Next-generation Sequencing Study of Pathogens in Serum from Patients with Febrile Jaundice in Sierra Leone / 生物医学与环境科学（英文）

OBJECTIVE@#People in Western Africa suffer greatly from febrile jaundice, which is caused by a variety of pathogens. However, yellow fever virus (YFV) is the only pathogen under surveillance in Sierra Leone owing to the undeveloped medical and public health system there. Most of the results of YFV identification are negative. Elucidation of the pathogen spectrum is required to reduce the prevalence of febrile jaundice.@*METHODS@#In the present study, we used Ion Torrent semiconductor sequencing to profile the pathogen spectrum in archived YFV-negative sera from 96 patients in Sierra Leone who presented with unexplained febrile jaundice.@*RESULTS@#The most frequently identified sequencing reads belonged to the following pathogens: cytomegalovirus (89.58%), Epstein-Barr virus (55.21%), hepatitis C virus (34.38%), rhinovirus (28.13%), hepatitis A virus (20.83%), coxsackievirus (10.42%), Ebola virus (8.33%), hepatitis E virus (8.33%), lyssavirus (4.17%), leptospirosis (4.17%), chikungunya virus (2.08%), Crimean-Congo hemorrhagic fever virus (1.04%), and hepatitis B virus (1.04%).@*CONCLUSION@#The distribution of sequencing reads suggests a broader spectrum of pathogens for consideration in clinical diagnostics and epidemiological surveillance in Sierra Leone.

Study on serological cross-reactivity of six pathogenic phleboviruses / 病毒学报

This article aimed to study the antigenicity of nucleocapsid proteins (NPs) in six pathogenic phleboviruses and to provide theoretical evidence for the development of serological diagnostic reagents. NPs of six pathogenic phleboviruses were expressed and purified using a prokaryotic expression system and rabbits were immunized with individual recombinant NPs. Cross-reactions among NPs and rabbit sera were determined by both indirect ELISA and Western blotting analyses, and the sera titer was determined by indirect ELISA. Furthermore, sera from SFTS patients were also detected by each recombinant NP as a coating antigen using indirect ELISA. The cross-reactions and the sera titer were subsequently determined. Both the concentration and purity of recombinant NPs of six pathogenic phleboviruses met the standards for immunization and detection. The results of indirect ELISA and Western blotting showed that each anti-phlebovirus NP rabbit immune serum had potential serological cross-reactivity with the other five virus NP antigens. Furthermore, the sera from SFTS patients also had cross-reactivity with the other five NP antigens to a certain extent. Our preliminary study evaluated the antigenicity and immune reactivity of six pathogenic phleboviruses NPs and laid the foundation for the development of diagnostic reagents.

Virus-like particle-based immunoglobulin M capture enzyme-linked immunosorbent assay for the detection of IgM antibodies against Chikungunya virus / 病毒学报

To establish a MacELISA method for the detection of IgM antibodies against Chikungunya virus (CHIKV), we prepared virus like particle (VLP) antigens of CHIKV using the whole structural protein C-E3-E2-6K-E1 encoding gene with a baculovirus expression system in Sf9 insect cells. The VLPs were purified and used to immunize Kunming mice. Then, polyclonal antibodies were purified from the samples of ascites with a protein G HiTrap SP column and labeled with horseradish peroxidase. A MacELISA method for the detection of IgM antibodies against CHIKV was assembled with goat anti-human IgM antibody, VLP antigens and an enzyme-labeled polyclonal antibody. The results were evaluated with a serum panel containing serum samples from laboratory-confirmed CHIK, HFRS patients, healthy donors, and commercially available CHIKV IgM as a quality control. It was shown that the MacELISA had a specificity of 99% (99/100), the coefficients of variation (CoV) within a plate were <10%, and the CoV of different ELISA plates in terms of the plate variation coefficient was <15%. A comparative analysis was performed to compare the current method against a commercial CHIKV IgM antibody detection kit for IIFA-IgM. The detection limit of MacELISA was significantly lower than that of the IIFA-IgM commercial kit (P< 0.0001). Here, we demonstrate that the VLP-based MacELISA is a promising tool for the early diagnosis and epidemiological investigation of CHIKV infection, with a high level of sensitivity and specificity for the detection of IgM antibodies against CHIKV.

Study on adjuvant effect of oral recombinant subunit vaccine formulated with chitosan against human enterovirus 71 / 病毒学报

To evaluate the adjuvant effect of recombinant enterovirus 71 (EV71) subunit vaccine formulated with chitosan, rabbits were orally immunized with recombinant VP1 (rVP1) or rVP1 mixed with chitosan adjuvant. Levels of virus-specific IgG and IgA antibodies in sera, mucosal wash buffer (intestine, nasal cavity, and lung), and feces were determined by indirect enzyme-linked immunosorbent assay (ELISA). The titers of neutralizing antibodies against EV71 were determined using cytopathic effect-based neutralizing assay, and levels of cytokines (IFN-gamma and IL-4) secreted from in vitro-cultured rabbit splenic lymphocytes under antigen stimulation were also determined by ELISA. Results showed that immunization with rVP1 alone could only induce low levels of serum IgG and mucosal IgA, while rVP1 combined with chitosan adjuvant were able to induce significantly higher levels of antibodies, rVP1 can only induce neutralizing antibodies when used in combination with chitosan. Levels of IFN-gamma and IL-4 in the group immunized with rVP1 plus chitosan were significantly higher than those in the group immunized with rVP1 only or those in the control groups. Our study lays the foundation for development of oral VP1 vaccine against EV71 infection.

Severe fever with thrombocytopenia syndrome virus nucleoprotein specifically binds to 60kD SSA/Ro protein in host cells / 病毒学报

This study aims to investigate whether the nucleoprotein (NP) of severe fever with thrombocytopenia syndrome virus (SFTSV) can impact the cellular immunity of host cells. Gene segments that encode the NP and non-structural protein (NSs) of SFTSV were inserted into eukaryotic expression vector VR1012. Host proteins that interact with NP and affect immunity were identified with co-immunoprecipitation (IP), SDS-PAGE, mass spectrometry (MS), and Western blot. Co-localization of NP and the identified host proteins was confirmed by confocal microscopy. A 60kD SSA/Ro, a protein related to immunity, interacted with NP, as found by IP and MS. Confocal microscopy showed that NP and SSA/Ro were co-localized in cytoplasm. These results indicated that SFTSV NP may specifically bind to 60kD SSA/Ro and cause a series of immune responses and clinical symptoms.

Investigation of RNA viral genome amplification by multiple displacement amplification technique / 病毒学报

In order to facilitate the detection of newly emerging or rare viral infectious diseases, a negative-strand RNA virus-severe fever with thrombocytopenia syndrome bunyavirus, and a positive-strand RNA virus-dengue virus, were used to investigate RNA viral genome unspecific amplification by multiple displacement amplification technique from clinical samples. Series of 10-fold diluted purified viral RNA were utilized as analog samples with different pathogen loads, after a series of reactions were sequentially processed, single-strand cDNA, double-strand cDNA, double-strand cDNA treated with ligation without or with supplemental RNA were generated, then a Phi29 DNA polymerase depended isothermal amplification was employed, and finally the target gene copies were detected by real time PCR assays to evaluate the amplification efficiencies of various methods. The results showed that multiple displacement amplification effects of single-strand or double-strand cDNA templates were limited, while the fold increases of double-strand cDNA templates treated with ligation could be up to 6 X 10(3), even 2 X 10(5) when supplemental RNA existed, and better results were obtained when viral RNA loads were lower. A RNA viral genome amplification system using multiple displacement amplification technique was established in this study and effective amplification of RNA viral genome with low load was achieved, which could provide a tool to synthesize adequate viral genome for multiplex pathogens detection.

Subcellular localization of severe fever with thrombocytopenia syndrome virus in macrophages / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To study the subcellular localization of severe fever with thrombocytopenia syndrome virus (SFTSV) in macrophages and understand the replication and assembly mechanism of SFTSV in host cells.</p><p><b>METHODS</b>Using two types of human macrophage cell lines THP-1 and U937, the study analyzed the intracellular colocalization of SFTSV with Golgi apparatus and endoplasmic reticulum by immunefluorescence staining and confocal microscopy.</p><p><b>RESULTS</b>SFTSV infected macrophage cell lines THP-1 and U937. Immunofluorescence staining showed that the SFTSV nuclear protein colocalized with Golgi apparatus and closely surrounded by endoplasmic reticulum in the perinuclear region.</p><p><b>CONCLUSION</b>The results suggested that Golgi complex and endoplasmic reticulum are probably the sites for formation and maturation of SFTSV viral particles.</p>

A double antibody sandwich ELISA based assay for titration of severe fever with thrombocytopenia syndrome virus / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To develop an assay for titration of severe fever with thrombocytopenia syndrome virus (SFTSV) based on double antibody sandwich ELISA.</p><p><b>METHODS</b>A double antibody sandwich ELISA was developed for detection of SFTSV based on SFTSV nucleocapsid (N) protein specific poly- and monoclonal antibodies, procedures were optimized and evaluated. This ELISA based titration assay was compared with fluorescence assasy and plaque assay based titration method.</p><p><b>RESULTS</b>The results suggested that the titers obtained by ELISA based method are consistent with those obtained by IFA based method (R = 0.999) and the plaque assay titration method (R = 0.949).</p><p><b>CONCLUSION</b>The novel ELISA based titration method with high sensitivity and specificity is easy to manage and perform, and can overcome the subjectivity associated with result determination of the fluorescence assay and plaque assay based methods. The novel ELISA based titration method can also be applied to high throughput detection.</p>

Recent advance in phlebovirus / 病毒学报

Genus Phlebovirus is single negative-strand RNA virus, and belongs to family bunyaviridae. Its genomes have three segments including L, M and S encoding RNA-dependent RNA polymerase, envelope glycoprotein and nucleoprotein respectively. Phlebovirus is arbovirus and can be disseminated by arthropod. More than 70 types of Phlebovirus so far have been reported, and 68 known serotypes are divided into groups Sandfly fever and Uukuniemi, of which a few members are closely related to human diseases. In addition, new emerging viruses of genus Phlebovirus are discovered recently. In this review, the latest research progress in molecular characteristics, epidemiology, diagnosis, treatment and emerging viruses of Phlebovirus is summarized.

Epidemiologic analysis on severe fever with thrombocytopenia syndrome in Hubei province, 2010 / 中华流行病学杂志

Objective To identify the epidemic characteristics and risk factors of an emerging infectious disease-severe fever with thrombocytopenia syndrome (SFTS) in Hubei province.Methods Active surveillance program on SFTS was set up in monitoring sites-hospitals,at the township level or above,in Suizhou,Huanggang and Wuhan from January to December,2010.Specific surveillance program on SFTS was launched across the province in hospitals above the county level.Cases that matched the definition of surveillance case were identified and reported to Centers for Disease Control and Prevention (CDCs).Cases were interviewed and their blood samples collected and detected using PCR and virus isolation.We also conducted serum antibody surveys among healthy population and livestock and surveillance on vector ticks in those high-epidemic areas.Results 188 cases that matched the definition of surveillance case and 21 deaths were reported in 11 cities,32 countries and 100 towns in 2010,with an incidence rate of 0.33/106.The fatality rate was 11.2％.Data showed that the patients were from hilly areas at the altitude elevated between 28-940 meters.The epidemic period was between April and December with the peak from May to September.The youngest case was an 11-year old,while the eldest was 81 with median age as 56-year old.95.3 ％ of the patients were farmers.All Patients did not have the history of traveling,two weeks before the onset of SFTS.93.6％ of the patients engaged in different kind of work which was associated with agriculture.52.8％ of the patients had been exposed to ticks.22.0％ of the patients had been bitten by ticks.Skin injury was found in 64.2％ of the patients.Samples from 129 cases (68.6％) were collected and detected,with 67.4％ of them (87 cases) showed positive by Real time-PCR for SFTS virus.An elevation in antibody titer by a factor of four or evidence of sero-conversion was observed in 11 patients; SFTS virus was isolated from 2 patients.The total antibody positive rates were 3.8％,55.0％ (6/11 ),36.7％ (2/3) and 80.0％ (4/5) respectively in healthy population,dogs,sheep and cows.Ticks from grass,cattle and sheep were detected positive by Real time-PCR.Conclusion Most cases of SFTS in Hubei were infected by SFTS virus,and cases of livestock were infected by SFTS virus.Ticks might serve as an important vector.Skin injury,exposure to tick bites seemed to be the risk factors.

Establishment of minireplicon system for severe fever with thrombocytopenia syndrome bunyavirus / 病毒学报

Severe fever with thrombocytopenia syndrome bunyavirus is a newly emerging virus in China, enveloped with a tripartite, single-stranded RNA genome of negative polarity. The regulatory elements for viral transcription and replication, as well as encapsidation and packaging signals, are thought to be located within these noncoding regions (NCRs). The terminal nucleotides are genus specific and highly conserved. The function of the remaining nucleotides of the NCRs is still not well understood. In this study, we developed the plasmid-driven RNA polymerase I minireplicon system for SFTSV firstly, using reporter genes GFP and luciferase. The function of the noncoding regions of the three Bunyaviridae RNA segments (L, M, S) in transcription was analyzed. Reporter genes are successfully expressed in SFTSV minireplicon system. Our results suggest that the NCRs of SFTSV from all three segments contain the necessary signals to initiate transcription. Quantitative detection of the luciferase expression level shows that promoter activity in the three segments is different.

Isolation, identification and characterization of SFTS bunyavirus from ticks collected on the surface of domestic animals / 病毒学报

To understand the maintenance and transmission of SFTS virus, the potential vector ticks were collected from sheep, cattle and dogs in the endemic areas of SFTSV in Shandong Province. Among the collected ticks, the dominant species was H. longicornis ticks. Real-time PCR for RNA detection, virus isolation and characterization, genomic sequencing, phylogenetic and antigenic analysis were performed in this investigation. The results showed that the SFTS viral RNA was detected in 2.14% H. longicornis, and a SFTS virus was isolated from one of viral RNA positive ticks collected from sheep. Whole genome analysis of the SFTSV isolates with 11 human-origin SFTS virus revealed a highly pairwise similarity, and the growth curve analysis showed nearly identical in virus yield and the dynamic of virus reproduction compared to human derived viral isolates. Immunofluorescence and neutralization test showed identical serological reaction character of the two different origin viral strains. In this study, the characters of a SFTSV isolate was firstly described, which suggested that the tick species H. longicornis acting important vector role in the transmission of SFTS virus.

Secreted expression of dengue virus type 2 envelope glycoprotein in eukaryotic cells / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To secreted express envelope glycoprotein (E) of dengue virus type 2 extracellularly.</p><p><b>METHODS</b>The entire prM/E gene was amplified by RT-PCR. An optimized signal sequence gene from Japanese encephalits virus (JEV, SA14-14-2 strain) was introduced using fusion PCR. The impact of E protein transmembrane and cytoplasmatic domains was compared by amplifying prM and E with full length of E gene, with 20% truncation of the E gene at 3' terminus and one chimeric gene, which was generated by replacing the 3' terminal 20% region of E gene with the corresponding sequence of JEV (SA14-14-2 strain). The PCR segments were inserted into the NheI and NotI sites of pcDNA5/FRT vector or into the NheI and XhoI sites of pAcUW51-M. Then they were transfected into 293T cells or Sf9 cells respectively. The expression and secretion of E protein were detected by immunofluorescence assay (IFA) and Western Blot.</p><p><b>RESULTS</b>After transected into 293T cells or Sf9 cells, all constructs expressed E protein intracellularly indentified by IFA while only two plasmids could secret detectable E protein into tissue culture using Western Blot analysis.</p><p><b>CONCLUSION</b>Signal peptide as well as the transmembrane and cytoplasmatic domains is crucial for the secretion of dengue E protein.</p>

Generation of recombinant human antibodies for EV71 virus / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To obtain recombinant human anti-EV71 antibodies from a EV71-associated hand-foot-and-mouth disease patient-derived antibody phage library.</p><p><b>METHODS</b>A combinatorial human scFv library to enterovirus 71 (EV71) virus was constructed using antibody genes harvested from the blood of EV71 virus patients. The library was panned and selected by using purified VP1 protein of EV71 virus with phage display. After that the specific antibody was converted to full human IgG antibody with recombinant baculovirus/insect cell system.</p><p><b>RESULTS</b>One unique human scFv antibody specific for EV71 virus VP1 protein was obtained by ELISA, IFA and analysis of the antibody DNA sequence. The specific anti-VP1 human scFv antibody was converted to full human IgG antibody with recombinant baculovirus/insect cell system. The full human IgG antibody was tested in vitro for EV71 virus neutralization, resulting in no neutralizing activity with EV71 A type and EV71 C4 subtype.</p><p><b>CONCLUSION</b>The obtained human anti-EV71 antibodies without neutralizing activity laid the foundation for diagnosis of human EV71-associated hand-foot-and-mouth disease.</p>

Expression of structural and non-structural proteins of severe fever with thrombocytopenia syndrome bunyavirus / 病毒学报

Severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) is a novel phlebovirus, causing a life-threatening illness associated with the symptoms of severe fever and thrombocytopenia syndrome. The sequence and structure of the genome have already been illustrated in previous study. However, the characteristics and function of the structure and non-structure proteins is still unclear. In this study, we identified the density of the purified SFTSV virions as 1.135 g/mL in sucrose solution. Using RT-PCR method, we amplified the full coding sequence of RNA dependent RNA polymerase(RdRp), glycoprotein precursor (M), glycoprotein n (Gn), glycoprotein c (Gc), nuclear protein (NP) and non structural protein (NSs) of SFTSV (strain HB29). Respectively inserted the target genes into eukaryotic expression vector pcDNA5/FRT or VR1012, the target protein in 293T cell were successfully expressed. By analyzing the SFTSV virions in SDS-PAGE and using recombinant viral proteins with SFTS patients sera in Western blotting and Immunofluorescent assay, the molecule weight of structure and non-structure proteins of SFTSV were defined. The study provides the first step to understand the molecular characteristics of SFTSV.

The development of neutralizing human antibodies against rabies virus / 病毒学报

A combinatorial human Fab library to the rabies virus was constructed using antibody genes derived from the blood of vaccinated donors. The library were panned and selected on purified rabies virus particles of aG or CTN strain with phage display. Eleven unique human Fab antibodies specific for the rabies virus glycoprotein were obtained by ELISA, IFA and DNA sequences analysis of these antibodies. Among these Fab antibodies, five human Fab antibodies were converted to full-length human IgG antibodies with recombinant baculovirus system. The five full-length human IgG antibodies were tested in vitro for rabies virus neutralization, resulting in all specificities to neutralize the virus. The obtained human anti-rabies antibodies lay the basis for the production of cocktail of anti-rabies monoclonal antibody with chinese intellectual property.

Development of pseudoviral competitive internal controls for RT-PCR detection of dengue virus / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>Development of pseudoviral competitive internal controls for RT-PCR laboratory detection of dengue virus.</p><p><b>METHODS</b>The internal controls target gene were obtained by insertion of a 180 bp non-related DNA fragment into RT-PCR detection target of dengue virus between the forward and reverse PCR primer binding regions. A yellow florescence protein reporter gene was induced at downstream of internal controls target gene via internal ribosome entry site gene. HEK 293T cells were transfected with plasmid containing this whole cassette and lentiviral packaging support plasmid. Pseudoviral particle was recovered from the supernatant and analyzed quantitatively and qualitatively in simulated samples at the same tube under different experimental conditions.</p><p><b>RESULTS</b>The established pseudoviral competitive internal controls can be used in the RT-PCR detection of different serotype dengue virus and the whole detection process can be monitored. The obtained fragment is easy to be differentiated in agarose electrophoresis.</p><p><b>CONCLUSION</b>The pseudoviral competitive internal controls could be used for the quality control of the laboratory diagnosis process, simple to prepare, stable for storage, easy to be transformed into internal controls for other RNA virus.</p>

Expression and function analysis of dengue virus type 1 to 4 envelope domain III recombinant fusion protein / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To observe the ability of dengue virus type 1-4 envelope domain III fusion protein to inhibit virus infection and analyze the neutralizing ability of polyclonal antibodies against rE III.</p><p><b>METHODS</b>After being connected by linker peptide, E III protein of Dengue virus serotypes 1-4 were expressed in E coli BL21 (DE3) then purified. Fusion proteins were verified by Western Blot and ELISA. Rabbits were immunized with fusion proteins to produce anti-rE III serum. The activity of anti-rE III serum were detected through indirect immunofluorescence assay test. Inhibition of dengue virus type 1 to 4 infection in BHK-21 cells by rE III fusion protein were tested. Neutralizing activity of anti-rE III serum was analyzed.</p><p><b>RESULTS</b>Dengue virus type 1 to 4 envelope domain III recombinant fusion protein was expressed in E coli BL21 and purified successfully. Then rE III fusion protein and anti-rE III serum were analyzed respectively and rE III fusion protein can effectively inhibit dengue virus type 1 to 4 from infecting BHK cells. The anti-rE III serums can neutralize dengue virus type 1 to 4 but with different neutralizing titer.</p><p><b>CONCLUSION</b>Dengue virus type 1-4 envelope domain III fusion protein can directly inhibit DV infection. Antibodies induced by rE III fusion proteins can neutralize dengue virus type 1-4.</p>

Fluorescent microbeads-based multiplex detection of IgM antibodies to pathogens caused viral hemorrhagic fever / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To develop and evaluate a multiplex detection of IgM antibodies to pathogens caused viral hemorrhagic fever.</p><p><b>METHODS</b>The nucleocapsid proteins (NP) of HTN, SEO, Puu MBV, Lassa, RFV and HPS viruses expressed in prokaryotic cells and purified were coupled to 7 different xMAP fluorescent microbeads. The assay was evaluated and optimized when screened against a panel of reference sera collected from HFRS patients, and compared to commonly used MacELISA Kits.</p><p><b>RESULTS</b>For detection of anti-NP antibodies, the sensitivity and specificity of the assay were comparable to a commonly used MacELISA kit, but it could detect different antigen specific antibodies in one reaction simultaneously.</p><p><b>CONCLUSION</b>A robust, rapid and multiplex assay based on NPs could be developed via Luminex xMAP platform for laboratory diagnosis of viral hemorrhagic fever and seroepidemiological investigation.</p>

Secreted expression of dengue virus type I envelope glycoprotein in 293T cells / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To expression prM/E gene of dengue virus type I in mammalia cells.</p><p><b>METHODS</b>The full-length prM/E gene of dengue virus type I strain GZ01/95 was amplified by RT-PCR, the signal peptide preceding the prM gene was added or the carboxyl-terminal 20% of DEN-1 E was replaced with the corresponding JE sequence in the meanwhile, and three of the constructions were cloned into the pcDNA5/FRT.Then they were transfected into 293T cells by lipofectamine respectively. The expression of recombinant proteins were identified by indirect immuno-fluorescence assay(IFA) as well as Western blot.</p><p><b>RESULTS</b>In the cytoplasm of 293T cells transfected with all the recombinant plasmids DNA, the expressed products for gene of dengue virus type I were confirmed by IFA. The secreted expression products for gene of dengue virus type I specific protein bands were confirmed by Western blot only existing in the cell supernatants transfected with the modified recombinant plasmids DNA.</p><p><b>CONCLUSION</b>The prM/E protein of dengue virus type 1 were expressed in 293T cells transfected with all the three recombinant plasmids DNA. The prM/E protein was obtained secretion after transfecting the modified recombinant plasmids adding a signal peptide preceding the prM gene or replacing the carboxyl-terminal 20% of E with the corresponding JE sequence.</p>