Efficacy and limitations of combined A2.CAR Treg and anti-CD154 therapy in a mouse model of haplo-mismatched heart transplantation

Durgam, S. S.; Rosado sanchez, I.; Yin, D.; Speck, M.; Mojibian, M.; Sayin, I.; Hynes, G.; Alegre, M.-L.; Levings, M. K.; Chong, A. S.

doi:10.1101/2024.09.20.614149

bioRxiv · 10.1101/2024.09.20.614149

Efficacy and limitations of combined A2.CAR Treg and anti-CD154 therapy in a mouse model of haplo-mismatched heart transplantation

Durgam, S. S.·Rosado sanchez, I.·Yin, D.·Speck, M.·Mojibian, M.·Sayin, I.·Hynes, G.·Alegre, M.-L.·Levings, M. K.·Chong, A. S.

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Abstract

Successful allograft specific tolerance induction would eliminate the need for daily immunosuppression and improve post-transplant quality of life. Adoptive cell therapy with regulatory T cells expressing donor-specific Chimeric Antigen Receptors (CAR-Tregs) is a promising strategy, but as monotherapy, cannot prolong the survival with allografts with multiple MHC mismatches. Using an HLA-A2-transgenic haplo-mismatched heart transplantation model in immunocompetent C57Bl/6 recipients, we show that HLA-A2-specific (A2) CAR Tregs was able to synergize with low dose of anti-CD154 to enhance graft survival. Using haplo-mismatched grafts expressing the 2W-OVA transgene and tetramer-based tracking of 2W- and OVA-specific T cells, we showed that in mice with accepted grafts, A2.CAR Tregs inhibited endogenous non-A2 donor- specific T cell, B cell and antibody responses, and promoted a significant increase in endogenous FoxP3+Tregs with indirect donor-specificity. By contrast, in mice where A2.CAR Tregs failed to prolong graft survival, FoxP3neg A2.CAR T cells preferentially accumulated in rejecting allografts and endogenous donor-specific responses were not controlled. This study therefore provides the first evidence for synergy between A2.CAR Tregs and CD154 blockade to promote infectious tolerance in immunocompetent recipients of haplo-mismatched heart grafts and defines features of A2.CAR Tregs when they fail to reshape host immunity towards allograft tolerance.

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Durgam, S. S., Rosado sanchez, I., Yin, D., Speck, M., Mojibian, M., Sayin, I., Hynes, G., Alegre, M.-L., Levings, M. K., Chong, A. S.. 2024-09-24. Efficacy and limitations of combined A2.CAR Treg and anti-CD154 therapy in a mouse model of haplo-mismatched heart transplantation. https://doi.org/10.1101/2024.09.20.614149

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