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Structure of TBEV virion. a Cryo-EM image of TBEV virions. The sample contained mature, immature (white arrows), half-mature (white arrowheads), and damaged (black arrows) particles. Scale bar 100 nm. b B-factor sharpened electron-density map of TBEV virion, rainbow-colored according to distance from particle center. The front lower-right eighth of the particle was removed to show the transmembrane helices of E-proteins and M-proteins. c Molecular surface of TBEV virion low-pass filtered to 7 Å. The three E-protein subunits within each icosahedral asymmetric unit are shown in red, green, and blue. The three E-proteins in the icosahedral asymmetric unit form unique interactions with each other (for more details, see Supplementary Fig. 2). The black triangle shows the borders of a selected icosahedral asymmetric unit. d Central slice of TBEV electron density map perpendicular to the virus 5-fold axis. The virus membrane is deformed by the transmembrane helices of E-proteins and M-proteins. The lower right quadrant of the slice is color-coded as follows: nucleocapsid—blue; inner and outer membrane leaflets—orange; M-proteins—red; E-proteins—green. Scale bars in b, c, and d represent 10 nm
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Tick-borne encephalitis virus (TBEV) causes 13,000 cases of human meningitis and encephalitis annually. However, the structure of the TBEV virion and its interactions with antibodies are unknown. Here, we present cryo-EM structures of the native TBEV virion and its complex with Fab fragments of neutralizing antibody 19/1786. Flavivirus genome deliv...
Citations
... Previously, the following TBEV structures were solved with the help of cryo-electron microscopy (cryo-EM) approach: a 3.9 Å structure of intact TBEV strain Hypr (PDB ID 5O6A [23], TBEV-Hypr), a 3.9 Å structure of TBEV strain Hypr complexed with Fab fragment of neutralizing antibody 19/1786 (PDB ID 5O6V [23]), a 3.3 Å structure of UV-inactivated TBEV strain Kuutsalo-14 (PDB ID 7Z51 [24], TBEV-Kuutsalo). Structures of immature TBEV virions from strains Kuutsalo-14, Neudoerfl, and Hypr (resolution 4-8 Å) have been described but not formally published yet [25]. ...
... Previously, the following TBEV structures were solved with the help of cryo-electron microscopy (cryo-EM) approach: a 3.9 Å structure of intact TBEV strain Hypr (PDB ID 5O6A [23], TBEV-Hypr), a 3.9 Å structure of TBEV strain Hypr complexed with Fab fragment of neutralizing antibody 19/1786 (PDB ID 5O6V [23]), a 3.3 Å structure of UV-inactivated TBEV strain Kuutsalo-14 (PDB ID 7Z51 [24], TBEV-Kuutsalo). Structures of immature TBEV virions from strains Kuutsalo-14, Neudoerfl, and Hypr (resolution 4-8 Å) have been described but not formally published yet [25]. ...
... Residues 14-18 (domain I) were not resolved in two of three independent subunits. We also did not observe electron density for any parts of the M protein as well as for stem and anchor regions of E protein ( Figure 1D), in contrast to the previously published TBEV structures [23,24]. Disorder in the transmembrane region of our structure is likely caused by the formaldehyde treatment upon the virus inactivation. ...
Tick-borne encephalitis virus (TBEV) causes a severe disease, tick-borne encephalitis (TBE), that has a substantial epidemiological importance for Northern Eurasia. Between 10,000 and 15,000 TBE cases are registered annually despite the availability of effective formaldehyde-inactivated full-virion vaccines due to insufficient vaccination coverage, as well as sporadic cases of vaccine breakthrough. The development of improved vaccines would benefit from the atomic resolution structure of the antigen. Here we report the refined single-particle cryo-electron microscopy (cryo-EM) structure of the inactivated mature TBEV vaccine strain Sofjin–Chumakov (Far-Eastern subtype) at a resolution of 3.0 Å. The increase of the resolution with respect to the previously published structures of TBEV strains Hypr and Kuutsalo-14 (European subtype) was reached due to improvement of the virus sample quality achieved by the optimized preparation methods. All the surface epitopes of TBEV were structurally conserved in the inactivated virions. ELISA studies with monoclonal antibodies supported the hypothesis of TBEV protein shell cross-linking upon inactivation with formaldehyde.
... IgG molecules have a negative charge at pH 7.4 [36], which is favorable for their interaction with PEI. Since the groups of negatively charged PSS completely dissociate in an experimental setting and help to form stable proteinpolyelectrolyte complexes [37,38], it was used as a second polyelectrolyte. We examined the simplest matrix, which contained one layer of PEI and one layer of PSS, in order to identify the thinnest modifying layer of the surface relevant to the desired Debye length. ...
... IgG molecules have a negative charge at pH 7.4 [36], which is favorable for their interaction with PEI. Since the groups of negatively charged PSS completely dissociate in an experimental setting and help to form stable protein-polyelectrolyte complexes [37,38], it was used as a second polyelectrolyte. We examined the simplest matrix, which contained one layer of PEI and one layer of PSS, in order to identify the thinnest modifying layer of the surface relevant to the desired Debye length. ...
Immunosensors based on field-effect transistors with nanowire channels (NWFETs) provide fast and real-time detection of a variety of biomarkers without the need for additional labels. The key feature of the developed immunosensor is the coating of silicon NWs with multilayers of polyelectrolytes (polyethylenimine (PEI) and polystyrene sulfonate (PSS)). By causing a macromolecular crowding effect, it ensures the “soft fixation” of the antibodies into the 3-D matrix of the oppositely charged layers. We investigated the interaction of prostate-specific antigen (PSA), a biomarker of prostate cancer, and antibodies adsorbed in the PEI and PSS matrix. In order to visualize the formation of immune complexes between polyelectrolyte layers using SEM and AFM techniques, we employed a second clone of antibodies labeled with gold nanoparticles. PSA was able to penetrate the matrix and concentrate close to the surface layer, which is crucial for its detection on the nanowires. Additionally, this provides the optimal orientation of the antibodies’ active centers for interacting with the antigen and improves their mobility. NWFETs were fabricated from SOI material using high-resolution e-beam lithography, thin film vacuum deposition, and reactive-ion etching processes. The immunosensor was characterized by a high sensitivity to pH (71 mV/pH) and an ultra-low limit of detection (LOD) of 0.04 fg/mL for PSA. The response of the immunosensor takes less than a minute, and the measurement is carried out in real time. This approach seems promising for further investigation of its applicability for early screening of prostate cancer and POC systems.
... There are five different protein structures of the Crimean-Congo haemorrhagic disease determined in the literature. These are Crimean Congo Haemorrhagic Fever Gn zinc finger (PDB ID=2L7X) [29], Structural analysis of a viral OTU domain protease from the Crimean-Congo Haemorrhagic Fever virus in complex with human ubiquitin (PDB ID=3PRP) [30], Envelope glycoprotein from tick-borne encephalitis virus (PDB ID=1SVB) [31], A RNA binding protein from Crimean-Congo haemorrhagic fever virus (PDB ID=3U3I) [32] and The cryo-EM structure of Tick-borne encephalitis virus complexed with Fab fragment of neutralizing antibody (PDB ID=5O6V) [33]. The binding energies and interaction types of synthesized and hypothetical complexes with target proteins determined for antibacterial and antiviral effects were examined. ...
For the first time, electronic characteristics of potential drug candidates and their inhibitory activities have been linked thanks to this work. Synthesized copper and nickel complexes with trans-N1,N8-bis(2-cyanoethyl)-2,4,4,9,11,11-hexamethyl-1,5,8,12-tetraazacyclotetradecane (tet-bx) ligand, as well as the proposed hypothetical complexes, were properly examined by the appropriate calculation method in atomic and molecular dimensions. The appropriate calculation level was achieved by using the IR spectroscopic data of the tet-bx ligand. The experimental and calculated bond stretching frequencies were compared for synthesized complexes [Ni(tet-bx)](ClO4)2 (1), [Cu(tet-bx)](ClO4)2 (2), [Ni(tet-bx)(NCS)2] (3), and [Ni(tet-bx)(ClO4)Cl] (5). Some bond stretching frequencies of hypothetical complexes [Cu(tet-bx)(NCS)2] (4) and [Cu(tet-bx)(ClO4)Cl] (6) have also been proposed and their molecular structure were determined. To analyze the electronic behavior of the examined complexes at the atomic level, Fukui function indices (nucleophilic f+ and electrophilic f- populations) were determined. Furthermore, antibacterial and antiviral inhibition efficiency of the complexes against Crimean-Congo hemorrhagic fever has been investigated by docking studies
... The traditional view is that a virus must infect the tick midgut cells, replicate, and be released from the midgut prior to dissemination to other tick organs (Franz et al., 2015;Füzik et al., 2018;Lejal et al., 2019). Although virus-midgut interaction plays an important role in the biology of TBFV infections, the detailed process by which TBFV infect and exit the tick midgut remains unclear. ...
... The nucleocapsid consists of the genome and the C protein and is surrounded by the viral envelope, which consists of both M and E glycoproteins and host-cell-derived lipids. Glycoprotein E is the major antigen of TBEV and is responsible for receptor binding and membrane fusion [8,9]. The glycoprotein-E-coding gene is commonly sequenced and analyzed, but a pairwise distance analysis indicated that it has evolutionary patterns distinct from other TBEV genomic regions [10]. ...
... The nucleocapsid consists of the genome and the C protein and is surrounded by the viral envelope, which consists of both M and E glycoproteins and host-cell-derived lipids. Glycoprotein E is the major antigen of TBEV and is responsible for receptor binding and membrane fusion [8,9]. The glycoprotein-E-coding gene is commonly sequenced and analyzed, but a pairwise distance analysis indicated that it has evolutionary pa erns distinct from other TBEV genomic regions [10]. ...
The tick-borne encephalitis virus (TBEV) is the arboviral etiological agent of tick-borne encephalitis (TBE), considered to be one of the most important tick-borne viral diseases in Europe and Asia. In recent years, an increase in the incidence of TBE as well as an increasing geographical range of the disease have been noted. Despite the COVID-19 pandemic and the imposition of restrictions that it necessitated, the incidence of TBE is rising in more than half of the European countries analyzed in recent studies. The virus is transmitted between ticks, animals, and humans. It seems that ticks and small mammals play a role in maintaining TBEV in nature. The disease can also affect dogs, horses, cattle, and small ruminants. Humans are incidental hosts, infected through the bite of an infected tick or by the alimentary route, through the consumption of unpasteurized milk or milk products from TBEV-infected animals. TBEV infections in humans may be asymptomatic, but the symptoms can range from mild flu-like to severe neurological. In Europe, cases of TBE are reported every year. While there is currently no effective treatment for TBE, immunization and protection against tick bites are critical in preventing this disease.
... Similar to other orthoflaviviruses, TBEV forms spherical particles approximately 50 nm in diameter with a genome consisting of singlestranded positive sense RNA (Füzik et al., 2018;Pulkkinen et al., 2022;Pulkkinen et al., 2018). The genome encodes a large polyprotein further divided into three structural proteins (envelope protein E, (pre) membrane protein (pr)M, and capsid protein C) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) (Lindenbach and Rice, 2003). ...
Vaccine-induced protection against tick-borne encephalitis virus (TBEV) is mediated by antibodies to the viral particle/envelope protein. The detection of non-structural protein 1 (NS1) specific antibodies has been suggested as a marker indicative of natural infections. However, recent work has shown that TBEV vaccines contain traces of NS1, and immunization of mice induced low amounts of NS1-specific antibodies. In this study, we investigated if vaccination induces TBEV NS1-specific antibodies in humans.
Healthy army members (n=898) were asked to fill in a questionnaire relating to flavivirus vaccination or infection, and blood samples were collected. In addition, samples of 71 suspected acute TBE cases were included. All samples were screened for the presence of TBEV NS1-specific IgG antibodies using an in-house developed ELISA. Antibodies were quantified as percent positivity in reference to a positive control. For qualitative evaluation, cut-off for positivity was defined based on the mean OD of the lower 95% of the vaccinated individuals +3 SD.
We found significantly higher NS1-specific IgG antibody titers (i.e., quantitative evaluation) in individuals having received 2, 3, or 4 or more vaccine doses than in non-vaccinated individuals. Similarly, the percentage of individuals with a positive test result (i.e., qualitative evaluation) was higher in individuals vaccinated against tick-borne encephalitis than in unvaccinated study participants. Although NS1-specific IgG titers remained at a relatively low level when compared to TBE patients, a clear distinction was not always possible. Establishing a clear cut-off point in detection systems is critical for NS1-specific antibodies to serve as a marker for distinguishing the immune response after vaccination and infection.
... Cryo-electron micrographs reveal that TBEV virions are smooth, with a diameter of 50 nm, comparable to other flaviviruses. [31][32][33][34][35] The virion comprises a nucleocapsid (NC), surrounded by a membrane composed of host-derived lipids with embedded viral envelope (E) and membrane (M) proteins. 31 As commonly observed among flaviviruses, [31][32][33][34][35][36] the lipid envelope is slightly angular due to distortion by transmembrane domains of E and M proteins. ...
... [31][32][33][34][35] The virion comprises a nucleocapsid (NC), surrounded by a membrane composed of host-derived lipids with embedded viral envelope (E) and membrane (M) proteins. 31 As commonly observed among flaviviruses, [31][32][33][34][35][36] the lipid envelope is slightly angular due to distortion by transmembrane domains of E and M proteins. 31 Moreover, the TBEV virion surface is covered with small protrusions formed by glycans attached to E protein subunits. ...
... [31][32][33][34][35] The virion comprises a nucleocapsid (NC), surrounded by a membrane composed of host-derived lipids with embedded viral envelope (E) and membrane (M) proteins. 31 As commonly observed among flaviviruses, [31][32][33][34][35][36] the lipid envelope is slightly angular due to distortion by transmembrane domains of E and M proteins. 31 Moreover, the TBEV virion surface is covered with small protrusions formed by glycans attached to E protein subunits. ...
European and Asian countries. It is an emerging public health problem, with steadily increasing case numbers over recent decades. Tick-borne encephalitis virus affects between 10,000 and 15,000 patients annually. Infection occurs through the bite of an infected tick and, much less commonly, through infected milk consumption or aerosols. The TBEV genome comprises a positive-sense single-stranded RNA molecule of ∼11 kilobases. The open reading frame is > 10,000 bases long, flanked by untranslated regions (UTR), and encodes a polyprotein that is co- and post-transcriptionally processed into three structural and seven non-structural proteins. Tick-borne encephalitis virus infection results in encephalitis, often with a characteristic biphasic disease course. After a short incubation time, the viraemic phase is characterised by non-specific influenza-like symptoms. After an asymptomatic period of 2–7 days, more than half of patients show progression to a neurological phase, usually characterised by central and, rarely, peripheral nervous system symptoms. Mortality is low—around 1% of confirmed cases, depending on the viral subtype. After acute tick-borne encephalitis (TBE), a minority of patients experience long-term neurological deficits. Additionally, 40%–50% of patients develop a post-encephalitic syndrome, which significantly impairs daily activities and quality of life. Although TBEV has been described for several decades, no specific treatment exists. Much remains unknown regarding the objective assessment of long-lasting sequelae. Additional research is needed to better understand, prevent, and treat TBE. In this review, we aim to provide a comprehensive overview of the epidemiology, virology, and clinical picture of TBE.
... Flaviviruses undergo a maturation process during their production, giving rise to three distinct types of particles within infected cells: immature non-infectious particles, partially mature particles, and fully mature infectious particles [12][13][14]. Mature TBEV particles have a smooth, spherical morphology and are membrane-enveloped with a diameter of approximately 50 nm, similar to those of other Flaviviruses [12,[15][16][17][18]. The icosahedral nucleocapsid, which measures about 30 nm in diameter, consists of several copies of a single viral capsid protein (C) and genomic RNA [13]. ...
... Flaviviruses undergo a maturation process during their production, giving rise to three distinct types of particles within infected cells: immature non-infectious particles, partially mature particles, and fully mature infectious particles [12][13][14]. Mature TBEV particles have a smooth, spherical morphology and are membrane-enveloped with a diameter of approximately 50 nm, similar to those of other Flaviviruses [12,[15][16][17][18]. The icosahedral nucleocapsid, which measures about 30 nm in diameter, consists of several copies of a single viral capsid protein (C) and genomic RNA [13]. ...
... The envelope E protein creates rod-shaped dimers oriented parallel to the membrane, covering the surface of the viral particle. The mature TBEV particle envelope contains three E proteins and three M proteins in each icosahedral asymmetric unit [12]. The surface of the TBEV virion is adorned with small protrusions, which are created by glycans attached to the E protein subunits. ...
Tick-borne encephalitis virus (TBEV), a member of the Flaviviridae family, can cause serious infection of the central nervous system in humans, resulting in potential neurological complications and fatal outcomes. TBEV is primarily transmitted to humans through infected tick bites, and the viral agent circulates between ticks and animals, such as deer and small mammals. The occurrence of the infection aligns with the seasonal activity of ticks. As no specific antiviral therapy exists for TBEV infection, treatment approaches primarily focus on symptomatic relief and support. Active immunization is highly effective, especially for individuals in endemic areas. The burden of TBEV infections is increasing, posing a growing health concern. Reported incidence rates rose from 0.4 to 0.9 cases per 100,000 people between 2015 and 2020. The Baltic and Central European countries have the highest incidence, but TBE is endemic across a wide geographic area. Various factors, including social and environmental aspects, improved medical awareness, and advanced diagnostics, have contributed to the observed increase. Diagnosing TBEV infection can be challenging due to the non-specific nature of the initial symptoms and potential co-infections. Accurate diagnosis is crucial for appropriate management, prevention of complications, and effective control measures. In this comprehensive review, we summarize the molecular structure of TBEV, its transmission and circulation in natural environments, the pathogenesis of TBEV infection, the epidemiology and global distribution of the virus, associated risk factors, clinical manifestations, and diagnostic approaches. By improving understanding of these aspects, we aim to enhance knowledge and promote strategies for timely and accurate diagnosis, appropriate management, and the implementation of effective control measures against TBEV infections.
... Its genome is a single-stranded, positive-sense RNA with a length of approximately 11 kb nucleotides. The genome has one open reading frame (ORF) that encodes a single polyprotein which is co-and posttranslationally cleaved by cellular and viral proteases into three structural proteins, including core (C), precursor-M (prM), and envelope (E) proteins, and seven non-structural proteins, namely, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5 ( Fig. 1A) (Lindquist and Vapalahti, 2008;Füzik et al., 2018;Pulkkinen et al., 2018). Mature TBEV particles are approximately 50 nm in diameter and consist of a nucleocapsid surrounded by M and E proteins that are anchored within a lipid bilayer (Pulkkinen et al., 2018). ...
... The result of negative-stain TEM revealed that the VLPs were homogeneous spherical structures with a diameter of approximately 40-50 nm (Fig. 1E). Their morphological characteristics were similar to the wild type TBEV particles (Fig. 1E), which were consistent with previous study (Füzik et al., 2018;Pulkkinen et al., 2018). ...
... Another study used a bicistronic vector expressing the C/prM/E and NS2B/NS3 proteins of ZIKV to generate C/prM/E VLPs could induce a superior NAb response compared to only expressing prM/E VLPs, and the C-specific antibodies were detected in the immunized mice (Garg et al., 2019). Additionally, the TBE VLPs purified in our study exhibited homogeneous spherical structures with a diameter of approximately 40-50 nm, similar in size, morphology, and antigenic composition to wild type TBEV (Füzik et al., 2018). In contrast, recombinant TBEV subviral particles which only contained prM-E were observed about 30 nm in diameter (Liu et al., 2005). ...
Tick-borne encephalitis virus (TBEV) is an important tick-borne pathogen that poses as a serious public health concern. The coverage and immunogenicity of the currently available vaccines against TBEV are relatively low; therefore, it is crucial to develop novel and effective vaccines against TBEV. The present study describes a novel strategy for the assembly of virus-like particles (VLPs) by co-expressing the structural (Core/prM/E) and non-structural (NS2B/NS3Pro) proteins of TBEV. The efficacy of the VLPs was subsequently evaluated in C57BL/6 mice, and the resultant IgG serum could neutralize both Far-Eastern and European subtypes of TBEV. These findings indicated that the VLP-based vaccine elicited the production of cross-subtype reactive antibodies. The VLPs provided protection to mice lacking the type I interferon receptor (IFNAR-/-) against lethal TBEV challenge, with undetectable viral load in brain and intestinal tissues. Furthermore, the group that received the VLP vaccine did not exhibit significant pathological changes and the inflammatory factors were significantly suppressed compared to the control group. Immunization with the VLP vaccine induced the production of multiple-cytokine-producing antiviral CD4+ T cells in vivo, including TNF-α+, IL-2+, and IFN-γ+ T cells. Altogether, the findings suggest that noninfectious VLPs can serve as a potentially safe and effective vaccine candidate against diverse subtypes of TBEV.
... In the tertiary structure of glycoprotein E, this small loop is located near the fusion loop, a site in the DII domain, which is highly conserved among different flaviviruses and plays a key role in virus penetration into the host cells. It has been previously shown that flavivirus-neutralizing antibodies with ADE were fusion-loop-specific or were targeted against various epitopes on DII [27][28][29][30][31][32][33]. ...
... We assume that a probable mechanism of virus neutralization by mAb FVN-32 interferes with conformational changes in the viral envelope, preventing the insertion of the fusion loop into the endosome membrane during viral infection of the cell as a result of binding of the mAb FVN-32 to its epitope. A neutralization mechanism similar to that of FVN-32 was observed for Fab 19/1786 [28]. It is known that antibodies blocking the release of the fusion loop are able to neutralize the virus on the one hand, and cause ADE on the other. ...
Orthoflavivirus encephalitidis, formerly tick-borne encephalitis virus (TBEV), belongs to the Orthoflavivirus genus. TBEV is transmitted by tick bites and infection with TBEV can lead to serious disorders of the central nervous system. In this study, a new protective monoclonal mouse antibody (mAb) FVN-32, with high binding activity to glycoprotein E of TBEV, was selected and examined in post exposure prophylaxis in a mouse model of TBEV infection. BALB/c mice were injected mAb FVN-32 at doses of 200 μg, 50 μg, and 12.5 μg per mouse one day after a TBEV challenge. mAb FVN-32 showed 37.5% protective efficacy when administered at doses of 200 μg and 50 μg per mouse. The epitope for protective mAb FVN-32 was localized in TBEV glycoprotein E domain I+II, using a set of truncated fragments of glycoprotein E. Additionally, the target site recognized by mAb FVN-32 was defined using combinatorial libraries of peptides. Three-dimensional modeling revealed that the site is dspatially close to the fusion loop, but does not come into contact with it, and is localized in a region between 247 and 254 amino acid residues on the envelope protein. This region is conserved among TBEV-like orthoflaviviruses.
