Imaging of viral neuroinvasion in the zebrafish reveals that Sindbis and chikungunya viruses favour different entry routes.

Gabriella Passoni,Pierre Boudinot,Christelle Langevin,Bryan C Mounce,Valérie Briolat,Marco Vignuzzi,Elodie De Job,Nuno Palha,Pierre Affaticati,Jean-Pierre Levraud,Philippe Herbomel,Maria-Carla Saleh,Jean-Stéphane Joly

doi:10.1242/dmm.029231

Abstract

ABSTRACTAlphaviruses, such as chikungunya virus (CHIKV) and Sindbis virus (SINV), are vector-borne pathogens that cause acute illnesses in humans and are sometimes associated with neuropathies, especially in infants and elderly patients. Little is known about their mechanism of entry into the central nervous system (CNS), even for SINV, which has been used extensively as a model for viral encephalopathies. We previously established a CHIKV infection model in the optically transparent zebrafish larva; here we describe a new SINV infection model in this host. We imaged in vivo the onset and progression of the infection caused by intravenous SINV inoculation. Similar to that described for CHIKV, infection in the periphery was detected early and was transient, whereas CNS infection started at later time points and was persistent or progressive. We then tested the possible mechanisms of neuroinvasion by CHIKV and SINV. Neither virus relied on macrophage-mediated transport to access the CNS. CHIKV, but not SINV, always infects endothelial cells of the brain vasculature. By contrast, axonal transport was much more efficient with SINV than CHIKV, both from the periphery to the CNS and between neural tissues. Thus, the preferred mechanisms of neuroinvasion by these two related viruses are distinct, providing a powerful imaging-friendly system to compare mechanisms and prevention methods of encephalopathies.

Highlights

Our study reveals the conservation of neurotropism of Alphaviruses from mammals to fish based on distinct entry routes in the central nervous system (CNS), namely infection of endothelial cells of the blood–brain barrier (BBB) for chikungunya virus (CHIKV) in contrast to axonal transport from peripheral nerves for Sindbis virus (SINV)
Course of SINV infection after peripheral inoculation Wild-type (WT) zebrafish larvae were inoculated IV at 3 days postfertilization (Fig. 1A) with ∼102 plaque forming units (PFU) of SINV-green fluorescent protein (GFP), similar to the protocol used for CHIKV-GFP (Palha et al, 2013)
We focused on its neuroinvasion and compared it with that of CHIKV

Summary

Introduction

Some viruses are able to infect cells of the BBB (i.e. endothelial cells that form brain microvessels) or other components of the brain–periphery interface, such as epithelial cells of choroid plexuses. This allows their release in the brain parenchyma by the infected cells and/or disruption of the barrier causing leakage of blood-borne virions. Another strategy is known as the ‘Trojan horse’ entry, whereby viruses hide in monocytes or macrophages, and exploit the ability of these cells to cross the barrier to enter the brain. Various viruses travel within the numerous axons of motor or sensory neurons that connect the CNS to the periphery, using either anterograde or retrograde transport

Methods

Results

Conclusion