Bacterial neuraminidase diminishes the enhancement of hemagglutination inhibition activity of saliva by zanamivir.

<p>Two-fold serial dilutions (25 µl) of a saliva sample was mixed with an equal volume of A/Udorn/72, B/Johonnesburg/99 and B/Kyoto/KU37/2011 virus suspensions (8 HAU/ml) containing zanamivir (+ Zanamivir, 500 nM) with or without <i>Vibrio cholerae</i> RDE (+ <i>V.c</i> RDE, 150 µunits/ml neuraminidase activity) and incubated at 37°C for 60 min. Then 50 µl of 0.5% chicken red blood cells was added, incubated at 4°C for 60 min, and hemagglutination was read. HI titers are reciprocals of the highest dilution of samples that inhibited hemagglutination.