Abstract: Objective To investigate the effect of the compound adjuvant composed of aluminium hydroxide (Al(OH)₃) and coptisine (COP) on humoral immune response induced by hepatitis A virus (HAV) antigen in mice.Methods Forty-nine female ICR mice of 6-8 weeks old were randomly divided into seven groups (7 mice in each group):blank control group (treated with phosphate buffered saline),antigen control group (18 endotoxin unitEUHAV),COP group (HAV 18EU+50 μg COP),(Al(OH)₃) group (18EU HAV+300 μg Al(OH)₃),low,moderate,and high-dose compound adjuvant groups (18EU HAV+300 μg Al(OH)₃+25,50,and 100 μg COP).Blood samples of the mice in different groups were collected at the 4th,8th,12th,and 16th week after the treatments for the detection of serum anti-HAV immunoglobulin G (IgG) with indirect enzyme-linked immunosorbent assay(ELISA).Results After the immunization,serum anti-HAV IgG was detected in the mice of all groups,except for those of blank control,at 4th,8th,12th,and 16th week of the treatment; the serum IgG level of the mice increased first and then decreased with the duration of the treatment and the level reached the highest at 12th week,with the value of log₁₀ (2.908±0.413) for antigen control,log₁₀ (2.960±0.315) for COP group,log₁₀ (3.460±0.295) for Al (OH)₃ group,and log₁₀ (3.460±0.351),log₁₀ (3.470±0.251) and log₁₀(3.470±0.251) for low,moderate,and high-dose compound adjuvant groups,respectively.At the 4th week after the immunization,the serum anti-HAV IgG level of the mice treated with low-dose compound adjuvant was significantly higher than those in adjuvant-free antigen control group and COP group (both P<0.05);at the 8th,12th,and 16th week after the immunization,the serum anti-HAV IgG levels of mice treated with various doses of compound adjuvant were significantly higher than those in adjuvant-free antigen control group and COP group (P<0.05 for all); at the 12th week after the immunization,the serum anti-HAV IgG level of mice treated with Al(OH)₃ was significantly higher than those in adjuvant-free antigen control group and COP group (both P<0.05); at the 16th week after the immunization,the serum anti-HAV IgG level of mice treated with Al (OH)₃ was significantly higher than that in adjuvant-free antigen control group (P<0.05).Conclusion The compound adjuvant composed of appropriate contents of Al (OH)₃ and COP could significantly and rapidly enhance humoral immune responses induced by HAV vaccine in mice; the results suggest that Al (OH)₃ and COP may be used to develope a new type of human vaccine adjuvant.