Aluminum hydroxide–CpG oligodeoxynucleotide complex (Alum-CpG)

The Aluminum hydroxide–CpG oligodeoxynucleotide complex is a multicomponent adjuvant system designed to enhance the immunogenicity of vaccine antigens. It combines the traditional mineral salt adjuvant, aluminum hydroxide (alum), with synthetic CpG oligodeoxynucleotides (ODNs), which are potent agonists of Toll-like receptor 9 (TLR9) (Krieg et al., 1995, Nature). While alum primarily promotes a Th2-type immune response and creates a depot for slow antigen release, the inclusion of CpG ODN redirects the immune system toward a Th1-type response, characterized by the production of pro-inflammatory cytokines like interferon-gamma and the activation of cytotoxic T cells (He et al., 2015, Human Vaccines & Immunotherapeutics). This synergy allows for lower antigen doses and improved protection against intracellular pathogens and tumors. The complex is not a biological target itself but rather a therapeutic adjuvant system that interacts with TLR9 and the NLRP3 inflammasome to stimulate innate and adaptive immunity (Ghimire, 2015, Journal of Immunology Research). It is widely studied in the context of infectious disease vaccines and cancer immunotherapy to overcome the limitations of alum-only formulations.

Other names

Alum-CpGCpG-AlumCpG-adsorbed aluminum hydroxideAlhydrogel-CpG complex

The complex functions by combining the depot-forming and NLRP3-activating properties of aluminum hydroxide with the TLR9-agonistic activity of CpG oligodeoxynucleotides, resulting in a synergistic enhancement of Th1-type immune responses (He et al., 2015; Ghimire, 2015).