Epstein-Barr Virus
Etiology
Taxonomy
| Order = Herpesvirales | Family = Herpesviridae | Subfamily = Gammaherpesvirinae | Genus = Lymphocryptovirus | Species = Human Herpesvirus 4
Description
The Epstein-Barr virus (EBV) is one of the two human host-specific viruses in the subfamily Gammaherpesvirinae, along with Kaposi's Sarcoma, a virus normally associated with lesions in AIDS patients. It is the most common virus among the human population. More than 95% of the human population contain EBV antibodies, meaning that they have come into contact with the virus at some point in life and it is lying latent. Many people are asymptomatic when infected, but under certain stresses, diseases, such as mononucleosis, can arise. EBV was found to be the main virus responsible for Burkitt's Lymphoma in 1964, and later on was found to be correlative with Hodgkin's Lymphoma and nasopharyngeal carcinoma. EBV is not the sole cause of these cancers, but it does play an important role in their development. A defining marker of a virus is that it requires a host to replicate and survive, and when EBV was discovered, it was very difficult to grow on any medium.
Herpesviruses are characteristically icosahedral, 20-sided, and 70-100 microns in diameter, which led Epstein to characterize EBV with this family, however because he could not run standard tests of the other herpesviruses at the time, he concluded it must be a new strain [1].
Genome
EBV is a double-stranded DNA virus, making it more stable and less likely for mutations than RNA viruses. EBV is 184 kb pairs in length. The genome shows around 70 predictable open reading frames and there are two different strains. The strains differ in their latent proteins, but they are not associated with any specific disease. Analyzing repeat genes can be used in studying outbreaks [2]. The genome codes for latent and lytic proteins, and there are RNA transcription proteins whose functions are still unknown. It is an enveloped herpes virus, which means it can cause a life-long latent infection. EBV is very large for a herpesvirus and is surrounded by an outer layer comprised of cellular membranes from infected cells, adding an extra 50-100 nm to its size. The envelope is necessary for infectivity and sensitivity.
