Herpesviruses Flashcards
Click on Answer for electron micrographs of herpesviruses.
What family do herpesviruses belong to?
Herpesviridae
State the three subfamilies of Herpesviruses, also listing their respective members.
(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
What type of genetic material do herpesviruses have?
double-stranded DNA
What is the common name for human herpesvirus 5 (HHV-5)?
cytomegalovirus (CMV)
What is the structure of a herpesvirus particle?
An icosahedral capsid, tegument, and lipid envelope.
What is the term for the ability of herpesviruses to remain dormant in the body?
latency
What is the primary mode of transmission for herpesviruses?
intimate contact
What is the tegument of a herpes virus and what is its significance?
The tegument is the space between the envelope and the capsid. It contains viral proteins and enzymes that help initiate replication.
How are HSV-1 and HSV-2 transmitted?
HSV-1 is typically transmitted through oral contact, while HSV-2 is usually transmitted through sexual contact. Both require close personal contact for transmission.
What is the primary site of infection for HSV-1?
What is the primary site of infection for HSV-2?
The primary site of infection for HSV-2 is the genital or perigenital area, leading to genital herpes.
Describe the latency and reactivation process of HSV.
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 ganglia. Reactivation can occur due to various triggers, leading to the virus traveling back to the skin or mucous membranes, causing recurrent lesions.
What are common triggers for HSV reactivation?
Recurrences may be activated by various stimuli which include stress, trauma, or fever, sunlight, menses and certain foods.
What is ocular herpes?
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.
How is ocular herpes contracted?
People typically contract ocular herpes by touching a cold sore and then touching the eyes with their contaminated fingers.
What are the different types of ocular herpes?
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)
Discuss herpetic whitlow.
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.
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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.
What is Herpes Simplex Encephalitis?
This is a severe brain infection caused by the herpes simplex virus, primarily HSV-1, and less commonly HSV-2.
What is the primary treatment for HSE?
intravenous administration of acyclovir
symptoms of genital herpes
genital lesions [small red bumps or tiny white blisters], fever, pain, dysuria, mucoid vaginal and urethral discharge with enlarged inguinal lymph nodes
How is Neonatal HSV acquired?
It is acquired during passage through the infected birth canal.
Which herpesvirus is the most common cause of congenital defects?
cytomegalovirus
Which herpesvirus has:
(a) the smallest genome?
(b) the largest genome?
(a) Varicella Zoster
(b) Cytomegalovirus
What is the primary disease caused by varicella-zoster virus (VZV)?
How is VZV transmitted and what is its pathogenesis?
VZV is primarily transmitted through respiratory droplets and direct contact with virus-infected vesicles. After initial infection, the virus replicates in the respiratory tract, spreads to regional lymph nodes, and causes viremia. It then infects the skin, leading to the characteristic vesicular rash. VZV establishes latency in sensory ganglia and can reactivate later in life, causing shingles.
List some medications that are used to treat VZV infection.
acyclovir, valacyclovir, famciclovir
(1) Ramsay Hunt Syndrome, also known as ____(a)____ is a complication of ____(b)____ caused by reactivation of the ____(c)____ virus.
(2) Which nerves are affected in Ramsay Hunt Syndrome?
(1) (a) Herpes zoster oticus, (b) shingles, (c) Varicella Zoster
(2) facial nerves near the inner ear
List symptoms of Ramsay Hunt Syndrome.
◾ intense ear pain
◾ painful vesicular rash around the ear, mouth, face, neck and scalp
◾ facial paralysis on the affected side
◾ partial or complete hearing loss in the affected ear
◾ vertigo (spinning sensation)
◾ tinnitus (ringing or buzzing sounds)
◾ loss of taste in the front two-thirds of the tongue
◾ dry mouth and eyes
How is cytomegalovirus transmitted?
CMV is spread through body fluids such as blood, saliva, urine, semen and breast milk.
Discuss the pathogenesis of cytomegalovirus.
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…].
What are the symptoms of congenital Cytomegalic Inclusion Disease?
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], microcephaly
[9-minute video]: Congenital CMV - causes, symptoms, diagnosis, treatment, pathology
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.
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Which herpesvirus is associated with mononucleosis?
Epstein-Barr virus [EBV or HHV-4]
Discuss the trasmission of Epstein-Barr virus.
EBV is highly contagious and spreads primarily through bodily fluids, especially saliva. This is why it is often referred to as the “kissing disease”. However it can also spread through semen, blood, organ transplants and contaminated objects.
Further notes:
Most people are infected with EBV at some point in their lives, with about 95% of adults worldwide carrying the virus.
Discuss the pathogenesis of EBV.
🛸 Once EBV enters the body, it infects the epithelial cells in the oropharynx and nasopharynx. [HHV-4 binds via its envelope glycoprotein gp350/gp220 to the complement receptor CD21.]
🛸 In these epithelial cells, EBV undergoes replication and lysis, with release of infectious virions.
🛸 The B lymphocytes infiltrating the nasopharynx become infected. Once inside the B cells, EBV can establish a latent infection. The virus’ DNA integrates into the host cell’s genome, allowing it to persist in a dormant state.
Discuss associated diseases of EBV.
(a) Infectious mononucleosis
Symptoms: fever, sore throat, swollen lymph nodes, and fatigue.
Complications: neurological issues e.g. Bell’s Palsy, meningoencephalitis, splenomegaly, thromboyctopenia, nephritis
(b) Cancers
✔ Burkitt’s lymphoma [This is a B cell lymphoma prevalent in children in tropical Africa. The regular association of HHV-4 with Burkitt’s suggests a cause and effect relationship.]
✔ Nasopharyngeal carcinoma
✔ Hodgkin’s lymphoma
Name the childhood disease most commonly associated with HHV-6 infection.
roseola infantum aka. exanthem subitum
Briefly discuss the transmission and pathogenesis of HHV-6.
🛸 HHV-6 is primarily transmitted through saliva, but it can also spread through other body fluids.
🛸 HHV-6 primarily infects T lymphocytes, particularly CD4+ T cells.
🛸 After the initial infection, HHV-6 can establish latency in other cells including monocytes, macrophages, and salivary gland cells.
🛸 [2-minute video]: Human Herpes Virus 6 (Roseola infantum)
Which herpesvirus is linked to Kaposi’s sarcoma?
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.
Which antiviral medications are usually administerd to manage symptomatic CMV infections?
ganciclovir, foscarnet
Discuss Viral Culture as a means of laboratory diagnosis of HSV.
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.
Briefly discuss Polymerase Chain Reaction (PCR) as a means of laboratory diagnosis of HSV.
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.
Briefly discuss Direct Fluorescent Antibody (DFA) test as a means of laboratory diagnosis of HSV.
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.
Briefly discuss Serologic Tests as a means of laboratory diagnosis of HSV.
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.
What is the mechanism of action of drugs used to manage HSV-1/2 infections?
They work by inhibiting viral DNA synthesis, which helps to reduce the severity and duration of symptoms.
Nasopharyngeal carcinoma is associated with this virus.
(a) Human herpesvirus 3
(b) Measles virus
(c) Rubella virus
(d) Human herpesvirus 8
(e) Human herpesvirus 4
(e) Human herpesvirus 4
[Diagram]
Which of the following statements about Herpesviruses is true?
(a) they are naked
(b) they belong to Baltimore Group VI
(c) they have RNA genome
(d) they cause life-long infections
(e) they are all treatable with antiviral therapy
(d) they cause life-long infections
The herpesvirus associated with herpetic whitlow belong which sub-family?
(a) Betaherpesvirinae
(b) Gammaherpesvirinae
(c). Papillomaviridae
(d) Alphaherpesvirinae
(e) Deltaherpesvirinae
(d) Alphaherpesvirinae
Which of the following is a characteristic of herpesviruses?
(a) ssRNA
(b) undergo latency
(c) non-enveloped
(d) segmented genome
(e) ssDNA
(b) undergo latency
The herpesvirus associated with herpes gladiatorum belongs to which sub-family?
(a) Papillomaviridae
(b) Alphaherpesvirinae
(c) Deltaherpesvirinae
(d) Betaherpesvirinae
(e) Gammaherpesvirinae
Which of the following is a characteristic of herpesviruses?
(a) Segmented genome
(b) They can cause cell membrane fusion
(c) ssRNA
(d) ssDNA
(e) Non-enveloped
(b) They can cause cell membrane fusion
Which of the following viruses undergoes latency in B cells?
(a) Human herpesvirus 1
(b) Human herpesvirus 8
(c) Human herpesvirus 6
(d) Human herpesvirus 3
(e) Human herpesvirus 2
(b) Human herpesvirus 8
Further notes:
The herpesviruses that undergo latency in B cells are:
🛸 Human herpesvirus 4
🛸 Human herpesvirus 8
Which one of the following is not true about herpesviruses?
(a) They only infect humans
(b) They cause lifelong infections
(c) They are large DNA viruses
(d) They undergo latency
(e) They are enveloped
(a) They only infect humans
Which one of the following is most likely to undergo latency in the trigeminal ganglia?
(a) Human herpesvirus 8
(b) Human herpesvirus 6
(c) Human herpesvirus 3
(d) Human herpesvirus 4
(e) Human herpesvirus 1
(e) Human herpesvirus 1
