Herpesviruses

Question 1

Click on Answer for electron micrographs of herpesviruses.

Answer 1

[Image 1] [Image 2] [Image 3] [Image 4] [Image 5]

Question 2

What family do herpesviruses belong to?

Answer 2

Herpesviridae

Question 3

State the three subfamilies of Herpesviruses, also listing their respective members.

Answer 3

(1) Alphaherpesviruses: HSV-1, HSV-2, VZV (HHV-3)
(2) Betaherpesviruses: CMV (HHV-5), HHV-6, HHV-7
(3) Gammaherpesviruses: EBV (HHV-4), HHV-8

Question 4

What type of genetic material do herpesviruses have?

Answer 4

double-stranded DNA

Question 5

What is the primary disease caused by varicella-zoster virus (VZV)?

Answer 5

chickenpox and shingles

Question 6

Which herpesvirus is associated with mononucleosis?

Answer 6

Epstein-Barr virus [EBV or HHV-4]

Further notes:
Mononucleosis, often called “mono” or the “kissing disease,” is a viral infection primarily caused by the Epstein-Barr virus (EBV). It spreads through saliva, which is why it’s commonly associated with kissing, but it can also be transmitted by sharing drinks, food utensils, or through other close contact. The symptoms of mononucleosis can vary but often include: extreme fatigue, fever, sore throat, swollen lymph nodes in the neck and armpits, swollen tonsils, headache, skin rash…

There is no specific treatment for mono; it usually resolves on its own.

Question 7

What is the common name for human herpesvirus 5 (HHV-5)?

Answer 7

cytomegalovirus (CMV)

Question 8

Which herpesvirus is linked to Kaposi’s sarcoma?

Answer 8

Human herpesvirus 8 (HHV-8)

Further notes:
Kaposi’s sarcoma is a type of cancer that forms in the lining of blood and lymph vessels. It causes lesions, which are abnormal tissue growths, to appear on the skin, mucous membranes, and sometimes internal organs.
Symptoms:
✓ urple, red, or brown skin lesions that may be flat or raised
✓ esions in the mouth, gastrointestinal tract, or respiratory tract
✓ Swelling and pain in the affected areas
Causes: Kaposi’s sarcoma is linked to infection with human herpesvirus 8 (HHV-8). It primarily affects individuals with weakened immune systems, such as those with HIV/AIDS or those on immunosuppressive drugs.

[Image 1] [Image 2]

Question 9

What is the structure of a herpesvirus particle?

Answer 9

An icosahedral capsid, tegument, and lipid envelope.

Question 10

What is the term for the ability of herpesviruses to remain dormant in the body?

Answer 10

latency

Question 11

What is the primary mode of transmission for herpesviruses?

Answer 11

intimate contact

Question 12

What is the tegument of a herpes virus and what is its significance?

Answer 12

The tegument is the space between the envelope and the capsid. It contains viral proteins and enzymes that help initiate replication.

Question 13

How are HSV-1 and HSV-2 transmitted?

Answer 13

HSV-1 is typically transmitted through oral contact, while HSV-2 is usually transmitted through sexual contact. Both require close personal contact for transmission.

Question 14

What is the primary site of infection for HSV-1?

Answer 14

The primary site of infection for HSV-1 is the oropharyngeal mucosa, leading to cold sores [aka. fever blisters] around the mouth.

Further notes:
Cold sores: [Image 1] [Image 2]

Question 15

What is the primary site of infection for HSV-2?

Answer 15

The primary site of infection for HSV-2 is the genital or perigenital area, leading to genital herpes.

Question 16

Describe the latency and reactivation process of HSV.

Answer 16

After the initial infection, HSV travels to the sensory ganglia; HSV-1 establishes latency in the trigeminal ganglion, whereas HSV-2 establishes latency in the sacral ganglion. Reactivation can occur due to various triggers, leading to the virus traveling back to the skin or mucous membranes, causing recurrent lesions.

Question 17

What are common triggers for HSV reactivation?

Answer 17

Recurrences may be activated by various stimuli which include stress, trauma, or fever, sunlight, menses and certain foods.

Question 18

What is ocular herpes?

Answer 18

Ocular herpes is an infection of the eye caused by the herpes simplex virus (HSV), which can affect various parts of the eye. It is usually caused by HSV-1.

Question 19

How is ocular herpes contracted?

Answer 19

People typically contract ocular herpes by touching a cold sore and then touching the eyes with their contaminated fingers.

Question 20

What are the different types of ocular herpes?

Answer 20

epithelial keratitis (outer layer of the cornea), stromal keratitis (deeper layers of the cornea), herpes simplex uveitis (inflammation of the uvea), herpes zoster ophthalmicus (caused by the varicella-zoster virus)

Question 21

Discuss herpetic whitlow.

Answer 21

This is a painful infection of the fingers or thumbs caused by the herpes simplex virus (HSV). It can be caused by either HSV-1 or HSV-2.
Symptoms: painful fluid-filled blisters on the skin near the fingernail, redness and swelling around the affected area.
[Image 1] [Image 2]

Further notes:
Herpetic whitlow tends to be more common among dentists and dental hygienists. This is because they frequently come into contact with the herpes simplex virus (HSV) through patients’ oral secretions, especially if there are holes in their latex gloves.

Question 22

What is Herpes Simplex Encephalitis?

Answer 22

This is a severe brain infection caused by the herpes simplex virus, primarily HSV-1, and less commonly HSV-2.

Question 23

What is the primary treatment for HSE?

Answer 23

intravenous administration of acyclovir

Question 24

symptoms of genital herpes

Answer 24

genital lesions [small red bumps or tiny white blisters], fever, pain, dysuria, mucoid vaginal and urethral discharge with enlarged inguinal lymph nodes

[Diagram] [Image 1] [Image 2] [Image 3]

Question 25

How is Neonatal HSV acquired?

Answer 25

It is acquired during passage through the infected birth canal.

Question 26

Which herpesvirus is the most common cause of congenital defects?

Answer 26

cytomegalovirus

Question 27

Which herpesvirus has:
(a) the smallest genome?
(b) the largest genome?

Answer 27

(a) Varicella Zoster
(b) Cytomegalovirus

Question 28

How is cytomegalovirus transmitted?

Answer 28

CMV is spread through body fluids such as blood, saliva, urine, semen and breast milk.

Question 29

Discuss the pathogenesis of cytomegalovirus.

Answer 29

CMV establishes a latent infection in mononuclear leucocytes (monocytes and B lymphocytes), epithelial cells and stromal cells of bone marrow.
In most cases, people with CMV are asymptomatic, but when symptoms are present, they resemble those of mononucleosis [fatigue, fever, sore throat, swollen lymph nodes, swollen tonsils, headache…].

Question 30

What are the symptoms of congenital Cytomegalic Inclusion Disease?

Answer 30

hepatosplenomegaly, jaundice, thrombocytopenic purpura [low platelet count causing bruising], pneumonitis [lung inflammation], chorioretinitis [inflammation or the retina], CNS damage [leading to mental retardation and unilateral or bilateral hearing loss]

Further notes:
The first five symptoms may also manifest in immunocompromised patients.

Histological Diagnosis of CID
(1) Tissue sampling: A biopsy is taken from the affected organ, such as the liver, lungs or kidneys.
(2) Histological Examination: The tissue sample is stained and examined under a microscope. Pathologists look for cells that show cytomegaly (enlarged cells) and inclusion bodies.
(3) Inclusion bodies: These are distinctive features of CMV infection. They appear as large, basophilic intranuclear inclusions surrounded by a clear halo, often reffered to as “owl’s eye” inclusions.
[Slide 1] [Slide 2]

Question 31

Which antiviral medication is usually administerd to manage symptomatic CMV infections?

Answer 31

ganciclovir

Question 32

Discuss Viral Culture as a means of laboratory diagnosis of HSV.

Answer 32

A sample from a lesion (blister or sore) is taken and cultured in the lab to grow the virus. The cells are then monitored for cytopathic effects. If HSV is present, it will cause characteristic changes in the cultured cells. These changes are observed under a microscope.

Further notes:
Pros: Highly specific and can differentiate between HSV-1 and HSV-2.
Cons: Less sensitive, especially if the lesion is healing.

Question 33

Discuss Polymerase Chain Reaction (PCR) as a means of laboratory diagnosis of HSV.

Answer 33

This method is used to detect HSV DNA in samples from lesions, blood, CSF, or other tissues.

Further notes:
Pros: Highly sensitive and specific, can detect low levels of the virus, and can differentiate between HSV-1 and HSV-2.
Cons: More expensive and requires specialized equipment.

Question 34

Discuss Direct Fluorescent Antibody (DFA) test as a means of laboratory diagnosis of HSV.

Answer 34

This method uses fluorescently labelled antibodies to detect HSV antigens in samples from lesions.
[Image]

Further notes:
Pros: Rapid and can differentiate between HSV-1 and HSV-2.
Cons: Less sensitive than PCR.

Question 35

Discuss Serologic Tests (Antibody Testing) as a means of laboratory diagnosis of HSV.

Answer 35

This method detects antibodies against HSV in the blood.

Further notes:
Pros: Useful for diagnosing past infections and in cases where lesions are not present.
Cons: Cannot distinguish between current and past infections, and may not be useful in early infection.

Question 36

What is the mechanism of action of drugs used to manage HSV-1/2 infections?

Answer 36

They work by inhibiting viral DNA synthesis, which helps to reduce the severity and duration of symptoms.