Abstract
Purpose :
CD4+FoxP3+CD25+ regulatory cells (Tregs) are essential for maintaining self-tolerance and their manipulation is of considerable interest as a strategy to prevent allograft rejection. mPTX-35 is an affinity matured mouse IgG1 anti-Human TNFRSF25 antibody, which can expand Tregs by stimulating the TNFRSF25 receptor. This work tested whether mPTX-35 treatment could prolong allogeneic corneal transplants (CT) in mice accompanied by Tregs expansion.
Methods :
Balb/c mice were administered different doses (0.5 ug, 5 ug, 50 ug) of mPTX-35 via subconjunctival (SC) injection and compared to an IgG1 (50ug) control. CD4+FoxP3+CD25+ Tregs in conjunctiva and draining LN were analyzed by flow cytometry 6 and 14 days post-treatment. MHC-mismatched CTs were performed from B6 to Balb/c mice, with the following treatment groups: (1) 1-dose-mPTX-35 (single dose, SC, 5ug, day-3), (2) 2-dose-mPTX-35 (2 doses, SC, 5 ug, day 0 & 7). Data is presented using median survival day post-transplant (MST) comparing mPTX-35 treated to IgG1 controls. Corneal opacity of the graft was scored twice per week using a pre-established scale ranging from 0-4; rejection was defined as a recorded score of ≥3 for two consecutive readings.
Results :
In the conjunctiva, Tregs/CD4+ frequency was significantly increased in the mPTX-35 treated mice on day 6 post-treatment at doses of 5 ug mPTX-35 (51.4±3.1%, p<0.0001) and 50 ug (48.6±2.5%, p<0.0001) vs IgG1 control (16.3±1%). Significant increases were also detected on day 14 in all 3 dose groups. Tregs/CD4+ frequency in the draining LN on day 6 was significantly elevated in the 5 ug mPTX-35 (22.7±2.5%, p=0.0037) and 50 ug mPTX-35 (19.8±1.6%, p=0.0048), but not in the 0.5 ug mPTX-35 (10.6±1.5%, ns) compared to the control (11.3±2.1%). In contrast to the subconjunctiva, no differences were detected on day 14 in the draining LN. Compared to their IgG1 controls, MST was not prolonged in the 1-dose-mPTX-35 group (27.5 d vs 33d, n=6/group), but significantly prolonged in the 2-dose-mPTX-35 group (39 d vs 21 d, p=0.0224, n=6/group).
Conclusions :
Local ocular delivery of TNFRSF25 specific mPTX-35 prolongs graft survival day in the allogeneic CT setting in mice. We posit recruiting Treg cells to the local conjunctiva and draining LN inhibits rejection responses. mPTX-35 would be a potential candidate to treat CT rejection in clinic.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.