Host Gene Expression Signatures Discriminate between Ferrets Infected with Genetically Similar H1N1 Strains.

Different respiratory viruses induce virus-specific gene expression in the host. Recent evidence, including those presented here, suggests that genetically related isolates of influenza virus induce strain specific host gene regulation in several animal models. Here, we identified systemic strain-specific gene expression signatures in ferrets infected with pandemic influenza A/California/07/2009, A/Mexico/4482/2009 or seasonal influenza A/Brisbane/59/2007. Using uncorrelated shrunken centroid classification, we were able to accurately identify the infecting influenza strain with a combined gene expression profile of 10 selected genes, independent of the severity of disease. Another gene signature, consisting of 7 genes, could classify samples based on lung pathology. Furthermore, we identified a gene expression profile consisting of 31 probes that could classify samples based on both strain and severity of disease. Thus, we show that expression-based analysis of non-infected tissue enables distinction between genetically related influenza viruses as well as lung pathology. These results open for development of alternative tools for influenza diagnostics. Blood derived total RNA from 63 ferrets. 30 ferrets were infected with A/California/07/2009 (15 with 10E6 TCID50/ml and 15 with 10E4 TCID50/ml, 15 with A/Mexico/4482/2009 and 12 with A/BN/2007. 6 animals were mock infected with PBS and used as controls. Three animals per group were euthanized at days 1, 2, 3, 5 and 7.