Figure 1.

Kinetic changes of IgG antibody responses against S1 antigen of MERS-CoV in 70 participants from 12 to 36 months after symptom onset. A, Collected sera were tested by a commercial ELISA kit. The assay was semi-quantitatively evaluated by calculating a ratio of the extinction value of the patient sample over the extinction value of the calibrator. Optical density (OD) ratios < 0.7 were considered negative, ratios > 1.4 (dashed line) were considered positive, and ratios ≥ 0.7 and ≤ 1.4 were considered as intermediate. B, Relative proportion of sera with negative, positive, and intermediate OD ratio values is presented in clinical severity groups (GI ~ GIII) at the indicated time points (G-I: n = 9 ~ 18, G-II: n = 20 ~ 33, and G-III: n = 12 ~ 18). Abbreviations: IgG, immunoglobulin G; MERS-CoV, Middle East respiratory syndrome coronavirus.