VSR recombinant antigens

An antigen recombinant respiratory syncytial virus (RSV) comprising a polypeptide of the protein soluble F comprising an F2 domain and an F1 domain of a polypeptide of the F protein of RSV, in which no cleavage site furin between F2 domain and the domain F1, and wherein the polypeptide further comprises a heterologous trimerization domain C-terminal to the domain F1.