V. Pravettoni

Lipid transfer proteins and 2S albumins as allergens

Plant lipid transfer proteins, a widespread family of proteins, have been recently identified as important food allergens. Their common structural features, such as eight conserved cysteines forming disulfide bridges, basic isoelectric point and high similarity in amino acid sequence, are the basis of allergic clinical cross‐reactivity. This has been demonstrated for the LTP allergens of the Prunoideae subfamily, whose similarity is about 95% as demonstrated for the purified allergens of peach, apricot, plum and apple. A relevant aspect is the existence of sequence homology of LTPs of botanically unrelated foods, as demonstrated for LTPs of maize and peach. A class of food allergens of well recognized clinical importance is that of seed storage 2S albumins. They have been identified in the most diffused edible seeds and nuts, such as mustard, sesame, Brazil nut, walnut and peanut. In particular, a strong correlation between IgE‐binding to these proteins and food‐induced anaphylaxis has been demonstrated for Brazil nut and sesame seeds.

Role of the elimination diet in adults with food allergy

The aim of the study was to check whether, after a period of complete exclusion of the offending foods in adult subjects suffering from food allergy, these foods could subsequently be safely reintroduced into the diet. Patients with chronic urticaria and/or perennial rhinitis negative for secondary pathology or other allergies were subjected to a strict diagnostic protocol for food allergy. Briefly, out of a case list of 207 patients, we found 23 patients whose symptoms were clearly related, on open reintroduction, to at least one food. The really offending foods in these patients were subsequently identified by double-blind, placebo-controlled food challenges. Only 10 of the 23 patients had positive challenges for 13 foods. Double-blind challenges were repeated after 1 year or more of avoidance of the offending foods to evaluate the persistence or disappearance of sensitivity. We found that five (38%) of the 13 previously offending foods were well tolerated. Thus, in adults, as previously proved in children, dietary avoidance of the offending foods appears to be an effective measure for dealing with food allergy. The kind of foods involved and the completeness of their avoidance appeared to be important factors favoring the reestablishment of tolerance in adults.

Lipid-transfer protein is the major maize allergen maintaining IgE-binding activity after cooking at 100°C, as demonstrated in anaphylactic patients and patients with positive double-blind, placebo-controlled food challenge results

BACKGROUNDnIn a previous study a 9-kd lipid-transfer protein (LTP) was identified as the major allergen of raw maize in a population of 22 anaphylactic patients. However, the stability of this protein in cooked maize is unknown.nnnOBJECTIVEnWe investigated the allergenicity of 5 maize hybrids and its modification after different thermal treatments by using sera from anaphylactic patients and patients with positive double-blind, placebo-controlled food challenges.nnnMETHODSnFive maize hybrids were extracted by using different methods, obtaining the water-soluble, zein, total zein, glutelin, and total protein fractions. The IgE-binding capacity of the different extracts, both raw and after thermal treatment, was investigated by means of SDS-PAGE immunoblotting. A 9-kd heat-stable allergen was purified by means of HPLC and sequenced. Changes in its secondary structure during and after heating from 25 degrees C to 100 degrees C were monitored by means of circular dichroism.nnnRESULTSnAll raw maize hybrids showed similar protein and IgE-binding profiles. The SDS-PAGE of all the heat-treated hybrids demonstrated a decreased number of stained bands in respect to the raw samples. The IgE immunoblotting demonstrated that the major allergen of the water-soluble, total zein, total protein, and glutelin fractions was a 9-kd protein identified by means of amino acid sequence as an LTP and a sub-tilisin-chymotrypsin inhibitor (in total zein fraction). The IgE-binding capacity of this 9-kd protein remained unchanged after thermal treatments, even though circular dichroism demonstrated an altered secondary structure.nnnCONCLUSIONSnMaize LTP maintains its IgE-binding capacity after heat treatment, thus being the most eligible candidate for a causative role in severe anaphylactic reactions to both raw and cooked maize.

Atopy and intolerance of antimicrobial drugs increase the risk of reactions to acetaminophen and nimesulide in patients allergic to nonsteroidal anti‐inflammatory drugs

This study evaluated the risk factors for developing allergic reactions to alternative drugs such as acetaminophen and nimesulide in 367 patients intolerant of nonsteroidal anti‐inflammatory drugs (NSAID) compared to 243 healthy controls. All subjects were given test doses (TD) of acetaminophen and nimesulide, and age, sex, atopy, and history of reactions also to unrelated drugs were compared in those who reacted and those who were tolerant of the challenge. TD was positive in 49 of 367 (t4%) NSAID‐allergic patients and in one (0.4%) ofthe controls (f <0.001). No difference was found in age and sex between the TD‐positive and TD‐negative subjects, although a significantly larger number of females were NSAID allergic (P<0.01). Of the 367 patients, 208 had a historj of reactions only to NSAID, and 148 to NSAID and antimicrobial drugs (AMD). TD with acetaminophen or nimesulide was positive in 6% of patients intolerant only of NSAID and i n 24% of those intolerant of both NSAID and AMD, with an odds ratio of 4.82. Atopy was more frequent among patients (36%) than controls (23%) (P=0.004). among TD‐positive (51%) than TD‐negative patients (33.5%) (P<0.02), and among patients intolerant of NSAID and AMD (48%) than those intolerant only of NSAID (F=0.006). The odds ratios were, respectively, 1.87, 2.57, and 3.16. This study provides evidence that atopy and history of allergic reactions to AMD increase the likelihood of intolerance of usually well‐tolerated alternative drugs such as acetaminophen and nimesulide in subjects allergic to NSAID.

Clinical and immunological effects of immunotherapy with alum‐absorbed grass allergoid in grass‐pollen‐induced hay fever

A double‐blind, placebo‐controlled study of immunotherapy was conducted in 19 patients with grass‐pollen hay fever to evaluate the efficacy and safety of a formalinized depot grass allergoid. The patients were assessed before and during IT by clinical (symptom‐medication scores during the grass‐ pollen season, specific nasal and skin reactivity) and immunological (specific IgE, IgG, IgG1 and IgG4 antibodies) parameters. High doses of grass allergoid, corresponding to a cumulative pre‐seasonal dosage of 46050 PNU, were administered, with only one systemic reaction. The actively treated patients had significantly lower symptom‐medication scores than placebo (p < 0.01) during the month of May and showed a significant decrease in specific skin (p < 0.01) and nasal (p < 0.05) reactivity, and a significant early increase in specific IgE (p < 0.01), IgG (p < 0.0005), IgG1 (p < 0.001) and IgG4 (p < 0.05), with a subsequent decrease of IgE and IgG1. No differences were detected in any of these parameters in the placebo group. A correlation was found between high IgG4/IgG1 ratio and the specific skin reactivity decrease (r = 0.691, p < 0.05), whereas a high IgG4/IgG1, ratio was associated with higher symptom‐medication scores (r = 0.654, p < 0.05). Possible explanations of these apparent discrepancies are proposed.

A double‐blind, placebo‐controlled study of immunotherapy with an alginate‐conjugated extract of Parietaria Judaica in patients with Parietaria hay fever

A double‐blind, placebo‐controlled study was conducted to evaluate the efficacy and safety of immunotherapy (IT) with a partially purified alginate‐conjugated extract of Parietaria judaica (Conjuvac®Parietaria, Dome/Hollister‐Stier) in patients suffering from rhinoconjunctivitis caused by Parietaria pollen. Eighteen patients (10 women, 8 men, mean age 35 years) received active treatment and 17 (10 women, 7 men, mean age 42.5 years) received placebo. Actively treated patients had significantly lower nasal symptom/medication scores (running nose P= 0.0087 and sneezing P= 0.048) during the Parietaria pollen season. Significant decreases in specific skin (P > 0.01), nasal (P > 0.05), and conjunctival (P > 0.01) reactivity to the Parietaria extract and significant increases of specific IgG (P > 0.001), IgGI (P > 0.001), and IgG4 (P > 0.001) in actively treated patients, but not in placebo, were found. IT was well tolerated, the active extract inducing five mild systemic reactions (four rhinitis and one urticaria) and placebo two (rhinitis). A significant correlation was found between low skin reactivity and high specific IgG (P= 0.0002) and IgG4 (P= 0.036). These findings indicate that IT with a partially purified P. judaica extract is an effective and safe treatment for Parietaria pollen allergy. The correlation between low immediate skin reactivity and high specific IgG and IgG4 suggests that, at least in the studied cutaneous model, these antibodies may exert a blocking effect.

New allergens in fruits and vegetables

regards the charac- terization of allergens, advances in allergology have served so far to introduce allergenic extracts capable of improving diagnostic and therapeutic performances rather than leading to a deep know- ledge of the etiopathogenesis of allergy. Currently, the concept that there are no peculiar properties making an antigen an efficient allergen is disputed, since recent data suggest that some allergens can directly induce an IgE response. This seems to be true of phospholipase

Clinical evaluation of CAP System and RAST in the measurement of specific IgE

We investigated the diagnostic value of a new in vitro test, Pharmacia CAP System (Pharmacia Diagnostics AB, Uppsala, Sweden), for the quantitative measurement of allergen‐specific IgE antibodies by comparison with RAST in 2 groups of patients, 71 atopic and 48 non‐atopic. In the last 20 years RAST has supplied a good diagnostic tool, but this test presents some problems, the main one being sensitivity. The new test has a solid phase able to bind even very small amounts of specific IgE and an anti‐IgE tracer with very low cross‐reactivity with other immunoglobulins, thus presenting more favourable conditions. From the analysis of our results, Pharmaeia CAP System gave higher sensitivity (94% compared to 88% of RAST) with no loss of specificity (96% for both tests). The reliability of these results is ensured by the proper selection of patients who were all suffering from pollinosis and were clinically diagnosed as certainly hypersensitive to a single pollen. A positive trend was found between severity of asthma and levels of specific IgE for timothy. Pharmacia CAP System appears to identify a larger number of atopic patients than RAST.

EAACI Guidelines on Allergen Immunotherapy: Hymenoptera venom allergy

Hymenoptera venom allergy is a potentially life‐threatening allergic reaction following a honeybee, vespid, or ant sting. Systemic‐allergic sting reactions have been reported in up to 7.5% of adults and up to 3.4% of children. They can be mild and restricted to the skin or moderate to severe with a risk of life‐threatening anaphylaxis. Patients should carry an emergency kit containing an adrenaline autoinjector, H1‐antihistamines, and corticosteroids depending on the severity of their previous sting reaction(s). The only treatment to prevent further systemic sting reactions is venom immunotherapy. This guideline has been prepared by the European Academy of Allergy and Clinical Immunologys (EAACI) Taskforce on Venom Immunotherapy as part of the EAACI Guidelines on Allergen Immunotherapy initiative. The guideline aims to provide evidence‐based recommendations for the use of venom immunotherapy, has been informed by a formal systematic review and meta‐analysis and produced using the Appraisal of Guidelines for Research and Evaluation (AGREE II) approach. The process included representation from a range of stakeholders. Venom immunotherapy is indicated in venom‐allergic children and adults to prevent further moderate‐to‐severe systemic sting reactions. Venom immunotherapy is also recommended in adults with only generalized skin reactions as it results in significant improvements in quality of life compared to carrying an adrenaline autoinjector. This guideline aims to give practical advice on performing venom immunotherapy. Key sections cover general considerations before initiating venom immunotherapy, evidence‐based clinical recommendations, risk factors for adverse events and for relapse of systemic sting reaction, and a summary of gaps in the evidence.

Maize food allergy: a double‐blind placebo‐controlled study

Background Maize allergy is not very common especially in Europe. The number of studies that address IgE mediated maize allergy is all too few.