Ragweed-specific IgE Antibody Research Articles

Design of an Epitope-Based Peptide Vaccine Against the Major Allergen Amb a 11 Using Immunoinformatic Approaches.

Allergic diseases are a socially significant problem of global importance. The number of people suffering from pollen allergies has increased dramatically in recent decades. Pollen allergies affect up to 30% of the world population. Pollen of the common ragweed (Ambrosia artemisiifolia L.) is one of the most aggressive allergens in the world. We have used a series of immunoinformatics approaches to design an effective epitope-based vaccine, which might induce a competent immunity against a major allergen Amb a 11. CD8+ and CD4+ T-cell epitopes and their corresponding MHC restricted alleles were identified by prediction tools provided by immune epitope database (IEDB). Among T-cell epitopes, MHC class I peptide (GLMEPAFTYV) and MHC class II peptide (LVCFSFSLVLILGLV) were identified as most suitable. From all predicted B-cell epitopes, only one epitope (GKLVKFSEQQLVDC) containing sequence from the conserved region was chosen for next processing. Selected epitopes have been validated by molecular docking analysis. These epitopes showed a very strong binding affinity to MHC I molecule and MHC II molecule with binding energy scores − 729.3 and − 725.0 kcal/mole respectively. Performed experimental validation showed that only the MHC class II peptide (LVCFSFSLVLILGLV) can stimulate T cells from ragweed allergic patients and IgE antibodies specific to the ragweed pollen do not recognize this epitope. Therefore, this peptide could be potentially used as a vaccine against the major allergen Amb a 11. The B-cell epitope GKLVKFSEQQLVDC forms a stable complex with the IgE molecule (energy weighted score − 695,0 kcal/mole). Tested sera from patients with ragweed allergy showed that the ragweed specific IgE antibodies can bind to the identified B-cell epitope. Population coverage analysis was performed for CD8+ and CD4+ T-cell epitopes. It was predicted that CD4+ T-cell epitope (LVCFSFSLVLILGLV) covers 90.56% of the population of Europe and 99.36% of the world population. CD8+ T-cell epitope (GLMEPAFTYV) has a population coverage of 77.37% for Europe and 71.35% for all the world.

Intranasal steroids inhibit seasonal increases in ragweed-specific immunoglobulin IE antibodies

We performed two seasonal studies to evaluate the effect of continuous treatment with intranasal steroids, beginning approximately 1 week before the apperance of ragweed pollen, on the level of ragweed-specific IgE antibodies in serum. In both studies the control groups showed the anticipated rise in ragweed-specific IgE antibodies after the ragweed season. In the first study, employing aqueous beclomethasone dipropionate (168 μg twice daily), no rise occurred in serum ragweed IgE after seasonal exposure and the level actually decreased in eight of 12 treated subjects. In the second study, with triamcinolone acetonide (220 μg twice daily), the expected rise in ragweed IgE antibody was also reduced, although less dramatically, probably as a result of the lower potency of the dose delivered. Our studies not only support the benefits of intranasal steroids in the treatment of seasonal allergic rhinitis but also suggest that specific IgE production may be down-regulated by their continuous use, which may alter the subsequent clinical course of the disease.

Polyethylene glycol-modified ragweed pollen extract in rhinoconjunctivitis

Sixty-two ragweed-sensitive adult subjects volunteered to take part in a 2-year, placebo-controlled efficacy study of polyethylene glycol (PEG)-modified ragweed extract, in ragweed pollen-induced rhinoconjunctivitis. At the beginning of the study, subjects were stratified according to skin sensitivity to ragweed extract and PEG-modified ragweed and the severity of hay fever in the previous year. There was random allocation of half to active treatment and half to placebo treatment. Before the first ragweed pollen season the 36 most sensitive subjects received 10 weekly injections (group 1), and the remaining 26 received six injections (group 2). Before the second season all subjects received 10 injections. Doses increased by half a log concentration each week unless there were adverse reactions. The mean total dose received by group 1 in year 1 was 385 μg of protein (28.9 μg AgE) and received by group 2 was 218 μg of protein (16.4 μg AgE). In year 2 the mean total dose was 1829 jug (137.2 μg AgE). Sixty-six percent of injections elicited no reaction or a mild local reaction; the remaining injections produced local redness and swelling more than 2 inches in diameter. Four percent of injections produced systemic symptoms. PEG-modified ragweed stimulated increases in ragweed specific IgG antibody both years, but increases in ragweed specific IgE antibody were significant only in group 1 in year 1. The magnitude of the IgG antibody changes was directly related to the total dose injected. At the beginning of the second year, PEG-modified ragweed-treated subjects still had elevated IgG antibody levels. In the first year the subjects who had received 10 PEG-modified ragweed injections improved in symptoms and medications; however, in subjects who received only six injections there was no difference between active and placebo treatment. In year 2 the actively treated group had significantly less symptoms and needed less medication, and the improvement was significantly better than that observed during the first year. The results indicate that PEG-modified ragweed, administered in sufficient doses, is effective in reducing symptoms of ragweed-induced rhinoconjunctivitis and that the effect may be additive when it is administered over consecutive years.

Effect of seasonal ragweed exposure on immunoglobulin E antiragweed antibodies in cultures of peripheral mononuclear cells, plasma and nasal secretions.

To determine the effects of seasonal ragweed exposure on in vitro IgE antibody production, the antiragweed IgE antibody content of 7-day cultures of peripheral blood mononuclear cells was assessed in samples obtained before, during and after the ragweed season, in 4 ragweed-allergic and 11 nonallergic individuals. The levels of ragweed-specific IgE and total IgE in unstimulated culture supernatants were measured by solid phase radioimmunoassays. Antiragweed IgE antibody was apparently detectable in the 7-day culture supernatants of both allergic and nonallergic individuals, and the antibody concentrations increased after natural ragweed exposure. However, the bindable counts of IgE antibody in supernatants from allergic patients were inhibited by soluble ragweed antigen, while those from nonallergics were not inhibitable, suggesting that supernatants from nonallergics did not contain true ragweed-specific IgE antibody. Because, for most subjects, the quantity of IgE in culture supernatants from 7-day cultures of living cells was the same as that derived from cells which were either frozen and thawed prior to culture, or briefly exposed to pH 3.7 buffer, the majority of IgE antibody in supernatants from allergic subjects, and of total IgE in supernatants from all subjects, was apparently not newly synthesized, but was preformed, and appeared to be largely derived from the cell surface. IgE antiragweed antibody was detected in the nasal secretions and plasma of allergic, but not nonallergic individuals, and the levels of antibody in allergic subjects increased after seasonal exposure. The fraction of total IgE protein accounted for by IgE antiragweed antibody in nasal secretions collected postseasonally was higher than that in both culture supernatants and plasma, suggesting that ragweed-specific IgE antibody is synthesized locally in the nose.

Asthma and increases in nonallergic bronchial responsiveness from seasonal pollen exposure

Serial measurements of symptoms, peak flow rates, methacholine bronchial responsiveness, and ragweed-specific IgE antibodies were made before and during the ragweed pollen season in 13 sensitized subjects. Allergen inhalation tests were carried out with aerosols of pollen extract out of season in nine subjects; isolated early asthmatic responses were provoked in four, and dual responses (early followed by late) were provoked in five. During the pollen season all subjects developed hay fever and eight had symptoms of asthma. There was a real increase in methacholine responsiveness during the ragweed season. This increase appeared before or after the occurrence of asthma symptoms and changes in flow rates and was greater in subjects with symptoms in the pollen season, dual responses after allergen inhalation tests, and higher levels of ragweed-specific IgE antibodies. The results confirm the occurrence of seasonal asthma and increases in nonallergic (nonspecific) bronchial responsiveness to methacholine from seasonal pollen exposure. They suggest that the occurrence of symptoms is closely linked to the allergic inflammatory reaction and the induction of increased nonallergic responsiveness.

Comparison of the radioallergosorbent test and a quantitative solid-phase radioimmunoassay for the detection of ragweed-specific immunoglobulin E antibody in patients undergoing immunotherapy

Commercially available radioallergosorbent test (RAST) was compared with a quantitative solid-phase polystyrene tube radioimmunoassay (PTRIA) for the detection of ragweed-specific IgE antibody in sera of patients undergoing ragweed immunotherapy. Both assays showed good replication over a wide range of IgE antibody activity. The RAST was limited in the ability to discriminate between sera with high levels of specific IgE antibody. In addition, RAST gave falsely low values of IgE antibody activity in the presence of high levels of blocking antibody.

The effect of cromolyn sodium powder as a treatment for ragweed pollinosis

The effect of treating ragweed pollinosis with intranasal cromolyn sodium powder was evaluated in 26 patients in a double-blind clinical study. Thirteen matched patient pairs were treated by either nasal insufflation of cromolyn sodium powder, 20 mg three times daily, or by a placebo powder. Patients were monitored for severity of symptoms by means of daily symptom diaries collected weekly throughout the pollen season. Serum samples were obtained in July prior to the ragweed season and following the ragweed season during the first and fourth weeks of October for the determination of ragweed-specific IgE antibody levels by the radioallergosorbent test. A significant reduction in symptom severity was observed in the treated patients with high preseasonal levels of IgE antibody to ragweed. Initially the levels of IgE antibody to ragweed did not differ between the two groups. IgE antibody levels increased in both groups after pollen exposure, but the treated group showed a significantly greater rise in IgE antibody levels. The results suggest that treatment with cromolyn sodium enhanced IgE antibody response to pollen exposure and significantly reduced the severity of hay fever symptoms in patients with high preseasonal levels of IgE antibody to ragweed.

Maximal rise in IgE antibody following ragweed pollination season

Patients allergic to ragweed pollen who did not receive immunotherapy had an increase in ragweed-specific IgE antibodies associated with seasonal exposure. Of 17 such patients, 15 reached peak levels between mid-September and mid-October. Two had peak values after mid-October; the levels were only slightly higher than earlier values. Our study shows that serum obtained in mid-October reflects approximately the maximal IgE antibody level attained 0y ragweed-sensitive patients in our area and that this value can be used as a baseline in monitoring the subsequent decline in antibodies. In addition, our data support an earlier observation that the magnitude of seasonal rise in IgE antibody is related to the preseasonal value. The significantly positive correlation of the results of carefully performed skin tests (end point titration) with radioallergosorbent test (RAST) values suggests the possibility that the RAST can be employed as a reliable diagnostic aid, perhaps even replacing the skin test.