Restricted Infection and Cytokine Expression in Primary Murine Astrocytes Induced by the H5N1 Influenza Virus

Abstract

Central nervous system (CNS) dysfunction caused by infection with neurovirulent viruses is of interest, and may play an important role in many neurodegenerative diseases. Since neuronal functions are believed to be partly regulated by cytokines produced by astrocytes, neuroinflammation and neurodegeneration caused by H5N1 influenza virus infection could be due to abnormal cytokine production of those infected astrocytes. In the present study, cytokine responses of murine astrocytes following H5N1 virus infection were investigated. Primary astrocytes from neonatal outbred ICR mice were isolated and used to investigate cytopathology upon infection with the H5N1 virus (A/Chicken/Thailand/CUK2/04). Thereafter, cell lysates at 6, 24, 48, and 72 hours-post infection (hpi) were collected and subjected to quantification of cytokine gene expression, including TNF-α, IL-1β, IL-2, IL-6 and IL-12β, by quantitative RT-PCR. The results revealed that infection with the H5N1 virus in primary murine astrocytes was restricted, and resulted in abortive virus infection. However, this abortive infection in the astrocytes was found to result in significant upregulation of IL-1β mRNA expression at 72 hpi compared with the mock-infected group, while the mRNA expression of IL-2 and IL-12β was observed to have undergone significant down-regulation at 6-72 hpi and 24-48 hpi, respectively. The results of the present study could support the role of astrocytes in neuroinflammation and neurodegeneration.