Production of antibodies with peptide-CpG-DNA-liposome complex without carriers

We present that a particular form of natural phosphodiester bond CpG-DNA encapsulated in a specific liposome complex (Lipoplex(O)) induces potent immunomodulatory activity in humans as well as in mice. Additionally, Lipoplex(O) enhances the production of IgG2a specific to antigenic protein in mice. Most importantly, immunization of mice with several peptides co-encapsulated with Lipoplex(O) without carriers significantly induces each peptide-specific IgG2a production in a TLR9-dependent manner. A peptide-specific monoclonal antibody produced against hepatocellular carcinoma-associated antigen has functional effects on the cancer cells.Our overall results show that Lipoplex(O) is a potent adjuvant and that complexes of peptide and Lipoplex(O) are extremely useful for B cell epitope screening and antibody production without carriers. Therefore, our strategy may be promptly used for the development of therapeutic antibodies by rapid screening of potent B cell epitopes.Synthetic oligodeoxynucleotides (ODNs) and bacterial DNA containing unmethylated CpG dinucleotides flanked by specific base sequences (CpG-DNA) have significant immunomodulatory effects on B lymphocytes, macrophages, dendritic cells, and natural killer cells [1-4]. Experimental evidence suggests that CpG-DNA induces the regulation of Th1/Th2 immune responses, antigen-presenting cell activity, and immunoglobulin (Ig) isotype switching [5-7]. Therefore, CpG-DNA has gained attention for its potential use as an immune adjuvant and in therapeutics for allergic and infectious diseases [8,9].Phosphorothioate-modified types of CpG-DNA (PS-ODN), which are resistant to nuclease activity and can be efficiently delivered into cells [10,11], have been utilized in clinical applications [9]. The immunomodulatory activities of PS-ODN are enhanced by liposome-encapsulation [12-14]. However, several studies have suggested that PS-ODN induces backbone-related side effects, such as transient splenomegaly [15], lymphoid folli