Glycans as receptors for influenza pathogenesis

Influenza A viruses, members of the Orthomyxoviridae family, are responsible for annual seasonal influenza epidemics and occasional global pandemics. The binding of viral coat glycoprotein hemagglutinin (HA) to sialylated glycan receptors on host epithelial cells is the critical initial step in the infection and transmission of these viruses. Scientists believe that a switch in the binding specificity of HA from Neu5Acα2-3Gal linked (α2-3) to Neu5Acα2-6Gal linked (α2-6) glycans is essential for the crossover of the viruses from avian to human hosts. However, studies have shown that the classification of glycan binding preference of HA based on sialic acid linkage alone is insufficient to establish a correlation between receptor specificity of HA and the efficient transmission of influenza A viruses. A recent study reported extensive diversity in the structure and composition of α2-6 glycans (which goes beyond the sialic acid linkage) in human upper respiratory epithelia and identified different glycan structural topologies. Biochemical examination of the multivalent HA binding to these diverse sialylated glycan structures also demonstrated that high affinity binding of HA to α2-6 glycans with a characteristic umbrella-like structural topology is critical for efficient human adaptation and human-human transmission of influenza A viruses. This review summarizes studies which suggest a new paradigm for understanding the role of the structure of sialylated glycan receptors in influenza virus pathogenesis.National Institute of General Medical Sciences (U.S.) (Glue Grant U54 GM62116)National Institutes of Health (U.S.) (Grant GM57073)Singapore-MIT Alliance for Research and Technolog

Quantitative Bestimmung dünnschichtchromatographisch getrennter Lipide aus Serum und Gewebe durch UV-Absorptionsmessung in Remission

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Bifidus factor. V. The activity of α- and β-methyl-N-acetyl-d-glucosaminides

1. β-Methyl-N-acetyl-d-glucosaminide is a growth factor for Lactobacillus bifidus var. Penn. The corresponding α-glucoside is inactive. 2. When mixtures of the inactive α-methyl-N-acetyl-d-glucosaminide and of the active β-isomer are used, the activity of the β-isomer is enhanced up to fivefold. 3. Other compounds containing NH-CO groups did not enhance the activity of β-methyl-N-acetyl-d-glucosaminide. In general, no or only very slight enhancement by the α-glucoside was observed when the β-glucoside was replaced by other substances with bifidus factor activity. 4. Lactobacillus bifidus var. Penn contains an enzyme that hydrolyzes and inactivates β-methyl-N-acetyl-d-glucosaminide but not the corresponding α-glucoside. In the presence of the α-glucoside the rate of hydrolysis of the β-glucoside was decreased. The observed in vitro effect did not seem sufficient to explain the microbiological response

Bifidus factor. II. Its occurrence in milk from different species and in other natural products

The activity of human milk for the growth of Lactobacillus bifidus var. Penn was compared with that of other species. The average relative activity was highest for human colostrum, closely followed by rat colostrum, then by human milk, rat milk, and cow's colostrum. The milk of ruminants (cow, ewe, goat) showed only very slight activity. Somewhat higher activity was found in the milk of cat, monkey, dog, donkey, rabbit, mare, and sow. The bifidus growth factor has been demonstrated in high concentration in various secretions in man, such as saliva, semen, amniotic fluid, meconium, and tears. Hog gastric mucin which has a high blood-group titer has also shown a high titer for bifidus factor, while other nitrogencontaining polysaccharides were free or almost free of bifidus factor. Ammonium salts and N-acetylglucosamine as well as N-acetylgalactosamine, especially the ammonium salts, in high concentration, were active, probably as precursors of the growth factor