FIG 1.

A ZIKV mutant arose or increased in frequency in six pregnant rhesus macaques inoculated with two different ZIKV strains via two routes. Experimental design for inoculation of pregnant rhesus macaques with 1 × 10⁵ ZIKV WT (a 2015 Brazilian strain [GenBank accession number KU321639.1]) both intravenously (i.v.) and intra-amniotically (i.a.) (blue circle) or 1 × 10³ of ZIKV Puerto Rico 2015 (GenBank accession number KU501215.1) delivered subcutaneously (s.c.) (blue circle with a thick pink border) on the days indicated by syringes. For more details on the study design, see the work of Coffey et al. (25) and Van Rompay et al. (35). Both inocula contained mostly ZIKV M1404, where ZIKV I1404 was absent or present at the limit of detection, ∼1%. The green line shows the duration of each rhesus macaque pregnancy divided into 3 ∼55-day trimesters, where full term is 165 days. The orange dotted lines represent 165 days of gestation, and the black solid lines show the period of infection and the experiment end for each dam and its fetus. Fetal death is shown as a red X. Fetuses that survived to the study endpoint, gestation day 155, are indicated with green squares. The gold star represents the time of first detection of I1404; full genome sequencing of this specimen showed no other genome-wide mutations. The pie charts represent the relative abundance of the amino acid at position 1404. The I1404 mutation was not detected in 4 additional pregnant macaques in the same study (not shown here but included in Table S2 in the supplemental material). Table S2 shows the depth of sequencing coverage for the data represented in the pie charts. The tissues listed are maternal unless otherwise indicated.