Human cytomegalovirus

Cytomegalovirus virion

Human cytomegalovirus (HCMV), also known as human herpesvirus 5 (HHV-5), is a member of the Herpesviridae family, which includes other viruses such as herpes simplex virus and varicella-zoster virus. HCMV is a common virus that infects people of all ages and is typically asymptomatic in healthy individuals. However, it can cause significant disease in immunocompromised individuals and is a major cause of congenital infections.

Virology

Schematic of CMV structure

HCMV is an enveloped virus with a double-stranded DNA genome. The virus is characterized by its large size and complex structure, which includes a capsid, tegument, and lipid envelope. The genome of HCMV is approximately 230 kilobases in length and encodes for a variety of proteins that facilitate viral replication and immune evasion.

Replication Cycle

The replication cycle of HCMV begins with the attachment of the virus to the host cell surface, followed by entry into the cell. Once inside, the viral DNA is transported to the nucleus where it is transcribed and replicated. The virus assembles in the nucleus and acquires its envelope by budding through the nuclear membrane. Mature virions are then released from the cell to infect new cells.

Pathogenesis

HCMV can establish both lytic and latent infections. During lytic infection, the virus actively replicates and can cause cell death. In latent infection, the virus persists in a dormant state within the host cells, particularly in monocytes and macrophages. Reactivation of the virus can occur under conditions of immunosuppression.

Congenital Infection

CMV placentitis

Congenital HCMV infection occurs when the virus is transmitted from a pregnant mother to her fetus. This can lead to a range of outcomes, from asymptomatic infection to severe disease, including hearing loss, microcephaly, and developmental delays. HCMV is the leading infectious cause of congenital disabilities in developed countries.

Clinical Manifestations

In healthy individuals, HCMV infection is often asymptomatic or may present with mild flu-like symptoms. In contrast, immunocompromised individuals, such as those with HIV/AIDS or organ transplant recipients, can experience severe complications, including pneumonia, retinitis, and gastroenteritis.

Diagnosis

Diagnosis of HCMV infection can be achieved through serological tests, which detect antibodies against the virus, or through molecular techniques such as polymerase chain reaction (PCR) to detect viral DNA in blood or other body fluids.

Treatment

Antiviral drugs for HCMV

Antiviral medications, such as ganciclovir, valganciclovir, foscarnet, and cidofovir, are used to treat HCMV infections, particularly in immunocompromised patients. These drugs inhibit viral DNA synthesis, thereby reducing viral replication.

Prevention

Preventive measures for HCMV include practicing good hygiene, such as handwashing, and avoiding contact with bodily fluids of infected individuals. In healthcare settings, standard precautions are essential to prevent nosocomial transmission.

Related Pages

• Herpesviridae
• Congenital infection
• Immunocompromised host
• Antiviral drug