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Objective:To grasp the distribution of fine antigenic epitope profiles of nucleoprotein (NP) and glycoprotein (GP) fragments of Crimean-Congo hemorrhagic fever virus (CCHFV) and to clarify the value of dominant antigenic epitopes in laboratory testing of Crimean-Congo hemorrhagic fever (CCHF).Methods:In a minimal synthetic short peptide consisting of 8 amino acids was segmentally expressed by CCHFV YL04057 strain using a modified bio-peptide synthesis method from 2014 to 2021 in the laboratory of Xinjiang University, College of Life Sciences. Using CCHFV polyclonal antibody or monoclonal antibody 14B7 (IgM) or CCHFV-positive sheep serum as antibodies, the minimal antigenic epitopes (BCEs) with antigenic activity on NP and GP fragments were identified by immunoblotting, and the obtained BCEs with sequence polymorphism were spatially clustered with CCHFV from different regions using the neighbor-joining method to determine the combination mode of BCEs with geographical correlation of regional distribution, to explore its application in establishing serological diagnosis. A prokaryotic expression plasmid (pET-32a), an E. coli expression plasmid (pGEX-KG) and a prokaryotic expression plasmid with an incomplete glutathione (GST188) tag (pXXGST-ST-1) were used to construct and express six dominant antigenic epitopes of different peptide lengths on NP fragments, and an indirect Enzyme-linked immunosorbent assay (ELISA) was established. CCHF sheep serum identified by immunofluorescence assay (IFA) was used as a control, and the specificity, sensitivity and overall compliance of the recombinant proteins with different peptide lengths of antigenic epitopes with IFA assay results were statistically analyzed. Results:CCHFV, NP and GP fragments had a total of 30 antigenically active BCEs, among which the core intermediate fragment NP2 (aa 170 th-305 th), which had a concentration of antigenic epitopes in the NP fragment, has 6 BCEs, and the NP1 (aa 1 st-200 th) and NP3 (aa 286 th-482 nd) at both ends have 9 BCEs; the Gc (aa 1 st-558 th) and Gn (aa 533 th-708 th) fragments of the GP fragment have 14 BCEs and a long antigenic peptide (AP) containing 15 amino acids, and the amino acid sequence homology of the NP fragment BCEs was 97.1% and that of the GP fragment BCEs was 89.1%. There was a significant difference ( P=0.0281, P<0.05). Among the 9 BCEs with sequence polymorphism in the GP fragment, 6 combined BCEs from GnEc1, GnE2, GnE4, GcE3, GcE6 and GcAP-4 (Ap) could cluster 15 CCHFV strains from different regions of the world into 5 geographical taxa, AsiaⅠ, AsiaⅡ, AficaⅠ, AficaⅡ and Europe. The constructs expressing PET-32a-NP (full length), PGEX-KG-NP2 (aa 170 th-305 th), pGEX-KG-NP2-1 (aa 235 th-275 th), PGEX-KG-NP2-1-1 (aa 237 th-256 th), pXXGST-1-NP2-1-2 (aa 250 th-265 th) and PGEX KG-NP2-1-3 (aa 260 th-276 th), six recombinant proteins CCHFV NP rabbit polyclonal antiserum (pAb) Western Blotting reaction positive, 33 sheep sera tested by IFA XHF as a reference, the sensitivity of the assay established by indirect ELISA using the recombinant proteins constructed from two fragments of NP2 and NP2-1 as antigens. The sensitivity, specificity and overall compliance were the best, with 73.4% (11/15) and 66.7% (10/15) for sensitivity, 100% (18/18) and 94.4% (17/18) for specificity, and 87.9% (29/33) and 81.8% (27/33) for overall compliance. Conclusion:CCHFV NP and GP are distributed with a high number of BCEs with antigenic immunoreactivity, among which the dominant antigenic epitopes are of high value in the laboratory serological diagnosis of CCHF.
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Objective:To investigate the effects of different chimerism strategies and different immune ways on the two antigen-dominant regions of Xinjiang hemorrhagic fever virus (XHFV) glycoprotein.Methods:The 5' end was added or not added with interleukin-2 (IL-2) signal peptide and the general-purpose auxiliary T cell epitopes as different design strategies. GcⅠ and GcⅡ and the epitopes previously identified on GcⅠ (Gc 233-248, Gc 241-256 and Gc 281-296) were fused and constructed into the eukaryotic expression vector pVAX1 and the prokaryotic expression vector pET-28a. The recombinant prokaryotic plasmid transformed into E.coli BL21 was induced and purified, and the recombinant eukaryotes were extracted by indirect immunofluorescent assay. BALB/c mice were immunized by protein immunity, gene immunity, and DNA prime-protein boost immunity. The IgG antibody level was measured by ELISA. The immune effect was evaluated by the proliferation of T-lymphocytes and the content of cytokines in the spleen. Results:The results of double enzyme digestion and sequencing showed that eight recombinant plasmids were successfully constructed, and the recombinant eukaryotes were successfully expressed in vitro by fluorescence microscopy. After three times of immunization, the IgG level and the proliferation of T-lymphocytes in the spleen of mice in the experimental group were significantly higher than those in the control group ( P<0.01). The mass concentration test results of Th2 cytokines IL-4 and Th1 cytokines interferon-gamma (IFN-γ) revealed that the response of the DNA prime-protein boost immunity was biased to Th1. Conclusions:The multi-epitope chimeric vaccine of XHFV glycoprotein was successfully constructed, and the target antigen could be expressed effectively in vivo. The immune groups stimulated stronger humoral and cellular immune responses compared with the control group. Among them, the immune effect of pVAX1-ST(GcⅠe+GcⅡ) combined with recombinant protein r(GcⅠe+GcⅡ) was the best, and it is expected to be a new candidate vaccine for XHFV.
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Objective To express and purify two domains GcⅠand GcⅡof Xinjiang hemorrhagic fever virus (XHFV) glycoprotein, and to study its immunogenicity and the effects on immune response in mice. Methods The prokaryotic expression plasmids of pET28a-GcⅠand pET32a-GcⅡwere constructed and transformed into E. coli BL21, respectively. The expression and purification conditions of rGcⅠand rGcⅡproteins were optimized. The antigenicity of the fusion protein was detected by Western Blot and enzyme-linked immunosorbent assay (ELISA). BALB/c mice were immunized by protein immunization and DNA priming-protein boosting. The mice were randomly divided into 5 groups, including pVAX1-GcⅠ+rGcⅠgroup, pVAX1-GcⅡ+rGcⅡgroup, rGcⅠgroup, rGcⅡgroup and saline group (control group) with 7 mice in each group. The serum antibody titer of mice was detected by indirect ELISA, and the immune effect was evaluated by spleen T lymphocyte proliferation assay and cytokine content determination. Results The fusion proteins rGcⅠand rGcⅡwere purified and obtained, which could react with positive serum of sheep and had good antigenicity. After three immunizations, the IgG levels in the serum of each experimental group were significantly higher than those in the control group (all P<0.001). The serum antibody titers of the experimental groups were reached above 1:12800. Among them, the concentration of Th2 type cytokine interleukin-4 (IL-4) in the spleen cell culture supernatant of rGcⅡ[(79.97±7.47) ng/L] and pVAX1-GcⅡ+rGcⅡgroup [(61.43±9.27) ng/L] was significantly higher than (24.29±3.81) ng/L of the control group, respectively (all P<0.01). The highest mass concentration [(42.46 ±2.60) ng/L] of Th1 type cytokine interferon-γ(IFN-γ) was observed in the pVAX1-GcⅡ+rGcⅡ group, which was significantly higher than (20.33±1.67) ng/L of the control group, and the difference was statistically significant (P<0.001). That showed a significant antigen-specific splenic T lymphocyte proliferation (P<0.001). Conclusions The purified recombinant proteins rGcⅠand rGcⅡhave good immunogenicity, which can make the immune system T lymphocytes tend to Th2 response, and pVAX1-GcⅡ combined with recombinant protein GcⅡ can induce better antigen-specific immune effect. And pVAX1-GcⅡ combined with recombinant protein GcⅡis expected to be used as vaccine candidates for the prevention and control of XHFV.
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Objective@#To construct the recombinant Crimean-Congo hemorrhagic fever virus (CCHFV) which can express the secreted nanoluciferase (NanoLuc) and investigate its potential application for rapid antiviral compounds screening.@*Methods@#The ORF of NanoLuc and the mucin encoded by the M segment of CCHFV were merged, and the recombinant CCHFV (rCCHFV) was rescued through reverse genetic system. Then rCCHFV was used to evaluate the antiviral effect for ribavirin and Furin inhibitor in vitro.@*Results@#The rCCHFV_mucin_NLuc with NanoLuc reporter was obtained, and the relative light unit (RLU) which can reflect NanoLuc activity was positively correlated with median tissue culture infective dose (TCID50) in the infected cell supernatant (cor=0.998, P=0.001). When the concentration for the compounds was 10 μmol/L, there was no significant difference for the NanoLuc activity in the infected cell supernatant between Furin inhibitor and ribavirin (P > 0.1) from day 1 to 3 after treatment. But at day 4, the NanoLuc activity in Fruin inhibitor treated group was significantly higher than that of ribavirin treated group (P=0.001), and no significant difference was found between the Furin inhibitor and untreated group (P > 0.1).@*Conclusions@#The rCCHFV with NanoLuc reporter was recovered successfully and it could be used for the primary rapid screening of antiviral compounds in future.
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Objective To establish a one-step recombinase polymerase amplification (RPA) method for pathogen screening and rapid detection in the field targeting for five hemorrhagic fever related viruses (Zaire ebola virus, Sudan ebola virus, Marburg virus, Lassa virus and Yellow fever virus). Methods The specific nucleic acid (NA) fragments of each virus were selected as target genes by genome sequence analysis, and the primers and probes for RPA assays were designed according to the sequence. A series of diluted template genes were used for RPA detection to determine the sensitivity. The hemorrhagic fever-related viral nucleic acids were used for RPA detection to determine the specificity. The amplification experiments were carried out at different temperature ranging from 37℃ to 42℃ to validate the reaction temperature range. Results The RPA reaction systems of the five hemorrhagic fever viruses could effectively amplify the target genes, the sensitivities were between 1.5×102 and 1.5×103 copies. No cross reactions existed with the other hemorrhagic fever-related viral genes. Meanwhile, RPA assay could effectively amplify the target genes at 37-42℃. Conclusion The isothermal RPA assays of five hemorrhagic fever viruses are established, which may amply target genes fast and react at a wide temperature range, and be potentially useful for in field pathogens detection.
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Objective To construct two DNA vaccines based on two glycoprotein antigen segments of Xinjiang hemorrhagic fever virus (XHFV) and to evaluate the immune responses in BALB/c mice following vaccination.Methods Two recombinant expression plasmids pVAX1-GcⅠand pVAX1-Gc Ⅱ were constructed by inserting XHFV YL04057 strain Gc Ⅰ (1 229-1 349 aa) and Gc Ⅱ (1 443-1 566 aa) fragments into the eukaryotic expression vector pVAX1 and then were identify by restriction enzyme digestion and sequencing analysis.The recombinant expression plasmids were transfected into mice by hydrodynamics-based transfection.Immune responses induced in mice were evaluated by testing the proliferation of T cells with MTT,measuring serum antibody level with ELISA and detecting cytokines in the supernatant of spleen cell culture with ELISA kit.Results The recombinant expression plasmids were successfully constructed as indicated by the results of restriction enzyme digestion and sequencing analysis.Expression of Gc Ⅰ and Gc Ⅱ genes in mice liver tissues was detected.Antibody titers in mice immunized with pVAX1-GcⅠor pVAX1-Gc Ⅱ were higher than those in mice immunized with pVAX1.Compared with pVAX1,pVAX1-Gc Ⅱ significantly enhanced the proliferation of splenic T lymphocytes and the expression of IFN-γ (P<0.01).Conclusion The constructed two DNA vaccines for XHFV can induce specific humoral and cellular immune responses in mice.pVAX1-Gc Ⅱ is better than pVAX1-GcⅠin immunogenicity and protective efficacy,suggesting that it can be used as a promising candidate for the development of DNA vaccine for XHFV.
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Severe Fever with Thrombocytopenia Syndrome (SFTS) and Crimean-Congo Haemorrhagic Fever (CCHF) are tick-borne diseases belonging to the family Bunyaviridae. Since SFTS was first reported in China in 2009, the virus was isolated and confirmed in 2011, with additional reports of SFTSV expanding its geographic range from China to South Korea and Japan. CCHFV has the widest geographic distribution of any tick-borne virus, encompassing around 30 countries from eastern China through Asia, the Middle East, and southeastern Europe to Africa. During the past decade, CCHFV has emerged in new areas of Europe, Africa, the Middle East, and Asia and has increased in endemic areas. Migratory birds are considered to play a role in dispersing CCHFV vectors, and the virus. This review summarises SFTSV and CCHFV, highlighting the role of migratory birds in the transmission of tick-borne disease.
Subject(s)
Humans , Africa , Asia , Birds , Bunyaviridae , China , Europe , Fever , Hemorrhagic Fever Virus, Crimean-Congo , Japan , Middle East , Republic of Korea , Thrombocytopenia , Tick-Borne Diseases , VirusesABSTRACT
Crimean-Congo hemorrhagic fever (CCHF) is a severe illness with high fatality.Cases are reported in several countries in Africa,Europe,the Middle East,and Asia.Phylogenetic analyses based on the virus S (nucleocapsid),M (glycoprotein),and L (polymerase) genome segments sequences indicate distinct geographic lineages exist but their specific genetic characteristics require elucidation.In this work we collected all full length S segment sequences and generated a phylogenetic tree based on the alignment of these 62 samples.We then analyzed the alignment using entries from AAIndex,the Amino Acid Index database,to identify amino acid mutations that performed significant changes in charge,pka,hydropathy and side chain volume.Finally,we mapped these changes back to the tree and alignment to identify correlated mutations or sites that characterized a specific lineage.Based on this analysis we are able to propose a number of sites that appear to be important for virus function and which would be good candidates for experimental mutational analysis studies.
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Crimean-Congo Haemorrhagic Fever Virus(CCHFV)is a tick-born virus of the Nairovirus genus within the Bunyaviridae family,which is widespread and causes,high fatality. The nucleocapsid of CCHFV is comprised of N proteins that are encoded by the S segment. In this research,the N protein of CCHFV was expressed in insect cells using a recombinant baculovirus. Under an electron microscope,Virus-Like Particles (VLPs)with various size and morphology were observed in cytoplasmic vesicles in the infected cells.Sucrose-gradient purification of the cell lysate indicated that the VLPs were mainly located in the upper fraction after ultracentrifugation,which was confirmed by Western blot analysis and immuno-electron microscopy(IEM).
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The Crimean-congo hemorrhagic fever virus(CCHFV)is a geographically widespread fatal pathogen.Identification of the epitope regions of the virus is important for the diagnosis and epidemiological studies of CCHFV infections.In this study,expression vectors carrying series truncated fragments of the NP(nueleoeapsid protein)gene from the S fragment of CCHFV strain YL04057 were constructed.The recombinant proteins were expressed in E.coli and purified for detection.The antigenic of the truncated fragments of NP was detected with a polyclonai serum(rabbit)and 2 monoclonal(mAbs)(14B7 and 43E5)against CCHFV by Western-blot analyses.The results showed that the three expressed constructs,which all contained the region 235AA to 305AA could be detected by mAbs polyclonal serum.The results suggest that region 235-305 aa of NP is a highly antigenic region and is highly conserved in the NP protein.
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Objective To study the cytopathogenic effect of epidemic hemorrhagic fever with renal syndrome virus (HFRSV) on renal tubular cells(RTC). Methods Human fetal renal tubular cells (HFRTC) were cultured in vitro. HFRTC infected or not infected by HFRSV were observed by using trypan-blue stain and transmission electron microscopy(TEM). Viral-mRNA was detected by in situ molecular hybridization. Results (1) HFRSV could directly infected HFRTC: (2)The death rate of HFRTC in the infection group was significantly higher than that in the control grou 1 to 4 weeks after infection; (3) Injuries of cell membrane and cell organs after infection with HFRSV were significantly earlier and more severe as compared to control by means of TEM. Conclusion HFRSV can directly damage renal tubular cells (RTC ), which contributes to the pathogenesis of hemorrhagic fever with renal syndrome (HFRS).
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Five strains out of the 8 of epidermic hemorrhagic fever(EHF)virus isolated from the serum of the acute phase of EHF patients in Nanchong, Sichuan were found to have cytopathogenic effect(CPE)through 4th to 10th passages in Vero-E6 cell culture. The biological, physico-chemical and antigenic characteristics of HFN-04 and HFN-19, 2 out of the 5 CPE strains, were identified. The results were as follows;( 1 ) The CPE development and the dynamic proliferation of the virus areconsistent. ( 2 ) The main biological and physico-chemical characteristics of the 2 CPEstrains arc the same as those of EHF virus.( 3 ) When paired samples of EHF patients' serum were tested with the slide antigens of E6 cells infected with these CPE strains, all the convalescent serum demonstrated an increase by 4 fold or more of the IFA. titer.( 4 ) The CPE of the virus can be neutralized by EHF patient's serum or EHF and KHF antisera, but not by normal rabbit serum or the multivalent serum of Reovirus type 1-3.( 5 ) The E6 cells infected by CPE strains of virus can almost fully absorbthe specific antibodies in EHF patients or in EHF and KHF antisera.( 6 ) The suspension of the mouse brain infected by CPE strains can formpositive agglutination reaction with the sentitized blood cells by EHFvirus strain A9 McAb 25-1.On the basis of our observation, it can be concluded that at least certain strains of EHF virus can produce CPE in Vero-E6 cell culture.