Fuente: WIPO "tomato" The present disclosure relates to an mRNA molecule encoding a polypeptide comprising an hMPV F protein, or an immunogenic fragment thereof, and a lumazine synthase (LuS) capable of multimerising to form a nanoparticle. Further aspects of the disclosure relate to compositions comprising the mRNA molecule and their use as a vaccine in the prevention of infectious diseases, including those caused by hMPV and RSV.