The present invention refers to methods and compositions to prevent viral entry into cells expressing the CD169/sialoadhesin surface receptor by inhibiting the coupling of the sialyllactose molecule contained in the viral membrane gangliosides to the CD 169/sialoadhesin receptor. The invention also pertains to vaccine compositions based on dendritic cells loaded with an antigen of interest whereby the vaccine is provided together with a composition capable of preventing viral entry into cells expressing the CD169/sialoadhesin. Moreover, the invention relates to diagnostic and therapeutic compositions that can be specifically delivered to enveloped virions wherein the diagnostic/therapeutic agent is coupled to CD169/sialoadhesin.
