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What is Which of the following HBV gene codes for HBeAg? and explain in detail?
Ans. a (Pre C+C) (Ref. Robbin's pathology 7th/ 18-D; Ananthanarayan Microbiology, 7th/ 552)HBV is a partially double-stranded deoxyribonucleic acid (DNA) virus packaged with a core protein (HBcAg) and DNA polymerase, and enclosed by envelope proteins (HBsAg). Following receptor-mediated entry into hepatocytes, the virus enters the nucleus, where its DNA is frequently integrated into the host genome.The HBV has four genes: S, P, C, and X. The S gene codes for the "major" envelope protein (HBsAg). The largest is P gene. It codes for DNA polymerase. The C gene codes for HBeAg and HBcAg. The C gene has a precore and a core region. If translation is initiated at the precore region, the protein product is HBeAg. If translation begins with the core region, HBcAg is the protein product. HBeAg is a marker of HBV replication and infectivity. The precore region is not necessary for viral replication. Precore mutants can replicate. They are readily detectable by HBV DNA in serum, but hepatitis B e antigen (HbeAg) is absent. The X gene codes for HBxAg. The product of the X gene is hepatitis B x antigen (HBxAg). It may be involved in carcinogenesis. Basal core promoter mutants cause a reduction in HBeAg production.Protein synthesis proceeds from 4 open reading frames:# Envelope proteins - Major, Middle, and Large - (HBsAg) from the -S gene, pre-Sl, and pre-S2 gene sequences;# The e antigen (HBeAg) and core protein (HBcAg) from the -C gene and pre-C gene sequence;# DNA polymerase protein from the -P gene; and# Transactivator X-protein from the -X gene.