A competitive solid-phase radioimmunoassay for quantitation of the major allergen of Parietaria pollen

Safety of inhalant allergen immunotherapy with mass units-standardized extracts

BACKGROUND

Allergen-specific immunotherapy (SIT) is an effective treatment for patients with respiratory allergies. However, subcutaneous injection of allergens can provoke systemic side-effects.

OBJECTIVE

This study was carried out to determine the incidence and risk factors o fsystemic reactions caused by SIT treatment, using extracts of different inhalant allergens, adsorbed in aluminium hydroxide and biologically standardized with the major allergens quantified in mass units.

METHODS

Five hundred and fifty-five subjects with allergic rhinitis and/or asthma were evaluated on clinical history and skin prick test (SPT) reactions to common inhalant allergens. Subcutaneous SIT was administered to all patients, according to the suggested precautionary guidelines and administration schedule. Patients were treated with house dust mite, grass pollen, Parietaria judaica pollen and olive pollen extracts, each receiving one or two extracts.

RESULTS

A total of 36,359 injections were administered in the 555 patients. We observed 34 episodes of serious systemic side-effects (0.093% of all injections), in 29 patients (5.2% of all patients), and no fatalities. About 55% of patients reported mild rhinitis and asthma. The majority (59%) of the serious systemic reactions (SSR), and all the anaphylactic reactions, were immediate (i.e. occurred within 30 min after the injection). Asthmatic subjects were at higher risk of SSR than patients with rhinitis (P = 0.01). Most of the side-effects observed occurred during the dose-increase phase (P < 0.05). There was no association of SSR with age, gender, SPT reactivity or allergen type.

CONCLUSION

SIT performed in patients with respiratory allergies by specialized staff with the allergen extracts studied, standardized in mass units, provoked a low rate of SSR. The significant risk factors for systemic reactions were asthma and the build-up period.

Sublingual immunotherapy: a double-blind, placebo-controlled trial with Parietaria judaica extract standardized in mass units in patients with rhinoconjunctivitis, asthma, or both

BACKGROUND

New routes of administering immunotherapy in respiratory allergy are being studied as an alternative to conventional injective immunotherapy. We carried out a study to evaluate the clinical efficacy and effects of sublingual immunotherapy in patients with Parietaria judaica-induced respiratory allergy.

METHODS

A double-blind, placebo-controlled design was followed. Thirty patients with P. judaica rhinoconjunctivitis, mild asthma, or both were randomly chosen for sublingual immunotherapy (14 patients) or placebo treatment (16 patients). The patients underwent preseasonal rush induction treatment followed by coseasonal maintenance treatment during the Parietaria pollen season. Symptom and drug scores, as well as specific IgE and specific IgG4, were recorded.

RESULTS

Significantly lower symptom and drug scores were found (P=0.04), especially during the Parietaria pollination period, in the immunotherapy group. No significant difference in specific IgE and specific IgG4 was detected between the active and placebo groups; a statistically significant increase of specific IgE was detected in both groups (P=0.05). No patient undergoing active sublingual immunotherapy reported local or systemic side-effects.

CONCLUSIONS

Our data suggest that sublingual immunotherapy is both clinically effective and safe in treating patients with Parietaria-induced rhinoconjunctivitis and mild asthma.

Role of carbohydrate moieties in cross-reactivity between different components of Parietaria judaica pollen extract

Cross-reactivity between the different components in Parietaria judaica pollen extract has been investigated by polyclonal as well as monoclonal antibodies before and after chemical deglycosylation obtained by trifluoromethanesulphonic acid (TFMS) treatment of the extract. In western blotting a polyclonal rabbit antiserum, obtained by injecting purified Par j I, was able to recognise many components of the native extract. However, its reactivity was restricted, after chemical deglycosylation of the extract, to the major allergen alone, indicating that its cross-reactivity was due to sugar moieties. Moreover, out of several monoclonal antibodies raised by injecting the whole Parietaria judaica extract, one (1A4/2F8) was also able in western blotting to recognise an epitope shared by many components of the extract except the major allergen Par j I. However, in this case the broad reactivity of the antibody was not affected by the deglycosylating procedure. When the reactivity of Parietaria judaica extract was tested before and after sugar removal, against specific IgE from a pool of patient sera, no differences could be demonstrated, thus indicating that carbohydrates are not strongly involved in the binding of Parietaria judaica-specific IgE. The results indicate that both proteic and carbohydratic cross-reactive epitopes are shared by many components of Parietaria judaica pollen extract.

Monoclonal antibody based radioimmunoassay for the quantitation of the main cat allergen (Fel d I or Cat-1)

A two-site solid-phase radioimmunoassay has been developed for the quantitation of the main cat allergen, Fel d I or cat allergen 1. The assay is based on two different monoclonal antibodies which recognize different epitopes on the Fel d I molecule; one antibody (C5/24) was immobilized on the solid phase and the other (C5/8) was labeled with 125I, being the allergen molecule sandwiched between them. The assay is specific for the Fel d I molecule and sensitive enough to detect as little as 0.25 ng/ml of allergen. The Fel d I RIA was compared with a radial immunodiffusion technique for the determination of allergen levels in several cat extracts and a good quantitative correlation was found. The same good correlation was found when the results obtained with the Fel d I RIA were compared with the determination of the total allergenic activity by RAST inhibition. The results indicate that the MAb RIA could be very useful in the standardization of allergenic extracts from feline origin.