Meta-analysis workflow. Briefly the compendium was assembled from multiple microarray data sets and either separated into intensity-level measurements or converted to log-ratios of measurements in infected samples to their respective mock infections. Different meta-analysis methods were applied and resulted in two classes of signatures. Various criteria were used to evaluate signatures. "INF" refers to infected samples, "CTR" to matching mock-infected control samples, "PCA" to principal components analysis, and "PCCS" to Pearson correlation coefficient scatter plot.