As one of the scheduled immunization vaccines worldwide, virtually all individuals have been vaccinated with BCG vaccine. In order to verify the hypothesis that delivering BCG high-affinity peptides to tumor areas could activate the existing BCG memory T cells to attack tumor, we firstly predicted the HLA-A*0201 high-affinity peptides of BCG Ag85A protein (KLIANNTRV, GLPVEYLQV), and then, A375 melanoma cells and HLA-A*0201 PBMCs (from PPD-positive adults) were added to co-incubated with the predicted peptides in vitro. We found that the predicted BCG high-affinity peptides could be directly loaded onto the surface of tumor cells, enhancing the tumor-killing efficacy of PBMCs from PPD-positive volunteer. Then, we constructed PPD-positive mice model bearing B16F10 subcutaneous tumors and found that intratumor injection of BCG Ag85A high-affinity peptides (SGGANSPAL, YHPQQFVYAGAMSGLLD) enhanced the anti-tumor efficacy in PPD-positive melanoma mice. Along with the better anti-tumor efficacy, the expression of PDL1 on tumor cell surface was also increased, and stronger antitumor effects occurred when further combined with anti-PD1 antibody. For microenvironment analysis, the proportion of effector memory T cells was increased and the better treatment efficacy may be attributed to the elevated effector memory CD4 + T cells within the tumor. In conclusion, using the existing immune response of BCG vaccine by delivering high-affinity peptides of BCG to tumor area is a safe and promising therapy for cancer.

卡介苗作为全球预定免疫疫苗之一，几乎所有个人都接种过卡介苗。为了验证将BCG高亲和力肽递送到肿瘤区域可以激活现有的BCG记忆T细胞攻击肿瘤的假设，我们首先预测了BCG Ag85A蛋白的HLA-A*0201高亲和力肽（KLIANNTRV，GLPVEYLQV） ，然后添加 A375 黑色素瘤细胞和 HLA-A*0201 PBMC（来自 PPD 阳性成人）与预测的肽在体外共孵育。我们发现预测的BCG高亲和力肽可以直接负载到肿瘤细胞表面，增强PPD阳性志愿者的PBMC的杀伤功效。然后，我们构建了携带B16F10皮下肿瘤的PPD阳性小鼠模型，发现瘤内注射BCG Ag85A高亲和力肽（SGGANSPAL、YHPQQFVYAGAMSGLLD）增强了PPD阳性黑色素瘤小鼠的抗肿瘤功效。在更好的抗肿瘤功效的同时，肿瘤细胞表面PDL1的表达也增加，进一步与抗PD1抗体联用会产生更强的抗肿瘤作用。对于微环境分析，效应记忆T细胞的比例增加，更好的治疗效果可能归因于肿瘤内效应记忆CD4+T细胞的增加。总之，利用卡介苗现有的免疫反应，将卡介苗的高亲和力肽递送至肿瘤区域，是一种安全且有前景的癌症治疗方法。