Cytomegalovirus

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Classification: Cytomegalovirus, CMV, is a member of the family of human herpesviruses, and is known as human herpesvirus 5 (HHV-5). CMV is a Betaherpesvirinae, a subfamily of herpesviridae. This classification is based on its tendancy to infect mononuclear cells and lymphocytes and on its molecular phylogenetic relationship to other herpesviruses.(emedicine)

Description and significance: CMV is a virus which can produce congenital and acquired infection, and has therefore become an important pathogen of study. Learning about it, its phylogenic history, and and its genome gives us a greater understanding of the organism and can lead to the development of a working drug against this ubiquitous virus. (“History of Cytomegalovirus” pubmed) Human Cytomegalovirus strains were isolated by three independent scientists: Smith and Rowe in 1956 and Weller in 1957. It is named for the cytomegalic, or enlarged cells, that are characteristic of this virus. (“History of Cytomegalovirus” Pubmed) CMV is species specific and there are strains which affect humans, monkeys, and rodents. Human CMV can be found in almost all of the body's organs. It can also be found in body fluids, including semen, saliva, urine, feces, breast milk, blood, and secretions of the cervix. (healthofchildren.com) In pregnant women, CMV is also able to cross the placenta. Therefore, infection in a pregnant woman can lead to infection of the developing fetus.(healthofchildren.com)

Genome structure: CMV has a double stranded linear DNA genome. It is more the 240 kilobase pairs long making it the largest member of the herpesvirus family. It is capable of encoding more than 200 potential protein products, but the function of most of these proteins is presently unknown. There are many strains of CMV, each affecting different organisms. Different strains have slightly different genomes, but share about 80% of the genome. CMV is a double-stranded linear DNA virus with 162 hexagonal protein capsomeres surrounded by a lipid membrane. CMV has the largest genome of the herpes viruses, ranging from 230-240 kilobase pairs. Of the betaherpesviruses, CMV is the only class E genome, making it similar to herpes simplex 1. Human CMV is composed of unique and inverted repeats that include the existence of 4 genome isomers caused by inversion of L-S genome components (class E). Replication may be divided into immediate early, delayed early, and late gene expression based on time of synthesis after infection. The DNA is replicated by rolling circles. In vitro, CMV replicates in human fibroblasts.(emedicine) Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

Cell structure and metabolism: Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.

Ecology: Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology: It is an enveloped DNA virus. When the host is infected, CMV DNA can be detected with polymerase chain reaction (PCR) in all the different cell lineages and organ systems in the body. Upon initial infection, CMV infects the epithelial cells of the salivary gland, resulting in a persistent infection and viral shedding.(emedicine) Clinically significant CMV disease most often develops in immunocompromised patients such as those with HIV,or those who have had organ or bone-marrow transplantations. When it is symptamatic, CMV can affect almost every organ of the body. This can result in fever of unknown origin, pneumonia, hepatitis, encephalitis, myelitis, colitis, uveitis, retinitis, and neuropathy. (emedicine) CMV, like other herpesviruses, can establish a latent infection in the host, where it remains dormant and does not cause symptoms to the host. (emedicine) Cell-mediated immunity is considered the most important factor in controlling CMV infection. Patients deficient in cell-mediated immunity are at greatest risk for CMV disease. CMV-specific CD4+ and CD8+ lymphocytes play an important role in immune protection after primary infection or reactivation of latent disease. Studies of bone marrow transplant patients have revealed that patients who do not develop CMV-specific CD4+ or CD8+ cells are at higher risk for CMV pneumonitis. Additionally, no cases of CMV pneumonia have been reported in allogeneic marrow transplant patients receiving infusions of CMV-specific CD8+ cells.(emedicine) How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology: Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research: Enter summaries of the most recent research here--at least three required

References:

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500. Retrieved from "http://en.citizendium.org/wiki/Biggius_microbia"

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