FIG 7.

Immunogenicity of AMC009 and AMC011 SOSIP trimers in rabbits. (A) Immunization schedule. Four groups of rabbits (n = 5) were immunized at weeks 0, 4, 20, and 36 (black arrows) with either SOSIP.v4.2 (first three doses) or SOSIP.v5.2 (final dose). Sera were obtained at weeks 0, 4, 6, 12, 20, 22, 36, and 38 (red arrows). In the monovalent immunogen groups, the animals received 22 μg of trimer per dose. Two trivalent combinations were also tested: in the low-dose group the animals received 7.3 μg of each trimer, 22 μg in total; in the high-dose group 22 μg of each trimer was given, 66 μg in total. The AMC008 SOSIP.v4.2 trimer was not used in this experiment, but historical neutralization data from the week 22 time point are plotted for comparison for panels C and E (19). (B) Antibody-binding titers (50% effective concentration [EC₅₀]) against His-tagged AMC009 SOSIP.v5.2, AMC011 SOSIP.v5.2, and AMC008 SOSIP.v4.2 trimers were measured by Ni-NTA ELISA. The mean EC₅₀ values are plotted with the standard deviations shown. (C) Autologous neutralization titers (ID₅₀) in week 38 sera. One virus was tested for the monovalent immunogen groups, all three for the trivalent groups. The AMC009 and AMC011 viruses are tier 2, and AMC008 is tier 1B. Historical week 22 ID₅₀ values of BG505 SOSIP.v5.2 and B41 SOSIP.v4.1 immunized animals are plotted for comparison with the monovalent groups (31). (D) Heterologous neutralization titers (ID₅₀) in week 38 sera against 16 tier 2 viruses, including nine viruses of the global virus panel (82). (E) Neutralization titers (ID₅₀) against four heterologous tier 2 viruses and the parental AMC011 virus at week 38. Circled are the serum-virus combinations used for the EM-based polyclonal epitope mapping analysis in Fig. 9B. The dashed line indicates the lower assay cutoff ID₅₀ value of 20, and the horizontal black line shows the median titer per group. Indicated are the statistical significances. Individual ID₅₀ values are reported in Table S1 in the supplemental material.