[Expression of host genes in influenza virus infected cells]

The NS1 protein of influenza virus shuts off host gene expression by inhibiting the polyadenylation-site cleavage of host pre-mRNAs, resulting in a general decline in cellular protein synthesis. On the other hand, an activation of several host genes related to host antiviral defense such as interferon- alpha/beta, MxA, 2',5'-oligoadenylate synthetase, and Fas occures upon infection. Therefore, balance of the shut-off and the activation of cellular genes during virus growth may be crucial in determining the outcome of infection. To obtain a comprehensive view of the global effects of influenza virus infection on human respiratory epithelial cells at the cytoplasmic mRNA level, we performed oligo DNA microarray analysis using GeneChip arrays (Affymetrix). In NCl-H292 cells infected with A/Udorn/72 virus, more than 4-fold increase of expression level was observed for 164 genes at 12 h pi. Approximately 60% of the virus-stimulated genes (VSGs) were also stimulated with interferon-beta treatment and contained the genes known to possess antiviral activity. Interestingly, majority of the VSGs were stimulated before induction of interferons, suggesting that the stimulation of the VSGs during early phase of infection is not mediated by interferons, but it is triggered from within by the virus infection.