Complex dynamics of defective interfering baculoviruses during serial passage in insect cells

Defective interfering (DI) viruses are thought to cause oscillations in virus levels, known as the 'Von Magnus effect'. Interference by DI viruses has been proposed to underlie these dynamics, although experimental tests of this idea have not been forthcoming. For the baculoviruses, insect viruses commonly used for the expression of heterologous proteins in insect cells, the molecular mechanisms underlying DI generation have been investigated. However, the dynamics of baculovirus populations harboring DIs have not been studied in detail. In order to address this issue, we used quantitative real-time PCR to determine the levels of helper and DI viruses during 50 serial passages of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) in Sf21 cells. Unexpectedly, the helper and DI viruses changed levels largely in phase, and oscillations were highly irregular, suggesting the presence of chaos. We therefore developed a simple mathematical model of baculovirus-DI dynamics. This theoretical model reproduced patterns qualitatively similar to the experimental data. Although we cannot exclude that experimental variation (noise) plays an important role in generating the observed patterns, the presence of chaos in the model dynamics was confirmed with the computation of the maximal Lyapunov exponent, and a Ruelle-Takens-Newhouse route to chaos was identified at decreasing production of DI viruses, using mutation as a control parameter. Our results contribute to a better understanding of the dynamics of DI baculoviruses, and suggest that changes in virus levels over passages may exhibit chaos.The authors thank Javier Carrera, Just Vlak and Lia Hemerik for helpful discussion. MPZ was supported by a Rubicon Grant from the Netherlands Organization for Scientific Research (NWO, www.nwo.nl) and a 'Juan de la Cierva' postdoctoral contract (JCI-2011-10379) from the Spanish 'Secretaria de Estado de Investigacion, Desarrollo e Innovacion'. JS was supported by the Botin Foundation. SFE was supported by grant BFU2012-30805, also from the Spanish 'Secretaria de Estado de Investigacion, Desarrollo e Innovacion'.Zwart, MP.; Pijlman, G.; Sardanyes Cayuela, J.; Duarte, J.; Januario, C.; Elena Fito, SF. (2013). Complex dynamics of defective interfering baculoviruses during serial passage in insect cells. Journal of Biological Physics. 39(2):327-342. doi:10.1007/s10867-013-9317-9S327342392Von Magnus, P.: Incomplete forms of influenza virus. Adv. Virus. Res. 2, 59–79 (1954)Huang, A.S.: Defective interfering viruses. Annu. Rev. Microbiol. 27, 101–117 (1973)Kool, M., Voncken, J.W., Vanlier, F.L.J., Tramper, J., Vlak, J.M.: Detection and analysis of Autographa californica nuclear polyhedrosis-virus mutants with defective interfering properties. Virology 183, 739–746 (1991)Wickham, T.J., Davis, T., Granados, R.R., Hammer, D.A., Shuler, M.L., Wood, H.A.: Baculovirus defective interfering particles are responsible for variations in recombinant protein-production as a function of multiplicity of infection. Biotechnol. Lett. 13, 483–488 (1991)Pijlman, G.P., van den Born, E., Martens, D.E., Vlak, J.M.: Autographa californica baculoviruses with large genomic deletions are rapidly generated in infected insect cells. Virology 283, 132–138 (2001)Giri, L., Feiss, M.G., Bonning, B.C., Murhammer, D.W.: Production of baculovirus defective interfering particles during serial passage is delayed by removing transposon target sites in fp25k. J. Gen. Virol. 93, 389–399 (2012)King, L.A., Possee, R.D.: The Baculovirus Expression System. University Press, Cambridge (1992)Lee, H.Y., Krell, P.J.: Reiterated DNA fragments in defective genomes of Autographa californica nuclear polyhedrosis virus are competent for AcMNPV-dependent DNA replication. Virology 202, 418–429 (1994)Pijlman, G.P., Dortmans, J., Vermeesch, A.M.G., Yang, K., Martens, D.E., Goldbach, R.W., Vlak, J.M.: Pivotal role of the non-hr origin of DNA replication in the genesis of defective interfering baculoviruses. J. Virol. 76, 5605–5611 (2002)Pijlman, G.P., van Schijndel, J.E., Vlak, J.M.: Spontaneous excision of BAC vector sequences from bacmid-derived baculovirus expression vectors upon passage in insect cells. J. Gen. Virol. 84, 2669–2678 (2003)Pijlman, G.P., Vermeesch, A.M.G., Vlak, J.M.: Cell line-specific accumulation of the baculovirus non-hr origin of DNA replication in infected insect cells. J. Invertebr. Pathol. 84, 214–219 (2003)Roux, L., Simon, A.E., Holland, J.J.: Effects of defective interfering viruses on virus-replication and pathogenesis in vitro and in vivo. Adv. Virus. Res. 40, 181–211 (1991)Grabau, E.A., Holland, J.J.: Analysis of viral and defective-interfering nucleocapsids in acute and persistent infection by Rhadoviruses. J. Gen. Virol. 60, 87–97 (1982)Kawai, A., Matsumoto, S., Tanabe, K.: Characterization of Rabies viruses recovered from persistently infected BHK cells. Virology 67, 520–533 (1975)Roux, L., Holland, J.J.: Viral genome synthesis in BHK-21 cells persistently infected with Sendai virus. Virology 100, 53–64 (1980)Palma, E.L., Huang, A.: Cyclic production of vesicular stomatitis virus cause by defective interfering particles. J. Infect. Dis. 129, 402–410 (1974).Stauffer Thompson, K.A., Yin, J.: Population dynamics of an RNA virus and its defective interfering particles in passage cultures. Virol. J. 7, 257–266 (2010)Szathmáry, E.: Cooperation and defection – playing the field in virus dynamics. J. Theor. Biol. 165, 341–356 (1993)Bangham, C.R.M., Kirkwood, T.B.L.: Defective interfering particles – effects in modulating virus growth and persistence. Virology 179, 821–826 (1990)Kirkwood, T.B.L., Bangham, C.R.M.: Cycles, chaos, and evolution in virus cultures – a model of defective interfering particles. Proc. Natl. Acad. Sci. USA 91, 8685–8689 (1994)De Gooijer, C.D., Koken, R.H.M., van Lier, F.L.J., Kool, M., Vlak, J.M., Tramper, J.: A structured dynamic model for the baculovirus infection process in insect-cell reactor configurations. Biotech. Bioeng. 40, 537–548 (1992)Van Lier, F.L.J., van der Meijs, W.C.J., Grobben, N.G., Olie, R.A., Vlak, J.M., Tramper, J.: Continuous beta-galactosidase production with a recombinant baculovirus insect-cell system in bioreactors. J. Biotechnol. 22, 291–298 (1992)Van Lier, F.L.J., van den Hombergh, J., de Gooijer, C.D., den Boer, M.M., Vlak, J.M., Tramper, J.: Long-term semi-continuous production of recombinant baculovirus protein in a repeated (fed-)batch two-stage reactor system. Enzyme Microb. Technol. 18, 460–466 (1996)Zwart, M.P., Erro, E., van Oers, M.M., de Visser, J.A.G.M., Vlak, J.M.: Low multiplicity of infection in vivo results in purifying selection against baculovirus deletion mutants. J. Gen. Virol. 89, 1220–1224 (2008)Luckow, V.A., Lee, S.C., Barry, G.F., Olins, P.O.: Efficient generation of infectious recombinant baculoviruses by site-specific transposon-mediated insertion of foreign genes into a baculovirus genome propagated in Escherichia coli. J. Virol. 67, 4566–4579 (1993)Vaughn, J.L., Goodwin, R.H., Tompkins, G.J., McCawley, P.: Establishment of 2 cell lines from insect Spodoptera frugiperda (Lepidoptera, Noctuidae). In Vitro 13, 213–217 (1977)Zwart, M.P., van Oers, M.M., Cory, J.S., van Lent, J.W.M., van der Werf, W., Vlak, J.M.: Development of a quantitative real-time PCR for determination of genotype frequencies for studies in baculovirus population biology. J. Virol. Meth. 148, 146–154 (2008)Zwart, M.P., Hemerik, L., Cory, J.S., de Visser, J.A.G.M., Bianchi, F.J.J.A., van Oers, M.M., Vlak, J.M., Hoekstra, R.F., van der Werf, W.: An experimental test of the independent action hypothesis in virus-insect pathosystems. Proc. R. Soc. B 276, 2233–2242 (2009)Olkin, I., Gleser, L.J., Derman, C.: Probability Models and Applications. Macmillan, New York (1994)Parker, T., Chua, L.: Practical Numerical Algorithms for Chaotic Systems. Springer-Verlag, Berlin (1989)Dieci, L., van Vleck, E.S.: Computation of a few Lyapunov exponents for continuous and discrete dynamical systems. J. Appl. Numer. Math. 17, 275–291 (1995)Matsumoto, T., Chua, L.O., Komuro, M.: The double scroll. IEEE Trans. Circuits Syst. 32, 797–818 (1985)Chua, L.O., Komuro, M., Matsumoto, T.: The double scroll family: rigorous proof of chaos. IEEE Trans. Circuits Syst. 33, 1072–1097 (1986)Ramasubramanian, K., Sriram, M.S.: A comparative study of computation of Lyapunov spectra with different algorithms. Phys. D: Nonlin. Phenom. 139, 72–86 (2000)Lee, H.Y., Krell, P.J.: Generation and analysis of defective genomes of Autographa californica nuclear polyhedrosis virus. J. Virol. 66, 4339–4347 (1992)Kovacs, G.R., Choi, J., Guarino, L.A., Summers MD: Functional dissection of the Autographa californica nuclear polyhedrosis virus immediate early 1 transcriptional regulatory protein. J. Virol. 66, 7429–7437 (1992)Legendre, P., Legendre, L.: Numerical Ecology. Elsevier, Amsterdam (1998)Schuster, H.G.: Deterministic Chaos: An Introduction. Wiley-VCH Verlag GmbH & Co. KGaA, Wienheim (2005)Strogatz, S.H.: Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry and Engineering. Westview Press, Cambridge (1994)Dennis, B., Desharnais, R.A., Cushing, J.M., Henson, S.M., Constantino, R.F.: Can noise induce chaos? Oikos 102, 329–339 (2003)Crutchfield, J.P., Huberman, B.A.: Fluctuations and the onset of chaos. Phys. Lett. A 77, 407–410 (1980)Crutchfield, J.P., Farmer, J.D.: Fluctuations and simple chaotic dynamics. Phys. Rep. 92, 45–82 (1982

Implementation of laparoscopic hysterectomy for endometrial cancer over the past decade

Background: Laparoscopic hysterectomy (LH) for the treatment of early-stage endometrial carcinoma/cancer (EC) has demonstrated to be safe in several randomized controlled trials. Yet, data on implementation of LH in clinical practice are limited. In the present study, implementation of LH for EC was evaluated in a large oncology network in the Netherlands. Results: Retrospectively, a total of 556 EC patients with FIGO stage I-II were registered in the selected years. The proportion of LH gradually increased from 11% in 2006 to 85% in 2015. LH was more often performed in patients with low-grade EC and was not related to the studied patient characteristics. The introduction of TLH was frequently preceded by LAVH. Patients treated in teaching hospitals were more likely to undergo a LH compared to patients in non-teaching hospitals. The conversion rate was 7.7%, and the overall complication rates between LH and AH were comparable, but less postoperative complications in LH. Conclusions: Implementation of laparoscopic hysterectomy for early-stage EC increased from 11 to 85% in 10 years. Implementation of TLH was often preceded by LAVH and was faster in teaching hospitals

Substance-Related Health Problems during Rave Parties in the Netherlands (1997–2008)

The objective of this study was to describe a 12-year (1997–2008) observation of substance-related incidents occurring at rave parties in the Netherlands, including length of visits to first-aid stations, substances used, and severity of the incidents. During rave parties, specifically trained medical and paramedical personnel staffed first aid stations. Visitors were diagnosed and treated, and their data were recorded using standardized methods. During the 12-year period with 249 rave parties involving about 3,800,000 visitors, 27,897 people visited a first aid station, of whom 10,100 reported having a substance-related problem. The mean age of these people was 22.3+/−5.4 years; 52.4% of them were male. Most (66.7%) substance-related problems were associated with ecstasy or alcohol use or both. Among 10,100 substance-related cases, 515 required professional medical care, and 16 of these cases were life threatening. People with a substance-related problem stayed 20 min at the first aid station, which was significantly longer than the 5 min that those without a substance-related health problem stayed. These unique data from the Netherlands identify a variety of acute health problems related to the use of alcohol, amphetamines, cannabis, cocaine, ecstasy, and GHB. Although most problems were minor, people using GHB more often required professional medical care those using the other substances. We recommended adherence to harm and risk reduction policy, and the use of first aid stations with specially trained staff for both minor and serious incidents

Can understanding reward help illuminate anhedonia?

Purpose of review: The goal of this paper is to examine how reward processing might help us understand the symptom of anhedonia. Recent findings: There are extensive reviews exploring the relationship between responses to rewarding stimuli and depression. These often include a discussion on anhedonia and how this might be underpinned in particular by dysfunctional reward processing. However, there is no specific consensus on whether studies to date have adequately examined the various sub-components of reward processing or how these might relate in turn to various aspects of anhedonia symptoms. Summary: The approach to understanding the symptom of anhedonia should be to examine all the sub-components of reward processing at the subjective and objective behavioural and neural level, with well validated tasks that can be replicated. Investigating real life experiences of anhedonia and how theses might be predicted by objective lab measures is also needed in future research

2′-O Methylation of the Viral mRNA Cap by West Nile Virus Evades Ifit1-Dependent and -Independent Mechanisms of Host Restriction In Vivo

Prior studies have shown that 2′-O methyltransferase activity of flaviviruses, coronaviruses, and poxviruses promotes viral evasion of Ifit1, an interferon-stimulated innate immune effector protein. Viruses lacking 2′-O methyltransferase activity exhibited attenuation in primary macrophages that was rescued in cells lacking Ifit1 gene expression. Here, we examined the role of Ifit1 in restricting pathogenesis in vivo of wild type WNV (WNV-WT) and a mutant in the NS5 gene (WNV-E218A) lacking 2′-O methylation of the 5′ viral RNA cap. While deletion of Ifit1 had marginal effects on WNV-WT pathogenesis, WNV-E218A showed increased replication in peripheral tissues of Ifit1−/− mice after subcutaneous infection, yet this failed to correlate with enhanced infection in the brain or lethality. In comparison, WNV-E218A was virulent after intracranial infection as judged by increased infection in different regions of the central nervous system (CNS) and a greater than 16,000-fold decrease in LD50 values in Ifit1−/− compared to wild type mice. Ex vivo infection experiments revealed cell-type specific differences in the ability of an Ifit1 deficiency to complement the replication defect of WNV-E218A. In particular, WNV-E218A infection was impaired in both wild type and Ifit1−/− brain microvascular endothelial cells, which are believed to participate in blood-brain barrier (BBB) regulation of virus entry into the CNS. A deficiency of Ifit1 also was associated with increased neuronal death in vivo, which was both cell-intrinsic and mediated by immunopathogenic CD8+ T cells. Our results suggest that virulent strains of WNV have largely evaded the antiviral effects of Ifit1, and viral mutants lacking 2′-O methylation are controlled in vivo by Ifit1-dependent and -independent mechanisms in different cell types

Winst & weidevogels: weidemaatregelen voor (functionele agro-)biodiversiteit

In het project Winst & Weidevogels is samen met collectieven en melkveehouders gewerkt aan meer biodiversiteit en het behoud van weidevogels. In deze brochure is de kennis, ervaring en onderzoek zoveel mogelijk gebundeld. Het levert aanbevelingen voor de praktijk