Zika Virus Causes Chorioretinal Atrophy in Mouse Eyes and Infects Primary Human Cells Lining the Blood-Retinal Barrier

Abstract

Purpose : Zika virus (ZIKV) infection has been liked to cause several ocular abnormalities, including chorioretinal atrophy, maculopathy, and uveitis in both newborn and adults. Thus, it is imperative to study ZIKV pathogenesis in the eye and develop animal models to identify potential targets for interventions. We hypothesized that ZIKV gain entry into the eye by directly infecting the cells lining the blood-retinal barrier (BRB).

Methods : ZIKV (strain PRVABC59) was administered intravitreally in adult C57BL/6 and ISG15 KO mice of either sex. The development of retinal abnormalities/lesions was monitored by fundus examination up to 7 days. Viral burden in the infected eyes and/or retina were estimated using qRT PCR and immunostaining of viral envelope proteins. For in vitro studies, human primary RPE cells, ARPE19 cell line, human retinal vascular endothelial cells (HRvEC), choroidal endothelial cells (CEC), human Müller glia (MIO-M1), and mouse photoreceptor cells (661W) were challenged with ZIKV and their permissiveness was assessed by immunostaining. ZIKV-induced retinal cell death was determined by TUNEL staining and assessing cleaved caspase 3. Induction of antiviral response was measured by qRT PCR analysis of various inflammatory and type-I interferons (IFNs).

Results : ZIKV challenge caused retinal lesions in both WT and ISG15 KO mouse eyes. However, the disease severity was more in ISG15 KO mice coinciding with increased viral replication and retinal cell death. WT retina exhibited strong inflammatory and antiviral immune response as compared to the ISG15 KO mouse retina. Among the various retinal cell types, Pr. RPE and HRvEC were more permissive to ZIKV replication whereas photoreceptors were least permissive. ZIKV challenge caused retinal cell death as evidenced by increased TUNEL and Cl.casp-3 positive cells. ZIKV incited in vitro inflammatory and antiviral immune response resulting in increased expression of ZIKV entry receptors AXL, MERTK, and TYRO3. Blockade of AXL inhibited viral replication in retinal cells.

Conclusions : Together, our mouse model of direct ZIKV inoculation into the eye mimics features of ZIKV-associated retinal lesions in humans. Our data on permissive nature of BRB provides the cellular basis of potential ZIKA entry into the eye. Furthermore, our study provides the first evidence that ISG15 plays a role in retinal innate defense to ZIKV infection.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.