We began this study by comparing the activity of Pla and Epo in Pla-mediated functions that i) have been documented to be important in plague pathogenesis in vivo, such as plasminogen activation by cleavage, or ii) directly or indirectly enhance the virulence potential in vitro, such as degradation of α2AP and PAI-1 and invasion to the human endothelial-like cell line. The gene discussed is SERPINE1; the disease is plague.