TOP1 and viral infectious disease: These results indicate that inhibition of Top1 expression by CPT treatment in healthy CD4 T cells can recapitulate the mtDNA damage found in CD4 T cells from HCV- and HIV-infected patients (Figure 1), and thus CPT represents a reliable model to study the mechanism of Top1-mediated mtDNA topological aberrancies and their role in T cell dysregulation during viral infection.