Recombinant GST-I-A beta 28-induced efficient serum antibody against A beta 42.

Six recombinant proteins GST-A beta 28/A beta 35/A beta 42 and GST-I-A beta 28/A beta 35/A beta 42 [I was the abbreviation for an immunostimulatory sequence that consisted of pan HLA DR binding epitope (PADRE) and Tetanus toxin epitope (TT)] were used as antigens after expressed and purified to immunize mice. The strongest antibody response against A beta 42 (titer 1:3200) was achieved by GST-I-A beta 28 or GST-A beta 42 immunization. However, IgG1 and IgG2b were the predominant serum antibody isotype responses by GST-I-A beta 28 immunization, whereas did IgG2a by GST-A beta 42 immunization. Thus, it indicated that GST-I-A beta 28 immunization in a mouse mainly evoked a stronger Th-2-type response; whereas, GST-A beta 42 immunization mainly elicited a Th-1-type response. Moreover, GST-I-A beta 28-induced serum antibodies had higher specificity to A beta 42 monomers and oligomers than to protofibrils and mature fibrils and exhibited the highest efficacy to block A beta 42 aggregation or fibrillogenesis and to disassemble A beta 42 aggregates in vitro. GST-I-A beta 28-induced serum antibodies also showed the most protective and restorative effects on target cells in vitro by inhibiting or neutralizing A beta 42-induced cytotoxicity. All of the above results indicated that A beta 28 could be speculated to substitute for A beta 42 and would become a better antigenic peptide for Alzheimer's disease immunotherapy in the presence of additional Th-cell epitopes such as the immunostimulatory sequence (I) applied in this study.