HEPATITIS B VIRUS

Structure & Property	Transmission	Pathogenesis	Clinical findings	Laboratory diagnosis	Treatment	
Family: hepadnavirus

Genome: partially double-strand DNA

Size: 42nm

Icosahedral nucleocapsid

Enveloped virion.

Contains DNA-dependent DNA polyermase.

EM reveals 3 particles:
- virion particle
- spheres
- filaments

HBsAg: surface antigen
HBcAg: core antigen
HBeaAg: e antigen

One serotype with 4 subtypes	Drug abusers: infection transmitted by sharing of syringes.

Sexual transmission

Pregnancy: spread from mother to child during birth or breast feeding.

Haemophiliacs: used to be of high risk because of contaminated factor VIII.	After entering blood, virus infects hepatocytes, causing necrosis and inflammation.

Immune attack against viral antigens on infected hepatocytes is mediated by cytotoxic T cells.

Lifelong immunity mediated by antibody against HBsAg.	Incubation period: 10-12 weeks.

Many HBV infections are asymptomatic, detected only by presence of antibody to HBsAg.

More severe than hepatitis A.

Complications:
- artharalgias
- immune-complex glomerulonephritis
- vasculitis

Chronic persistent hepatitis: benign and self-limiting.

Chronic active hepatitis:
- in 3% of all cases
- serious disease, with liver dysfunction and cirrhosis.

High incidence of liver cancer with hepatitis B.	Diagnosis:
- acute infection: test by LIESA for HBsAg, if present test for anti-HBc IgM and for HBeAg.
- HBsAg is detectable during acute disease, but falls to undetectable levels during covalescence.
- prolonged presence of HBsAg indicates carrier state and risk of chronic hepatitis.
- past infection: anti-HBc IgG without IgM.
- anti-HBeAg indicates low infectivity.
- anti-HBs IgG indicates immunity after infection.	Hepatitis B vaccine:
- contains HBsAg, prepared by recombinant DNA technology, adsorbed onto aluminum hydroxide.
- for those at special risk: health care workers, close contacts of carriers, haemophiliacs.
- injected intramuscularly into deltoid in 3 doses; two, 1 month apart, third, 6 months after the first.
- babies born to HBsAg-positive mothers should be immunized a few hours of birth.

Passive immunization:
- hepatitis B-specific immunoglobulin gives partial but significant protection against disease.
- used in people exposed in a single episode involving high risk of infection.

Interferon-alpha reduces viral replication in hepatitis B.