Moving from peanut extract to peanut components: towards validation of component-resolved IgE tests.

BACKGROUND: Replacement of peanut extracts by recombinant peanut components is an important step in allergy serologic testing. Criteria are needed for the unbiased inclusion of patients into a study to validate such a replacement. METHODS: Plasma samples from 64 peanut-positive children (42 reactors, 22 nonreactors in a double-blind, placebo-controlled food challenge) were used to compare IgE reactivity to six recombinant peanut allergens with reactivity to natural peanut proteins extracted at neutral or low pH. We tested the hypothesis that poor extractability of Ara h 9 and other basic allergens at neutral pH leads to under-representation of patients with such sensitization. RESULTS: IgE reactivity to the components did not fully explain IgE reactivity to peanut extract in 5 of 32 reactors with IgE to peanut extract ≤100 kUA /l. IgE reactivity to components was stronger than to the extract in 11 plasma samples, which was largely due to a low Ara h 8 reactivity of the extract. IgE reactivity to Ara h 9 was much lower than reactivity to other basic proteins, some of which bound IgE well in the RAST, but lost IgE reactivity upon immunoblotting. CONCLUSIONS: Conventional peanut extracts are deficient in significant IgE-binding components. The inclusion of patients for a validation study should be based on serology performed with improved peanut reagents to avoid a bias against these under-represented, potentially important allergens. To judge clinical relevance of an allergen, the reagent used for inclusion of patients needs to be efficient in detecting IgE to this component.

Efficacy of birch-pollen immunotherapy on cross-reactive food allergy confirmed by skin tests and double-blind food challenges.

BACKGROUND: The effect of birch-pollen immunotherapy (IT) on cross-reactive food allergies is controversial. OBJECTIVE: The aim of this study was to investigate the effect of birch-pollen IT on apple allergy and to evaluate recombinant allergens and double-blind placebo-controlled food challenges (DBPCFCs) as monitoring tools. METHODS: Twenty-five adult birch-pollen- and apple-allergic patients were randomly divided into two groups, either receiving birch-pollen IT or symptomatic drugs only. IgE and IgG4 antibodies against birch pollen, apple, natural Bet v 1 and Mal d 1 were measured. In addition, skin prick tests (SPT) were performed using recombinant Bet v 1 (rBet v 1) and Mal d 1 (rMal d 1). Clinical outcome was evaluated by DBPCFC. CD4(+)CD25(+) regulatory T cells (Tregs) were isolated from peripheral blood and tested in functional assays. RESULTS: Birch-pollen IT resulted in a significant decrease of SPT reactivity for rBet v 1 (30-fold) and rMal d 1 (10-fold) already after 3 months. IgG4 antibodies were potently induced against Bet v 1, displaying cross-reactivity to Mal d 1. Visual analogue scale scores decreased >10-fold in 9/13 patients of the IT group, with three patients converting to negative. In the control group, no decrease was observed. Birch-pollen IT did not lead to detectable changes in the number or function of the CD4(+)CD25(+) Tregs. CONCLUSIONS: This trial supports the claims that birch-pollen IT also decreases allergy to foods containing Bet v 1-homologous allergens. Recombinant allergens and DBPCFCs have proven to be useful tools for monitoring the effect of birch-pollen IT on linked food allergies.

Medical therapy of patients with reflux oesophagitis poorly responsive to H2-receptor antagonist therapy.

There is substantial clinical experience of omeprazole treatment in patients with reflux oesophagitis, who have an incomplete or failed response to profound and prolonged acid-inhibitory therapy with H2-receptor antagonists. In The Netherlands, most patients with reflux oesophagitis poorly responsive to high-dose H2-receptor antagonists were healed within 3 months of treatment with omeprazole, 40 mg once daily. Only a few patients (less than 10%) with complicated reflux oesophagitis needed a longer duration of treatment or a higher dose of omeprazole to achieve complete endoscopic healing. Follow-up for up to 6 years has shown that most of these patients could be maintained successfully on omeprazole, 20 mg daily. However, about one third of the patients relapsed after healing when the maintenance dose was introduced. Evaluation of these patients who relapsed has shown that they require a higher level of acid-secretory inhibition; a maintenance dose of omeprazole, 40 mg once daily, rehealed the oesophagitis within 3 months. Only a few patients had a second relapse, and these patients were rehealed by an increase of the omeprazole dose to 60 mg daily. Oesophageal pH monitoring in these patients has shown that there is continued pathological oesophageal acid exposure, predominantly during the night, suggesting that the duration of major action of omeprazole was insufficient for production of adequate elevation of intragastric pH during the night. Successful control of reflux disease in these patients was achieved by increasing omeprazole therapy to a regime and dosage that achieved elevation of intragastric pH above 4 throughout the 24-hour period.

Management of gastro-oesophageal reflux disease. Are there alternatives to omeprazole?

Several studies have clearly demonstrated that omeprazole is highly efficacious in the management of patients with gastro-oesophageal reflux disease. In particular, wherever H2-receptor antagonists fail to produce results--in patients with severe disease--omeprazole has been shown to be of major value. However, new alternatives are forthcoming; a new generation of more potent H2-receptor antagonists will be available, while 24 pH studies with high-dose ranitidine have shown that acid reflux is suppressed more efficiently than with standard doses. The prokinetic drug cisapride appears to be of importance, not only in the management of patients with mild reflux disease, but also of cases with severe disease when cisapride is combined with a H2-receptor antagonist. Such a combination could also be of value as an alternative to omeprazole in long-term therapy, since it has not yet been shown that indefinite treatment with omeprazole of patients with reflux disease will be safe. In addition, the value of long-term sucralfate, effective in short-term therapy, needs to be evaluated in patients with chronic reflux disease who will not be operated. In forthcoming studies, it will be advisable to incorporate 24-hour pH measurements to detect periods of nonacid suppression more accurately. The future of medical management of gastro-oesophageal reflux disease appears to be promising.

The effects of omeprazole and ranitidine on 24-hour pH in the distal oesophagus of patients with reflux oesophagitis.

Ambulatory 24-h pH monitoring in the distal oesophagus was performed in seven patients with erosive or ulcerative reflux oesophagitis to compare the effects of omeprazole and ranitidine in the management of gastro-oesophageal reflux disease. In a double-blind, crossover study patients were treated with either 60 mg o.m. omeprazole or 150 mg b.d. ranitidine. The pH measurements were performed before treatment and on the fourteenth day of treatment with either regimen. The total acid exposure time (percentage total time pH less than 4) was abnormal in six out of seven patients before treatment. During treatment with omeprazole the acid exposure time of five patients was normal in comparison with only two patients during ranitidine therapy. However, even with a rather high dose of omeprazole, pathological gastro-oesophageal reflux may still occur.