Abstract
Combined hepatitis B surface antigen and hepatitis C antigen were encapsulated into 1, 2, and 5 μm 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 μg/mL hepatitis B surface antigen and hepatitis C antigen, 50 μg/mL of the same antigens or liposomes alone. 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 proliferation to 10 μg of either antigen. Seroconversion to both antigens in the mice receiving liposomal antigens occurred in 87.5% of animals sacrificed at 4 weeks and later. One animal (12.5%) receiving antigen alone seroconverted to hepatitis B virus at 6 weeks, but all animals receiving liposomes alone remained negative. Proliferation indexes (PI) greater than 3 were observed in all animals receiving liposomal antigens, 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 liposomes of three sizes containing both hepatitis B and C antigens given to mice resulted in rapid seroconversion and a progressive robust cellular immune response, whereas the antigens alone or liposomes without antigen did not.
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