Figure 4

C-KCE-HA/PrM-E viruses prime humoral responses. Ducks were vaccinated with PBS, 105 PFU of C-KCE or C-KCE-HA/PrM-E (n = 10 per group) subcutaneously. Sera were obtained at the indicated time points to detect the neutralization antibodies against XN/07 and df2. (A) XN/07-neutralizing antibodies were measured by neutralization assay on MDCK cells. (B) df2-neutralizing antibodies were determined by neutralization assay on BHK-21 cells. The dashed line shows the detection limit for a positive response.