FIG 5 .

Passive protection of mice with antiserum to ZIKV E protein. (A) Serum transfer and challenge schedule for the BALB/c passive-protection study. (B) Experimental groups. (C) Prechallenge data points. ZIKV E-specific IgG titers are expressed as MFIs of the serum pools diluted 1:10 with normal BALB/c serum, simulating IgG titers expected in vivo after i.p. injection. Postchallenge data points are GMTs (with 95% CIs) from postchallenge BALB/c serum. (D) Neutralizing titers (PRNT₅₀s) in sera from passively immunized mice 2 weeks postchallenge. The significance of differences between ZIKV PRNT₅₀ values of the mouse groups receiving high-titer, low-titer, or naive SW mouse sera and the control group were determined by using a one-way ANOVA (Prism; GraphPad Software, Inc., San Diego, CA) and then by using Tukey’s multiple comparisons. (*, P < 0.05; **, P < 0.01.)