OX40L-expressing recombinant modified vaccinia virus Ankara induces potent antitumor immunity via reprogramming Tregs.

Effective depletion of immune suppressive regulatory T cells (Tregs) in the tumor microenvironment without triggering systemic autoimmunity is an important strategy for cancer immunotherapy. Modified vaccinia virus Ankara (MVA) is a highly attenuated, non-replicative vaccinia virus with a long history of human use. Here, we report rational engineering of an immune-activating recombinant MVA (rMVA, MVA∆E5R-Flt3L-OX40L) with deletion of the vaccinia E5R gene (encoding an inhibitor of the DNA sensor cyclic GMP-AMP synthase, cGAS) and expression of two membrane-anchored transgenes, Flt3L and OX40L. Intratumoral (IT) delivery of rMVA (MVA∆E5R-Flt3L-OX40L) generates potent antitumor immunity, dependent on CD8+ T cells, the cGAS/STING-mediated cytosolic DNA-sensing pathway, and type I IFN signaling. Remarkably, IT rMVA (MVA∆E5R-Flt3L-OX40L) depletes OX40hi regulatory T cells via OX40L/OX40 interaction and IFNAR signaling. Single-cell RNA-seq analyses of tumors treated with rMVA showed the depletion of OX40hiCCR8hi Tregs and expansion of IFN-responsive Tregs. Taken together, our study provides a proof-of-concept for depleting and reprogramming intratumoral Tregs via an immune-activating rMVA.

Sumoylation and its regulation in testicular Sertoli cells.

The molecular regulation of Sertoli cells and their crosstalk with germ cells has not been fully characterized. SUMO proteins are essential for normal development and are expressed in mouse and human Sertoli cells; However, the cell-specific role of sumoylation in those cells has only started to be elucidated. In other cell types, including granulosa cells, sumoylation is regulated by a SUMO ligase KAP1/Trim28. Deletion of KAP1 in Sertoli cells causes testicular degeneration; However, the role of KAP1 in those cells has not been identified. Here we show that both mouse and human Sertoli undergo apoptosis upon inhibition of sumoylation with a chemical inhibitor or via a siRNA technology. We have additionally detected changes in the Sertoli cell proteome upon the inhibition of sumoylation, and our data suggest that among others, the expression of ER/stress-related proteins is highly affected by this inhibition. Sumoylation may also regulate the NOTCH signaling which is important for the maintenance of the developing germ cells. Furthermore, we show that a siRNA-down-regulation of KAP1 in a Sertoli-derived cell line causes an almost complete inactivation of sumoylation. In conclusion, sumoylation regulates important survival and signaling pathways in Sertoli cells, and KAP1 can be a major regulator of sumoylation in these cells.