Robin Joy Thomson

Complexity in influenza virus targeted drug design: interaction with human sialidases

With the global spread of the pandemic H1N1 and the ongoing pandemic potential of the H5N1 subtype, the influenza virus represents one of the most alarming viruses spreading worldwide. The influenza virus sialidase is an effective drug target, and a number of inhibitors are clinically effective against the virus (zanamivir, oseltamivir, peramivir). Here we report structural and biochemical studies of the human cytosolic sialidase Neu2 with influenza virus sialidase-targeting drugs and related compounds.

Unsaturated N-acetyl-D-glucosaminuronic acid glycosides as inhibitors of influenza virus sialidase

The threat of pandemic influenza is a significant concern of governments worldwide. There is a very limited and relatively expensive armament to tackle such a pandemic should it occur. This fact provides much impetus to the scientific community for the discovery of new and less expensive anti-influenza drugs. Our longstanding interest in the inhibition of influenza virus sialidase, coupled with the development of simple carbohydrates that mimic an unsaturated derivative of the enzymes naturally-occurring ligand, N-acetylneuraminic acid, has led us to investigate the development of influenza virus sialidase inhibitors based on these mimetics. We have successfully prepared a range of these compounds, in good yield, from the relatively inexpensive carbohydrate N-acetylglucosamine utilising a short synthetic procedure. We have employed a sialidase inhibition assay for biological evaluation of the target compounds and to our delight these mimetics have displayed significant inhibition of influenza virus sialidase.

Synthesis of Carbohydrates with an Anomeric Thiol Moiety for Elaboration into Metabolically Stable Thioglycosides

ABSTRACT The synthesis of thioglycosides for use as metabolically stable biological probes is an area of continued interest. This paper describes the synthesis of functionalised carbohydrates which contain an anomeric thio group. During the course of this work we have examined the most viable route into compounds such as the specifically functionalised carbohydrates 36 and 37, and have also investigated the usefulness of disulfides as protecting groups for anomeric thiols.

The design, synthesis and biological evaluation of neuraminic acid-based probes of Vibrio cholerae sialidase

Abstract A molecular modelling study using the program GRID has been used to investigate the structural requirements of a potential inhibitor binding to Vibrio cholerae sialidase. A number of favourable interactions were predicted between the sialidase and Neu2en derivatives containing hydroxyl- or halogen-substituted acyl groups on the C-5 amine. As a result of this study, a detailed analysis of the interactions of C-5-substituted Neu2en derivatives with the active site of V. cholerae sialidase was undertaken using a conformational searching routine based on molecular dynamics. Based on the results of these molecular design studies several N -acyl-Neu2en-based probes were prepared and evaluated for sialidase inhibition. As envisaged, and pleasingly, the designed compounds were found to be accommodated by the enzyme’s active site architecture, and to be strong inhibitors of V. cholerae sialidase.

Synthesis of Δ4-β-D-glucopyranosiduronic acids as mimetics of 2,3-unsaturated sialic acids for sialidase inhibition

Abstract Mimetics of Neu5Ac2en and KDN2en, based on Δ 4 -β- d -glucopyranosiduronic acids, have been synthesised. The Neu5Ac2en mimetic 5 showed inhibition of both bacterial and viral sialidases, with inhibition of the viral sialidase being comparable to that of Neu5Ac2en itself.

Saturation transfer difference (STD) 1H‐NMR experiments and in silico docking experiments to probe the binding of N‐acetylneuraminic acid and derivatives to Vibrio cholerae sialidase

Saturation transfer difference (STD) 1H NMR experiments were used to probe the epitope binding characteristics of the sialidase [EC 3.2.1.18] from the bacterium Vibrio cholerae, the causative agent of cholera. Binding preferences were investigated for N‐acetylneuraminic acid (Neu5Ac, 1), the product of the sialidase catalytic reaction, for the known sialidase inhibitor 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐glycero‐D‐galacto‐non‐2‐enoic acid (Neu5Ac2en, 2), and for the uronic acid‐based Neu5Ac2en mimetic iso‐propyl 2‐acetamido‐2,4‐dideoxy‐α‐L‐threo‐hex‐4‐enopyranosiduronic acid (3), in which the native glycerol side‐chain of Neu5Ac2en is replaced with an O‐iso‐propyl ether. The STD experiments provided evidence, supporting previous studies, that Neu5Ac (1) binds to the sialidase as the α‐anomer. Docking experiments using DOCK (version 4.0.1) revealed further information regarding the binding characteristics of the enzyme active site in complex with Neu5Ac2en (2) and the Neu5Ac2en mimetic (3), indicating an expected dominant interaction of the acetamide moiety with the protein. Proteins 2004.

Structural analysis of a designed inhibitor complexed with the hemagglutinin-neuraminidase of Newcastle disease virus

Viruses of the Paramyxoviridae family are the leading cause of respiratory disease in children. The human parainfluenza viruses (hPIV) are members of the Paramyxovirinae subfamily, which also includes mumps virus, Newcastle disease virus (NDV), Sendai virus (SV) and simian type 5 virus (SV5). On the surface of these viruses is the glycoprotein hemagglutinin-neuraminidase (HN), which is responsible for cell attachment, promotion of fusion and release of progeny virions. This multifunctional nature of HN makes it an attractive target for the development of inhibitors as a treatment for childhood respiratory diseases. Here we report the crystal structure of NDV HN in complex with a derivative of 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, Neu5Ac2en, that has a functional group designed to occupy a large conserved binding pocket around the active site. The purpose of this study was to examine the effect of a bulky hydrophobic group at the O4 position of Neu5Ac2en, given the hydrophobic nature of the binding pocket. This derivative, with a benzyl group added to the O4 position of Neu5Ac2en, has an IC50 of ∼10 μM in a neuraminidase assay against hPIV3 HN. The IC50 value of the parent compound, Neu5Ac2en, in the same assay is ∼25 μM. These results highlight the striking difference between the influenza neuraminidase and paramyxovirus HN active sites, and provide a platform for the development of improved HN inhibitors.

Imaging of influenza virus sialidase activity in living cells

Influenza virus is rich in variation and mutations. It would be very convenient for virus detection and isolation to histochemically detect viral infection regardless of variation and mutations. Here, we established a histochemical imaging assay for influenza virus sialidase activity in living cells by using a new fluorescent sialidase substrate, 2-(benzothiazol-2-yl)-4-bromophenyl 5-acetamido-3,5-dideoxy-α-D-glycero-D-galacto-2-nonulopyranosidonic acid (BTP3-Neu5Ac). The BTP3-Neu5Ac assay histochemically visualized influenza virus-infected cells regardless of viral hosts and subtypes. Influenza virus neuraminidase-expressed cells, viral focus formation, and virus-infected locations in mice lung tissues were easily, rapidly, and sensitively detected by the BTP3-Neu5Ac assay. Histochemical visualization with the BTP3-Neu5Ac assay is extremely useful for detection of influenza viruses without the need for fixation or a specific antibody. This novel assay should greatly improve the efficiency of detection, titration, and isolation of influenza viruses and might contribute to research on viral sialidase.

SYNTHESIS OF 4-SUBSTITUTED-2-ACETAMIDO-2,4-DIDEOXY-MANNOPYRANOSES USING 1,6-ANHYDRO SUGAR CHEMISTRY

Abstract The introduction of nitrogen, sulfur, and bromine substituents at C-4 of 2-acetamido-2-deoxy- d -mannopyranose has been readily achieved through opening of the 3,4-epoxide of 2-acetamido-1,6:3,4-dianhydro-2-deoxy-β- d -talopyranose.

Rapid access to uronic acid-based mimetics of Kdn2en from d-glucurono-6,3-lactone

A concise route to novel mimetics of Kdn2en, based on delta4-uronic acids, from D-glucurono-6,3-lactone is presented. Uronic acid-based mimetics in which an aliphatic ether (O-glycoside), a thioether (S-glycoside), or acetamide takes the place of the natural C-6 glycerol sidechain of the sialic acid were synthesized from the key intermediate, methyl 2,3,4-tri-O-acetyl-alpha-D-glucopyranosyluronate bromide.