A double-blind, placebo-controlled study of immunotherapy with an alginate-conjugated extract of Parietaria judaica in patients with Parietaria hay fever.

A double-blind, placebo-controlled study was conducted to evaluate the efficacy and safety of immunotherapy (IT) with a partially purified alginate-conjugated extract of Parietaria judaica (Conjuvac Parietaria, Dome/Hollister-Stier) in patients suffering from rhinoconjunctivitis caused by Parietaria pollen. Eighteen patients (10 women, 8 men, mean age 35 years) received active treatment and 17 (10 women, 7 men, mean age 42.5 years) received placebo. Actively treated patients had significantly lower nasal symptom/medication scores (running nose P = 0.0087 and sneezing P = 0.048) during the Parietaria pollen season. Significant decreases in specific skin (P < 0.01), nasal (P < 0.05), and conjunctival (P < 0.01) reactivity to the Parietaria extract and significant increases of specific IgG (P < 0.001), IgG1 (P < 0.001), and IgG4 (P < 0.001) in actively treated patients, but not in placebo, were found. IT was well tolerated, the active extract inducing five mild systemic reactions (four rhinitis and one urticaria) and placebo two (rhinitis). A significant correlation was found between low skin reactivity and high specific IgG (P = 0.0002) and IgG4 (P = 0.036). These findings indicate that IT with a partially purified P. judaica extract is an effective and safe treatment for Parietaria pollen allergy. The correlation between low immediate skin reactivity and high specific IgG and IgG4 suggests that, at least in the studied cutaneous model, these antibodies may exert a blocking effect.