serotypes of Dengue virus in the genus Flavivirus which together with Kedougou virus form the dengue virus serogroup. Double diffusion tests reveal a common antigen and specific antigens. Type 1 occurs in South-East Asia from India to Japan and Hawaii, with temporary spread to Greece, South Africa and Australia. The virus is not endemic in Japan except for a transient outbreak in the 1940s. Type 2 occurs in South-East Asia, central America and the Caribbean. Types 3 and 4 occur in Thailand and the Philippines. Hemorrhagic fever with dengue shock syndrome probably results from infection with one type in persons immune to another. An antigen-antibody reaction occurs in the tissues and results in increased vascular permeability and leakage of plasma, but the molecular basis of the pathological process is not well understood. No vaccines are currently licensed, but considerable progress has been made toward the development of a tetravalent live attenuated vaccine. Control is presently limited to control of the principal vector species, Aedes aegypti.
Gubler DJ and Meltzer M (1999) Adv Virus Res 54,35
Monath TP (1994) Semin Virol 5, 133
Denhardt's solution A solution comprising 0.02% Ficoll, 0.02% polyvinyl pyrrolidone and 0.02% bovine serum albumin used in the preincubation of nitrocellulose and nylon filters. This treatment prevents non-specific binding in Northern and Southern blots.
Denhardt DT (1966) Biochem Biophys Res Commun 23, 641
dense virus particles The virions of Picornaviridae which band at a density of 1.44g/ml compared to 1.34g/ml at which standard particles band. Dense and standard virions are probably two configurations of the virion structure.
Rowlands DJ et al (1975) J Gen Virol 29, 223 Wiegers KJ et al (1977) J Gen Virol 34, 465
density-dependent inhibition Inhibition of cell division in tissue cultures due to the presence of neighboring cells, although other factors are involved. For example, if cell metabolism has rendered the medium acid, restoration of an alkaline pH will temporarily restore growth. Addition of serum or other growth factors may also have a similar effect. See contact inhibition.
density gradient A gradient of a solute in a solvent used to support macromolecules during their fractionation. Usually applied to the separation of macromolec-ular species by centrifugation in a supporting column of fluid whose density is lowest at the top of the tube, and increases toward the bottom where it is greatest. This technique is particularly useful for the fractionation of virus-associated macromolecules. See rate zonal centrifugation and isopycnic gradient centrifugation.
Densovirinae A subfamily of the family Parvoviridae comprised of parvoviruses infecting invertebrate (arthropod) species.
Densovirus A genus of the subfamily Densovirinae, family Parvoviridae, containing parvoviruses infecting arthropods, which replicate without a helper virus. The virions contain single-stranded DNA, 6kb in length, which is either a positive or a negative strand.
Siegl G et al (1985) Intervirology 23, 61
6-deoxyacyclovir An acyclic nucleoside analog that is absorbed orally and converted by xanthine oxidase to form acyclovir. Has been used to treat chronic hepatitis B infection as well as herpes zoster.
Peterslund NA et al (1987) J Antimicrob Chemother 20, 743
Weller IV et al (1986) J Hepatol 2, 5119
1-2'-deoxy-2'-F-P-arabinosylfuranosyl-5-iodocytosine A nucleoside analog which selectively inhibits replication of her-pesviruses.
Colacino JM and Lopez C (1985) Antimicrob Ag Chemother 28, 252
deoxycholate Abbreviation for sodium deoxycholate (C24H39O4Na) (mol. wt. 414.6), an anionic detergent.
1-deoxynojirimycin An alpha-glucosidase inhibitor with some antiviral activity against HIV.
deoxyribonuclease (DNase) A phosphodi-esterase enzyme which degrades DNA. There are two types: exonucleases which require a terminus for hydrolysis; and endonucleases which may act broadly or on specific base sequences (restriction endonucleases). Often refers to DNase I, an endonuclease which digests single-stranded and double-stranded DNA to give oligonucleotides terminating in a 5'-nucleotide, and is dependent upon the divalent cation, Mg2+, for activity. DNase I digests single-stranded and double-stranded DNA to give oligonucleotides terminating in a 3'-nucleotide.
deoxyribonucleic acid (DNA) A polymer of deoxyribonucleotides which is the primary genetic material of all cells. A very large molecule: mol. wt. 106-1010. Adenine (A), cytosine (C), guanine (G) and thymine (T) are the four bases characteristic of DNA. A and G are purines (with a double-ring structure), and C and T are pyrimidines (with only a single ring). However, in certain types of viral DNA other bases occur, e.g. in T2, T4 and T6 bacteriophages cytosine is replaced by 5-hydroxymethylcytosine. The nucleo-tides in DNA are joined by diester links in which one phosphoric acid molecule forms bonds between the 3' and 5' positions of consecutive nucleotides to form a chain called a 'polydeoxyribonu-cleotide'. The sequence of nucleotides in the chain is the primary structure of DNA. In double-stranded DNA, the adenine and thymine are present in equimolecular amounts, as are guanine and cytosine (see Chargaff's rule). The pairing between bases of the two chains is highly specific. Adenine is always hydrogen-bonded to thymine, and gua-nine to cytosine. Because of this specific base-pairing, the sequences of nucleo-tides along the two chains are complementary. The two strands are of opposite polarity, the 5' end of one chain being opposite the 3' end of the other, and they exist as a double helix. The two helices are usually right-handed (B-DNA) but more rarely DNA can adopt left-handed helical conformations (Z-DNA). In addition to the B and Z conformations, in certain conditions DNA may form single-stranded loops, hairpins or cruciform structures. These structural forms may play a role as recognition elements in DNA-protein interactions such as transcription. The exact conformation and number of residues per turn depends on the physical conditions. Both single- and double-stranded DNA molecules can exist as linear molecules, or circles, and may be coiled or supercoiled, and all these forms can be observed in the DNA genomes of various viruses. Single-stranded DNA molecules are rare in nature but are found to constitute the genome of viruses such as Circoviridae, Parvoviridae and bacteriophage OX174.
Watson JD and Crick FHC (1953) Nature 171, 737
deoxyriboviruses DNA-containing viruses.
deoxyuridine triphosphate nucleotidohy-drolase (dUTPase) A herpesvirus-specific enzyme which is non-essential for growth of virus in vitro.
Dependovirus A genus in the subfamily Parvovirinae, family Parvoviridae. The type species is Adeno-associated virus 2 (AAV-2). Mature virions contain either positive or negative single-stranded DNA, about 4.7 kb in size, and upon extraction the DNA readily forms double strands. Replication is dependent upon a helper virus, adenovirus or herpesvirus. In the absence of a helper virus, the AAV genome can be integrated into cellular DNA to establish a latent infection. Subsequent helper virus infection may activate the latent AAV. All six isolates of Adeno-associated virus share a common antigen. Transplacental transmission has been observed. Species affecting cattle, chicken, dog, horse, humans, monkey and sheep have been described.
Berns KI and Bohenzky RA (1987) Adv Virus Res 32, 485
Berns KI (1990) Microbiol Rev 54, 316
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