Recombinant metapneumovirus f proteins and their use

A method for generating an immune response to metapneumovirus (MPV) F protein in a subject, comprising:

• administering to the subject an effective amount of a nucleic acid molecule encoding a recombinant MPV F protein or immunogenic fragment thereof stabilized in a prefusion conformation by one or more amino acid substitutions compared to a native MPV F protein sequence, wherein the recombinant MPV F protein comprises a F2 polypeptide and a F1 ectodomain, wherein the one or more amino acid substitutions introduce one or more non-native intra- or inter-protomer disulfide bonds that, alone or in combination with other modifications, stabilize the MPV F protein in the prefusion conformation.