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J Vet Sci 2018; 19(6): 750-758  https://doi.org/10.4142/jvs.2018.19.6.750
Neonatal influenza virus infection affects myelination in influenza-recovered mouse brain
Jin Hee Kim, Ji Eun Yu, Byung-Joon Chang, Sang-Soep Nahm*
Department of Veterinary Medicine, College of Veterinary Medicine, Konkuk University, Seoul 05029, Korea
Correspondence to: Tel: +82-2-450-3705; Fax: +82-2-450-3037; E-mail: ssnahm@konkuk.ac.kr
Received: April 24, 2018; Revised: July 24, 2018; Accepted: August 6, 2018; Published online: November 30, 2018.
Abstract
Influenza virus infection is a zoonosis that has great socioeconomic effects worldwide. Influenza infection induces respiratory symptoms, while the influenza virus can infect brain and leave central nervous system sequelae. As children are more vulnerable to infection, they are at risk of long-term neurological effects once their brains are infected. We previously demonstrated that functional changes in hippocampal neurons were observed in mice recovered from neonatal influenza infection. In this study, we investigated changes in myelination properties that could affect neural dysfunction. Mice were infected with the influenza virus on postnatal day 5. Tissues were harvested from recovered mice 21-days post-infection. The expression levels for myelin basic protein (MBP) were determined, and immunohistochemical staining and transmission electron microscopy were performed. Real-time polymerase chain reaction and Western blot analyses showed that mRNA and protein expressions increased in the hippocampus and cerebellum of recovered mice. Increased MBP-staining signal was observed in the recovered mouse brain. By calculating the relative thickness of myelin sheath in relation to nerve fiber diameter (G-ratio) from electron photomicrographs, an increased G-ratio was observed in both the hippocampus and cerebellum of recovered mice. Influenza infection in oligodendrocyte-enriched primary brain cell cultures showed that proinflammatory cytokines may induce MBP upregulation. These results suggested that increased MBP expression could be a compensatory change related to hypomyelination, which may underlie neural dysfunction in recovered mice. In summary, the present results demonstrate that influenza infection during the neonatal period affects myelination and further induces functional changes in influenza-recovered mouse brain.
Keywords: cerebellum, hippocampus, influenza, myelin, oligodendrocyte


© 2018 The Korean Society of Veterinary Science.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.