Effect of adjuvant on pharmacokinetics, organ distribution and humoral immunity of hepatitis B surface antigen after intramuscular injection to rats

Two types of radioiodinated plasma driven antigens, heat-inactivated ( ¹²⁵I-h-HBsAg) and formalin- inactivated HBsAg (¹²⁵I-f- HBsAg) were investigated for the effect of immunoadjuvant, aluminium phosphate (AP) on pharmacokinetics, organ distribution and humoral immunity of differently inactivated hepatitis B surface antigens (HBsAg) in rats. As a result, most of h- HBsAg (90%) was retained and slowly eliminated from the injection site. The h-HBsAg was highly localized in regional lymph node (RLN), but resulted in low humoral immune response. On the other hand, f-HBsAg was less localized in the injection site and RLN, but mainly distributed into serum and liver (62.9 and 22.4%, respectively). However, both h-HBsAg and f- HBsAg slowly disappeared from the injection site with AP, resulting in the increased area under the amount-time curve (AUQ) of h-HBsAg and f-HBsAg in the injection site. Exposures of h-HBsAg and f-HBsAg in serum were increased (1.4 and 2.8 times increase in AUC, respectively) with AP. The RLN uptake of both antigens were dramatically increased (25 and 3.1 times increase in AUC, respectively) with higher humoral immune response. The antibody titres were also increased with AP. In conclusion, pharmacokinetics, organ distribution and humoral immunity of h-HBsAg were highly dependent on the inactivation method of antigen and the presence of immunoadjuvant such as AP.