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@#Objective To develop and verify a plaque method for detection of infectious titer of tick-borne encephalitis virus(TBEV)strain(PHKT strain for short)adapted to primary hamster kidney(PHK)cells.Methods PHK cells were infected with TBEV,a primary mouse brain adaption strain,and passed consecutively for 12 passages.The titer of PHKT was detected by plaque method(Monolayer BHK-21 cells were infected with PHKT of various passages at different dilution ratios,and the plaque number was calculated by neutral red staining)and challenge titration in mouse brain(Mice were challenged with PHKT of various passages at different dilution ratios through brain cavity,0.03 mL for each,observed continuously for 14 days,and calculated for the median lethal dose(LD50)by Reed-Muench method)respectively,and the correlation between the results of two methods was analyzed.The developed plaque method for the detection of TBEV titer was verified for specificity,repeatability and intermediate precision.Results The plaque titer of PHKT virus was up to8.9 lgPFU/mL;The correlation between the results of plaque method and mouse brain challenge titration method was good(r = 0.92);The specificity of plaque method for detecting infectious titer of PHKT virus was good,and the coefficients of variation(CVs)of repeatability and intermediate precision were both less than 5%.Conclusion A plaque method for detecting infectious titer of PHKT virus was developed,which may be used as an alternative method for challenge titration in mouse brain.
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@#Objective To express and purify the E protein Domain Ⅲ(ED Ⅲ) of tick-borne encephalitis virus(TBEV) in tandem and prepare the corresponding polyclonal antibody.Methods The TBEV RNA was extracted by Trizol method,and then reversely transcribed into cDNA,which was used as template to amplify ED Ⅲ gene fragment by PCR.Two ED Ⅲ gene fragments were ligated into fusion gene by the hydrophobic flexible polypeptide(G_4S)_3 using overlapping PCR,which was then linked to prokaryotic expression vector pET-28a(+) to construct the recombinant expression plasmid pET-28a-2ED Ⅲ.After sequencing,pET-28a-2ED Ⅲ was transformed into E.coli BL21(DE3) competent cells,induced by IPTG and purified by Ni~(2+) affinity chromatography.Female New Zealand white rabbits were immunized with the renatured recombinant protein to prepare polyclonal antibody.The antibody titer was detected by indirect ELISA and the specificity was identified by Western blot.The homology of ED Ⅲ amino acid sequence between TBEV and other flaviviruses was analyzed by DNAMAN software.Results The recombinant plasmid pET-28a-2ED Ⅲ was identified by sequencing,and the amplified sequence contained two genes consistent with the E sequence of TBEV "Senzhang" strain(JQ650523.1) included on GenBank,indicating that the recombinant plasmid was constructed correctly.The recombinant 2ED Ⅲ protein was expressed mainly in the form of inclusion bodies,with a relative molecular mass of about 21 000 and a purity of 97.5%.The titer of rabbit anti-2ED Ⅲ serum polyclonal antibody was 1:10~7,which reacted specifically with TBEV whole virus.DNAMAN software alignment showed that the homology of ED Ⅲ amino acid sequences between TBEV and Japanese encephalitis virus(JEV),yellow fever virus(YFV) and Dengue virus(DENY) was 36.56%,9.28% and 30.77%,respectively.Conclusion The TBEV envelope ED Ⅲ tandem recombinant expression plasmid pET-28a-2ED Ⅲ was successfully constructed.The expressed recombinant 2ED Ⅲ protein had good reactivity and immunogenicity,and the prepared polyclonal antibody had high titer.
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OBJECTIVE@#Tick-borne encephalitis virus (TBEV) is an emerging pathogen in Europe and North Asia that causes tick-borne encephalitis (TBE). A simple, rapid method for detecting TBEV RNA is needed to control this disease.@*METHODS@#A reverse-transcription recombinase-aided amplification (RT-RAA) assay was developed. This assay can be completed in one closed tube at 39 °C within 30 minutes. The sensitivity and specificity of RT-RAA were validated using non-infectious synthetic RNA representing a fragment of the NS5 region of the wild-type (WT) TBEV genome and the Senzhang strain. Additionally, 10 batches of tick samples were used to evaluate the performance of the RT-RAA assay.@*RESULTS@#The analytical limit of detection of the assay was 20 copies per reaction of the TBEV synthetic transcript and 3 plaque-forming units (pfu) per reaction of TBEV titers. With the specific assay, no signal due to other arboviruses was observed. Of the 10 batches of tick samples obtained from the Changbai Mountains of China, three were TBEV-positive, which was consistent with the results of the quantitative real-time PCR assay.@*CONCLUSION@#A rapid, highly sensitive, specific, and easy-to-use method was developed for the detection of the TBEV Far-Eastern subtype.
Subject(s)
Encephalitis Viruses, Tick-Borne , Genetics , Nucleic Acid Amplification Techniques , RNA, ViralABSTRACT
@#In Mongolia, the incidence and fatality rates of tick-borne encephalitis (TBE) have been increasing. We aimed to identify the epidemiological and molecular characteristics of tick-borne encephalitis virus (TBEV) associated with fatal meningoencephalitis in Mongolia. We conducted a descriptive study of 14 fatal cases of TBE that occurred between 2008 and 2017 in Mongolia. Reverse transcription polymerase chain reaction (RT–PCR) was used to detect viral RNA in brain tissue. RT–PCR products from six patients who died from TBE between 2013 and 2017 were directly sequenced and analysed phylogenetically. Ticks collected from Selenge and Bulgan provinces were also tested for TBEV by RT–PCR. Between 2008 and 2017, there were 14 fatal TBE cases in hospitals in Mongolia. The 14 patients who died reported receiving tick bites in Bulgan or Selenge province; 71.4% of deaths resulted from tick bites in Bulgan province. The TBE case fatality rate was 28.6% for patients in Bulgan province and 2.7% for those in Selenge province. All of the fatalities were men; the median age was 45 ± 12.6 years. Tick bites occurred between April and June in forested areas. In 2013, a 388 base pair fragment of the envelope (E) gene was obtained from a hospitalized patient. The closest relatives of this virus are Far-Eastern TBEV isolates. The case fatality rate differed between two provinces where tick bites occurred. A higher number of TBE cases and the virulent Far-Eastern subtype occurred in patients in Bulgan province. This province should increase vaccination coverage, training, education and investigations.
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To investigate the genotype and the biological characteristics of Tick-borne encephalitis virus (TBEV) in Charles Hilary endemic foci in the China-Kazakhstan border area in Xinjiang,ticks were collected by flagging during May to June in 2012 and 2014,and were stored in liquid nitrogen.TBEV strains were isolated from tick samples by inoculating BALB/c mice and BHK-21 cells.The FE gene fragments of TBEV-Far and the S gene fragments of TBEV-Sib were detected by RT-PCR from infected mice brain tissue and BHK cells,and then subjected to sequence alignment.Totally 16 TBEV strains were isolated from Ixodes persulcatus and Dermuceuter silvarum,among 13 strains were Far eastern subtype,three strains were Siberian subtype.It was first time that the TBEV-Sib was isolated in China.The Charles Hilary TBE natural foci were in the China-Kazakhstan border area,and both TBEV-Far and TBEV-Sib co-circulated.
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Tick-borne encephalitis ( TBE) is a well-known central nervous system ( CNS) infection in children. The disease in children is generally milder,although severe illness may occur and even lead to perma-nent impairment of the quality of life due to neuropsychological sequelae. We review the epidemiological and clinical characteristics of tick-borne encephalitis,and summarise biological and virological aspects that are impor-tant for understanding the life-cycle and transmission of the virus. Tick-borne encephalitis virus is a flavivirus that is transmitted by ixodes persulcatus. Tick-borne encephalitis causes acute meningoencephalitis. The serologi-cal diagnosis is usually straightforward. No specific treatment for the disease exists,and immunisation is the main preventive measure.
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Tickborne encephalitis (TBE) is a human viral infectious disease caused by tickborne encephalitis virus (TBEV). It is transmitted by the bite of an infected tick and also initiated the swelling of brain (encephalitis) and spinal cord. There is a pressing need to develop potent and sufficient amount of drugs and vaccines for control of TBE. We have selected the structural proteins such as anchored core protein C, core protein C, premembrane, matrix and envelope proteins of TBEV for identification of T-cell epitopes using immunoinformatics tools. These epitopes were showed the highest binding affinity with major histocompatibility complex (MHC) class I and II molecules. These finding may be used as an immunodiagnostic agent and also development of peptide based novel vaccines.
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Objective To identify the infection and the replication of Tick-borne encephalitis virus(TBEV) in human neuroblastoma cells.Methods After being inffected with TBEV,the cell culture supernatant of human neuroblastoma cell line SK-N-SH was collected and assayed at different time points.Byusing real-time RT-PCR and plaque assay to measure the titer of virus in the supernatant,the replication andproliferation of TBEV in human neuroblastoma cell was identified.Meanwhile,the morphological change of SK-N-SH after TBEV infection was also visualized by observation under microscope and immunmquorescenceassay.Results Real-time RT-PCR and plaque assay both demonstrated that TBEV could replicate effectively in SK-N-SH cells,the peak titer could reach 2.92× 107 PFU/ml on 3 days post-inoculation.And significant morphological change occured on infected SK-N-SH cells after 2 days post inoculation.By immunofluorescence assay,the virus particles could be detected and visualized.Conclusion TBEV can replicate andproliferate effcctively and cause significant cell morphological changes in human neuroblastoma cell SK-N-SH,which demonstrated that SK-N-SH could be a suitable cell model for TBEV culture.
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The prevalence of tick-borne encephalitis virus (TBEV) in southern Korea was determined by collecting ticks using tick drags. A total of 4,077 of 6,788 ticks collected were pooled (649 pools) according to collection site, species, and developmental stage and assayed for TBEV. The TBEV protein E and NS5 gene fragments were detected using RT-nested PCR in six pools of nymphs collected from Jeju Island (2,491 ticks). The minimum field detection rates for TBEV were 0.17% and 0.14% for Haemaphysalis longicornis and Haemayphysalis. flava nymphs, respectively. The 252 bp NS5 and 477 bp protein E gene amplicons were sequenced. Phylogenetic analysis showed that the NS5 and protein E genes of the Jeju strain were clustered with Western subtype (98.0% and 99.4% identity, respectively). The Western subtype of TBEV is endemic in Korea, including Jeju Island. The study of vector and zoonotic host susceptibility to TBEV is required to better understand its potential impact on public health.