Shiho Torii, will present her research, “From mosquitoes to mice: Viral genetic factors determining Zika virus lineage differences"

Tuesday, the 21st of April 2026, at 11.30 am, in Amphitheatre G1 – UCBL Gerland– 50 avenue Tony Garnier – 69007

Abstract

Zika virus (ZIKV) is an orthoflavivirus primarily transmitted by Aedes aegypti. Over the past two decades, it has caused significant outbreaks associated with birth defects and neurological disorders. ZIKV falls into two main phylogenetic groups: African and Asian lineages, each with unique biological traits. African lineage Zika virus strains are more transmissible by Aedes aegypti and more pathogenic to mice than their Asian counterparts, however the genetic determinants underlying these differences are unknown. Here, we address this question by comparing recent African and Asian strains using a panel of chimeric viruses, with swapped genome segments.

Our mosquito infection experiments revealed that structural genes primarily influenced in vivo mosquito transmission, regardless of the mosquito genetic background. A stochastic model of in vivo viral dynamics that mirrors the observed patterns, suggested that the primary difference in transmission efficiency between the African and Asian strains lied in their ability to traverse mosquito salivary glands. In Ifnar1 knockout mice infected with these chimeric viruses, non-structural genes of African strains correlated with higher clinical scores, while structural genes caused severe viremia. These findings suggest that the differences in biological properties between lineages are polygenic in nature. We futhermore examined transmission potential of the African and Asian strains from mouse to mosquitoes. Interestingly, there was no observed difference between the African and Asian strains in the prevalence of mosquitoes with infectious saliva, while African strain-infected mice demonstrated higher viremia than Asian counterpart. This indicates that factors in the blood of infected hosts might influence virus infection in mosquitoes. Ongoing research aims to uncover the underlying molecular mechanisms and the factors that have led to outbreaks by Asian lineages.

Dr Shiho Torii obtained her PhD in Veterinary medicine from Hokkaido University in 2020 and has been working at the Institut Pasteur since June 2021. She will launch her own laboratory at Osaka University from July 2026. Her research interest is arthropod-borne viruses, particularly those transmitted by mosquitoes. Through the virus reverse genetics and in vivo mosquito infection experiments,  she would like to comprehend how arthropod-borne viruses emerge and cause epidemics within the complex interactions between animal hosts, arthropod vectors and environment.

Hosts : V. Raquin (IVPC - ATP team)