Another avian influenza VLP clinical trial (ClinicalTrials.gov: NCT00519389) reported that insect cell-derived VLPs expressing the HA, NA, and M1 proteins of H5N1 A/Indonesia/05/2005 (clade 2.1) induced antibody responses that preferentially bind to the oligomeric form of HA and the C terminus of NA, but the dose-sparing effect was not observed [59]. Here, XK is linked to avian influenza.