Heterogeneous Host Susceptibility Enhances Prevalence of Mixed-Genotype Micro-Parasite Infections

Dose response in micro-parasite infections is usually shallower than predicted by the independent action model, which assumes that each infectious unit has a probability of infection that is independent of the presence of other infectious units. Moreover, the prevalence of mixed-genotype infections was greater than predicted by this model. No probabilistic infection model has been proposed to account for the higher prevalence of mixed-genotype infections. We use model selection within a set of four alternative models to explain high prevalence of mixed-genotype infections in combination with a shallow dose response. These models contrast dependent versus independent action of micro-parasite infectious units, and homogeneous versus heterogeneous host susceptibility. We specifically consider a situation in which genome differences between genotypes are minimal, and highly unlikely to result in genotype-genotype interactions. Data on dose response and mixed-genotype infection prevalence were collected by challenging fifth instar Spodoptera exigua larvae with two genotypes of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), differing only in a 100 bp PCR marker sequence. We show that an independent action model that includes heterogeneity in host susceptibility can explain both the shallow dose response and the high prevalence of mixed-genotype infections. Theoretical results indicate that variation in host susceptibility is inextricably linked to increased prevalence of mixed-genotype infections. We have shown, to our knowledge for the first time, how heterogeneity in host susceptibility affects mixed-genotype infection prevalence. No evidence was found that virions operate dependently. While it has been recognized that heterogeneity in host susceptibility must be included in models of micro-parasite transmission and epidemiology to account for dose response, here we show that heterogeneity in susceptibility is also a fundamental principle explaining patterns of pathogen genetic diversity among hosts in a population. This principle has potentially wide implications for the monitoring, modeling and management of infectious diseases

Model-selection-based approach for calculating cellular multiplicity of infection during virus colonization of multi-cellular hosts

The cellular multiplicity of infection (MOI) is a key parameter for describing the interactions between virions and cells, predicting the dynamics of mixed-genotype infections, and understanding virus evolution. Two recent studies have reported in vivo MOI estimates for Tobacco mosaic virus (TMV) and Cauliflower mosaic virus (CaMV), using sophisticated approaches to measure the distribution of two virus variants over host cells. Although the experimental approaches were similar, the studies employed different definitions of MOI and estimation methods. Here, new model-selection-based methods for calculating MOI were developed. Seven alternative models for predicting MOI were formulated that incorporate an increasing number of parameters. For both datasets the best-supported model included spatial segregation of virus variants over time, and to a lesser extent aggregation of virus-infected cells was also implicated. Three methods for MOI estimation were then compared: the two previously reported methods and the best-supported model. For CaMV data, all three methods gave comparable results. For TMV data, the previously reported methods both predicted low MOI values (range: 1.04-1.23) over time, whereas the best-supported model predicted a wider range of MOI values (range: 1.01-2.10) and an increase in MOI over time. Model selection can therefore identify suitable alternative MOI models and suggest key mechanisms affecting the frequency of coinfected cells. For the TMV data, this leads to appreciable differences in estimated MOI values.This work was supported by grant BFU2012-30805 (SFE) and by 'Juan de la Cierva' postdoctoral contract JCI-2011-10379 (MPZ) from the Spanish Secretaria de Estado de Investigacion, Desarrollo e Innovacion. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Zwart, MP.; Tromas ., N.; Elena Fito, SF. (2013). Model-selection-based approach for calculating cellular multiplicity of infection during virus colonization of multi-cellular hosts. PLoS ONE. 8:64657-64657. https://doi.org/10.1371/journal.pone.0064657S64657646578Froissart, R., Wilke, C. O., Montville, R., Remold, S. K., Chao, L., & Turner, P. E. (2004). Co-infection Weakens Selection Against Epistatic Mutations in RNA Viruses. Genetics, 168(1), 9-19. doi:10.1534/genetics.104.030205Miyashita, S., & Kishino, H. (2009). Estimation of the Size of Genetic Bottlenecks in Cell-to-Cell Movement of Soil-Borne Wheat Mosaic Virus and the Possible Role of the Bottlenecks in Speeding Up Selection of Variations in trans-Acting Genes or Elements. Journal of Virology, 84(4), 1828-1837. doi:10.1128/jvi.01890-09Taylor, D. R., Zeyl, C., & Cooke, E. (2002). Conflicting levels of selection in the accumulation of mitochondrial defects inSaccharomycescerevisiae. Proceedings of the National Academy of Sciences, 99(6), 3690-3694. doi:10.1073/pnas.072660299Turner, P. E., & Chao, L. (1999). Prisoner’s dilemma in an RNA virus. Nature, 398(6726), 441-443. doi:10.1038/18913Turner, P. E., & Chao, L. (2003). Escape from Prisoner’s Dilemma in RNA Phage Φ6. The American Naturalist, 161(3), 497-505. doi:10.1086/367880Zwart, M. P., Erro, E., van Oers, M. M., de Visser, J. A. G. M., & Vlak, J. M. (2008). Low multiplicity of infection in vivo results in purifying selection against baculovirus deletion mutants. Journal of General Virology, 89(5), 1220-1224. doi:10.1099/vir.0.83645-0Godfray, H. C. J., O’reilly, D. R., & Briggs, C. J. (1997). A model of Nucleopolyhedrovirus (NPV) population genetics applied to co–occlusion and the spread of the few Polyhedra (FP) phenotype. Proceedings of the Royal Society of London. Series B: Biological Sciences, 264(1380), 315-322. doi:10.1098/rspb.1997.0045Bull, J. C., Godfray, H. C. J., & O’Reilly, D. R. (2001). Persistence of an Occlusion-Negative Recombinant Nucleopolyhedrovirus in Trichoplusia ni Indicates High Multiplicity of Cellular Infection. Applied and Environmental Microbiology, 67(11), 5204-5209. doi:10.1128/aem.67.11.5204-5209.2001Gonzalez-Jara, P., Fraile, A., Canto, T., & Garcia-Arenal, F. (2009). The Multiplicity of Infection of a Plant Virus Varies during Colonization of Its Eukaryotic Host. Journal of Virology, 83(15), 7487-7494. doi:10.1128/jvi.00636-09Gutiérrez, S., Yvon, M., Thébaud, G., Monsion, B., Michalakis, Y., & Blanc, S. (2010). Dynamics of the Multiplicity of Cellular Infection in a Plant Virus. PLoS Pathogens, 6(9), e1001113. doi:10.1371/journal.ppat.1001113Morra, M. R., & Petty, I. T. D. (2000). Tissue Specificity of Geminivirus Infection Is Genetically Determined. The Plant Cell, 12(11), 2259-2270. doi:10.1105/tpc.12.11.2259Silva, M. S., Goldbach, R. W., van Lent, J. W. M., & Wellink, J. (2002). Phloem loading and unloading of Cowpea mosaic virus in Vigna unguiculata. Journal of General Virology, 83(6), 1493-1504. doi:10.1099/0022-1317-83-6-1493Sokal RR, Rohlf FJ (1995) Biometry, 3rd edition. New York: W.H. Freeman and Co. 887 p.Zwart, M. P., Hemerik, L., Cory, J. S., de Visser, J. A. G. M., Bianchi, F. J. J. A., Van Oers, M. M., … Van der Werf, W. (2009). An experimental test of the independent action hypothesis in virus–insect pathosystems. Proceedings of the Royal Society B: Biological Sciences, 276(1665), 2233-2242. doi:10.1098/rspb.2009.0064Dietrich, C. (2003). Fluorescent labelling reveals spatial separation of potyvirus populations in mixed infected Nicotiana benthamiana plants. Journal of General Virology, 84(10), 2871-2876. doi:10.1099/vir.0.19245-0Zwart, M. P., Daròs, J.-A., & Elena, S. F. (2011). One Is Enough: In Vivo Effective Population Size Is Dose-Dependent for a Plant RNA Virus. PLoS Pathogens, 7(7), e1002122. doi:10.1371/journal.ppat.1002122Lafforgue, G., Tromas, N., Elena, S. F., & Zwart, M. P. (2012). Dynamics of the Establishment of Systemic Potyvirus Infection: Independent yet Cumulative Action of Primary Infection Sites. Journal of Virology, 86(23), 12912-12922. doi:10.1128/jvi.02207-12Dolja, V. V., McBride, H. J., & Carrington, J. C. (1992). Tagging of plant potyvirus replication and movement by insertion of beta-glucuronidase into the viral polyprotein. Proceedings of the National Academy of Sciences, 89(21), 10208-10212. doi:10.1073/pnas.89.21.10208Van der Werf, W., Hemerik, L., Vlak, J. M., & Zwart, M. P. (2011). Heterogeneous Host Susceptibility Enhances Prevalence of Mixed-Genotype Micro-Parasite Infections. PLoS Computational Biology, 7(6), e1002097. doi:10.1371/journal.pcbi.1002097Barlow, N. D. (1991). A Spatially Aggregated Disease/Host Model for Bovine Tb in New Zealand Possum Populations. The Journal of Applied Ecology, 28(3), 777. doi:10.2307/2404207Barlow, N. D. (2000). Non-linear transmission and simple models for bovine tuberculosis. Journal of Animal Ecology, 69(4), 703-713. doi:10.1046/j.1365-2656.2000.00428.xR Core Team (2012) R: A Language and Environment for Statistical Computing. Vienna: R Foundation for Statistical Computing.Olkin I, Gleser LJ, Derman C. (1994) Probability Models and Applications, 2nd ed. New York: Macmillan. 575 p

A missing dimension in measures of vaccination impacts

Immunological protection, acquired from either natural infection or vaccination, varies among hosts, reflecting underlying biological variation and affecting population-level protection. Owing to the nature of resistance mechanisms, distributions of susceptibility and protection entangle with pathogen dose in a way that can be decoupled by adequately representing the dose dimension. Any infectious processes must depend in some fashion on dose, and empirical evidence exists for an effect of exposure dose on the probability of transmission to mumps-vaccinated hosts [1], the case-fatality ratio of measles [2], and the probability of infection and, given infection, of symptoms in cholera [3]. Extreme distributions of vaccine protection have been termed leaky (partially protects all hosts) and all-or-nothing (totally protects a proportion of hosts) [4]. These distributions can be distinguished in vaccine field trials from the time dependence of infections [5]. Frailty mixing models have also been proposed to estimate the distribution of protection from time to event data [6], [7], although the results are not comparable across regions unless there is explicit control for baseline transmission [8]. Distributions of host susceptibility and acquired protection can be estimated from dose-response data generated under controlled experimental conditions [9]–[11] and natural settings [12], [13]. These distributions can guide research on mechanisms of protection, as well as enable model validity across the entire range of transmission intensities. We argue for a shift to a dose-dimension paradigm in infectious disease science and community health

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

One Is Enough: In Vivo Effective Population Size Is Dose-Dependent for a Plant RNA Virus

Effective population size (Ne) determines the strength of genetic drift and the frequency of co-infection by multiple genotypes, making it a key factor in viral evolution. Experimental estimates of Ne for different plant viruses have, however, rendered diverging results. The independent action hypothesis (IAH) states that each virion has a probability of infection, and that virions act independent of one another during the infection process. A corollary of IAH is that Ne must be dose dependent. A test of IAH for a plant virus has not been reported yet. Here we perform a test of an IAH infection model using a plant RNA virus, Tobacco etch virus (TEV) variants carrying GFP or mCherry fluorescent markers, in Nicotiana tabacum and Capsicum annuum plants. The number of primary infection foci increased linearly with dose, and was similar to a Poisson distribution. At high doses, primary infection foci containing both genotypes were found at a low frequency (<2%). The probability that a genotype that infected the inoculated leaf would systemically infect that plant was near 1, although in a few rare cases genotypes could be trapped in the inoculated leaf by being physically surrounded by the other genotype. The frequency of mixed-genotype infection could be predicted from the mean number of primary infection foci using the independent-action model. Independent action appears to hold for TEV, and Ne is therefore dose-dependent for this plant RNA virus. The mean number of virions causing systemic infection can be very small, and approaches 1 at low doses. Dose-dependency in TEV suggests that comparison of Ne estimates for different viruses are not very meaningful unless dose effects are taken into consideration

Evolutionary Trajectory of White Spot Syndrome Virus (WSSV) Genome Shrinkage during Spread in Asia

Background - White spot syndrome virus (WSSV) is the sole member of the novel Nimaviridae family, and the source of major economic problems in shrimp aquaculture. WSSV appears to have rapidly spread worldwide after the first reported outbreak in the early 1990s. Genomic deletions of various sizes occur at two loci in the WSSV genome, the ORF14/15 and ORF23/24 variable regions, and these have been used as molecular markers to study patterns of viral spread over space and time. We describe the dynamics underlying the process of WSSV genome shrinkage using empirical data and a simple mathematical model. Methodology/Principal Findings - We genotyped new WSSV isolates from five Asian countries, and analyzed this information together with published data. Genome size appears to stabilize over time, and deletion size in the ORF23/24 variable region was significantly related to the time of the first WSSV outbreak in a particular country. Parameter estimates derived from fitting a simple mathematical model of genome shrinkage to the data support a geometric progression (

Knowledge, Attitudes and Practices (KAP) related to the Pandemic (H1N1) 2009 among Chinese General Population: a Telephone Survey

<p>Abstract</p> <p>Background</p> <p>China is at greatest risk of the Pandemic (H1N1) 2009 due to its huge population and high residential density. The unclear comprehension and negative attitudes towards the emerging infectious disease among general population may lead to unnecessary worry and even panic. The objective of this study was to investigate the Chinese public response to H1N1 pandemic and provide baseline data to develop public education campaigns in response to future outbreaks.</p> <p>Methods</p> <p>A close-ended questionnaire developed by the Chinese Center for Disease Control and Prevention was applied to assess the knowledge, attitudes and practices (KAP) of pandemic (H1N1) 2009 among 10,669 responders recruited from seven urban and two rural areas of China sampled by using the probability proportional to size (PPS) method.</p> <p>Results</p> <p>30.0% respondents were not clear whether food spread H1N1 virusand. 65.7% reported that the pandemic had no impact on their life. The immunization rates of the seasonal flu and H1N1vaccine were 7.5% and 10.8%, respectively. Farmers and those with lower education level were less likely to know the main transmission route (cough or talk face to face). Female and those with college and above education had higher perception of risk and more compliance with preventive behaviors. Relationships between knowledge and risk perception (OR = 1.69; 95%CI 1.54-1.86), and knowledge and practices (OR = 1.57; 95%CI 1.42-1.73) were found among the study subjects. With regard to the behavior of taking up A/H1N1 vaccination, there are several related factors found in the current study population, including the perception of life disturbed (OR = 1.29; 95%CI 1.11-1.50), the safety of A/H1N1 vaccine (OR = 0.07; 95%CI 0.04-0.11), the knowledge of free vaccination policy (OR = 7.20; 95%CI 5.91-8.78), the state's priority vaccination strategy(OR = 1.33; 95%CI 1.08-1.64), and taking up seasonal influenza vaccine behavior (OR = 4.69; 95%CI 3.53-6.23).</p> <p>Conclusions</p> <p>This A/H1N1 epidemic has not caused public panic yet, but the knowledge of A/H1N1 in residents is not optimistic. Public education campaign may take the side effects of vaccine and the knowledge about the state's vaccination strategy into account.</p

Ankyrin-mediated self-protection during cell invasion by the bacterial predator Bdellovibrio bacteriovorus

Predatory Bdellovibrio bacteriovorus are natural antimicrobial organisms, killing other bacteria by whole-cell invasion. Self-protection against prey-metabolizing enzymes is important for the evolution of predation. Initial prey entry involves the predator’s peptidoglycan DD-endopeptidases, which decrosslink cell walls and prevent wasteful entry by a second predator. Here we identify and characterize a self-protection protein from B. bacteriovorus, Bd3460, which displays an ankyrin-based fold common to intracellular pathogens of eukaryotes. Co-crystal structures reveal Bd3460 complexation of dual targets, binding a conserved epitope of each of the Bd3459 and Bd0816 endopeptidases. Complexation inhibits endopeptidase activity and cell wall decrosslinking in vitro. Self-protection is vital — DBd3460 Bdellovibrio deleteriously decrosslink self-peptidoglycan upon invasion, adopt a round morpholog, and lose predatory capacity and cellular integrity. Our analysis provides the first mechanistic examination of self-protection in Bdellovibrio, documents protection-multiplicity for products of two different genomic loci, and reveals an important evolutionary adaptation to an invasive predatory bacterial lifestyle

Practice Induces Function-Specific Changes in Brain Activity

Practice can have a profound effect on performance and brain activity, especially if a task can be automated. Tasks that allow for automatization typically involve repeated encoding of information that is paired with a constant response. Much remains unknown about the effects of practice on encoding and response selection in an automated task.To investigate function-specific effects of automatization we employed a variant of a Sternberg task with optimized separation of activity associated with encoding and response selection by means of m-sequences. This optimized randomized event-related design allows for model free measurement of BOLD signals over the course of practice. Brain activity was measured at six consecutive runs of practice and compared to brain activity in a novel task.Prompt reductions were found in the entire cortical network involved in encoding after a single run of practice. Changes in the network associated with response selection were less robust and were present only after the third run of practice.This study shows that automatization causes heterogeneous decreases in brain activity across functional regions that do not strictly track performance improvement. This suggests that cognitive performance is supported by a dynamic allocation of multiple resources in a distributed network. Our findings may bear importance in understanding the role of automatization in complex cognitive performance, as increased encoding efficiency in early stages of practice possibly increases the capacity to otherwise interfering information

The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure