Both AlloStim® and CRCL can be used as components of therapeutic vaccines. Vaccines generally contain two separate components, an antigen and an adjuvant.
- An antigen is a protein unique to the disease tissue. Antigens are processed internally and presented to the immune system on the surface of the cell in the context of specialized molecules known as Major Histocompatability (MHC) molecules. The ability of the immune system to identify and target a particular cell type depends upon the "antigen fingerprint" of the cell. One or more antigens are used in vaccine formulations to direct an immune response to diseased cells which express the selected antigen(s). Normally, the best antigens are selected based on their expression exclusively on the target cells and not on normal tissues. However, recently it has been shown that expression of surface antigens does not create an effective immune response. Accordingly, antigens from the internal contents of tumors are believed to be the most effective tumor antigens.
- An adjuvant is used to program and boost the desired type of immune response (cellular or humoral) to the selected antigen(s). Humoral immunity causes the production of antibodies which can serve to neutralize disease agents, such as viruses, or block their entry into a cell. However, antibody responses that target surface antigens of tumors are not effective against cancer. Cellular immunity directs an immune response lead by cytolytic T-lymphocytes (CTL). CTL can cause the direct destruction of the target cell. Internal antigens that are processed and presented in conjunction with MHC molecules are the most effective way to elicit tumor-specific CTL cells. Therapeutic cancer vaccines generally require cellular immunity to function ideally, while protective vaccines generally require humoral immunity to function.