Prefusion rsv f proteins and their use

A recombinant respiratory syncytial virus (RSV) F ectodomain trimer, comprising:

• three recombinant F2-F1 ectodomain protomers each comprising a deletion of RSV F positions 104-144 and a glycine-serine peptide linker between RSV F positions 103 and 145, wherein the recombinant F2-F1 ectodomain protomers comprise the following amino acid substitutions to stabilize the recombinant RSV F ectodomain trimer in a prefusion conformation:
• a non-native disulfide bond between cysteines introduced by 155C and 290C substitutions;
• 190F and 207L substitutions;
• and
• (A) a non-native inter-protomer disulfide bond between cysteines introduced by 98C and 361C substitutions;
• or
• (B) a non-native inter-protomer disulfide bond between cysteines introduced by 183GC and 428C substitutions, and an amino acid sequence set forth as residues 26-475 of SEQ ID NO:
• 2, 6, 11, 30-35, 38-39, 42-43, 46-47, 50-51, or 54-55, or residues 31-480 of SEQ ID NO:
• 16 or 21.