Insect sting allergy with negative venom skin test responses

BACKGROUND

In our 1976 controlled venom immuno rapy trial, 33% of 182 patients with a history of systemic reactions to insect stings were excluded because of negative venom skin test responses. There have been reports of patients with negative skin test responses who have had severe reactions to subsequent stings.

OBJECTIVE

Our aim is to increase awareness about the patient with a negative skin test response and insect sting allergy and to determine the frequency and significance of negative skin test responses in patients with a history of systemic reactions to insect stings.

METHODS

We prospectively examined the prevalence of negative venom skin test responses in patients with a history of systemic reactions to stings. In patients who gave informed consent, we analyzed the outcome of retesting and sting challenge.

RESULTS

Of 307 patients with positive histories screened for our sting challenge study, 208 (68%) had positive venom skin test responses (up to 1 microg/mL concentration), and 99 (32%) had negative venom skin test responses. In 36 (36%) of the 99 patients with negative skin test responses, the venom RAST result was a low positive (1-3 ng/mL), or repeat venom skin test responses were positive; another 7 (7%) patients had high venom-specific IgE antibody levels (4-243 ng/mL). Notably, 56 (57%) of 99 patients with positive histories and negative skin test responses had negative RAST results. In patients with positive skin test responses, sting challenges were performed in 141 of 196 patients, with 30 systemic reactions. Sting challenges were performed on 37 of 43 patients with negative skin test responses and positive venom-specific IgE and in 14 of 56 patients with negative skin test responses and negative RAST results. There were 11 patients with negative skin test responses who had systemic reactions to the challenge sting: 2 had negative RAST results, and 9 had positive RAST results at 1 ng/mL. The frequency of systemic reaction was 21% in patients with positive skin test responses and 22% in patients with negative skin test responses (24% in those with positive RAST results and 14% in those with negative RAST results).

CONCLUSIONS

Venom skin test responses can be negative in patients who will subsequently experience another systemic sting reaction. Venom skin test responses are negative in many patients with a history of systemic allergic reactions to insect stings and may be associated with positive serologic test responses for venom-specific IgE antibodies (sometimes strongly positive results). Venom skin test responses should be repeated when negative, along with a serologic IgE antivenom test. Better diagnostic skin test reagents are urgently needed.

Effects of peptide therapy on ex vivo T-cell responses

BACKGROUND

Peptide therapy targets T cells directly with short peptides containing multiple T-cell receptor epitopes. Murine studies suggest T-cell anergy as the mechanism of action; however, changes in T-cell cytokine profiles may be more relevant in human beings.

OBJECTIVE

We sought to study the effects of peptide therapy on ex vivo antigen-specific T-cell responses.

METHODS

Antigen-specific T-cell lines were generated from subjects enrolled in a double-blind, placebo controlled, two-dose study of the ALLERVAX CAT therapeutic, containing Fel d 1 peptides (ImmuLogic Pharmaceutical Corp., Waltham, Mass.) (n = 7, 8, and 7, respectively, for groups receiving placebo, 75 microg, or 750 microg). Each subject had three lines propagated before and after receiving peptide therapy; antigens used were cat hair extract, Fel d 1 peptides, and tetanus toxoid (negative control). Proliferative responses and cytokine generation from each line were assessed after two restimulations with antigen and autologous antigen-presenting cells.

RESULTS

The Fel d 1 peptide lines showed a dose-dependent decrease of IL-4 production (p = 0.02 and 0.025, respectively, for the 750 microg group vs both the 75 microg and placebo groups). IL-4 production from the cat hair allergen extract lines and interferon-gamma production from both the Fel d 1 peptide lines and cat hair allergen extract lines showed no statistically significant changes. The control tetanus toxoid lines showed no changes in cytokine production; there were no significant changes in proliferation with any of the antigens in any of the treatment groups. In the clinical arm of the trial, only the 750 microg dose of peptides produced a significant response.

CONCLUSIONS

Peptide therapy induces a significant, dose-dependent decrease in peptide-stimulated IL-4 production, consistent with either a shift in T-cell phenotype or peptide-specific T-cell tolerance.

The efficacy of slow versus faster inhalation of cromolyn sodium in protecting against allergen challenge in patients with asthma

BACKGROUND

Approximately one third of patients with allergy-induced asthma who are treated with aerosolized cromolyn sodium (CS) fail to achieve a full therapeutic effect. This lack of effectiveness could involve nonhomogeneous distribution of drug in the lung as a result of high inspiratory flow rates.

OBJECTIVE

We sought to determine the efficacy of slow versus faster inhalation of CS in protecting against allergen challenge in patients with asthma.

METHODS

Eight patients with asthma underwent two allergen challenges 30 minutes after pretreatment with CS that was inhaled from a large holding chamber at approximately 30 L/min or approximately 70 L/min. Percent decreases in FEV1 at a common dose of allergen on the two challenge days were compared. Values of skew (an indicator of aerosol distribution homogeneity) obtained from gamma camera lung images after slow and faster inhalation of radiolabeled CS were also compared.

RESULTS

Mean (+/- SD) allergen-induced decrease in FEV1 was 5.4% +/- 4.2% after slow inspiration of CS, which was significantly less than the allergen-induced decrease in FEV1 after faster inhalation of CS with 12.6% +/- 11% (p < 0.05). Mean skew values were also significantly decreased after slow inspiration of CS, and differences in decreases in allergen FEV1 and skew values for the two breathing maneuvers were significantly correlated.

CONCLUSION

These data indicate that protection against allergen-induced asthma can be optimized by slowly inspiring CS from a large holding chamber compared with faster inhalation of the drug. These results appear to be related to enhanced distribution homogeneity of CS within the lungs.

A double-blind study of the discontinuation of ragweed immunotherapy

BACKGROUND

Immunotherapy effectively treats the symptoms of allergic rhinitis and improves its pathophysiology. We studied whether the effects of immunotherapy on the early response to nasal challenge with antigen and seasonal symptoms persist after discontinuation.

METHODS

Twenty subjects with ragweed allergy who were receiving immunotherapy and who had nasal challenges performed before initiation of treatment were selected. The patients had been receiving maintenance therapy with aqueous ragweed extract at a dose of 12 microg of Amb a 1 equivalent for a minimum of 3 years, at which point they were randomized to receive either placebo injections or to continue with the maintenance dose. Nasal challenges were performed before and 1 year after randomization. Nasal challenges were monitored by counting the number of sneezes and measuring histamine, N-alpha-tosyl-L-arginine methyl ester-esterase activity, and kinins in recovered nasal lavages. In the same year symptom diaries were collected during the ragweed season.

RESULTS

The initial immunotherapy significantly reduced responses to nasal challenge in both groups. The group continuing to receive active treatment showed no significant changes from the response before randomization. In contrast, the group randomized to placebo treatment showed a partial return of histamine, kinins, and N-alpha-tosyl-L-arginine methyl ester-esterase in nasal secretions and the numbers of sneezes. IgG antibodies to ragweed declined only in the group switched to placebo treatment. Seasonal rises of IgE antibodies to ragweed did not return during the first season after treatment was stopped. Symptoms reported during the ragweed season were not different between the groups.

CONCLUSIONS

One year after discontinuation of ragweed immunotherapy, nasal challenges showed partial recrudescence of mediator responses even though reports during the season appeared to indicate continued suppression of symptoms.

Clinical and immunologic effects of component peptides in Allervax Cat

Peptides have been designed to be T cell tolerogenic for the principal allergens of the cat. These have been administered in several dosage programs to cat-sensitive patients in multicenter blinded studies. In contrast to proteins in standard extracts, IgE sensitization to peptides is an uncommon event. Pretreatment prick tests with peptides will identify the occasional sensitized patient. Other side reactions consist of allergic symptoms occurring on the day of injections. These become less severe with subsequent injections and are easily treatable with antihistamines or bronchodilators, depending on the symptoms. Treatment with cat peptides ameliorated symptoms that occur upon exposure to cats 1-6 or more weeks later. A 2-week course of 4 injections is the most effective of the regimens so far tried. T-cell-active peptides offer a promising low-risk alternative for specific treatment of respiratory allergies.

Grass immunotherapy induces inhibition of allergen-specific human peripheral blood mononuclear cell proliferation

The peripheral blood mononuclear cells (PBMC) from humans allergic to grass pollens (GR+ subjects) show strong in vitro proliferative responses to purified allergens from Lolium perenne pollen Lol p 1, and to a lesser extent to Lol p 2 and Lol p 3. By contrast, PBMC from grass allergic patients undergoing immunotherapy (GR + IT subjects) exhibit a very poor Lol p-specific proliferative response, similar to that observed in nongrass allergic subjects (GR-subjects). Unlike GR-subjects, both GR+ and GR + IT subjects have high levels of antigen-specific serum IgG and IgE antibodies to Lol p 1, Lol p 2 and Lol p 3. While GR+ subjects exhibit a significant correlation between antigen-specific serum antibody and PBMC responses, GR + IT subjects do not show a correlation between the two responses. The possible mechanisms by which immunotherapy may modulate allergen-specific T cell proliferative response are discussed.

Treatment of cat allergy with T-cell reactive peptides

We induced in allergic humans the counterpart of murine experimental T-cell tolerance. T-cell lines from cat-allergic humans were used to map T-cell epitopes for the principal allergen of cat dander, Fel d 1. Two peptides of 27 amino acids each were synthesized to contain the dominant epitopes (ALLERVAX CAT). After a safety trial, we carried out a blinded study of the dose required for efficacy. We randomly divided 95 cat-sensitive patients into placebo, 7.5 micrograms, 75 micrograms, and 750 micrograms groups. Patients received a subcutaneous injection weekly for 4 wk. Before and after treatment, patients were exposed in a room inhabited by live cats and scored by nose and lung symptoms. Baseline nasal and lung scores (+/-SEM) were 6.2 +/- 0.56 and 5.4 +/- 0.73 in the 750 micrograms group; 7.8 +/- 0.53 and 4.7 +/- 0.68 in the placebo group. Six weeks after treatment, scores adjusted for baseline differences were reduced in the 750 micrograms group: -2.3 +/- 4.9 and -2.3 +/- 0.59 compared with -0.84 +/- 0.50 and -0.85 +/- 0.62 in the placebo group. The 75 micrograms group showed intermediate effects and the 7.5 micrograms group no effect. Linear trend analysis indicated a significant dose response effect: p = 0.05 for nose and 0.03 for lung symptoms. Allergic side effects occurred an hour or more after the first 750 micrograms dose in 16 of 24 patients but required little or no treatment with one exception. T-cell reactive treatment peptides safely improved allergic responses to cats.

Ragweed immunotherapy in adult asthma

BACKGROUND

Although allergen immunotherapy is effective for allergic rhinitis, its role in treating asthma is unclear.

METHODS

We examined the efficacy of immunotherapy for asthma exacerbated by seasonal ragweed exposure. During an observation phase, adults with asthma who were sensitive to ragweed kept daily diaries and recorded peak expiratory flow rates between July and October. Those who reported seasonal asthma symptoms and medication use as well as decreased peak expiratory flow were randomly assigned to receive placebo or ragweed-extract immunotherapy in doses that increased weekly for an additional two years.

RESULTS

During the observation phase, the mean (+/- SE) peak expiratory flow rate measured in the morning during the three weeks representing the height of the pollination season was 454 +/- 20 liters per minute in the immunotherapy group and 444 +/- 16 liters per minute in the placebo group. Of the 77 patients who began the treatment phase, 64 completed one year of the study treatment and 53 completed two years. During the two treatment years, the mean peak expiratory flow rate was higher in the immunotherapy group (489 +/- 16 liters per minute, vs. 453 +/- 17 in the placebo group [P = 0.06] during the first year, and 480 +/- 12 liters per minute, vs. 461 +/- 13 in the placebo group [P = 0.03] during the second). Medication use was higher in the immunotherapy group than in the placebo group during observation and lower during the first treatment year (P = 0.01) but did not differ in the two groups during the second year (P = 0.7). Asthma-symptom scores were similar in the two groups (P = 0.08 in year 1 and P = 0.3 in year 2). The immunotherapy group had reduced hay-fever symptoms, skin-test sensitivity to ragweed, and sensitivity to bronchial challenges and increased IgG antibodies to ragweed as compared with the placebo group; there was no longer a seasonal increase in IgE antibodies to ragweed allergen in the immunotherapy group after two years of treatment. Reduced medication costs were counterbalanced by the costs of immunotherapy.

CONCLUSIONS

Although immunotherapy for adults with asthma exacerbated by seasonal ragweed exposure had positive effects on objective measures of asthma and allergy, the clinical effects were limited and many were not sustained for two years.

Modern concepts of immunotherapy

Although common allergies have been considered as immediate IgE antibody mediated responses, attention is now turning to inflammatory responses that appear to be initiated by T-cell responses to peptides from allergens presented in combination with HLA class II molecules. Although classic immunotherapy with allergen extracts has been found to downregulate these T-cell responses, more efficient and safe methods are being sought.

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

We performed two seasonal studies to evaluate the effect of continuous treatment with intranasal steroids, beginning approximately 1 week before the appearance 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 micrograms 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 micrograms 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.

Therapeutic potential of peptides in allergic disease

Immunotherapy with crude allergens prevents allergic symptoms in many patients, but its effects are temporary and variable. This type of intervention provokes a transient increase in IgE antibody synthesis that may produce untoward side effects. Recent research has suggested that such immunotherapy downregulates T-cell activity, indicating that regulation of proinflammatory T cells may be a critical mechanism of the therapeutic response. Animal studies have shown that T cells can be rendered anergic by the administration of nonimmunogenic, T-cell-active peptides. Peptides prepared by urea denaturation of purified allergens and by pepsin digestion of crude allergens have been evaluated in humans. Although evidence of specific immunosuppression was noted, allergic reactions occurred as well. Subsequently, researchers synthesized peptides representing short sequences from the protein chains of principal allergens, such as Amb a I of ragweed and Fel d I of cat. Assays of proliferation of T-cell lines from ragweed- and cat-sensitive patients have shown that relatively short sequences from these proteins are responsible for a major portion of the activity of the whole protein. One such cat peptide has shown no reactivity with human IgE. The characteristics of these peptides suggest they should be evaluated further in clinical trials of allergic patients. The anticipated outcome would be prolonged T-cell downregulation, which might result in suppression of late-phase allergic inflammation and IgE antibody synthesis. The question whether such changes will reduce clinical reactivity sufficiently to be clinically useful remains to be answered in future studies.

Cutaneous late-phase response in food-allergic children and adolescents with atopic dermatitis

Food hypersensitivities contribute to disease exacerbation in a sub-group of children with atopic dermatitis (AD). It has been shown that only selected foods are capable of causing clinical reactions when ingested, whereas other foods, to which the patient is equally sensitive by skin-prick testing, may be tolerated. The purpose of this study was to examine the cutaneous late-phase response (LPR) to food antigens in food-allergic patients with AD and to determine if the skin reacted differently to 'relevant foods' (foods eliciting positive skin-prick tests and positive oral challenges) than to 'non-relevant foods' (foods eliciting positive skin tests but negative oral challenges). Using blister chambers adfixed to the skin, six children with AD were challenged epicutaneously with foods to which they had previously been shown to be sensitive. Histamine and PGD2 were measured hourly for 10-12 hr in parallel with quantitation of the cellular traffic. There appeared to be no difference in any of the measured parameters between relevant foods and non-relevant foods, and the patterns of the LPR cells and mediators were similar to those previously described with aero-allergens in patients with respiratory allergy. Histamine rose to 13.0 +/- 24 ng/ml (P < 0.005) during the first hours, declined to < 1 ng/ml by the fifth hour, and then rose a second time to 6.72 +/- 3.4 ng/ml (P < 0.05) during the 12th hour. PGD2 rose to an average of 312 pg/ml (P < 0.05) during the first 3 hr followed by a decline to baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Budesonide in grass pollen rhinitis

To determine the relative efficacy, to compare the incidence of adverse experiences, and to assess the systemic glucocorticoid effect of nasal preparations of budesonide, 200 micrograms bid, and placebo, 50 adult patients with seasonal allergic rhinitis due to grass pollen were studied in a stratified, double-blind parallel group design. After a 2-week baseline period, budesonide nasal spray, 100 microgram per nostril twice a day, was compared with placebo nasal spray over a 4-week treatment period. Supplementary treatment with chlorpheniramine, 4-mg tablets, was permitted when necessary to control symptoms. Daily symptom and medication diaries were kept by the patients. Investigator assessments of symptoms and side effects were made at clinic visits at 2-week intervals. At baseline and again towards the end of the study, blood samples were drawn for the determination of plasma cortisol levels and 24-hour urine samples collected for the measurement of 17-hydroxycorticosteroid output. Of the 24 men and 26 women entering, 49 completed the study. Symptom scores for sneezing, stuffy nose, and nasal secretion all decreased dramatically from baseline when budesonide treatment was started. The decrease in symptoms was greater for budesonide than for placebo (P < .001). There was no difference between budesonide and placebo with regard to eye itch and rescue medication used. Morning nasal washes were taken during the grass season before treatment was started and 16 to 17 days after. They showed a significant decrease in TAME esterase levels in secretions in the budesonide treated patients (P = .03) but not in the placebo-treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of H1 receptor blockade on the early and late response to cutaneous allergen challenge

We investigated whether cutaneous antigen-induced inflammatory cell infiltration and mediator release were modified by H1 receptor antagonists. Three chemically unrelated antihistamines (cetirizine, promethazine and chlorpheniramine) were tested in three groups of allergic subjects in a double-blind, crossover design. Chamber fluids were collected for 12 hr and histamine release, prostaglandin D2 production and cellular infiltration were quantified. Cetirizine significantly decreased late leukocyte migration into antigen-challenged chambers: eosinophils by 68% (P less than .04), basophils by 64% (P less than .04) and neutrophils by 72% (P less than .04), whereas mononuclear cells were not significantly affected. No alteration in the numbers of peripheral blood leukocytes or eosinophils occurred while on cetirizine treatment, suggesting that the decrease in inflammatory cells during the late phase reaction in the skin is not secondary to alterations in the peripheral leukocyte pool. In contrast, neither promethazine nor chlorpheniramine induced any significant alteration in inflammatory cell infiltration. All three antihistamines caused significant inhibition of the immediate reaction to antigen without any significant alteration in late phase reaction cutaneous reactivity. None of the three antihistamines caused any significant alteration in histamine or prostaglandin D2 levels. Thus, cetirizine may be an antihistamine uniquely capable of downregulating the late phase reaction inflammatory cell milieu without altering either early or late mediator production. The mechanisms involved and the clinical relevance of these findings remain to be explored.

The nasal response to histamine challenge: effect of the pollen season and immunotherapy

To evaluate changes in the nasal response to histamine, we challenged 19 subjects with allergic rhinitis caused by ragweed (RW) before, during, and after the RW season with increasing doses of histamine diphosphate. We compared their response, as measured by symptoms and the levels of TAME-esterase activity and albumin recovered in the nasal lavage fluid, with response of two groups with allergic rhinitis undergoing immunotherapy with moderate-dose (N = 16) and high-dose (N = 11) RW (2 and 24 micrograms of antigen E [Amb a I] as maintenance dose, respectively). Four challenges with histamine were performed in each group: before, at the peak of, near the end of, and 2 weeks after the RW season. The three groups of subjects had similar skin sensitivity to antigen and levels of TAME-esterase activity and albumin recovered from nasal lavages after histamine challenge performed before seasonal exposure. Symptom diaries obtained throughout the season revealed a significant reduction only in the high-dose immunotherapy-treated group. At the peak of the season, the untreated group had more symptoms in response to the challenge compared with the challenges before and after the season (p = 0.04 for both groups). The saline challenge occurring before challenging with histamine also demonstrated a significant increase at the peak of the season compared with increases before the season (p = 0.02). This observation was also true for the levels of albumin and TAME-esterase activity. If the response after saline challenge was subtracted from each response after histamine challenge, no difference was found in the results between any of the visits.(ABSTRACT TRUNCATED AT 250 WORDS)