Basic research in immunology, epidemiology, natural history and vaccine trials in animal models and humans all contribute to a greater understanding of the immune system breakdown and of how new vaccines may be designed to prevent or slow down the progress of HIV disease. Because of safety concerns, most candidate HIV vaccines use one or more synthetic proteins of HIV, not the whole infectious virus. These new generation vaccines contain no intact live virus and thus, appear to stimulate less potent immune responses than traditional vaccines made from whole viruses that have been inactivated or attenuated. To augment the immune responses elicited by these and other vaccines, scientists use immunologic adjuvants, which can increase the type, strength, and durability of immune responses evoked by a vaccine. Some vaccine adjuvant combinations can induce cellular immune responses in animals, even if the vaccine antigen by itself does not.
Some adjuvants also stimulate mucosal immunity.
An adjuvant may work well with one experimental vaccine but not another. Therefore, FDA licenses the vaccine- adjuvant combination, rather than the adjuvant alone. Alum primarily increases the strength of antibody responses generated by the vaccine antigen. Because of alum's limited activity, other adjuvants now being evaluated in animal models and human studies may be better suited for the newer candidate HIV vaccines. An effective way to enhance immune responses to HIV is the combination approach.