FANCB and influenza: To confirm this result, the WT C05 Fab, which contained an Ala at position 100d, and three C05 Fab variants with a Ser at position 100d (VPGSGW, VVSSGW and VTGSGW), which had the highest affinity against SI06 H1 HA, were expressed in insect cells, purified and their affinities against HA from a panel of human influenza strains were measured.