Hepatitis is an inflammatory process in the liver characterized, clinically and histologically, by evidence of diffuse or pathcy hepatocellular necrosis affecting all lobules. Hepatitis B is an infectious disease caused by the hepatitis B virus. Hepatitis B virus (HBV) infection can cause a spectrum of acute and chronic liver disease, ranging from mild, progressive liver disease, asymptomatic infection to severe.
Hepatitis B Epidemiology
More than 2 billion people worldwide have been infected with HBV, and estimated 350 million of those people have become chronic carriers of the virus. Over three quarters of these may be of Asian ethnicity. Approximately 900.000 to 1 million people in Europe and 140.000 to 320.000 people in the USA become infected with HBV each year.
Hepatitis B Transmission, Hepatitis B virus (HBV) is present in blood, saliva, and semen of infected individuals, with highest concentration of HBV found in blood and serous fluids. In order to reach the liver, HBV must gain access to the circulation by crossing the skin or mucous membranes. Major modes of Hepatitis B transmission: include:
- Vertical (from mother to child perinatally)
- Sexual contact
- Other physical contact with an infected individual
- Parenteral/percutaneous inoculation (eg. contact with contaminated syringes, acupuncture needles, or tatoo instruments)
In Hepatitis B endemic regions such as Asia and Africa, HBV infection is often acquired early in life, either vertically from perinatal transmission or horizontally from contact with other infected individuals.
What is Hepatitis B Virus, Hepatitis B Virus is a small, enveloped virus classified as a member of the hepadnavirus family. Although HBV has several close relatives among animal viruses, there are no other human viruses similar to hepatitis B virus, including other viruses that cause hepatitis. The DNA genome of Hepatitis B virus contains only 4 genes that encode viral proteins. These include the surface (S) gene, which encodes the 3 forms of HBsAg; the pre-core/core (PC/C) gene, which encodes core protein and hepatitis B e antigen (HBeAg); the X gene, which encodes the X proteins; and the polymerase (P) gene, which encodes the viral DNA polymerase.
Some tips to reduce of getting Hepatitis B infection are avoiding the use of unnecessary transfusion, routine screening of all blood for HBsAg, get vaccinated for HBV Vaccine, and avoiding high risk hepatitis b behaviors.
Some tips to reduce of getting Hepatitis B infection are avoiding the use of unnecessary transfusion, routine screening of all blood for HBsAg, get vaccinated for HBV Vaccine, and avoiding high risk hepatitis b behaviors.
Hepatitis B Virus Replication
Hepatitis B virus utilises a novel replication strategy, which is related to that of retroviruses such as human immunodeficiency virus (HIV), in that reverse transcription of RNA into DNA is a critical step in the replication cycle. However, unlike retroviruses, Hepatitis B virus DNA is not integrated into the host cell DNA during replication. After an infectious HBV particle binds to and enters an hepatocyte, HBV DNA enters the cell nucleus and is converted into covalently closed circular DNA (cccDNA). cccDNA is highly stable an an important intermediate in Hepatitis B Virus replication, acting as template for transcription of RNA copies. The largest of RNA copies is called pregenomic mRNA, is transported to the cytoplasm of the cell, and has function to carrying genetic information to direct the synthesis of some viral proteins and as template for synthesis of new Hepatitis B virus DNA. Smaller HBV mRNA transcripts participate in synthesis of other viral proteins.
After viral protein systhesis has begun, HBV core protein, Pregenomic mRNA and Hepatitis B virus DNA polymerase assemble to form new virus particles. The pregenomic mRNA within each particle is then reverse transcribed by HBV DNA polymerase to form minus sense viral DNA with concomitant degradation of the RNA template. The minus sense DNA then acts as template for synthesis of plus sense DNA. While HBVDNA synthesis is proceeding, the viral particles remain within the cell and contribute their viral DNA for replenisment of nuclear stores of covalently closed circular DNA (cccDNA).
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