Comparison of the neutralization profiles of the serum of donor CH0219 and MAbs CH01 and VRC-CH31 either alone or in combination. Neutralizing activity was tested on a panel of 97 Env-pseudotyped lentiviruses, which comprised tier 1 and tier 2 isolates as well as transmitted founder viruses from multiple clades. CH01 and VRC-CH31 MAbs were tested both alone and in combination at a 1:1 ratio. Monoclonal antibody activity is shown as IC50 (μg/ml) and color coded based on the following IC50 ranges: <0.1 (red), 0.1 to 1 (orange), 1.1 to 10 (bright yellow), 11 to 50 (straw yellow), and >50 (white). Serum activity is shown as ID50 titer (1/dilution). Serum neutralization resistance was defined as an ID50 titer less than 20. Concordance of neutralization between the serum and the combination of the CH01 and the VRC-CH31 MAbs is noted as follows: ✓, sensitivity to both serum and the MAb combination; ×, sensitivity to serum only; Δ, sensitivity to the MAb combination only; =, neutralization resistance to both serum and MAb combination. Part of the data for CH01 MAb alone has been previously published ().