Plasma from animals (A1–A6) pre- (pre-Imm, week 0, Figure 7), and post-immunization (week 19 plasma sample, 1 week after the second protein boost, Figure 7), was tested for its ability to neutralize cellular RhIL-10 (grey bars) or RhCMVIL-10 (black bars) bioactivity, where bioactivity was measured as suppression of LPS-induced IL-12 production in rhesus PBMC. The data show the biological activity of RhIL-10 is not neutralized by plasma from animals immunized with RhCMVIL-10 M1 or M2. However, RhCMVIL-10 biological activity, except for A6, is almost completely neutralized by the same plasma sample. Percent (%) neutralization is calculated as described in Figure 7 and in the “Materials and methods” section.