Plating efficiency See efficiency of plating

Playas virus (PLAV) A serotype of Bunyamwera virus in the genus Bunyavirus. Isolated from mosquitoes, Aedes taeniorhynchus, in Ecuador. Not known to cause disease in humans.

pleconaril

pleconaril An antiviral compound that inhibits picornavirus replication and is active in mice by oral administration. Binds to the hydrophobic pocket of the virion capsid. Clinical trials against enterovirus and rhinovirus infections are underway.

pleurodynia See Bamble disease.

pleuronectid herpesvirus (PiHV-1) An unas-signed virus in the family Herpesviridae. First recognized in 1978 among young turbot, Scophthalmus maximus, in a fish farm in Scotland, but since then also recognized in Wales. The fish develop anorexia and lethargy and heavy mortality occurs. The only signs of infection are pathological changes in epithelial cells of the skin and gills where giant cells are seen containing herpesvirus-like particles. Virus isolation has not been reported. Synonyms: herpesvirus scophthalmus; turbot herpesvirus.

Buchanan JS and Madeley CR (1978) J Fish Dis 1, 283

Buchanan JS et al (1978) Vet Rec 102, 527

plus strand The RNA strand which acts as messenger RNA. See positive strand.

Plymouth virus A strain of 'classic' human calicivirus from a 16-month-old girl. Identified by genomic sequence analysis.

Liu BL et al (1995) Arch Virol 140, 1345

PML-2 virus See JC polyomavirus.

PMSF (phenyl methanesulfonyl fluoride, a-toluenesulfonyl fluoride) An inhibitor of proteases. Used in studies on viral proteins where proteolysis is to be avoided.

pneumonia virus of mice (PVM) See

Murine pneumonia virus.

pneumonia virus of rats This very common chronic pulmonary disease of old laboratory rats probably has no specific cause, but a multiple etiology in which mycoplasma play a part. The many descriptive names given to chronic lung disease in rats do not describe specific diseases but rather clinical findings. Disease starts as a silent pneumonia and progresses slowly, often with the formation of pus-filled cavities and fibro-sis. The nose and middle ears may be mainly involved. Pleuropneumonia-like organisms and bacteria, as well as mycoplasma, are regularly isolated. Synonyms: atypical pneumonia of rats; endemic pneumonia of rats; enzootic bronchiectasis of rats.

Brennan PC et al (1969) Lab Anim Care 19, 360 Nelson JB (1946) J Exp Med 84, 7, 15

Pneumovirinae A subfamily in the family

Paramyxoviridae with two genera, Pneumovirus and Metapneumovirus. Differ from members of the subfamily Paramyxovirinae in having 10 separate transcriptional units, extensive O-linked glycosylation of the G protein, a smaller nucleocapsid diameter and longer surface peplomers.

Pneumovirus A genus of the subfamily Pneumovirinae. Virions contain no neu-raminidase. Nucleocapsid about 14nm in diameter with a helical pitch of 7nm. The negative-strand RNA genome encodes 10 separate genes. The glycoprotein (G protein) has extensive O-linked glycosylation. Type species Human respiratory syncytial virus. Other species are Bovine respiratory syncytial virus and Murine pneumonia virus.

Kingsbury DW et al (1978) Intervirology 10, 137

pock assay Viruses which replicate on the CAM often produce local lesions called pocks, visible to the naked eye. Each one originates from a single infected cell, so a count of the pocks produced is a measure of the infective dose applied to the membrane. Analogous to a plaque assay.

Pogosta disease Name given to an outbreak of disease in Finland caused by a variant of Sindbis virus. A Finnish name for the disease usually called Karelian fever, caused by Ockelbo virus. See Ockelbo virus.

Poisson distribution An important statistical concept used in virology to model experimental infections and to estimate the multiplicity of infection. It provides a distribution of the number of randomly occurring events over a given period of time; times between successive events are

poly A polymerase exponential random variables. In an experimental virus infection, the fraction of cells (P) that actually receive any given number (k) of infectious virus particles at an average multiplicity of infection (m) is described by the Poisson equation as P(k) = (e-mmk)/k!

polarized epithelial cells The plasma membrane of epithelial cells is divided into two discrete domains with distinct protein and lipid compositions. Tight junctions serve to preserve these domains and prevent mixing between them. Several cell lines maintain the properties of epithelial cells in culture (polarized cells) and some viruses are found to bud asymmetrically from these cells, e.g. Vesicular stomatitis, and retroviruses are released from the basolateral domain, whereas influenza virus, paramyxovirus and respiratory syncytial virus bud from the apical domain.

Tucker SP and Compans RW (1993) Adv Virus Res 42, 187

pol gene One of the genes in the genome of the retroviruses. Codes for the reverse transcriptase of the virus: the poly-merase, hence the name.

Katz RA and Skalka AM (1994) Annu Rev Biochem 63, 133

polio-encephalomyelopathy of mice virus Synonym for Theiler's murine encephalomyelitis virus.

poliomyelitis virus type 4 A name used at one time for coxsackie virus A7.

Chumakov MP et al (1956) Probl Virol 1, 16

Poliovirus (PV) The type species of the genus Enterovirus. There are three serotypes: human poliovirus 1, human poliovirus 2 and human poliovirus 3 (PV-1 to -3). Causes poliomyelitis, a disease of great antiquity, and was one of the first viruses to be isolated, in 1909. Following infection the virus may multiply in mucosal surfaces, tonsils and Peyer's patches of the small intestine before spreading to more distant lymph nodes and through viremia to other sites including peripheral nerves and spinal cord. The outcome of the infection may be inapparent (90-95%); an abortive or minor illness (respiratory, gastrointestinal or influenza-like) from which the patient soon recovers (4-8%); non-paralytic poliomyelitis, with symptoms of back pain and muscle spasm from which the patient soon recovers (1-2%); or paralytic poliomyelitis where following a minor prodromal illness as above, the predominant feature is flaccid paralysis resulting from lower motor neuron damage. Poliomyelitis is termed spinal if the lower spine is involved or bulbar if the upper spine and brain stem are involved. About 10% of cases, especially of bulbar poliomyelitis, are fatal and paralysis remains significant or severe in 80% of cases, with about 10% of cases recovering with only minor paralysis. Poliomyelitis was uncommon until standards of hygiene improved in the twentieth century. Formerly it was a common infection and the presence of maternal antibody probably protected infants from neurological disease. Once maternal infection became uncommon, infants were exposed to poliovirus and infantile paralysis became a major problem in the Western world. Safe and effective polio vaccines were developed in the 1950s which have led to a major initiative by WHO to eradicate poliovirus globally by 2005. See human polioviruses.

poliovirus hominis See Poliovirus.

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