Herpes Simplex Virus (HPV)

Large DNA Virus- Herpes (Herpein -greek (creep) refering to spreading of lesions

Virion

Enveleped Icosahedral capsid

Diameter :200 nm

Capsid has six proteins, envelope contains at least 10 glyco proteins

Tegument

Material between capsid and envelope contains at least 14 proteins

Genome

Linear doubled stranded DNA,125-250 kb

Has unique regions, inverted repeat elements and repeated sequences

Virus and Hosts

Nine human herpesviruses( Herpes simples virus (HSV), Varicella-zoster virus (shingles,chickenpox), Epstein-Barr virus and cytomegalovirus)

100 known viruse in animals

Distinctive Characteristics

1. Tegument proteins function in the early steps of virus replication:

   Activation of transcription and host shutoff.

2. Virion formation begins by budding of nucleocapsids through

   the inner nuclear membrane.

3. Many viral genes counter host defenses against virus infection

4. Most herpesviruses become latent in the body and can be

reactivated months or years after primary infection

Latent Infections

After infection, viral DNA is stored in latent state in neurons, B or T lymphocytes, and other type of cells.

Can have no symptoms for months and years, or your entire life.

They can reactivate sometimes can lead to recurrent disease

Varicella zoster viruses (VZV): Chickenpox and Shingles

Chickenpox: mild disease in children but severe in infants, adults and person with impaired immune system

Adults are more susceptible to complications, such as bacterial infection in skin, sweling of the brain, and pneumonia

Chickenpox is the ony herpesvirus that spreads person to person to person through coughing sneezing

Never roots

Where VZV remains in all people that have had chickenpox

Herpes Simplex Virus (HSV Type 1 and 2)

HSV1 and HSV2 prefer to infect anatomic sites such as mouth, pharynx, and genetials.

HSV1 is genrally above the waist——

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Epstein- Barr Virus (EBV)

A common imfection throughout the world (95% population ). Occurs in young childrn and are asymptomatic

When EBV is caught during people in their teens or 20s generally become symptomatic —

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Osterid Herpervirus

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HSV genome contain both unique and repated sequence elments

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Entry by fusion may occur at the plasma memebrane or in endosomes

Binds to surface recpetor —

Tegment proteins activate viral gene expression and degrade cellular messenger RNAs

Virion host shutoff protein : rapidly degrsge cellular messenger RNAs in the cytoplasm, causing shutoff or down regulation of host synthesis —

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DNA replictaion initally proceeds in a bidercetional fashion from a replication origin

Rolling circle replication subsequently produces concatmers

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HSV proteins

1. α (immediate early): early gene activation (six genes)

2. β (early): DNA replication, late gene activation

3. γ (late): virion proteins, regulatory proteins

Herpes simplex virus establishes latent infection in neurons

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