R E S E A R C H Open Access
Differential neurovirulence of Usutu virus lineages in mice and neuronal cells
Marion Clé 1 † , Orianne Constant 1 † , Jonathan Barthelemy 1 , Caroline Desmetz 2 , Marie France Martin 3 , Lina Lapeyre 3 , Daniel Cadar 4 , Giovanni Savini 5 , Liana Teodori 5 , Federica Monaco 5 , Jonas Schmidt-Chanasit 4,6 , Juan-Carlos Saiz 7 , Gaëlle Gonzales 8 , Sylvie Lecollinet 8 , Cécile Beck 8 , Fabien Gosselet 9 , Philippe Van de Perre 1,10 ,
Vincent Foulongne 1,10 , Sara Salinas 1 and Yannick Simonin 1*
Abstract
Background: Usutu virus (USUV) is an emerging neurotropic arthropod-borne virus recently involved in massive die offs of wild birds predominantly reported in Europe. Although primarily asymptomatic or presenting mild clinical signs, humans infected by USUV can develop neuroinvasive pathologies (including encephalitis and
meningoencephalitis). Similar to other flaviviruses, such as West Nile virus, USUV is capable of reaching the central nervous system. However, the neuropathogenesis of USUV is still poorly understood, and the virulence of the specific USUV lineages is currently unknown. One of the major complexities of the study of USUV pathogenesis is the presence of a great diversity of lineages circulating at the same time and in the same location.
Methods: The aim of this work was to determine the neurovirulence of isolates from the six main lineages circulating in Europe using mouse model and several neuronal cell lines (neurons, microglia, pericytes, brain endothelial cells, astrocytes, and in vitro Blood-Brain Barrier model).
Results: Our results indicate that all strains are neurotropic but have different virulence profiles. The Europe 2 strain, previously described as being involved in several clinical cases, induced the shortest survival time and highest mortality in vivo and appeared to be more virulent and persistent in microglial, astrocytes, and brain endothelial cells, while also inducing an atypical cytopathic effect. Moreover, an amino acid substitution (D3425E) was specifically identified in the RNA-dependent RNA polymerase domain of the NS5 protein of this lineage.
Conclusions: Altogether, these data show a broad neurotropism for USUV in the central nervous system with lineage-dependent virulence. Our results will help to better understand the biological and epidemiological diversity of USUV infection.
Keywords: Usutu virus, Arbovirus, Flavivirus, Neurotropism, Central nervous system
Background
Usutu virus (USUV) is an arbovirus of the genus Flavivi- rus from the Flaviviridae family. It belongs to the Japa- nese encephalitis virus (JEV) antigenic complex isolated
for the first time in 1959 from Culex neavei (trapped in Swaziland) after intracerebral inoculation of newborn mice in Southern Africa [1 – 4]. Over recent years, this emerging virus has dispersed out of Africa mainly into Europe [5]. It was presumably carried by migratory birds and their associated mosquitoes, such as Culex pipiens [6 – 9]. Similar to other flaviviruses, USUV is an icosahedral-enveloped virus with a single-stranded posi- tive sense RNA of 11 kb, with a 5 ′ cap structure and one
© The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
* Correspondence: yannick.simonin@umontpellier.fr
†
Marion Clé and Orianne Constant contributed equally to this work.
1