Abstract: Oil-based adjuvant emulsions, immunogenic compositions, and methods of using the same to elicit immunological responses in a subject are provided. The oil-based adjuvants comprise a plant-derived surfactant, such as gum arabic, an aqueous component, and an oil. The adjuvant emulsions can be used to potentiate the immunological effects of active agents, including antigens derived from various pathogens and/or toxins. Immunogenic compositions comprising the adjuvant emulsions and various active agents are also provided, along with vaccine systems for therapeutic or prophylactic treatment of a subject using these adjuvants.