STAT2 and hydrops fetalis: When HF cells were infected with wild-type, IE1(Δ290–320), or IE1(Δ421–475) viruses for 12 h and co-IP assays were performed, both wild-type IE1 and IE1(Δ290–320) were coprecipitated with comparable amounts of STAT2; however, IE1(Δ421–475) did not interact with STAT2 (Fig. 6B), thus demonstrating that IE1(Δ290–320) interacts with STAT2 as efficiently as wild-type IE1.