Cytomegalovirus - HCMV

Human cytomegalovirus is a species of virus that belongs to the viral family known as Herpesviridae or herpesviruses. It is typically abbreviated as HCMV and is alternatively known as Human herpesvirus 5 (HHV-5). Within Herpesviridae, HCMV belongs to the Betaherpesvirinae subfamily, which also includes cytomegaloviruses from other mammals.

Although they may be found throughout the body, HCMV infections are frequently associated with the salivary glands. HCMV infection is typically unnoticed in healthy people, but can be life-threatening for the immunocompromised, such as HIV-infected persons, organ transplant recipients, or new born infants. It can cause hydrops fetalis in infants. After infection, HCMV has an ability to remain latent within the body over long periods. CMV persists in the host because the viral genome encodes multiple proteins that interfere with MHC class I presentation of viral antigens. One viral protein blocks translocation of peptides into the lumen of the endoplasmic reticulum, while two other viral proteins cause degradation of MHC class I proteins before they reach the cell surface. Hence, diagnosis is done histologically by looking for inclusion bodies in salivary glands. A prevention by hygienic measures is included in information given to pregnant women.

HCMV is found throughout all geographic locations and socioeconomic groups, and infects between 50% and 80% of adults in the United States (40% worldwide) as indicated by the presence of antibodies in much of the general population. Seroprevalence is age-dependent: 58.9% of individuals aged 6 and older are infected with CMV while 90.8% of individuals aged 80 and older are positive for HCMV. HCMV is also the virus most frequently transmitted to a developing fetus. HCMV infection is more widespread in developing countries and in communities with lower socioeconomic status and represents the most significant viral cause of birth defects in industrialized countries. CMV "seems to have a large impact on immune parameters in later life and may contribute to increased morbidity and eventual mortality."

A vaccine against cytomegalovirus (CMV) is currently under investigation. As a member of the TORCH complex, cytomegalovirus can cause congenital infection. Because of this, there has been considerable effort made towards the development of a vaccine, with particular emphasis on protection for pregnant women. Development of such a vaccine has been emphasized as a priority by the National Vaccine Program Office in the United States. A phase 2 study of a CMV vaccine published in 2009 indicated an efficacy of 50%, thus the protection provided was limited and a number of subjects contracted CMV infection despite the vaccination. In one case also congenital CMV was encountered.