HERPESVIRIDAE

There are 8 types of Herpes virus:

• Herpes in Greek means “creep”. This is because it reflects the creeping or spreading nature of the skin lesions caused by many herpes virus types.
  
  https://healthlibrary.epnet.com/GetContent.aspx?token=c5987b1e-add7-403a-b817-b3efe6109265&chunkiid=11950

• Herpes viruses quite ubiquitous in nature (ubiquitous means everywhere) and they are prevalent (means common/widespread).
  
• Herpes viruses are the leading cause of human viral disease just second to the influenza virus.
  
• Herpes viruses can be found mammalian and non mammalian vertebrates and non vertebrates.
  
• Structure of Herpes virus:

from left:

http://stdgen.northwestern.edu/stdgen/bacteria/hhv2/herpes.diagram.jpg

http://stdgen.northwestern.edu/stdgen/bacteria/hhv2/herpes.diagram.jpg

- Envelope: Found in the outside of the herpes virus particle. Contain numerous glycoproteins.

- Tegument: It is the space between envelope and the capsid. The tegument is a protein-filled region which contains protein and enzyme which are involved in the beginning of the replication process.

- Glycoprotein spikes: It determines the cell that can be infected due to the availability of the suitable receptors.

- Capsid: Protein shell of the herpes virus. It has an icosahedral structure.

- Genome: Contains linear double stranded DNA.

Herpes Simplex Virus 1 (HSV1) and Herpes Simplex Virus 2 (HSV2):

Similarities
- Both share about 50% of their DNA.
- Most people infected with HSV1 or HSV2 do not have any symptoms or any noticeable symptoms.
- Both infect the mucosal surfaces of the body.

Differences
- HSV1 causes the sores around the mouth and it is also known as “cold sores”.
- HSV2 infects the genital and it is also known as “genital herpes”.
- HSV1 establish latency in the trigeminal ganglion.
- HSV2 establish latency in the sacral ganglion.

Causes of HSV1 and HSV2
- People get infected with HSV1 by touching infected saliva mucous membrane or skins.
- For HSV2, people get infected during sex with an infected partner.

Stages of Infection

1. Primary infection
   When people get infected with either HSV1 or HSV2, they usually do not know of the condition since most of the time there are no symptom or noticeable symptom.
2. Latent infection
   After the herpes viruses infect the host, it will remain inactive for a long period of time. It hides within in the cells and the nerves tissue. By hiding, the herpes virus protects itself from being destroyed by the antibodies that is produced by the immune system.
3. Recurrent infection
   This happens when the herpes virus reactivates. Reactivation occurs due to various factors like sunlight, stress and menstruation. Infections can recur throughout life.

References:

• http://biommed.Isu.edu/onlinefiles/BIOL4190/LECT-6-Herpesviruses/SLIDES-herpesviridae-TIM-FOSTER.pdf
• http://chealth.canoe.ca/channel_section_details.asp?text_id=1364&channel_id=1020&relation_id=8287
• http://www.globalherbalsupplies.com/herpes/scinfo.html
• http://www.microbiologybytes.com/virology/Herpesviruses.html

HEPADNAVIRIDAE

• Hepadnaviridae is obtained from the hepatotrophic (replicates and cause infection of the liver) nature of the virus and its genome which is made up of double stranded DNA (hepadna).
  
• All hepadna viruses can cause hepatitis to their host as they infect hepatocytes that can be found in the liver.
  
• Hepatitis: Syndrome characterized by inflammation of the liver.
  
• Although all hepadnaviruses cause hepatitis to their host, but this does not mean that all hepatitis diseases are hepadna.
  
• Other hepatitis include:
  - Hepatitis A (Picornaviridae)
  - Hepatitis C (Flaviviridae)
  - Hepatitis D (No family)
  - Hepatitis E (Hepeviridae)
  - Hepatitis G (Flaviviridae)

from left in the top row:


Hepatitis A (http://www.marlerblog.com/gech_0001_0002_0_img0129(1).jpg)
Hepatitis C (http://www.co.monroe.mi.us/Monroe/uploadedImages/hepatitis-c(1).gif)
Hepatitis D (http://www.dshs.state.tx.us/idcu/disease/hepatitis/hepatitis_d/image1.gif)
Hepatitis E (http://pathmicro.med.sc.edu/virol/hep-e1.jpg)
Hepatitis G (http://www.dshs.state.tx.us/idcu/disease/hepatitis/hepatitis_g/image1.gif)

• Hepadnaviridae can be divided into two genera: Orthohepadnavirus and Avihepadnavirus.
  
• The genera are divided based on the similarities of the DNA sequence.
  
• The orthohepadnavirus infect mammals whereas the avihepadnavirus infect the avians meaning the birds.
  
• These viruses infect species that are closely related to their natural host. Example hepatitis B viruses infect humans and chimps which are closely related. That is why they have a narrow range of hosts.
  

• Among the virus classified under hepadnaviridae, only one virus that is pathogenic to human: Hepatitis B.


• Structure of hepadna virus:
  

Genome:
a. Hepatitis B has the smallest genome of 3.2 kb long among all hepadna viruses.
b. Partially double stranded DNA genome which carries all the genetic information in it.
c. The DNA consists of a positive strand and negative strand.
d. The complete negative strand is longer than of the incomplete positive strand (about 15% to 50% of the DNA is single stranded).
e. An RNA oligonucleotide is attached to the 5’ end of the positive strand while a 5’ protein covalently attached to the end of the negative strand.

Nucleocapsid:
a. Has an icosahedral shape.
b. The nucleocapsid is about 27 nm in diameter.
c. Contains a DNA polymerase and an antigen (HBcAg)
d. Three proteins can be found on the surface of the capsid: L (large), M (medium) and S (small) that is present in the ratio of 1:1:4.


Envelope:
a. It is spherical and 42 nm in diameter.
b. It surrounded the nucleocapsid.
c. Contain glycoproteins, lipids and surface antigens that is virus-specific like HBsAg.






References:

• http://www.taxonomy.nl/taxonomicon/TaxonTree.aspx?id=214545
• http://www.stanford.edu/~swhwang/10things.html
• www.marlerblog.com/.../hepatitis-a/
• http://www.care-mates.com/
• http://www.dshs.state.tx.us/idcu/disease/hepatitis/hepatitis_d/
• http://pathmicro.med.sc.edu/virol/hepatitis-virus.htm
• www.dshs.state.tx.us/.../hepatitis_g/faqs/
• virus.stanford.edu/hepadna/index.html