| 1. |
- Lindqvist, Richard, et al.
(author)
-
Tick-Borne Flaviviruses and the Type I Interferon Response
- 2018
-
In: Viruses. - : MDPI. - 1999-4915. ; 10:7
-
Research review (peer-reviewed)abstract
- Flaviviruses are globally distributed pathogens causing millions of human infections every year. Flaviviruses are arthropod-borne viruses and are mainly transmitted by either ticks or mosquitoes. Mosquito-borne flaviviruses and their interactions with the innate immune response have been well-studied and reviewed extensively, thus this review will discuss tick-borne flaviviruses and their interactions with the host innate immune response.
|
|
| 2. |
- Panayiotou, Christakis, et al.
(author)
-
Viperin restricts Zika virus and tick-borne encephalitis virus replication by targeting NS3 for proteasomal degradation
- 2018
-
In: Journal of Virology. - : American Society for Microbiology. - 0022-538X .- 1098-5514. ; 92:7
-
Journal article (peer-reviewed)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.
|
|
| 3. |
|
|
| 4. |
- Upadhyay, Arunkumar, 1984-
(author)
-
Viperin, a multifunctional radical SAM enzyme : biogenesis and antiviral mechanisms
- 2016
-
Doctoral thesis (other academic/artistic)abstract
- Viperin (virus-inhibitory protein, endoplasmic reticulum-associated, interferon-inducible) is an interferon-induced antiviral protein. It has three distinct functional domains: the N-terminal domain, the radical SAM (S-adenosylmethionine) domain for binding iron-sulphur cluster, and the C-terminus domain. Viperin has a broad antiviral effect, and is also involved in the immune response signalling. However, the function and antiviral mechanism of viperin are still not well characterized. Thus the overall aim of the thesis was to investigate and better understand the function of viperin and its antiviral mechanism by identifying the cellular network of interaction partners. Affinity purification and mass spectrometry analysis were used to identify cellular proteins that interact with viperin.CIA1 (also known as CIAO1), a factor involved in loading of iron-sulphur (Fe/S) cluster was identified and confirmed to interact at the C-terminus of viperin. It was also seen that the C-terminal domain and the functional SAM domain of viperin was essential for loading the Fe/S cluster onto viperin. On a closer look at the biogenesis of viperin, we identified and confirmed viperin interaction with CIA2A, CIA2B, (also known as FAM96A and FAM96B respectively) and MMS19, which are other factors involved in the transfer of Fe/S clusters onto cytosolic Fe/S apo-proteins. Surprisingly, MMS19, which has been shown to act as an adapter protein for other Fe/S proteins, only interacted indirectly and was not required for transferring the Fe/S cluster. Similarly, the interaction of viperin with both the isoforms of CIA2 was interesting, but the role they play in viperin biogenesis and antiviral function is still not clear and requires further investigation.Study of the antiviral action of viperin against tick-borne encephalitis virus (TBEV) showed that the activity of the SAM domain is essential for the strong inhibition of genome replication of TBEV. Furthermore, viperin also affects the assembly and release of TBEV. Viperin interacts with GBF1 and downregulates its activity, thus preferentially inducing the secretion of viral capsid protein from the cell, and therefore disrupting the formation of infectious virus particles. The N-terminal domain of viperin is important for its effect on assembly and release.In summary, this work contributes to our general understanding of viperin biogenesis in the cell regarding the loading of Fe/S cluster onto viperin. It also addresses the importance of the different domains for its antiviral function against TBEV. Finally, mass spectrometry and viperin interactome analysis implicate many other interesting cellular pathways or processes that might give us a better understanding of viperin’s function and antiviral mechanism.
|
|
| 5. |
- Vonderstein, Kirstin, 1986-, et al.
(author)
-
Viperin targets flavivirus virulence by inducing assembly of non-infectious capsid particles
- 2018
-
In: Journal of Virology. - : American Society of Microbiology. - 0022-538X .- 1098-5514. ; 92:1
-
Journal article (peer-reviewed)abstract
- Efficient antiviral immunity requires interference with virus replication at multiple layers targeting diverse steps in the viral life cycle. Here we describe a novel flavivirus inhibition mechanism that results in interferon-mediated obstruction of tick-borne encephalitis virus particle assembly, and involves release of malfunctional membrane associated capsid (C) particles. This mechanism is controlled by the activity of the interferon-induced protein viperin, a broad spectrum antiviral interferon stimulated gene. Through analysis of the viperin-interactome, we identified the Golgi Brefeldin A resistant guanine nucleotide exchange factor 1 (GBF1), as the cellular protein targeted by viperin. Viperin-induced antiviral activity as well as C-particle release was stimulated by GBF1 inhibition and knock down, and reduced by elevated levels of GBF1. Our results suggest that viperin targets flavivirus virulence by inducing the secretion of unproductive non-infectious virus particles, by a GBF1-dependent mechanism. This yet undescribed antiviral mechanism allows potential therapeutic intervention.Importance The interferon response can target viral infection on almost every level, however, very little is known about interference of flavivirus assembly. Here we show that interferon, through the action of viperin, can disturb assembly of tick-borne encephalitis virus. The viperin protein is highly induced after viral infection and exhibit broad-spectrum antiviral activity. However, the mechanism of action is still elusive and appear to vary between the different viruses, indicating that cellular targets utilized by several viruses might be involved. In this study we show that viperin induce capsid particle release by interacting and inhibiting the function of the cellular protein Golgi Brefeldin A resistant guanine nucleotide exchange factor 1 (GBF1). GBF1 is a key protein in the cellular secretory pathway and essential in the life cycle of many viruses, also targeted by viperin, implicating GBF1 as a novel putative drug target.
|
|
