Fig 1. Design of RSV F head-only immunogens.

(A) Genetic construct of RSV F illustrating the location of the head region. The signal peptide is colored yellow, F₂ is colored blue, F₁ is colored green, the transmembrane region is colored cyan and the cytoplasmic domain is colored gray. (B) Pre-F form of the RSV F trimer. One protomer of RSV F is depicted as a ribbon diagram and colored as in A. The other two protomers are gray surface representations. Antigenic site Ø and site II are red and orange respectively. Domains I, II and III are labeled as defined previously [9, 35]. (C) Models of head-only immunogens i-273, i-693 (upper panels), i-210 and i-447 (lower panels). For each immunogen a cartoon of the genetic construct is depicted (top) and a ribbon diagram (bottom), color-coded as in A and B with brown coloring for purification tags. PDB entries 4JHW [9], 1RFO [36] and 1GCM [37] were used to depict RSV F, the foldon and the coiled coil respectively. RSV F residue numbering follows the numbering in PDB entry 4JHW [9].