They were immunized intranasally with monophosphoryl lipid A (MPL),VR1012,VR1012+MPL,VR1012/Sj31,VR1012/Sj31+MPL respectively.

• A组为单磷脂 (MPL)组 ,B组为VR10 12组 ,C组VR10 12 +MPL组 ,D组为VR10 12 /Sj3 1组 ,E组为VR10 12 /Sj 3 1+MPL组。 滴鼻免疫。