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# System prepended metadata

title: Bekir Can Altındişoğulları- 1605A005

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# Bekir Can Altındişoğulları- 1605A005
 ***Hepadnaviruses*** - "Virology by P. Saravanan, 2017." Chaper 19 P:297-315.

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# ***What are Hepadnaviruses?***
![](https://i.imgur.com/GHY8t3M.png)
:::danger
They cause the hepatit B and they get their name because of this. They have DNA genomes. They also known as hepatit B viruses (HBVs). Some of them infect mammalians and some of them infect birds. HBV also infects humans and can cause death.
Hepadnaviruses are special for two main reason. Firstly, they have small genomes to big work. Secondly their DNA genomes repliceted by RNA intermedia. So that they use revers transcription on replication. This is an uniqe stiuation for DNA viruses.
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How many people are infected by HBV, couldn't known. But World Health Organization saying their number is approximate to 300million and contributes to an estimated 700,000 deaths worldwide every year and contributes to an estimated 700,000 deaths worldwide every year.
![](https://i.imgur.com/VW8CwHP.png)
Figure shows the worldwide intensity of infected people 

Virus is present in the blood and semen of infected individuals and the modes of transmission generally parallel those for HIV transmission. There are over 50 million new HBV infections each year, the majority in babies who acquire the infection from their mothers. Many infections are thought to result from the reuse of syringes and needles for injections, mainly in the developing world.

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# ***Parts of Virion***

![](https://i.imgur.com/tYIBDQO.png)
Figure shows the HBV virion. L, M, s: large, medium, and small envelope proteins. P: polymerase.

The virion is spherical, and it is 42nm diameter.

# *DNA*
HBV's genome is made up of two strands of DNA but it is psrtly single-stranded, partly double-stranded. Even it has triple-stranded sequence at end point of genomic.

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# *Polymerase Protein*
![](https://i.imgur.com/fTxZ73H.png)
In this figure shown polymerase protein

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# *Capsid*
![](https://i.imgur.com/kXtGDLU.png)
In this figure shown capsid of virion

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# *Envelope Protein*
![](https://i.imgur.com/ETyYcg1.png)
In this figure shown envelope protein

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# ***Genom***
2 kb, the HBV genome is very small, though there are viruses with smaller genomes. There are four ORFs, from w h ich seven proteins are translated, so a large amount of coding information is packed into the small genome. The virus cleverly achieves this by using every nucleotide in the genome for protein-coding and by reading more than half of the genome in two reading frames.
![](https://i.imgur.com/xpa0l7H.png)
genome has codding proteins, it follows that all the regulatory sequences, such as promoters, are with in protein coding equences. The genome contains direct repeats of 11 nucleotides known as DR1 and DR2.
Viruse's small genome enccodes 7 protein, so it is mostly dependent on host cell functions. Host proteins plays a big role in HBV's replication enzymes, transcription  factors, and chaperones.

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# ***HBV Replication***
![](https://i.imgur.com/zAmYW9p.png)
Outline of the HBV replication cycle. Genome replication involves the synthesis of RNA in the nucleus , then copying from RNA to DNA (reverse transcription) incapsids. Stages invirion assembly include capsid construction and acquisition of the envelope by budding. The mode of exit of virions and non-infectious particles from the cell is not shown.

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# ***Preventing and Treatment***

Today, most of vaccinnes produced by using recombinant yeast cells contaiing the gene for the S protein. Vaccinating programs are reducing highly successfully around world.

Alpha-interferon has been used for treatment at HBV infection.
It is not eliminate the infection but it reduct to cases 30% and interferon therapy efective for  side-effectssuch as influenza and weight loss.

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