Neurolymphomatosis of fowls virus

Synonym for Gallid herpesvirus 2.

neurotransmitters Small molecules liberated at nerve endings that diffuse to neighboring cells and trigger a specific response. Examples are acetylcholine, epinephrine, norepinephrine, dopamine and gamma-aminobutyrate (GABA).

neurovaccinia virus A strain of Vaccinia virus, in the genus Orthopoxvirus, more virulent than other vaccinia viruses. Produces flat, ulcerated pocks on the CAM, with a tendency to hemorrhage.

neutralization Usually understood to mean neutralization of infectivity by combination of virus with specific antibody. On the surface of the virus particle there may be several antigens, and neutralization

antibodies to some of these can combine without causing loss of infectivity. However, such an infective antigen-antibody complex may be neutralized if either complement or an antibody against the first antibody binds to the complex. In such a case the neutralization may be due to virolysis of an enveloped virus, or to steric hindrance due to the build-up of protein molecules. This type of neutralization is described as 'extrinsic' in contrast to 'intrinsic' neutralization in which there is a direct inactivation reaction between antibody and a vital site on the virus. Virus particles may be agglutinated without losing infectivity, but this will result in a fall in the titer of infectivity units. This process is described as 'pseudoneutralization'. The initially formed virus-antibody union is dissociable, but with time the binding becomes firmer, although some dissociation of a small amount of infective virus can still occur. See also non-neutraliz-able fraction and neutralization test.

Cleveland SM et al (2000) Virology 266, 66 Dimmock NJ (1995) Rev Med Virol 5, 165

neutralization test Used to measure infec-tivity neutralizing capacity, usually of specific antibody. Virus and antiserum are mixed, and surviving infectivity, if any, is tested for by inoculation of animals, eggs or cell cultures. The amount of virus or antibody is kept constant, but the other component is varied to obtain a titer of neutralizing activity which will be expressed as the serum dilution required to neutralize a certain number of infective doses of virus, or as the number of infective doses of virus neutralized by a certain amount of antiserum. A virus control with no antiserum is required, and the test is read when the control becomes positive because the virus may later break through the neutralizing action of the antibody, and the apparent titer of the antiserum will fall. See also non-neutral-izable fraction.

neutralizing antibody An antibody which inhibits the infectivity of a virus.

neutral red A photoreactive dye. See pho-todynamic inactivation.

neutroseron A name proposed for any group of viruses which cross-react in neutralization tests. No longer in use.

Nevirapine A non-competitive nucleoside inhibitor of reverse transcriptase that interacts with tyrosine residues on the enzyme. In clinical trials against HIV, resistant mutants rapidly developed, but it was effective when used in combination with AZT. Recommended as a single dose to prevent perinatal transmission of HIV. Has caused severe liver damage and other adverse events in some healthcare workers taking high doses prophylactically. Synonyms: BI-RG-587; Viramune.

Anon (2001) MMWR 49, 1153 Merluzzi vJ et al (1990) Science 250,1411

newborn pneumonitis virus Synonym for Human parainfluenza virus type 1.

Newbury agent-2 (NA-2) A strain of bovine enteric calicivirus. An unassigned species in the family Caliciviridae.

Dastjerdi AM et al (1999) Virology 254, 1

Newbury virus A strain of bovine enteric calicivirus. An unassigned species in the family Caliciviridae.

Woode GN and Bridger JC (1978) J Med Microbiol 11, 441

Newcastle disease virus (NDV) A species in the genus Rubulavirus. A highly contagious natural infection of fowls, turkeys and other species of birds. Strains have antigenic differences and vary in virulence. The strains of low pathogenicity are termed 'lentogenic', those of medium pathogenicity 'meso-genic', and highly pathogenic strains 'velogenic'. These differences are mostly determined by the sequence at the cleavage site of the Fo protein, with high cleavability correlated with high virulence. Global panzootics occurred first in 1926 (originating in Java then spreading to Newcastle-upon-Tyne, UK) then in 1973 and 1979 (both originating in the Middle East). Highly pathogenic (velo-genic) strains caused epidemics among double-crested cormorants over a wide area of central North America in 1990 and 1992, and in Saskatchewan, Canada in 1995. Large outbreaks occurred in New South Wales, Australia during 1998-2000. Disease produced is primarily respiratory but signs of nervous system involvement may be seen. The eyes are closed, there is nasal discharge and watery diarrhea. Virus is shed in all secretions and excretions for up to 4 weeks. Spasms and paralysis may occur. Mild strains cause low mortality but reduce egg production. Most avian species appear to be susceptible. Infection of the conjunctiva has been reported in poultry and laboratory workers. Experimental i.c. injection in hamsters and mice causes encephalitis which is not transmissible. Transmission is through drinking water or inhalation of dust. Control is by slaughter or use of attenuated vaccines that can be administered by aerosol or in drinking water. Most strains replicate readily in eggs or chick cell cultures in which they produce CPE. Replication also occurs in many species of mammalian cells. Cultures may remain latently infected for long periods. All strains agglutinate fowl ery-throcytes; some agglutinate a variety of avian and mammalian cells. Human ery-throcytes treated with some strains are agglutinated by serum from infectious mononucleosis patients. Synonyms: atypischen geflugelpest virus; avian pneumoencephalitis virus; ranikhet disease virus; fowlpest virus; avian paramyxovirus 1.

Emmerson PT (1999) In Encyclopedia of Virology, Second edition, edited by A Granoff and RG Webster. London: Academic Press, p. 1020

Gould AR et al (2001) Virus Res 77, 51

New Jersey virus See Vesicular stomatitis New Jersey virus.

New Minto virus (NMV) An unassigned species in the family Rhabdoviridae, belonging to the Sawgrass group. Isolated from the tick, Haemaphysalis lep-orispalustris, removed from snow-shoe hares, Lepus americanus, in central Alaska. Sensitive to sodium deoxy-cholate. Kills suckling mice on i.c. but not on i.p. injection. Weaned mice do not die after i.c. injection. Produces plaques in Vero cells but not in Pekin duck embryo cells. Antigenically related to sawgrass virus and Connecticut virus.

Ritter DG et al (1978) Can J Microbiol 24, 422

newt viruses T6 to T20 Various viruses have been isolated from newts which may be strains of Frog virus 3, but they require further characterization.

New variant Creutzfeldt-Jakob disease (nvCJD) A new disease announced by an expert advisory committee to the UK government on 20 March, 1996 based on the recognition of 10 persons with onset of a new form of CJD with characteristic pathological brain lesions. Molecular analysis showed that nvCJD is caused by a prion indistinguishable from the causative agent of bovine spongiform encephalopathy. More than 100 cases have now been described, all fatal, the majority in young persons below the age of 30. The cases are widely distributed geographically with no obvious common risk so far, apart from one cluster in Queniborough, Leicestershire, UK. See prion diseases.

Will RG et al (1996) Lancet 347, 921

New World arenaviruses South American arenaviruses belonging to the Tacaribe complex (Table N1).

Table N1. New World arenaviruses

Amapari

Parana

Flexal

Pichinde

Guanarito*

Pirital

Junin*

Sabia*

Latino

Tacaribe

Machupo*

Tamiami

Oliveros

Whitewater Arroyo*

* Denotes highly pathogenic hemorrhagic fever-inducing viruses.

* Denotes highly pathogenic hemorrhagic fever-inducing viruses.

New World hantaviruses North and South American viruses belonging to the Hantavirus genus. Many are highly pathogenic, causing hantavirus pulmonary syndrome, a disease with about 40% mortality (Table N2).

New York virus (NYV) A species in the genus Hantavirus. Identified as the cause of fatal hantavirus pulmonary syndrome in a Rhode Island patient

Table N2. New World hantaviruses

Andes*

CaƱo Delgadito

Laguna Negra

Prospect Hill

Araraquara*

Castelo dos Sonhos*

Lechiguanas*

Rio Mamore

Bayou*

Choclo*

Maciel

Rio Segundo

Bermejo

Isla Vista

Muleshoe

Seoul

Black Creek Canal*

El Moro Canyon

New York*

Sin Nombre*

Blue River

Hu39694*

Oran*

Calabazo

Juquitiba*

Pergamino

'Denotes highly pathogenic hantavirus pulmonary syndrome-inducing viruses.

'Denotes highly pathogenic hantavirus pulmonary syndrome-inducing viruses.

probably infected in Shelter Island, New York. Genetically and antigenically distinct from Sin Nombre virus. The rodent host is Peromyscus leucopus (eastern hap-lotype).

Hjelle B et al (1995) J Virol 69, 8137

Nexo-Cendo configuration A trans-membrane protein with the N-terminus external to the membrane and the C-terminus endocytoplasmic.

den Boon JA et al (1991) Virology 182, 655 Escors D et al (2001) J Virol 75, 1312

NF-kB A pleiotropic transcription factor that is active in the nucleus of mature B lymphocytes, differentiated monocytes and some T-cell lines. Named because it was originally found to switch on genes for the k class of immunoglobulins in B lymphocytes. Involved in the response of lymphoid cells to a variety of stimuli. The oncogene of avian reticuloendothe-liosis virus, v-rel, specifies a v-REL protein that is related to NF-kB, and causes acute fatal neoplasia in infected birds.

Ngaingan virus (NGAV) An unassigned vertebrate rhabdovirus. Isolated from Culicoides sp in Queensland, Australia. Antibodies present in wallabies, kangaroos and cattle. Not reported to cause disease in humans.

Ngari virus (NRIV) A serotype of Bunyamwera virus in the genus Bunyavirus. Isolated from male mosquitoes, Aedes simpsoni, in Senegal. Also found in Burkina Faso, Central African Republic and Madagascar. Isolated from other Aedes sp and also Anopheles sp. Not reported to cause disease in humans.

Institut Pasteur, Dakar (1984) Annual Report

Ngoupe virus (NGOV) A serotype of Eubenangee virus in the genus Orbivirus. Isolated from Aedes tarsalis in the Central African Republic.

Institut Pasteur, Dakar (1975) Annual Report nick A break in a single strand of nucleic acid, especially one strand of a double-stranded nucleic acid.

nickase An enzyme that introduces singlestrand breaks into double-stranded DNA.

Nicolau bodies Intranuclear or intracyto-plasmic inclusion bodies found in cells infected with Human herpesvirus 1,2 or 3.

Nidovirales An order comprising the families Arteriviridae and Coronaviridae, which share various structural and replicative features. They have linear, non-segmented, positive-sense single-stranded RNA genomes. The gene order from 5' to 3' consists of a replicase gene followed by the structural and non-structural protein genes. Replication involves a 3' cotermi-nal nested set of four or more subgenomic RNAs (which give the name Nido from Latin nidus meaning nest, to the Order). The genomic RNA is the mRNA for translation of the replicase. There is a virion envelope with an integral membrane protein that spans the membrane at least three times. There are two genera, Coronavirus and Torovirus, in the family Coronaviridae, and only one, Arterivirus, in the family Arteriviridae.

Cavanagh D (1997) Arch Virol 142, 629

Nigerian horse virus A virus isolated from the brain of a horse with sporadic meningoencephalomyelitis (staggers) by i.c. inoculation of suckling mice. Probably

NK virus the cause of staggers in horses in Nigeria; may be a strain of Borna disease virus. Not known to cause disease in humans.

Porterfield JS et al (1958) Br Vet J114, 425

Nigg's virus Not a virus. Synonym for mouse pneumonitis agent. A chlamydia of subgroup A.

Niigata virus A virus isolated from an outbreak of gastroenteritis in Japan. Could be passed in humans.

Kojima S et al (1948) Jap Med J1, 467

Nile crocodilepox virus (CRV) An unas-signed virus in the family Poxviridae.

Nipah virus An unassigned species in the family Paramyxoviridae. Isolated in March 1999 from the brain of a patient who died in Sg Nipah village, Bukit Pelandok, Malaysia during a large outbreak of human encephalitis with 105 fatalities amongst 265 cases. Because of an associated outbreak of disease in pigs, the virus was initially thought to be Japanese encephalitis virus, but was found to cause syncytia in Vero cells and to show positive fluorescence in an IFA test using antiserum made against Hendra virus. Subsequent molecular characterization confirmed that Hendra virus and Nipah virus are closely related, though distinct, species that represent a new genus of the Paramyxoviridae. Nipah virus first emerged in domestic pigs in 1997 when a respiratory disease was noted by farmers. The disease spread amongst pigs during 1998, becoming epizootic in September when the first human cases of encephalitis were noted. 11 confirmed cases also occurred in abattoir workers handling Malaysian pigs in Singapore, with one fatality. The disease in pigs has a relatively low mortality rate (< 5%) compared to the disease in humans (> 40%). Pigs develop rapid, labored breathing and an explosive non-productive cough as the main symptoms, but some neurological changes can be observed including lethargy or aggressive behavior. In humans, who appear to contract the disease only from direct contact with pigs or pig excretions (no transmission by human-human contact has been demonstrated), there is a febrile encephalitis which rapidly progresses to multisystem involvement with vasculitis and syncytial giant cell formation at various sites. Spread to the brain is by the vascular route and leads to diffuse small foci of necrosis and neuronal degeneration. The disease epidemic was stopped in May 1999 by the slaughter of more than a million pigs. The reservoir of natural infection seems to be the large fruit-eating bat, Pteropus hypomelanus, but other species of Megachiroptera may also be involved, as is the case with Hendra virus in Queensland, Australia. The reason for the sudden appearance in farmed pigs is unknown. The genome of Nipah virus is a negative-sense single-stranded RNA molecule 18 246 kb in length. The nucleotide sequence homol-ogy compared to Hendra virus ranges from 70 to 88% in the gene open reading frames's which are arranged 5'-N-P-C-V-M-F-G-L-3', and the intergenic regions are identical in the two viruses. Although Nipah and Hendra viruses are closely related, they are clearly distinct from any of the established genera within the Paramyxoviridae.

Chua KB et al (2000) Science 288, 1432 Harcourt BH et al (2000) Virology 271, 334 Paton NI et al (1999) Lancet 354,1253

Nique virus (NIQV) A strain of Candiru virus in the genus Phlebovirus, member of the sandfly fever serogroup, Candiru complex. Isolated from flies Lutzomyia panamensis in Panama. Not reported to cause disease in humans.

nitric oxide synthase An inducible enzyme activity which has been reported to be associated with brain infection by Borna disease virus and Rabies virus.

Koprowski H et al (1993) Proc Natl Acad Sci 90, 3024

nitrocellulose A nitrated derivative of cellulose which is used either as a powder or is made into membrane filters of defined porosity. Used to bind nucleic acids in Northern blotting and Southern blotting procedures and proteins in Western blotting.

NK virus A strain in the genus Polyomavirus, similar to MG virus.

Nkolbisson virus (NKOV)

Nkolbisson virus (NKOV) An unassigned species in the family Rhabdoviridae, belonging to the Kern Canyon serogroup. Isolated from mosquitoes near Yaounde, Cameroon. Not reported to cause disease in humans.

NMH10 A strain of Sin Nombre virus in the genus Hantavirus.

NMR-11 virus A strain of Sin Nombre virus in the genus Hantavirus.

Nodaviridae A family of RNA viruses with two genera: Alphanodavirus, consisting of viruses isolated only from insects, and Betanodavirus, consisting of viruses isolated from juvenile marine fish, in which they cause nervous necrosis disease (see Table N3).

Table N3. Fish nervous necrosis viruses

Atlantic halibut

Barfin flounder

Dicentrarchus labrax (Sea bass)

Japanese flounder

Lates calcarifer (Barramundi)

Malabar grouper

Redspotted grouper

Striped jack

Tiger puffer

All are species in the genus Betanodavirus, except Atlantic halibut and Malabar grouper viruses, which are tentative species.

nodule-inducing mouse mammary tumor virus A strain of virus in the genus Betaretrovirus found in mice freed from Mouse mammary tumor virus by foster nursing. These mice develop mammary tumors late in life. The virus is morphologically identical to Mouse mammary tumor virus but induces only hyperplastic nodules with low neoplastic potential.

Nola virus (NOLAV) A serotype of Bakau virus in the genus Bunyavirus. Isolated from Culex perfuscus in Central African Republic. Not known to cause disease in humans.

nomenclature The names of viruses have developed in a haphazard manner over the century since they were discovered, from descriptions of the disease (e.g. Yellow fever virus) to names of individual virologists (e.g. Rous sarcoma virus) or the place where they were first discovered (e.g. Marburg virus). In recent years, emphasis on the disease or the name of the investigator has generally been dropped, and newly discovered viruses have received a place name (e.g. Nipah virus), though a prominent exception was the virus causing hantavirus pulmonary syndrome, not welcomed by the local affected population and finally called Sin Nombre (no name) virus. For the last 30 years the ICTV (and its predecessor the ICNV) has developed a framework of rules that govern the officially recognized names of viruses. A stable scheme using English virus family, subfamily, genus and species names has evolved: family names have the suffix viridae, subfamily virinae, and genus virus. This taxonomic scheme is both easy to use in practice, and valuable to the discipline of virology.

Pennington TH (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. 23 van Regenmortel MHV et al (2000) Virus Taxonomy, Classification and Nomenclature of Viruses, Seventh Report of the ICTV. San Diego: Academic Press

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