| 1. |
- Kurhade, Chaitanya, 1989-, et al.
(författare)
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Correlation of Severity of Human Tick-Borne Encephalitis Virus Disease and Pathogenicity in Mice
- 2018
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Ingår i: Emerging Infectious Diseases. - : Centers for Disease control and Prevention. - 1080-6040 .- 1080-6059. ; 24:9, s. 1709-1712
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Tidskriftsartikel (refereegranskat)abstract
- We compared 2 tick-borne encephalitis virus strains isolated from 2 different foci that cause different symptoms in tick-borne encephalitis patients, from neurologic to mild gastrointestinal symptoms. We compared neuroinvasiveness, neurovirulence, and proinflammatory cytokine response in mice and found unique differences that contribute to our understanding of pathogenesis.
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| 2. |
- Kurhade, Chaitanya, 1989-
(författare)
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Interplay between tick-borne encephalitis virus and the host innate immunity
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flaviviruses are important emerging and re-emerging arthropod-borne pathogens that cause significant morbidity and mortality in humans. It consists of globally distributed human pathogens such as tick-borne encephalitis virus (TBEV), West Nile virus (WNV), Japanese encephalitis virus (JEV), yellow fever virus (YFV), dengue virus (DENV), and Zika virus (ZIKV). Depending on type, flaviviruses can cause a variety of symptoms ranging from haemorrhage to neurological disorders.Virus infection is detected by host pattern recognition receptors (PRRs), and through downstream signalling it leads to the production of interferons (IFNs). These IFNs then act in an autocrine or paracrine manner on the cells to induce various IFN-stimulated genes (ISGs), which have antiviral roles. However, the amount of IFN produced depends on the nature of the PRRs used by host cells to detect a particular virus. Although there are many PRRs present in the host cells, their relative contribution in different cell types and against a specific virus may vary. In the first study, we determined the importance of IPS-1 signalling in immunity and pathogenicity of tick-borne flaviviruses. This is an adaptor protein for cytoplasmic RIG-I-like receptors. Using IPS-1-deficient mice, we showed its importance against TBEV and Langat virus (LGTV) infection (the LGTV model virus belongs to the TBEV serogroup). Absence of IPS-1 leads to uncontrolled virus replication in the central nervous system (CNS), but it has only a minor role in shaping the humoral immune response at the periphery. LGTV-infected IPS-1-deficient mice showed apoptosis, activation of microglia and astrocytes, an elevated proinflammatory response, and recruitment of immune cells to the CNS. Interestingly, we also found that IFN-b upregulation after viral infection was dependent on IPS-1 in the olfactory bulb of the brain. Thus, our results suggest that local immune microenvironment of distinct brain regions is critical for determination of virus permissiveness.Interferons can upregulate several ISGs. Viperin is one such ISG that has a broad-spectrum antiviral action against many viruses. However, the importance of cell type and the significance of viperin in controlling many flavivirus infections in vivo is not known. Using viperin-deficient mice, we found that viperin was necessary for restriction of LGTV replication in the olfactory bulb and cerebrum, but not in the cerebellum. This finding was also confirmed with primary neurons derived from these brain regions. Furthermore, we could also show the particular importance of viperin in cortical neurons against TBEV, WNV, and ZIKV infection. The results suggested that a single ISG can shape the susceptibility and immune response to a flavivirus in different regions of the brain.Although viperin is such an important ISG against flaviviruses, the exact molecular mechanism of action is not known. To understand the mechanism, we performed co-immunoprecipitation screening to identify TBEV proteins that could interact with viperin. While viperin interacted with the prM, E, NS2A, NS2B, and NS3 proteins of TBEV, its interaction with NS3 led to its degradation through the proteosomal pathway. Furthermore, viperin could reduce the stability of other viperin-binding TBEV proteins in an NS3-dependent manner. We screened for viperin activity regarding interaction with NS3 proteins of other flaviviruses. Viperin interacted with NS3 of JEV, ZIKV, and YFV, but selectively degraded NS3 proteins of TBEV and ZIKV, and this activity correlated with its antiviral activity against these viruses.The last study was based on in vivo characterization of the newly isolated MucAr HB 171/11 strain of TBEV which caused unusual gastrointestinal and constitutional symptoms. This strain was compared with another strain, Torö-2003, of the same European subtype of TBEV but isolated from the different focus. Here we found unique differences in their neuroinvasiveness and neurovirulence, and in the immune response to these two strains.In summary, my work shed some light on the interplay between tick-borne flavivirus and the innate immune system. I have shown two examples of CNS region-specific differences in innate immune response regarding both in IFN induction pathways and antiviral effectors. Furthermore, we have investigated the in vivo pathogenesis of a strain of TBEV that caused unusual gastrointestinal and constitutional symptoms.
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| 3. |
- Panayiotou, Christakis, et al.
(författare)
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Viperin restricts Zika virus and tick-borne encephalitis virus replication by targeting NS3 for proteasomal degradation
- 2018
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Ingår i: Journal of Virology. - : American Society for Microbiology. - 0022-538X .- 1098-5514. ; 92:7
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Tidskriftsartikel (refereegranskat)abstract
- Flaviviruses are arthropod-borne viruses that constitute a major global health problem, with millions of human infections annually. Their pathogenesis ranges from mild illness to severe manifestations such as hemorrhagic fever and fatal encephalitis. Type I interferons (IFNs) are induced in response to viral infection and stimulate the expression of interferon-stimulated genes (ISGs), including that encoding viperin (virus-inhibitory protein, endoplasmic reticulum associated, IFN inducible), which shows antiviral activity against a broad spectrum of viruses, including several flaviviruses. Here we describe a novel antiviral mechanism employed by viperin against two prominent flaviviruses, tick-borne encephalitis virus (TBEV) and Zika virus (ZIKV). Viperin was found to interact and colocalize with the structural proteins premembrane (prM) and envelope (E) of TBEV, as well as with nonstructural (NS) proteins NS2A, NS2B, and NS3. Interestingly, viperin expression reduced the NS3 protein level, and the stability of the other interacting viral proteins, but only in the presence of NS3. We also found that although viperin interacted with NS3 of mosquito-borne flaviviruses (ZIKV, Japanese encephalitis virus, and yellow fever virus), only ZIKV was sensitive to the antiviral effect of viperin. This sensitivity correlated with viperin's ability to induce proteasome-dependent degradation of NS3. ZIKV and TBEV replication was rescued completely when NS3 was overexpressed, suggesting that the viral NS3 is the specific target of viperin. In summary, we present here a novel antiviral mechanism of viperin that is selective for specific viruses in the genus Flavivirus, affording the possible availability of new drug targets that can be used for therapeutic intervention.IMPORTANCE Flaviviruses are a group of enveloped RNA viruses that cause severe diseases in humans and animals worldwide, but no antiviral treatment is yet available. Viperin, a host protein produced in response to infection, effectively restricts the replication of several flaviviruses, but the exact molecular mechanisms have not been elucidated. Here we have identified a novel mechanism employed by viperin to inhibit the replication of two flaviviruses: tick-borne encephalitis virus (TBEV) and Zika virus (ZIKV). Viperin induced selective degradation via the proteasome of TBEV and ZIKV non-structural 3 (NS3) protein, which is involved in several steps of the viral life cycle. Furthermore, viperin also reduced the stability of several other viral proteins in a NS3-dependent manner, suggesting a central role of NS3 in viperin's antiflavivirus activity. Taking the results together, our work shows important similarities and differences among the members of the genus Flavivirus and could lead to the possibility of therapeutic intervention.
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| 4. |
- Reimer, Lasse, et al.
(författare)
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PKR kinase directly regulates tau expression and Alzheimer's disease-related tau phosphorylation
- 2021
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Ingår i: Brain Pathology. - : John Wiley & Sons. - 1015-6305 .- 1750-3639. ; 31:1, s. 103-119
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of extensively hyperphosphorylated tau in specific brain cells is a clear pathological hallmark in Alzheimer's disease and a number of other neurodegenerative disorders, collectively termed the tauopathies. Furthermore, hyperphosphorylation of tau prevents it from fulfilling its physiological role as a microtubule-stabilizing protein and leaves it increasingly vulnerable to self-assembly, suggestive of a central underlying role of hyperphosphorylation as a contributing factor in the etiology of these diseases. Viain vitrophosphorylation and regulation of kinase activity within cells and acute brain tissue, we reveal that the inflammation associated kinase, protein kinase R (PKR), directly phosphorylates numerous abnormal and disease-modifying residues within tau including Thr181, Ser199/202, Thr231, Ser262, Ser396, Ser404 and Ser409. Similar to disease processes, these PKR-mediated phosphorylations actively displace tau from microtubules in cells. In addition, PKR overexpression and knockdown, respectively, increase and decrease tau protein and mRNA levels in cells. This regulation occurs independent of noncoding transcriptional elements, suggesting an underlying mechanism involving intra-exonic regulation of the tau-encoding microtubule-associated protein tau (MAPT) gene. Finally, acute encephalopathy in wild type mice, induced by intracranial Langat virus infection, results in robust inflammation and PKR upregulation accompanied by abnormally phosphorylated full-length- and truncated tau. These findings indicate that PKR, independent of other kinases and upon acute brain inflammation, is capable of triggering pathological modulation of tau, which, in turn, might form the initial pathologic seed in several tauopathies such as Alzheimer's disease and Chronic traumatic encephalopathy where inflammation is severe.
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