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- Asghar, Naveed, et al.
(author)
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Deep sequencing analysis of tick-borne encephalitis virus from questing ticks at natural foci reveals similarities between quasispecies pools of the virus
- 2017
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In: Journal of General Virology. - : The Microbiology Society. - 0022-1317 .- 1465-2099. ; 98:3, s. 413-421
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Journal article (peer-reviewed)abstract
- Every year, tick-borne encephalitis virus (TBEV) causes severe central nervous system infection in 10 000 to 15 000 people in Europe and Asia. TBEV is maintained in the environment by an enzootic cycle that requires a tick vector and a vertebrate host, and the adaptation of TBEV to vertebrate and invertebrate environments is essential for TBEV persistence in nature. This adaptation is facilitated by the error-prone nature of the virus's RNA-dependent RNA polymerase, which generates genetically distinct virus variants called quasispecies. TBEV shows a focal geographical distribution pattern where each focus represents a TBEV hotspot. Here, we sequenced and characterized two TBEV genomes, JP-296 and JP-554, from questing Ixodes ricinus ticks at a TBEV focus in central Sweden. Phylogenetic analysis showed geographical clustering among the newly sequenced strains and three previously sequenced Scandinavian strains, Toro-2003, Saringe-2009 and Mandal-2009, which originated from the same ancestor. Among these five Scandinavian TBEV strains, only Mandal-2009 showed a large deletion within the 3' non-coding region (NCR), similar to the highly virulent TBEV strain Hypr. Deep sequencing of JP-296, JP-554 and Mandal-2009 revealed significantly high quasispecies diversity for JP-296 and JP-554, with intact 3' NCRs, compared to the low diversity in Mandal-2009, with a truncated 3' NCR. Single-nucleotide polymorphism analysis showed that 40% of the single-nucleotide polymorphisms were common between quasispecies populations of JP-296 and JP-554, indicating a putative mechanism for how TBEV persists and is maintained within its natural foci.
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| 3. |
- Asghar, Naveed, 1983-, et al.
(author)
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Transient Expression of Flavivirus Structural Proteins in Nicotiana benthamiana
- 2022
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In: Vaccines. - : MDPI. - 2076-393X. ; 10:10
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Journal article (peer-reviewed)abstract
- Flaviviruses are a threat to public health and can cause major disease outbreaks. Tick-borne encephalitis (TBE) is caused by a flavivirus, and it is one of the most important causes of viral encephalitis in Europe and is on the rise in Sweden. As there is no antiviral treatment availa-ble, vaccination remains the best protective measure against TBE. Currently available TBE vaccines are based on formalin-inactivated virus produced in cell culture. These vaccines must be delivered by intramuscular injection, have a burdensome immunization schedule, and may exhibit vaccine failure in certain populations. This project aimed to develop an edible TBE vaccine to trigger a stronger immune response through oral delivery of viral antigens to mucosal surfaces. We demonstrated successful expression and post-translational processing of flavivirus structural pro-teins which then self-assembled to form virus-like particles in Nicotiana benthamiana. We performed oral toxicity tests in mice using various plant species as potential bioreactors and evaluated the immunogenicity of the resulting edible vaccine candidate. Mice immunized with the edible vaccine candidate did not survive challenge with TBE virus. Interestingly, immunization of female mice with a commercial TBE vaccine can protect their offspring against TBE virus infection.
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| 4. |
- Eliassen, Knut Eirik, et al.
(author)
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Tick-transmitted co-infections among erythema migrans patients in a general practice setting in Norway : a clinical and laboratory follow-up study
- 2021
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In: BMC Infectious Diseases. - : BMC. - 1471-2334. ; 21:1
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Journal article (peer-reviewed)abstract
- Background Erythema migrans (EM) is the most common manifestation of Lyme borreliosis. Here, we examined EM patients in Norwegian general practice to find the proportion exposed to tick-transmitted microorganisms other than Borrelia, and the impact of co-infection on the clinical manifestations and disease duration. Methods Skin biopsies from 139/188 EM patients were analyzed using PCR for Neoehrlichia mikurensis, Rickettsia spp., Anaplasma phagocytophilum and Babesia spp. Follow-up sera from 135/188 patients were analyzed for spotted fever group (SFG) Rickettsia, A. phagocytophilum and Babesia microti antibodies, and tested with PCR if positive. Day 0 sera from patients with fever (8/188) or EM duration of >= 21 days (69/188) were analyzed, using PCR, for A. phagocytophilum, Rickettsia spp., Babesia spp. and N. mikurensis. Day 14 sera were tested for TBEV IgG. Results We detected no microorganisms in the skin biopsies nor in the sera of patients with fever or prolonged EM duration. Serological signs of exposure against SFG Rickettsia and A. phagocytophilum were detected in 11/135 and 8/135, respectively. Three patients exhibited both SFG Rickettsia and A. phagocytophilum antibodies, albeit negative PCR. No antibodies were detected against B. microti. 2/187 had TBEV antibodies without prior immunization. There was no significant increase in clinical symptoms or disease duration in patients with possible co-infection. Conclusions Co-infection with N. mikurensis, A. phagocytophilum, SFG Rickettsia, Babesia spp. and TBEV is uncommon in Norwegian EM patients. Despite detecting antibodies against SFG Rickettsia and A. phagocytophilum in some patients, no clinical implications could be demonstrated.
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| 5. |
- Lindblom, Pontus, et al.
(author)
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Tick-borne encephalitis virus in ticks detached from humans and follow-up of serological and clinical response.
- 2014
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In: Ticks and Tick Borne Diseases. - Jena, Germany : Elsevier. - 1877-959X. ; 5:1, s. 21-28
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Journal article (peer-reviewed)abstract
- The risk of tick-borne encephalitis virus (TBEV) infection after a tick bite remains largely unknown. To address this, we investigated the presence of TBEV in ticks detached from humans in an attempt to relate viral copy number, TBEV subtype, and tick feeding time with the serological and clinical response of the tick-bitten participants. Ticks, blood samples, and questionnaires were collected from tick-bitten humans at 34 primary health care centers in Sweden and in the Aland Islands (Finland). A total of 2167 ticks was received from 1886 persons in 2008-2009. Using a multiplex quantitative real-time PCR, 5 TBEV-infected ticks were found (overall prevalence 0.23%, copy range <4 X 10(2)-7.7 X 10(6) per tick). One unvaccinated person bitten by a tick containing 7.7 x 10(6) TBEV copies experienced symptoms. Another unvaccinated person bitten by a tick containing 1.8 x 10(3) TBEV copies developed neither symptoms nor TBEV antibodies. The remaining 3 persons were protected by vaccination. In contrast, despite lack of TBEV in the detached ticks, 2 persons developed antibodies against TBEV, one of whom reported symptoms. Overall, a low risk of TBEV infection was observed, and too few persons got bitten by TBEV-infected ticks to draw certain conclusions regarding the clinical outcome in relation to the duration of the blood meal and virus copy number. However, this study indicates that an antibody response may develop without clinical symptoms, that a bite by an infected tick not always leads to an antibody response or clinical symptoms, and a possible correlation between virus load and tick feeding time. (C) 2013 Elsevier GmbH. All rights reserved.
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| 7. |
- Shakya, Ruchika, et al.
(author)
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Inkoo and Sindbis viruses in blood sucking insects, and a serological study for Inkoo virus in semi-domesticated Eurasian tundra reindeer in Norway
- 2022
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In: Virology Journal. - : Springer Nature. - 1743-422X. ; 19:1
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Journal article (peer-reviewed)abstract
- Background: Mosquito-borne viruses pose a serious threat to humans worldwide. There has been an upsurge in the number of mosquito-borne viruses in Europe, mostly belonging to the families Togaviridae, genus Alphavirus (Sindbis, Chikungunya), Flaviviridae (West Nile, Usutu, Dengue), and Peribunyaviridae, genus Orthobunyavirus, California serogroup (Inkoo, Batai, Tahyna). The principal focus of this study was Inkoo (INKV) and Sindbis (SINV) virus circulating in Norway, Sweden, Finland, and some parts of Russia. These viruses are associated with morbidity in humans. However, there is a knowledge gap regarding reservoirs and transmission. Therefore, we aimed to determine the prevalence of INKV and SINV in blood sucking insects and seroprevalence for INKV in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway. Materials and methods: In total, 213 pools containing about 25 blood sucking insects (BSI) each and 480 reindeer sera were collected in eight Norwegian reindeer summer pasture districts during 2013–2015. The pools were analysed by RT-PCR to detect INKV and by RT-real-time PCR for SINV. Reindeer sera were analysed for INKV-specific IgG by an Indirect Immunofluorescence Assay (n = 480, IIFA) and a Plaque Reduction Neutralization Test (n = 60, PRNT). Results: Aedes spp. were the most dominant species among the collected BSI. Two of the pools were positive for INKV-RNA by RT-PCR and were confirmed by pyrosequencing. The overall estimated pool prevalence (EPP) of INKV in Norway was 0.04%. None of the analysed pools were positive for SINV. Overall IgG seroprevalence in reindeer was 62% positive for INKV by IIFA. Of the 60 reindeer sera- analysed by PRNT for INKV, 80% were confirmed positive, and there was no cross-reactivity with the closely related Tahyna virus (TAHV) and Snowshoe hare virus (SSHV). Conclusion: The occurrence and prevalence of INKV in BSI and the high seroprevalence against the virus among semi-domesticated reindeer in Norway indicate that further studies are required for monitoring this virus. SINV was not detected in the BSI in this study, however, human cases of SINV infection are yearly reported from other regions such as Rjukan in south-central Norway. It is therefore essential to monitor both viruses in the human population. Our findings are important to raise awareness regarding the geographical distribution of these mosquito-borne viruses in Northern Europe.
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