TLR9 and allergic disease: Since the TLR9 agonist CpG had demonstrated promise in allergen-free immunotherapy against allergy in previous studies4, 7, 10, we therefore hypothesized that by improving its targeting to lung-resident DCs and lung LNs, conjugation to ultrasmall NPs could allow the same dose of CpG to yield greater efficacy in preventing and treating airway allergy.