Construction of Hybrid Gene of Hepatitis B Surface Antigen Carrying Heat- Stable Enterotoxin of Escherichia coli and Its Expression in Mammalian Cell Line.

Hepatitis B surface antigen is the first genetically engineered vaccine licensed for human use. Various strategies have been proposed to obtain a vaccine that would bypass the need for injection. In this study, a non-toxic portion of heat-stable enterotoxin of Escherichia coli that is capable of adhering to epithelial cells was inserted at amino acid position 112 of hepatitis surface antigen. The construct was used for transfection of human embryonic kidney cells in order to assess the expression of the hybrid protein. The data obtained showed a very low level of expression. In vivo antibody production and cytotoxic T lymphocyte response in B6 mice were assessed using DNA immunization. Three out of five injected mice responded with titers >10 mIU/ml anti-HBsAg and cytotoxic T-lymphocyte response was much higher with construct encoding the chimeric protein. Although this study proves that the chimeric protein is capable of eliciting both humoral and cellular responses, but further work is required to fully explore the feasibility of combining the properties of the two proteins.