The present invention relates to compositions comprising a recombinant respiratory syncitial virus (RSV) Fusion (F) polypeptide that is stabilized in the pre-fusion conformation, wherein said RSV F polypeptide comprises at least one mutation as compared to a wild type RSV F polypeptide, wherein the at least one mutation is selected from the group consisting of: a) a mutation of the amino acid aspartic acid (D) on position 486, b) a mutation of the amino acid aspartic acid (D) on position 489, and c) a mutation of the amino acid serine (S) on position 398 and/or the amino acid lysine (K) on position 394. The invention also relate to compositions comprising an isolated nucleic acid molecule encoding said stable RSV F polypeptides.
