Human Cytomegalovirus: An Insight of Its Pathobiology and Therapeutics

Human cytomegalovirus (HCMV) belongs to herpes family of viruses. It is also known as human herpesvirus 5 (HHV-5). In 1956 and 1957, Weller, Smith, and Rowe independently isolated and grew cytomegaloviruses (CMVs) from mice and humans. The CMVs have derived their name from Greek which means cell (cyto) and big (megalo). These are the largest known disease-causing viruses in humans with a DNA genome of size 230 Kbp. In children, HCMV seroprevalence is low but with time seroprevalence increases by 40–80% globally. HCMV is one of the most opportunistic infections. It remains in latent phase in host cells by modulating the immune environment of the host cell. Monocyte-derived macrophages (MDM) and endothelial cells are the major reservoirs for latent phase of HCMV. In immunocompetent individuals, it remains latent phase and asymptomatic, but in immunocompromised individuals, it affects almost all the major organs of the body, i.e. retinitis ocular (retinitis), central nervous system (polyradiculopathy, meningoencephalitis), lungs (pneumonitis), gastrointestinal tract (esophagitis, gastritis, ileitis, colitis, pancreatitis), and liver (hepatitis). Various in vitro- and in vivo-based models are being developed for the propagation of HCMVs. Serology, histopathology, viral culture, shell-vial assay, antigenemia, and nucleic acid testing are most common diagnostic tests for HCMV. Antiviral therapies (ganciclovir, foscarnet, and cidofovir) are the major mode of treatment for HCMV, but these therapies are associated with side effects. There is no vaccine available for HCMV at present but in coming decade we can expect effective vaccine against HCMV. Most of the therapeutic options are focused on CMV-specific T-cell therapy.