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E protein Abbreviation for envelope protein.

E1 region A region mapping at the left-hand end of the conventional genome of adenovirus which encodes some 10 polypeptides required for cell transformation by adenovirus. Divided into two domains: E1A, which is required to immortalize cells in culture; and E1B, necessary for tumor formation.

E1A gene See E1 region.

Eagle's medium (basal medium) Simple chemically defined medium; used in growing many vertebrate cell lines.

early antigens The products of expression of early genes.

early enzymes Enzymes, especially in cells infected with bacteriophage, which are synthesized de novo under the direction of the invading virus genome.

early genes Viral genes which are expressed early in the replication cycle before nucleic acid replication occurs, e.g. the T antigen genes of SV40. Early gene products are usually involved in the replication of the viral nucleic acid. See late genes.

Eastern equine encephalomyelitis virus

(EEEV) A species in the genus Alphavirus, first isolated from the brain of an affected horse in 1933. Maintained in the wild as a harmless infection of birds, small rodents, reptiles and amphibia. Causes encephalitis in humans, horses, pigeons and pheasants. Man and horses are infected by mosquito bites. In horses there is viremia and fever followed by involvement of the CNS. Strains vary in virulence but mortality can be 90%. In humans the disease is similar, with high mortality, 30-50%. Most survivors show paralytic or mental sequelae. There are about five encephalitic cases a year in the

USA with more than 100 inapparent infections determined serologically. Outbreaks with high mortality occur in pheasants. The virus is found in eastern USA, the Caribbean, Central America and north and eastern S America. In North America the principal vector is the swamp mosquito, Culiseta melanura, and the reservoir hosts are birds. In the Caribbean Culex taeniopus is the principal vector. Mice, guinea pigs, goats, chicks, snakes and turtles can be infected experimentally. In birds the virus infects the viscera (liver) rather than the CNS. Virus can be propagated in eggs and a variety of tissue cultures in which it causes CPE. Vaccines are available for horses, pheasants and human laboratory workers exposed to EEEV.

Scott TW and Weaver SC (1989) Adv Virus Res 37, 277

Weaver SC (1997) In Viral Pathogenesis, edited by N Nathanson et al. Philadelphia: Lipincott-Raven, p. 329

EB-3 cells (CCL 85) A cell line of lym-phoblast-like cells, derived from a 3-year-old black male with Burkitt's lymphoma. The cells harbor a herpes-like virus particle detected by electron microscopy.

EBNA Epstein-Barr virus-induced nuclear antigen. A neoantigen complex associated with the chromatin of latently infected lymphoblastoid cells carrying the EBV (human herpes virus 4) viral genome. The EBNA complex consists of at least six virus-specified polypeptides, which differ in structure dependent upon the inducing virus strain. The best characterized of the polypeptides are known as EBNA-1 and EBNA-2, both of which seem to elicit humoral antibodies in infected individuals. EBNA-1 is a phos-phorylated polypeptide consisting of 641 amino acids, which can be seen diffusely associated with cell chromosomes at metaphase. EBNA-2 polypeptide consists of 443 (in EBV-2) or 491 (in EBV-1) amino acids and is also phosphorylated.

EBNA

Although the precise function of these proteins is not known, EBNA-1 is a DNA-binding protein which is involved in the initiation of EBV DNA replication, and EBNA-2 seems to function as a trans-activator of virus gene expression. There are three related genes for EBNA-3 tandemly located in the EBV genome (EBNA-3A, EBNA-3B and EBNA-3C), which specify large proteins (900-1000 amino acids each) of presently unknown function.

'Ebola-like viruses' A genus in the family Filoviridae. The type species is Zaire Ebola virus (ZEBOV). Differ from 'Marburg-like virus'. There are nine distinguishing features:

(1) almost no antigenic cross-reactivity with Marburg virus;

(2) virion length is about 970 nm as opposed to 790 nm with Marburg virus;

(3) genome length of 18.9 kb as opposed to 19.1 kb with Marburg virus;

(4) several gene overlaps as opposed to a single overlap with Marburg virus;

(5) glycoprotein expression involves transcriptional editing;

(6) transcription of only the first ORF of gene 4 yields a soluble small glycoprotein not observed with Marburg virus;

(7) protein profile distinct from Marburg virus; however species specific;

(8) glycoprotein gene nucleotide sequence difference of 57% compared with Marburg virus;

(9) fatality rates for humans 50-90% with species Sudan Ebola virus and Zaire Ebola virus, respectively.

Species Reston Ebola virus appears to be nonpathogenic for humans. There are four distinct species in the genus, Côte d'Ivoire Ebola virus, Reston Ebola virus, Sudan Ebola virus and Zaire Ebola virus.

Ebola virus (EBOV) A species in the genus Filovirus morphologically indistinguishable from Marburg virus, but immunologically and phylogenetically different. The name comes from a small river in Zaire near which the virus was first isolated. Causes a severe and often fatal hemorrhagic fever in humans. Epidemics occurred in the Sudan and Zaire in 1976. Incubation period is 7-14 days. There is headache, limb and back pains, diarrhea, vomiting and extensive internal bleeding. Recovery is slow. The disease was less severe in the Sudan than in Zaire, and the virus isolated from Sudanese patients (Sudan Ebola virus) produced a lower mortality rate in rhesus monkeys than did virus from patients in Zaire (Zaire Ebola virus). In 1976 in northern Zaire there were 318 human cases with 88% mortality, and in southern Sudan there were 284 cases with 53% mortality. Phylogenetic analysis of these viruses shows that they are quite different, and they are now considered to be distinct species of Ebola virus. In some other characteristics the viruses are indistinguishable. The Zaire Ebola virus reappeared and was recognized as a single fatal case in Tandala, Zaire in 1977, then in 1979 the Sudan Ebola virus reappeared in southern Sudan affecting 34 people and causing 65% mortality in the same area as the original 1976 outbreak. The Sudan Ebola virus reappeared again in 2000 in Gulu, Uganda (see below). In 1989, 1991 and 1996, closely related viruses were isolated from outbreaks of hemorrhagic fever in captive cynomolgus monkeys imported to Reston, VA, Alice, TX, USA and Milan, Italy from the Philippines. These viruses are currently termed Reston Ebola virus, and appear to form a phylogenetically distinct subtype when compared to Sudan Ebola and Zaire Ebola viruses. Ebola in humans reappeared in 1994 when a single non-fatal case occurred in a Swiss ethologist after she performed a necropsy on a dead chimpanzee in the Tai Forest, Côte d'Ivoire. The virus recovered from this case was different from Zaire, Sudan or Reston Ebola and is now considered to be a fourth Ebola virus species, Côte d'Ivoire Ebola virus. A further chimpanzee-related outbreak occurred in Gabon in 1996. In 1995 a large outbreak of Ebola hemor-rhagic fever was recognized in Kikwit, Zaire, with 316 cases and 77% mortality. The virus was found to be almost indistinguishable genetically from the 1976 Zaire Ebola species. Then in 2000 another large outbreak of Sudan Ebola virus began in Gulu, Uganda, with 428 cases and 173 deaths. Transmission requires very close contact with an infected monkey or person. The natural reservoir of infection is unknown. Diagnosis is by antigen capture ELISA or polymerase chain reaction of acute sera, IgM or IgG ELISA of paired (acute and convalescent) sera or inoculation into Vero cells followed by an IFA test. The virus may be isolated in the laboratory by inoculation of patients' sera into guinea pigs or Vero cells. The virus has a negative-strand RNA genome 19kb in length encoding seven major proteins, in the order: 3'-NP, VP35, VP40, GP, VP30, VP24 and L-5'. There is also a non-structural secreted glycoprotein (SGP) of unknown function. A DNA-based vaccine under development has protected monkeys from a challenge infection. A novel diagnostic assay to detect Ebola virus in skin has been described. Synonym: Maridi virus.

Feldmann H et al (1998) In Virology, vol. 1 of Topley & Wilson's Microbiology and Microbial Infections, Ninth edition, edited by BWJ Mahy and L Collier. London: Arnold, p. 651 Sullivan NJ et al (2000) Nature 408, 605 Xu L et al (1998) Nature, Medicine 4, 37 Zaki SR et al (1999) J Inf Dis 179 (Suppl 1), S36

EBTr(NBL-4) cells (CCL 44) A heteroploid bovine cell strain derived from minced whole trachea of a male fetus of Bos taurus. Cells decline beyond the 55th passage.

EBV Abbreviation for Epstein-Barr virus. See Human herpesvirus 4.

ecboviruses (enteric cytopathic bovine orphan viruses) Synonym for Bovine enterovirus, a species in the genus Enterovirus. There are two serotypes, but neither has been associated with disease in cattle.

echinoviruses A name proposed, but not adopted, for the group of syncytial or foamy viruses in the genus Spumavirus. The name refers to the presence of long projections or spines on the surface of the virus particle.

echovirus 1 A serotype of Human enterovirus B.

echovirus 4 (EV4) A serotype of Human enterovirus B. Has caused outbreaks of aseptic meningitis with gastrointestinal symptoms in about 70% of cases.

Chin TDY et al (1957) Am J Hyg 66, 76 Johnsson T (1957) Lancet i, 590

echovirus 6 (EV6) A serotype of Human enterovirus B. Causes outbreaks of aseptic meningitis in children and adults. Gastrointestinal symptoms are uncommon. Localized muscle weaknesses and maculopapular rashes have been observed in some outbreaks. Resembles coxsackie virus in causing Bamble disease and carditis in humans, and in being pathogenic for suckling mice.

Kibrick S et al (1957) Ann NY Acad Sci 67, 311

echovirus 7 A serotype of Human enterovirus B. Sequence of this virus has been reported to occur in spinal cord of patients with ALS.

Berger MM et al (2000) Neurology 54, 20

echovirus 8 (EV8) A serotype of Human enterovirus B. Isolated from patients with respiratory and intestinal symptoms. Subsequently shown to be identical to echovirus 1.

echovirus 9 (EV9) A serotype of Human enterovirus B. Caused widespread epidemic aseptic meningitis in Europe in 1955 and 1956, and in America in 1957. There was often a maculopapular rash. Unlike the prototype strain, many isolates can be adapted to produce coxsackie A-type disease in newborn mice. Antigenically identical to coxsackie A23 virus.

echovirus 10 Reclassified as a strain of reovirus type 1.

echovirus 11 (EV11) A serotype of Human enterovirus B. When it causes disease it is usually in infants or young children. Meningeal symptoms are most common, but fever, respiratory or gastrointestinal symptoms may occur. Sometimes associated with Bamble disease. Related by sequence homology to coxsackie A9. Synonym: U virus.

Dahlund L et al (1995) Virus Res 35, 215 Nagington J et al (1968) Lancet ii, 725

echovirus 16 (EV16) A serotype of Human enterovirus B. Caused the 'Boston Exanthem': an outbreak of fever, aseptic meningitis and a maculopapular rash which did not appear until the fever was over.

Neva FA and Enders IF (1954) J Immun 72, 307

echovirus 18 (EV18) A serotype of Human enterovirus B. Viruses isolated from two outbreaks of gastroenteritis and designated N5 and D-3 proved to be echo 18. Probably a cause of gastroenteritis in infants. Infection often associated with skin rashes.

Eichenwald HF (1958) J Am Med Assoc 166, 1563

echovirus 19 (EV19) A serotype of Human enterovirus B. Isolated originally from an infant with diarrhea and later from the CSF of an adult male patient. Has been associated with cases of mild respiratory disease and diarrhea mainly in children.

Cramblett HG et al (1962) Arch Int Med 110,574

echovirus 20 (EV20) A serotype of Human enterovirus B. Isolated from the stools of children with fever, coryza and diarrhea. In adult volunteers infection caused mainly constitutional symptoms, but some had 'colds' or gastrointestinal symptoms. Synonym: JVI virus.

Buckland FE et al (1961) BMJ i, 397

echovirus 21 (EV21) A serotype of Human enterovirus B. Isolated in Massachusetts, USA from a child with meningitis.

Kibrick S (1964) Prog Med Virol 6, 27

echovirus 22 and 23 (EV22 and 23) These viruses have been associated with outbreaks of respiratory disease in young children. They have some of the characteristics of coxsackie A viruses which they resemble in their reaction to 2-a-hydroxy-benzyl benzimidazole and the nuclear changes produced in infected cell cultures. Sequence analysis suggests that they are distinct from prototype echoviruses and they have been reclassi-fied as human parechoviruses 1 and 2 in a new genus, Parechovirus.

Stanway G et al (1994) J Virol 68, 8232

echovirus 25 (EV25) A serotype of Human enterovirus B. Has been associated with rashes in infants. Infection of human volunteers has caused fever, pharyngitis and cervical adenitis.

Kasel IA et al (1965) Proc Soc Exp Biol Med 118, 381

echovirus 28 Now reclassified as human rhinovirus strain 1A. Isolated in a primary rhesus monkey cell culture at the Naval Medical Research Unit No. 4, Great Lakes, Illinois, USA from a nasal washing from a young man with a mild respiratory infection.

echovirus 34 A serotype of coxsackie virus A 24 in the genus Human enterovirus C.

echoviruses 1-7, 9, 11-27, 29-33 (EV-1 to -7, 9, 11-27, 29-33) (enteric cytopathic human orphan virus). Serotypes in the genus Enterovirus. There are 33 numbered serotypes, but serotype 8 was found to be identical to echovirus 1, serotypes 10 and 28 are now reclassified as reovirus type 1 and rhinovirus type 1A, respectively, and serotypes 22 and 23 are reclassified as human parechoviruses 1 and 2. Frequently isolated from fecal specimens in primary monkey kidney cell cultures but some strains replicate better in human amnion cells. Originally thought to be non-pathogenic, they may rarely cause aseptic meningitis, encephalitis, respiratory disease, exanthem, gastrointestinal symptoms, pericarditis and myocarditis. Do not produce disease in suckling mice. Newly recognized enteroviruses, from type 68, are no longer assigned a coxsackie or echovirus number. Many strains of types 3, 6, 7, 10, 11, 12, 13, 19, 20, 21, 29, 30 and 33 agglutinate human O erythrocytes at 4°C. A strain of type 9 has been adapted to suckling mice and causes a disease similar to that produced by a coxsackie A virus. Focal lesions can occasionally be produced by some strains on inoculation into the brain or spinal cord of monkeys. Types 4, 6 and 9 have been associated with outbreaks of aseptic meningitis. Types 11, 22 and 25 have been associated with respiratory illness. Type 18 was recovered from infants with diarrhea. Type l6 caused the 'Boston Exanthem' fever with a maculopapular rash. Data on the history of various strains is available in Strains of Human Viruses. Synonym: echoviruses.

Edmonston virus

Majer M and Plotkin SA (1972) Strains of Human Viruses. Basel: S Karger.

eclipse period The time after infection between the disappearance of the infecting virus and the appearance of new intracellular virus infectivity. The infecting virus loses its infectivity soon after penetration and for some time no infective virus can be demonstrated. See also latent period.

Doermann AH (1952) J Gen Physiol 35, 645

ecmoviruses (enteric cytopathic monkey orphan viruses) Synonym for simian enteroviruses.

ecotropic murine type C virus A subspecies of mouse type C oncovirus in the genus Gammaretrovirus. Infects and replicates in cultures of mouse and rat cells only, unlike the amphotropic murine type C virus which will also replicate in non-murine cells.

Synonym: mouse-tropic strain. Cf. xenotropic murine type C viruses.

Bryant ML et al (1978) Virology 88, 389

ecpoviruses (enteric cytopathic porcine orphan viruses) Synonym for porcine enteroviruses.

ecsoviruses (enteric cytopathic swine orphan viruses) Synonym for porcine enteroviruses.

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