Tregitopes derived from canine proteins can enhance T regulatory lymphocytes frequency in dog PBMC culture in vitro

Adoptive cell therapy using ex vivo expanded autologous Tregs could be a novel therapeutic approach for cell-based immunotherapy in dogs. This study aimed to expand dog Treg lymphocytes via the use of tregitopes. PBMCs were isolated from healthy beagle dogs and stimulated with peptides: human tregitope EEQ, two potential canine tregitopes- EQF and PSV and whole canine IgG in primary cultures. In addition, lymphocytes were simultaneously stimulated with peptides and canine vaccine antigens. The frequencies of Treg lymphocytes (CD4+CD25+Foxp3+, CD4+Foxp3+) and activated lymphocytes (CD4+CD25+) were determined by flow cytometry. A statistically significant increase in the frequency of CD4+Foxp3+ and CD4+CD25+Foxp3+ lymphocytes stimulated with PSV and EQF peptides and canine IgG was observed. No increase in the Treg lymphocyte frequency occurred after EEQ Tregitope stimulation or vaccine antigen costimulation. Canine Treg lymphocytes isolated from peripheral blood are sensitive to stimulation with peptides with potential tregitope properties derived from canine proteins.