Zika virus infection of mature neurons from immunocompetent mice generates a disease-associated microglia and a tauopathy-like phenotype in link with a delayed interferon beta response

Abstract

Background Zika virus (ZIKV) infection at postnatal or adult age can lead to neurological disorders associated with cognitive defects. Yet, how mature neurons respond to ZIKV remains substantially unexplored. Methods The impact of ZIKV infection on mature neurons and microglia was analyzed at the molecular and cellular levels, in vitro using immunocompetent primary cultured neurons and microglia, and in vivo in the brain of adult immunocompetent mice following intracranial ZIKV inoculation. We have used C57BL/6 and the genetically diverse Collaborative Cross mouse strains, displaying a broad range of susceptibility to ZIKV infection, to question the correlation between the effects induced by ZIKV infection on neurons and microglia and the in vivo susceptibility to ZIKV. Results As a result of a delayed induction of interferon beta (IFNB) expression and response, infected neurons displayed an inability to stop ZIKV replication, a trait that was further increased in neurons from susceptible mice. Alongside with an enhanced expression of ZIKV RNA, we observed in vivo, in the brain of susceptible mice, an increased level of active Iba1-expressing microglial cells occasionally engulfing neurons and displaying a gene expression profile close to the molecular signature of disease-associated microglia (DAM). In vivo as well as in vitro, only neurons and not microglial cells were identified as infected, raising the question of the mechanisms underlying microglia activation following brain ZIKV infection. Treatment of primary cultured microglia with conditioned media from ZIKV-infected neurons demonstrated that type-I interferons (IFNs-I) secreted by neurons late after infection activate non-infected microglial cells. In addition, ZIKV infection induced pathological phosphorylation of Tau (pTau) protein, a hallmark of neurodegenerative tauopathies, in vitro and in vivo with clusters of neurons displaying pTau surrounded by active microglial cells. Conclusions We show that ZIKV-infected mature neurons display an inability to stop viral replication in link with a delayed IFNB expression and response, while signaling microglia for activation through IFNs-I secreted at late times post-infection. In the brain of ZIKV-infected susceptible mice, uninfected microglial cells adopt an active morphology and a DAM expression profile, surrounding and sometimes engulfing neurons while ZIKV-infected neurons accumulate pTau, overall reflecting a tauopathy-like phenotype.

Susceptibility to Zika virus in a Collaborative Cross mouse strain is induced by Irf3 deficiency in vitro but requires other variants in vivo

“…In line with these findings, our study provides, to our knowledge, the first evidence for a role of Irf3 in the infection of murine cells by ZIKV. Moreover, we recently reported that primary cultured neurons (PCNs) show a delayed activation of the Ifnb1 expression upon ZIKV exposure compared with MEFs, and that this delay is even longer in PCNs derived from CC071 compared with CC001 [ 34 ]. The identification of the Irf3 mutation in CC071 provides an explanation for this observation, although it would require confirmation in B6- Irf3 KO PCNs.…”

“…Discrepancies between the consequences of Irf3 deficiency in in vitro and in vivo experiments likely reflect differences between a single cell type model with an intrinsic capacity to mount a more or less IRF3-dependent IFN-I response, and a multicellular organism in which the paracrine effect of IFN-I produced by the most reactive cells induces protection of other, less reactive, cell types. In fact, we have recently reported such cooperation between neurons and microglia cells [ 34 ].…”

ZIKV infection differentially affects the transcriptional profiles in HTR8 and U251 cells

“…These studies have consistently demonstrated that ZIKV can infect the neurons, resulting in cell death and impaired neurodevelopment, ultimately leading to the development of microcephaly ( Alpuche-Lazcano et al., 2021 ; Hughes et al., 2016 ; Lin et al., 2017 ; Oh et al., 2017 ). In addition to neural cells, studies have shown that glial cells, including microglia and astrocytes, are also significant targets of ZIKV infection in the brain ( Jorgačevski et al., 2019 ; Manet et al., 2022 ; van den Pol et al., 2017 ). Astrocytes are the most abundant glial cells in the central nervous system and play crucial roles in the immune response, synaptic guidance, and maintenance of the integrity of the blood-brain barrier (BBB) ( Ransom and Ransom, 2012 ).…”