The model of the HCMV gB structure was generated by standard homology modelling procedures using the program MODELLER [73] , based on a sequence alignment with the template structure of HSV-1 gB [46] . Two loop regions (Val 306 to Glu 317 and Leu 439 to His 468 of HCMV gB) were not resolved in the reference structure and could therefore not be modelled. All images were generated with Accelrys DS Visualizer v2.0.1. The quality of the model was validated using ProSA [74] and PROCHECK [75] . ProSA analysis reveals that the overall model quality (Z-score = 26.22) is quite similar to that of the template crystal structure (Z-score = 27.84). Both values are within the range of z-scores typically found for crystal structures of proteins of similar size. In addition, the residue energy profiles of template and target structure are very similar indicating that the modelling did not place amino acids in an unfavourable environment. In addition, analysis of the backbone geometry shows that that 87.5% of all residues of HCMV gB are located in the most favourable regions of the Ramachandran Plot. This value corresponds to a crystal structure with 2.0-2.5 Å resolution. The HCMV gB model will be made available by the authors upon request.