Propolis Extract vs. Alum as Adjuvants for E. coli Antigens in Rats

Abstract
Vaccines are vital tools in the fight against infectious illness. The choice of an appropriate adjuvant is one of the most crucial steps in vaccine development. Although aluminum salts are still the most widely used adjuvants, numerous novel compounds with improved safety and adjuvant properties have been the focus of the current study.
The focus of this research is the alcoholic extract of local propolis as a natural vaccine adjuvant used with two types of Gram-negative antigens in rats, one with crude and another with killed bacterial antigens, compared with alum hydroxide adjuvants with the same antigens.
The study's findings indicate that there was an increase in the total leukocyte count in all groups compared with the control group (all results are statistically significant (P ˂ 0.05), whereas, the result of G5 which consist of propolis adjuvant vaccine with the whole killed bacteria (PRKI) was not significant), and a notable increase in phagocytosis rates and respiratory burst assessment in the two types of adjuvants compared with the control group (P ˂ 0.0001).
Concerning adaptive immune responses propolis, as a natural adjuvant, was able to stimulate humoral immune responses. However, the alum adjuvant was more potent in this respect, and the difference with the control was statistically significant (p˂ 0.001).
In conclusion, using the propolis vaccine adjuvant was efficient in the induction of responses against Gram-negative antigens.