HEPATITIS B VIRUS. Presented by Group I PCL2. MEMBERS OF GROUP BAHIZI Sadallah Ug 12114376 BAMPORIKI Judith Ug 12214657 BAYINGANA Marie Eve Ug 12214674 BAZAMBAZA Philippe Ug 12215192
Presented by Group I PCL2
BAMPORIKI Judith Ug 12214657
BAYINGANA Marie Eve Ug 12214674
BAZAMBAZA Philippe Ug 12215192
BITUNGURAMYE Adam Ug 12114056
BIZIMANA Anselme UG12114504
BUGINGO JEAN Pierre Ug 12113855
BUHOLO Jael Ug12214676
BUSOMOKE Denys FabriceUg 12113988
BYIRINGIRO Jean d’ Amour Ug 12113049
CHOI Jaeseok Ug12215093`
The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenicepitopes present on its envelope proteins, and into eight genotypes (A-H) according to overall nucleotide sequence variation of the genome
The genome of HBV is a partially double-stranded circular DNA molecule
large HBsAg (containing Pre-S1, Pre-S2, and S), middle HBsAg (containing Pre-S2 and S), and small HBsAg (containing S only).
Infected hepatocytes are capable of synthesizing and secreting massive quantities of noninfective surface protein (mainly small HBsAg).
Electron microscopy of a patient's serum reveals three different types of particles: a few 42-nm virions and many 22-nm spheres and long filaments 22 nm wide, which are composed of surface antigen
There are three important modes of transmission of HBV infection:
About 5-10% of HBV infections result in chronic carrier state. The latter may be defined as persistence of HBsAg in the circulation for more than six months.
Carriers are of two types:
and become persistently infected
-The existence of HBV carriers with normal liver histology and function
-Patient with defects in cellular immune competence are more likely to remain chronically infected.
The replication cycle of HBV
DNA Genomes replicated by reverse transcription
Attachment Endocytosis Penetration Uncoating
In brief of replication:
Virion attaches to host cell
Virions are released
Virion penetrates cell and its DNA is uncoated
Late translation; capsid proteins are synthesized
Late transcription; DNA is replicated
Early transcription and translation; enzymes are synthesized
The natural course of the disease can be followed by serum markers
FIGURE 18-11( from Robbins &Cotran Pathology,8thed ) below show Sequence of serologic markers for hepatitis B viral hepatitis demonstrating (A) acute infection with resolution and (B) progression to chronic infection.
The most important laboratory test for the detection of HBV infection:
HBsAbis undetectable because it is bound in immune complexes and DNA polymerase activity is detectable during the incubation period and early in the disease, but the assay is not available in most clinical laboratories
Acute infection with hepatitis B usually does not require treatment. In rare cases, however, the infection may cause life-threatening liver failure. Patients with liver failure due to acute hepatitis B should be evaluated for liver transplantation. Small studies suggest that the drug lamivudine (Epivir) may be effective in this setting.
If a person is chronically infected with hepatitis B and has few signs or symptoms of complications, medications usually are not used. These patients are watched carefully and given periodic blood tests
The medications in current use for chronic hepatitis B include the interferons and nucleoside/nucleotide analogues
Are man-made chemicals that mimic the nucleosides and nucleotides that are used for making DNA. When the virus tries to use the analogues to make its own DNA, it is unable to make the DNA and, therefore, cannot reproduce. Examples of these agents include adefovir (Hepsera), entecavir (Baraclude), lamivudine (Epivir-HBV, Heptovir, Heptodin), telbivudine (Tyzeka) and tenofovir (Viread).
Changes in sexual practice and improved screening measures of blood products have reduced the risk of transfusion-associated hepatitis.
Hepatitis B Immune Globulin (HBIG) is a sterile solution of ready-made antibodies against hepatitis B is used
Prevention of primary infection by vaccination is an important strategy to decrease the risk of chronic HBV infection and its subsequent complications.
The vaccine is prepared from purified HbsAg produced in yeast. Vaccination induces a protective anti-HBs antibody response in 95% of infants, children, and adolescents.
A vaccine called Twinrixthat contains both HBsAg and inactivated HAV provides protection against both hepatitis B.