Fig. 1

Protein microarray binding of hypothetical polyreactive (a) and autoreactive (b) bNAbs. Top, Protein arrays were blotted with a non-polyreactive control Ab (151K, A and B), Ab X (A) or Ab Y (B). Axis values represent the relative fluorescence signal intensity in the 151K array (y-axis) or the test Ab array (x-axis). Each dot represents an individual target protein. The diagonal line indicates equal binding by the two comparators. The dashed lines mark the cutoff for autoreactivity, set at 500-fold higher binding by the test Ab than by the control Ab. The red circle denotes an autoantigen bound ≥ 500-fold more avidly by Ab X than by the control Ab. Bottom, Histogram showing the displacement of each protein from the diagonal (top). The bin size is 0.02. Positive displacement indicates stronger binding by the test Ab than by 151K. The polyreactivity index (PI) is the Gaussian mean of all displacement values. The threshold of polyreactivity, set at PI = 0.21, is equivalent to twofold stronger overall binding by the test Ab than the control Ab