Enhanced susceptibility of nasal polyp tissues to avian and human influenza viruses.
BACKGROUND
Influenza viruses bind and infect respiratory epithelial cells through sialic acid on cell surface. Differential preference to sialic acid types contributes to host- and tissue-tropism of avian and seasonal influenza viruses. Although the highly pathogenic avian influenza virus H5N1 can infect and cause severe diseases in humans, it is not efficient in infecting human upper respiratory tract. This is because of the scarcity of its receptor, α2,3-linked sialic acid, in human upper airway. Expression of sialic acid can be influenced by various factors including inflammatory process. Allergic rhinitis and nasal polyp are common inflammatory conditions of nasal mucosa and may affect expression of the sialic acid and susceptibility to influenza infection.


RESULTS
To test this hypothesis, we detected α2,3- and α2,6-linked sialic acid in human nasal polyp and normal nasal mucosal tissues by lectin staining and infected explants of those tissues with avian influenza viruses H5N1 and seasonal influenza viruses. We show here that mucosal surface of nasal polyp expressed higher level of α2,3- and α2,6-linked sialic acid than normal nasal mucosa. Accordingly, both H5N1 avian influenza viruses and seasonal influenza viruses replicated more efficiently in nasal polyp tissues explants.


CONCLUSIONS
Our data suggest a role of nasal inflammatory conditions in susceptibility to influenza infection, especially by avian influenza viruses, which is generally inefficient in infecting human upper airway. The increased receptor expression may contribute to increased susceptibility in some individuals. This may contribute to the gradual adaptation of the virus to human population.
Suptawiwat
Ornpreya
O
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Tantilipikorn
Pongsakorn
P
Boonarkart
Chompunuch
C
Lumyongsatien
Jate
J
Uiprasertkul
Mongkol
M
Puthavathana
Pilaipan
P
Auewarakul
Prasert
P
D004198:Disease Susceptibility; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D007251:Influenza, Human / Q000378:metabolism / Q000821:virology*; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009297:Nasal Mucosa / Q000378:metabolism / Q000821:virology; D009298:Nasal Polyps / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism
D011991:Receptors, Virus; D019158:N-Acetylneuraminic Acid