Role of insects as inhalant allergens in bronchial asthma with special reference to the clinical characteristics of patients

The Identification of Potential Immunogenic Antigens in Particular Active Developmental Stages of the Rice Weevil (Sitophilus oryzae)

BACKGROUND

The rice weevil (Sitophilus oryzae) originates from subtropical and tropical areas of Asia and Africa, but it also appears on other continents, mostly as a result of trade in rice. It may occur in grain fields as well as in storage facilities, and cause allergenic reactions. The aim of this study was to identify the potential antigens in all developmental stages of S. oryzae, which may cause an allergic response in humans.

METHODS

Sera of 30 patients were tested for the presence of IgE antibodies to antigens from three life stages of the rice weevil. To identify protein fractions containing potential allergens, proteins collected from larvae, pupae, and adults separated by sex of S. oryzae were fractionated by SDS-PAGE. Then, they were probed with anti-human, anti-IgE monoclonal antibodies, fractionated by SDS-PAGE and detected by Western blotting.

RESULTS

In total, 26 protein fractions of males and 22 fractions of other life stages of S. oryzae (larvae, pupae, and females) positively reacted with the examined sera.

CONCLUSIONS

The conducted study showed that S. oryzae may be a source of many antigens which may cause the potential allergic reactions in humans.

Respiratory sensitization to insect allergens: Species, components and clinical symptoms

Airborne insect particles have been identified as an important cause of respiratory allergies, including allergic asthma and rhinitis. In the literature, the significance of respiratory exposure to insect particles as a cause of occupational allergy has been well-documented. Indeed, many cases of occupational allergy have been reported including allergy to the larvae of flies and moths in anglers and occupationally exposed workers, to grain pests in bakers or other workers handling grains, and to crickets and/or locusts in researchers and workers in aquaculture companies. Furthermore, the prevalence of sensitization to insect allergens is considerably high among patients with asthma and/or rhinitis who are not occupationally exposed to insects, suggesting the clinical relevance of exposure to insects in indoor and outdoor environmental non-occupational settings. Exposure to cockroaches, a well-studied indoor insect, is associated with cockroach sensitization and the development and exacerbation of asthma. Booklice, another common indoor insect, were recently identified as a significant sensitizer of asthmatic patients in Japan and India, and potentially of asthma patients living in warm and humid climates around the world. Lip b 1 was identified as an allergenic protein contributing to the species-specific sensitization to booklice. Moths are considered a significant seasonal outdoor allergen and their allergens are considered to have the highest sensitization rate among Japanese patients. However, other than cockroaches, allergenic insect proteins contributing to sensitization have not been fully characterized to date.

A review on Respiratory allergy caused by insects

Hypersensitivity or allergy encompasses a wide range of immunological reactions that generally have adverse consequences involving one or many organ systems of the body. Allergens are usually glycoprotein or chemically complex low molecular weight substances. The common allergens include pollen, fungal spores, house dust mite and house dust, animal danders, drugs, foods, insect emanations, and detritus, etc. Information on the role of insects in respiratory allergy is increasing in the literature. There are about 30 million living species of insects. These insects can broadly be classified as stinging insects, biting insects and non-stinging and non-biting insects. All materials form insets namely wings, scales, saliva; dried feces and venom can cause allergic diseases, such as rhinitis, conjunctivitis, asthma and urticaria. There are wide varieties of insects such as moths, butterflies, bees, wasps, hornets, yellow jackets, flies, beetles, cockroaches, and mosquitoes. Exposure to emanations and detritus of these insects may lead to several allergies in some genetically predisposed individuals. Therefore, it is of interest to review allergies caused by various insect's stings and bites and their adverse effect on the human body.

Allergenicity and cross-reactivity of booklice (Liposcelis bostrichophila): a common household insect pest in Japan

BACKGROUND

Booklice (Liposcelis bostrichophila) are a common household insect pest distributed worldwide. Particularly in Japan, they infest 'tatami' mats and are the most frequently detected insect among all detectable insects, present at a frequency of about 90% in dust samples. Although it has been hypothesized that they are an important indoor allergen, studies on their allergenicity have been limited.

METHODS

To clarify the allergenicity of booklice and the cross-reactivity of this insect allergen with allergens of other insects, patients sensitized to booklice were identified from 185 Japanese adults with allergic asthma using skin tests and IgE-ELISA. IgE-inhibition analysis, immunoblotting and immunoblotting-inhibition analysis were performed using sera from these patients. Allergenic proteins contributing to specific sensitization to booklice were identified by two-dimensional electrophoresis and two-dimensional immunoblotting.

RESULTS

The booklouse-specific IgE antibody was detected in sera from 41 patients (22% of studied patients). IgE inhibition analysis revealed that IgE reactivity to the booklouse allergen in the sera from one third of booklouse-sensitized patients was not inhibited by preincubation with extracts from any other environmental insects in this study. Immunoblotting identified a 26-kD protein from booklouse extract as the allergenic protein contributing to specific sensitization to booklice. The amino acid sequence of peptide fragments of this protein showed no homology to those of previously described allergenic proteins, indicating that this protein is a new allergen.

CONCLUSIONS

Sensitization to booklice was relatively common and specific sensitization to this insect not related to insect panallergy was indicated in this population.

Clinico-immunologic study on immunotherapy with mixed and single insect allergens

BACKGROUND

Immunotherapy (IT) is practiced mainly with mixed and single allergen vaccines. But studies are rare with mixed allergen preparations.

OBJECTIVE

The objective of this study is to study mix and single insect allergen IT in patients of allergic rhinitis and asthma.

METHODS

We performed a double-blind placebo-controlled trial of mix and single allergen IT for 1 year in 99 patients of asthma or rhinitis or both. There were two groups, (1) active allergen IT (n = 61) with three subgroups single insect extract (cockroach, housefly, or mosquito) and mix allergen IT (two or three insect extracts) and (2) placebo (n = 38). Clinical (skin reactivity, airway reactivity, and symptom score) and immunological (IgE/IgG4 and IgG1/IgG4 ratio) parameters were assessed at baseline and after 1 year of IT.

RESULTS

Eighty-five patients completed 1 year of IT. The active allergen IT group patients showed a significant improvement compared to baseline values (p < 0.05) and placebo group patients (p < 0.05) with regard to symptom scores, FEV1 values, and immunological parameters (IgG4). No significant difference was found between mixed and single IT group patients for changes in clinical and immunological parameters. Positive correlation was observed between increase in IgG4 and clinical improvement. The changes in above parameters in placebo group were nonsignificant after 1 year of treatment.

CONCLUSION

IT with two to three mix extract from the same allergen group is effective for insect hypersensitivity.

Immunotherapy with mosquito (Culex quinquefasciatus) extract: a double-blind, placebo-controlled study

BACKGROUND

Mosquito allergy is well established, but mosquito immunotherapy requires validation using clinical and immunologic variables.

OBJECTIVE

To evaluate the tolerability and efficacy of specific immunotherapy with Culex quinquefasciatus (mosquito) extract.

METHODS

We performed a randomized, double-blind, placebo-controlled trial of immunotherapy for 1 year in 40 patients with asthma, rhinitis, or both. Patients were evaluated by means of intradermal testing, symptom and drug scores, and histamine provocation testing before and after 1 year of immunotherapy. Mosquito specific IgE and IgG subclass antibody responses were evaluated at the basal level and after 1 year.

RESULTS

Patients receiving allergen immunotherapy for 1 year showed a significant improvement compared with baseline and patients receiving placebo regarding skin reactions, symptom scores (rhinitis and asthma), and forced expiratory volume in 1 second. Provocation concentration of histamine that caused a decrease in forced expiratory volume in 1 second of 20% by inhalation was elevated in the group receiving immunotherapy. In the active group serologic analysis showed a slight reduction in IgE levels (P = .02) but a significant elevation in IgG4 levels (P = .001), with a significant decrease in the IgE/IgG4 ratio (P = .001). All these changes in the placebo group were nonsignificant.

CONCLUSIONS

Allergen immunotherapy with mosquito extract was well tolerated, with improvement in symptoms and airway reactivity. Good clinical outcome was associated with increased IgG4 antibody levels.

Reaction pattern to histamine and codeine in a human intradermal skin test model

BACKGROUND

Skin prick and intradermal skin tests (IDT) are useful tools in evaluating IgE-mediated allergic disorders. In the literature, many variations of the techniques used are described. No general agreement exists on test procedures and reading of test results.

OBJECTIVE

To analyse test conditions for IDT to facilitate comparability between different study protocols.

METHODS

We tested 24 healthy volunteers with three concentrations of histamine and codeine each on the upper back, lateral upper arm and volar forearm, with/without addition of ethylene diamine tetra-acetic acid. Reading of the resulting weal was performed by taking a digital image of the weal, later outlining the weal perimeter in triplicate and calculating the weal area using the NIH Image J software version 1.3.

RESULTS

Weal size was dose dependent for both substances, generally larger on the upper back than on the forearm and upper arm, and larger after codeine than after histamine. Addition of the Ca2+ -chelator ethylene diamine tetra-acetic acid did not significantly affect weal size. Weal size induced by histamine showed better consistency than that induced by codeine.

CONCLUSIONS

The results and our technique provide valuable tools for the daily routine as well as for the ability to compare information of intradermal tests from different studies or clinical reports. When assessing skin reactivity, we recommend the use of 1 mg/mL codeine as well as 0.1 mg/mL histamine to reflect aspects of mast-cell releasability and of vascular reactivity. The involvement of local factors influencing the vascular reactivity or differences in opiate receptor density on mast cells surfaces needs to be addressed in future studies.

[Occupational inhalant allergy to the common housefly (Musca domestica)]

Isolated allergy to the common housefly (Musca domestica) has only been described in four cases. Predisposing factors include high concentrations of allergens and prolonged exposure time. Two pharmaceutical industry workers, 59 and 34 years of age, both without atopy, presented with recent onset of allergic rhinitis. Their symptoms appeared about 30 minutes after exposure to Musca domestica in the closed breeding rooms. They were symptom-free with other insects, on weekends and on vacation. Skin prick tests with common inhalant allergens were negative. Prick testing with crushed Musca domestica adults, hatched eggs, contaminated nets and sand, as well as fly feces were all positive. One patient had specific IGE antibodies against Musca domestica. Both patients lacked specific IgE antibodies against other insect species and common aeroallergens. In these two patients there was a species-specific sensitization without relevant cross reactions to other arthropods. The patients were transferred to new work sites where they had no contact with Musca domestica and became symptom-free. Thus this common insect can be a relevant occupational aeroallergen.

Pharaoh ant (Monomorium pharaonis): newly identified important inhalant allergens in bronchial asthma

The nonstinging house ant, Monomorium pharaonis (pharaoh ant), was recently identified as a cause of respiratory allergy. This study was performed to evaluate the extent of sensitization to pharaoh ant, and its clinical significance in asthmatic patients. We carried out skin prick tests in 318 patients with asthma. Specific IgE (sIgE) to pharaoh ant was measured by ELISA, and cross-reactivity was evaluated by ELISA inhibition tests. Bronchial provocation testing was performed using pharaoh ant extracts. Fifty-eight (18.2%) of 318 patients showed positive skin responses to pharaoh ant, and 25 (7.9%) had an isolated response to pharaoh ant. Positive skin responses to pharaoh ant were significantly higher among patients with non-atopic asthma than among those with atopic asthma (26.0% vs. 14.9%, p<0.05). There was significant correlation between sIgE level and skin responses to pharaoh ant (rho=0.552, p<0.001). The ELISA inhibition tests indicated that pharaoh ant allergens had various pattern of cross-reactivity to house dust mites and cockroaches. Bronchial provocation tests to pharaoh ant were conducted for 9 patients, and eight showed typical asthmatic reactions. In conclusion, pharaoh ant is an important source of aeroallergens, and it should be included in the skin test battery for screening the causative allergens in patients with asthma.

Pets and cockroaches: two increasing causes of respiratory allergy in indoor environments. Characteristics of airways sensitization and prevention strategies

The increasing prevalence of allergic sensitization to indoor allergens such as dust mites, pets and cockroaches is the result of the changes in indoor environments induced by human activities. The Westernized lifestyle and the increasing time spent indoors determine a reduction in natural air ventilation and, consequently, higher levels of allergen concentrations and longer exposure to allergens. The major cat allergen Fel d 1 is carried by small-dimension particles (< 5 microm diameter) that readily become airborne and persist immodified for a long time. Fel d 1 must be considered a ubiquitous allergen because it has been found in indoor environments and even in public places where a cat has never been kept. Recent research has demonstrated that clothing of cat owners may contribute to the dispersal of Fel d 1 in cat-free environments. Therefore, washing Fel d 1-contaminated clothes should be considered a simple and effective method for removing this allergen from clothing and, consequently, reducing the risk of Fel d 1 dispersion. Cockroach allergens constitute another important cause of environment-related respiratory allergy and may trigger asthma exacerbations in sensitized individuals. In the prevention of cockroach allergy, the use of chemical agents associated with an intensive vacuum cleaning of indoor environments is an important tool in removing cockroach material containing allergenic proteins. Early recognition of allergy-predisposed babies, monitoring indoor allergens and adequate strategies of allergen avoidance are likely to be important means for reducing the prevalence of bronchial asthma.

Insect and arachnid hypersensitivity

Insect hypersensitivity reactions can have a large number of clinical presentations. The majority of reactions are pruritic and involve the short- or sparsely haired areas of the body. Most are associated with eosinophilic infiltration into the skin, often in a perivascular pattern. The diagnosis may be based on compatible clinical signs and improvement with aggressive insect control and, in some cases, confirmation via provocative exposure. Intradermal, prick, or serum testing for allergen-specific IgE can be used to document the presence of reaginic antibodies against insect allergens. Treatments include avoidance, aggressive insect control, and symptomatic support; in some cases, immunotherapy may be useful in decreasing the severity of clinical reactions to insects.

Role of animal danders as inhalant allergens in bronchial asthma in India

The etiological significance of animal danders in Indian patients with nasobronchial disorders has not yet been investigated. In the present study, the role of animal danders in the etiology of bronchial asthma was studied. Extracts of danders from 6 animals along with guinea pig whole pelt were prepared. Intradermal and bronchial provocation tests with these extracts were performed on (i) 68 asthmatics and (ii) 20 nonallergic healthy volunteers. In patients, significant positive skin reactions (2+ to 4+) ranged from 1.4% each with guinea pig whole pelt and ox dander to 8.8% with dog dander extracts. None of the healthy volunteers elicited such a response. On bronchial provocation, 20% and 53.8% of the tests were positive in asthmatics showing 1+ and 2+ skin reactivity, respectively. All the patients as well as controls eliciting negative intradermal responses demonstrated uniformly negative bronchial provocation tests to different dander extracts. Analysis of various clinical features of asthmatics with respect to skin positivity to dander/pelt extract was also carried out. Radioallergosorbent tests (RASTs) were performed to estimate dander-specific IgE levels in the sera of patients showing different grades of skin response to dander extracts of dog, horse, and goat. Sixty percent of sera from the patients showing 2+ to 4+ skin reactivity to various animal dander extracts showed positive RASTs. RAST positivity as well as RAST ratio increased with increase in the intensity of skin response. All the patients with positive cutaneous as well as positive bronchial responses also showed positive RASTs. Similarly, all the patients with positive skin and positive RASTs showed positive bronchoprovocation tests. These results suggested that animal danders play an important role in the etiology of bronchial asthma. Some of the clinical characteristics of asthmatics, such as (i) early age at onset of asthma, (ii) positive family history, and (iii) asthma with associated allergies, have significant bearing on the cutaneous response to various dander extracts.