Herpesviruses Overview and Properties

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Questions and Answers

Which of the following statements about the transmission of HHV-8 is accurate?

Transmission occurs mainly through contaminated food and water.

The specific route of HHV-8 transmission is not fully understood, but evidence suggests sexual transmission and solid organ transplants may play a role. (correct)

The transmission of HHV-8 is primarily through respiratory droplets.

HHV-8 is transmitted through direct contact with infected skin lesions.

What is a potential consequence of a HHV-4 infection?

Development of chronic Fatigue Syndrome.

Reactivation leading to pneumonia, chorioretinits or colitis.

Development of Kaposi's Sarcoma.

Development of Burkitts Lymphoma. (correct)

Which of the following cell types is most commonly associated with the persistence of the HHV-4 genome?

Polymorphs

B Lymphocytes (correct)

T Lymphocytes

Monocytes

What is the primary pharmacological treatment for severe HHV-5 infections, such as pneumonia or chorioretinitis?

Ganciclovir and Foscarnet (B) Signup and view all the answers

Which of the following is a characteristic feature of infectious mononucleosis?

Swollen lymph nodes in the neck and armpits. (C) Signup and view all the answers

Which of the following is NOT a characteristic of Herpesviridae?

Linear single-stranded DNA (D) Signup and view all the answers

Which herpesvirus subfamily includes the Epstein-Barr Virus (EBV)?

Lymphocryptovirus (D) Signup and view all the answers

What is the primary means of transmission for HHV-1 and HHV-2?

Direct contact with infectious material (D) Signup and view all the answers

Which of the following is NOT a possible route of transmission for genital herpes infections?

Blood Transfusion (C) Signup and view all the answers

What clinical presentation is most commonly associated with a primary HHV-1 infection in young children?

Gingivostomatitis (A) Signup and view all the answers

Where does HHV-1 DNA persist in the body after a primary oropharyngeal infection?

Trigeminal ganglion (C) Signup and view all the answers

In which part of the host cell does DNA replication and encapsidation of herpesviruses occur?

Nucleus (B) Signup and view all the answers

What is the characteristic morphology of herpesviruses, making them indistinguishable under electron microscopy?

Spherical enveloped virion with an icosahedral capsid (C) Signup and view all the answers

Which of the following is NOT a characteristic clinical presentation of herpes simplex?

Genital warts (C) Signup and view all the answers

Which of the following is the preferred method for detecting HHV-1/2 in cerebrospinal fluid (CSF)?

PCR (D) Signup and view all the answers

Which of the following is NOT true regarding the treatment of recurrent herpes genitalis?

Treatment is effective in eliminating the virus from the body. (B) Signup and view all the answers

Which of the following is responsible for the characteristic skin rash seen in chickenpox?

Multiplication of the virus in epithelial cells of the skin. (C) Signup and view all the answers

What is the primary route of transmission for human herpesvirus 3 (HHV-3)?

Inhalation. (B) Signup and view all the answers

Which of the following herpesviruses is commonly associated with morbidity and mortality in immunocompromised individuals?

HHV-5 (C) Signup and view all the answers

Which is the main way an individual can acquire a secondary herpes simplex infection?

Through oral-genital contact. (D) Signup and view all the answers

Which of the following is NOT a common site for the development of genital herpes lesions?

Tonsils (A) Signup and view all the answers

Study Notes

Herpesviruses of Humans

Herpesviruses are classified into subfamilies and genera.
Simplexvirus includes Human Herpesvirus 1 (HHV-1) and Human Herpesvirus 2 (HHV-2).
Varicellovirus includes Human Herpesvirus 3 (HHV-3), also known as Varicella-Zoster Virus (VZV).
Betahepesvirinae includes Human Herpesvirus 5 (HHV-5), also known as Cytomegalovirus (CMV).
Roseolovirus includes Human Herpesvirus 6 (HHV-6).
Lymphocryptovirus includes Human Herpesvirus 4 (HHV-4), also known as Epstein-Barr Virus (EBV).

Properties of Herpesviridae

Herpesviruses are spherical, enveloped virions, with a diameter of 120-200nm.
They have an icosahedral capsid.
They contain linear double-stranded DNA.
Replication occurs in the nucleus.
DNA replication and encapsulation occur in the nucleus.
Herpesviruses establish latent infections, with their genome persisting in the nucleus of neurons or lymphocytes.
Reactivation triggers replication and shedding of infectious virus.

Herpesvirus Particle

Herpesvirus particles have identical morphology, making them indistinguishable under electron microscopy.

Replication

HHV infection begins with virus attachment to cellular receptors.
The virus penetrates the cell by fusion of the viral envelope with the plasma membrane.

Herpesviridae

All herpesviruses can persist indefinitely in their host cells as an episome within the nucleus.
In humans, herpesviruses of different subfamilies occupy specific ecological niches, particularly in different cell types.

Simplexvirus (HHV-1 & HHV-2)

Transmission occurs via direct contact with infectious material.
Orofacial herpes infections are often transmitted by kissing.
Genital herpes infections result from direct contact, including genital-genital, oral-genital, and anal-genital contact.
Herpes simplex infection can occur during asymptomatic virus shedding.
Incubation period for herpes simplex is 2-12 days.

Gingivostomatitis

Primary infection with HHV-1 often involves the mouth and/or throat.
Young children may develop gingivostomatitis, characterized by vesicles on the mouth and gums that rupture to form ulcers.
Following recovery, HHV-1 DNA persists in the trigeminal ganglion, leading to a high chance of recurrent attacks of herpes labialis (oral herpes).

Genital Herpes

Primary genital herpes is typically caused by HHV-2, but HHV-1 is increasingly implicated.
Genital herpes is commonly seen in young adults.
Characteristic lesions include ulcerating vesicular lesions on the vulva, vagina, cervix, and perineum in females and the penis in males. Rectum and perianal regions can also be affected.

Lab Diagnosis

Characteristic clinical presentations (e.g., recurrent herpes labialis) can aid diagnosis.
Unclear-cut presentations may require additional tests, including tests for encephalitis, kerato-conjunctivitis, or genital herpes localised to the cervix.

Specimens for Diagnosis

Vesicle fluid, cerebrospinal fluid (CSF), and swabs/scrapings from the genital tract, throat, eye, or skin can be collected for diagnosis.
Isolation in cell culture and ELISA on CSF are methods.
PCR is a preferred method for detecting HHV in CSF.

Chemotherapy

Acyclovir and valacyclovir are common antiviral medications.
Treatment of recurrent genital or oral herpes may not provide significant benefit.

Human Herpes Virus 3 (Varicella-Zoster Virus)

HHV-3 causes two common diseases: chickenpox (varicella) and shingles (herpes zoster).
Chickenpox typically occurs in childhood.
Shingles is more common in older adults and immunocompromised individuals.
VZV enters through inhalation and replicates in respiratory tract mucosa.

HHV-3 Pathogenesis

Incubation period is 14 days.
Virus spreads via lymphatics and blood, multiplying in mononuclear leukocytes and capillary endothelial cells.
Skin rash results from viral multiplication in epithelial cells.
Virus ascends sensory nerve axons and becomes latent in sensory ganglia.
Primary infection is controlled by cellular immunity, leading to long-term immunity.

Human Herpes Virus-5

Of all herpes viruses, HHV-5 (CMV) is the most frequent cause of morbidity and mortality among immunocompromised individuals.
Infection is typically acquired subclinically in childhood through inhalation.
Infected individuals carry the virus lifelong, intermittently shedding it in saliva, urine, semen, cervical secretions, and breast milk.
During acute infection and reactivation, virus can be found in monocytes, polymorphs, and, to a lesser extent, lymphocytes.

HHV-5 Lab Diagnosis

Viral culture is a slow method.
HHV-5 DNA can be detected using polymerase chain reaction (PCR).

HHV-5 Treatment

Ganciclovir and foscarnet are commonly used antiviral medications.
These drugs are most effective for severe HHV-5 infections, such as pneumonia, chorioretinitis, and colitis.

Human Herpes Virus-4 (EBV)

HHV-4's genome persists in B cells as a plasmid.
Few viral genes are expressed, but expression of some leads to B-cell immortalization.
Immortalized B cells produce B cell growth factor and monoclonal antibodies.
The virus exists in two types, with Type A being most prevalent in Europe and the USA, often isolated from B lymphocytes.

HHV-4 Clinical Features

EBV infection can result in infectious mononucleosis (glandular fever), with an incubation period of 4–7 weeks.
Complications include neurologic disorders (e.g., Bell's palsy, meningitis, transverse myelitis).
Other complications include nephritis and thrombocytopenia.
EBV plays a role in certain cancers, such as Burkitt's lymphoma and nasopharyngeal carcinoma.

HHV-8

HHV-8 is associated with Kaposi's sarcoma..
transmission route is unknown although evidence leans towards sexual and solid organ transplants.
HHV-8 infection plays a role in lesion development through infection of spindle and flat endothelial cells. This leads to cell proliferation/transformation.

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Description

This quiz covers the classification and properties of herpesviruses that affect humans. It includes details about different subfamilies and their associated viruses, as well as key characteristics of the Herpesviridae family. Test your knowledge on this important group of viruses!