TLR9-/- and TLR9+/+ mice display similar immune responses to a DNA vaccine.

Plasmid DNA continues to attract interest as a potential vaccine-delivery vehicle. However, the mechanisms whereby immune responses are elicited by plasmids are not fully understood. Although there have been suggestions regarding the importance of CpG motifs in plasmid immunogenicity, the molecular mechanisms by which CpG motifs enhance immune responses to DNA vaccines are not well understood.