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Published in: European Journal of Nuclear Medicine and Molecular Imaging 3/2023

Open Access 09-11-2022 | Zika Virus | Original Article

TSPO expression in a Zika virus murine infection model as an imaging target for acute infection-induced neuroinflammation

Authors: Carla Bianca Luena Victorio, Rasha Msallam, Wisna Novera, Joanne Ong, Tham Jing Yang, Arun Ganasarajah, Jenny Low, Satoru Watanabe, Ann-Marie Chacko

Published in: European Journal of Nuclear Medicine and Molecular Imaging | Issue 3/2023

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Abstract

Introduction

Zika virus (ZIKV) is a neurotropic human pathogen that causes neuroinflammation, whose hallmark is elevated translocator protein (TSPO) expression in the brain. This study investigates ZIKV-associated changes in adult brain TSPO expression, evaluates the effectiveness of TSPO radioligands in detecting TSPO expression, and identifies cells that drive brain TSPO expression in a mouse infection model.

Methods

The interferon-deficient AG129 mouse infected with ZIKV was used as neuroinflammation model. TSPO expression was evaluated by tissue immunostaining. TSPO radioligands, [3H]PK11195 and [18F]FEPPA, were used for in vitro and ex vivo detection of TSPO in infected brains. [18F]FEPPA-PET was used for in vivo detection of TSPO expression. Cell subsets that contribute to TSPO expression were identified by flow cytometry.

Results

Brain TSPO expression increased with ZIKV disease severity. This increase was contributed by TSPO-positive microglia and infiltrating monocytes; and by influx of TSPO-expressing immune cells into the brain. [3H]PK11195 and [18F]FEPPA distinguish ZIKV-infected brains from normal controls in vitro and ex vivo. [18F]FEPPA brain uptake by PET imaging correlated with disease severity and neuroinflammation. However, TSPO expression by immune cells contributed to significant blood pool [18F]FEPPA activity which could confound [18F]FEPPA-PET imaging results.

Conclusions

TSPO is a biologically relevant imaging target for ZIKV neuroinflammation. Brain [18F]FEPPA uptake can be a surrogate marker for ZIKV disease and may be a potential PET imaging marker for ZIKV-induced neuroinflammation. Future TSPO-PET/SPECT studies on viral neuroinflammation and related encephalitis should assess the contribution of immune cells on TSPO expression and employ appropriate image correction methods to subtract blood pool activity.
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Metadata
Title
TSPO expression in a Zika virus murine infection model as an imaging target for acute infection-induced neuroinflammation
Authors
Carla Bianca Luena Victorio
Rasha Msallam
Wisna Novera
Joanne Ong
Tham Jing Yang
Arun Ganasarajah
Jenny Low
Satoru Watanabe
Ann-Marie Chacko
Publication date
09-11-2022
Publisher
Springer Berlin Heidelberg
Published in
European Journal of Nuclear Medicine and Molecular Imaging / Issue 3/2023
Print ISSN: 1619-7070
Electronic ISSN: 1619-7089
DOI
https://doi.org/10.1007/s00259-022-06019-w

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