Xenogeneic Testicular Cell Vaccination Induces Long-Term Anti-Cancer Immunity in Mice

Background/Objectives: Cancer/testis antigen (CTA) gene products are expressed in most malignant tumours, while under normal conditions, their expression is primarily restricted to testicular cells. In this study, we investigated the prophylactic application of a xenogeneic (ram-derived) testicular cell (TC) vaccine for cancer prevention in an experimental animal model. Methods: C57BL/6 mice were immunised three times with either xenogeneic (ram) or syngeneic (mouse) formaldehyde-fixed spermatogenic tissue-derived cells. Following vaccination, mice were implanted with live B16 melanoma or LLC carcinoma cells. Tumour-bearing mice were subsequently assessed for survival and immunological parameters indicative of anti-cancer immunity. Results: Xenogeneic vaccination with TCs induced cross-reactive immune responses to both B16 melanoma and LLC carcinoma antigens (Ags), as determined by the MTT assay. Prophylactic vaccination with xenogeneic TCs (xTCs), but not syngeneic TCs (sTCs), significantly improved survival rates, with 30% of vaccinated mice surviving after LLC carcinoma implantation. The induced immunity was long-lasting, as mice implanted with LLC carcinoma cells 3–6 months post-vaccination exhibited prolonged survival. Furthermore, lymphoid cells from surviving vaccinated mice were capable of adoptively transferring anti-cancer immunity to naïve animals, significantly increasing their survival rates upon subsequent LLC carcinoma cell implantation. Vaccinated mice bearing LLC tumours exhibited a reduction in regulatory CD4⁺CD25⁺Foxp3⁺ T cells in the spleen, with no effect observed in the central memory CD4⁺CD44⁺CD62L⁺ T cell compartment. Moreover, vaccinated mice displayed increased interferon-gamma (IFN-γ) levels in the blood, with no significant changes in interleukin-10 (IL-10) levels. Conclusions: Prophylactic vaccination with xenogeneic CTAs effectively induces long-term, stable anti-cancer immunity, demonstrating potential for future immunopreventive strategies.