A study of the efficacy of liposomes in comparison to new and established adjuvants in potentiating the antibody response against hepatitis B virus surface antigen.

The dehydration-rehydration vesicle (DRV) method was used to encapsulate hepatitis B surface antigen (HBsAg) in phosphatidylcholine (PC) and distearoyl phosphatidylcholine (DSPC) liposomes giving entrapment values of 31.7% and 33.1% respectively. A comparison of antibody levels, as determined by ELISA, in the primary and secondary immune responses in mice immunized twice with 1 microgram HBsAg free, or in formulations of PC DRV, DSPC DRV, Syntex Adjuvant Formulation (SAF), alum and Freund's Complete Adjuvant (FCA) showed that by far, FCA was the best adjuvant in both the primary and secondary IgG1, IgG2a and IgG2b responses. In the secondary response, apart from FCA, DSPC DRV and SAF were equally efficacious and better adjuvants than alum and PC DRV for the IgG2a and IgG2b subclasses. SAF was a better adjuvant for HBsAg than alum, DSPC DRV and PC DRV (in descending order of efficacy) in the secondary IgG1 response.