CpG oligodeoxynucleotides as a future vaccine for allergic diseases

An astounding feature of the DNA sequences termed CpG motifs is the induction of immune and inflammatory responses in a senseless manner. CpG motifs exist abundantly in microbes and evoke innate immunity that constitutes the first line of defense against microbial infections in vertebrates. CpG motifs that essentially work in an antigen-nonspecific fashion, however, turn into novel immunomodulators that can manipulate acquired immunity in an antigen-specific manner if oligodeoxynucleotides containing CpG motifs (CpG ODNs) are directly conjugated to the antigen. CpG ODNs with potent polyclonal Th1-inducing ability show promise for application in immunotherapy whereby neutralization of dominant allergy-prone Th2 cells is achieved by inducing allergen-specific Th1 cells. The underlying mechanisms include an unexpected enhancement of dendritic cell function as a linker between innate and acquired immunity. In the foreseeable future the mainstream therapeutic role of corticosteroids in anti-inflammatory therapy for allergic diseases could possibly be replaced by immunotherapy using CpG ODN-conjugated antigens.