USP13 and infection: Performing ProcartaPlex ELISA assays, we assessed whether the soluble TNF factors of these pathways (TNF-alpha, TNFSF9 and TNFRSF9) were secreted following infection and observed significantly increased secretion of TNF-alpha (Fig. 4C) and TNFRSF9 (Fig. 4D) from both USP7 and USP13 cells at 48 hpi.