Figure 4

Representative SPR sensorgrams corresponding to the different groups of subjects included in the study. During SPR experiments, interaction between the PCV13 molecules immobilised in the chip and the serum anti-PnPs IgG occurs, changing the refractive index at the surface of the gold film and increasing signal intensity. Response units (RU) are used to describe the increase in the signal, where 1 RU is equal to a critical angle shift of 10⁻⁴ deg. At the start of the experiment all immobilised PCV13 molecules have not been exposed to serum anti-PnPs IgGs and the RU correspond to the starting critical angle (baseline). During the association phase, serum samples are injected into the flow cell and serum anti-PnPs IgGs bind to the immobilised PCV13 molecules, increasing the signal intensity. The shape of this curve can be used to measure the rate of association. This maximum RU relates to the maximum concentration of serum anti-PnPs IgGs that specifically interact with immobilized PCV13. During the dissociation phase, serum anti-PnPs IgGs are removed from the chip by the continuous flow. The surface is regenerated at the end of the experiment and returned to the starting critical angle (baseline) to start the next experiment. *Characteristically report points of SPR sensorgram: Baseline report point refers to the value of the critical angle at the star of the experiment. Binding report point refers to the maximum level of RU obtained after serum injection.