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| 2. |
- da Silva, Diogo V., et al.
(författare)
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The Influenza Virus Neuraminidase Protein Transmembrane and Head Domains Have Coevolved
- 2015
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 89:2, s. 1094-1104
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Tidskriftsartikel (refereegranskat)abstract
- Transmembrane domains (TMDs) from single-spanning membrane proteins are commonly viewed as membrane anchors for functional domains. Influenza virus neuraminidase (NA) exemplifies this concept, as it retains enzymatic function upon proteolytic release from the membrane. However, the subtype 1 NA TMDs have become increasingly more polar in human strains since 1918, which suggests that selection pressure exists on this domain. Here, we investigated the N1 TMD-head domain relationship by exchanging a prototypical old TMD (1933) with a recent (2009), more polar TMD and an engineered hydrophobic TMD. Each exchange altered the TMD association, decreased the NA folding efficiency, and significantly reduced viral budding and replication at 37 degrees C compared to at 33 degrees C, at which NA folds more efficiently. Passaging the chimera viruses at 37 degrees C restored the NA folding efficiency, viral budding, and infectivity by selecting for NA TMD mutations that correspond with their polar or hydrophobic assembly properties. These results demonstrate that single-spanning membrane protein TMDs can influence distal domain folding, as well as membrane-related processes, and suggest the NA TMD in H1N1 viruses has become more polar to maintain compatibility with the evolving enzymatic head domain. IMPORTANCE The neuranainidase (NA) protein from influenza A viruses (IAVs) functions to promote viral release and is one of the major surface antigens. The receptor-destroying activity in NA resides in the distal head domain that is linked to the viral membrane by an N-terminal hydrophobic transmembrane domain (TMD). Over the last century, the subtype 1 NA TMDs (N1) in human H1N1 viruses have become increasingly more polar, and the head domains have changed to alter their antigenicity. Here, we provide the first evidence that an old N1 head domain from 1933 is incompatible with a recent (2009), more polar N1 TMD sequence and that, during viral replication, the head domain drives the selection of TMD mutations. These mutations modify the intrinsic TMD assembly to restore the head domain folding compatibility and the resultant budding deficiency. This likely explains why the N1 TMDs have become more polar and suggests the N1 TMD and head domain have coevolved.
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| 3. |
- Fusco, Salvatore, 1985
(författare)
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Unravelling the Role of the F55 Regulator in the Transition from Lysogeny to UV Induction of Sulfolobus Spindle-Shaped Virus 1
- 2015
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 89:12, s. 6453-6461
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACTSulfolobus spindle-shaped virus 1 represents a model for studying virus-host interaction in harsh environments, and it is so farthe only member of the family Fuselloviridae that shows a UV-inducible life cycle. Although the virus has been extensively studied,mechanisms underpinning the maintenance of lysogeny as well as those regulating the UV induction have received little attention.Recently, a novel SSV1 transcription factor, F55, was identified. This factor was able to bind in vitro to several sequencesderived from the early and UV-inducible promoters of the SSV1 genome. The location of these binding sites together with thedifferential affinity of F55 for these sequences led to the hypothesis that this protein might be involved in the maintenance of theSSV1 lysogeny. Here, we report an in vivo survey of the molecular events occurring at the UV-inducible region of the SSV1 genome,with a focus on the binding profile of F55 before and after the UV irradiation. The binding of F55 to the target promoterscorrelates with transcription repression, whereas its dissociation is paralleled by transcription activation. Therefore, we proposethat F55 acts as a molecular switch for the transcriptional regulation of the early viral genes.IMPORTANCEFunctional genomic studies of SSV1 proteins have been hindered by the lack of similarity with other characterized proteins. As aresult, few insights into their in vivo roles have been gained throughout the last 3 decades. Here, we report the first in vivo investigationof an SSV1 transcription regulator, F55, that plays a key role in the transition from the lysogenic to the induced state ofSSV1. We show that F55 regulates the expression of the UV-inducible as well as the early genes. Moreover, the differential affinityof this transcription factor for these targets allows a fine-tuned and temporal coordinated regulation of transcription of viralgenes.
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| 4. |
- Norberg, Peter, 1974, et al.
(författare)
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Recombination of Globally Circulating Varicella-Zoster Virus
- 2015
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Ingår i: Journal of Virology. - : American Society for Microbiology. - 0022-538X .- 1098-5514. ; 89:14, s. 7133-7146
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Tidskriftsartikel (refereegranskat)abstract
- Varicella-zoster virus (VZV) is a human herpesvirus, which during primary infection typically causes varicella (chicken pox) and establishes lifelong latency in sensory and autonomic ganglia. Later in life, the virus may reactivate to cause herpes zoster (HZ; also known as shingles). To prevent these diseases, a live-attenuated heterogeneous vaccine preparation, vOka, is used routinely in many countries worldwide. Recent studies of another alphaherpesvirus, infectious laryngotracheitis virus, demonstrate that live-attenuated vaccine strains can recombine in vivo, creating virulent progeny. These findings raised concerns about using attenuated herpesvirus vaccines under conditions that favor recombination. To investigate whether VZV may undergo recombination, which is a prerequisite for VZV vaccination to create such conditions, we here analyzed 115 complete VZV genomes. Our results demonstrate that recombination occurs frequently for VZV. It thus seems that VZV is fully capable of recombination if given the opportunity, which may have important implications for continued VZV vaccination. Although no interclade vaccine-wild-type recombinant strains were found, intraclade recombinants were frequently detected in clade 2, which harbors the vaccine strains, suggesting that the vaccine strains have already been involved in recombination events, either in vivo or in vitro during passages in cell culture. Finally, previous partial and complete genomic studies have described strains that do not cluster phylogenetically to any of the five established clades. The additional VZV strains sequenced here, in combination with those previously published, have enabled us to formally define a novel sixth VZV clade. Although genetic recombination has been demonstrated to frequently occur for other human alphaherpesviruses, herpes simplex viruses 1 and 2, only a few ancient and isolated recent recombination events have hitherto been demonstrated for VZV. In the present study, we demonstrate that VZV also frequently undergoes genetic recombination, including strains belonging to the clade containing the vOKA strain.
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| 5. |
- Rezelj, Veronica V, et al.
(författare)
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Generation of mutant Uukuniemi viruses lacking the nonstructural protein NSs by reverse genetics indicates that NSs is a weak interferon antagonist.
- 2015
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 89:9, s. 4849-4856
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Tidskriftsartikel (refereegranskat)abstract
- Uukuniemi virus (UUKV) is a tick-borne member of the Phlebovirus genus (family Bunyaviridae) and has been widely used as a safe laboratory model to study aspects of bunyavirus replication. Recently, a number of new tick-borne phleboviruses have been discovered, some of which, like severe fever with thrombocytopenia syndrome virus and Heartland virus, are highly pathogenic in man. UUKV could now serve as a useful comparator to understand the molecular basis for the different pathogenicities of these related viruses. We established a reverse genetics system to recover UUKV entirely from cDNA clones. We generated two recombinant viruses, one in which the nonstructural protein NSs open reading frame was deleted from the S segment and one in which the NSs gene was replaced with GFP, allowing convenient visualization of viral infection. We show that the UUKV NSs protein acts as a weak interferon antagonist in human cells, but it is unable to completely counteract the interferon response, which could serve as an explanation for its inability to cause disease in man.IMPORTANCE: Uukuniemi virus (UUKV) is a tick-borne phlebovirus that is apathogenic for man and has been used as a convenient model to investigate aspects of phlebovirus replication. Recently new tick-borne phleboviruses have emerged, such as severe fever with thrombocytopenia syndrome virus in China and Heartland virus in the US, that are highly pathogenic, and UUKV will now serve as a comparison to aid understanding of the molecular basis for the virulence of these new viruses. To help such investigations, we have developed a reverse genetics system for UUKV that permits manipulation of the viral genome. We generated viruses lacking the nonstructural protein NSs and show that UUKV NSs is a weak interferon antagonist. In addition, we created a virus that expresses GFP and thus allows convenient monitoring of virus replication. These new tools represent a significant advance in the study of tick-borne phleboviruses.
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| 6. |
- Shirinian, Margret, et al.
(författare)
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A Transgenic Drosophila melanogaster Model To Study Human T-Lymphotropic Virus Oncoprotein Tax-1-Driven Transformation In Vivo
- 2015
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 89:15, s. 8092-8095
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Tidskriftsartikel (refereegranskat)abstract
- Human T-cell lymphotropic virus type 1 (HTLV-1)-induced adult T-cell leukemia/lymphoma is an aggressive malignancy. HTLV-2 is genetically related to HTLV-1 but does not cause any malignant disease. HTLV-1 Tax transactivator (Tax-1) contributes to leukemogenesis via NF-kappa B. We describe transgenic Drosophila models expressing Tax in the compound eye and plasmatocytes. We demonstrate that Tax-1 but not Tax-2 induces ommatidial perturbation and increased plasmatocyte proliferation and that the eye phenotype is dependent on Kenny (IKK gamma/NEMO), thus validating this new in vivo model.
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| 7. |
- Verhagen, Josanne H., et al.
(författare)
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Long-Term Effect of Serial Infections with H13 and H16 Low-Pathogenic Avian Influenza Viruses in Black-Headed Gulls.
- 2015
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 89:22, s. 11507-11522
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Tidskriftsartikel (refereegranskat)abstract
- UNLABELLED: Infections of domestic and wild birds with low-pathogenic avian influenza viruses (LPAIVs) have been associated with protective immunity to subsequent infection. However, the degree and duration of immunity in wild birds from previous LPAIV infection, by the same or a different subtype, are poorly understood. Therefore, we inoculated H13N2 (A/black-headed gull/Netherlands/7/2009) and H16N3 (A/black-headed gull/Netherlands/26/2009) LPAIVs into black-headed gulls (Chroicocephalus ridibundus), their natural host species, and measured the long-term immune response and protection against one or two reinfections over a period of >1 year. This is the typical interval between LPAIV epizootics in wild birds. Reinfection with the same virus resulted in progressively less virus excretion, with complete abrogation of virus excretion after two infections for H13 but not H16. However, reinfection with the other virus affected neither the level nor duration of virus excretion. Virus excretion by immunologically naive birds did not differ in total levels of excreted H13 or H16 virus between first- and second-year birds, but the duration of H13 excretion was shorter for second-year birds. Furthermore, serum antibody levels did not correlate with protection against LPAIV infection. LPAIV-infected gulls showed no clinical signs of disease. These results imply that the epidemiological cycles of H13 and H16 in black-headed gulls are relatively independent from each other and depend mainly on infection of first-year birds.IMPORTANCE: Low-pathogenic avian influenza viruses (LPAIVs) circulate mainly in wild water birds but are occasionally transmitted to other species, including humans, where they cause subclinical to fatal disease. To date, the effect of LPAIV-specific immunity on the epidemiology of LPAIV in wild birds is poorly understood. In this study, we investigated the effect of H13 and H16 LPAIV infection in black-headed gulls on susceptibility and virus excretion of subsequent infection with the same or the other virus within the same breeding season and between breeding seasons. These are the only two LPAIV hemagglutinin subtypes predominating in this species. The findings suggest that H13 and H16 LPAIV cycles in black-headed gull populations are independent of each other, indicate the importance of first-year birds in LPAIV epidemiology, and emphasize the need for alternatives to avian influenza virus (AIV)-specific serum antibodies as evidence of past LPAIV infection and correlates of protection against LPAIV infection in wild birds.
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