1. In general, human and swine viruses bind to host respiratory tract surface molecules that have an α2-6 linkage between sialic acid (Sia) and adjacent sugar molecules. Avian viruses preferentially bind to host receptors with an α2-3 linkage. Information on controlling influenza virus infection by removing Sia from the host surface is limited.
2. Lectin histochemistry was used to identify the Siaα2-6 and Siaα2-3 linkage and this lectin binding was re-examined after topical (surface) sialidase treatment. The presence of sialylated glycans in tissues was analysed using mass spectrometry. The presence of infection of human upper and lower respiratory tract tissue was tested after sialidase treatment with avian and human viruses.
3. There was a diffuse expression of Siaα2-6 throughout the upper and lower respiratory tract. Siaα2-3 varied according to site with more N-linked Siaα2-3 glycans in the upper respiratory tract and more O-linked glycans in the lower respiratory tract. Sialidase treatment was able to remove both types of glycans. Unexpectedly, the effect of desialylation was not the same in all cell lines tested.
4. Both prophylactic as well as therapeutic sialidase treatment was able to prevent infection with avian and human influenza viruses. Sialidase therapy offers a potentially useful clinical option and is now in phase II clinical trial.