Everything About The Cytomegalovirus
Date: 2 سال قبل
Cytomegalovirus (CMV) is a genus of herpesvirus in the subfamily of β-Herpesvirinae. CMV is the prototypical β-herpesvirus.
The HCMV virion ranges from 200 to 300 nM in diameter. The virion tegument layer resides between the envelope and the capsid and remains the least well-characterized region of the virion both in terms of composition and organization. The tegumented nucleocapsid is surrounded by a lipid bilayer envelope derived from the endoplasmic reticulum–Golgi intermediate compartment and contains a large number of virusencoded proteins. The envelope exhibits a unique lipid content including very long chain fatty acids and cholesterol that distinguishes it from membranes of uninfected cells.
The HCMV genome is one of the largest and most complex of any characterized herpesvirus.Initial DNA sequence analysis, together with follow-up investigatn established the presence of 40 conserved core protein-coding genes common to all subfamilies of mammalian herpesviruses along with a larger subset (~70) conserved across the β-herpesviruses with some of these encoding late transcription
Cytomegalovirus causes three clinical syndromes.Congenital cytomegalovirus infection (when symptomatic) causes hepatosplenomegaly, retinitis, rash, and central nervous system involvement. In about 10 per cent of older children and adults, primary cytomegalovirus infection causes a mononucleosis syndrome with fever, malaise, atypical lymphocytosis, and pharyngitis. Immunocompromised hosts (transplant recipients and human immunodeficiency virus [HIV]-infected individuals) may develop life-threatening disseminated disease involving the lungs, gastrointestinal tract, liver, retina, and central nervous system.
PATHOGENESIS AND PATHOLOGY
HCMV infection and transmission in most people proceeds without symptoms or disease.Clinically apparent manifestations of HCMV infection are expressed almost exclusively in the context of congenital infection and in the immunocompromised host, including transplant recipients and HIV/AIDS and cancer patients undergoing immunosuppressive chemotherapy.This virus is also an occasional cause of infectious mononucleosis. Characteristics of CMVdisease are discussed in section Clinical Features. Numerous books, reviews, and chapters have described person-to-person transmission, dissemination, and host control characteristics that place individuals at risk for HCMV disease. From initial infection at the mucosal epithelium, HCMV infects diverse cell types and tissues, causing a systemic infection with persistent and sporadic shedding for life.
as discussed in section Latency. Entry and Transmission Community acquisition of HCMV follows mucosal exposure to virus that is shed into oral and genital fluids, urine, and breast milk. Thus, repeated exposures to infectious virus in saliva or urine leads to virus transmission in adults and young children. Individuals exposed to infants shedding virus and infants exposed to HCMV through breast-feeding are high-risk settings for infection. Approximately 50% of breast-fed infants born to HCMV seropositive women will acquire the virus in the first few months of life and subsequently shed virus in saliva and urine for prolonged periods of time during infancy, exposing others. The high incidence of transmission in these settings makes these important routes of community acquired infections
worldwide Rates of transmission between children less than 2 years of age are also elevated, likely the result of frequent exchange of saliva between young children.
In adults, sexual transmission has been documented with virus shed into both cervical secretions and semen.
Transfusion of blood products from HCMV infected donors has long been known to represent a significant risk for the acquisition of HCMV and as a result, blood products from noninfected donors or that are leukocyte depleted are now commonly employed for transfusion of at risk individuals such as premature infants and pediatric transplant recipients.
The detection of HCMV DNA by quantitative PCR is the most frequently employed approach for the diagnosis of HCMV infection, and serial measurements of viral DNA has largely replaced other assays for virologicalmonitoring patients at risk for invasive HCMV infection.
PREVENTION AND CONTROL
Antiviral agents have been used to control HCMV infections in allograft recipients, individuals with HIV/AIDS, and, more recently, infants with cCMV infections.
A recently approved antiviral agent, letermovir, has been shown to be of considerable value in HCMV prophylaxis in HCT recipients secondary to both its antiviral activity and, importantly,a lack of myelosuppression that is associated with ganciclovir therapy. Letermovir is a small molecule inhibitor that specifically inhibits the packaging of HCMV DNA but not rodent CMVs or other herpesviruses
Transmission is via intimate contact with infected secretions. Cytomegalovirus infections are among the most prevalent viral infections worldwide.