Sialic acids, influenza virus

The influenza virus inhibitors, zanamivir, and oseltamivir, act outside the cell after virus particles have been formed. The dtugs have been designed to fit into the active site of the viral envelope enzyme neuraminidase, which is required to cleave sialic acid off the surface of the producing cells. When its activity is blocked, new virus particles stay attached to the cell surface through binding of the virus protein hemagglutinin to sialic acid and are prevented from spreading to other cells. 

B neuraminidase and its complex with sialic acid. Embo J 11 49-56 Burmeister WP, Henrissat B, Bosso C, Cusack S, Ruigrok RW (1993) Influenza B virus neuraminidase can synthesize its own inhibitor. Structure 1 19-26 Calfee DP, Hayden FG (1998) New approaches to influenza chemotherapy neuraminidase inhibitors, Drugs 56 537-553... 

Matrosovich M, Klenk H-D (2003) Natural and synthetic sialic acid-containing inhibitors of influenza virus receptor binding. Rev Med Virol 13 85-97 Matrosovich MN, Matrosovich TY, Gray T, Roberts NA, Klenk H-D (2004) Neuraminidase is important for the initiation of influenza virus infection in human airway epithelium. J Virol 78 12665-12667... 

Suzuki Y, Ito T, Suzuki T, HoUand RE Jr, Chambers TM, Kiso M, Ishida H, Kawaoka Y (2000) Sialic acid species as a determinant of the host range of influenza A viruses. J Virol 74 11825-11831... 

Varghese IN, Colman PM (1991) Three-dimensional structure of the neuraminidase of influenza virus A/Tokyo/3/67 at 2.2 A resolution. 1 Mol Biol 221 473 86 Varghese IN, Laver WG, Colman PM (1983) Structure of the influenza virus glycoprotein antigen neuraminidase at 2.9 A resolution. Nature 303 35 0 Varghese IN, McKimm-Breschkin IL, Caldwell IB, Kortt AA, Colman PM (1992) The structure of the complex between influenza virus neuraminidase and sialic acid, the viral receptor. Proteins 14 327-332... 

Influenza virus particles are spheroidal and approximately 100 nm in diameter. The outer-membrane envelope contains 500 copies of hemagglutinin (HA) trimers and 100 copies of neuraminidase tetramers. The hemagglutinin constitutes the receptor sites for a-sialoside ligands. X-ray analyses show that the three sialic acid binding pockets reside 46 A apart, each trimer being separated on the virion surface by about 65-110 A [42],... 

Reichert A, Nagy JO, Spevak W, Charych D (1995) Polydiacetylene liposomes functionalized with sialic-acid bind and colorimetrically detect influenza-virus. J Am Chem Soc 117 829-830... 

For enveloped viruses such as the influenza viruses it has been shown that similar binding affinities are found for the hemagglutinin (HA) Hg-and sialic acid using either isolated HA or the whole virus [37,40] using simple H NMR titration experiments. In contrast to structural proteins of non-enveloped viruses, HA is a membrane protein and thus not as rigid as proteins as part of, e.g., icosahedral particles. For the application of STD NMR... 

N-Acetvlneuraminic Acid Aldolase. A new procedure has also been developed for the synthesis of 9-0-acetyl-N-acetylneuraminic acid using the aldolase catalyzed reaction methodology. This compound is an unusual sialic acid found in a number of tumor cells and influenza virus C glycoproteins (4 ). The aldol acceptor, 6-0-acetyl-D-mannosamine was prepared in 70% isolated yield from isopropenyl acetate and N-acetyl-D-mannosamine catalyzed by protease N from Bacillus subtilis (from Amano). The 6-0-acetyl hexose was previously prepared by a complicated chemical procedure (42.) The target molecule was obtained in 90% yield via the condensation of the 6-0-acetyl sugar and pyruvate catalyzed by NANA aldolase (Figure 6). With similar procedures applied to KDO, 2-deoxy-NANA and 2-deoxy-2-fluoro-NANA were prepared from NANA. 

Figure 12.4 Colorimetric detection of influenza virus using polymerized liposomes containing sialic acid, (a) Photograph of liposomes to which have been added increasing amounts (from left to right) of influenza virus. Liposomes were 1 and 95% 5. To each well was added the following amounts of influenza virus (left to right) 0, 8, 16, and 32 hemagglutinin units (HAU). Reprinted from Charych et al. (1996). Copyright 1996 Elsevier Science. (See color insert.)...

Polythiophenes functionalized with monosaccharides have been evaluated for their ability to detect the influenza virus and E. coli (Baek et al. 2000). Copolymers of thiophene acetic acid 10 and carbohydrate-modified thiophenes 11 have been prepared via iron(III) chloride mediated polymerization. Addition of influenza virus to a sialic acid containing copolymer resulted in a blue shift of the polymer absorption maximum, resulting in an orange to red chromatic transition. Mannose-containing polythiophenes underwent color changes upon the addition of the lectin ConA or E. coli cells that contain cell surface mannose-binding receptors. A similar biotinylated pol5hhiophene afforded a streptavidin responsive material (Paid and Leclerc 1996). 

Several ganglioside analogs containing an a-thioglycoside of sialic acid, derived for example from (29 c) (Scheme 8), have been found to be potent inhibitors of sialidase activities of different subtypes of influenza virus [64]. 

The latter approach has been followed in our laboratory. For instance, in studies related to the synthesis of potent multivalent sialoside inhibitors of influenza virus hemagglutinin [34], it became of interest to evaluate the immunogenicity of neoglycoproteins containing sialosides as sole immunodominant hapten. To this end, acetochloroneuraminic acid (1) was transformed into allyl glycoside 2 (Scheme 1) which upon reductive ozonolysis afforded aldehyde 3 in excellent overall yields [35], Reductive amination of 3 to bovine serum albumin (BSA) and tetanus toxoid provided immunogenic vaccines from which specific rabbit IgG anti-sialic acid antibodies were obtained [36]. In order... 

By carefully adjusting the distances between two sialoside residues in a number of divalent clusters. Click and Knowles [105] have obtained dimer 104 having the two sialic acid 5.7 nm apart. Compound 104 was 100-fold more potent than methyl a-sialoside (Neu5Aca2Me) in influenza virus inhibitions and 500-fold more potent in the case of polyomia virus. Alternatively, sialyl-a-(2,6)-/3-LacNAc dimers (105) branched at different positions of synthetic peptides, including compact glycine-rich and helical proline-rich peptides, afforded clusters which were only 8- and 4-fold more potent, respectively, than the corresponding monovalent trisaccharide [106]. 

This cooperative effect of several ligands at the surface of a liposome was recently demonstrated by the inhibition of agglutination of erythrocytes (natural vesicles covered with sialic acids) with the influenza virus by means of sialyl gangliosides. The lowest concentration of sialyl derivatives required for the inhibition was found to be 10 pM in solution whereas it was 20 nM at the surface of a vesicle. Actually, arrays of sialic acid at the surface of liposomes were found to be moderately more effective than sialic acid groups linked to a soluble polymer but as good or better than the best known naturd inhibitors of hemagglutination (i.e. mucins and macroglobulins) [150]. 

The internal, sialyl residue of GM, is not completely resistant to some sialidases, so long as the oligosaccharide chain is bound to the ceramide part of GM, it is slowly cleaved by C. perfringens sialidase in the presence of bile salts.77 57 3511 Surprisingly, it is a relatively good substrate for the A. ureafaciens sialidase.360 Rapid hydrolysis of GM, sialic acid has also been observed with Sendai virus sialidase, in contrast to the enzymes from NDV or influenza viruses.361 Susceptibility towards mammalian sialidases has also been reported.362 However, it... 

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