Publications (24)69.36 Total impact
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Article: The SnoB study: frequency of baseline raltegravir resistance mutations prevalence in different non-B subtypes
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ABSTRACT: The SnoB study analysed the variability of the integrase (IN) gene of non-B viruses from treatment-naïve patients to determine whether non-B subtypes carry natural resistance mutations to raltegravir (RAL). Plasma viral RNA from 427 patients was gained, and IN sequences were subtyped and screened for subtype-specific highly-variable residues. Seven viruses of different subtypes were phenotypically tested for RAL susceptibility; 359/427 samples could be sequenced. One hundred and seventy samples (47%) were classified as non-B subtypes. No primary RAL resistance–associated mutations (RRAMs) were detected. Certain secondary mutations were found, mostly related to specific non-B subtypes. L74M was significantly more prevalent in subtype 02_AG, T97A in A and 06_cpx, V151I in 06_cpx, and G163R in 12_BF. Various additional mutations were also detected and could be associated with the subtype too. While K156N and S230N were correlated with B subtype, V72I, L74I, T112I, T125A, V201I and T206S were more frequent in certain non-B subtypes. The resistance factors (RF) of 7 viral strains of different subtypes ranged from 1.0 to 1.9. No primary or secondary but subtype-associated additional RRAMs were present. No correlation between RF and additional RRAMs was found. The prevalence of RRAMs was higher in non-B samples. However, the RFs for the analysed non-B subtypes showed lower values to those reported relevant to clinical failure. As the role of baseline secondary and additional mutations on RAL therapy failure is actually not known, baseline IN screening is necessary. KeywordsIntegrase inhibitors–Raltegravir–Polymorphisms–Non-B subtypes–Resistance mutations–Phenotypic analysisMedical Microbiology and Immunology 04/2012; 200(4):225-232. · 3.83 Impact Factor -
Article: Endogenous or exogenous spreading of HIV-1 in Nordrhein-Westfalen, Germany, investigated by phylodynamic analysis of the RESINA Study cohort.
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ABSTRACT: HIV's genetic instability means that sequence similarity can illuminate the underlying transmission network. Previous application of such methods to samples from the United Kingdom has suggested that as many as 86% of UK infections arose outside of the country, a conclusion contrary to usual patterns of disease spread. We investigated transmission networks in the Resina cohort, a 2,747 member sample from Nordrhein-Westfalen, Germany, sequenced at therapy start. Transmission networks were determined by thresholding the pairwise genetic distance in the pol gene at 96.8% identity. At first blush the results concurred with the UK studies. Closer examination revealed four large and growing transmission networks that encompassed all major transmission groups. One of these formed a supercluster containing 71% of the sex with men (MSM) subjects when the network was thresholded at levels roughly equivalent to those used in the UK studies, though methodological differences suggest that this threshold may be too generous in the current data. Examination of the endo- versus exogenesis hypothesis by testing whether infections that were exogenous to Cologne or to Dusseldorf were endogenous to the greater region supported endogenous spread in MSM subjects and exogenous spread in the endemic transmission group. In intravenous drug using group subjects, it depended on viral strain, with subtype B sequences appearing to have origin exogenous to the Resina data, while non-B sequences (primarily subtype A) were almost completely endogenous to their local community. These results suggest that, at least in Germany, the question of endogenous versus exogenous linkages depends on subject group.Medical Microbiology and Immunology 01/2012; 201(3):259-69. · 3.83 Impact Factor -
Article: Efficacy of antiretroviral therapy switch in HIV-infected patients: a 10-year analysis of the EuResist Cohort.
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ABSTRACT: Highly active antiretroviral therapy (HAART) has been shown to be effective in many recent trials. However, there is limited data on time trends of HAART efficacy after treatment change. Data from different European cohorts were compiled within the EuResist Project. The efficacy of HAART defined by suppression of viral replication at 24 weeks after therapy switch was analyzed considering previous treatment modifications from 1999 to 2008. Results: Altogether, 12,323 treatment change episodes in 7,342 patients were included in the analysis. In 1999, HAART after treatment switch was effective in 38.0% of the patients who had previously undergone 1-5 therapies. This figure rose to 85.0% in 2008. In patients with more than 5 previous therapies, efficacy rose from 23.9 to 76.2% in the same time period. In patients with detectable viral load at therapy switch, the efficacy rose from 23.3 to 66.7% with 1-5 previous treatments and from 14.4 to 55.6% with more than 5 previous treatments. The results of this large cohort show that the outcome of HAART switch has improved considerably over the last years. This result was particularly observed in the context after viral rebound. Thus, changing HAART is no longer associated with a high risk of treatment failure.Intervirology 01/2012; 55(2):160-6. · 2.34 Impact Factor -
Article: Predicting response to antiretroviral treatment by machine learning: the EuResist project.
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ABSTRACT: For a long time, the clinical management of antiretroviral drug resistance was based on sequence analysis of the HIV genome followed by estimating drug susceptibility from the mutational pattern that was detected. The large number of anti-HIV drugs and HIV drug resistance mutations has prompted the development of computer-aided genotype interpretation systems, typically comprising rules handcrafted by experts via careful examination of in vitro and in vivo resistance data. More recently, machine learning approaches have been applied to establish data-driven engines able to indicate the most effective treatments for any patient and virus combination. Systems of this kind, currently including the Resistance Response Database Initiative and the EuResist engine, must learn from the large data sets of patient histories and can provide an objective and accurate estimate of the virological response to different antiretroviral regimens. The EuResist engine was developed by a European consortium of HIV and bioinformatics experts and compares favorably with the most commonly used genotype interpretation systems and HIV drug resistance experts. Next-generation treatment response prediction engines may valuably assist the HIV specialist in the challenging task of establishing effective regimens for patients harboring drug-resistant virus strains. The extensive collection and accurate processing of increasingly large patient data sets are eagerly awaited to further train and translate these systems from prototype engines into real-life treatment decision support tools.Intervirology 01/2012; 55(2):123-7. · 2.34 Impact Factor -
Article: Mutational patterns in the frameshift-regulating site of HIV-1 selected by protease inhibitors.
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ABSTRACT: Sustained suppression of viral replication in HIV-1 infected patients is especially hampered by the emergence of HIV-1 drug resistance. The mechanisms of drug resistance mainly involve mutations directly altering the interaction of viral enzymes and inhibitors. However, protease inhibitors do not only select for mutations in the protease but also for mutations in the precursor Gag and Pol proteins. In this study, we analysed the frameshift-regulating site of HIV-1 subtype B isolates, which also encodes for Gag and Pol proteins, classified as either treatment-naïve (TN) or protease inhibitor resistant (PI-R). HIV-1 Gag cleavage site mutations (G435E, K436N, I437V, L449F/V) especially correlated with protease inhibitor resistance mutations, but also Pol cleavage site mutations (D05G, D05S) could be assigned to specific protease resistance profiles. Additionally, two Gag non-cleavage site mutations (S440F, H441P) were observed more often in HIV-1 isolates carrying protease resistance mutations. However, in dual luciferase assays, the frameshift efficiencies of specific clones did not reveal any effect from these mutations. Nevertheless, two patterns of mutations modestly increased the frameshift rates in vitro, but were not specifically accumulating in PI-resistant HIV-1 isolates. In summary, HIV-1 Gag cleavage site mutations were dominantly selected in PI-resistant HIV-1 isolates but also Pol cleavage site mutations influenced resistance profiles in the protease. Additionally, Gag non-cleavage site mutations accumulated in PI-resistant HIV-1 isolates, but were not related to an increased frameshift efficiency.Medical Microbiology and Immunology 12/2011; 201(2):213-8. · 3.83 Impact Factor -
Article: The SnoB study: frequency of baseline raltegravir resistance mutations prevalence in different non-B subtypes.
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ABSTRACT: The SnoB study analysed the variability of the integrase (IN) gene of non-B viruses from treatment-naïve patients to determine whether non-B subtypes carry natural resistance mutations to raltegravir (RAL). Plasma viral RNA from 427 patients was gained, and IN sequences were subtyped and screened for subtype-specific highly-variable residues. Seven viruses of different subtypes were phenotypically tested for RAL susceptibility; 359/427 samples could be sequenced. One hundred and seventy samples (47%) were classified as non-B subtypes. No primary RAL resistance-associated mutations (RRAMs) were detected. Certain secondary mutations were found, mostly related to specific non-B subtypes. L74 M was significantly more prevalent in subtype 02_AG, T97A in A and 06_cpx, V151I in 06_cpx, and G163R in 12_BF. Various additional mutations were also detected and could be associated with the subtype too. While K156 N and S230 N were correlated with B subtype, V72I, L74I, T112I, T125A, V201I and T206S were more frequent in certain non-B subtypes. The resistance factors (RF) of 7 viral strains of different subtypes ranged from 1.0 to 1.9. No primary or secondary but subtype-associated additional RRAMs were present. No correlation between RF and additional RRAMs was found. The prevalence of RRAMs was higher in non-B samples. However, the RFs for the analysed non-B subtypes showed lower values to those reported relevant to clinical failure. As the role of baseline secondary and additional mutations on RAL therapy failure is actually not known, baseline IN screening is necessary.Medical Microbiology and Immunology 04/2011; 200(4):225-32. · 3.83 Impact Factor -
Article: HIV prevalence and route of transmission in Turkish immigrants living in North-Rhine Westphalia, Germany.
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ABSTRACT: The high number of Turkish immigrants in the German state North-Rhine Westphalia (NRW) compelled us to look for HIV-infected patients with Turkish nationality. In the AREVIR database, we found 127 (107 men, 20 women) Turkish HIV patients living in NRW. In order to investigate transmission clusters and their correlation to gender, nationality and self-reported transmission mode, a phylogenetic analysis including pol gene sequences was performed. Subtype distribution and the number of HIV drug resistance mutations in the Turkish patient group were found to be similar to the proportion in the non-Turkish patients. Great differences were observed in self-reported mode of transmission in the heterosexual Turkish male subgroup. Neighbour-joining tree of pol gene sequences gave indication that 59% of these reported heterosexual transmissions cluster with those of men having sex with men in the database. This is the first study analysing HIV type distribution, drug resistance mutations and transmission mode in a Turkish immigrant population.Medical Microbiology and Immunology 04/2011; 200(4):219-23. · 3.83 Impact Factor -
Article: Correction: Antiretroviral Therapy Optimisation without Genotype Resistance Testing: A Perspective on Treatment History Based Models.
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ABSTRACT: [This corrects the article on p. e13753 in vol. 5.].PLoS ONE 01/2011; 6(4). · 4.09 Impact Factor -
Article: Evolution of protease inhibitor resistance in the gag and pol genes of HIV subtype G isolates.
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ABSTRACT: To analyse HIV Gag cleavage site (CS) and non-CS mutations in HIV non-B isolates from patients failing antiretroviral therapy. Twenty-one HIV isolates were obtained from patients infected with HIV subtype G during an outbreak in Russia 20 years ago. Most patients were failing antiretroviral therapy when genotyping was performed. HIV Gag CS mutations accumulated in protease inhibitor (PI)-resistant HIV isolates and were correlated with the presence of three or more PI resistance mutations. Only 1 of 11 HIV isolates carrying major protease mutations did not harbour treatment-associated CS mutations. Natural polymorphism 453T, often found in HIV non-B subtypes, seems to favour the selection of CS mutation 453I rather than treatment-associated CS mutation 453L. Resistance-associated non-CS mutations (123E and 200I) were also observed in PI-resistant clinical isolates. Non-CS mutations in the frameshift-regulating site, which controls the synthesis of Gag-Pol, did not affect frameshift efficiency in dual luciferase assays. Of note, one of four HIV isolates from patients failing PI therapies without protease mutations harboured Gag mutations associated with PI resistance (123E and 436R) and reverse transcriptase inhibitor mutations conferring resistance to the backbone drug. HIV Gag CS mutations commonly occurred in HIV isolates from patients failing PI therapies and natural polymorphisms at the same position influence their emergence. Non-CS mutations previously associated with PI resistance were also observed in clinical isolates. Gag mutations might indicate the evolution of PI resistance even in the absence of protease mutations.Journal of Antimicrobial Chemotherapy 07/2010; 65(7):1472-6. · 5.07 Impact Factor -
Article: The evolution of protease mutation 76V is associated with protease mutation 46I and gag mutation 431V.
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ABSTRACT: Recently, first-line lopinavir failure was observed due to protease mutation 76V. In the present study, we found 76V associated with protease mutation 46I and gag cleavage-site mutation 431V. Longitudinal analysis of patients failing protease inhibitor therapies demonstrated that 76V strictly occurs either together with 46I and/or 431V or in HIV isolates already harbouring one of both mutations. Therefore, all three mutations seem to cooperate in terms of protease inhibitor resistance.AIDS (London, England) 02/2010; 24(5):779-81. · 4.91 Impact Factor -
Article: Antiretroviral therapy optimisation without genotype resistance testing: a perspective on treatment history based models.
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ABSTRACT: Although genotypic resistance testing (GRT) is recommended to guide combination antiretroviral therapy (cART), funding and/or facilities to perform GRT may not be available in low to middle income countries. Since treatment history (TH) impacts response to subsequent therapy, we investigated a set of statistical learning models to optimise cART in the absence of GRT information. The EuResist database was used to extract 8-week and 24-week treatment change episodes (TCE) with GRT and additional clinical, demographic and TH information. Random Forest (RF) classification was used to predict 8- and 24-week success, defined as undetectable HIV-1 RNA, comparing nested models including (i) GRT+TH and (ii) TH without GRT, using multiple cross-validation and area under the receiver operating characteristic curve (AUC). Virological success was achieved in 68.2% and 68.0% of TCE at 8- and 24-weeks (n = 2,831 and 2,579), respectively. RF (i) and (ii) showed comparable performances, with an average (st.dev.) AUC 0.77 (0.031) vs. 0.757 (0.035) at 8-weeks, 0.834 (0.027) vs. 0.821 (0.025) at 24-weeks. Sensitivity analyses, carried out on a data subset that included antiretroviral regimens commonly used in low to middle income countries, confirmed our findings. Training on subtype B and validation on non-B isolates resulted in a decline of performance for models (i) and (ii). Treatment history-based RF prediction models are comparable to GRT-based for classification of virological outcome. These results may be relevant for therapy optimisation in areas where availability of GRT is limited. Further investigations are required in order to account for different demographics, subtypes and different therapy switching strategies.PLoS ONE 01/2010; 5(10):e13753. · 4.09 Impact Factor -
Article: Evolution of raltegravir resistance during therapy.
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ABSTRACT: We investigated the prevalence of raltegravir resistance-associated mutations at baseline and their evolution during raltegravir therapy in patients infected with different HIV-1 subtypes. At pre-treatment screening, the integrase gene from plasma samples from patients infected with subtype B and non-B viruses was analysed. Raltegravir resistance evolution was further evaluated in 10 heavily pre-treated patients. Two hundred and nine plasma samples from 94 subtype B and 115 non-B patients were sequenced. No signature/primary raltegravir resistance mutations were detected at baseline. The secondary mutations L74M, T97A, V151I and G163R were observed with a frequency of <4%. The primary mutations N155H, Q148R/H or Q143R were observed during raltegravir therapy. The Q148R/H was detected only in subtype B. A switch of the primary mutation during raltegravir treatment was not restricted to the subtype B viruses. The prevalence of each primary mutation varied depending on the length of the raltegravir therapy. The Q148R/H was mostly detected after short exposure to raltegravir, while the Y143R was observed only after prolonged raltegravir exposure. We detected an association between the presence of the T206S in the baseline genotype and the absence of the primary Q148R/H mutation or any secondary mutation accompanying the N155H following raltegravir failure. A number of secondary and additional mutations were found in baseline genotypes. During therapy, when the virus was not optimally suppressed, resistance mutations developed, which were dependent on subtype and time on raltegravir.Journal of Antimicrobial Chemotherapy 06/2009; 64(1):25-32. · 5.07 Impact Factor -
Article: Predicting the response to combination antiretroviral therapy: retrospective validation of geno2pheno-THEO on a large clinical database.
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ABSTRACT: Expert-based genotypic interpretation systems are standard methods for guiding treatment selection for patients infected with human immunodeficiency virus type 1. We previously introduced the software pipeline geno2pheno-THEO (g2p-THEO), which on the basis of viral sequence predicts the response to treatment with a combination of antiretroviral compounds by applying methods from statistical learning and the estimated potential of the virus to escape from drug pressure. We retrospectively validated the statistical model used by g2p-THEO in approximately 7600 independent treatment-sequence pairs extracted from the EuResist integrated database, ranging from 1990 to 2007. Results were compared with the 3 most widely used expert-based interpretation systems: Stanford HIVdb, ANRS, and Rega. The difference in receiver operating characteristic curves between g2p-THEO and expert-based approaches was significant (P < .001; paired Wilcoxon test). Indeed, at 80% specificity, g2p-THEO found 16.2%-19.8% more successful regimens than did the expert-based approaches. The increased performance of g2p-THEO was confirmed in a 2001-2007 data set from which most obsolete therapies had been removed. Finding drug combinations that increase the chances of therapeutic success is the main reason for using decision support systems. The present analysis of a large data set derived from clinical practice demonstrates that g2p-THEO solves this task significantly better than state-of-the-art expert-based systems. The tool is available at http://www.geno2pheno.org.The Journal of Infectious Diseases 03/2009; 199(7):999-1006. · 6.41 Impact Factor -
Article: Investigation of expert rule bases, logistic regression, and non-linear machine learning techniques for predicting response to antiretroviral treatment.
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ABSTRACT: The extreme flexibility of the HIV type-1 (HIV-1) genome makes it challenging to build the ideal antiretroviral treatment regimen. Interpretation of HIV-1 genotypic drug resistance is evolving from rule-based systems guided by expert opinion to data-driven engines developed through machine learning methods. The aim of the study was to investigate linear and non-linear statistical learning models for classifying short-term virological outcome of antiretroviral treatment. To optimize the model, different feature selection methods were considered. Robust extra-sample error estimation and different loss functions were used to assess model performance. The results were compared with widely used rule-based genotypic interpretation systems (Stanford HIVdb, Rega and ANRS). A set of 3,143 treatment change episodes were extracted from the EuResist database. The dataset included patient demographics, treatment history and viral genotypes. A logistic regression model using high order interaction variables performed better than rule-based genotypic interpretation systems (accuracy 75.63% versus 71.74-73.89%, area under the receiver operating characteristic curve [AUC] 0.76 versus 0.68-0.70) and was equivalent to a random forest model (accuracy 76.16%, AUC 0.77). However, when rule-based genotypic interpretation systems were coupled with additional patient attributes, and the combination was provided as input to the logistic regression model, the performance increased significantly, becoming comparable to the fully data-driven methods. Patient-derived supplementary features significantly improved the accuracy of the prediction of response to treatment, both with rule-based and data-driven interpretation systems. Fully data-driven models derived from large-scale data sources show promise as antiretroviral treatment decision support tools.Antiviral therapy 02/2009; 14(3):433-42. · 3.16 Impact Factor -
Article: Advantages of predicted phenotypes and statistical learning models in inferring virological response to antiretroviral therapy from HIV genotype.
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ABSTRACT: Inferring response to antiretroviral therapy from the viral genotype alone is challenging. The utility of an intermediate step of predicting in vitro drug susceptibility is currently controversial. Here, we provide a retrospective comparison of approaches using either genotype or predicted phenotypes alone, or in combination. Treatment change episodes were extracted from two large databases from the USA (Stanford-California) and Europe (EuResistDB) comprising data from 6,706 and 13,811 patients, respectively. Response to antiretroviral treatment was dichotomized according to two definitions. Using the viral sequence and the treatment regimen as input, three expert algorithms (ANRS, Rega and HIVdb) were used to generate genotype-based encodings and VircoTYPE() 4.0 (Virco BVBA, Mechelen, Belgium) was used to generate a predicted -phenotype-based encoding. Single drug classifications were combined into a treatment score via simple summation and statistical learning using random forests. Classification performance was studied on Stanford-California data using cross-validation and, in addition, on the independent EuResistDB data. In all experiments, predicted phenotype was among the most sensitive approaches. Combining single drug classifications by statistical learning was significantly superior to unweighted summation (P<2.2x10(-16)). Classification performance could be increased further by combining predicted phenotypes and expert encodings but not by combinations of expert encodings alone. These results were confirmed on an independent test set comprising data solely from EuResistDB. This study demonstrates consistent performance advantages in utilizing predicted phenotype in most scenarios over methods based on genotype alone in inferring virological response. Moreover, all approaches under study benefit significantly from statistical learning for merging single drug classifications into treatment scores.Antiviral therapy 01/2009; 14(2):273-83. · 3.16 Impact Factor -
Article: Selecting anti-HIV therapies based on a variety of genomic and clinical factors.
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ABSTRACT: Optimizing HIV therapies is crucial since the virus rapidly develops mutations to evade drug pressure. Recent studies have shown that genotypic information might not be sufficient for the design of therapies and that other clinical and demographical factors may play a role in therapy failure. This study is designed to assess the improvement in prediction achieved when such information is taken into account. We use these factors to generate a prediction engine using a variety of machine learning methods and to determine which clinical conditions are most misleading in terms of predicting the outcome of a therapy. Three different machine learning techniques were used: generative-discriminative method, regression with derived evolutionary features, and regression with a mixture of effects. All three methods had similar performances with an area under the receiver operating characteristic curve (AUC) of 0.77. A set of three similar engines limited to genotypic information only achieved an AUC of 0.75. A straightforward combination of the three engines consistently improves the prediction, with significantly better prediction when the full set of features is employed. The combined engine improves on predictions obtained from an online state-of-the-art resistance interpretation system. Moreover, engines tend to disagree more on the outcome of failure therapies than regarding successful ones. Careful analysis of the differences between the engines revealed those mutations and drugs most closely associated with uncertainty of the therapy outcome. The combined prediction engine will be available from July 2008, see http://engine.euresist.org.Bioinformatics 08/2008; 24(13):i399-406. · 5.47 Impact Factor -
Article: Comparison of classifier fusion methods for predicting response to anti HIV-1 therapy.
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ABSTRACT: Analysis of the viral genome for drug resistance mutations is state-of-the-art for guiding treatment selection for human immunodeficiency virus type 1 (HIV-1)-infected patients. These mutations alter the structure of viral target proteins and reduce or in the worst case completely inhibit the effect of antiretroviral compounds while maintaining the ability for effective replication. Modern anti-HIV-1 regimens comprise multiple drugs in order to prevent or at least delay the development of resistance mutations. However, commonly used HIV-1 genotype interpretation systems provide only classifications for single drugs. The EuResist initiative has collected data from about 18,500 patients to train three classifiers for predicting response to combination antiretroviral therapy, given the viral genotype and further information. In this work we compare different classifier fusion methods for combining the individual classifiers. The individual classifiers yielded similar performance, and all the combination approaches considered performed equally well. The gain in performance due to combining methods did not reach statistical significance compared to the single best individual classifier on the complete training set. However, on smaller training set sizes (200 to 1,600 instances compared to 2,700) the combination significantly outperformed the individual classifiers (p<0.01; paired one-sided Wilcoxon test). Together with a consistent reduction of the standard deviation compared to the individual prediction engines this shows a more robust behavior of the combined system. Moreover, using the combined system we were able to identify a class of therapy courses that led to a consistent underestimation (about 0.05 AUC) of the system performance. Discovery of these therapy courses is a further hint for the robustness of the combined system. The combined EuResist prediction engine is freely available at http://engine.euresist.org.PLoS ONE 01/2008; 3(10):e3470. · 4.09 Impact Factor -
Article: The EuResist approach for predicting response to anti HIV-1 therapy
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Article: Sustaining lamivudine/emtricitabine, abacavir, zidovudine or atazanavir from a previous treatment shows a clinical benefit
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Article: Comparison of Classifier Fusion Methods for Predicting Response to Anti HIV-1 Therapy
PLoS ONE, v.3 (2008).
Top Journals
Institutions
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2012
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Università degli Studi di Siena
Siena, Tuscany, Italy
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2009–2012
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Universität Köln
- Institute of Virology
Köln, North Rhine-Westphalia, Germany
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2008–2012
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Max-Planck-Institut für Informatik
- Department 3: Computational Biology & Applied Algorithmics
Saarbrücken, Saarland, Germany -
IBM
Armonk, NY, USA
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