Subacute myeloopticoneuropathy virus

(SMON) A herpesvirus isolated from the feces and CSF of patients with subacute myelo-optico-neuropathy. Seen mainly in Japan, the disease is characterized by sensory disturbance, especially of the lower part of the legs, abdominal symptoms, decreased muscle strength and bilateral impairment of visual acuity. There are no changes in the blood or CSF. There is degeneration of posterior and lateral tracts of the spinal cord. The virus was isolated in BAT-6 cells and causes a thinning of the cell sheet. On injection into newborn C57Bl/6 mice it is reported to cause paralysis of the hind legs. It is claimed that the virus can be derived on passage of avian infectious laryngotra-cheitis virus on the CAM or in newborn C57BL/6 mice. It is antigenically related to this virus but is said to differ from it in being non-pathogenic for fowls, less unstable at low pH and pathogenic for C57BL/6 mice. The role of the virus in subacute myelo-optico-neuropathy has been questioned and it is suggested that the disease is due to the administration of clioquinol, an antidiarrheal drug. When the use of clioquinol was stopped in Japan in September 1970, incidence of the disease fell dramatically. However, clio-quinol is used outside Japan and appears to cause little disease. Synonym: Inoue-Melnick virus.

Inoue YK (1975) Prog Med Virol 21, 35 Kono R (1975) Lancet ii, 370

subacute sclerosing panencephalitis virus (SSPE) Measles virus is the cause of SSPE, a slow virus disease of the brain. Vaccinated children are much less likely to develop SSPE than the unvaccinated. The disease is more common in patients who have measles before the age of 2 years. The majority of cases appear 6-8 years after acute measles, with an incidence in unvaccinated children of 1 in 1 million cases. More likely to occur in boys than girls. Measles virus can be isolated from the brain in cases of SSPE but only by co-cultivation of brain cells with susceptible target cells. It seems that host cell-dependent attenuation of Measles virus gene expression and function occurs which determines persistence in the brain. Some SSPE strains of Measles virus are neurovirulent in ferrets and these strains are strongly cell-associated.

Baczko K et al (1993) Virology 197, 188 Schneider-Schaulies S et al (1994) Semin Virol 5, 273

subacute spongiform encephalopathy viruses Synonym for spongiform ence-phalopathy viruses.

subgenomic RNA A species of RNA of less than genome length found in RNA virus-infected cells. The genome RNA of several groups of positive-strand RNA viruses (Togaviridae, Retroviridae and Caliciviridae, for example) contains more than one initiation site, but early in infection only the portion of the RNA coding for RNA-replicating enzymes is translated. Subsequently, subgenomic RNA containing the previously masked initiation site is synthesized and can then be translated into virus coat proteins. In togaviruses, this RNA has been termed

'interjacent RNA'. The several mono-cistronic species of mRNA synthesized by transcription from full-length genome RNA in cells infected with some negative-strand viruses, such as Para-myxoviridae and Rhabdoviridae, may also be termed subgenomic RNA. See interjacent RNA.

submaxillary virus See Cytomegalovirus.

suckling mouse cataract virus An unusual type of mycoplasma isolated from rabbit ticks, Haemaphysalis leporis-palustris, in Georgia, USA. Replicates to high titer in chick embryos. Causes cataracts in suckling mice after 20 days, sometimes with signs of neurological involvement and stunting of growth. Passes through filters of APD 220nm but not at APD 100nm. Electron microscopy reveals mycoplasma-like bodies.

Bastardo JW et al (1974) Infect Immun 9, 444 Clark HF (1974) Prog Med Virol 18, 307

Sudan Ebola virus (SEBOV) A species in the genus 'Ebola-like viruses', which caused a major outbreak of Ebola hemor-rhagic fever in Sudan in 1976. See Ebola virus.

Sudan Ebola virus Boniface An isolate of Sudan Ebola virus from a patient named Boniface.

Sudan Ebola virus Maleo An isolate of Sudan Ebola virus from a patient named Maleo.

Suid herpesvirus 1 (SuHV-1) A species in the genus Varicellovirus. A natural infection, mainly of pigs, but cattle, horses, sheep, dogs, cats, foxes and mink are also susceptible. Endemic in pig populations throughout the world. In pigs the infection is usually silent, but in 5-10% the virus infects the tonsils from which it spreads to the CNS. There are nervous symptoms and fever but the pigs recover. Causes abortion in up to 50% of pregnant sows. In cattle, sheep and carnivores the disease is usually fatal, with intense pru-ritis (known as 'mad itch'). There are reports of infection in laboratory workers who developed aphthae of the mouth and local pruritis. Rabbits, guinea pigs and many other species are susceptible experimentally. Monkeys infected intra-nasally develop ataxia, salivation and have convulsions, but there is no pruritis. Virus replicates on the CAM with plaque production and CPE in cultures of chick, rabbit, guinea pig and dog cells. All strains appear antigenically similar. The virus has provided a valuable model for studies of the spread of viruses through the nervous system.

Synonyms: herpesvirus suis; Aujeszky's disease virus; infectious bulbar paralysis virus; mad itch virus; pig herpesvirus 1; porcine herpesvirus 1, pseudorabies virus.

Enquist LW et al (1999) Adv Virus Res 51, 237 Pensaert MB and Kluge JP (1989) In Virus Infections of Porcines, edited by MB Pensaert. New York: Elsevier suid herpesvirus 2 (SuHV-2) An unas-signed species in the family Herpesviridae. Causes rhinitis and destruction of the turbinates, with distortion of the snout, epistaxis and sneezing, notably in 2-week-old piglets, when death is common. Transmission is possible in piglets but not in adult pigs. Disease occurs in outbreaks and inclusions are present in the cells of many organs. Can be cultivated in primary pig cell cultures, replicating better in epithelial than in fibroblastic cells. Synonyms: inclusion-body rhinitis virus; swine cytomegalovirus.

Suipoxvirus A genus in the subfamily Chordopoxvirinae containing the Swinepox virus. Virions are brick-shaped, about 300 x 250 x 200nm. DNA 175kb in length with inverted terminal repeats of 5kb. Virus forms foci in pig kidney cell cultures and plaques in swine testes cell cultures. The only species in the genus is Swinepox virus.

Sunday Canyon virus (SCAV) An unas-signed virus in the family Bunyaviridae. Isolated from the tick, Argas cooleyi, collected in south-western USA in areas frequented by cliff swallows, Petrochelidon pyrrhonota. Sensitive to ether and to low pH. Pathogenic for suckling mice. Not reported to cause disease in humans.

Yunker CE et al (1977) Acta Virol, Prague 21, 36

supercoiled DNA A conformation that a double-stranded DNA molecule can adopt. When both strands of a double-stranded molecule are covalently closed, one of the strands becomes over- or under-wound in relation to the other. The torsional strain causes the molecule to coil into a characteristic shape.

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