Fig 1.

Primer and probe position of W4P/R detection for the RT-PCR method. The 3 types of hepatitis B virus (HBV) pre-S1 variants in the 4th codon (wild type [TGG], W4P [CCG], and W4R [CGG]) and primer and probe positions designed for the detection of 3 types of hepatitis B virus pre-S1 variants. Arrows indicate the primer directions. Underlining indicates the probe positions. The numbers indicate the nucleotide position on the pre-S1 gene sequence. Bases in bold type denote bases different from the ones of the consensus sequence. Shading indicates the variants at the 4th codon of the pre-S1 gene. The amino acid sequence is shown using the one-letter amino acid symbols.