Antioxidative Protection of Squalene Adjuvant and Rabies Vaccine with Adjuvant

The authors verified the possibility of antioxidative protection of squalene adjuvant emulsions by the antioxidants α-tocopherol and β-carotene. They determined the influence of β-carotene on the stability and antigenic effectiveness of adjuvant emulsion in combination with rabies vaccine. The composition of the adjuvant emulsions or vaccines was: 2.5% squalene; 6% detergents; 0.5% antioxidant; 91% water phase. The oxidative injury after UV-irradiation was followed by the detection of the peroxide value of the emulsions. The stability of the emulsions was evaluated by the determination of the emulsion's particle size. The level of rabies antibodies (RAB) in mice sera until day 90 after vaccination, was determined by the rapid fluorescent focus inhibition test. In the in vitro system of squalene adjuvant, α-tocopherol acted as a prooxidant, while β-carotene effectively reduced the oxidative injury. The homogenization of the squalene adjuvant during a prolonged period from 8 to 10 min did not change the particle size. The oxidation processes were efficiently reduced by β-carotene during the preparation process and also during the 70-d storage. The vaccine with β-carotene induced a gradual increase in the RAB levels with the highest value on day 28. While the inactivated rabies vaccine with adjuvant without β-carotene developed a rapid formation of RAB, the application of the vaccine with β-carotene induced a slower but more uniform production of RAB. The level of RAB was significantly higher after the application of the vaccine with β-carotene and reached the protective value of 0.5 IU/mL, in contrast to the vaccine without β-carotene.