Adeno-associated viral vectors encoding anti-P2X7 nanobodies reduce graft-versus-host disease in a humanised mouse...

Graft-versus-host disease (GVHD) is an inflammatory disorder that arises following allogeneic haematopoietic stem cell transplantation. P2X7 is an extracellular ATP-gated cation channel present on immune cells. P2X7 blockade with small molecule inhibitors impairs GVHD development in a humanised mouse model. This study investigated whether adeno-associated viral (AAV) vectors encoding nanobodies (Nbs) that block mouse P2X7 (mP2X7) or both mP2X7 and human P2X7 (m/hP2X7) impair GVHD development in this model.

On Day -21, NOD.Cg-Prkdc ^scid Il2rg ^tm1Wjl /SzJ (NSG) mice were injected intramuscularly with 10 × 10¹⁰ viral genomes encoding either green fluorescent protein (GFP), an anti-mP2X7 Nb or an anti-m/hP2X7 Nb, or with saline. On Day 0, mice were euthanised or injected intraperitoneally with 10 × 10⁶ human peripheral blood mononuclear cells and monitored thrice weekly for signs of GVHD until the experiment or disease endpoint.

The anti-m/hP2X7 and anti-mP2X7 Nbs reduced clinical GVHD and time to disease onset, as well as liver and lung GVHD. Both Nbs reduced liver human T helper (Th)17 cells. Sera collected at Day 0 and disease endpoint from treated mice, but not from control mice, completely blocked P2X7 activity in human RPMI 8226 and/or murine J774 cells, confirming circulating anti-P2X7 Nbs in mice from Day 0 to disease endpoint.

This study indicates that P2X7 blockade with an anti-m/hP2X7 and to a lesser extent an anti-mP2X7 Nb reduces GVHD progression in humanised mice. This supports the future testing of these P2X7 biologics as a prophylactic therapy for GVHD.