Herpesviruses | Sherris Medical Microbiology, 7e | AccessBiomedical Science

OVERVIEW

I’m kinda like herpes, I just keep coming back.

George Carlin

Overview

The Herpesviridae is composed of large, enveloped, double-stranded DNA viruses. There are eight known human herpesviruses (HHVs) and a very large number of animal herpesvirsues. The HHVs include: herpes simplex virus-1 (HSV-1) and HSV-2, which cause facial and genital lesions; varicella-zoster virus (VZV), which causes chickenpox and later in life can reactivate to cause shingles; Epstein-Barr virus (EBV), an infectious cause of mononucleosis as well as Burkitt lymphoma (BL) among other B-cell lymphomas; cytomegalovirus (CMV) can also cause mononucleosis symptoms in adults, and is a leading cause of congenital blindness; HHV types 6 and 7 (HHV-6 and HHV-7), which cause roseola in infants; and Kaposi Sarcoma (KS)-associated herpesvirus (KSHV), also known as HHV-8 (Table 14–1). In addition, the simian herpesvirus, herpes B virus, has occasionally caused lethal human disease in primate center workers. All herpesviruses establish lifelong latent infections in their hosts with periodic reactivation events.

✺ Large, enveloped, double-stranded DNA viruses

Eight HHVs cause a range of diseases

TABLE 14–1Human Herpesviruses

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TABLE 14–1 Human Herpesviruses

DESIGNATION

COMMON NAME

TRANSMISSION

PRIMARY INFECTION SITE

DISEASE

LATENT INFECTION SITE

HHV-1

Herpes simplex virus 1 (HSV-1)

Close contact

Mucoepithelial cells

Oral (fever blisters), ocular lesions; encephalitis

Nerve ganglia

HHV-2

Herpes simplex virus 2 (HSV-2)

Close contact

Sexual transmission

Mucoepithelial cells

Genital, anal lesions; severe neonatal infections; meningitis

Nerve ganglia

HHV-3

Varicella-zoster virus (VZV)

Respiratory route

Inhalation

Close contact

Mucoepithelial cells

Chickenpox (primary infection); shingles (reactivation)

Nerve ganglia

HHV-4

Epstein-Barr virus (EBV)

Saliva

Kissing

B cell, oral epithelium

Infectious mononucleosis (primary infection); tumors, including B-cell tumors (Burkitt lymphoma, immunoblastic lymphomas of the immunosuppressed); nasopharyngeal carcinoma, some T-cell tumors

B lymphocytes

HHV-5

Cytomegalovirus (CMV)

Close contact, sexual transmission

Congenital

Blood-to-blood

Transplant

Leukocytes (T and B)

Lymphocytes

Monocytes

Mononucleosis; severe congenital infection; infections in immunocompromised (gastroenteritis, retinitis, pneumonia)

Monocytes, neutrophils, vascular endothelial cells

HHV-6

Human herpesvirus 6

Close contact

Respiratory route

T lymphocytes

Roseola in infants (primary infection); infections in allograft recipients (pneumonia, marrow failure)

T lymphocytes monocytes, macrophages

HHV-7

Human herpesvirus 7

Saliva

Close contact

T lymphocytes

Some cases of roseola (primary infection)

CD4+ T cells

HHV-8

Kaposi sarcoma-associated herpesvirus

(KSHV), human herpesvirus 8

Saliva, blood?

B lymphocytes

Peripheral blood mononuclear cell

Oral epithelium

Tumors, including Kaposi sarcoma; some B-cell lymphomas

B-lymphocytes

Virus-infected tumors

HERPESVIRUSES: GROUP CHARACTERISTICS

VIROLOGY

All herpesviruses are morphologically similar, with an overall size of 180 to 200 nm. An example of a HSV virion is shown in Figure 14–1 as a representative virion structure for herpesviruses. The linear, double-stranded DNA genome and core proteins are encapsidated by an icosahedral capsid. The capsid is surrounded by the tegument, a relatively amorphous protein-filled region unique to herpesviruses. The tegument contains viral proteins and enzymes that play a ...

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