Hemorrhagic septicemia virus of fish

Synonym for Viral hemorrhagic septicemia virus.

Henderson-Paterson bodies An old name for the molluscum body produced in epidermal cells of patients infected with Molluscum contagiosum virus. An inclusion body.

Hendra virus (HeV)

Hendra virus (HeV) An unclassified species in the family Paramyxoviridae, related to Nipah virus but distinct from other paramyxoviruses by genetic analysis and extended host range. Formerly called equine morbillivirus, but now known to be a virus which primarily infects large fruit bats, Pteropus sp, and is not a morbillivirus. Caused a serious outbreak of acute respiratory disease in the Hendra stables, near Brisbane, Queensland, Australia in 1994 in which 14 horses and their trainer died. A sta-blehand was also infected and hospitalized, but survived. In 1995 a second human death, this time from encephalitis, occurred in Mackay, Queensland in a man who had helped in a post-mortem examination of two horses one year earlier. Experimentally, Hendra virus has produced disease in cats, guinea pigs and horses, but not in mice, rabbits, chickens or dogs. The incubation period in horses is 8-11 days. There is depression, loss of appetite, fever, labored respiration, followed by substantial nasal discharge, and death within 2 days after onset of symptoms. Lungs show hemorrhagic as well as pneumonia-like lesions. Sampling of 2000 horses in Queensland revealed no evidence of infection except in those related to the Hendra stables. Antibodies can be found in all four species of fruit-eating bats (flying foxes) of the genus Pteropus found in Queensland, and infectious virus was isolated from one pregnant fruit bat. In January 1999 a horse in Cairns, Queensland that had died of unknown causes was found on post-mortem to have been infected with Hendra virus. No other cases of infection in horses or humans have been reported. Sequence analysis of the negative single-stranded RNA genome of Hendra virus reveals an exceptionally large molecule (18 234 nucleotides), which has only limited homology with all other paramyxoviruses except Nipah virus. It is likely that Hendra and Nipah viruses represent a new genus of the Paramyxoviridae, which remains to be described in detail.

Gould A (1996) Virus Res 43,17 Hyatt AD and Selleck PW (1996) Virus Res 43, 1 Lin-Fa Wang et al (2000) J Virol 74, 9972 Murray PK et al (1995) Science 268, 94

Hepacivirus A genus in the family Flaviviridae which includes Hepatitis C and related viruses. Transmission between humans occurs primarily through exposure to blood or blood products carrying the virus. There is no known invertebrate vector. Virions are spherical, 50 nm in diameter, and contain a molecule of linear positive-sense single-stranded RNA about 9.6 kb long. The 5'-NCR is about 340 nt long and contains an internal ribosomal entry site. The virion proteins include a nucleocapsid protein C (p19) and two envelope proteins, E1 (gp31) and E2 (gp70). Two non-structural proteins, NS2 and NS3, are autocatalytically derived from a single precursor molecule by a Zn-dependent proteinase activity that is not found in the other flavivirus genera. The genome consists of a single large open reading frame (ORF) which encodes a polyprotein of about 3000 amino acids. The gene order is 5'-C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B-3'. At present Hepatitis C virus is the only species in the genus.

Hepadnaviridae A family consisting of DNA viruses which infect humans and a variety of other species including wood-chucks, squirrels, herons and ducks. The mammalian and avian species are in different genera, Orthohepadnavirus and Avihepadnavirus, because of differences in genome structure and pathogenesis. The virus infecting humans is composed of a spherical, enveloped particle (the Dane particle), 42nm in diameter, with no evident surface projections, but small spherical particles, 22nm in diameter (HBsAg particles), are also present in the plasma of carriers. The virus particle consists of a 27nm icosahedral nucleocapsid (the core particle) containing one major polypeptide species (mol. wt. 20K) surrounded by a detergent-sensitive envelope. The lipid-containing envelope contains the surface (S) antigen (HBsAg, Australia antigen) against which virus-neutralizing antibodies are directed. The envelope is composed of three major proteins: S (p24, gp27); M (p33, gp36); and L (p39, gp42). The 22nm surface antigen (HBsAg) particles consist largely of S proteins (226 amino acids), which can assemble in the absence of cores. The M proteins (281 amino acids) are composed of p24 with an additional 55 amino acids at the N-terminus containing the pre-S2 domain. The L proteins (400 amino acids) contain an additional 119 amino acids at the N-terminus, containing the pre-S1 domain. HBsAg cross-reacts between human, woodchuck and ground squirrel hepadnaviruses, but not with avian hepadnaviruses. The virion core contains a single polypeptide (p22) which has both the core antigen (HBcAg) and, in truncated form (p16), the soluble e antigen (HBeAg) specificities. The core also contains enzyme activities involved in replication: DNA polymerase, reverse transcriptase and protein kinase. The genome is a single molecule of non-covalently closed, circular DNA (3.0-3.3kb in different viruses) which is partially single-stranded and partially double-stranded. The long strand is termed negative and is complementary to viral mRNA. It encodes four open reading frames, the core, polymerase, envelope and X gene. The X gene encodes a transactivator protein and is absent from avian hepadnaviruses. The positive strand varies from 1.7 to 2.8kb in different molecules. The negative strand is not a closed circle but has a nick at a unique site, which differs between mammalian and avian hepadnaviruses; there is a polypeptide covalently attached to its 5' end which acts as the primer for DNA synthesis. The positive strand is primed by a short 19-base RNA molecule at its 5' end. Replication involves the generation of a closed-circular DNA molecule within the cell nucleus, and synthesis of a 3.4kb plus-strand RNA that serves as mRNA and also as template for synthesis of negative-strand DNA. The exact mechanisms of cell entry and exit are not currently known. Hepadnaviruses are highly host-specific, and suitable in vitro cell culture systems to study these events have not been found for mammalian viruses. Fetal duck liver hepatocytes support growth of avian viruses.

Kann M and Gerlich WH (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. 745 Mason WS and Seeger C (editors) (1991) Curr Top Microbiol Immun 168, 206 pp Nassal M (1996) Curr Top Microbiol Immun 214, 297

HEPA filter High efficiency particulate air filter, used in biological safety cabinets of Class II level and higher to provide clean input air for product (e.g. cell culture) protection as well as filtered exhaust air for environmental protection. In some cases used in series for added protection.

heparan sulfate A glycosaminoglycan constituent of membrane-associated proteoglycans. Found on cells of the lungs, arterial walls and many other cell surfaces. Related to heparin and containing the same disaccharide repeating units, but is less sulfated.

heparin A highly sulfated glycosamino-glycan that has anticoagulant activity; it inhibits the action of thrombin by activating antithrombin III and interfering with the blood-clotting cascade.

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