A compound for vaccination of an animal comprising (i) a moiety which selectively binds to a dendritic cell in the animal but which does not naturally occur in the animal and (ii) an antigen. Typically, the moiety which selectively binds as said binds to DC-SIGN. The moiety may be HIV-1 gp 120. The compound of the invention may be used to vaccinate animals and, following vaccination, they may be distinguished from naturally infected animals.