Evaluation of two grass pollen extracts for immunotherapy by serum determinations of specific IgE and IgG4 antibodies towards purified Timothy grass pollen allergens (Phl p 1, 2, 4, 5, 6, 7, 11, 12) in patients undergoing hyposensitization treatment

Abstract

The diagnosis of allergic diseases with recombinant allergens allows us to detect antibodies specific for single allergens in extracts. The aim of the present study was to assess the early effect of grass pollen immunotherapy on IgE and IgG4 responses to eight purified grass pollen allergens in patients undergoing hyposensitization treatment. The sera of 22 consecutive atopic individuals undergoing cluster regimen grass pollen immunotherapy were analyzed for IgE and IgG4 antibodies specific for grass pollen allergens (Phl p 1, 2, 4, 5, 6, 7, 11, 12). Two serum samples were taken, one before the start of therapy and one between 12 and 15 weeks after the first immunization. Immunotherapy was performed with two allergy vaccines comprising a standardized extract aluminum-adsorbed grass pollen mix and a standardized extract of grass pollen mix adsorbed onto calcium phosphate. One treated patient showed a specific IgE conversion from negative (< 0.35 kUA/L) to positive in the capsulated hydrophilic carrier polymer (CAP) test for Phl p 2, 1 and 4 (1.89, 0.84 and 0.68 kUA/L, respectively). The sera of 10 of 11 patients treated with alluminum-adsorbed grass pollen extract showed a significant increase in specific IgG4 towards natural Timothy grass pollen extract and purified allergens, as well as significant IgG4 levels towards Phl p 1 ( P = 0.000238) Phl p 2 ( P = 0.000289), Phl p 4 ( P = 0.000585), Phl p 5 ( P = 0.000364), Phl p 6 ( P = 0.000346) and Phl p 11 ( P = 0.039623; Mann–Whitney U-test) 12 weeks after the onset of immunotherapy. The sera of seven of 11 subjects treated with calcium phospate-adsorbed grass pollen extract had significant IgG4 levels against Timothy pollen allergens, as well as significant IgG4 titers against Phl p 1 ( P = 0.004703), Phl p 4 ( P = 0.000282), Phl p 5 ( P = 0.015480), Phl p 6 ( P = 0.013012) and Phl p 11 ( P = 0.005178). Patients treated with aluminum-adsorbed grass pollen extract had higher levels of IgG4 towards Phl p 2, 4 and 6 and natural Timothy grass extract compared with patients treated with calcium phosphate-adsorbed grass pollen extract. Both the alluminum-adsorbed and calcium phosphate-adsorbed grass pollen extract allergy vaccines induced significant titers of specific IgG4 towards Phleum pratense pollen extract ( P = 0.008376 and 0.01148, respectively). These results indicate that grass pollen immunotherapy elicits an array of antibody specificities that reflect the allergen content and the potency of allergen extracts; this could be of pivotal importance to define optimal allergen extract doses.