Fig. 1

Design and biochemical characterization of BG505 SOSIP.664-ferritin nanoparticles. a Top: model of eight BG505 SOSIP.664 trimers (PDB: 4TVP) with gp120 subunits in blue and gp41 subunits in green, displayed on the H. Pylori ferritin nanoparticle (in violet, PDB: 3BVE), viewed down one of the threefold axes of the ferritin particle. The figure was drawn using Pymol [20]. Bottom: the BG505 SOSIP.664-gp140-ferritin construct. The hexa-arginine furin cleavage site (R6) [21], the SOS disulfide bond between gp120 and gp41 (C501–C605) [22], and the I559P substitution that facilitates trimerization [23] are indicated on the SOSIP.664 component, to which the ferritin moiety is linked via a Gly-Ser-Gly (GSG) spacer. b Coomassie-stained reducing and non-reducing SDS-PAGE (left) and BN-PAGE (right) gels comparing soluble SOSIP.664 trimers and SOSIP.664-ferritin nanoparticles. The nanoparticles were too large to enter BN-PAGE gels efficiently, but were visible at the top of the lanes (Fig. 1b, right panel, right lane). c Representative ELISA binding curves of a panel of antibodies to SOSIP.664 trimer (2.0 μg/ml) and SOSIP.664-ferritin (0.45 μg/ml) with 2G12 as loading control. d Unprocessed electron micrograph showing individual SOSIP.664-ferritin particles (indicated by arrows). Protein samples were prepared on carbon-coated copper grids. Imaging was carried out using an FEI Tecnai T12 microscope operating at 120 keV [2]. Images were collected using a Tietz TemCam-F416 CMOS camera at 1 µm defocus with an average dose of 25 electrons/Ų and a magnification of ×52,000. e 84 NS-EM 2D class averages of SOSIP.664-ferritin particles. The SOSIP.664 spikes (blue arrows) and the ferritin cage (magenta arrow) are highlighted in the top right 2D class average image