Quantification and statistical analysis

Technical and biological replicates are indicated in the methods and figure legends. Error bars in figures represent SD. Statistical analyses were performed using Prism v8 (GraphPad).

ELISA fluorescence values were normalized to a percentage of maximal binding determined from a control well without an irrelevant prior competing mAb added. The Pearson correlation of each biotinylated mAb to each other biotinylated mAb was calculated using the median inhibition percentage from three different experiments using the corr method of the Pandas Python package (58). Hierarchical clustering was then performed on these Pearson correlations using clustermap from the Seaborn Python package. The clustering information was exported in newick format and imported into Interactive Tree of Life v4 (59), which was used to display the hierarchically clustered heatmap before importation into Excel (Microsoft) for final display.

EC₅₀ values for mAb binding were determined after log transformation of antibody concentration using four-parameter sigmoidal dose-response nonlinear regression analysis constrained to a bottom value of zero and top value less than the maximal fluorescent value of the mAb with the highest saturation fluorescence value.

MAb IC₅₀ values were calculated using a formula based on the Spearman-Kärber equation (36). Viral titers in murine plasma and lungs were compared using a one-way analysis of variance (ANOVA) and Dunnett’s multiple comparisons test, with a single pooled variance. A value of P < 0.05 was considered significant.

For each cytokine/chemokine, the concentrations from treated mice were compared with placebo-treated mice using a Brown-Forsythe one-way ANOVA test and Dunnett’s T3 multiple comparisons test, with individual variances computed for each comparison. This analysis was chosen because we did not assume equal standard deviations for each measurement.

Survival curves were generated using the Kaplan-Meier method and curves compared using the log-rank test (Mantel-Cox). Neurologic scores were compared using a chi-square test.