Oil-based emulsion vaccine adjuvants.

Vaccine adjuvants are critical components in experimental and licensed vaccines used in human and veterinary medicine. When aiming to evoke an immune response to a purified antigen, the administration of antigen alone is often insufficient, unless the antigen contains microbial structures or has a natural particulate structure. In most cases, the rationale to use an adjuvant is obvious to the experimental immunologist or the professional vaccinologist, who is familiar with the nature of the antigen, and the aim of the vaccine to elicit a specific antibody response and/or a specific type of T cell response. In this unit, we describe protocols to formulate antigens with oil-based emulsions. Such emulsions represent a major prototype adjuvant category that is frequently used in experimental preclinical vaccines, as well as veterinary and human vaccines.

The use of oil adjuvants in therapeutic vaccines.

Water in oil emulsions represents one of the new promising generations of adjuvants for immunotherapy. Fifty years ago, incomplete freund adjuvant (IFA) has been used in clinical trials for prophylactic vaccines like poliomyelitis or flu vaccine because of its strong potency. However, even if the quality of the raw materials has been improved in order to avoid secondary reactions, the risk benefit ratio was not favorable to its use for prophylactic vaccines. Moreover, emulsions were highly viscous with a weak stability. The development of new adjuvants concepts like liposomes, oil in water emulsions, bacterial immunostimulating compounds has induced a loss of interest for such formulations. The emergence of immunotherapy treatments for cancer, AIDS or other diseases leads to the re-emergence of these adjuvants, as the risk benefit ratio is more favorable. Then, safety of these adjuvants has been improved by the use of more specific surfactants and refined oils but also by improving their manufacturing process, allowing even sometimes their use in clinical trials for prophylactic vaccines.