Immunoliposomes bearing lymphocyte activation gene 3 fusion protein and P5 peptide: A novel vaccine for breast cancer.

LAG3-Ig as an immune adjuvant has elicited potent anti-tumor immune responses in several preclinical and clinical studies, but the full potential immunostimulatory of LAG3-Ig has yet to be achieved. We hypothesized that by anchoring LAG3-Ig to the surface of liposomes, the adjuvant activity of LAG3-Ig could be improved. We also investigated the immunotherapy by co-delivery of liposome-coupled LAG3-Ig and P5 tumor antigen in mice model of TUBO breast cancer. We prepared and characterized novel PEGylated liposomes bearing surface conjugated LAG3-Ig and P5. Consistent with our hypothesis, liposomes-conjugated LAG3-Ig via multivalent binding to MHC class II molecules exerted immunostimulatory of LAG3-Ig and markedly induced maturation of dendritic cells more efficiently than free LAG3-Ig. LAG3-Ig-P5-immunoliposomes effectively elicited protective anti-tumor responses more than locally injected soluble LAG3-Ig + P5. The higher percentage of CD4+ and CD8+ T cells in the spleen and more rapid and pronounced infiltration of these effector cells into the site of the tumor were seen following immunoliposome therapy. Finally, anti-tumor immunity induced by LAG3-Ig-P5-immunoliposomes translated into the more tumor regression and prolonged survival of treated mice, compared to soluble immunotherapy. Taken together, our findings suggest that LAG3-Ig-P5-immunoliposomes can be considered as a valuable candidate for developing a liposome-based therapeutic cancer vaccine in treating HER2/ neu+ breast cancer patients.