Abstract: The present invention relates to a cyclic peptide, a conjugate comprising said cyclic peptide and a lipopeptide building block, a bundle of said conjugates, a synthetic virus-like particle comprising at least one bundle of conjugates and pharmaceutical compositions comprising the same. The present invention further relates to said cyclic peptide, said conjugate said bundle of conjugates, said synthetic virus-like particle and said pharmaceutical compositions for use as a medicament, preferably for use in a method for preventing of an infectious disease or reducing the risk of an infectious disease, more preferably for use in a method for preventing or reducing the risk of an infectious disease associated with or caused by a respiratory syncytial virus.

Abstract: The invention relates to lipopeptides consisting of a peptide chain comprising a parallel coiled-coil domain, a proline-rich peptide antigen, and a lipid moiety, all covalently linked, which aggregate to synthetic virus-like particles. Proline-rich peptide antigens considered contain negatively and positively charged amino acid, and at least 15% of the amino acids are proline. Such synthetic virus-like particles carrying proline-rich antigens derived from pneumococcal proteins are useful as vaccines against infectious diseases caused by Gram-positive bacteria such as Streptococcus pneumoniae.