Secondly, to evaluate if PN-SIA49 recognizes an epitope on the HA stem region, a competition assay on A/Puerto Rico/8/1934-HA (A/PR/8/34-HA) human epithelial kidney HEK293T transfected cells was performed between PN-SIA49 and the commercially available mouse monoclonal antibody C179 (Takara Bio inc., Otsu, Shiga, Japan), which binds to an epitope on the HA stem region [29] . The results obtained showed that PN-SIA49 completely inhibited C179 binding to the A/PR/8/34-HA ( Figure  S3 ).