong were classified into HBV/Cs, and the 25 in Japan were HBV/Ce, confirmed by sequencing. Some specific mutations were detected in the encapsidation signal; precore stop mutation (A1896), accompanied by a C-to-T substitution at nt 1858, was found in HBV/Ce strains, and another precore mutation (A1898), accompanied by a C-to-T mutation at nt 1856, was found in HBV/Cs. Especially, two closely linked mutations (A1896 and A1899) in HBV/Ce could stabilize the epsilon loop structure more efficiently and influece viral replication. Hence, these virological differences between the two subtypes might influence clinical features.
authors.affiliation: Department of Clinical Molecular Informative Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Etsuro
authors.initials: E
authors.lastname: Orito
authors.forename: Man-Fung
authors.initials: MF
authors.lastname: Yuen
authors.forename: Motokazu
authors.initials: M
authors.lastname: Mukaide
authors.forename: Fuminaka
authors.initials: F
authors.lastname: Sugauchi
authors.forename: Kiyoaki
authors.initials: K
authors.lastname: Ito
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ozasa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Fuat
authors.initials: F
authors.lastname: Kurbanov
authors.forename: Ching-Lung
authors.initials: CL
authors.lastname: Lai
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizokami