Immunogenicity of PELA microsphere encapsulated hepatitis B vaccine

Objective To investigate the immunogenicity of [poly dl lactide poly (ethylene glycol),PELA]encapsulating hepatitis B surface antigen (HBsAg) expressed by Hansenular polymorpha. Methods Encapsulated HBsAg microspheres were administered to BALB/c mice. The anti HBs of PELA microsphere vaccine and HBsAg/microsphere vaccine immunization were detected by solid radioimmunoassay. IgG subclass was titred by ELISA. In the respect of cellular immunity, By using PELA·HBsAg as immunogens, splenic mononuclear cells (MNC) were prepared at 5 , 10 , 15 , 20 and 25 day after immunization respectively. The proliferation of MNC induced by Con A or LPS was assayed. T lymphocyte proliferation tests of the specific antigens and lymphocyte subpopulations were determined. The delayed type hypersensitivity (DTH) determined by footpad swelling using sheep red blood cells (SRBC) as sensitinogen was also tested. Cytotoxic T lymphocyte(CTL )activity was tested by 51 Cr release assay against P815 HBsAg. Results ① The anti HBs titer of HBsAg/microsphere vaccine immunization was 85mIU/ml while that of HBsAg with alum was 36mIU/ml. ② The ratio of IgG2a and IgG in PELA microsphere vaccine and HBsAg/PELA microsphere vaccine was significantly higher than that of HBsAg with alum ( P 0.05 ). ③ On the 25th day after injection, the SI of Con A or LPS induced proliferation of spleen MNC from mice immunized with PELA·HBsAg was 133.59, 47.48, which was significantly higher than those of Al(OH) 3 HBsAg and HBsAg( P 0.05). ④ PELA·HBsAg significantly improved SRBC induced DTH response of mice ( P 0.05 ). ⑤ The specific cytolytic activity of splenocyte of mice immunized with PELA·HBsAg microsphere vaccine was significantly higher than that of other groups ( P 0.05). Conclusion PELA had the function to improve the HBsAg induced humoral and cellular immunities,and also played a role in control release of the immune effects of the antigens.