RAF1 and infection: To examine the effects of COPI-WT or COPI-SNP overexpression on NS1 secretion, independent of viral RNA replication and/or spread of infection, we employed the T7 RNA polymerase-driven pIRO-D expression system in which heterologously expressed T7 RNA polymerase drives the expression of the DENV2 NS1-NS5 polyprotein, and induces the formation of replication organelles that are morphologically indistinguishable from those of wild-type DENV infection (42).