Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bluetongue (BT) is an arthropod-borne viral disease affecting ruminants primarily in tropical and temperate regions of the world. Of the 24 serotypes of BT virus (BTV) identified worldwide, five have been found in the United States. Serotype identification of BTV isolates is important to the epidemiology of the virus, but current methods are cumbersome. A single-tube multiplex reverse transcriptase polymerase chain reaction (mRT-PCR) assay, previously developed for the serotype determination of U.S. BTV isolates, was evaluated. The determination of serotype was based on the size of the resultant amplified product. The procedure was evaluated using all 24 serotypes of BTV and nine serotypes of epizootic hemorrhagic disease virus (EHDV), a closely related orbivirus. Only the five U.S. serotypes of BTV were detected by the mRT-PCR. The assay was further tested using 132 BTV isolates originating from 24 western and southern states of the United States, from several different host species, spanning a period of 24 years. The serotypes of the isolates were determined by both a virus neutralization (VN) procedure and the mRT-PCR. Comparison of the mRT-PCR to the standard VN showed that the mRT-PCR successfully identified the serotypes of 130 of the isolates and was shown to be more reliable and specific than the VN assay.
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PMID:Validation of a reverse transcriptase multiplex PCR test for the serotype determination of U.S. isolates of bluetongue virus. 1094 41

Bluetongue virus (BTV) is the cause of an insect-transmitted virus infection of ruminants that occurs throughout much of the world. Individual gene segments differ between field strains of BTV; thus, we hypothesized that key viral genes undergo genetic drift during alternating passage of BTV in its ruminant and insect hosts. To test this hypothesis, variation in the consensus sequence and quasispecies heterogeneity of the VP2 and NS3/NS3A genes of a plaque-purified strain of BTV serotype 10 was determined during alternating infection of vector Culicoides sonorensis and a sheep and calf. Consensus sequences were determined after reverse transcriptase-nested PCR amplification of viral RNA directly from ruminant blood and homogenized insects, and quasispecies heterogeneity was determined by the sequencing of clones derived from directly amplified viral RNA. Comparison of these sequences to those of the original BTV inoculum used to initiate the cycle of BTV infection demonstrated, for the first time, that individual BTV gene segments evolve independently of one another by genetic drift in a host-specific fashion, generating quasispecies populations in both ruminant and insect hosts. Furthermore, a unique viral variant was randomly ingested by C. sonorensis insects that fed on a sheep with low-titer viremia, thereby fixing a novel genotype by founder effect. Thus, we conclude that genetic drift and founder effect contribute to diversification of individual gene segments of field strains of BTV.
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PMID:Occurrence of genetic drift and founder effect during quasispecies evolution of the VP2 and NS3/NS3A genes of bluetongue virus upon passage between sheep, cattle, and Culicoides sonorensis. 1148 75

Bluetongue virus (BTV) is the causative agent of Bluetongue (BT) disease in ruminant livestock and occurs almost worldwide between latitudes 35 degrees S and 50 degrees N; 24 serotypes of BTV are known of which 8 circulate periodically within parts of the Mediterranean Region. A fast (about 3.5 h) and versatile diagnostic procedure able to detect and quantify BTV-RNA, has been developed using a Molecular Beacon (MB) fluorescent probe; PCR primers were designed to target 91 bp within the NS3 conserved region of the viral RNA segment 10 (S10) and bracketed the MB fluorescence probe hybridisation site. The MB fluorescent probe was used to develop two Bluetongue serogroup-specific assays: a quantitative real time reverse transcriptase polymerase chain reaction (RT-PCR) and a traditional RT-PCR. These were tested using BTV-RNAs extracted from the blood and organs of BT-affected animals, and from virus isolate suspensions. The samples included ten serotypes (BTV-1-BTV-9 and BTV-16); of these, BTV serotypes -1, -2, -4, -9 and -16 have since 1998 been involved in the extensive outbreaks of BT across the Mediterranean Region. To evaluate the specificity and sensitivity of the MB probe, all positive samples (and negative controls) were tested using the developed quantitative real time RT-PCR and traditional RT-PCR assays. The former test had a detection limit of 10(3) cDNA molecules per reaction with a log-linear quantification range of up to 10(11) (R2 = 0.98), while the latter test was able to detect 500 cDNA-BTV molecules/PCR. The results show that the MB fluorescent probe is both rapid and versatile for the laboratory diagnosis of Bluetongue and for quantifying levels of viraemia in BTV-affected animals. An "in silico" comparison of the primers and MB fluorescent probe used in this study showed that it is possible to detect all 24 serotypes of BTV.
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PMID:Rapid detection and quantitation of Bluetongue virus (BTV) using a Molecular Beacon fluorescent probe assay. 1687 84

Bluetongue virus (BTV) is the prototype of the member of the Orbivirus genus within the family Reoviridae. The BTV serogroup contains 24 serotypes. Traditionally, viruses have been isolated in cultured cells, suckling mouse brain or embryonated chicken eggs before their identification and biochemical, antigenic and biological characterization. These procedures are time-consuming and may fail to detect low levels of infectious virus or strains of BTV which fail to replicate in eggs, mice or tissue culture. In the past decade, traditional procedures for virus characterization, such as ELISA and serum neutralisation with serotype-specific antisera, have been supplemented by reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing. A number of procedures have been developed to detect the presence of BTV antigens or nucleic acids. RT-PCR technique has appeared to be a powerful tool in the field of BTV diagnosis. Polymerase chain reaction techniques may be used not only to detect the presence of viral nucleic acid but also to 'serogroup' orbiviruses and provide information on the serotype and possible geographical source (topotype or genotype) of BTV isolates within a few days of receipt of a clinical sample such as infected sheep blood. Real-time PCRs have recently been developed.
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PMID:Bluetongue: characterization of virus types by reverse transcription-polymerase chain reaction. 1705 94

In August 2006, Bluetongue virus disease (BTD) was detected for the first time in the Netherlands, Belgium, Germany and Northern France. Serological tests as well as reverse transcriptase polymerase chain reaction (RT-PCR) proved the occurrence of Bluetongue virus (BTV) in diseased sheep and cattle, and the virus was identified as serotype 8. Therefore, the search for possible vectors was immediately initiated in the outbreak region in Germany. Traps with automatically regulated ultraviolet light lamps were placed at two different farms with sero-positive cattle, and insect monitoring was done from August 2006 until January 2007. The caught arthropods were weekly determined, and it could be observed that midges of the dipteran family Ceratopogonidae occurred in large numbers, sometimes representing up to 40% of all individuals. The microscopical analysis of the wing morphology showed that the species (complex) Culicoides obsoletus was most abundant covering about 97% of the analysed midges. On the second place ranged C. pulicaris, while C. nubeculosus and C. festivipennis were found only as single individuals. Fed and unfed females were separated, sent to the National Reference Laboratory for Bluetongue disease (Friedrich-Loeffler-Institut, Isle of Riems, Germany) and investigated with a BTV-8-specific real-time RT-PCR. It could be demonstrated that at both farms both fed and unfed C. obsoletus were tested positive for BTV-8 genomes, while none of the other species scored positive. This finding strongly supports that the BTD-epidemic, which reached in the meantime wide regions of North Rhine-Westphalia in Germany and of the neighbouring countries with several hundreds of affected farms, is initiated by virus transmission during the blood meal of midges of the C. obsoletus complex. Since they were captured still at the 21st of December close to cattle with clinical signs, it must be feared that BTV-8 is now established in Central Europe, where it had been absent until now.
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PMID:First occurrence of Culicoides obsoletus-transmitted Bluetongue virus epidemic in Central Europe. 1738 85

When the first outbreak of bluetongue virus serotype 8 (BTV8) was recorded in North-West Europe in August 2006 and renewed outbreaks occurred in the summer of 2007 and again in 2008, the question was raised how the virus survived the winter. Since most adult Culicoides vector midges are assumed not to survive the northern European winter, and transovarial transmission in Culicoides is not recorded, we examined the potential vector role of ixodid and argasid ticks for bluetongue virus. Four species of ixodid ticks (Ixodes ricinus, Ixodes hexagonus, Dermacentor reticulatus and Rhipicephalus bursa) and one soft tick species, Ornithodoros savignyi, ingested BTV8-containing blood either through capillary feeding or by feeding on artificial membranes. The virus was taken up by the ticks and was found to pass through the gut barrier and spread via the haemolymph into the salivary glands, ovaries and testes, as demonstrated by real-time reverse transcriptase PCR (PCR-test). BTV8 was detected in various tissues of ixodid ticks for up to 21 days post feeding and in Ornithodoros ticks for up to 26 days. It was found after moulting in adult Ixodes hexagonus and was also able to pass through the ovaries into the eggs of an Ornithodoros savignyi tick. This study demonstrates that ticks can become infected with bluetongue virus serotype 8. The transstadial passage in hard ticks and transovarial passage in soft ticks suggest that ticks have potential vectorial capacity for bluetongue virus. Further studies are required to investigate transmission from infected ticks to domestic livestock. This route of transmission could provide an additional clue in the unresolved mystery of the epidemiology of Bluetongue in Europe by considering ticks as a potential overwintering mechanism for bluetongue virus.
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PMID:Potential role of ticks as vectors of bluetongue virus. 2035 93

Bluetongue (BT) first occurred in Japan between late August and October 1994 in 23 cattle in three prefectures of the northern Kanto region, and between the end of October and mid-November in 23 Suffolk sheep in the same region. The affected cattle had fever, deglutitive difficulty, hyper-salivation, facial oedema, scabbing of the corner of the mouth and dysphagia. The BT virus (BTV) was isolated from blood cells of the affected sheep. Surveillance for BTV antibody conducted by prefectures in the affected region has detected seroconversion to BTV in some prefectures every year thereafter. In the autumn of 2001, again in the northern Kanto region, 45 sheep developed BT, and BTV was isolated. It is considered important that Japan has imported numerous cattle from Australia, the United States of America (USA), and New Zealand every year. In particular, BTV was isolated from cattle imported from the USA during quarantine although some of the serotypes isolated are not present in the USA. Furthermore, BTV is not present in New Zealand. The third RNA segment encoding the serogroup-specific VP3 protein of Japanese BTV isolates and reverse transcriptase-polymerase chain reaction (RT-PCR) positive blood cells was amplified by RT-PCR. Molecular phylogenetic analysis of the third RNA segment based on the sequence homology of the PCR products led to the classification of Japanese BTV isolates into two major groups.
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PMID:Epidemiological observations on bluetongue in sheep and cattle in Japan. 2041 39

Bluetongue virus (BTV) has persisted within Europe for the past five years, highlighting a need for rapid and reliable virus detection and identification methods. Various RT-PCR protocols and strategies, which target genome segment 7, were evaluated for their ability to detect all members of the BTV species (serogroup), with the aim of developing a fully validated reverse transcriptase-polymerase chain reaction- (RT-PCR) based diagnostic assay. A nested PCR strategy, using near terminal and internal segment 7 primers, detected all 24 BTV serotypes, but also cross-reacted with some other related Orbivirus species. In an attempt to circumvent these problems, conventional PCR and touch-down PCR methods, using similar primers were also investigated. Both methods were able to amplify cDNA from only 21 of the 24 BTV types. Further sequence analyses of the VP7 gene from the remaining isolates (types 7, 15 and 19) will permit the design of additional and more effective virus-species specific primers and RT-PCR-based assays. This may include the introduction of a multiplex PCR system.
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PMID:Differential diagnosis of bluetongue virus using a reverse transcriptase-polymerase chain reaction for genome segment 7. 2042 84

Bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) in deer have already been isolated in Reunion Island and have caused more or less severe clinical signs in cattle (EHDV) or in sheep (BTV), as observed in 2003. In January 2009, cattle in Reunion Island showed clinical signs suggesting infection by one or the other of these arboviral diseases. A study was set up to determine the etiology of the disease. Analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) performed on blood samples from 116 cattle from different districts of the island detected the presence of the EHDV genome in 106 samples and, in 5 of them, the simultaneous occurrence of BTV and EHDV. One strain of EHDV (7 isolates) and one of BTV were isolated in embryonated eggs and a BHK-21 cell culture. Group and subgroup primer-pairs were designed on the segment 2 sequences available in GenBank to identify and type the EHDV strains. Phylogenetic analysis of the genomic segment 2 (encoding the VP2 serotype-specific protein) of the isolates confirmed the serotypes of these two orbiviruses as BTV-2 and EHDV-6 and allowed them to be compared with previously isolated strains.
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PMID:Co-circulation of bluetongue and epizootic haemorrhagic disease viruses in cattle in Reunion Island. 2200 78

Bluetongue (BT) is an insect-transmitted, economically important disease of domestic and wild ruminants. Although only five of the 26 reported bluetongue virus (BTV) serotypes are considered endemic to the USA, 10 exotic serotypes have been isolated primarily in the southeastern region of the country since 1999. For an exotic BTV serotype to become endemic there must be susceptible animal species and competent vectors. In the USA, sheep and white-tailed deer (WTD) are the primary sentinel livestock and wildlife species, respectively. In 2006, BTV-8 was introduced into Northern Europe and subsequently overwintered, causing unprecedented livestock disease and mortality during the 2006-2007 vector seasons. To assess the risk of the European strain of BTV-8 to North American WTD, and understand the role they could play after a similar introduction, eight bluetongue-seronegative WTD were inoculated with BTV-8. Body temperatures and clinical signs were recorded daily. Blood samples were analyzed for BTV RNA with quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR), serum analyzed for BTV antibodies by cELISA, and tissues taken for histopathology and qRT-PCR. All eight deer became infected and developed moderate to severe clinical disease from days 8 to 15. Peak viremia was from day 7 to 10 with detectable titers through the end of the study (28 days) in most deer. Serum antibody was detected by day 6, peaked by day 10 and continued through day 28. We conclude that North American WTD are highly susceptible to BTV-8 and would act as clinical disease sentinels and amplifying hosts during an outbreak.
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PMID:Experimental infection of white-tailed deer (Odocoileus virginianus) with Northern European bluetongue virus serotype 8. 2387 32


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