PCR See polymerase chain reaction

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peacockpox virus (PKPV) A tentative species in the genus Avipoxvirus. Isolated from captive peacocks, Pavo cristatus sp, in Baghdad Zoo in 1978 during an outbreak in which there was 75% morbidity and 13% mortality. Pathogenic for chickens infected experimentally. Antigenically related to Fowlpox and Pigeonpox virus.

Al Fallugi MM et al (1979) J Wildl Dis 15, 597

Peaton virus (PEAV) A serotype of Shamonda virus in the genus Bunyavirus, belonging to the Simbu serogroup. Isolated from the mosquito, Culicoides bre-vitarsis, in Queensland, Australia.

St George TD et al (1980) Aust J Biol Sci 33, 235

PEG Abbreviation for polyethylene glycol. A chemical used for phase partitioning that is often employed to concentrate viruses present in a suspension.

pellet The material concentrated at the bottom of a centrifuge tube after centrifu-gation. See supernatant.

penciclovir A drug related to acyclovir which is selectively phosphorylated by the HSV thymidine kinase and inhibits replication of herpesviruses such as VZV and CMV as well as HSV. It is licensed as a cream for use against oral herpes. Because it was not effective orally, the 6-deoxydiacetyl ester derivative famciclovir was developed as an orally delivered prodrug of penciclovir and is now licensed for treatment, especially of herpes zoster infections in immunosup-pressed patients. It is also effective against hepatitis B.

Vere Hodge RA (1993) Antivir Chem Chemother 4, 67

penetration The second stage of infection of a cell by a virus. After attachment to a receptor area on the cell surface, the virus is taken into the cell either by fusion with the plasma membrane or by viropexis. The mechanism differs from one virus/cell system to another.

Lonberg-Holm K and Philipson L (1974) Monogr Virol 9,148 pp penguinpox virus (PEPV) A tentative species in the genus Avipoxvirus.

pentamers Protein units on the virion surface which in groups of five form pentons.

penton Group of five protein units at the 12 vertices of a virus capsid with icosahe-dral symmetry. In members of the Adenoviridae, the pentons are complex structures with base, fiber and knob, and are involved in cell attachment. See icosa-hedral symmetry.

Pependana virus A probable species in the genus Orbivirus, isolated from phle-botomine sandflies in the Amazon region of Brazil. Antigenically related to Changuinola virus. Not associated with disease in humans.

peplomers Knob-like structures (spikes) projecting from the surface envelope of a virus particle. They may have hemagglu-tinating activity and act as cell receptors, or have enzyme activity such as neur-aminidase. They are surface antigens.

peplos (Greek: peplos = an outer robe or cloak as worn by women in ancient Greece) Synonym for envelope.

peptabody A new type of high-avidity binding protein. A short peptide ligand was fused via a semi-rigid hinge region with the coiled-coil assembly domain of cartilage oligomeric matrix protein to produce a multivalent binding molecule.

Terskikh AV et al (1997) Proc Natl Acad Sci 94, 1663

peptide A compound of two or more amino acids joined by peptide bonds.

peptide bond A chemical link formed by the reaction between the carboxylic acid group of one amino acid and the amino group of another, thus uniting the carbon atom of one with the nitrogen atom of the other.

peptide vaccines Synthetic peptides were produced initially in 1963, and thought to have great promise as vaccines as the development of gene sequence analysis led to precise descriptions of the amino acid sequences of presumed antigenic binding sites (epitopes). Although clear evidence was obtained that protection against a major animal pathogen, foot and mouth disease virus, could be obtained by peptide immunization, albeit only at very high peptide doses in cattle, other efforts with human disease-inducing viruses have met with less success. Peptides are poorly immunogenic, do not necessarily adopt the same configuration as the natural epitope, and seem to give rise to binding but not neutralizing antibodies. A number of ways to improve the response have included coupling to pep-tide carrier molecules incorporating T-cell epitopes, but so far these remain at the stage of developmental research.

Meloen RH et al (1995) Vaccine 13, 885

peptidyl transferase An enzyme, part of the 50S subunit of the ribosome, which forms the peptide bonds between amino acids.

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