Figure 1. Human anti-EEEV mAbs isolated from an EEEV survivor potently neutralize Sindbis (SINV)/EEEV and WT EEEV.

(A–B) Representative neutralization curves of neutralizing human anti-EEEV mAbs (A) or Fabs (B) against SINV/EEEV. Neutralization curves of potent (left) or moderate (right) neutralizing human anti-EEEV mAbs (open squares; A) or Fab molecules (open circles; B) against SINV/EEEV with mAb (A) or Fab (B) concentration (nM) on the x-axis and % relative infectivity on the y-axis. A positive control mouse mAb, EEEV-86 (dark purple) (Kim et al., 2019), and a negative control mAb, rDENV-2D22 (black), were included.

(C) Neutralization curves of human anti-EEEV mAbs against EEEV. Neutralization curves of potent (left) or moderate (right) neutralizing human anti-EEEV mAbs (open diamonds) against EEEV with mAb concentration (nM) on the x-axis and % relative infectivity on the y-axis. A positive control mouse anti-EEEV ascites fluid, ATCC (+)ve, and a negative control mAb (black), were included.

(D) Half-maximal inhibitory concentration (IC₅₀) values (pM) for human anti-EEEV mAbs or Fabs against SINV/EEEV and mAbs against EEEV strain FL93–939. IC₅₀ values (pM) for neutralizing human anti-EEEV mAbs or Fabs against SINV/EEEV or mAbs against EEEV are indicated in the table. Neutralizing human anti-EEEV mAbs are listed in order of increasing IC₅₀ value against SINV/EEEV. IC₅₀ value in pM is indicated by the orange heat map (<33 [dark orange], 33.01 to 333 [medium orange], 333.01 to 3,333 [light orange], <10,000 [lightest orange]). Isotype is indicated as heavy chain (IgG1 or IgA1), light chain (κ or λ) as determined by antibody gene sequencing.

Data in A–B represent mean ± SD of technical triplicates and are representative of three independent focus reduction neutralization test (FRNT) experiments. Data in C represent mean ± SD of technical triplicates of a plaque reduction neutralization test (PRNT) experiment.