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- Johansson, Susanne, 1977-
(författare)
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Design and Synthesis of Sialic Acid Conjugates as Inhibitors of EKC-causing Adenoviruses
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The combat against viral diseases has been, and still is, a major challenge in the field of drug development. Viruses are intracellular parasites that use the host cell ma-chinery for their replication and release. Therefore it is difficult to target and destroy the viral particle without disturbing the essential functions of the host cell. This thesis describes studies towards antiviral agents targeting adenovirus type 37 (Ad37), which causes the severe ocular infection epidemic keratoconjunctivitis (EKC). Cell surface oligosaccharides serve as cellular receptors for many pathogens, including viruses and bacteria. For EKC-causing adenoviruses, cell surface oligo-saccharides with terminal sialic acid have recently been shown to be critical for their attachment to and infection of host cells. The work in this thesis support these re-sults and identifies the minimal binding epitope for viral recognition. As carbo-hydrate–protein interactions in general, the sialic acid–Ad37 interaction is very weak. Nature overcomes this problem and vastly improves the binding affinity by presenting the carbohydrates in a multivalent fashion. Adenoviruses interact with their cellular receptors via multiple fiber proteins, whereby it is likely that the ideal inhibitor of adenoviral infections should be multivalent. This thesis includes design and synthesis of multivalent sialic acid glycoconjugates that mimic the structure of the cellular receptor in order to inhibit adenoviral attachment to and infection of human corneal epithelial (HCE) cells. Synthetic routes to three different classes of sialic acid conjugates, i.e. derivatives of sialic acid, 3’-sialyllactose and N-acyl modified sialic acids, and their multivalent counterparts on human serum albumine (HSA) have been developed. Evaluation of these conjugates in cell binding and cell infectivity assays revealed that they are effective as inhibitors. Moreover the results verify the hypothesis of the multivalency effect and clearly shows that the power of inhibition is significantly increased with higher orders of valency. Potential inhibi-tors could easily be transferred to the eye using a salve or eye drops, and thereby they would escape the metabolic processes of the body, a major drawback of using carbohydrates as drugs. The results herein could therefore be useful in efforts to develop an antiviral drug for treatment of EKC.
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| 2. |
- Saleeb, Michael, 1985-
(författare)
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Towards novel antibacterials : Synthesis and identification of natural product inspired inhibitors of Chlamydia trachomatis and development of chemical probes targeting virulence of Pseudomonas aeruginosa
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antibiotic resistance has evolved significantly to become one of the serious threats to public health today. Yet, the pipeline of new antibiotics is drying up and is lagging behind the challenging needs. As a contribution to this recurrent need for novel antibacterials, we applied multidisciplinary strategies to identify small-molecule antibacterials against Chlamydia trachomatis and antivirulence agents against Pseudomonas aeruginosa infections. These strategies included:1. Synthesis of a focused compounds library inspired by natural product scaffolds followed by phenotypic screening against Chlamydia trachomatis. (Paper I)(-)-Hopeaphenol is a polyphenol natural product that was identified as an antivirulence agent against Y. pseudotuberculosis and P. aeruginosa. Hopeaphenol core scaffold, 2,3-diaryl-2,3-dihydrobenzofuran, is ubiquitous in polyphenolic phytochemicals. In this thesis, a focused library of forty-eight compounds was synthesized based on 2,3-diarylbenzofuran and 2,3-diaryl-2,3- dihydrobenzofuran. The library was then explored for antibacterial properties in a number of screening assays and resulted in five novel antichlamydial compounds with inhibition potency down to sub-micromolar. The identified molecules also inhibited the growth of different clinical presentations of C. trachomatis, one of the most common sexually transmitted disease worldwide.2. Target-based screening against the P. aeruginosa virulence factor using enzymatic and biophysical assays. (Paper II-IV)P. aeruginosa is a Gram-negative opportunistic pathogen with remarkable antibiotic resistance that is associated with a wide range of clinical infections. An alternative strategy to develop novel and selective antibacterials is to target the bacterial virulence factors, i.e. the ability of the bacteria to promote disease, thus ‘disarming’ the pathogens instead of killing them. P. aeruginosa employs its virulence factor, the type III secretion system (T3SS), to inject toxins (e.g. ExoS) into the eukaryotic cytosol. In one part of this thesis, we utilized enzymatic assay and identified inhibitors against the P. aeruginosa T3S toxin (ExoS). A follow up structure-activity relationship analysis was established and resulted in five (low micromolar) inhibitors of ExoS ADP-ribosylation enzymatic activity. In another part, we used surface plasmon resonance biophysical assay and identified small molecule binders of T3S translocation protein (PcrV). The primary SAR analysis was established and showed the antivirulence properties of these molecules and the potential to expand them further as novel antibacterials.
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