Abstract
Hepatitis B virus (HBV) is a serious global health problem affecting
millions worldwide. Chronic HBV infection can lead to liver cirrhosis and
hepatocellular carcinoma, making it a major cause of morbidity and mortality. The
molecular basis of HBV infection and pathogenesis is complex and involves multiple
interactions between the virus and the host immune system. HBV is a partially doublestranded DNA virus replicating through reverse RNA intermediate transcription. The
virus has several proteins, including the envelope protein (HBsAg), core protein
(HBcAg), and polymerase (HBp), that play critical roles in virus entry, replication, and
assembly. The viral genome is organized into four overlapping open reading frames
(ORFs), each encoding a different viral protein. During HBV infection, the virus
initially binds to heparan sulfate proteoglycans on the cell surface, followed by binding
to specific receptors, such as the sodium taurocholate co-transporting polypeptide
(NTCP). The virus then enters the cell through endocytosis, where it is uncoated and
releases the viral DNA into the nucleus. The viral DNA is then transcribed by the host
RNA polymerase II, producing viral mRNAs translated into viral proteins. One key
factor determining the outcome of HBV infection is the host's immune response. The
innate immune response plays an important role in controlling the initial phase of HBV
infection, while the adaptive immune response, particularly the CD8+ T cell response,
is critical for the clearance of the virus. However, in some cases, the immune response
cannot clear the virus, leading to chronic infection. Understanding the molecular basis
of HBV infection and pathogenesis is critical for developing effective treatments and
vaccines. Current treatments for chronic HBV infection include nucleoside/nucleotide
analogs and interferon-based therapies, which can suppress viral replication and reduce
liver damage. However, these treatments are not curative and can have significant side
effects. Vaccination against HBV is highly effective in preventing infection and is
recommended for all individuals at risk of HBV infection.