Cousative Agent Of Hbsag

Hepatitis B is caused by hepatitis B virus (HBV) (figure 24.19a), a member of the hepadnavirus family (hepa-, referring to the liver, and -dna- "DNA"). The virus contains double-stranded DNA and has a lipid-containing outer envelope. Three important HBV antigens are (1) surface antigen (HBsAg), (2) core antigen (HBcAg), a protein of the nucleocapsid, and (3) e antigen (HBeAg), a soluble component of the viral core. HBsAg is produced during viral replication in amounts far in excess of that needed for virus production. It occurs in the bloodstream on small spheres and filaments of viral envelope material empty of DNA (figure 24.19b) in quantities often 1,000 or more times as great as complete virions. HBsAg is responsible for the ability of the virus to attach to and infect host cells; antibody to surface antigen (anti-HBsAg) confers immunity.

Genomic DNA (double-stranded with partial single strand)

Hepatitis B surface antigen (HBsAg)

Genomic DNA (double-stranded with partial single strand)

Hepatitis B surface antigen (HBsAg)

Envelope lipid (from host cell)

- Nucleocapsid (viral capsid)

Hepatitis B e antigen Hepatitis B core antigen (HBeAg) (HBcAg)

Envelope lipid (from host cell)

Hepatitis B e antigen Hepatitis B core antigen (HBeAg) (HBcAg)

- Nucleocapsid (viral capsid)

Spherical

Elongated

(a) Complete infectious virion

(b) Viral envelope particles containing HBsAg

Figure 24.19 Hepatitis B Virus Components Found in the Blood of Infected Individuals (a) Complete infectious virion. (b) Smaller spherical and elongated envelope particles lacking DNA.

Chapter 24 Alimentary System Infections

Liver cell cytoplasmic membrane

Chapter 24 Alimentary System Infections

Liver cell cytoplasmic membrane

(c) Completed viral genome transported to cell nucleus, messenger RNA and RNA copy of genome transcribed.

(e) Reverse transcription of RNA genome copy packaged in newly forming capsid; RNA strand degraded.

(c) Completed viral genome transported to cell nucleus, messenger RNA and RNA copy of genome transcribed.

(d) Reverse transcriptase and other viral proteins are translated; assembly of viral capsid begun. 9 A

(f) Synthesis of complementary DNA strand begun.

(g) Replication of second DNA strand ceases as virion buds from cell membrane.

(e) Reverse transcription of RNA genome copy packaged in newly forming capsid; RNA strand degraded.

(f) Synthesis of complementary DNA strand begun.

(g) Replication of second DNA strand ceases as virion buds from cell membrane.

Figure 24.20 Replication of Hepatitis B Virus Notice that this DNA virus employs reverse transcriptase in its replication cycle.

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Detox Diet Basics

Detox Diet Basics

Our internal organs, the colon, liver and intestines, help our bodies eliminate toxic and harmful  matter from our bloodstreams and tissues. Often, our systems become overloaded with waste. The very air we breathe, and all of its pollutants, build up in our bodies. Today’s over processed foods and environmental pollutants can easily overwhelm our delicate systems and cause toxic matter to build up in our bodies.

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