Background: Minor histocompatibility antigen (miHA) vaccines have the potential to augment graft-versus-tumor effects without graft-versus-host disease (GVHD). We used mixed hematopoietic chimerism in the canine model of major histocompatibility complex-matched allogeneic hematopoietic cell transplantation as a platform to develop a miHA vaccination regimen.
Methods: We engineered DNA plasmids and replication-deficient human adenovirus type 5 constructs encoding large sections of canine SMCY and the entire canine SRY gene.
Results: Priming with replication-deficient human adenovirus type 5 constructs and boosting with ex vivo plasmid-transfected dendritic cells and cutaneous delivery of plasmids with a particle-mediated epidermal delivery device (PMED) in 2 female dogs induced antigen-specific T-cell responses. Similar responses were observed after a prime-boost vaccine regimen in three female hematopoietic cell transplantation donors. Subsequent donor lymphocyte infusion resulted in a significant change of chimerism in 1 of 3 male recipients without any signs of graft-versus-host disease. The change in chimerism in the recipient occurred in association with the development of CD4+ and CD8+ T-cell responses to the same peptide pools detected in the donor.
Conclusions: These studies describe the first in vivo response to miHA vaccination in a large, outbred animal model without using recipient cells to sensitize the donor. This model provides a platform for ongoing experiments designed to define optimal miHA targets and develop protocols to directly vaccinate the recipient.