| 1. |
- Bzhalava, Davit, et al.
(författare)
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Phylogenetically diverse TT virus viremia among pregnant women
- 2012
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Ingår i: Virology. - : Elsevier BV. - 1096-0341 .- 0042-6822. ; 432:2, s. 427-434
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Tidskriftsartikel (refereegranskat)abstract
- Infections during pregnancy have been suggested to be involved in childhood leukemias. We used high-throughput sequencing to describe the viruses most readily detectable in serum samples of pregnant women. Serum DNA of 112 mothers to leukemic children was amplified using whole genome amplification. Sequencing identified one TT virus (TTV) isolate belonging to a known type and two putatively new TTVs. For 22 mothers, we also performed ITV amplification by general primer PCR before sequencing. This detected 39 TTVs, two of which were identical to the Tilts found after whole genome amplification. Altogether, we found 40 TTV isolates, 29 of which were putatively new types (similarities ranging from 89% to 69%). In conclusion, high throughput sequencing is useful to describe the known or unknown viruses that are present in serum samples of pregnant women. (C) 2012 Elsevier Inc. All rights reserved.
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| 2. |
- Lysholm, Fredrik, et al.
(författare)
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An efficient simulator of 454 data using configurable statistical models
- 2011
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Ingår i: BMC Research Notes. - : Springer Science and Business Media LLC. - 1756-0500. ; 4:449
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundRoche 454 is one of the major 2nd generation sequencing platforms. The particular characteristics of 454 sequence data pose new challenges for bioinformatic analyses, e.g. assembly and alignment search algorithms. Simulation of these data is therefore useful, in order to further assess how bioinformatic applications and algorithms handle 454 data.FindingsWe developed a new application named 454sim for simulation of 454 data at high speed and accuracy. The program is multi-thread capable and is available as C++ source code or pre-compiled binaries. Sequence reads are simulated by 454sim using a set of statistical models for each chemistry. 454sim simulates recorded peak intensities, peak quality deterioration and it calculates quality values. All three generations of the Roche 454 chemistry ('GS20', 'GS FLX' and 'Titanium') are supported and defined in external text files for easy access and tweaking.ConclusionsWe present a new platform independent application named 454sim. 454sim is generally 200 times faster compared to previous programs and it allows for simple adjustments of the statistical models. These improvements make it possible to carry out more complex and rigorous algorithm evaluations in a reasonable time scale.
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| 3. |
- Lysholm, Fredrik, 1981-
(författare)
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Bioinformatic methods for characterization of viral pathogens in metagenomic samples
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Virus infections impose a huge disease burden on humanity and new viruses are continuously found. As most studies of viral disease are limited to theinvestigation of known viruses, it is important to characterize all circulating viruses. Thus, a broad and unselective exploration of the virus flora would be the most productive development of modern virology. Fueled by the reduction in sequencing costs and the unbiased nature of shotgun sequencing, viral metagenomics has rapidly become the strategy of choice for this exploration.This thesis mainly focuses on improving key methods used in viral metagenomics as well as the complete viral characterization of two sets of samples using these methods. The major methods developed are an efficient automated analysis pipeline for metagenomics data and two novel, more accurate, alignment algorithms for 454 sequencing data. The automated pipeline facilitates rapid, complete and effortless analysis of metagenomics samples, which in turn enables detection of potential pathogens, for instance in patient samples. The two new alignment algorithms developed cover comparisons both against nucleotide and protein databases, while retaining the underlying 454 data representation. Furthermore, a simulator for 454 data was developed in order to evaluate these methods. This simulator is currently the fastest and most complete simulator of 454 data, which enables further development of algorithms and methods. Finally, we have successfully used these methods to fully characterize a multitude of samples, including samples collected from children suffering from severe lower respiratory tract infections as well as patients diagnosed with chronic fatigue syndrome, both of which presented in this thesis. In these studies, a complete viral characterization has revealed the presence of both expected and unexpected viral pathogens as well as many potential novel viruses.
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| 4. |
- Lysholm, Fredrik, et al.
(författare)
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Characterization of the viral microbiome in patients with severe lower respiratory tract infections, using metagenomic sequencing
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- The human respiratory tract is heavily exposed to microorganisms. Viral respiratory tract pathogens, like RSV, influenza and rhinoviruses cause major morbidity and mortality from respiratory tract disease. Furthermore, as viruses have limited means of transmission, viruses that cause pathogenicity in other tissues may be transmitted through the respiratory tract. It is therefore important to chart the human virome in this compartment. We have studied nasopharyngeal aspirate samples submitted to the Karolinska University Laboratory, Stockholm, Sweden from March 2004 to May 2005 for diagnosis of respiratory tract infections. We have used a metagenomic sequencing strategy to characterize viruses, as this provides the most unbiased view of the samples. Virus enrichment followed by 454 sequencing resulted in totally 703,790 reads and 110,931 of these were found to be of viral origin by using an automated classification pipeline. The snapshot of the respiratory tract virome of these 210 patients revealed 39 species and many more strains of viruses. Most of the viral sequences were classified into one of three major families; Paramyxoviridae, Picornaviridae or Orthomyxoviridae. The study also identified one novel type of Rhinovirus C, and identified a number of previously undescribed viral genetic fragments of unknown origin.
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| 5. |
- Lysholm, Fredrik, et al.
(författare)
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FAAST: Flow-space Assisted Alignment Search Tool
- 2011
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Ingår i: BMC Bioinformatics. - : BioMed Central. - 1471-2105. ; 12:293
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Tidskriftsartikel (refereegranskat)abstract
- Background: High throughput pyrosequencing (454 sequencing) is the major sequencing platform for producing long read high throughput data. While most other sequencing techniques produce reading errors mainly comparable with substitutions, pyrosequencing produce errors mainly comparable with gaps. These errors are less efficiently detected by most conventional alignment programs and may produce inaccurate alignments. less thanbrgreater than less thanbrgreater thanResults: We suggest a novel algorithm for calculating the optimal local alignment which utilises flowpeak information in order to improve alignment accuracy. Flowpeak information can be retained from a 454 sequencing run through interpretation of the binary SFF-file format. This novel algorithm has been implemented in a program named FAAST (Flow-space Assisted Alignment Search Tool). less thanbrgreater than less thanbrgreater thanConclusions: We present and discuss the results of simulations that show that FAAST, through the use of the novel algorithm, can gain several percentage points of accuracy compared to Smith-Waterman-Gotoh alignments, depending on the 454 data quality. Furthermore, through an efficient multi-thread aware implementation, FAAST is able to perform these high quality alignments at high speed. The tool is available at http://www.ifm.liu.se/bioinfo/
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| 6. |
- Sullivan, Patrick F, et al.
(författare)
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An unbiased metagenomic search for infectious agents using monozygotic twins discordantfor chronic fatigue
- 2011
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Ingår i: BMC Microbiology. - : BMC. - 1471-2180. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: Chronic fatigue syndrome is an idiopathic syndrome widely suspected of having an infectious orimmune etiology. We applied an unbiased metagenomic approach to try to identify known or novel infectiousagents in the serum of 45 cases with chronic fatigue syndrome or idiopathic chronic fatigue. Controls were theunaffected monozygotic co-twins of cases, and serum samples were obtained at the same place and time.Results: No novel DNA or RNA viral signatures were confidently identified. Four affected twins and no unaffectedtwins evidenced viremia with GB virus C (8.9% vs. 0%, p = 0.019), and one affected twin had previously undetectedhepatitis C viremia. An excess of GB virus C viremia in cases with chronic fatigue requires confirmation.Conclusions: Current, impairing chronic fatigue was not robustly associated with viremia detectable in serum.
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