ISG15 and infection: At 24 hpi, when only RSAD2 was found to be differentially expressed by G18 infection by analysis of the RNA-Seq data (Data Set S1), four genes, OAS1Y, CXCL10, ISG15, and RSAD2, were upregulated in response to AF2122 and G18 (Table 2, asterisks), and there was no strain-specific difference in expression in any of the six investigated genes.