STIMULATION OF A MEMORY B-CELL RESPONSE DOES NOT REQUIRE PRIMED HELPER T-CELLS

The use of universally immunogenic T cell epitopes, such as those iden tified in tetanus toxin or malaria circumsporozoite protein, could rep resent a major improvement in the development of synthetic vaccines. H owever, one limitation of this approach is the lack of T cell cross-re activity between the vaccine and the pathogen. To determine whether th e memory B cell response elicited by immunization with a synthetic pep tide containing a B cell epitope linked to a T cell epitope can be res timulated by the same B cell epitope linked to different T cell epitop e(s), we used a synthetic peptide which contains non-overlapping B and T cell determinants from hepatitis B surface antigen (HBsAg) of hepat itis B virus (HBV). The results of this study clearly show that primed T cells can increase the antibody response against a B cell epitope l inked to the priming T cell determinant. However, the antibody respons e obtained was weaker than that obtained after two injections of the p eptide containing both B and T cell epitopes, showing the important ro le played by memory B cells in secondary antibody responses. Moreover, a strong antibody response against the B cell epitope was elicited by boosting mice with the B cell epitope linked to a heterologous carrie r, thus demonstrating that a strong B cell memory response can be reve aled in the absence of primed T cells. These results therefore provide new important information for the design of synthetic or recombinant vaccines.