The rapid spread of Zika virus (ZIKV) and the association between ZIKV and abnormal brain development constitute a global health emergency. Zika virus (ZIKV) infection leads to a spectrum of neurologic malformations in human fetuses and sequelae in newborns, including microcephaly, meningoencephalitis, craniofacial disproportion, retinal lesions, hearing loss, convulsions, and hypotony. While microcephaly is the most recognizable and severe neurologic defect, many infants born with microcephaly also have major defects in the retina that may lead to blindness. Beyond these relatively severe cases of ZIKV infection, there is growing concern that ZIKV may cause more subtle defects in learning, socialization, or reduced sight. The cells infected in the nervous system include glial cells, astrocytes, oligodendrocytes and neurons. Complications of ZIKV infection arise both early and late in pregnancy. Consequently, it is likely that ZIKV infection of both neuroprogenitor cells and neurons negatively impact the developing fetus. Little is known about how ZIKV spreads in the brain, to the retina and other neural tissues. Like other neurotropic viruses, ZIKV probably spreads into and from neuronal axons. This mode of virus spread allows for very fast spread between neurons and between neurons and other cells. We show preliminary data that: 1) ZIKV productively infected neuronal cell bodies, 2) ZIKV particles were observed within neuronal axons and, 3) infectious ZIKV was released from axon tips. These preliminary data support our hypothesis that ZIKV employs axonal transport machinery in neurons to spread through the developing fetal brain and, perhaps, to the eye. The proposal includes two specific aims. Aim 1 will characterize anterograde and retrograde transport of ZIKV particles in neuronal axons and investigate whether specific cellular cargo molecules colocalize with ZIKV virions in axons. Cellular cargo molecules represent an important tool by which axonal transport can be characterized. By knowing which cargos colocalize with ZIKV we can make predictions about which kinesin motors transport the virus. We know that ZIKV can be transported in the anterograde direction (into axons from the neuron cytoplasm) and we will extend these studies to determine whether ZIKV can move in the retrograde direction (from axons toward neuron cell bodies or soma). Aim 2 will seek to determine which kinesin motors transport ZIKV in the anterograde direction. This aim will characterize which kinesin motors are found in association with membrane vesicles containing ZIKV enveloped particles. The functional consequences of specific kinesins that colocalize with ZIKV will be tested by silencing these kinesins and using dominant negative kinesins. Together, these studies will provide a better picture of how ZIKV is transported in neuronal axons and help improve our understanding of how ZIKV spreads in vivo.