| 1. |
- Abi-Rached, Laurent, et al.
(författare)
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The Shaping of Modern Human Immune Systems by Multiregional Admixture with Archaic Humans
- 2011
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 334:6052, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- Whole genome comparisons identified introgression from archaic to modern humans. Our analysis of highly polymorphic human leukocyte antigen (HLA) class I, vital immune system components subject to strong balancing selection, shows how modern humans acquired the HLA-B*73 allele in west Asia through admixture with archaic humans called Denisovans, a likely sister group to the Neandertals. Virtual genotyping of Denisovan and Neandertal genomes identified archaic HLA haplotypes carrying functionally distinctive alleles that have introgressed into modern Eurasian and Oceanian populations. These alleles, of which several encode unique or strong ligands for natural killer cell receptors, now represent more than half the HLA alleles of modern Eurasians and also appear to have been later introduced into Africans. Thus, adaptive introgression of archaic alleles has significantly shaped modern human immune systems.
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| 2. |
- Babrzadeh, Farbod, et al.
(författare)
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Whole-genome sequencing of the efficient industrial fuel-ethanol fermentative Saccharomyces cerevisiae strain CAT-1
- 2012
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Ingår i: Molecular Genetics and Genomics. - : Springer Science and Business Media LLC. - 1617-4615 .- 1617-4623. ; 287:6, s. 485-494
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Tidskriftsartikel (refereegranskat)abstract
- The Saccharomyces cerevisiae strains widely used for industrial fuel-ethanol production have been developed by selection, but their underlying beneficial genetic polymorphisms remain unknown. Here, we report the draft whole-genome sequence of the S. cerevisiae strain CAT-1, which is a dominant fuel-ethanol fermentative strain from the sugarcane industry in Brazil. Our results indicate that strain CAT-1 is a highly heterozygous diploid yeast strain, and the similar to 12-Mb genome of CAT-1, when compared with the reference S228c genome, contains similar to 36,000 homozygous and similar to 30,000 heterozygous single nucleotide polymorphisms, exhibiting an uneven distribution among chromosomes due to large genomic regions of loss of heterozygosity (LOH). In total, 58 % of the 6,652 predicted protein-coding genes of the CAT-1 genome constitute different alleles when compared with the genes present in the reference S288c genome. The CAT-1 genome contains a reduced number of transposable elements, as well as several gene deletions and duplications, especially at telomeric regions, some correlated with several of the physiological characteristics of this industrial fuel-ethanol strain. Phylogenetic analyses revealed that some genes were likely associated with traits important for bioethanol production. Identifying and characterizing the allelic variations controlling traits relevant to industrial fermentation should provide the basis for a forward genetics approach for developing better fermenting yeast strains.
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| 3. |
- Eriksson, Jonas, et al.
(författare)
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Pyrosequencing (TM) technology at elevated temperature
- 2004
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 25:1, s. 20-27
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Tidskriftsartikel (refereegranskat)abstract
- To date, the Pyrosequencing(TM) technology has been performed at 28degreesC due to the low thermostability of the firefly luciferase. In this study, firefly luciferase was stabilized in the presence of glycine betaine, allowing DNA sequencing at 37degreesC. By increasing the temperature to 37degreesC, false signals due to primer-dimers and loop-structures were decreased significantly. In addition, a combination of (i) replacing the natural dGTP with 7'deaza-dGTP in the polymerase chain reaction (PCR), (ii) 1.6 m glycine betaine, and (iii) an increase of the temperature to 37degreesC enabled us to sequence a DNA template with the initial sequence 3'-ATGGCCCGGGGGGGAGCTCCA . . . 5'. Furthermore, we describe a method to analyze if a primer forms a primer-dimer with extendable 3'-ends.
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| 4. |
- Eriksson, Jonas, et al.
(författare)
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Pyrosequencing trade mark technology at elevated temperature
- 2004
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Ingår i: Electrophoresis. - : Wiley-VCH Verlagsgesellschaft. - 0173-0835 .- 1522-2683. ; 25:1, s. 20-27
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Tidskriftsartikel (refereegranskat)abstract
- To date, the Pyrosequencing trade mark technology has been performed at 28 degrees C due to the low thermostability of the firefly luciferase. In this study, firefly luciferase was stabilized in the presence of glycine betaine, allowing DNA sequencing at 37 degrees C. By increasing the temperature to 37 degrees C, false signals due to primer-dimers and loop-structures were decreased significantly. In addition, a combination of (i) replacing the natural dGTP with 7'deaza-dGTP in the polymerase chain reaction (PCR), (ii) 1.6 M glycine betaine, and (iii) an increase of the temperature to 37 degrees C enabled us to sequence a DNA template with the initial sequence 3'-ATGGCCCGGGGGGGAGCTCCA em leader 5'. Furthermore, we describe a method to analyze if a primer forms a primer-dimer with extendable 3'-ends.
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| 5. |
- Gambelunghe, G., et al.
(författare)
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Lack of association of human chemokine receptor gene polymorphisms CCR2-64I and CCR5-Delta 32 with autoimmune Addison's disease
- 2004
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Ingår i: European journal of immunogenetics. - : Wiley. - 0960-7420 .- 1365-2370. ; 31:2, s. 73-76
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Tidskriftsartikel (refereegranskat)abstract
- The attraction of leukocytes to tissues is essential for inflammation and the initiation of the autoimmune reaction. The process is controlled by chemokines, which are chemotactic cytokines. We investigated whether human chemokine receptor gene polymorphisms, namely CCR5-Delta32 and CCR2-64I, are associated with susceptibility to autoimmune Addison's disease. Genotyping was performed in 56 patients and 127 healthy controls by a new method using pyrosequencing for CCR2-64I and by polymerase chain reaction and detecting gel for CCR5-Delta32. None of the CCR2 or CCR5 alleles was found to be associated, either positively or negatively, with disease risk. Our results indicate that the CCR2-64I and CCR5-Delta32 gene polymorphisms do not play a major role in conferring genetic risk for, and/or protection against, autoimmune Addison's disease.
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| 6. |
- Ghaderi, Mehran, et al.
(författare)
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MHC2TA single nucleotide polymorphism and genetic risk for autoimmune adrenal insufficiency
- 2006
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 91:10, s. 4107-4111
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: The polymorphism of class II HLA genes modulates the genetic risk for several endocrine autoimmune diseases. The constitutive class II expression on antigen-presenting cells is under the control of the MHC class II transactivator, encoded by the MHC2TA gene, which is mapped to chromosome 16p13. The MHC2TA -168 A-->G single nucleotide polymorphism (rs3087456) has been suggested to confer susceptibility to some autoimmune diseases. DESIGN: With the aim of testing whether this MHC2TA single nucleotide polymorphism is independently associated with autoimmune Addison's disease (AAD) and/or modulates the genetic risk conferred by DRB1-DQA1-DQB1 haplotypes, we analyzed DNA samples from 128 AAD patients and 406 healthy control subjects from continental Italy. RESULTS: Frequency of allele G of MHC2TA was significantly increased among AAD patients (39% alleles), compared with 29% in healthy controls (P = 0.003). Similarly, the frequency of AG+GG genotypes was significantly higher among AAD patients than among healthy control subjects, in both a codominant (P = 0.012) and a G-dominant model (P = 0.018). Multivariate logistic regression analysis showed that MHC2TA AG+GG continued to be positively associated with genetic risk for AAD (P = 0.028, odds ratio = 1.72, 95% confidence interval = 1.06-2.78), after correction for DRB1*03-DQA1*0501-DQB1*0201, DRB1*04 (not 0403)-DQA1*0301-DQB1*0302 and DRB1*0403. Similar results were obtained when the number of G alleles was included in the model (P = 0.004; odds ratio = 1.65, 95% confidence interval = 1.17-2.32). CONCLUSIONS: Our study provides the first demonstration of the association of the polymorphism of the MHC2TA gene with genetic risk for AAD that appears to be independent from the well-known association with the polymorphism of HLA class II genes.
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| 7. |
- Gharizadeh, Baback, et al.
(författare)
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Detection of gyrA mutations associated with ciprofloxacin resistance in Neisseria gonorrhoeae by rapid and reliable pre-programmed short DNA sequencing
- 2005
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Ingår i: International Journal of Antimicrobial Agents. - : Elsevier BV. - 0924-8579 .- 1872-7913. ; 26:6, s. 486-490
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Tidskriftsartikel (refereegranskat)abstract
- Quinolone resistance is rapidly increasing in Neisseria gonorrhoeae and is posing a significant public health threat that requires constant surveillance. A rapid and reliable mutation detection assay has been developed. The assay is based on pre-programmed short DNA sequencing and is designed to detect point mutations in the gyrA gene that are highly related to ciprofloxacin resistance, i.e. in codons 91 and 95. By developing an assay based on pyrosequencing and exploiting the pre-programmed nucleotide dispensation capability of this technology, the sequence comprising the mutations will be analysed and promptly reveal whether the N. gonorrhoeae pathogen carries resistance to ciprofloxacin. A panel of 40 N. gonorrhoeae clinical isolates, of which 27 phenotypically displayed decreased susceptibility or resistance to ciprofloxacin, was used in the present study. All point mutations in the short stretch of the N. gonorrhoeae gyrA gene were easily discriminated, and the genotypic results obtained by pre-programmed sequencing were mainly in agreement with the phenotypically identified decreased susceptibility or resistance to ciprofloxacin. The new method used in the present study has the potential for rapid and reliable identification of known as well as previously unknown drug resistance mutations.
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| 8. |
- Gharizadeh, Baback, et al.
(författare)
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Identification of medically important fungi by the Pyrosequencing (TM) technology
- 2004
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Ingår i: Mycoses. - : Wiley. - 0933-7407 .- 1439-0507. ; 47:1-2, s. 29-33
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Tidskriftsartikel (refereegranskat)abstract
- The Pyrosequencing(TM) technology was used for identification of different clinically relevant fungi. The tests were performed on amplicons derived from the 18S rRNA gene using polymerase chain reaction (PCR) universal primers for amplification. Sequencing was performed up to 40 bases in a variable region with a designed general sequencing primer and the Pyrosequence data were analyzed by BLAST sequence search in the GenBank database. DNA from a total of 21 fungal specimens consisting of nine strains of clinically relevant fungi and 12 clinical specimens from patients suffering from proven invasive fungal infections were PCR-amplified and analyzed by gel electrophoresis, PCR-enzyme-linked immunosorbent assay (ELISA) and the Pyrosequencing technology. All data obtained by the Pyrosequencing technology were in agreement with the results obtained by PCR-ELISA using species/genus-specific oligonucleotides and were as well in accordance with the culture results. The results demonstrate that the Pyrosequencing method is a reproducible and reliable technique for identification of fungal pathogens.
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| 9. |
- Gharizadeh, Baback, 1967-
(författare)
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Method development and applications of Pyrosequencing technology
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability to determine nucleic acid sequences is one ofthe most important platforms for the detailed study ofbiological systems. Pyrosequencing technology is a relativelynovel DNA sequencing technique with multifaceted uniquecharacteristics, adjustable to different strategies, formatsand instrumentations. The aims of this thesis were to improvethe chemistry of the Pyrosequencing technique for increasedread-length, enhance the general sequence quality and improvethe sequencing performance for challenging templates. Improvedchemistry would enable Pyrosequencing technique to be used fornumerous applications with inherent advantages in accuracy,flexibility and parallel processing.Pyrosequencing technology, at its advent, was restricted tosequencing short stretches of DNA. The major limiting factorwas presence of an isomer of dATPaS, a substitute for thenatural dATP, which inhibited enzyme activity in thePyrosequencing chemistry. By removing this non-functionalnucleotide, we were able to achieve DNA read-lengths of up toone hundred bases, which has been a substantial accomplishmentfor performance of different applications. Furthermore, the useof a new polymerase, called Sequenase, has enabled sequencingof homopolymeric T-regions, which are challenging for thetraditional Klenow polymerase. Sequenase has markedly madepossible sequencing of such templates with synchronizedextension.The improved read-length and chemistry has enabledadditional applications, which were not possible previously.DNA sequencing is the gold standard method for microbial andvial typing. We have utilized Pyrosequencing technology foraccurate typing ofhuman papillomaviruses, and bacterial andfungal identification with promising results.Furthermore, DNA sequencing technologies are not capable oftyping of a sample harboring a multitude of species/types orunspecific amplification products. We have addressed theproblem of multiple infections/variants present in a clinicalsample by a new versatile method. The multiple sequencingprimer method is suited for detection and typing of samplesharboring different clinically important types/species(multiple infections) and unspecific amplifications, whicheliminates the need for nested PCR, stringent PCR conditionsand cloning. Furthermore, the method has proved to be usefulfor samples containing subdominant types/species, and sampleswith low PCR yield, which avoids reperforming unsuccessfulPCRs. We also introduce the sequence pattern recognition whenthere is a plurality of genotypes in the sample, whichfacilitates typing of more than one target DNA in the sample.Moreover, target specific sequencing primers could be easilytailored and adapted according to the desired applications orclinical settings based on regional prevalence ofmicroorganisms and viruses.Pyrosequencing technology has also been used forclone-checking by using preprogrammed nucleotide additionorder, EST sequencing and SNP analysis, yielding accurate andreliable results.Keywords:apyrase, bacterial identification, dATPaS, ESTsequencing, fungal identification, human papillomavirus (HPV),microbial and viral typing, multiple sequencing primer method,Pyrosequencing technology, Sequenase, single-strandedDNA-binding protein (SSB), SNP analysis
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| 10. |
- Gharizadeh, Baback, et al.
(författare)
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Methodological improvements of pyrosequencing technology
- 2006
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 124:3, s. 504-511
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Tidskriftsartikel (refereegranskat)abstract
- Pyrosequencing technology is a rather novel DNA sequencing method based on the sequencing-by-synthesis principle. This bioluminometric, real-time DNA sequencing technique employs a cascade of four enzymatic reactions producing sequence peak signals. The method has been proven highly suitable for single nucleotide polymorphism analysis and sequencing of short stretches of DNA. Although the pyrosequencing procedure is relatively straightforward, users may face challenges due to varying parameters in PCR and sequencing primer design, sample preparation and nucleotide dispensation; such challenges are labor and cost intensive. In this study, these issues have been addressed to increase signal quality and assure sequence accuracy.
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| 11. |
- Gharizadeh, Baback, et al.
(författare)
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Multiple group-specific sequencing primers for reliable and rapid DNA sequencing
- 2003
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Ingår i: Molecular and Cellular Probes. - 0890-8508 .- 1096-1194. ; 17:4, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- Pyrosequencing™ technology is a bioluminometric DNA sequencing method that employs a cascade of four enzymes to deliver sequence signals. To date this technology has been limited to the sequencing of short stretches of DNA. As an improvement to this technique, we have introduced a bacterial group-specific, multiple sequencing primer approach that circumvents sequencing of less informative semi-conservative regions of the 16S rRNA gene. This new approach is suitable for challenging templates, improving sequence data quality, avoiding sequencing of non-specific amplification products, lessening sequencing time, and moreover, this strategy should open the way for many new applications in the future. The group-specific, multiple sequencing primers can be applied in the Sanger dideoxy sequencing method as well. In addition, we have improved the chemistry of the Pyrosequencing system enabling sequencing of longer stretches of DNA, which allows numerous new applications.
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| 12. |
- Gharizadeh, Baback, et al.
(författare)
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Sentinel-base DNA genotyping using multiple sequencing primers for high-risk human papillomaviruses
- 2006
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Ingår i: Mol Cell Probes. - : Elsevier BV. ; 20:3-4, s. 230-238
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Tidskriftsartikel (refereegranskat)abstract
- Despite the various technologies in place for genotyping human papillomaviruses (HPV), clinical use and clinical research demand a method that is fast, more reliable and cost-effective. The technology described here represents a breakthrough development in that direction. By combining the method of multiple sequencing primers with DNA sequencing, we have developed a rapid assay for genotyping HPV that relies on the identification of a single, type-specific 'sentinel' base. As described here, the prototype assay has been developed to recognize the 12 most high-risk HPV types (HPV-16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59) and is capable of recognizing and simultaneously genotyping multiple HPV co-infections. By providing sequence information on multiple HPV infections, this method eliminates the need for labor- and cost-intensive PCR cloning. These proof-of-concept studies establish the assay to be accurate, reliable, rapid, flexible, and cost-effective, providing evidence of the feasibility this technique for use in clinical settings.
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| 13. |
- Gharizadeh, Baback, et al.
(författare)
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Viral and microbial genotyping by a combination of multiplex competitive hybridization and specific extension followed by hybridization to generic tag arrays
- 2003
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 31:22, s. e146-
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Tidskriftsartikel (refereegranskat)abstract
- Detection and identification of microbial pathogens are important for disease diagnosis, treatment and prophylaxis measurements. By introducing an innovative technique, we show a robust, reliable and accurate microarray-based method for identification of microbial pathogens. The technique utilizes a unique combination of multiplex competitive hybridization, which enhances hybridization accuracy of oligonucleotides to the specific target, and apyrase-mediated allele-specific extension, which improves specific extension. As a model system, different clinically relevant human papillomaviruses were selected for this study. The method generated accurate results and proves to be promising for specific and correct microbial and viral typing.
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| 14. |
- Gottlieb, Bruce, et al.
(författare)
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Making Sense of Intratumor Genetic Heterogeneity : Altered Frequency of Androgen Receptor CAG Repeat Length Variants in Breast Cancer Tissues
- 2013
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 34:4, s. 610-618
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Tidskriftsartikel (refereegranskat)abstract
- To examine the significance of intratumor genetic heterogeneity (ITGH) of the androgen receptor (AR) gene in breast cancer, patient-matched samples of laser capture microdissected breast tumor cells, adjacent normal breast epithelia cells, and peripheral blood leukocytes were sequenced using a novel next generation sequencing protocol. This protocol measured the frequency of distribution of a variable AR CAG repeat length, a functional polymorphism associated with breast cancer risk. All samples exhibited some degree of ITGH with up to 30 CAG repeat length variants identified. Each type of tissue exhibited a different distribution profile of CAG repeat lengths with substantial differences in the frequencies of zero and 1825 CAG AR variants. Tissue differences in the frequency of ARs with each of these CAG repeat lengths were significant as measured by paired, twin t-tests. These results suggest that preferential selection of 1825 CAG repeat length variants in breast tumors may be associated with breast cancer, and support the observation that shorter CAG repeats may protect against breast cancer. They also suggest that merely identifying variant genes will be insufficient to determine the critical mutational events of oncogenesis, which will require measuring the frequency of distribution of mutations within cancerous and matching normal tissues.
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| 15. |
- Käller, Max, et al.
(författare)
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Tag-array based HPV genotyping by competitive hybridization and extension
- 2005
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Ingår i: Journal of Virological Methods. - : Elsevier BV. - 0166-0934 .- 1879-0984. ; 129:2, s. 102-112
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Tidskriftsartikel (refereegranskat)abstract
- A method is described for HPV genotyping based on multiplex competitive hybridization (MUCH) combined with apyrase mediated allele-specific extension (AMASE). Two type-specific oligonucleotides were designed for each of the 23 investigated HPV types and directed towards two highly inter-type heterogeneous regions. The type-specific oligonucleotides were allowed to compete in the hybridization to an immobilized template resulting in a highly specific hybridization process. To increase further the specificity, a second step of type discrimination was used in which specific extension of 3'-termini matched oligonucleotides was performed. The 46 type-specific oligonucleotides each had a unique tag sequence to allow detection via an array of oligonucleotides complementary to the tags. To evaluate the genotyping assay, a total of 92 HPV positive samples were tested in this study. Twelve had double infections and five had three to five coexisting HPV types. The results show that MUCH-AMASE can readily detect multiple infections, whereas conventional dideoxy sequencing resulted in ambiguous sequence. Four samples with three to five genotypes detected were cloned and individual clones were sequenced. The cloning procedure verified the MUCH-AMASE results with indications that we can find minor infections (< 2% relative amounts). We can thus conclude that the developed assay is highly sensitive, with improved throughput and with excellent possibility to detect multiple infections.
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| 16. |
- Laytragoon-Lewin, Nongnit, et al.
(författare)
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Human papillomavirus (HPV), DNA aberrations and cell cycle progression in anal squamous cell carcinoma patients
- 2007
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Ingår i: Anticancer Research. - 0250-7005 .- 1791-7530. ; 27:6C, s. 4473-4479
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Tidskriftsartikel (refereegranskat)abstract
- Human papillomavirus (HP) infections of the genital tract are sexually transmitted and prevalent worldwide. In this study, the role of HPV in 72 patients with anal squamous cell carcinoma was investigated. Patients and Methods: Polymerase chain reaction (PCR) in combination with in situ hybridization was used to identify HPV-DNA in the patients biopsies. The HPV typing was conducted by pyrosequencing. Cell cycle and DNA content were analysed by cytometry. Results: Ninety percent of the carcinoma biopsies carried high-risk oncogenic HPV in their malignant cells. Eighty-one percent of these demonstrated a single infection with HPV16, 18 or 33 and 19% were double infected with HPV16 and HPV18 Accumulations of viral genes were seen at the necrotic area of the tumours. The HPV genome in the tumour cell influenced significant the host cell cycle progression, but not DNA aberrations. Within these patients, HPV status in the malignant cells was not found to be associated with patient survival time. Conclusion: High-risk oncogenic HPV may play an important role in the initiation of host cell proliferation in anal squamous cell carcinoma. However, infection with HPV may not have any direct influence itself on the clinical outcome of these patients considering the treatments currently available.
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| 17. |
- Lindbäck, Emma, et al.
(författare)
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Pyrosequencing of the DNA gyrase gene in Neisseria species : effective indicator of ciprofloxacin resistance in Neisseria gonorrhoeae
- 2006
-
Ingår i: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS). - : Wiley. - 0903-4641 .- 1600-0463. ; 114:12, s. 837-841
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Tidskriftsartikel (refereegranskat)abstract
- The quinolone resistance determining region (QRDR) of the gyrA gene in ciprofloxacin-susceptible strains (n=53) and strains of Neisseria spp. with reduced susceptibility (n=70) was determined by the pyrosequencing method. Results showed that the QRDR of the gyrA gene is an effective molecular indicator of resistance to ciprofloxacin in Neisseria gonorrhoeae, and presumably in Neisseria meningitidis, but not in all other Neisseria spp. This sequence was not unique for N. gonorrhoeae and seems unsuitable for species verification of N. gonorrhoeae. However, whether it is also possible to use this region for verification depends on the specificity of the primary screening method used.
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| 18. |
- Parameswaran, Poornima, et al.
(författare)
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Six RNA Viruses and Forty-One Hosts : Viral Small RNAs and Modulation of Small RNA Repertoires in Vertebrate and Invertebrate Systems
- 2010
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 6:2, s. e1000764-
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Tidskriftsartikel (refereegranskat)abstract
- We have used multiplexed high-throughput sequencing to characterize changes in small RNA populations that occur during viral infection in animal cells. Small RNA-based mechanisms such as RNA interference (RNAi) have been shown in plant and invertebrate systems to play a key role in host responses to viral infection. Although homologs of the key RNAi effector pathways are present in mammalian cells, and can launch an RNAi-mediated degradation of experimentally targeted mRNAs, any role for such responses in mammalian host-virus interactions remains to be characterized. Six different viruses were examined in 41 experimentally susceptible and resistant host systems. We identified virus-derived small RNAs (vsRNAs) from all six viruses, with total abundance varying from "vanishingly rare'' (less than 0.1% of cellular small RNA) to highly abundant (comparable to abundant micro-RNAs "miRNAs''). In addition to the appearance of vsRNAs during infection, we saw a number of specific changes in host miRNA profiles. For several infection models investigated in more detail, the RNAi and Interferon pathways modulated the abundance of vsRNAs. We also found evidence for populations of vsRNAs that exist as duplexed siRNAs with zero to three nucleotide 39 overhangs. Using populations of cells carrying a Hepatitis C replicon, we observed strand-selective loading of siRNAs onto Argonaute complexes. These experiments define vsRNAs as one possible component of the interplay between animal viruses and their hosts.
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| 19. |
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| 20. |
- Svantesson, Anna, et al.
(författare)
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A mathematical model of the Pyrosequencing reaction system
- 2004
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Ingår i: Biophysical Chemistry. - : Elsevier BV. - 0301-4622 .- 1873-4200. ; 110:02-jan, s. 129-145
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Tidskriftsartikel (refereegranskat)abstract
- The Pyrosequencing(TM) technology is a newly developed DNA sequencing method that monitors DNA nucleotide incorporation in real-time. A set of coupled enzymatic reactions, together with bioluminescence, detects incorporated nucleotides in the form of light pulses, yielding a characteristic light profile. In this study, a biochemical model of the Pyrosequencing reaction system is suggested and implemented. The model is constructed utilizing an assumption of irreversible Michaelis-Menten rate equations and a constant incorporation efficiency. The kinetic parameters are studied and values are chosen to obtain as reliable simulation results as possible. The results presented here show strong resemblance with real experiments. The model is able to capture the dynamics of a single light pulse with great accuracy, as well as the overall characteristics of a whole pyrogram(TM). The plus- and minus-shift effects observed in experiments are successfully reconstructed by two constant efficiency factors. Furthermore, pulse broadening can partly be explained by apyrase inhibition and successive dilution.
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| 21. |
- Toh, Soo Ting, et al.
(författare)
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Deep sequencing of the hepatitis B virus in hepatocellular carcinoma patients reveals enriched integration events, structural alterations and sequence variations
- 2013
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Ingår i: Carcinogenesis. - : Oxford University Press (OUP). - 0143-3334 .- 1460-2180. ; 34:4, s. 787-798
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Tidskriftsartikel (refereegranskat)abstract
- Chronic hepatitis B virus (HBV) infection is epidemiologically associated with hepatocellular carcinoma (HCC), but its role in HCC remains poorly understood due to technological limitations. In this study, we systematically characterize HBV in HCC patients. HBV sequences were enriched from 48 HCC patients using an oligo-bead-based strategy, pooled together and sequenced using the FLX-Genome-Sequencer. In the tumors, preferential integration of HBV into promoters of genes (P < 0.001) and significant enrichment of integration into chromosome 10 (P < 0.01) were observed. Integration into chromosome 10 was significantly associated with poorly differentiated tumors (P < 0.05). Notably, in the tumors, recurrent integration into the promoter of the human telomerase reverse transcriptase (TERT) gene was found to correlate with increased TERT expression. The preferred region within the HBV genome involved in integration and viral structural alteration is at the 3'-end of hepatitis B virus X protein (HBx), where viral replication/transcription initiates. Upon integration, the 3'-end of the HBx is often deleted. HBxhuman chimeric transcripts, the most common type of chimeric transcripts, can be expressed as chimeric proteins. Sequence variation resulting in non-conservative amino acid substitutions are commonly observed in HBV genome. This study highlights HBV as highly mutable in HCC patients with preferential regions within the host and virus genome for HBV integration/structural alterations.
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| 22. |
- Unemo, Magnus, et al.
(författare)
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Molecular characterization of Neisseria gonorrhoeae identifies transmission and resistance of one ciprofloxacin-resistant strain
- 2007
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Ingår i: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS). - : Wiley. - 0903-4641 .- 1600-0463. ; 115:3, s. 231-240
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Tidskriftsartikel (refereegranskat)abstract
- A highly discriminative and objective genetic characterization of N. gonorrhoeae, which increases our knowledge of strain populations in different geographic areas, is crucial for the development of improved control measures. In the present study, conventional phenotypic characterization and genetic characterization by means of pulsed-field gel electrophoresis (PFGE), sequencing of the entire porB gene, N. gonorrhoeae multiantigen sequence typing (NG-MAST), and pyrosequencing of a quinolone resistance determining region (QRDR) of the gyrA gene of Swedish ciprofloxacin-resistant N. gonorrhoeae serovar IB-10 isolates (n=45) were performed. The genetic characterization identified one widely spread ciprofloxacin-resistant N. gonorrhoeae ST147 strain. In addition, isolates with slightly different genetic characteristics, which presumably reflect the ongoing evolution only, were also identified. All the isolates contained single nucleotide polymorphisms in QRDR of the gyrA gene that are highly correlated with ciprofloxacin resistance. Consequently, comprehensive characterization identified the first confirmed large domestic transmission, mainly among young heterosexuals, of one ciprofloxacin-resistant N. gonorrhoeae strain in Swedish society during 2002-2003. In conclusion, a precise, i. e. genetic, characterization for identification of individual strains is a very valuable support to the crucial active surveillance of the epidemiological characteristics and the antibiotic susceptibility of N. gonorrhoeae in the effective treatment of gonorrhoea.
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| 23. |
- Varghese, Vici, et al.
(författare)
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Minority Variants Associated with Transmitted and Acquired HIV-1 Nonnucleoside Reverse Transcriptase Inhibitor Resistance : Implications for the Use of Second-Generation Nonnucleoside Reverse Transcriptase Inhibitors
- 2009
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Ingår i: Journal of Acquired Immune Deficiency Syndromes. - 1525-4135 .- 1944-7884. ; 52:3, s. 309-315
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: K103N, the most common nonnucleoside reverse transcriptase inhibitor (NNRTI)-resistant mutation in patients with transmitted resistance and in patients receiving a failing NNRTI-containing regimen, is fully susceptible to the new NNRTI, etravirine. Therefore, we sought to determine how often NNRTI-resistant Mutations other than K103N occur as minority variants in plasma samples for which standard genotypic resistance testing detects K103N alone. Methods: We performed ultradeep pyrosequencing (UDPS; 454 Life Sciences a Roche Company, Branford, CT) of plasma virus samples from 13 treatment-naive and 20 NNRTI-experienced patients in whom standard genotypic resistance testing revealed K103N but no other major NNRTI-resistance mutations. Results: Samples from 0 of 13 treatment-naive patients vs. 7 of 20 patients failing an NNRTI-containing regimen had minority variants with major etravirine-associated NNRTI-resistant mutations (P = 0.03, Fisher exact test): Y181C (7.0%), Y181C (3.6%) + G190A (3.2%), L1001 (14%), L100I (32%) + 190A (5.4%), K101E (3.8%) + G190A (4.9%), K101E (4.0%) + G190S (4.8%), and G190S (3.1%). Conclusions: In treatment-naive patients, UDPS did not detect additional major NNRTI-resistant mutations suggesting that etravirine may be effective in patients with transmitted K103N. In NNRTI-experienced patients, UDPS often detected additional major NNRTI-resistant mutations suggesting that etravirine may not be fully active in patients with acquired K103N.
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| 24. |
- Varghese, Vici, et al.
(författare)
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Nucleic Acid Template and the Risk of a PCR-Induced HIV-1 Drug Resistance Mutation
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:6, s. e10992-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The HIV-1 nucleoside RT inhibitor (NRTI)-resistance mutation, K65R confers intermediate to high-level resistance to the NRTIs abacavir, didanosine, emtricitabine, lamivudine, and tenofovir; and low-level resistance to stavudine. Several lines of evidence suggest that K65R is more common in HIV-1 subtype C than subtype B viruses. Methods and Findings: We performed ultra-deep pyrosequencing (UDPS) and clonal dideoxynucleotide sequencing of plasma virus samples to assess the prevalence of minority K65R variants in subtype B and C viruses from untreated individuals. Although UDPS of plasma samples from 18 subtype C and 27 subtype B viruses showed that a higher proportion of subtype C viruses contain K65R (1.04% vs. 0.25%; p < 0.001), limiting dilution clonal sequencing failed to corroborate its presence in two of the samples in which K65R was present in >1.5% of UDPS reads. We therefore performed UDPS on clones and site-directed mutants containing subtype B- and C-specific patterns of silent mutations in the conserved KKK motif encompassing RT codons 64 to 66 and found that subtype-specific nucleotide differences were responsible for increased PCR-induced K65R mutation in subtype C viruses. Conclusions: This study shows that the RT KKK nucleotide template in subtype C viruses can lead to the spurious detection of K65R by highly sensitive PCR-dependent sequencing techniques. However, the study is also consistent with the subtype C nucleotide template being inherently responsible for increased polymerization-induced K65R mutations in vivo.
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| 25. |
- Wang, Chunlin, et al.
(författare)
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High throughput sequencing reveals a complex pattern of dynamic interrelationships among human T cell subsets
- 2010
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:4, s. 1518-1523
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Tidskriftsartikel (refereegranskat)abstract
- Developing T cells face a series of cell fate choices in the thymus and in the periphery. The role of the individual T cell receptor (TCR) in determining decisions of cell fate remains unresolved. The stochastic/selection model postulates that the initial fate of the cell is independent of TCR specificity, with survival dependent on additional TCR/coreceptor "rescue" signals. The "instructive" model holds that cell fate is initiated by the interaction of the TCR with a cognate peptide-MHC complex. T cells are then segregated on the basis of TCR specificity with the aid of critical coreceptors and signal modulators [Chan S, Correia-Neves M, Benoist C, Mathis (1998) Immunol Rev 165: 195-207]. The former would predict a random representation of individual TCR across divergent T cell lineages whereas the latter would predict minimal overlap between divergent T cell subsets. To address this issue, we have used high-throughput sequencing to evaluate the TCR distribution among key T cell developmental and effector subsets from a single donor. We found numerous examples of individual subsets sharing identical TCR sequence, supporting a model of a stochastic process of cell fate determination coupled with dynamic patterns of clonal expansion of T cells bearing the same TCR sequence among both CD4(+) and CD8+ populations.
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| 26. |
- Zheng, Biying, et al.
(författare)
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Genetic polymorphism of chemokine receptors CCR2 and CCR5 in Swedish cervical cancer patients
- 2006
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Ingår i: Anticancer research. - 1791-7530. ; 26:5B, s. 3669-3674
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Tidskriftsartikel (refereegranskat)abstract
- Chemokines are chemotactic cytokines that orchestrate leukocyte trafficking in tissues, thus, playing an important role in regulation of immunological processes. The aim of this study was to investigate the association of human papillomavirus (HPV) infection and cervical cancer with two DNA polymorphisms of the chemokine receptors CCR5-Delta 32 and CCR2-64L The study material consisted of 50 cervical intraepithelial neoplasia (CIN) cases and 50 of age and sampling-date matched controls, 100 invasive cervix cancer cases and 100 of their corresponding matched disease-free controls. Pyrosequencing (TM) was employed to genotype the CCR2-64I polymorphism. CCR5-Delta 32 was genotyped using standard PCR fragment length analysis. The frequencies of CCR2 and CCR5 genotypes from 150 patients and 150 healthy controls were representative of the general population according to the Hardy-Weinberg equilibrium analysis. Risk association was computed with conditional logistic regression analysis. HPV-positive individuals with the rare CCR5 Delta 32/Delta 32 genotype have a risk of 4.58 (CI=0.40-52.64, p-valite=0.045) compare to HPV negative group. The Delta-32 mutation on the CCR locus is imperceptibly associated with increased risk of HPV infection. In total, cervical neoplasia was not associated with genetic polymorphism of CCR2 and CCR5.
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| 27. |
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