THE CAPACITY OF A COMBINED LIPOSOMAL HEPATITIS-B AND HEPATITIS-C VACCINE TO STIMULATE HUMORAL AND CELLULAR-RESPONSES IN MICE

Combined hepatitis B surface antigen and hepatitis C antigen were enca psulated into 1, 2, and 5 mu m discrete liposomes and then lyophilized , Groups of adolescent CD-1 mice were given a single 0.3 mL oral dose of these liposomes containing 50 mu g/mL hepatitis B surface antigen a nd hepatitis C antigen, 50 mu g/mL of the same antigens or liposomes a lone. Animals in each group were sacrificed every 2 weeks for 10 weeks and the humoral response investigated by enzyme-linked immunosorbent assay (ELISA) and the cellular response by splenic lymphocyte prolifer ation to 10 mu g of either antigen. Seroconversion to both antigens in the mice receiving liposomal antigens occurred in 87.5% of animals sa crificed at 4 weeks and later. One animal (12.5%) receiving antigen al one seroconverted to hepatitis B virus at 6 weeks, but all animals rec eiving liposomes alone remained negative. Proliferation indexes (PI) g reater than 3 were observed in all animals receiving liposomal antigen s, with the greatest response seen at 10 weeks. PI was less than 2 for all animals In the other two groups. Thus, a single oral dose of lipo somes of three sizes containing both hepatitis B and C antigens given to mice resulted in rapid seroconversion and a progressive robust cell ular immune response, whereas the antigens alone or liposomes without antigen did not.