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正Dear Editor,Previous studies had described the adaptation of enterovirus 71 (EV-A71) strains that enabled entry and viral replication in Chinese Hamster Ovary (CHO) cell line(Zaini and Mc Minn 2012; Zaini et al. 2012). These adapted  相似文献   

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Chimeras between human (HM-175) and simian (AGM-27) strains of hepatitis A virus (HAV) were constructed to evaluate the effect of the 2C gene of AGM-27 on HAV replication in cell culture and virulence in tamarins (Saguinus mystax) and chimpanzees (Pan troglodytes). Kinetic studies and radioimmunofocus assays demonstrated that replacement of the 2C gene of HAV/7, a cell culture-adapted strain of HM-175, with that of AGM-27 drastically reduced the ability of the virus to replicate in cultured cells. Intragenic chimeras containing AGM-27 sequences in either the 5′ or 3′ half of the 2C gene replicated in cell culture at an intermediate level. Whereas HAV/7 is attenuated for tamarins, a chimera containing the simian virus 2C gene in the HAV/7 background was virulent in tamarins, demonstrating that the simian virus 2C gene alone can confer the phenotype of virulence to an otherwise attenuated virus. Clusters of AGM-27-specific residues near both ends of the 2C protein were required for virulence since a chimera containing AGM-27 sequences in the carboxy-terminal half of 2C was partially attenuated for tamarins while one containing AGM-27 sequences only in the amino-terminal half of 2C was even more attenuated. Chimeras containing either the entire or only the 3′ half of the simian virus 2C gene in the HAV/7 background were attenuated for chimpanzees.  相似文献   

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埃可病毒6型(Echovirus 6,ECHO6)作为肠道病毒B组(Enterovirus B,EV-B)的一员,在临床上常导致无菌性脑膜炎(Aseptic meningitis,AM)、急性弛缓性麻痹(Acute flaccid paralysis,AFP)、手足口病(Hand,foot,and mouth disease,HFMD)等多种疾病。本文挑选四株中国大陆地区不同年份、地区及疾病严重程度的代表毒株进行全基因组测定分析,与GenBank上ECHO6全长代表株及EV-B组原型株比对分析,了解其进化特征,并筛选BLAST结果的EV-B组流行株,探究我国流行的ECHO6与其他血清型的基因重组特征。结果提示,本研究四株ECHO6毒株在非结构蛋白区与EV-B其他血清型均发生重组,其中死亡病例标本重组模式更为复杂,可能与疾病严重程度有关。通过本研究分析,可进一步揭示ECHO6的遗传特征,为肠道病毒血清型研究提供基础数据,对了解其进化变异及临床致病力影响具有重要意义。  相似文献   

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A new species of Primulaceae, Primula undulifolia, is described from the hilly area of Hunan province in south-central China. Its morphology and distributional range suggest that it is allied to P. kwangtungensis, both adapted to subtropical climate, having contiguous distribution and similar habitat, growing on shady and moist cliffs. Petioles, scapes and pedicels of them are densely covered with rusty multicellular hairs, but the new species can be easily distinguished by its smaller flowers and narrowly oblong leaves with undulate margins. Molecular phylogenetic analysis based on four DNA markers (ITS, matK, trnL-F and rps16) confirmed the new species as an independent lineage and constitutes a main clade together with P. kwangtungensis, P. kweichouensis, P. wangii and P. hunanensis of Primula sect. Carolinella.  相似文献   

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Two phagotrophic euglenid strains (Strains Pac and Tam) were isolated from coastal locations in Taiwan. Ultrastructural characteristics of the strains included five pellicle strips joined at the posterior end. The strips were formed by major grooves with bifurcated edges. At the cell anterior, the feeding structure formed a lip. Underneath the lip was a comb composed of layers of microtubules. Farther back, two supporting rods tapered toward the posterior end, and a number of vanes with attached microtubules were present between the rods. The morphological characteristics agree with Ploeotia costata Strain CCAP 1265/1. However, the 18S rDNA sequences of Strains Pac/Tam lacked a group I intron and possessed three extra insertions of 116, 67, and 53 bp. Phylogenetic analysis indicated low sequence similarity between Strains Pac/Tam and CCAP 1265/1 (92%). The morphospecies P. costata apparently includes a substantial level of DNA sequence divergence, and likely represents multiple molecular species units.  相似文献   

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A cytopathogenic agent was isolated in monkey kidney (MK) cell cultures from the stool specimen of a 3-month-old Filipina hospitalized with lower respiratory disease. The agent was designated the Drilon strain. It was characterized as an enterovirus on the basis of electron microscopic morphology, nucleic acid type (RNA), resistance to ether and acid (pH 3.0) treatments, stabilization by molar MgCl2 against heat inactivation, and buoyant density in CsCl. The strain caused mild febrile illness in experimentally inoculated cynomolgus monkeys, but not in suckling mice. In addition to its effect in primary MK cells, the virus was cytopathogenic in primary and secondary human amnion or embryonic lung cell cultures and in WI-38 or HEp-2 cell lines, but not in primary bovine kidney, primary porcine kidney, primary embryonic mouse or primary embryonic chick cell cultures. The Drilon strain was not neutralized by reference antisera against the known enterovirus serotypes, and the antiserum prepared with the Drilon strain did not neutralize any of the recognized prototype enterovirus strains. Although the patient's sera were not available, antibodies against the Drilon strain were prevalent in normal Filipinos and Indonesians, but not in Japanese people. The Drilon strain fulfilled the criteria of human enterovirus and is considered a candidate for designation as a new type.  相似文献   

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Homologous recombination (HR) is critical for the repair of double strand breaks and broken replication forks. Although HR is mostly error free, inherent or environmental conditions that either suppress or induce HR cause genomic instability. Despite its importance in carcinogenesis, due to limitations in our ability to detect HR in vivo, little is known about HR in mammalian tissues. Here, we describe a mouse model in which a direct repeat HR substrate is targeted to the ubiquitously expressed Rosa26 locus. In the Rosa26 Direct Repeat-GFP (RaDR-GFP) mice, HR between two truncated EGFP expression cassettes can yield a fluorescent signal. In-house image analysis software provides a rapid method for quantifying recombination events within intact tissues, and the frequency of recombinant cells can be evaluated by flow cytometry. A comparison among 11 tissues shows that the frequency of recombinant cells varies by more than two orders of magnitude among tissues, wherein HR in the brain is the lowest. Additionally, de novo recombination events accumulate with age in the colon, showing that this mouse model can be used to study the impact of chronic exposures on genomic stability. Exposure to N-methyl-N-nitrosourea, an alkylating agent similar to the cancer chemotherapeutic temozolomide, shows that the colon, liver and pancreas are susceptible to DNA damage-induced HR. Finally, histological analysis of the underlying cell types reveals that pancreatic acinar cells and liver hepatocytes undergo HR and also that HR can be specifically detected in colonic somatic stem cells. Taken together, the RaDR-GFP mouse model provides new understanding of how tissue and age impact susceptibility to HR, and enables future studies of genetic, environmental and physiological factors that modulate HR in mammals.  相似文献   

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Despite the identification of severe acute respiratory syndrome-related coronavirus (SARSr-CoV) in Rhinolophus Chinese horseshoe bats (SARSr-Rh-BatCoV) in China, the evolutionary and possible recombination origin of SARSr-CoV remains undetermined. We carried out the first study to investigate the migration pattern and SARSr-Rh-BatCoV genome epidemiology in Chinese horseshoe bats during a 4-year period. Of 1,401 Chinese horseshoe bats from Hong Kong and Guangdong, China, that were sampled, SARSr-Rh-BatCoV was detected in alimentary specimens from 130 (9.3%) bats, with peak activity during spring. A tagging exercise of 511 bats showed migration distances from 1.86 to 17 km. Bats carrying SARSr-Rh-BatCoV appeared healthy, with viral clearance occurring between 2 weeks and 4 months. However, lower body weights were observed in bats positive for SARSr-Rh-BatCoV, but not Rh-BatCoV HKU2. Complete genome sequencing of 10 SARSr-Rh-BatCoV strains showed frequent recombination between different strains. Moreover, recombination was detected between SARSr-Rh-BatCoV Rp3 from Guangxi, China, and Rf1 from Hubei, China, in the possible generation of civet SARSr-CoV SZ3, with a breakpoint at the nsp16/spike region. Molecular clock analysis showed that SARSr-CoVs were newly emerged viruses with the time of the most recent common ancestor (tMRCA) at 1972, which diverged between civet and bat strains in 1995. The present data suggest that SARSr-Rh-BatCoV causes acute, self-limiting infection in horseshoe bats, which serve as a reservoir for recombination between strains from different geographical locations within reachable foraging range. Civet SARSr-CoV is likely a recombinant virus arising from SARSr-CoV strains closely related to SARSr-Rh-BatCoV Rp3 and Rf1. Such frequent recombination, coupled with rapid evolution especially in ORF7b/ORF8 region, in these animals may have accounted for the cross-species transmission and emergence of SARS.Coronaviruses can infect a wide variety of animals, causing respiratory, enteric, hepatic, and neurological diseases with different degrees of severity. On the basis of genotypic and serological characteristics, coronaviruses were classified into three distinct groups (2, 20, 54). Among coronaviruses that infect humans, human coronavirus 229E (HCoV-229E) and human coronavirus NL63 (HCoV-NL63) belong to group 1 coronaviruses and human coronavirus OC43 (HCoV-OC43), and human coronavirus HKU1 (HCoV-HKU1) belong to group 2 coronaviruses, whereas severe acute respiratory syndrome-related coronavirus (SARSr-CoV) has been classified as a group 2b coronavirus, distantly related to group 2a, and the recently discovered group 2c and 2d coronaviruses (6, 8, 10, 18, 31, 38, 43, 46, 49, 50). Recently, the Coronavirus Study Group of the International Committee for Taxonomy of Viruses has proposed renaming the traditional group 1, 2, and 3 coronaviruses Alphacoronavirus, Betacoronavirus, and Gammacoronavirus, respectively (http://talk.ictvonline.org/media/p/1230.aspx).Among all coronaviruses, SARSr-CoV has caused the most severe disease in humans, with over 700 fatalities since the SARS epidemic in 2003. Although the identification of SARSr-CoV in Himalayan palm civets and raccoon dogs in live animal markets in southern China suggested that wild animals could be the origin of SARS (11), the presence of the virus in only market or farmed civets, but not civets in the wild, and the rapid evolution of SARSr-CoV genomes in market civets suggested that these caged animals were only intermediate hosts (24, 39, 42, 52). Since bats are commonly found and served in wild animal markets and restaurants in Guangdong, China (47), we have previously carried out a study of bats from the region and identified a SARSr-CoV in Rhinolophus Chinese horseshoe bats (SARSr-Rh-BatCoV) (21). Similar viruses have also been found in three other species of horseshoe bats in mainland China (25), supporting the hypothesis that horseshoe bats are a reservoir of SARSr-CoV. Recently, viruses closely related to SARSr-Rh-BatCoV in China were also reported in Chaerophon bats from Africa, although only partial RNA-dependent RNA polymerase (RdRp) sequences were available (41). In addition, more than 10 previously unrecognized coronaviruses of huge diversity have since been identified in bats from China and other countries (1, 3, 5, 9, 22, 27, 32, 33, 40, 46, 51), suggesting that bats play an important role in the ecology and evolution of coronaviruses.As a result of the unique mechanism of viral replication, coronaviruses have a high frequency of recombination (20). Such a high recombination rate, coupled with the infidelity of the polymerases of RNA viruses, may allow them to adapt to new hosts and ecological niches (12, 48). Recombination in coronaviruses was first recognized between different strains of murine hepatitis virus (MHV) and subsequently in other coronaviruses, such as infectious bronchitis virus, between MHV and bovine coronavirus, and between feline coronavirus type I and canine coronavirus generating feline coronavirus type II (12, 16, 17, 23). Recently, by complete genome analysis of 22 strains of HCoV-HKU1, we have also documented for the first time that natural recombination events in a human coronavirus can give rise to three different genotypes (48).Although previous studies have attempted to study the possible evolutionary and recombination origin of SARSr-CoV, no definite conclusion can be made on whether the viruses from bats are the direct ancestor of SARSr-CoV in civets and humans, given the paucity of available strains and genome sequences. To better define the epidemiology and evolution of SARSr-Rh-BatCoV in China and their role as a recombination origin of SARSr-CoV in civets, we carried out a 4-year study on coronaviruses in Chinese horseshoe bats in Hong Kong and Guangdong Province of southern China. Bat tagging was also performed to study the migration pattern of bats and viral persistence. The complete genomes of 10 strains of SARSr-Rh-BatCoV obtained at different time were sequenced and compared to previously sequenced genomes. With the availability of this larger set of genome sequences for more accurate analysis, recombination and molecular clock analyses were performed to elucidate the evolutionary origin and time of interspecies transmission of SARSr-CoV.  相似文献   

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对肠道病毒71型(enterovirus 71,EV71)中国(深圳)分离株SHZH03进行了全基因组(未包括多聚腺苷尾)7406个碱基的核苷酸序列测定.结果表明,SHZH03株与其它肠道病毒71型毒株相比,在编码区没有核苷酸的缺失和插入,其5′UTR和3′UTR区的长度和序列有一定的差异.核苷酸同源性比较结果表明,在P1区SHZH03株与SHZH98株、中国台湾流行株(TW2086、TW2272)的同源性较高(分别为92.5%,90.1%和87.9%),与新加坡流行株SIN5666、SIN5865及标准株MS、BrCr的同源性则在81%左右,而与Coxsackievirus A16(Cox.A16)的同源性最低(63.6%).氨基酸同源性比较结果表明,在P1区SHZH03株与Cox. A16的同源性最低,但在P2和P3区SHZH03株与Cox.A16的同源性最高.P1区的遗传进化分析表明,SHZH03株和中国台湾1998年流行的EV71毒株的亲缘关系较近,属于同一型(genogroup),而与标准株BrCr和MS的亲缘关系较远.上述结果有助于肠道病毒71型的基础研究和中国对于EV71所致疾病的预防.  相似文献   

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Background/Objectives: Parasites of the subgenus Leishmania (Viannia) cause varying clinical symptoms ranging from cutaneous leishmaniases (CL) with single or few lesions, disseminated CL (DL) with multiple lesions to disfiguring forms of mucocutaneous leishmaniasis (MCL). In this population genetics study, 37 strains of L. (V.) guyanensis, 63 of L. (V.) braziliensis, four of L. (V.) shawi, six of L. (V.) lainsoni, seven of L. (V.) naiffi, one each of L. (V.) utingensis and L. (V.) lindenbergi, and one L. (V.) lainsoni/L. naiffi hybrid from different endemic foci in Brazil were examined for variation at 15 hyper-variable microsatellite markers. Methodology/Principal findings: The multilocus microsatellite profiles obtained for the 120 strains were analysed using both model- and distance-based methods. Significant genetic diversity was observed for all L. (Viannia) strains studied. The two cluster analysis approaches identified two principal genetic groups or populations, one consisting of strains of L. (V.) guyanensis from the Amazon region and the other of strains of L. (V.) braziliensis isolated along the Atlantic coast of Brazil. A third group comprised a heterogeneous assembly of species, including other strains of L. braziliensis isolated from the north of Brazil, which were extremely polymorphic. The latter strains seemed to be more closely related to those of L. (V.) shawi, L. (V.) naiffi, and L. (V.) lainsoni, also isolated in northern Brazilian foci. The MLMT approach identified an epidemic clone consisting of 13 strains of L. braziliensis from Minas Gerais, but evidence for recombination was obtained for the populations of L. (V.) braziliensis from the Atlantic coast and for L. (V.) guyanensis. Conclusions/Significance: Different levels of recombination versus clonality seem to occur within the subgenus L. (Viannia). Though clearly departing from panmixia, sporadic, but long-term sustained recombination might explain the tremendous genetic diversity and limited population structure found for such L. (Viannia) strains.  相似文献   

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This review discusses the current testing methodologies for COVID-19 diagnosis and explores next-generation sequencing (NGS) technology for the detection of SARS-CoV-2 and monitoring phylogenetic evolution in the current COVID-19 pandemic. The review addresses the development, fundamentals, assay quality control and bioinformatics processing of the NGS data. This article provides a comprehensive review of the obstacles and opportunities facing the application of NGS technologies for the diagnosis, surveillance, and study of SARS-CoV-2 and other infectious diseases. Further, we have contemplated the opportunities and challenges inherent in the adoption of NGS technology as a diagnostic test with real-world examples of its utility in the fight against COVID-19.  相似文献   

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Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of porcine reproductive and respiratory syndrome (PRRS), which can evolve continuously by random mutation or intragenic recombination. Here we report the complete genomic sequence of a PRRSV variant with nucleotide acid deletions and insertions in the nonstructural protein 2 (nsp2) gene and a possible recombination event between a modified live virus (MLV) vaccine strain and a prototype Chinese field strain.  相似文献   

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The epidemiology and molecular characteristics of human enterovirus B (HEV-B) associated with hand, foot and mouth disease (HFMD) outbreaks in China are not well known. In the present study, we tested 201 HEV isolates from 233 clinical specimens from patients with severe HFMD during 2010–2011 in Linyi, Shandong, China. Of the 201 isolates, 189 were fully typed and 18 corresponded to HEV-B species (six serotypes CVA9, CVB1, CVB4, Echo 6, Echo 25 and Echo 30) using sensitive semi-nested polymerase chain reaction analysis of VP1 gene sequences. Phylogenetic analysis based on the VP1 region showed that eight E30SD belonged to a novel sub-genogroup D2; E25SD belonged to a novel sub-genogroup D6; E6SD belonged to sub-lineage C6 and five CVB1SD belonged to subgroup 4C; and B4SD belonged sub-lineage D2. The full viral genomes of the CVB1SD, E6SD, E25SD and E30SD isolates were sequenced. Analysis of phylogenetic and similarity plots indicated that E25SD recombined with E25-HN-2, E30FDJS03 and E4AUS250 at noncontiguous P2A–P3D regions, while E30SD, E30FDJ03, E25-HN-2 and E9 DM had shared sequences in discrete regions of P2 and P3. Both E6SD and B1SD shared sequences with E1-HN, B4/GX/10, B5-HN, and A9-Alberta in contiguous regions of most of P2 and P3. Genetic algorithm recombination detection analysis further confirmed the existence of multiple potential recombination points. In conclusion, analysis of the complete genomes of E25SD, E30SD, CVB1SD and E6SD isolated from HFMD patients revealed that they formed novel subgenogroup. Given the prevalence and recombination of these viruses in outbreaks of HFMD, persistent surveillance of HFMD-associated HEV-B pathogens is required to predict potential emerging viruses and related disease outbreaks.  相似文献   

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A new species of Leptobrachella is described from Sichuan Province and Chongqing Municipality,China.Molecular phylogenetic analyses based on mitochondrial and nuclear gene sequences indicated that the new species is genetically divergent from its congeners.It could be identified from its congeners by a combination of followings characters:body size of male 29.1-34.1 mm(n=14),female 34.1-34.9 mm(n=4);dorsal skin rough with large tubercles in size of humeral glands,without conical spines;fringes o...  相似文献   

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Mutations in the REM1 gene of Saccharomyces cerevisiae confer a semidominant hyper-recombination and hypermutable phenotype upon mitotic cells ( GOLIN and ESPOSITO 1977). These effects have not been observed in meiosis. We have examined the interactions of rem1 mutations with rad6-1, rad50 -1, rad52-1 or spo11 -1 mutations in order to understand the basis of the rem1 hyper-rec phenotype. The rad mutations have pleiotropic phenotypes; spo11 is only defective in sporulation and meiosis. The RAD6, RAD50 and SPO11 genes are not required for spontaneous mitotic recombination; mutations in the RAD52 gene cause a general spontaneous mitotic Rec- phenotype. Mutations in RAD50 , RAD52 or SPO11 eliminate meiotic recombination, and mutations in RAD6 prevent spore formation. Evidence for the involvement of RAD6 in meiotic recombination is less clear. Mutations in all three RAD genes confer sensitivity to X rays; the RAD6 gene is also required for UV damage repair. To test whether any of these functions might be involved in the hyper-rec phenotype conferred by rem1 mutations, double mutants were constructed. Double mutants of rem1 spo11 were viable and demonstrated rem1 levels of mitotic recombination, suggesting that the normal meiotic recombination system is not involved in producing the rem1 phenotype. The rem1 rad6 double mutant was also viable and had rem1 levels of mitotic recombination. Neither rem1 rad50 nor rem1 rad52 double mutants were viable. This suggests that rem1 causes its hyper-rec phenotype because it creates lesions in the DNA that are repaired using a recombination-repair system involving RAD50 and RAD52.  相似文献   

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