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. 2016 Jun 23;12(6):e1005692. doi: 10.1371/journal.ppat.1005692

Fig 3. Two-epitope EMM.

Fig 3

Panel A: A schematic for the two-epitope EMM. The HA antigen has two epitopes: X on the head and S on the stem. Binding of antibodies specific for these epitopes masks them and masked epitope is indicated by O. Panel B-D: We plot for the two-epitope model how pre-existing antibody to the stem of HA, A S, affects boosting (fold increase) in the antibody to both the head (A X) and the stem (A S) of HA following immunization. In the basic model (Panel B) boosting is independent of the level of pre-existing antibody. In the ACM (Panel C) prevaccination antibody to the stem clears the antigen and causes an equal reduction in boosting of antibodies to both the head and stem of HA. In the FIM (in the absence of epitope masking) (Panel D), prevaccination antibody rapidly binds antigen and these antigen-antibody complexes downregulate B cell proliferation to both epitopes. In the EMM (Panel E) pre-existing antibody to the stem masks only the stem epitope, thus reducing only the boosting of antibody to the stem of HA (and boosting of antibody to the head remains unaffected). Corresponding models equations are shown in Methods section. Parameters are in the Table 1. For ACM parameter d b is equal 3, for FIM parameter α = 0.01 and α = 0 for other models.