Effects of the Toll-like receptor 7 (TLR7) agonist, AZD8848, on allergen-induced responses in patients with mild asthma: a double-blind, randomised, parallel-group study

Leaker, Brian R.; Singh, Dave; Lindgren, Sam; Almqvist, Gun; Eriksson, Leif; Young, Barbara; O’Connor, Brian

The global prevalence of allergic diseases has continued to rise in recent decades, despite some evidence of a trend towards a plateau in asthma prevalence in developed countries [1] . Some epidemiological findings have suggested that this increase may be attributed to a reduced childhood exposure to infection as a result of antibiotics, vaccination and improved sanitation [2, 3] . Thelper (Th) 1, Th2 and T regulatory (T reg ) cells play a vital role in regulating adaptive immune responses to infection [4] . The 'hygiene hypothesis' proposes that a reduction in Th1 or T reg -like responses resulting from lack of exposure to infection during childhood may polarise the immune system towards allergen-reactive Th2-type responses in genetically susceptible individuals. A recent study reported that an Amish farming community exposed to microbial products and lipopolysaccharide (LPS) demonstrated increased innate immune responses and an associated low overall incidence of asthma and allergy [5, 6] .