Latex antigens: identification and use in clinical and experimental studies, including crossreactivity with food and pollen allergens

Detection of Islet Cell Immune Reactivity with Low Glycemic Index Foods: Is This a Concern for Type 1 Diabetes?

Dietary management of autoimmune diabetes includes low glycemic foods classified from the glycemic index, but it does not consider the role that immunoreactive foods may play with the immunological etiology of the disease. We measured the reactivity of either monoclonal or polyclonal affinity-purified antibodies to insulin, insulin receptor alpha, insulin receptor beta, zinc transporter 8 (ZnT8), tyrosine phosphatase-based islet antigen 2 (IA2), and glutamic acid decarboxylase (GAD) 65 and 67 against 204 dietary proteins that are commonly consumed. Dietary protein determinants included unmodified (raw) and modified (cooked and roasted) foods, herbs, spices, food gums, brewed beverages, and additives. There was no immune reactivity between insulin or insulin receptor beta and dietary proteins. However, we identified strong to moderate immunological reactivity with antibodies against insulin receptor alpha, ZnT8, IA2, GAD-65, and GAD-67 with several dietary proteins. We also identified 49 dietary proteins found in foods classified as low glycemic foods with immune reactivity to autoimmune target sites. Laboratory analysis of immunological cross-reactivity between pancreas target sites and dietary proteins is the initial step necessary in determining whether dietary proteins may play a potential immunoreactive role in autoimmune diabetes.

Food-induced immunoglobulin E-mediated allergic rhinitis

Food allergies are estimated about 1–2% in adults and 8% in children younger than 6 years. Allergic rhinitis is a common disease with a prevalence of 40% among different societies. Although, some foods play a role on exacerbation of allergic rhinitis symptoms, but still there are controversies about the role of diet on incidence or worsening the symptoms. The ongoing research demonstrates a possible relationship between certain foods and their induction of allergic reactions by modulating immunoglobulin E. A total of 100 patients (including both children and adults), between the ages 10 to 60 years, diagnosed with allergic rhinitis were selected for the study. Pregnant females and treated patients with antihistamine were excluded from the study. In vitro serum immunoglobulin E (IgE) levels mediated by a combination of food and inhalant allergens were detected by RIDA^® Allergy Screen in blood samples. Data were presented as mean, standard deviation and standard error. A statistical analysis was performed by one-way analysis of variance (ANOVA). A p value < 0.05 was considered statistically significant. We reported that 63% of patients with allergic rhinitis were sensitized to common food allergens whereas the rest 37% of patients were not sensitive to any of the food allergens. Similarly, a correlation between the age groups of patients with allergic rhinitis and food allergy were also accomplished. We found the highest response rate for allergic rhinitis and food allergy (53.2%) for the people between aged between 21 years and 40 years. We also demonstrated that females are more prone to mediate allergic rhinitis as induced by food allergies as compare to males (i.e., 66.2% vs. 33.3%). Food allergy is estimated to be 4.5% in adolescents and adults with asthma, rhinitis or both. Rice, citrus fruits, black grams and banana are identified as major allergens for inducing allergic-rhinitis symptoms.

Latex immunotherapy: state of the art

OBJECTIVE

Latex allergy remains a significant problem, especially among certain professional categories, and specific immunotherapy has been suggested as a suitable therapeutic option. The objective of the this article is to review the available literature on clinical trials of specific immunotherapy in latex allergy.

DATA SOURCES

Literature databases (PubMed, Embase, Google Scholar) were searched for latex immunotherapy clinical trials.

STUDY SELECTIONS

Clinical trials (either open or randomized controlled) using subcutaneous or sublingual immunotherapy with latex extracts were selected. Only articles published in English in peer-reviewed journals were considered. Case reports quoted in the clinical trials were also described, when pertinent.

RESULTS

Eleven clinical trials (3 with subcutaneous and 8 with sublingual immunotherapy) were identified. Two of the 3 randomized trials of subcutaneous immunotherapy reported some benefit in adults but a remarkable occurrence of side effects. Concerning sublingual immunotherapy (SLIT), there were 6 randomized placebo-controlled (1 in children), 1 randomized open, and 1 open trials. All but 1 trial reported positive results, and the safety profile was overall superior to injection immunotherapy. The overall quality of the study was moderate, and the number of subjects studied was low.

CONCLUSION

Although guidelines do not consider allergy to latex as an accepted indication to desensitization, SLIT can be offered, in addition to symptomatic treatment, to selected patients, when avoidance measures are not feasible or effective.

A 71-year-old man with anaphylaxis after eating grits

The allergist is frequently called on to evaluate patients after episodes of anaphylaxis to determine the cause and implement preventive measures that will reduce the patient's risk from future episodes. The etiology of anaphylaxis can be the result of numerous causes that may go undiagnosed if a thorough evaluation is not performed. We present a 71-year-old man with no history of food allergy or atopy who presented to the emergency room and then our allergy clinic for evaluation after suffering anaphylaxis after a meal of grits and shrimp. The underlying diagnosis, which was subsequently determined, requires a high index of suspicion and should be included in the differential diagnosis of any patient presenting with unexplained anaphylaxis.

Isolation and characterization of the potential receptor for wheat germ agglutinin from human neutrophils

Neutrophils participate in host protection and central to this process is the regulation of oxidative mechanisms. We purified by affinity chromatography the receptor for the GlcNAc-specific WGA from CD14+ CD16+ cell lysates (WGAr). The receptor is a 141 kDa glycoprotein constituted by two subunits of 78 and 63 kDa. It is mainly composed of Ser, Asx, and Gly, and, in a minor proportion, His, Cys, and Pro. Its glycan portion contains GlcNAc, Gal, and Man; NeuAc and GalNAc were identified in a minor proportion. The amino acid sequence of the WGA receptor was predicted from tryptic peptides by MALDI-TOF, both subunits showed homology with cytokeratin type II (26 and 29% for the 78 and 63 kDa subunits, respectively); the 78 kDa subunit showed also homology with the human transferrin receptor (24%). Antibodies against WGAr induce higher oxidative burst than WGA, determined by NBT reduction; however, this effect was inhibited (p < 0.05) with GlcNAc suggesting that WGAr participates as mediator in signal transduction in neutrophils.

Specific immunotherapy with standardized latex extract versus placebo in latex-allergic patients

BACKGROUND

Allergy to natural rubber latex proteins continues to be an important medical problem among health care professionals, but also in multioperated children. Clinical manifestations range from urticaria to angioedema, rhinoconjunctivitis, bronchial asthma and anaphylactic shock.

METHODS

The aim of this study was to investigate the efficacy and safety of a 12-month latex-specific immunotherapy in sensitized patients, most often health care workers. Twenty-three patients with latex rhinoconjunctivitis (20 of whom also had asthma) were included in this randomized, double-blind, placebo-controlled trial (11 in the active group, 12 in the placebo group). Treatment efficacy was assessed by means of symptom and medication scores. Conjunctival provocation tests and quantitative skin prick tests were also performed.

RESULTS

The clinical index (derived by combining changes from baseline of six efficacy variables during the treatment period) did not differ significantly between treatment groups. Change from baseline of rhinitis, conjunctivitis, skin symptoms, asthma symptoms, medication score and cutaneous reactivity were not significantly different between the two groups. A nonsignificant difference in conjunctival reactivity was observed in favor of the active group (p = 0.09). Systemic reactions were much higher in the specific immunotherapy than in the placebo group.

CONCLUSIONS

The present study failed to show a significant improvement of symptoms and medication scores, probably because of the low level of symptoms at baseline and the low maintenance dose of therapy, even if allergen-specific conjunctival reactivity decreased in the active group. Moreover, the incidence of systemic reactions was very high in the active group.

Kiwi fruit allergy: a review

Allergy to kiwi fruit was first described in 1981, and there have since been reports of the allergy presenting with a wide range of symptoms from localized oral allergy syndrome (OAS) to life-threatening anaphylaxis. The article reviews the available information concerning the clinical features of kiwi fruit allergy and the role of clinical investigations for diagnosis. Work identifying the major allergens in kiwi fruit has resulted in conflicting results, the possible reasons for which are discussed. The clinical associations of kiwi fruit allergy with allergies to pollens or latex are reviewed.

Comparison of ammoniated and nonammoniated extracts in children with latex allergy

BACKGROUND

The use of ammoniated or nonammoniated latex extracts for the diagnosis of latex allergy is still a matter of debate. The aim of our study was to compare the characteristics of the two types of extracts by immunoblotting and RAST techniques in children with ascertained latex allergy.

METHODS

Ammoniated (AL) and nonammoniated latex (NAL) extracts were prepared and blotted on SDS-PAGE to resolve their components. Also a solid phase for RAST assays was prepared with the two extracts. The sera from 18 children (mean age 11.4 years, range 6-15 years), with ascertained latex allergy (clinical history, skin test, CAP-RAST and provocation) were used for the experiments.

RESULTS

The NAL extract is resolved in many bands (5-100 kDa), whereas AL showed only few components, likely Hev b 4, 6 and 7. IgE reactivity against AL was observed only in 5/18 patients, whereas 12/18 were positive with NAL. The blotting profile against NAL was complex and the IgE recognition pattern involved different bands.

CONCLUSION

The extract obtained from NAL is able to detect specific IgE against a greater number of allergenic determinants, and therefore a greater diagnostic accuracy can be expected.

Hevein-specific recombinant IgE antibodies from human single-chain antibody phage display libraries

IgE antibodies distinctively recognising allergenic epitopes would be ideal reagents in immunodiagnostics to detect and quantify allergens, as well as for the development of allergy diagnostics and therapeutics. We have isolated recombinant human IgE antibodies specific for the major latex allergen, hevein, from antibody phage display libraries using a green fluorescent protein (GFP)-hevein fusion as a selection antigen. Human IgE phage display libraries were constructed by combining the IgE heavy chain genes to kappa and lambda light-chain genes which were isolated from lymphocytes of a latex allergic patient. The screening of antibody libraries resulted in the enrichment of two hevein-binding scFvs designated as 1A4 and 1C2. Both antibodies showed specific binding to the hevein that could be inhibited by both the recombinant GFP-hevein and native hevein isolated from latex examination gloves. The scFvs were prone to aggregate and, thus, for further characterisation, they were converted to Fab fragments with human IgG1 or IgE isotype. Similar hevein-binding properties of the 1A4 and 1C2 Fab fragments and human IgE serum pool, conventionally used in the detection of latex allergens, demonstrate the potential utility of these recombinant antibodies for the analysis of latex allergen.

Allergic and latex-specific sensitization: route, frequency, and amount of exposure that are required to initiate IgE production

Quantitative data that documents human exposure-response relationships for IgE sensitization to allergens are limited. Although seemingly straightforward, documentation of exposure-response relationships can be difficult. Issues that are related to study design, allergen standardization, exposure assessment, and evaluation for sensitization can impact greatly on study results. Despite these issues, exposure-response relationships for sensitization to protein allergens have been documented in several occupational groups, which include enzyme-detergent workers, bakers, and laboratory animal workers. In general, atopy acts as an effect modifier in these settings, steepening the exposure-response relationship. Several studies suggest that the greatest risk for sensitization is within the first several years of exposure. For 1 allergen, the protease subtilisin, a short-term exposure limit of 60 ng/m(3) has been recommended by the American Council of Governmental Industrial Hygienists. With regard to natural rubber latex, exposure-related factors such as number of operations have been shown to be risk factors for sensitization of children with spina bifida. By contrast, fewer studies show exposure-response relationships for IgE sensitization of health care workers to natural rubber latex, and the area remains controversial. However, a recent cohort study that evaluated incident sensitization in dental hygiene students suggests strongly that, with sufficient exposure, employment in health care can lead to an increased risk of IgE sensitization to natural rubber latex.

[Latex-fruit syndrome]

During the last decade, latex IgE-mediated allergy has been recognized as a very important medical problem. At the same time, many studies have dealt with allergic cross-reactions between aeroallergens and foods. In this context, there is clear evidence now on the existence of significant clinical association between latex and fruit allergies. Therefore, a latex-fruit syndrome has been postulated.Several studies have demonstrated that from 20% to 60% of latex-allergic patients show IgE-mediated reactions to a wide variety of foods, mainly fruits. Although implicated foods vary among the studies, banana, avocado, chestnut and kiwi are the most frequently involved. Clinical manifestations of these reactions may vary from oral allergy syndrome to severe anaphylactic reactions, which are not uncommon, thus remarking the clinical relevance of this syndrome.The diagnosis of food hypersensitivities associated to latex allergy is based on the clinical history of immediate adverse reactions, suggestive of an IgE-mediated sensitivity. Prick by prick test with the fresh foods implicated in the reactions shows an 80% concordance with the clinical diagnosis, and therefore it seems to be the best diagnostic test available nowadays in order to confirm the suspicion of latex-fruit allergy. Once the diagnosis is achieved, a diet free of the offending fruits is mandatory.Recently, some of the common allergens responsible for the cross-reactions among latex and the fruits most commonly implicated in the syndrome have been identified. Class I chitinases, with an N-terminal hevein like domain, which cross-react with the major latex allergen hevein, seem to be the panallergens responsible for the latex-fruit syndrome.

Allergenic proteins of natural rubber latex

As the living cytoplasm of laticiferous cells, Hevea brasiliensis latex is a rich blend of organic substances that include a mélange of proteins. A small number of these proteins have given rise to the problem of latex allergy. The salient characteristics of H. brasiliensis latex allergens that are recognized by the International Union of Immunological Societies (IUIS) are reviewed. These are the proteins associated with the rubber particles, the cytosolic C-serum proteins and the B-serum proteins that originate mainly from the lutoids. Procedures for the isolation and purification of latex allergens are discussed, from latex collection in the field to various preparative approaches adopted in the laboratory. As interest in recombinant latex allergens increases, there is a need to validate recombinant proteins to ascertain equivalence with their native counterparts when used in immunological studies, diagnostics, and immunotherapy.

Clinical implications of cross-reactive food allergens

As a consequence of the general increase in allergic sensitization, the prevalence of hypersensitivity reactions to multiple foods that share homologous proteins has become a significant clinical problem. A variety of these allergens conserved among plants (eg, profilin and lipid transfer proteins) and animals (eg, tropomyosin and caseins) have been characterized. Although studies with molecular biologic techniques have elucidated the nature of these ubiquitous allergens, clinical studies have lagged behind. The physician is called on to determine the risk of reaction to related foods among legumes, tree nuts, fish, shellfish, cereal grains, mammalian and avian food products, and a variety of other plant-derived foods that may share proteins with pollens, latex, and each other. Clinical evaluations require a careful history, laboratory evaluation, and in some cases oral food challenges. The pitfalls in the evaluation of food allergy-unreliable histories and limitations in laboratory assessment primarily caused by false-positive skin prick test responses/RAST results are magnified when dealing with cross-reactive proteins. This review focuses on the clinical data regarding cross-reacting food allergens with the goal of providing a background for improved risk assessment and a framework on which to approach these difficult clinical questions.

Characterization and identification of allergen epitopes: recombinant peptide libraries and synthetic, overlapping peptides

For the understanding of the relationship between protein structure and allergenicity, it is important to identify allergenic epitopes. Two methods to characterize primarily linear epitopes are compared using the major allergen from brown shrimp (Penaeus aztecus), Pen a 1, as an example. A recombinant peptide library was constructed and synthetic, overlapping peptides, spanning the entire Pen a 1 molecule, were synthesized and tested for specific IgE reactivity. Both methods identified IgE-binding of Pen a 1, however, the SPOTs procedure resulted in the identification of more epitopes of the major shrimp allergen Pen a 1 than the usage of the recombinant peptide library. For detection of specific IgE antibodies, the usage of 125I-labeled detection antibody seems to be superior over enzyme-labeled anti IgE antibodies. The regeneration of SPOTs membranes is possible, but it is prudent to test regenerated membranes for residual activity. If a given food allergen contains significant linear epitopes, which seems to be true for stable major allergens such as those of peanut and shrimp the SPOTs system may be more advantageous than the use of recombinant peptides libraries. However, if allergens are studied that contain more conformational epitopes, recombinant peptide libraries may help to identify the relevant epitopes. It has to be emphasized that no system for epitope identification will detect all epitopes and that the relevance of identified epitopes has to be confirmed with other methods such as inhibition studies, crystallographic analysis or the immunological evaluation of modified whole allergens.

Hevein, an allergenic lectin from rubber latex, activates human neutrophils' oxidative burst

Hevein is an N-acetyl-D-glucosamine (GlcNAc) specific lectin that has been hypothesized to participate in the IgE-mediated allergic reactions in patients with latex allergy. In this work we assessed the specificity and biological effect of hevein purified from rubber latex on human leukocytes, using epifluorescence microscopy and flow cytometry. Purified human granulocytes were stimulated in vitro with hevein, and production of oxidative radicals was measured by reduction of nitroblue tetrazolium formazan. Histochemical staining and flow cytometry showed that hevein recognizes specifically monocytes (CD14+) and neutrophils (CD16+), but not lymphoid cells. Hevein induced oxidative response in purified granulocytes; this effect was 1.3-1.5-fold higher than the effect observed with the lectin WGA (wheat germ agglutinin), or other lectins with different sugar specificity. The induced reactions and cellular recognition by hevein were inhibited with GlcNAc and its oligomers; as well as by glycoproteins containing tri-and tetra-antennary N-glycosydically linked glycans. Our findings suggest that neutrophils are the main target for latex hevein; this lectin induces production of oxidative radicals, which seem to play an important role in tissue damage during latex allergy.

The latex and food allergy connection

Natural rubber latex is used in the manufacture of many products in the United States. As natural rubber latex allergy becomes of increasing concern, dietitians need to have an understanding of this allergy and how it relates to workplace safety, employee health, and patient feeding and counseling. Natural rubber latex contains more than 35 proteins that may be related to Type I, Ig-E-mediated allergy in numerous segments of the population, including health care workers and patients. Many foods, especially chestnut, banana, and avocado, have the potential to cross-react with natural rubber latex. Chitinase enzymes, related to plant defense, are believed to be involved in this cross-reaction. A strong connection between food allergy and natural rubber latex allergy is recognized and described in this review.

Digestibility of allergens extracted from natural rubber latex and vegetable foods

BACKGROUND

Several cross-reactive allergens are now known to be involved in the defense responses of higher plants. Such proteins are drawing the attention of plant breeders because of their antimicrobial or stress-alleviating activities. Plants genetically modified to express defense-related proteins are being developed. The current concern is focused on the allergenicity of these intentionally expressed proteins.

OBJECTIVE

It is believed that food allergens are proteins resistant to digestion. Digestibility tests have been accepted as an appropriate method for evaluating the allergenicity of newly introduced proteins. In this study we investigated the usefulness of this method for detecting allergens from natural rubber latex and vegetable foods.

METHODS

Proteins were extracted from rubber latex, potato, and 5 kinds of fruits. Simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were used for the digestibility test. An aliquot of each digest was periodically withdrawn and analyzed. Allergens were detected with pooled sera from individuals with latex allergy or patients given a diagnosis of oral allergy syndrome.

RESULTS

Most latex and vegetable food proteins were digested by the SGF within 4 minutes. Numerous allergens were also decomposed by the SGF within 8 minutes. Although vegetable food allergens were relatively stable in the SIF, kiwi allergens were substantially degraded by the SIF within 16 hours.

CONCLUSION

The pronounced lability of the plant-derived allergens was thought to reflect the discrete sensitization and elicitation processes of patients with latex-fruit syndrome or oral allergy syndrome. These results indicate that the allergenicity of a newly expressed protein should be carefully evaluated according to not only its digestibility but also other important properties.

Specific immunotherapy with a standardized latex extract versus placebo in allergic healthcare workers

BACKGROUND

The prevalence of allergy to natural rubber latex proteins has increased over recent years among healthcare professionals but also in children undergoing multiple operations. Exposure to the antigen mainly occurs through the respiratory mucosa and the percutaneous route. Clinical manifestations range from urticaria to angioedema, rhinoconjunctivitis, bronchial asthma, or anaphylactic shock. Preventive measures have been proposed to reduce the risk of sensitization by using only powder-free or synthetic gloves and latex-free material in operating units, but this is not always possible.

OBJECTIVE

The aim of this study was to investigate the efficacy and safety of specific immunotherapy in sensitized workers.

METHODS

Seventeen patients with latex skin allergy and rhinitis (9 of whom also had asthma) were included in this randomized, double-blind, placebo-controlled trial (9 in the active group and 8 in the placebo group) for 1 year. Treatment started with a 2-day course of rush immunotherapy in hospital. Treatment efficacy was assessed after 6 and 12 months by means of symptom and medication scores recorded on diary cards. Conjunctival provocation tests were also performed.

RESULTS

Patients in the active treatment group had a significantly lower total rhinitis score after 6 (P <. 04) and 12 months (P <.05), conjunctivitis score after 6 months (P <. 02), and cutaneous score after 12 months (P <.03) than in the placebo group. Asthma symptoms after 6 or 12 months of treatment were not significantly different between the two groups after adjustment for baseline values. The global medication score was markedly decreased in the latex-treated group. A significant difference in conjunctival reactivity was observed in favor of the active group: the number of patients for whom the threshold dose was increased after 12 months of treatment was significantly greater in the active group than in the placebo group (P <.02). Most injections were well tolerated, but several adverse effects, including hypotension, urticaria, wheezing, and pharyngeal edema, were observed.

CONCLUSION

The clinical benefits observed during the present study included a significant improvement of rhinitis, conjunctivitis, and cutaneous symptoms. Immunotherapy also decreased allergen-specific conjunctival reactivity. Latex-specific immunotherapy may allow sensitized personnel to remain at work, but further trials need to be conducted in a larger number of patients.