Self-Tumor Antigens in Solid Tumors Turned into Vaccines by α-gal Micelles Immunotherapy

A major reason for failure of the immune system to detect tumor antigens (TA) is the insufficient uptake, processing, and presentation of TA by antigen-presenting-cells (APC). Immunogenicity of public and private TA of the individual patient can be markedly increased by in situ targeting of tumor cells for uptake by APC, without the need to identify and characterize the TA. This is feasible by intra-tumoral administration of alpha-gal micelles comprised of glycolipids presenting the carbohydrate-antigen “alpha-gal epitope” (Galalpha1-3Gal beta1-4GlcNAc-R). Humans produce a natural antibody called “anti-Gal” (constituting ~1% of immunoglobulins) which binds alpha-gal epitopes. Tumor injected alpha-gal micelles spontaneously insert into tumor cell membranes, so that multiple alpha-gal epitopes present on tumor cells. Anti-Gal binding to these epitopes activates the complement system, resulting in killing of tumor cells, and recruitment of multiple APC (dendritic cells and macrophages) into treated tumors by chemotactic complement cleavage peptides C5a and C3a. In this process of converting the treated tumor into personalized TA vaccine, recruited APC internalize anti-Gal opsonized tumor cells and cell membranes, process the internalized TA and transport them to regional lymph-nodes. TA peptides presented on APC activate TA specific T and B cells to proliferate and destroy metastatic tumor cells presenting the TA. Studies in anti-Gal producing mice demonstrated induction of effective protection against distant metastases of the highly tumorigenic B16 melanoma following injection of natural and synthetic alpha-gal micelles into primary tumors. This treatment was further found to synergize with anti-PD1 antibody. Phase-1 clinical-trials indicated that this immunotherapy is safe and can induce infiltration of CD4+ and CD8+ T cells into untreated distant metastases. It is suggested that in addition to converting treated metastases into autologous TA vaccine, this treatment should be considered as neo-adjuvant therapy administering alpha-gal micelles into primary tumors immediately following their detection. Such immunotherapy will convert tumors into personalized anti-TA vaccine for the period prior to their resection.