Individuals with a variety of conditions, including cancer, autoimmune disease, diabetes, or obesity may have metabolic dysregulation of cellular glycosylation, so that some proteins are not properly glycosylated ( 1, – 6). Glycosylation of newly synthesized proteins is an important part of cellular function in eukaryotic organisms.

Our data suggest that aberrant cellular glycosylation may increase the risk of severe influenza as a result of the increased ability of glycome-modified influenza viruses to evade the immune response. Immunization of mice with NGI-1-treated virus significantly reduced antihemagglutinin and antineuraminidase titers of total serum antibody and reduced hemagglutinin protective antibody responses.

Hemagglutinin with reduced glycan occupancy required a higher concentration of surfactant protein D (an important innate immunity respiratory tract collectin) for inhibition compared to that with normal glycan occupancy. Cells treated with NGI-1 produced morphologically unaltered viable influenza virus with sequence-neutral glycosylation changes (primarily reduced site occupancy) in the hemagglutinin and neuraminidase proteins. We transiently induced aberrant N-linked glycosylation in cultured cells with an oligosaccharyltransferase inhibitor, NGI-1. Here, we investigate the consequences of aberrant cellular glycosylation for the glycome and the biology of influenza virus. Individuals with metabolic dysregulation of cellular glycosylation often experience severe influenza disease, with a poor immune response to the virus and low vaccine efficacy. Differences between NGI-1-treated and untreated samples were not significant ( P > 0.05). Data represent the average (± SD) of the results from one representative experiment (of two total). Viral titers were assessed at the indicated time points. (c) MDCK cells with normal N-glycosylation were infected with untreated or NGI-treated MDCK cells grown with virus at MOI 0.01. (a) MDCK cell monolayers or (b) 10-day-old embryonated chicken eggs with unmodified N-glycosylation were infected with A(H3N2)2013 IAV from untreated or NGI-treated NHBE cells at MOI 0.01 (in the case of MDCK cells) or with 4 HA (in the case of embryonated chicken eggs). Virus-containing apical culture supernatants were collected 24 h postinfection, and viral titers were determined. NHBE or MDCK cell monolayers were untreated or pretreated with 10.0 μM NGI-1 1 h prior to infection with A(H3N2)2013 IAV. H3N2 IAV from NGI-1-treated cells exhibits normal growth at conditions of unmodified N-glycosylation.

Raising the Bottom by Lisa Boucher