| 436081. |
- Laabei, Maisem, et al.
(författare)
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Antibacterial Fusion Proteins Enhance Moraxella catarrhalis Killing
- 2020
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Moraxella catarrhalis is a human-specific commensal of the respiratory tract and an opportunistic pathogen. It is one of the leading cause of otitis media in children and of acute exacerbations in patients with chronic obstructive pulmonary disease, resulting in significant morbidity and economic burden. Vaccines and new immunotherapeutic strategies to treat this emerging pathogen are needed. Complement is a key component of innate immunity that mediates the detection, response, and subsequent elimination of invading pathogens. Many pathogens including M. catarrhalis have evolved complement evasion mechanisms, which include the binding of human complement inhibitors such as C4b-binding protein (C4BP) and Factor H (FH). Inhibiting C4BP and FH acquisition by M. catarrhalis may provide a novel therapeutic avenue to treat infections. To achieve this, we created two chimeric proteins that combined the Moraxella-binding domains of C4BP and FH fused to human immunoglobulin Fcs: C4BP domains 1 and 2 and FH domains 6 and 7 fused to IgM and IgG Fc, respectively. As expected, FH6-7/IgG displaced FH from the bacterial surface while simultaneously activating complement via Fc-C1q interactions, together increasing pathogen elimination. C4BP1-2/IgM also increased serum killing of the bacteria through enhanced complement deposition, but did not displace C4BP from the surface of M. catarrhalis. These Fc fusion proteins could act as anti-infective immunotherapies. Many microbes bind the complement inhibitors C4BP and FH through the same domains as M. catarrhalis, therefore these Fc fusion proteins may be promising candidates as adjunctive therapy against many different drug-resistant pathogens.
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| 436082. |
- Laabei, Maisem, et al.
(författare)
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Catch Me if You Can : Streptococcus pyogenes Complement Evasion Strategies
- 2019
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Ingår i: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 11:1, s. 3-12
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Tidskriftsartikel (refereegranskat)abstract
- The human host has evolved elaborate protection mechanisms to prevent infection from the billions of microorganisms to which it host is exposed and is home. One of these systems, complement, is an evolutionary ancient arm of innate immunity essential for combatting bacterial infection. Complement permits the efficient labelling of bacteria with opsonins, supports phagocytosis, and facilitates phagocyte recruitment to the site of infection through the production of chemoattractants. However, it is by no means perfect, and certain organisms engage in an evolutionary arms race with the host where complement has become a major target to promote immune evasion. Streptococcus pyogenes is a major human pathogen that causes significant morbidity and mortality globally. S. pyogenes is also a member of an elite group of bacterial pathogens possessing a sophisticated arsenal of virulence determinants capable of interfering with complement. In this review, we focus on these complement evasins, their mechanism of action, and their importance in disease progression. Finally, we highlight new therapeutic options for fighting S. pyogenes, by interfering with one of its main mechanisms of complement evasion.
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| 436083. |
- Laabei, M., et al.
(författare)
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Predicting the virulence of MRSA from its genome sequence
- 2014
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051. ; 24:5, s. 839-849
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Tidskriftsartikel (refereegranskat)abstract
- Microbial virulence is a complex and often multifactorial phenotype, intricately linked to a pathogen's evolutionary trajectory. Toxicity, the ability to destroy host cell membranes, and adhesion, the ability to adhere to human tissues, are the major virulence factors of many bacterial pathogens, including Staphylococcus aureus. Here, we assayed the toxicity and adhesiveness of 90 MRSA (methicillin resistant S. aureus) isolates and found that while there was remarkably little variation in adhesion, toxicity varied by over an order of magnitude between isolates, suggesting different evolutionary selection pressures acting on these two traits. We performed a genome-wide association study (GWAS) and identified a large number of loci, as well as a putative network of epistatically interacting loci, that significantly associated with toxicity. Despite this apparent complexity in toxicity regulation, a predictive model based on a set of significant single nucleotide polymorphisms (SNPs) and insertion and deletions events (indels) showed a high degree of accuracy in predicting an isolate's toxicity solely from the genetic signature at these sites. Our results thus highlight the potential of using sequence data to determine clinically relevant parameters and have further implications for understanding the microbial virulence of this opportunistic pathogen.
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| 436084. |
- Laabei, Maisem, et al.
(författare)
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Short leucine-rich proteoglycans modulate complement activity and increase killing of the respiratory pathogen moraxella catarrhalis
- 2018
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 201:9, s. 2721-2730
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Tidskriftsartikel (refereegranskat)abstract
- The respiratory pathogen Moraxella catarrhalis is a human-specific commensal that frequently causes acute otitis media in children and stimulates acute exacerbations in chronic obstructive pulmonary disease patients. The exact molecular mechanisms defining host-pathogen interactions promoting pathogenesis are not clearly understood. Limited knowledge hampers vaccine and immunotherapeutic development required to treat this emerging pathogen. In this study, we reveal in detail a novel antibacterial role displayed by short leucine-rich proteoglycans (SLRPs) in concert with complement. We show that fibromodulin (FMOD), osteoadherin (OSAD), and biglycan (BGN) but not decorin (DCN) enhance serum killing of M. catarrhalis. Our results suggest that M. catarrhalis binding to SLRPs is a conserved feature, as the overwhelming majority of clinical and laboratory strains bound all four SLRPs. Furthermore, we resolve the binding mechanism responsible for this interaction and highlight the role of the ubiquitous surface protein (Usp) A2/A2H in mediating binding to host SLRPs. A conserved immune evasive strategy used by M. catarrhalis and other pathogens is the surface acquisition of host complement inhibitors such as C4b-binding protein (C4BP). We observed that FMOD, OSAD, and BGN competitively inhibit binding of C4BP to the surface of M. catarrhalis, resulting in increased C3b/iC3b deposition, membrane attack complex (MAC) formation, and subsequently decreased bacterial survival. Furthermore, both OSAD and BGN promote enhanced neutrophil killing in vitro, both in a complement-dependent and independent fashion. In summary, our results illustrate that SLRPs, FMOD, OSAD, and BGN portray complement-modulating activity enhancing M. catarrhalis killing, defining a new antibacterial role supplied by SLRPs.
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| 436085. |
- Laaber, C., et al.
(författare)
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Applying test case prioritization to software microbenchmarks
- 2021
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Ingår i: Empirical Software Engineering. - : Springer Science and Business Media LLC. - 1382-3256 .- 1573-7616. ; 26:6
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Tidskriftsartikel (refereegranskat)abstract
- Regression testing comprises techniques which are applied during software evolution to uncover faults effectively and efficiently. While regression testing is widely studied for functional tests, performance regression testing, e.g., with software microbenchmarks, is hardly investigated. Applying test case prioritization (TCP), a regression testing technique, to software microbenchmarks may help capturing large performance regressions sooner upon new versions. This may especially be beneficial for microbenchmark suites, because they take considerably longer to execute than unit test suites. However, it is unclear whether traditional unit testing TCP techniques work equally well for software microbenchmarks. In this paper, we empirically study coverage-based TCP techniques, employing total and additional greedy strategies, applied to software microbenchmarks along multiple parameterization dimensions, leading to 54 unique technique instantiations. We find that TCP techniques have a mean APFD-P (average percentage of fault-detection on performance) effectiveness between 0.54 and 0.71 and are able to capture the three largest performance changes after executing 29% to 66% of the whole microbenchmark suite. Our efficiency analysis reveals that the runtime overhead of TCP varies considerably depending on the exact parameterization. The most effective technique has an overhead of 11% of the total microbenchmark suite execution time, making TCP a viable option for performance regression testing. The results demonstrate that the total strategy is superior to the additional strategy. Finally, dynamic-coverage techniques should be favored over static-coverage techniques due to their acceptable analysis overhead; however, in settings where the time for prioritzation is limited, static-coverage techniques provide an attractive alternative.
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| 436086. |
- Laaber, C., et al.
(författare)
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Software microbenchmarking in the cloud. How bad is it really?
- 2019
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Ingår i: Empirical Software Engineering. - : Springer Science and Business Media LLC. - 1382-3256 .- 1573-7616. ; 24:4, s. 2469-2508
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Tidskriftsartikel (refereegranskat)abstract
- Rigorous performance engineering traditionally assumes measuring on bare-metal environments to control for as many confounding factors as possible. Unfortunately, some researchers and practitioners might not have access, knowledge, or funds to operate dedicated performance-testing hardware, making public clouds an attractive alternative. However, shared public cloud environments are inherently unpredictable in terms of the system performance they provide. In this study, we explore the effects of cloud environments on the variability of performance test results and to what extent slowdowns can still be reliably detected even in a public cloud. We focus on software microbenchmarks as an example of performance tests and execute extensive experiments on three different well-known public cloud services (AWS, GCE, and Azure) using three different cloud instance types per service. We also compare the results to a hosted bare-metal offering from IBM Bluemix. In total, we gathered more than 4.5 million unique microbenchmarking data points from benchmarks written in Java and Go. We find that the variability of results differs substantially between benchmarks and instance types (by a coefficient of variation from 0.03% to >100%). However, executing test and control experiments on the same instances (in randomized order) allows us to detect slowdowns of 10% or less with high confidence, using state-of-the-art statistical tests (i.e., Wilcoxon rank-sum and overlapping bootstrapped confidence intervals). Finally, our results indicate that Wilcoxon rank-sum manages to detect smaller slowdowns in cloud environments.
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| 436087. |
- Laadan, Boaz, et al.
(författare)
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Furaldehyde substrate specificity and kinetics of Saccharomyces cerevisiae alcohol dehydrogenase 1 variants
- 2014
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Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: A previously discovered mutant of Saccharomyces cerevisiae alcohol dehydrogenase 1 (Adh1p) was shown to enable a unique NADH-dependent reduction of 5-hydroxymethylfurfural (HMF), a well-known inhibitor of yeast fermentation. In the present study, site-directed mutagenesis of both native and mutated ADH1 genes was performed in order to identify the key amino acids involved in this substrate shift, resulting in Adh1p-variants with different substrate specificities. Results: In vitro activities of the Adh1p-variants using two furaldehydes, HMF and furfural, revealed that HMF reduction ability could be acquired after a single amino acid substitution (Y295C). The highest activity, however, was reached with the double mutation S110P Y295C. Kinetic characterization with both aldehydes and the in vivo primary substrate acetaldehyde also enabled to correlate the alterations in substrate affinity with the different amino acid substitutions. Conclusions: We demonstrated the key role of Y295C mutation in HMF reduction by Adh1p. We generated and kinetically characterized a group of protein variants using two furaldehyde compounds of industrial relevance. Also, we showed that there is a threshold after which higher in vitro HMF reduction activities do not correlate any more with faster in vivo rates of HMF conversion, indicating other cell limitations in the conversion of HMF.
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| 436088. |
- Laadan, Boaz, et al.
(författare)
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Identification of an NADH-dependent 5-hydroxymethylfurfural-reducing alcohol dehydrogenase in Saccharomyces cerevisiae.
- 2008
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Ingår i: Yeast. - : Wiley. - 1097-0061 .- 0749-503X. ; 25:3, s. 191-198
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Tidskriftsartikel (refereegranskat)abstract
- We report on the identification and characterization of a mutated alcohol dehydrogenase 1 from the industrial Saccharomyces cerevisiae strain TMB3000 that mediates the NADH-dependent reduction of 5-hydroxymethylfurfural (HMF) to 2,5-bis-hydroxymethylfuran. The co-factor preference distinguished this alcohol dehydrogenase from the previously reported NADPH-dependent S. cerevisiae HMF alcohol dehydrogenase Adh6. The amino acid sequence revealed three novel mutations (S109P, L116S and Y294C) that were all predicted at the vicinity of the substrate binding site, which could explain the unusual substrate specificity. Increased biomass production and HMF conversion rate were achieved in a CEN.PK S. cerevisiae strain overexpressing the mutated ADH1 gene. Copyright (c) 2008 John Wiley & Sons, Ltd.
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| 436089. |
- Laage-Hellman, Jens, 1947, et al.
(författare)
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Business creation in networks: How a technology-based start-up collaborates with customers in product development
- 2018
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Ingår i: Industrial Marketing Management. - : Elsevier BV. - 0019-8501 .- 1873-2062. ; 70, s. 13-24
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with business creation in networks by setting the focus on how technology- based start-up companies collaborate with customers in product development. The aim is to analyze the pattern of customer collaboration by using the industrial network approach as theoretical point of departure. The method consists of a process-based single case study. The focal case is Oxeon, a Swedish rapidly growing university spin-off company commercializing a new technology for making carbon fiber composites. The development of products and applications has taken place in close collaboration with their customers. The paper addresses three research issues, which are related to the timing, mutuality and organizing of the collaboration. The analysis of the Oxeon case results in identification of five crucial aspects on the management of customer collaboration: (i) the need for involving customers early, (ii) the choice of application areas, (iii) the mutual process of choosing and getting chosen as collaboration partner, (iv) the external networking role of the start-up, and (v) the internal organizing of the start-up in relation to its ambitions for external interaction with customers. The results are summarized by formulating a set of propositions that can be taken as starting point for further research.
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| 436090. |
- Laage-Hellman, Jens, 1947, et al.
(författare)
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Customer Involvement in Product Development: An Industrial Network Perspective
- 2014
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Ingår i: Journal of Business-to-Business Marketing. - 1051-712X .- 1547-0628. ; 21:4, s. 257-276
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In business markets, working with customers and users has become increasingly important to get knowledge about customer needs and to develop new products. The purpose of this article is twofold: (1) to develop a framework for analyzing customer involvement in product development in a business market context, and (2) to apply this framework to a particular company to describe and analyze how it practices customer involvement.Methodology/approach: The article takes its main theoretical starting point in the industrial network approach, but also uses other literature from the innovation and product development field. The empirical study applies a qualitative case study approach and focuses on one company in the truck business.Findings: The suggested framework deals with four key aspects of customer involvement: Why, when, how, and who. The observed pattern of the truck manufacturer shows how dealers, hauliers, and truck drivers are all part of the overall understanding of the customer. These actors are involved for different, typically very clear, purposes at different points in time through surveys, product clinics, and field testing. The pattern, referred to as mixed facilitative, is not one of close collaboration with individual customers, but one of broad involvement of several customers through business intelligence and direct involvement.Research implications: First, the article provides researchers with a framework and method for studying customer involvement in product development. Second, the case study provides an illustrative example of the customer involvement pattern pursued by a leading company in a major industry. This enhances the understanding of the focal phenomenon, leads to managerial implications, and gives ideas for future research.Practical implications: There are several managerial implications related to the why, when, how, and who questions. For example, it is pointed out that managers should consider involving customers more extensively than what seems to be common today-for example, by using customers as codevelopers, working with them throughout the entire development process (i.e., not only early and late), and including different types of users (with different requirements and wishes).Originality/value/contribution of the article: The contribution lies in the development of a framework centered on the four key questions of customer involvement in product development and using this framework for observing a pattern, and finding explanations and relating this pattern to how other firms are doing.
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