IFA was performed following previous protocol
Madin-Darby canine kidney (MDCK) cells were infected
with influenza virus and fixed with cold acetone-alcohol (3:2, vol/
vol). Hybridoma supernatant or purified mAb was added and
incubated at 37 "C for 30 min. After washing with phosphatebuffered
saline (PBS), goat-anti-mouse IgG conjugated with
fluorescein isothiocyanate (Sigma-Aldrich, USA) was added and
incubated at 37 "C for 30 min. After washing with PBS, the cells
were observed under laser scanning confocal microscope