on 4.2.09 with 0 comments

  • STRUCTURE: Circular DNA, partially double-stranded, partially single-stranded.

  • REPLICATION: DNA replication with an RNA intermediate, utilizing Reverse Transcriptase.

    • Upon entry of virus into cell, the viral DNA-Polymerase repairs the single-stranded end of the molecule, forming a supercoiled dsDNA genome.

    • Host-cell RNA Polymerase then forms mRNA's from the DNA genome:

      • Full-length (+) mRNA

      • Subgenomic mRNA's, from which structural and non-structural proteins are made.

    • The full-length mRNA gets enclosed around a core-capsid.

    • Inside the core, viral DNA Polymerase then serves as a Reverse Transcriptase, to make DNA out of the full-length mRNA.

      • cDNA is formed, forming a DNA:RNA hybrid. The RNA is then degraded, and then a complementary DNA strand is formed, making dsDNA.

    • dsDNA progeny genome is then put out of cell, taking outer envelope with it as it leaves host cell.



      • Dane Particle: The entire infectious virion, including nucleocapsid, core antigens, and surface antigens.

      • HBV Surface Antigen (HBsAg): 4 phenotypes, useful for epidemiology: adw, ayw, adr, ayr.

    • TRANSMISSION: Sexual, fecal-oral, or intravenous or by exposure to blood products.





Hepatitis-B Surface Antigen


Surface antigen present on viral envelope. Its presence indicates acute HBV infection.

Antibodies to Hepatitis-B Surface Antigen


Antibodies to the surface antigen are not detectable during acute infection even though they are being made, because there is way more antigen and it sops it all up, making it undetectable in the blood.

Presence of Anti-HBs indicates immunity to HBV or previous vaccination for HBV.

Hepatitis-B Core Antigen


Its presence indicates acute HBV infection.

Antibodies to Hepatitis-B Core


Its presence indicates acute or chronic HBV infection. Whether it is acute or chronic depends on whether IgM is present or IgG.

Hepatitis B e Antigen


This is the hepatitis viral polymerase and is present during acute infection.

Antibodies to Hepatitis-B e Antigen.


These aren't usually tested but are present during acute or chronic infection.

Antibodies to Hepatitis-A


Indicates acute infection of Hepatitis-A. There is no chronic Hepatitis-A infection.

Antibodies to Hepatitis-C


Indicates acute or chronic infection of Hepatitis-C.

    • MANIFESTATIONS: Cell-mediated immunity is responsible for the symptoms.

      • Acute Infection: Acute infection may or may not lead to persistent infection. HBsAg and Anti-HBc will show up in blood.

      • Chronic (Persistent) Infection: Hepatitis-B virus is still being produced. 5-10% of HBV can be expected to develop an HBV carrier state.

        • Vasculitis, arthralgia, rash, and kidney problems can all result from immune-complex disease involving immune complexes of the HBsAg.

        • Primary Hepatocellular Carcinoma: 80% of primary hepatomas are due to HBV infection.

    • Other Hepatitis Infections:

      • Hepatitis-A (HAV): Enterovirus-72

      • Hepatitis-C (HCV): Flavivirus.

      • HEPATITIS-D (Delta Agent): Hepatitis-B is required in order for this virus to infect.

        • STRUCTURE: ss circular RNA that resembles an intron. RNA encodes the delta antigen, which is in turn enveloped by the HBsAg.

        • MANIFESTATIONS: Should be tested for as co-infection with HBV. Course is more severe and prognosis is poorer when Delta agent is present.

      • Hepatitis-E (HEV): Calicivirus

    • VACCINE: It consists of the Hepatitis-B Surface Antigen, to which we then make protective antibodies. Thus presence of Anti-HBs is indicative of previous vaccination.

Category: Microbiology Notes



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