Hepatitis B Virus

Hepatitis B Virus

Virology:


_ Family: Hepadnaviridae
_ The complete virus particle is 42-nm in diameter
_ Enveloped, spherical
_ Consists of outer envelope containing HBs-Ag particles
_ And internal nucleocapsid (core) containing ds-DNA genome
_ The core (nucleocapsid) consists of two antigens HBc-Ag
and HBe-Ag.
_ The serum of infected individual shows large number of free
spherical HBs-Ag particles.
_ Some of HBs-Ag particles are linked together to take the
form of filaments.




Transmission:


_ Parenterally
_ Direct exposure to infected blood and body secretions
_ Use of contaminated needles, syringes, surgical and
dental instruments.
_ Use of contaminated instruments in the practice of
Tatooing and folk medicine.
_ Sharing contaminated razors or tooth brushes
_ From mother to child:
_ Mainly perinatally during labour and delivery
_ Sexually
_ By having sexual contact with infected person.





Inoccupation period


_ 60 days

_ Types of infection:

1. Acute hepatitis B with full recovery
2. Chronic hepatitis B infections
3. Fulminant hepatitis

_ Acute hepatitis B:

_ Approximately 90% of infected individuals develop
acute hepatitis B and recover completely.
_ Acute hepatitis B is characterized by the presence of
HBs-Ag in the blood fore less than 6-months.
_ HBs-Ag is the first marker that appear in circulation and
persists for 4-12 weeks (less than 6 months), then
disappears.





_ Acute hepatitis B: ()




_ HBe-Ag is the second marker that appear in circulation
_ It appears after HBs-Ag and disappears before the
surface antigen.
_ Antibody to the core (anti-HBc) is the first Ab that
appear in the blood and usually persists for several years.
_ With the disappearance of HBe from circulation, Anti-
HBe appears and usually persists for several weeks to
months.
_ Anti-HBs is the last marker that appears in the blood. It
appears few weeks after disappearance of HBs-Ag.
_ Anti-HBs usually persists for several years
_ It is the only marker that indicates immunity to HBV
infection.






Chronic hepatitis B:

_ Characterized by the presence of HBsAg in the blood fore
more than 6-months.
_ About 5-10% of acutely infected adults, 50% of infected
children and 90% of infected neonates will become
chronically infected.
_ Chronic hepatitis B varies from asymptomatic, mild liver
disease to severe chronic hepatitis B
_ About 20-30% of all chronic hepatitis B patients will
progress to cirrhosis.



_ Chronic hepatitis has three phases

_ The replicative phase
_ The inflammatory phase
_ And the inactive phase







The replicative phase:

_ The patient is positive for both HBe-Ag and HBV-DNA
_ ALT is normal or nearly normal
_ Liver biopsy is relatively inactive
The inflammatory phase:
_ For unknown reasons, patients may enter this phase
_ The immune system attacks those hepatocytes harboring
the virus
_ ALT elevated
_ Liver biopsy shows damage to hepatocytes
_ Decline in the HBV-DNA in the blood






The inactive phase:


_ The patient successfully clear viral replication
_ Normal ALT
_ Clearance of HBe-Ag and anti-HBe will form
_ Based on the result of liver biopsy patients with chronic
hepatitis are classified into three groups


1. Mild chronic hepatitis


2. Moderate to severe chronic hepatitis


3. Severe chronic hepatitis


_ Confluent necrosis


_ Much more likely to progress to cirrhosis








Hepatitis B vaccine:


_ It contains highly purified preparation of HBsAg
particles.
_ HBs-Ag particles produced by genetic engineering in
yeast
_ It is a recombinant and subunit vaccine
_ It is not live attenuated or killed vaccine
_ The vaccine is administered in three doses at 0,1 & 6
months
_ The vaccine is protective







Hepatitis B Markers:


1. HBsAg
_ Marker of infection
2. HBeAg
_ Marker of active virus replication in the liver
_ High level of HBV-DNA in the patient serum
_ Highly infectious
3. Anti-HBe
_ Marker of low infectivity
_ No active virus replication
_ Less infectious






Hepatitis B Markers:


4. Anti-HBs
_ Marker of immunity
_ Clearance of HBV - infection
5. Anti-HBc IgG
_ Marker of previous exposure to HBV
6. Anti-HBc IgM
_ Marker of the acute phase of HBV infection.



Hepatocellular Carcinoma (HCC):



_ One of the most common cancer in the world
_ One of the most deadly cancer if not treated
_ Hepatitis B and C viruses are the leading cause of chronic
liver diseases, cirrhosis and HCC.

Symptoms:

_ Abdominal pain
_ Abdominal swelling
_ Weight loss
_ Anorexia
_ Vomiting
_ Jaundice



Physical Examination Reveals:

_ Hepatomegaly
_ Splenomegaly
_ Ascites


Diagnosis:

_ Alfa-fetoprotein measurement with multiple CT-abdominal
scan are the most sensitive method for diagnosis of HCC.

Treatment:

_ Surgical resection and liver transplant.

Prognosis:

_ Without liver transplantation, the prognosis is poor and one
year survival is rare.