Table 1.

HBV ORFs and proteins

ORF	Protein	Function/role in pathogenesis of HBV infection
P	Viral polymerase	DNA polymerase, reverse transcriptase, and RNase H activity; contains functional domains essential for encapsidation of the pregenomic RNA
S	HBV surface proteins	Pre-S1 protein plays a key role in attachment of the virus to the hepatocyte (200)
C	Core protein	Forms the capsid and encapsidates HBV nucleic acids
	HBeAg	Biological role is poorly understood; however, strong epidemiological associations between HBeAg and HBV DNA level (53) and the risk of progression to hepatocellular carcinoma (290) are well documented
X	HBx protein	Transactivator of viral regulatory elements and host gene promoters (60, 248), essential for establishment of infection in vivo (300), potential role in hepatocarcinogenesis (60)