Fetal brain lesions after subcutaneous inoculation of Zika virus in a pregnant nonhuman primate

Abstract

We describe the development of fetal brain lesions after Zika virus (ZIKV) inoculation in a pregnant pigtail macaque. Periventricular lesions developed within 10 d and evolved asymmetrically in the occipital-parietal lobes. Fetal autopsy revealed ZIKV in the brain and significant cerebral white matter hypoplasia, periventricular white matter gliosis, and axonal and ependymal injury. Our observation of ZIKV-associated fetal brain lesions in a nonhuman primate provides a model for therapeutic evaluation.

Figure 1. Fetal Biometry and Ultrasound of the Fetal Brain

Fetal biometry demonstrates a lag in BPD growth (A) in contrast to continued growth of the femur length (B). An area of linear heterogeneity (arrow) developed in the fetal brain adjacent to the lateral ventricle in the posterior right brain (C). Note the choroid plexus in the lateral ventricle (*) and falx (arrowheads).

Figure 2. Serial Fetal Brain MRI Imaging

Serial MRI images of the fetal brain over time from 10 to 43 days post-inoculation (129 to 162 days gestation) demonstrate a bilateral periventricular T2 hyperintense foci that evolves over time with concomitant loss of volume in the posterior brain.

Figure 3. Neuropathology of the ZIKV Infected Fetus and Control

In contrast with sections from similar regions of a two-week younger control brain (A, C, E, G), the occipital cortex of the ZIKV-infected fetus (B, D, F, H) showed marked white matter hypoplasia and gliosis (pink bands indicated by asterisks). Gliosis in the deep white matter corresponded to abundant reactive astrocytes (D, F versus C, E) with increased GFAP immunoreactivity (H versus G). Axonal spheroids, a marker of severe axon injury, were seen only in the ZIKV fetus; the spheroids were confirmed to express neurofilament protein (F, inset).

Figure 4. ZIKV RNA and Proteins in Fetal Tissues

ZIKV RNA levels were measured by a Taqman qRT-PCR assay and calculated as mean viral copy number per mg of tissue using a standard curve (analyzed in triplicate; A). Error bars reflect standard deviation in technical replicates. Confocal fluorescent microscopy was performed on fetal brain sections stained with a primary antibody against the Zika virus E protein (B) and with secondary antibody alone (C). Nuclei were counterstained with DAPI (blue). All images are at the same scale.