FIG 4.
Interperson variation in longitudinal IgG immunological responses to SARS-CoV-2 in intensively hospitalized patients. Longitudinal serum samples from ICU-admitted patients (n = 9) were tested for IgG to SARS-CoV-2 S, RBD, and NP antigens. Curve lines are fitted for each antigen (smoothed splines with 4 knots). Corresponding RT-PCR CT values are plotted in reverse on the right axis (purple) and connected by straight lines through the mean CT value of each test. A single sample was randomly selected for each time interval bin (≤5, 6 to 10, 11 to 15, 16 to 20, and ≥21 days from symptom onset) to assay for ACE2 inhibition. Values shown in boxes above each plot are percent residual MFI values for each antigen (percentage of MFI detected with ACE2 addition compared to a no-ACE2 control). Box size indicates time interval bins. NEG, negative; POS, positive.