Norbert Roos

• Mertes, Verena; Saragliadis, Athanasios; Mascherin, E; Tysvær, Ellen-Beate; Roos, Norbert & Linke, Dirk [Vis alle 7 forfattere av denne artikkelen] (2024). Recombinant expression of Yersinia ruckeri outer membrane proteins in Escherichia coli extracellular vesicles. Protein Expression and Purification. ISSN 1046-5928. 215. doi: 10.1016/j.pep.2023.106409. Fulltekst i vitenarkiv Vis sammendrag

  The secretion of extracellular vesicles (EVs) is a common process in Gram-negative bacteria and can be exploited for biotechnological applications. EVs pose a self-adjuvanting, non-replicative vaccine platform, where membrane and antigens are presented to the host immune system in a non-infectious fashion. The secreted quantity of EVs varies between Gram-negative bacterial species and is comparatively high in the model bacterium E. coli. The outer membrane proteins OmpA and OmpF of the fish pathogen Y. ruckeri have been proposed as vaccine candidates to prevent enteric redmouth disease in aquaculture. In this work, Y.ruckeri OmpA or OmpF were expressed in E. coli and recombinant EVs were isolated. To avoid competition between endogenous E. coli OmpA or OmpF, Y. ruckeri OmpA and OmpF were expressed in E. coli strains lacking ompA, ompF, and in a quadruple knockout strain where the four major outer membrane protein genes ompA, ompC, ompF and lamB were removed. Y.ruckeri OmpA and OmpF were successfully expressed in EVs derived from the E. coli mutants as verified by SDS-PAGE, heat modifiability and proteomic analysis using mass-spectrometry. Transmission electron microscopy revealed the presence of EVs in all E. coli strains, and increased EV concentrations were detected when expressing Y. ruckeri OmpA or OmpF in recombinant EVs compared to empty vector controls as verified by nanoparticle tracking analysis. These results show that E. coli can be utilized as a vector for production of EVs expressing outer membrane antigens from Y. ruckeri.

• Stephan, Mareike; Broeker, Nina; Saragliadis, Athanasios; Roos, Norbert; Linke, Dirk & Barbirz, Stefanie (2020). In vitro Analysis of O-Antigen-Specific Bacteriophage P22 Inactivation by Salmonella Outer Membrane Vesicles. Frontiers in Microbiology. 11. doi: 10.3389/fmicb.2020.510638. Fulltekst i vitenarkiv Vis sammendrag

  Bacteriophages use a large number of different bacterial cell envelope structures as receptors for surface attachment. As a consequence, bacterial surfaces represent a major control point for the defense against phage attack. One strategy for phage population control is the production of outer membrane vesicles (OMVs). In Gram-negative host bacteria, O-antigen-specific bacteriophages address lipopolysaccharide (LPS) to initiate infection, thus relying on an essential outer membrane glycan building block as receptor that is constantly present also in OMVs. In this work, we have analyzed interactions of Salmonella (S.) bacteriophage P22 with OMVs. For this, we isolated OMVs that were formed in large amounts during mechanical cell lysis of the P22 S. Typhimurium host. In vitro, these OMVs could efficiently reduce the number of infective phage particles. Fluorescence spectroscopy showed that upon interaction with OMVs, bacteriophage P22 released its DNA into the vesicle lumen. However, only about one third of the phage P22 particles actively ejected their genome. For the larger part, no genome release was observed, albeit the majority of phages in the system had lost infectivity towards their host. With OMVs, P22 ejected its DNA more rapidly and could release more DNA against elevated osmotic pressures compared to DNA release triggered with protein-free LPS aggregates. This emphasizes that OMV composition is a key feature for the regulation of infective bacteriophage particles in the system.

• Skottvoll, Frøydis Sved; Berg, Henriette Engen; Bjørseth, Kamilla; Lund, Kaja; Roos, Norbert & Bekhradnia, Sara [Vis alle 13 forfattere av denne artikkelen] (2018). Ultracentrifugation versus kit exosome isolation: nanoLC-MS and other tools reveal similar performance biomarkers, but also contaminations. Future science OA. 5(1). doi: 10.4155/fsoa-2018-0088. Fulltekst i vitenarkiv Vis sammendrag

  Aim: For isolation of exosomes, differential ultracentrifugation and an isolation kit from a major vendor were compared. Materials & methods: ‘Case study’ exosomes isolated from patient-derived cells from glioblastoma multiforme and a breast cancer cell line were analyzed. Results: Transmission electron microscopy, dynamic light scattering, western blotting, and so forth, revealed comparable performance. Potential protein biomarkers for both diseases were also identified in the isolates using nanoLC–MS. Western blotting and nanoLC–MS also revealed negative exosome markers regarding both isolation approaches. Conclusion: The two isolation methods had an overall similar performance, but we hesitate to use the term ‘exosome isolation’ as impurities may be present with both isolation methods. NanoLC–MS can detect disease biomarkers in exosomes and is useful for critical assessment of exosome enrichment procedures.

• Wessel, Øystein; Braaen, Stine; Alarcon, Marta; Haatveit, Hanne Merethe; Roos, Norbert & Markussen, Turhan [Vis alle 9 forfattere av denne artikkelen] (2017). Infection with purified Piscine orthoreovirus demonstrates a causal relationship with heart and skeletal muscle inflammation in Atlantic salmon. PLOS ONE. 12(8). doi: 10.1371/journal.pone.0183781. Fulltekst i vitenarkiv Vis sammendrag

  Viral diseases pose a significant threat to the productivity in aquaculture. Heart- and skeletal muscle inflammation (HSMI) is an emerging disease in Atlantic salmon (Salmo salar) farming. HSMI is associated with Piscine orthoreovirus (PRV) infection, but PRV is ubiquitous in farmed Atlantic salmon and thus present also in apparently healthy individuals. This has brought speculations if additional etiological factors are required, and experiments focusing on the causal relationship between PRV and HSMI are highly warranted. A major bottleneck in PRV research has been the lack of cell lines that allow propagation of the virus. To bypass this, we propagated PRV in salmon, bled the fish at the peak of the infection, and purified virus particles from blood cells. Electron microscopy, western blot and high-throughput sequencing all verified the purity of the viral particles. Purified PRV particles were inoculated into naïve Atlantic salmon. The purified virus replicated in inoculated fish, spread to naïve cohabitants, and induced histopathological changes consistent with HSMI. PRV specific staining was demonstrated in the pathological lesions. A dose-dependent response was observed; a high dose of virus gave earlier peak of the viral load and development of histopathological changes compared to a lower dose, but no difference in the severity of the disease. The experiment demonstrated that PRV can be purified from blood cells, and that PRV is the etiological agent of HSMI in Atlantic salmon.

• Nesset, Cecilie Kåsi; Kong, Xiang Yi; Damme, Markus; Schjalm, Camilla; Roos, Norbert & Løberg, Else Marit [Vis alle 7 forfattere av denne artikkelen] (2016). Age-dependent development of liver fibrosis in Glmp (gt/gt) mice. Fibrogenesis & Tissue Repair. 9(5). doi: 10.1186/s13069-016-0042-4. Fulltekst i vitenarkiv Vis sammendrag

  Background Mice lacking glycosylated lysosomal membrane protein (Glmp gt/gt mice) have liver fibrosis as the predominant phenotype due to chronic liver injury. The Glmp gt/gt mice grow and reproduce at the same rate as their wild-type siblings. Life expectancy is around 18 months. Methods Wild-type and Glmp gt/gt mice were studied between 1 week and 18 months of age. Livers were analyzed using histological, immunohistochemical, biochemical, and qPCR analyses. Results It was shown that Glmp gt/gt mice were not born with liver injury; however, it appeared shortly after birth as indicated by excess collagen expression, deposition of fibrous collagen in the periportal areas, and increased levels of hydroxyproline in Glmp gt/gt liver. Liver functional tests indicated a chronic, mild liver injury. Markers of inflammation, fibrosis, apoptosis, and modulation of extracellular matrix increased from an early age, peaking around 4 months of age and followed by attenuation of these signals. To compensate for loss of hepatocytes, the oval cell compartment was activated, with the highest activity of the oval cells detected at 3 months of age, suggesting insufficient hepatocyte proliferation in Glmp gt/gt mice around this age. Although constant proliferation of hepatocytes and oval cells maintained adequate hepatic function in Glmp gt/gt mice, it also resulted in a higher frequency of liver tumors in older animals. Conclusions The Glmp gt/gt mouse is proposed as a model for slowly progressing liver fibrosis and possibly as a model for a yet undescribed human lysosomal disorder.

• Høydahl, Lene Støkken; Nilssen, Nicolay Rustad; Gunnarsen, Kristin Støen; Pré, Marie Fleur du; Iversen, Rasmus & Roos, Norbert [Vis alle 11 forfattere av denne artikkelen] (2016). Multivalent pIX phage display selects for distinct and improved antibody properties. Scientific Reports. 6. doi: 10.1038/srep39066. Fulltekst i vitenarkiv Vis sammendrag

  Phage display screening readily allows for the identification of a multitude of antibody specificities, but to identify optimal lead candidates remains a challenge. Here, we direct the antibody-capsid fusion away from the signal sequence-dependent secretory SEC pathway in E. coli by utilizing the intrinsic signal sequence-independent property of pIX to obtain virion integration. This approach was combined with the use of an engineered helper phage known to improve antibody pIX display and retrieval. By direct comparison with pIII display, we demonstrate that antibody display using this pIX system translates into substantially improved retrieval of desired specificities with favorable biophysical properties in de novo selection. We show that the effect was due to less E. coli host toxicity during phage propagation conferred by the lack of a signal sequence. This pIX combinatorial display platform provides a generic alternative route for obtaining good binders with high stability and may thus find broad applicability.

• Tandberg, Julia Isabel; Rojas, Leidy Ximena Lagos; Langlete, Petter; Berger, Eva Kathrin; Rishovd, Anne-Lise & Roos, Norbert [Vis alle 9 forfattere av denne artikkelen] (2016). Comparative Analysis of Membrane Vesicles from Three Piscirickettsia salmonis Isolates Reveals Differences in Vesicle Characteristics. PLOS ONE. 11. doi: 10.1371/journal.pone.0165099. Fulltekst i vitenarkiv Vis sammendrag

  Membrane vesicles (MVs) are spherical particles naturally released from the membrane of Gram-negative bacteria. Bacterial MV production is associated with a range of phenotypes including biofilm formation, horizontal gene transfer, toxin delivery, modulation of host immune responses and virulence. This study reports comparative profiling of MVs from bacterial strains isolated from three widely disperse geographical areas. Mass spectrometry identified 119, 159 and 142 proteins in MVs from three different strains of Piscirickettsia salmonis isolated from salmonids in Chile (LF-89), Norway (NVI 5692) and Canada (NVI 5892), respectively. MV comparison revealed several strain-specific differences related to higher virulence capability for LF-89 MVs, both in vivo and in vitro, and stronger similarities between the NVI 5692 and NVI 5892 MV proteome. The MVs were similar in size and appearance as analyzed by electron microscopy and dynamic light scattering. The MVs from all three strains were internalized by both commercial and primary immune cell cultures, which suggest a potential role of the MVs in the bacterium’s utilization of leukocytes. When MVs were injected into an adult zebrafish infection model, an upregulation of several pro-inflammatory genes were observed in spleen and kidney, indicating a modulating effect on the immune system. The present study is the first comparative analysis of P. salmonis derived MVs, highlighting strain-specific vesicle characteristics. The results further illustrate that the MV proteome from one bacterial strain is not representative of all bacterial strains within one species.

• Iversen, Hildegunn; Lindbäck, Toril; L'Abee-Lund, Trine Marie; Roos, Norbert; Aspholm, Marina & Arnesen, Lotte Pia Stenfors (2015). The gut bacterium Bacteroides thetaiotaomicron influences the virulence potential of the enterohemorrhagic Escherichia coli0103:H25. PLOS ONE. 10(2), s. 1–23. doi: 10.1371/journal.pone.0118140. Fulltekst i vitenarkiv Vis sammendrag

  Enterohemorrhagic E. coli (EHEC) is associated with severe gastrointestinal disease. Upon entering the gastrointestinal tract, EHEC is exposed to a fluctuating environment and a myriad of other bacterial species. To establish an infection, EHEC strains have to modulate their gene expression according to the GI tract environment. In order to explore the interspecies interactions between EHEC and an human intestinal commensal, the global gene expression profile was determined of EHEC O103:H25 (EHEC NIPH-11060424) co-cultured with B. thetaiotaomicron (CCUG 10774) or grown in the presence of spent medium from B. thetaiotaomicron. Microarray analysis revealed that approximately 1% of the EHEC NIPH-11060424 genes were significantly up-regulated both in co-culture (30 genes) and in the presence of spent medium (44 genes), and that the affected genes differed between the two conditions. In co-culture, genes encoding structural components of the type three secretion system were among the most affected genes with an almost 4-fold up-regulation, while the most affected genes in spent medium were involved in chemotaxis and were more than 3-fold up-regulated. The operons for type three secretion system (TTSS) are located on the Locus of enterocyte effacement (LEE) pathogenicity island, and qPCR showed that genes of all five operons (LEE1-LEE5) were up-regulated. Moreover, an increased adherence to HeLa cells was observed in EHEC NIPH-11060424 exposed to B. thetaiotaomicron. Expression of stx2 genes, encoding the main virulence factor of EHEC, was down-regulated in both conditions (co-culture/spent medium). These results show that expression of EHEC genes involved in colonization and virulence is modulated in response to direct interspecies contact between cells, or to diffusible factors released from B. thetaiotaomicron. Such interspecies interactions could allow the pathogen to recognize its predilection site and modulate its behaviour accordingly, thus increasing the efficiency of colonization of the colon mucosa, facilitating its persistence and increasing its virulence potential.

• Brudal, Espen; Lampe, Elisabeth Opsjøn; Reubsaet, Leon; Roos, Norbert; Hegna, Ida Kristin & Thrane, Ida Marie [Vis alle 8 forfattere av denne artikkelen] (2015). Vaccination with outer membrane vesicles from Francisella noatunensis reduces development of francisellosis in a zebrafish model. Fish and Shellfish Immunology. ISSN 1050-4648. 42(1), s. 50–57. doi: 10.1016/j.fsi.2014.10.025. Fulltekst i vitenarkiv
• Pedersen, K.W.; Kierulf, B.; Oksvold, M.P.; Li, M.; Vlassov, A. & Roos, Norbert [Vis alle 8 forfattere av denne artikkelen] (2015). Direct Isolation of Exosomes from Cell Culture: Simplifying Methods for Exosome Enrichment and Analysis. Translational Biomedicine. 6(2:18), s. 1–9. Fulltekst i vitenarkiv
• Momtazi, Leva; Fam, Shahla Bagheri; Singh, Gurvinder; Hofgaard, Antje; Hakkarainen, Minna & Glomm, Wilhelm [Vis alle 10 forfattere av denne artikkelen] (2014). Synthesis, characterization, and cellular uptake of magnetic nanocarriers for cancer drug delivery. Journal of Colloid and Interface Science. ISSN 0021-9797. 433, s. 76–85. doi: 10.1016/j.jcis.2014.07.013. Fulltekst i vitenarkiv Vis sammendrag

  Hypothesis The absence of targetability is the primary inadequacy of conventional chemotherapy. Targeted drug delivery systems are conceptualized to overcome this challenge. We have designed a targetable magnetic nanocarrier consisting of a superparamagnetic iron oxide (SPIO) core and biocompatible and biodegradable poly(sebacic anhydride)-block-methyl ether poly(ethylene glycol) (PSA-mPEG) polymer shell. The idea is that this type of carriers should facilitate the targeting of cancer cells.

• Fenaroli, Federico; Westmoreland, David; Benjaminsen, Jørgen; Kolstad, Terje R Selnes; Skjeldal, Frode Miltzow & Meijer, Annemarie H. [Vis alle 12 forfattere av denne artikkelen] (2014). Nanoparticles as Drug Delivery System against Tuberculosis in Zebrafish Embryos: Direct Visualization and Treatment. ACS Nano. ISSN 1936-0851. 8(7), s. 7014–7026. doi: 10.1021/nn5019126. Fulltekst i vitenarkiv
• Vik, Åshild; Anonsen, Jan Haug; Aas, Finn Erik; Hegge, Finn Terje; Roos, Norbert & Koomey, Michael [Vis alle 7 forfattere av denne artikkelen] (2014). Type IV pilus assembly proficiency and dynamics influence pilin subunit phospho-form macro- and microheterogeneity in Neisseria gonorrhoeae. PLOS ONE. 9(5). doi: 10.1371/journal.pone.0096419. Fulltekst i vitenarkiv Vis sammendrag

  The PilE pilin subunit protein of the gonococcal Type IV pilus (Tfp) colonization factor undergoes multisite, covalent modification with the zwitterionic phospho-form modification phosphoethanolamine (PE). In a mutant lacking the pilin-like PilV protein however, PilE is modified with a mixture of PE and phosphocholine (PC). Moreover, intrastrain variation of PilE PC modification levels have been observed in backgrounds that constitutively express PptA (the protein phospho-form transferase A) required for both PE and PC modification. The molecular basis underlying phospho-form microheterogeneity in these instances remains poorly defined. Here, we examined the effects of mutations at numerous loci that disrupt or perturb Tfp assembly and observed that these mutants phenocopy the pilV mutant vis a vis phospho-form modification status. Thus, PC modification appears to be directly or indirectly responsive to the efficacy of pilin subunit interactions. Despite the complexity of contributing factors identified here, the data favor a model in which increased retention in the inner membrane may act as a key signal in altering phospho-form modification. These results also provide an alternative explanation for the variation in PilE PC levels observed previously and that has been assumed to be due to phase variation of pptA. Moreover, mass spectrometry revealed evidence for mono- and di-methylated forms of PE attached to PilE in mutants deficient in pilus assembly, directly implicating a methyltransferase-based pathway for PC synthesis in N. gonorrhoeae.

• Kong, Xiang Yi; Nesset, Cecilie Kåsi; Damme, Markus; Løberg, Else Marit; Lübke, Torben & Mæhlen, Jan [Vis alle 13 forfattere av denne artikkelen] (2014). Loss of lysosomal membrane protein NCU-G1 in mice results in spontaneous liver fibrosis with accumulation of lipofuscin and iron in Kupffer cells. Disease Models and Mechanisms. ISSN 1754-8403. 7(3), s. 351–362. doi: 10.1242/dmm.014050. Fulltekst i vitenarkiv Vis sammendrag

  Human kidney predominant protein, NCU-G1, is a highly conserved protein with an unknown biological function. Initially described as a nuclear protein, it was later shown to be a bona fide lysosomal integral membrane protein. To gain insight into the physiological function of NCU-G1, mice with no detectable expression of this gene were created using a gene-trap strategy, and Ncu-g1gt/gt mice were successfully characterized. Lysosomal disorders are mainly caused by lack of or malfunctioning of proteins in the endosomal-lysosomal pathway. The clinical symptoms vary, but often include liver dysfunction. Persistent liver damage activates fibrogenesis and, if unremedied, eventually leads to liver fibrosis/cirrhosis and death. We demonstrate that the disruption of Ncu-g1 results in spontaneous liver fibrosis in mice as the predominant phenotype. Evidence for an increased rate of hepatic cell death, oxidative stress and active fibrogenesis were detected in Ncu-g1gt/gt liver. In addition to collagen deposition, microscopic examination of liver sections revealed accumulation of autofluorescent lipofuscin and iron in Ncu-g1gt/gt Kupffer cells. Because only a few transgenic mouse models have been identified with chronic liver injury and spontaneous liver fibrosis development, we propose that the Ncu-g1gt/gt mouse could be a valuable new tool in the development of novel treatments for the attenuation of fibrosis due to chronic liver damage.

• Seidl, Sebastian; Braun, Ursula Barbara; Roos, Norbert; Shaohua, Li; Lüdtke, Timo H.-W. & Kispert, Andreas [Vis alle 7 forfattere av denne artikkelen] (2013). Phenotypical Analysis of Atypical PKCs In Vivo Function Display a Compensatory System at Mouse Embryonic Day 7.5. PLOS ONE. 8(5). doi: 10.1371/journal.pone.0062756. Fulltekst i vitenarkiv
• Santarella-Mellwig, Rachel; Pruggnaller, Sabine; Roos, Norbert; Mattaj, Ian W. & Devos, Damien P. (2013). Three-Dimensional Reconstruction of Bacteria with a Complex Endomembrane System. PLoS Biology. ISSN 1544-9173. 11(5), s. 1–9. doi: 10.1371/journal.pbio.1001565. Fulltekst i vitenarkiv
• Kalluru, Raja Sab; Fenaroli, Federico; Westmoreland, David; Ulanova, Lilia; Maleki, Atoosa & Roos, Norbert [Vis alle 15 forfattere av denne artikkelen] (2013). Polylactide-co-glycolide-rifampicin-nanoparticles efficiently clear Mycobacterium bovis BCG infection in macrophages and remain membrane-bound in phago-lysosomes. Journal of Cell Science. ISSN 0021-9533. 126(14), s. 3043–3054. doi: 10.1242/jcs.121814. Fulltekst i vitenarkiv
• Vik, Åshild; Aspholm, Marina; Anonsen, Jan Haug; Børud, Bente; Roos, Norbert & Koomey, Michael (2012). Insights into type IV pilus biogenesis and dynamics from genetic analysis of a C-terminally tagged pilin: a role for O-linked glycosylation. Molecular Microbiology. ISSN 0950-382X. 85(6), s. 1166–1178. doi: 10.1111/j.1365-2958.2012.08166.x. Fulltekst i vitenarkiv
• Nilssen, Nicolay Rustad; Frigstad, Terje; Pollmann, Sylvie; Roos, Norbert; Bogen, Bjarne & Sandlie, Inger [Vis alle 7 forfattere av denne artikkelen] (2012). DeltaPhage-a novel helper phage for high-valence pIX phagemid display. Nucleic Acids Research (NAR). ISSN 0305-1048. 40(16). doi: 10.1093/nar/gks341. Fulltekst i vitenarkiv Vis sammendrag

  Phage display has been instrumental in discovery of novel binding peptides and folded domains for the past two decades. We recently reported a novel pIX phagemid display system that is characterized by a strong preference for phagemid packaging combined with low display levels, two key features that support highly efficient affinity selection. However, high diversity in selected repertoires are intimately coupled to high display levels during initial selection rounds. To incorporate this additional feature into the pIX display system, we have developed a novel helper phage termed DeltaPhage that allows for high-valence display on pIX. This was obtained by inserting two amber mutations close to the pIX start codon, but after the pVII translational stop, conditionally inactivating the helper phage encoded pIX. Until now, the general notion has been that display on pIX is dependent on wild-type complementation, making high-valence display unachievable. However, we found that DeltaPhage does facilitate high-valence pIX display when used with a non-suppressor host. Here, we report a side-by-side comparison with pIII display, and we find that this novel helper phage complements existing pIX phagemid display systems to allow both low and high-valence display, making pIX display a complete and efficient alternative to existing pIII phagemid display systems.

• Farkas, Julia; Christian, Paul; Gallego-Urrea, Julián Alberto; Roos, Norbert; Hassellöv, Martin & Tollefsen, Knut-Erik [Vis alle 7 forfattere av denne artikkelen] (2011). Uptake and effects of manufactured silver nanoparticles in rainbow trout (Oncorhynchus mykiss) gill cells. Aquatic Toxicology. ISSN 0166-445X. 101(1), s. 117–125. doi: 10.1016/j.aquatox.2010.09.010. Fulltekst i vitenarkiv
• Løset, Geir Åge; Roos, Norbert; Bogen, Bjarne & Sandlie, Inger (2011). Expanding the Versatility of Phage Display II: Improved Affinity Selection of Folded Domains on Protein VII and IX of the Filamentous Phage. PLOS ONE. 6(2). doi: 10.1371/journal.pone.0017433. Fulltekst i vitenarkiv Vis sammendrag

  Background: Phage display is a leading technology for selection of binders with affinity for specific target molecules. Polypeptides are normally displayed as fusions to the major coat protein VIII (pVIII) or the minor coat protein III (pIII). Whereas pVIII display suffers from drawbacks such as heterogeneity in display levels and polypeptide fusion size limitations, toxicity and infection interference effects have been described for pIII display. Thus, display on other coat proteins such as pVII or pIX might be more attractive. Neither pVII nor pIX display have gained widespread use or been characterized in detail like pIII and pVIII display. Methodology/Principal Findings: Here we present a side-by-side comparison of display on pIII with display on pVII and pIX. Polypeptides of interest (POIs) are fused to pVII or pIX. The N-terminal periplasmic signal sequence, which is required for phage integration of pIII and pVIII and that has been added to pVII and pIX in earlier studies, is omitted altogether. Although the POI display level on pIII is higher than on pVII and pIX, affinity selection with pVII and pIX display libraries is shown to be particularly efficient. Conclusions/Significance: Display through pVII and/or pIX represent platforms with characteristics that differ from those of the pIII platform. We have explored this to increase the performance and expand the use of phage display. In the paper, we describe effective affinity selection of folded domains displayed on pVII or pIX. This makes both platforms more attractive alternatives to conventional pIII and pVIII display than they were before. © 2011 Wälchli et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

• Haugland, Øyvind; Mikalsen, Aase; Nilsen, Pål; Lindmo, Karine; Thu, Beate Julie & M., Trygve Eliassen [Vis alle 9 forfattere av denne artikkelen] (2011). Cardiomyopathy Syndrome of Atlantic Salmon (Salmo salar L.) Is Caused by a Double-Stranded RNA Virus of the Totiviridae Family. Journal of Virology. ISSN 0022-538X. 85(11), s. 5275–5286. doi: 10.1128/JVI.02154-10. Fulltekst i vitenarkiv
• Farkas, Julia; Christian, Paul; Urrea, Julian Alberto Gallego; Roos, Norbert; Hassellöv, Martin & Tollefsen, Knut-Erik [Vis alle 7 forfattere av denne artikkelen] (2010). Effects of silver and gold nanoparticles on rainbow trout (Oncorhynchus mykiss) hepatocytes. Aquatic Toxicology. ISSN 0166-445X. 96(1), s. 44–52. doi: 10.1016/j.aquatox.2009.09.016. Fulltekst i vitenarkiv
• Schiøtz, Berit Lyng; Roos, Norbert; Rishovd, Anne-Lise & Gjøen, Tor (2010). Formation of autophagosomes and redistribution of LC3 upon in vitro infection with infectious salmon anemia virus. Virus Research. ISSN 0168-1702. 151(1), s. 104–107. doi: 10.1016/j.virusres.2010.03.013. Fulltekst i vitenarkiv
• Salomonsson, Emelie; Forsberg, A; Roos, Norbert; Holz, C; Maier, B & Koomey, Michael [Vis alle 7 forfattere av denne artikkelen] (2009). Functional analyses of pilin-like proteins from Francisella tularensis: complementation of type IV pilus phenotypes in Neisseria gonorrhoeae. Microbiology (Reading). ISSN 1350-0872. 155, s. 2546–2559. doi: 10.1099/mic.0.028183-0. Fulltekst i vitenarkiv
• Posthuma, CC; Pedersen, Ketil Winther; Lu, Z; Joosten, RG; Roos, Norbert & Zevenhoven-Dobbe, JC [Vis alle 7 forfattere av denne artikkelen] (2008). Formation of the arterivirus replication/transcription complex: a key role for nonstructural protein 3 in the remodeling of intracellular membranes. Journal of Virology. ISSN 0022-538X. 82, s. 4480–4491. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Wolfgang, Matthew; Putten, JPM van; Roos, Norbert; Aas, Finn Erik & Jacobsen, Wolfgang Mathias [Vis alle 8 forfattere av denne artikkelen] (2007). Pseudomonas aeruginosa type IV pilus expression in Neisseria gonorrhoeae: Effects of pilin subunit composition on function and organelle dynamics. Journal of Bacteriology. ISSN 0021-9193. 189(18), s. 6676–6685. doi: 10.1128/JB.00407-07. Fulltekst i vitenarkiv
• Sporstol, Marita; Mousavi, Darbi Seyed Ali; Eskild, Winnie; Roos, Norbert & Berg, Trond (2007). ABCAI, ABCGI and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines. BMC Molecular Biology. 8. doi: 10.1186/1471-2199-8-5. Fulltekst i vitenarkiv Vis sammendrag

  Background Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism. Results By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines. Conclusion Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR.

• Aas, Finn Erik; Winther-Larsen, Hanne C; Wolfgang, Matthew; Frye, Stephan; Løvold, Cecilia & Roos, Norbert [Vis alle 8 forfattere av denne artikkelen] (2007). Substitutions in the N-terminal alpha helical spine of Neisseria gonorrhoeae pilin affect type IV pilus assembly, dynamics and associated functions. Molecular Microbiology. ISSN 0950-382X. 63, s. 69–85. doi: 10.1111/j.1365-2958.2006.05482.x. Fulltekst i vitenarkiv
• Aas, Finn Erik; Winther-Larsen, Hanne C; Wolfgang, Matthew; Frye, Stephan Alfons; Løvold, Cecilia & Roos, Norbert [Vis alle 8 forfattere av denne artikkelen] (2006). Substitutions in the N-terminal alpha helical spine of Neisseria gonorrhoeae pilin affects Type IV pilus assembly, dynamics and associated functions. Molecular Microbiology. ISSN 0950-382X. 63(1), s. 69–85. Fulltekst i vitenarkiv
• Roos, Norbert; Webster, Paul & Griffiths, Gareth Wyn (2006). Use of ultrathin cryo- and plastic sections for immunocytochemistry. I Celis, Julio E. (Red.), Cell biology. A laboratory handbook. 3rd ed. Elsevier. ISSN 9780121647339. s. 299–305. Fulltekst i vitenarkiv
• Malerød, Lene; Sporstol, Marita; Juvet, Lene Kristine; Mousavi, Darbi Seyed Ali; Gjøen, Tor & Berg, Trond [Vis alle 8 forfattere av denne artikkelen] (2005). Bile acids reduce SR-BI expression in hepatocytes by a pathway involving FXR/RXR, SHP, and LRH-1. Biochemical and Biophysical Research Communications - BBRC. ISSN 0006-291X. 336(4), s. 1096–1105. Fulltekst i vitenarkiv
• Senoo, Haruki; Wake, Kenjiro; Wold, Heidi Libæk; Higashi, Nobuyo; Imai, Katsuyuki & Moskaug, Jan Øivind [Vis alle 14 forfattere av denne artikkelen] (2004). Decreased Capacity for Vitamin A Storage in Hepatic Stellate Cells for Arctic Animals. Comparative Hepatology. 3(1), s. 18–18. Fulltekst i vitenarkiv
• Higashi, Nobuyo; Imai, Katsuyuki; Sato, Mitsuru; Sato, Takeya; Kojima, Naosuke & Miura, Mitsutaka [Vis alle 14 forfattere av denne artikkelen] (2004). Intralobular Distribution of Vitamin A-Storing Lipid Droplets in Hepatic Stellate Cells with Special Reference to Polar Bear and Arctic Fox. Comparative Hepatology. 3(1). Fulltekst i vitenarkiv
• Berg, Trond; Norum, Kaare Reidar; Roos, Norbert & Blomhoff, Rune (2004). Intralobular distribution of vitamin A-storing lipid droplets in hepatic stellate cells. Special reference to polar bear and arctic fox. Comparative Hepatology. 3, s. 16–16. Fulltekst i vitenarkiv
• Kindberg, Grete M.; Tolleshaug, Helge; Roos, Norbert & Skotland, Tore (2003). Hepatic clearance of Sanazoid perflourobutane microbubbles by Kupffer cells does not reduce the ability of the liver to phagocytose or degrade albumin microspheres. Cell and Tissue Research. ISSN 0302-766X. 312, s. 49–54. Fulltekst i vitenarkiv
• Mallardo, Massimo; Leithe, Edward; Schleich, Sybille; Roos, Norbert; Doglio, Laura & Locker, Jacomine Krijnse (2002). Relationship between Vaccinia virus intracellular cores, early mRNAs, and DNA replication sites. Journal of Virology. ISSN 0022-538X. 76(10), s. 5167–5183. Fulltekst i vitenarkiv
• Doglio, Laura; Marco, Ario de; Schleich, Sybille; Roos, Norbert & Locker, Jacomine Krijnse (2002). The Vaccinia virus E8R gene product: a viral membrane protein that is made early in infection and packaged into the virions´core. Journal of Virology. ISSN 0022-538X. 76(19), s. 9773–9786. Fulltekst i vitenarkiv
• Snijder, Eric J.; Tool, Hans van; Roos, Norbert & Pedersen, Ketil Winther (2001). Non-structural proteins 2 and 3 interact to modify host cell membranes during the formation of the arterivirus replication complex. Journal of General Virology. ISSN 0022-1317. 82, s. 985–994. Fulltekst i vitenarkiv
• Sato, Mitsuru; Miura, Mitsutaka; Kojima, Naosuke; Higashi, Nobyuo; Imamura, Kazuyuki & Sato, Takeya [Vis alle 14 forfattere av denne artikkelen] (2001). Nuclear deviation in hepatic parenchymal cells on sinusoidal surfaces in artcic animals. Cell structure and function. ISSN 0386-7196. 26, s. 71–77. Fulltekst i vitenarkiv
• Senoo, Haruki; Imamura, Kazuyuki; Higashi, Nobyuo; Wake, Kenjiro; Nojima, N. & Miura, Mitsutaka [Vis alle 13 forfattere av denne artikkelen] (2001). Transport and hepatic storage of vitamin A in arctic animals. I Wisse, E; Knook, D.L.; Zanger, R De & Arthur, K. (Red.), Cells of the hepatic sinusoid. Kupffer Cell Foundation, Leiden, The Netherlands. s. 207–209. Fulltekst i vitenarkiv
• Griffiths, Gareth O.; Wepf, Roger; Wendt, Thomas; Krijnse-Locker, Jacomine; Cyrklaff, Marek & Roos, Norbert (2001). Structure and Assembly of Intracellular Mature Vaccinia Virus: Isolated-Particle Analysis. Journal of Virology. ISSN 0022-538X. 75(22), s. 11034–11055. Fulltekst i vitenarkiv
• Griffiths, Gareth O.; Roos, Norbert; Schleich, Sybille & Krijnse-Locker, Jacomine (2001). Structure and Assembly of Intracellular Mature Vaccinia Virus: Thin-Section Analysis. Journal of Virology. ISSN 0022-538X. 75(22), s. 11056–11070. Fulltekst i vitenarkiv
• Oksvold, Morten Pedersen; Skarpen, Ellen; Lindeman, Birgitte; Roos, Norbert & Huitfeldt, Henrik (2000). Immunocytochemical localization of She and activated EGF receptor in early endosomes after EGF stimulation of HeLa cells. Journal of Histochemistry and Cytochemistry. ISSN 0022-1554. 48(1), s. 21–33. Fulltekst i vitenarkiv
• Pedersen, Ketil Winther; Snijder, Eric J.; Schleich, Sybille; Roos, Norbert; Griffiths, Gareth O. & Locker, Jacomine Krijnse (2000). Characterization of vaccinia virus intracellular cores: implications for viral uncoating and core structure. Journal of Virology. ISSN 0022-538X. 74(8), s. 3525–3536. Fulltekst i vitenarkiv Vis sammendrag

  The entry of vaccinia virus (VV) into the host cell results in the delivery of the double-stranded DNA genome-containing core into the cytoplasm. The core is disassembled, releasing the viral DNA in order to initiate VV cytoplasmic transcription and DNA replication. Core disassembly can be prevented using the VV early transcription inhibitor actinomycin D (actD), since early VV protein synthesis is required for core uncoating. In this study, VV intracellular cores were accumulated in the presence of actD and isolated from infected cells. The content of these cores was analyzed by negative staining EM and by Western blotting using a collection of antibodies to VV core and membrane proteins. By Western blot analyses, intracellular actD cores, as well as cores prepared by NP-40-dithiothreitol treatment of purified virions (NP-40/DTT cores), contained the core proteins p25 (encoded by L4R), 4a (A10L), 4b (A3L), and p39 (A4L) as well as small amounts of the VV membrane proteins p32 (D8L) and p35 (H3L). While NP-40/DTT cores contained the major putative DNA-binding protein p11 (F17R), actD cores entirely lacked this protein. Labeled cryosections of cells infected for different periods of time in the presence or absence of actD were subsequently used to follow the fate of VV core proteins by EM. These EM images confirmed that p11 was lost at the plasma membrane upon core penetration. The cores that accumulated in the presence of actD were labeled with antibodies to 4a, p39, p25, and DNA at all times examined. In the absence of the drug the cores gradually lost their electron-dense inner part, concomitant with the loss of p25 and DNA labeling. The remaining core shell still labeled with antibodies to p39 and 4a/4b, implying that these proteins are part of this structure. These combined data are discussed with respect to the structure of VV as well as core disassembly.

• Hammarstedt, Maria; Wallengren, Kristina; Pedersen, Ketil Winther; Roos, Norbert & Garoff, Henrik (2000). Minimal exclusion of plasma membrane proteins during retroviral envelope formation. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 97(13), s. 7527–7532. Fulltekst i vitenarkiv
• Senoo, H; Imai, K; Wake, K; Wold, Heidi Libæk; Moskaug, Jan Øivind & Kojima, N [Vis alle 14 forfattere av denne artikkelen] (1999). Vitamin A-storing system in mammals and birds in arctic area: a study in the Svalbard archipelego. I Wisse, E; Knook, D.L.; Zanger, R de & Fraser, R (Red.), Cells of the hepatic sinusoid. Kupffer Cell Foundation. ISSN 9789080385627. s. 34–35. Fulltekst i vitenarkiv
• Pedersen, Ketil Winther; Meer, Y. van der; Roos, Norbert & Snijder, Eric J. (1999). Open reading frame 1a-encoded subunits of the arterivirus replicase induce endoplasmic reticulum-derived double-membrane vesicles which carry the viral replication complex. Journal of Virology. ISSN 0022-538X. s. 2016–2026. Fulltekst i vitenarkiv Vis sammendrag

  The replicase of equine arteritis virus (EAV; family Arteriviridae, order Nidovirales) is expressed in the form of two polyproteins (the open reading frame 1a [ORF1a] and ORF1ab proteins). Three viral proteases cleave these precursors into 12 nonstructural proteins, which direct both genome replication and subgenomic mRNA transcription. Immunofluorescence assays showed that most EAV replicase subunits localize to membranes in the perinuclear region of the infected cell. Using replicase-specific antibodies and cryoimmunoelectron microscopy, unusual double-membrane vesicles (DMVs) were identified as the probable site of EAV RNA synthesis. These DMVs were previously observed in cells infected with different arteriviruses but were never implicated in viral RNA synthesis. Extensive electron microscopic analysis showed that they appear to be derived from paired endoplasmic reticulum membranes and that they are most likely formed by protrusion and detachment of vesicular structures with a double membrane. Interestingly, very similar membrane rearrangements were observed upon expression of ORF1a-encoded replicase subunits nsp2 to nsp7 from an alphavirus-based expression vector. Apparently, the formation of a membrane-bound scaffold for the replication complex is a distinct step in the arterivirus life cycle, which is directed by the ORF1a protein and does not depend on other viral proteins and/or EAV-specific RNA synthesis.

• Roos, Norbert & Griffiths, Gareth Wyn (1998). Use of ultrathin cryo-and plastic sections for immunoelectron microscopy. I Celis, Julio E. (Red.), Cell Biology: A Laboratory Handbook. Academic Press. ISSN 9780121647285. s. 332–339. Fulltekst i vitenarkiv
• Brech, Andreas; Kjeken, Rune; Emblemsvåg, Marianne Synnes; Berg, Trond; Roos, Norbert & Prydz, Kristian (1998). Endocytosed ricin and asialoorosomucoid follow different intracellular pathways in hepatocytes. Biochimica et Biophysica Acta. ISSN 0006-3002. 1373(1), s. 195–208. Fulltekst i vitenarkiv Vis sammendrag

  Earlier studies have suggested that fluid phase endocytosis in rat hepatocytes takes place via a clathrin-independent mechanism [1,2]. This observation suggests that a relatively large amount of plasma membrane outside coated pits may be involved in hepatic endocytosis. Ricin, which binds to galactose residues on glycoproteins and glycolipids, has, in this report, been used as a general marker for the plasma membrane of hepatocytes. The endocytosis of ricin was compared with that of asialoorosomucoid (AOM) which is taken up exclusively via clathrin-coated pits. Hypertonic medium has been shown to inhibit uptake via coated pits more effectively than clathrin-independent uptake [3-5]. It was found, in this study, that the addition of 100 mM sucrose to the incubation medium inhibited the uptake of 125I-tyramine- cellobiose-asialoorosomucoid (125I-TC-AOM) more extensively than that of 125I-tyramine-cellobiose-ricin (125I-TC-ricin), compatible with the notion that the two probes are internalised via different mechanisms. Subcellular fractionation experiments indicated that 125I-TC-ricin entered a denser endocytic organelle than that receiving 125I-TC-AOM. To determine whether the separation of the two probes was due to a different transport kinetics (i.e. that 125I-TC-ricin is transported more rapidly to a later, denser compartment than 125I-TC-AOM) the cells were incubated at 18 degreesC to allow a slower internalisation/transport of the labelled probes. The results obtained showed, again, that the early endosomes containing 125I-TC-ricin were significantly denser than those containing 125I-TC-AOM. We also employed the horseradish peroxidase (HRP)-diaminobenzidine (DAB) density shift technique of Courtoy et al. [6] to determine whether 125I- TC-ricin and 125I-TC-AOM were in separate endosomes early after their uptake. The results showed that early endosomes containing 125I-TC-AOM were density shifted whereas those containing 125I-TC-ricin were unaffected by the density shift procedure. The use of probes labelled with 125I-TC allowed us to identify compartments involved in the degradation of 125I-TC-AOM and 125I-TC-ricin, by measuring acid soluble radioactivities in the gradient fractions. It was found that 125I-TC- ricin was degraded mainly in endosomes, whereas 125I-TC-AOM, as expected, was degraded mainly in lysosomes.

• Nagy, Nina; Holven, Kirsten B.; Roos, Norbert; Senoo, Haruki; Kojima, Naosuke & Norum, Kaare Reidar [Vis alle 7 forfattere av denne artikkelen] (1997). Storage of vitmain A in extrahepatic stellate cells in normal rats. Journal of Lipid Research. ISSN 0022-2275. 38, s. 645–658. Fulltekst i vitenarkiv
• Nagy, Nina Elisabeth; Holven, Kirsten Bjørklund; Roos, Norbert; Senoo, Haruki; Kojima, Naosuke & Norum, Kaare Reidar [Vis alle 7 forfattere av denne artikkelen] (1997). Storage of vitamin A in extrahepatic stellate cells in normal rats. Journal of Lipid Research. ISSN 0022-2275. 38, s. 645–658. Fulltekst i vitenarkiv
• Brech, Andreas; Løvdahl, T; Kjekken, Rune; Roos, Norbert & Berg, Trond (1996). Density shift of endocytic vesicles induced by uptake of colloidal gold particles in rat hepatocytes. Zeitschrift für Gastroenterologie - German Journal of Gastroenterology. ISSN 0044-2771. 34, s. 79–80. Fulltekst i vitenarkiv
• Roos, Norbert; Cyrklaff, Marek; Cudmore, Sally; Blasco, Rafael; Krijnse-Locker, Jacomine & Griffiths, Gareth Wyn (1996). A novel immunogold cryoelectron microscopic approach to investigate the structure of the intracellular and extracellular forms of vaccinia virus. EMBO Journal. ISSN 0261-4189. 15(10), s. 2343–2355. Fulltekst i vitenarkiv
• Kjekken, Rune; Brech, Andreas; Løvdal, Torunn; Roos, Norbert & Berg, Trond (1995). Involvement of early amd late lysosomes in the degradation of mannosylated ligands by rat liver endothelial cells. Experimental Cell Research. ISSN 0014-4827. 216, s. 290–298. Fulltekst i vitenarkiv
• Holen, Ingunn; Gordon, Paul B.; Strømhaug, Per E.; Berg, Trond Olav; Fengsrud, Monica & Brech, Andreas [Vis alle 9 forfattere av denne artikkelen] (1995). Inhibition of asialoglycoprotein endocytosis and degradation in rat hepatocytes by protein phosphatase inhibitors. Biochemical Journal. ISSN 0264-6021. 311, s. 317–326. Fulltekst i vitenarkiv
• Fengsrud, Monica; Roos, Norbert; Berg, Trond; Liou, Willisa; Slot, Jan W & Seglen, Per O. (1995). Ultrastructural and immunocytochemical characterization of autophagic vacoules in isolated hepatocytes: Effects of vinblastine and asparagine on vacoule distributions. Experimental Cell Research. ISSN 0014-4827. 221, s. 504–519. Fulltekst i vitenarkiv
• Roos, Norbert & Griffiths, Gareth Wyn (1994). Use of ultrathin cryo-and plastic sections for immunoelectron microscopy. I Celis, Julio E. (Red.), Cell Biology: A Laboratory Handbook. Academic Press. ISSN 9780121647162. s. 168–176. Fulltekst i vitenarkiv
• Brorson, Sverre Henning; Roos, Norbert & Skjørten, Fredrik (1994). Antibody penetration into LR-white sections. Micron. ISSN 0968-4328. 25(5), s. 453–460. Fulltekst i vitenarkiv
• Cyrklaff, Marek; Roos, Norbert; Gross, H & Dubochet, Jacque (1994). Particle-surface interaction in thin vitrified films for cryo-electron microscopy. Journal of Microscopy. ISSN 0022-2720. 175, s. 135–142. Fulltekst i vitenarkiv
• Ørvim, Una; Roald, Helge Einar; Stephens, Roos W; Roos, Norbert & Sakariassen, Kjell S. (1994). Tissue factor-induced coagulation triggers platelet thrombus formation as efficiently as fibrillar collagen at arterial blood flow conditions. Arteriosclerosis and thrombosis. ISSN 1049-8834. 14, s. 1976–1983. Fulltekst i vitenarkiv
• Senoo, H; Smeland, Sigbjørn; Stang, Espen; Roos, Norbert; Berg, Trond & Norum, Kaare [Vis alle 7 forfattere av denne artikkelen] (1993). Stellate cells take up retinol-binding protein. I Knook, D.L. & Wisse, E (Red.), Cells of the hepatic sinusoid. The Kupffer Cell Foundation. ISSN 9789080007956. s. 423–425. Fulltekst i vitenarkiv
• Gudmundsen, Ola; Roos, Norbert; Berg, Trond & Nenseter, Marit Sofie (1993). The role of nonparenchymal liver cells in the uptake of plasma LDL and beta-VLDL in cholesterol-fed rabbits. I Knook, D.L. & Wisse, E (Red.), Cells of the hepatic sinusoid. The Kupffer Cell Foundation. ISSN 9789080007956. s. 461–464. Fulltekst i vitenarkiv
• Berg, Trond; Brech, Andreas; Kjeken, Rune & Roos, Norbert (1993). Prelysosomal degradation in rat liver endothelial cells. I Knook, D.L. & Wisse, E (Red.), Cells of the hepatic sinusoid. The Kupffer Cell Foundation. ISSN 9789080007956. s. 426–430. Fulltekst i vitenarkiv
• Brech, Andreas; Magnusson, Sigurdur; Stang, Espen; Berg, Trond & Roos, Norbert (1993). Receptor-mediated endocytosis of ricin in rat liver endothelial cells: An immonocytochemical study. European Journal of Cell Biology. ISSN 0171-9335. 60, s. 154–162. Fulltekst i vitenarkiv
• Senoo, Haruki; Smeland, Sigbjørn; Malaba, Lucie; Bjerknes, Tove; Stang, Espen & Roos, Norbert [Vis alle 9 forfattere av denne artikkelen] (1993). Transfer or retinol-binding protein from HepG2 human hepatoma cells to cocultured rat stellate cells. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 90, s. 3616–3620. Fulltekst i vitenarkiv
• Gudmundsen, Ola; Berg, Trond; Roos, Norbert & Nenseter, Marit Sofie (1993). Hepatic uptake of beta-VLDL in cholesterol-fed rabbits. Journal of Lipid Research. ISSN 0022-2275. 34, s. 589–600. Fulltekst i vitenarkiv
• Nenseter, Marit Sofie; Gudmundsen, O.; Roos, Norbert; Mælandsmo, Gunhild Mari; Drevon, Christian A & Berg, Trond (1992). Role of liver endothelial and Kupffer cells in clearing low density lipoprotein from blood in hypercholesterolemic rabbits. Journal of Lipid Research. ISSN 0022-2275. s. 867–877. Fulltekst i vitenarkiv
• Berg, Trond; Magnusson, Sigurdur; Stang, Espen & Roos, Norbert (1992). Receptor-mediated endocytosis in liver endothelial cells. Evidence of lysosomal heterogeneity. I Courtoy, Pierre J. (Red.), Endocytosis: From cell biology to health, disease and therapy. Springer. ISSN 9783540531463. s. 239–245. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Mertes, Verena; Linke, Dirk; Saragliadis, Athanasios; Roos, Norbert; Tysvær, Ellen-Beate & Mascherin, Elisa (2024). Recombinant extracellular vesicles as vaccines within animal health. Fulltekst i vitenarkiv Vis sammendrag

  Introduction: Secretion of extracellular vesicles (EVs) from the bacterial body is associated with a range of phenotypes including cell-cell communication, host-pathogen interactions and antimicrobial resistance development. EV may also elicit a humoral and antibody mediated immune response after immunization of a host making them an interesting vaccine candidate against an infectious agent. We have investigated the use of EV as a potential vaccine against several intracellular bacterial pathogens creating problems in farmed animals including fish. Immunization with EV revealed protection against some diseases, but not in others where we hypothesized that the EV was part of the microbial pathogenesis of the disease. To circumvent possible negative side effects of natural BEV with the host, we have explored the immunogenic properties of recombinant BEV (rEV) isolated from E. coli expressing antigens from the infectious bacterial species. Methods: We have expressed antigens from the fish bacterial species Yersinia ruckeri in E. coli. The rEV were isolated from E. coli using tangential flow and ultracentrifugation and compared to BEV isolated from the native E. coli strain. The rEVs were analyzed by transmission electron microscopy (TEM) and Nano-particle tracking analysis (NTA), and the antigen expression were confirmed by SDS-PAGE and mass spectrometry. The rEVs were exposed on fish cell cultures and the immune modulating properties were evaluated by qPCR. Results: Transmission electron microscopy revealed the presence of rEVs in the E. coli with similar shape to native E. coli EVs. Y. ruckeri antigens were successfully expressed in the rEVs as verified by SDS-PAGE and proteomic analysis using mass-spectrometry. Increased rEV concentrations were detected E. coli when expressing Y. ruckeri antigens compared to empty vector controls as verified by nanoparticle tracking analysis. Summary/conclusion: These results show that E. coli has the potential to be utilized as a vector for production of EVs expressing outer membrane antigens from Y. ruckeri and probably antigens from other bacterial species. These rEVs will hopefully circumvent the negative side effects of native EVs isolated from the pathogenic bacteria when used as vaccines and may enhance the repertoire of EVs based vaccines within animal health.

• Mertes, Verena; Linke, Dirk; Saragliadis, Athanasios; Roos, Norbert; Mascherin, Elisa & Tysvær, Ellen-Beate (2024). Recombinant extracellular vesicles as vaccines within animal health. Fulltekst i vitenarkiv Vis sammendrag

  Introduction: Secretion of extracellular vesicles (EVs) from the bacterial body is associated with a range of phenotypes including cell-cell communication, host-pathogen interactions and antimicrobial resistance development. EV may also elicit a humoral and antibody mediated immune response after immunization of a host making them an interesting vaccine candidate against an infectious agent. We have investigated the use of EV as a potential vaccine against several intracellular bacterial pathogens creating problems in farmed animals including fish. Immunization with EV revealed protection against some diseases, but not in others where we hypothesized that the EV was part of the microbial pathogenesis of the disease. To circumvent possible negative side effects of natural BEV with the host, we have explored the immunogenic properties of recombinant BEV (rEV) isolated from E. coli expressing antigens from the infectious bacterial species. Methods: We have expressed antigens from the fish bacterial species Yersinia ruckeri in E. coli. The rEV were isolated from E. coli using tangential flow and ultracentrifugation and compared to BEV isolated from the native E. coli strain. The rEVs were analyzed by transmission electron microscopy (TEM) and Nano-particle tracking analysis (NTA), and the antigen expression were confirmed by SDS-PAGE and mass spectrometry. The rEVs were exposed on fish cell cultures and the immune modulating properties were evaluated by qPCR. Results: Transmission electron microscopy revealed the presence of rEVs in the E. coli with similar shape to native E. coli EVs. Y. ruckeri antigens were successfully expressed in the rEVs as verified by SDS-PAGE and proteomic analysis using mass-spectrometry. Increased rEV concentrations were detected E. coli when expressing Y. ruckeri antigens compared to empty vector controls as verified by nanoparticle tracking analysis. Summary/conclusion: These results show that E. coli has the potential to be utilized as a vector for production of EVs expressing outer membrane antigens from Y. ruckeri and probably antigens from other bacterial species. These rEVs will hopefully circumvent the negative side effects of native EVs isolated from the pathogenic bacteria when used as vaccines and may enhance the repertoire of EVs based vaccines within animal health.

• Winther-Larsen, Hanne Cecilie; Mertes, Verena; Linke, Dirk; Saragliadis, Athanasios; Roos, Norbert & Mascherin, Elisa [Vis alle 7 forfattere av denne artikkelen] (2024). Recombinant extracellular vesicles as vaccines within animal health. Fulltekst i vitenarkiv Vis sammendrag

  Secretion of extracellular vesicles (EVs) from the bacterial body is associated with a range of phenotypes including cell-cell communication, host-pathogen interactions and antimicrobial resistance development. EV also elicit an immune response after immunization of a host making them an interesting vaccine candidate. We have investigated the use of EV as a potential vaccine against several bacterial pathogens creating problems in farmed animals including fish. Immunization with EV revealed protection against some diseases, but not in others where we hypothesized that the EV was part of the microbial pathogenesis. To circumvent possible negative side effects of natural EV, we have explored the recombinant EV (rEV) isolated from E. coli expressing antigens from other infectious agents. We have expressed antigens from the fish bacterial species Yersinia ruckeri in E. coli. The rEV was isolated using tangential flow and ultracentrifugation before analysis by transmission electron microscopy (TEM) and Nano-particle tracking analysis (NTA). The antigen expression was confirmed by SDS-PAGE and proteomics analysis. The rEVs did not elicit any toxicity when exposed to fish cells in culture. These results show that E. coli has the potential to be utilized as a vector for production of EVs expressing antigens from other bacterial species. These rEVs will hopefully circumvent the negative side effects of native EVs isolated from the pathogenic bacteria when used as vaccines and may enhance the repertoire of EVs based vaccines within animal health.

• Vogel, Anne Ilse Maria; Winther-Larsen, Hanne Cecilie; Roos, Norbert; Lale, Rahmi & Hohmann-Marriott, Martin Frank (2018). Function of type IV pili in iron acquisition in Synechococcus sp. PCC 7002. Fulltekst i vitenarkiv
• Vogel, Anne Ilse Maria; Winther-Larsen, Hanne Cecilie; Roos, Norbert; Lale, Rahmi & Hohmann-Marriott, Martin Frank (2018). Function of type IV pili in iron acquisition in Synechococcus sp. PCC 7002. Fulltekst i vitenarkiv
• Vogel, Anne Ilse Maria; Winther-Larsen, Hanne Cecilie; Roos, Norbert; Lale, Rahmi & Hohmann-Marriott, Martin Frank (2018). Function of type IV pili in iron acquisition in Synechococcus sp. PCC 7002. Fulltekst i vitenarkiv
• Vogel, Anne Ilse Maria; Winther-Larsen, Hanne Cecilie; Roos, Norbert; Lale, Rahmi & Hohmann-Marriott, Martin Frank (2018). A novel function of type IV pili in iron uptake in Synechococcus sp. PCC 7002. Fulltekst i vitenarkiv Vis sammendrag

  Iron is abundant in the Earth’s crust, but in marine environments, iron is often the limiting micronutrient for cyanobacterial growth. Marine cyanobacteria such as Synechococcus sp. PCC 7002 (hereafter Synechococcus) require iron for their photosynthetic machinery, especially Photosystem I, and have therefore developed efficient iron acquisition strategies. Recent research on type IV pili suggests that these so-called “nanowires” can increase metal bioavailability by facilitating reduction of extracellular electron acceptors such as iron oxides (1,2). These pili consist of tightly stacked pilA1 proteins and seem to have conductive properties (1). We deleted the gene encoding pilA1 in Synechococcus and studied the growth of the deletion strain on different iron minerals with varying bioavailability. The ΔpilA1 strain shows reduced growth compared to wildtype Synechococcus when grown on iron oxides with low bioavailability. We analyzed pili expression with SEM, TEM and mass spectrometry. Our results indicate a clear effect of pilA1 deletion on the expression of alternative pilins. Finally, we assessed the state of the photosynthetic complexes by spectroscopic methods. Spectral analysis of the ΔpilA1 strain indicate changes of the photosynthetic complexes consistent with iron stress. Our results indicate a novel function of type IV pili in iron acquisition in marine cyanobacteria. Heterologous pilA expression and deletion of genes involved in other parts of the external electron transport chain will further elucidate how intracellular electron transport is coupled to extracellular reduction. (1) Gorby YA, Yanina S, McLean JS, et al (2006) Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms. Proc Natl Acad Sci U S A 103:11358–63. doi: 10.1073/pnas.0604517103 (2) Lamb JJ, Hill RE, Eaton-Rye JJ, Hohmann-Marriott MF (2014) Functional role of PilA in iron acquisition in the cyanobacterium Synechocystis sp. PCC 6803. PLoS One 9:e105761. doi: 10.1371/journal.pone.0105761

• Vogel, Anne Ilse Maria; Winther-Larsen, Hanne Cecilie; Roos, Norbert; Lale, Rahmi & Hohmann-Marriott, Martin Frank (2018). Conductive Type IV pili play an important role for iron acquisition in the marine cyanobacterium Synechococcus sp. PCC 7002. Fulltekst i vitenarkiv
• Wessel, Øystein; Braaen, Stine; Alarcon, Marta; Haatveit, Hanne Merethe; Roos, Norbert & Markussen, Turhan [Vis alle 9 forfattere av denne artikkelen] (2017). Infection with purified Piscine orthoreovirus demonstrates a causal relationship with heart and skeletal muscle inflammation in Atlantic salmon. Fulltekst i vitenarkiv Vis sammendrag

  Introduction: Heart- and skeletal muscle inflammation (HSMI) is an emerging disease in Atlantic salmon (Salmo salar) farming. HSMI is associated with Piscine orthoreovirus (PRV) infection, but PRV is ubiquitous in farmed Atlantic salmon and thus present also in apparently healthy individuals. This has brought speculations if additional etiological factors are required, and experiments focusing on the causal relationship between PRV and HSMI are highly warranted. Methodology: A major bottleneck in PRV research has been the lack of cell lines that allow propagation of the virus. To bypass this, we propagated PRV in salmon, bled the fish at the peak of the infection, and purified virus particles from blood cells by gradient centrifugation. Electron microscopy, western blot and high-throughput sequencing all verified the purity of the viral particles. Two doses of purified PRV particles were inoculated into Atlantic salmon, which were cohabitated 50:50 with naïve individuals for eight weeks. PRV load and antiviral responses were examined by RT-qPCR, and histological analysis and immunostaining for PRV was performed in heart and muscle. Results: The purified virus replicated in inoculated fish, spread to naïve cohabitants, and induced histopathological changes consistent with HSMI. PRV specific staining was demonstrated in the pathological lesions. A dose-dependent response was observed; a high dose of virus gave earlier peak of the viral load and development of histopathological changes compared to a lower dose, but no difference in the severity of the disease. Conclusions: The experiment demonstrated that PRV can be purified from blood cells, and that PRV is the etiological agent of HSMI in Atlantic salmon.

• Brudal, Espen; Milton, Debra L; myrtennäs, Kerstin; Roos, Norbert; Griffiths, Gareth Wyn & Winther-Larsen, Hanne C. (2014). A degenerative Type IV pilus like system is functional and required for virulence in the fish pathogen Francisella noatunensis subsp. noatunensis. Fulltekst i vitenarkiv
• Vik, Åshild; Anonsen, Jan Haug; Aas, Finn Erik; Hegge, Finn Terje; Roos, Norbert & Koomey, Michael [Vis alle 7 forfattere av denne artikkelen] (2014). Type IV pilus assembly proficiency and dynamics influence pilin subunit phospho-form marcro- and microheterogeneity in Neisseria gonorrhoeae. Fulltekst i vitenarkiv
• Lystad, Alf Håkon; Sporstol, Marita; Foroughi, Masoud; Roos, Norbert; Berg, Trond & Eskild, Winnie (2009). Regulation of VEGF expression by vitamin D i hepatic stellate cells - possible attenuation by the nuclear receptor coregulator NCY-G1. Fulltekst i vitenarkiv
• Lystad, Alf Håkon; Sporstol, Marita; Foroughi, Masoud; Roos, Norbert; Berg, Trond & Eskild, Winnie (2009). Regulation of VEGF expression by vitamin D in hepatic stellate cells - possible attenuation by the nuclear receptor coregulator NCU-G1. Fulltekst i vitenarkiv
• Salomonsson, Emelie; Forsberg, A; Roos, Norbert; Holz, C; Maier, B. & Koomey, Michael [Vis alle 7 forfattere av denne artikkelen] (2009). Heterologous expression of Francisella tularensis type IV pili genes in Neisseria gonorrhoeae confirms that PilA can form functional pili. Fulltekst i vitenarkiv
• Farkas, Julia; Christian, P.; Hylland, Ketil; Ellesat, Kathrin; Roos, Norbert & Urrea, J. [Vis alle 9 forfattere av denne artikkelen] (2009). Effects of Silver and Gold nanoparticles on rainbow trout (Oncorhynchus mykiss) hepatocytes. Fulltekst i vitenarkiv
• Kåsi, Cecilie; Sporstol, Marita; Roos, Norbert; Berg, Trond & Eskild, Winnie (2007). NUCLEAR RECEPTORS IN HEPATIC STELLATE CELL ACTIVATION. Fulltekst i vitenarkiv
• Salomonsson, Emelie; Koomey, Michael; Roos, Norbert; Forsberg, Åke & Winther-Larsen, Hanne C (2007). Knowledge about the bioterrorism class A agent Francisella tularensis by utilizing Neisseria gonorrhoeae. Fulltekst i vitenarkiv
• Salomonsson, Emelie; Koomey, Michael; Roos, Norbert; Forsberg, Åke & Winther-Larsen, Hanne C (2007). Exploring the role of virulence-associated pilin proteins from Francisella tularensis using heterologous expression in Neisseria. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Heiniger, Ryan; Roos, Norbert; Putten, JPM van; Koomey, Michael & Wolfgang, Matthew (2006). Dynamics of Type IV pilus biogenesis in Pseudomonas aeruginosa. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Løvold, Cecilia; Wolfgang, Matthew; Putten, JPM van; Roos, Norbert & Aas, Finn Erik [Vis alle 10 forfattere av denne artikkelen] (2006). Microbial hair-extention. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Heiniger, Ryan W; Roos, Norbert; Egge-Jacobsen, Wolfgang; Putten, JPM van & Koomey, Michael [Vis alle 7 forfattere av denne artikkelen] (2006). Dynamics of Type IV pili Biogenesis in Pseudomonas aeruginosa. Fulltekst i vitenarkiv
• Løvold, Cecilia; Aas, Finn Erik; Winther-Larsen, Hanne C; Egge-Jacobsen, Wolfgang; Hegge, Finn Terje & Roos, Norbert [Vis alle 8 forfattere av denne artikkelen] (2005). Mutant analysis of dca: a gene encoding a putative transferase that mediates phosphoethanolamine and phosphocholine modifications of the Type IV pili in Neisseria gonorrhoeae. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Løvold, Cecilia; Wolfgang, Matthew; Putten, JPM van; Roos, Norbert & Aas, Finn Erik [Vis alle 10 forfattere av denne artikkelen] (2005). Pseudomonas aeruginosa PAK Type IV pili expression in Neisseria gonorrhoeae complements Tfp associated functions. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Løvold, Cecilia; Aas, Finn Erik; Roos, Norbert & Koomey, John Michael (2004). Complementation of both transformation competence and human cell adherence by hetrologous expression of the Pseudomonas aeruginosa Type IV pilin sunbunit in Neisseria gonorrhoea. Fulltekst i vitenarkiv
• Aas, Finn Erik; Løvold, Cecilia; Winther-Larsen, Hanne C; Jacobsen, Wolfgang Mathias; Roos, Norbert & Koomey, John Michael (2004). Characterization of dca, a gene involved in posttranslational modification of Neisseria gonorrhoeae Type IV Pili with phosphoethanolamine and phosphocholine. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Løvold, Cecilia; Aas, Finn Erik; Roos, Norbert & Koomey, John Michael (2004). Complementation of both transformation competence and human cell adherence by hetrologous expression of the Pseudomonas aeruginosa Type IV pilin sunbunit in Neisseria gonorrhoea. Fulltekst i vitenarkiv
• Winther-Larsen, Hanne C; Løvold, Cecilia; Aas, Finn Erik; Roos, Norbert & Koomey, John Michael (2004). Complementation of both transformation competence and human cell adherence by hetrologous expression of the Pseudomonas aeruginosa Type IV pilin sunbunit in Neisseria gonorrhoea. Fulltekst i vitenarkiv
• Oksvold, Morten Pedersen; Skarpen, Ellen; Roos, Norbert & Huitfeldt, Henrik (1999). Immunocytochemical localization of ligand-activated phosphorylated EGFR in endosomes. Proceedings of the American Association of Cancer Research. ISSN 0197-016X. 40, s. 336–336. Fulltekst i vitenarkiv
• Senoo, Haruki; Imamura, Kazuyuki; Wake, Kenjiro; Wold, Heidi L.; Moshaug, Jan Øivind & Kojima, Naosuke [Vis alle 14 forfattere av denne artikkelen] (1998). Vitamin A-storing system in mammals and birds in the arctic area - a study in the Svalbard archipelago. Fulltekst i vitenarkiv Vis sammendrag

  Arctic animals (polar bears, polar foxes, ringed seals etc) store large amounts of vitamin A in hepatic stellate cells. These animals do not show hypervitaminosis A.

• Brech, Andreas; Løvdahl, T; Kjeken, R; Roos, Norbert & Berg, Trond (1996). Density shift of endocytic vesicles induced by uptake of colloidal gold particles in rat hepatocytes. Zeitschrift für Gastroenterologie - German Journal of Gastroenterology. ISSN 0044-2771. 34, s. 79–80. Fulltekst i vitenarkiv
• Roos, Norbert; Cyrklaff, Marek; Cudmore, Sally; Krijnse-Locker, Jacomine; Blasco, Rafael & Griffiths, Gareth Wyn (1995). Cryo EM immunocytochemical analysis of the two infectious forms of vaccinia virus. European Journal of Cell Biology. ISSN 0171-9335. s. 108–109. Fulltekst i vitenarkiv

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