Allergen manufacturing and quality aspects for allergen immunotherapy in Europe and the United States: An analysis from the EAACI AIT Guidelines Project

Adequate quality is essential for any medicinal product to be eligible for marketing. Quality includes verification of the identity, content and purity of a medicinal product in combination with a specified production process and its control. Allergen products derived from natural sources require particular considerations to ensure adequate quality. Here, we describe key aspects of the documentation on manufacturing and quality aspects for allergen immunotherapy products in the European Union and the United States. In some key parts, requirements in these areas are harmonized while other fields are regulated separately between both regions. Essential differences are found in the use of Reference Preparations, or the requirement to apply standardized assays for potency determination. As the types of products available are different in specific regions, regulatory guidance for such products may also be available in one specific region only, such as for allergoids in the European Union. Region-specific issues and priorities are a result of this. As allergen products derived from natural sources are inherently variable in their qualitative and quantitative composition, these products present special challenges to balance the variability and ensuring batch-to-batch consistency. Advancements in scientific knowledge on specific allergens and their role in allergic disease will consequentially find representation in future regulatory guidelines.

Challenges in the implementation of EAACI guidelines on allergen immunotherapy: A global perspective on the regulation of allergen products

Regulatory approaches for allergen immunotherapy (AIT) products and the availability of high-quality AIT products are inherently linked to each other. While allergen products are available in many countries across the globe, their regulation is very heterogeneous. First, we describe the regulatory systems applicable for AIT products in the European Union (EU) and in the United States (US). For Europe, a depiction of the different types of relevant procedures, as well as the committees involved, is provided and the fundamental role of national agencies of the EU member states in this complex and unique network is highlighted. Furthermore, the regulatory agencies from Australia, Canada, Japan, Russia, and Switzerland provided information on the system implemented in their countries for the regulation of allergen products. While AIT products are commonly classified as biological medicinal products, they are made available by varying types of procedures, most commonly either by obtaining a marketing authorization or by being distributed as named patient products. Exemptions from marketing authorizations in exceptional cases, as well as import of allergen products from other countries, are additional tools applied by countries to ensure availability of needed AIT products. Several challenges for AIT products are apparent from this analysis and will require further consideration.

Accurate quantification of 5 German cockroach (GCr) allergens in complex extracts using multiple reaction monitoring mass spectrometry (MRM MS)

BACKGROUND

German cockroach (GCr) allergen extracts are complex and heterogeneous products, and methods to better assess their potency and composition are needed for adequate studies of their safety and efficacy.

OBJECTIVE AND METHODS

The objective of this study was to develop an assay based on liquid chromatography and multiple reaction monitoring mass spectrometry (LC-MRM MS) for rapid, accurate, and reproducible quantification of 5 allergens (Bla g 1, Bla g 2, Bla g 3, Bla g 4, and Bla g 5) in crude GCr allergen extracts.

RESULTS

We first established a comprehensive peptide library of allergens from various commercial extracts as well as recombinant allergens. Peptide mapping was performed using high-resolution MS, and the peptide library was then used to identify prototypic and quantotypic peptides to proceed with MRM method development. Assay development included a systematic optimization of digestion conditions (buffer, digestion time, and trypsin concentration), chromatographic separation, and MS parameters. Robustness and suitability were assessed following ICH (Q2 [R1]) guidelines. The method is precise (RSD < 10%), linear over a wide range (r > 0.99, 0.01-1384 fmol/μL), and sensitive (LLOD and LLOQ <1 fmol/μL). Having established the parameters for LC-MRM MS, we quantified allergens from various commercial GCr extracts and showed considerable variability that may impact clinical efficacy.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data demonstrate that the LC-MRM MS method is valuable for absolute quantification of allergens in GCr extracts and likely has broader applicability to other complex allergen extracts. Definitive quantification provides a new standard for labelling of allergen extracts, which will inform patient care, enable personalized therapy, and enhance the efficacy of immunotherapy for environmental and food allergies.

Biological potency of German cockroach allergen extracts determined in an inner city population

BACKGROUND

Cockroach allergy is an important cause of inner city asthma. To perform valid studies on the diagnosis and treatment of cockroach allergy, biological potencies of test extracts need to be established, and a surrogate in vitro test for biological potency should be chosen.

METHODS

Sixty-two cockroach-allergic adult subjects were recruited for quantitative skin testing with three commercial German cockroach extracts. The intradermal D50 values were determined using linear interpolation, and the biologic potencies were determined from D50 data. The extracts were also analysed for relative potency, using a competition ELISA, and for specific allergen content, using a two-site ELISA.

RESULTS

Estimates of each extract's D50 were analysable in 48-55 subjects, with D50s between 10.3 and 11.8. All three extracts were bioequivalent using pre-set criteria. The biological potencies of the extracts were 1738-8570 bioequivalent allergy units (BAU)/mL (geometric mean=3300), and these relative potencies were similar to those estimated by competition ELISA and specific allergen content. IgE against cockroach allergens were detected in sera from 34 subjects with analysable D50s, and 17 subjects had IgE directed against specific cockroach allergens. Although the presence of anti-Bla g 5 correlated with the subjects' skin test responses for 2/3 extracts, no single allergen was immunodominant. Antibody responses among the subjects were heterogeneous.

CONCLUSIONS

Although commercial cockroach extracts are relatively low in potency, immunotherapeutic doses should be achievable. Biological potency may be estimated using D50 testing, a combination of specific allergen determinations, or by an overall potency assay such as the competition ELISA.

CAPSULE SUMMARY

The biological potency of three German cockroach allergen extracts, determined in an inner city population, was 1738-8570 BAU/mL. No one allergen was immunodominant, and surrogate in vitro testing methods were examined.

Competition enzyme-linked immunosorbant assay (ELISA) can be a sensitive method for the specific detection of small quantities of allergen in a complex mixture

RATIONALE

The competition ELISA assay is used to determine the potency of US standardized allergen extracts. We have been concerned that the competition ELISA is not sensitive to changes in individual allergen levels. This study was designed to determine the sensitivity of the competition ELISA to detect the specific loss of Bla g 1 and Bla g 2 in cockroach extracts.

METHODS

German cockroach extract E3Cg was made from defatted German cockroaches. New Zealand White rabbits were immunized with rBla g 1 or rBla g 2. Optimal dilutions of anti-Bla g 1 and anti-Bla g 2 sera were established by ELISA. E3Cg was selectively depleted of Bla g 1 or Bla g 2 by immunoabsorption with anti-Bla g 1 or anti-Bla g 2 attached to Protein G agarose beads. Competition ELISA using pooled human sera, or mixed anti-Bla g 1 and anti-Bla g 2 serum, was performed on the depleted extracts, and on depleted extracts reconstituted with rBla g 1 or rBla g 2.

RESULTS

Unlike pooled human-allergic IgE sera, anti-Bla g 1 and anti-Bla g 2 IgG -- in dilutions as low as 10(-6), could be used in the competition ELISA to measure the loss of allergen in depleted E3Cg. As little as 0.001 microg/mL of added rBla g 1 and 0.1 microg/mL of added rBla g 2, could be detected.

CONCLUSION

The competition ELISA can be highly sensitive to compositional differences in complex allergen mixtures, even when the specific detecting antibody is present in relatively small amounts.

Exploiting the avian immunoglobulin system to simplify the generation of recombinant antibodies to allergenic proteins

BACKGROUND

Monoclonal antibodies are a valuable tool in the study of allergens, but the technology used in their generation can be slow and labour-intensive. Therefore, we have examined recombinant antibody development by phage-display against single allergens and protein mixtures.

OBJECTIVE

We used the avian immunoglobulin system (generated from single V(H) and V(L) genes) to provide a rapid method for generating highly specific recombinant antibody fragments from a minimal number of animals.

METHODS

A single-chain antibody fragment (scFv) library was generated from a single chicken immunized with model allergens. ScFvs were isolated by phage-display and their properties investigated by ELISA and Western blot.

RESULTS

Mono-specific scFvs were generated against recombinant Fel d 1 and native Amb a 1. Pannings against yellow jacket venom extracts only yielded clones that reacted with multiple proteins in the venom extract. The scFvs from each panning type were effectively expressed in Escherichia coli and readily purified. Highly specific and sensitive recognition of Fel d 1 and Amb a 1 was demonstrated in ELISA, with scFvs displaying antibody-concentration-dependent absorbance curves down to picogram levels of antibody. The specificity of selected antibodies for their cognate antigen was further confirmed in Western blot analysis, with scFvs directed to either Fel d 1 or Amb a 1 showing no reactivity for the other antigens used in immunization. Anti-Amb a 1 scFvs also mapped Amb a 1-isoform location in Western blot of ragweed extracts separated by 2D SDS-PAGE. DNA sequence analysis of scFvs showed that multiple different clones had been generated against Fel d 1 and Amb a 1. Using two anti-Fel d 1 scFv for ELISA analysis of Fel d 1 content in crude cat pelt extracts, we could produce data which were highly similar (P=0.33 and 0.89 by paired t-test analysis) to those obtained using conventional assays (radial immunodiffusion).

CONCLUSION

Phage-display technology may generate multiple allergen-specific recombinant antibody fragments from a single chicken, to allergens from mammalian, plant and insect sources. The resulting antibody fragments are of demonstrable use in allergen identification and quantification, in comparison with standard immunoassays.

Characterization of allergen extracts

Allergen vaccines are complex extracts of natural products, and are used for the diagnosis and treatment of allergic diseases. In the U.S., 19 allergen extracts have been standardized. For these vaccines, the potency is estimated by the skin test responses of highly allergic individuals, and surrogate in vitro tests are established for lot release and quality control. The surrogate tests differ for different extracts. National reference standards to which manufactured lots are compared are maintained at FDA/CBER. Allergen standardization has facilitated the establishment of data-driven release limits.

Characterization and comparison of commercially available German and American cockroach allergen extracts

BACKGROUND

In this study we examine the variability among unstandardized cockroach allergen extracts.

METHODS

We obtained 24 aqueous and glycerinated cockroach allergen extracts from nine manufacturers. We used previously characterized cockroach extracts, E2-Cg and E2-Ca, as references. The modified ninhydrin assay was used to determine protein concentration of each extract. Relative potencies of extracts were determined by competition ELISA, using a human allergic serum pool. Bla g 1 and Bla g 2 levels of glycerinated German cockroach extracts were determined by ELISA using monoclonal antibodies. Extracts were also analysed by SDS-PAGE.

RESULTS

Commercial cockroach allergen extracts had highly variable protein contents that were lower than the protein contents of the references. Electrophoretic data confirmed the presence of a variable number and intensity of protein bands in extracts among manufacturers. The relative potencies of the commercial extracts were between 10 and 782 BAU/mL for German cockroach and 10-250 BAU/mL for American cockroach. The mean Bla g 1 content of the commercial extracts was significantly lower than that of the reference (P = 0.001). The mean Bla g 2 content of the commercial extracts was higher than that of the E2-Cg reference but the Bla g 2 levels were more variable compared to Bla g 1. In glycerinated German cockroach extracts, protein concentrations, relative potencies and specific allergen levels were significantly correlated (P < 0.001).

CONCLUSION

Our tests indicate that commercially available cockroach allergen extracts are variable in protein content, electrophoretic banding patterns, relative potency and Bla g 2 levels. In glycerinated German cockroach extracts, protein concentrations, relative potencies and specific allergen levels were significantly correlated.

Specific monoclonal antibodies and human immunoglobulin E show that Hev b 5 is an abundant allergen in high protein powdered latex gloves

BACKGROUND

Hev b 5 is a major latex allergen recognized predominantly by latex-allergic health care workers (HCWs). Recombinant Hev b 5 (rHev b 5) was previously expressed as a fusion protein with maltose binding protein (MBP), itself an immunogenic molecule; therefore non-fusion rHev b 5 is desirable. Moreover, standardized immunological assays for the detection of Hev b 5 are currently lacking and may have important implications for both allergen avoidance and diagnosis in latex allergy.

OBJECTIVES

To generate and use Hev b 5-specific mAbs to determine the relative abundance of Hev b 5 in different latex extracts, correlating this with the IgE reactivity of latex-allergic HCWs and to produce non-fusion rHev b 5.

METHODS

For the production of mAbs, mice were immunized with rHev b 5/MBP fusion protein and mAbs selected with rHev b 5/MBP but not MBP reactivity. The mAb reactivity was compared with polyclonal IgE from latex-allergic HCWs using direct and inhibition ELISA and immunoblot assays. Recombinant Hev b 5 was expressed and purified in the pPROEX-HTa bacterial expression system.

RESULTS

Four Hev b 5-specific mAbs were produced. Immunoblotting and ELISA using the mAbs indicate abundant Hev b 5 in high protein powdered latex glove extracts as compared with crude latex sap extracts. High quality surgical gloves with no detectable protein have no detectable Hev b 5. Inhibition ELISAs using serum IgE from latex-allergic HCWs and Hev b 5-specific mAbs gave strong correlation. Non-fusion recombinant Hev b 5 was successfully expressed and purified, showing reactivity with both the Hev b 5-specific mAbs and serum IgE of latex-allergic HCWs.

CONCLUSION

Hev b 5-specific mAbs and human IgE from latex-allergic HCWs demonstrate the greater content of Hev b 5 in high protein powdered glove extracts. This may explain the observed higher frequency of sensitization to this allergen in HCWs.

Human cytomegalovirus UL37 immediate-early regulatory proteins traffic through the secretory apparatus and to mitochondria

The human cytomegalovirus (HCMV) UL36-38 immediate-early (IE) locus encodes the UL37 exon 1 (pUL37x1) and UL37 (gpUL37) regulatory proteins, which have anti-apoptotic activities. pUL37x1 shares its entire sequence, including a hydrophobic leader and an acidic domain, with the exception of one residue, with the amino terminus of gpUL37. gpUL37 has, in addition, unique N-linked glycosylation, transmembrane and cytosolic domains. A rabbit polyvalent antiserum was generated against residues 27-40 in the shared amino-terminal domain and a mouse polyvalent antiserum was generated against the full-length protein to study trafficking of individual UL37 proteins in human cells that transiently expressed gpUL37 or pUL37x1. Co-localization studies by confocal laser scanning microscopy detected trafficking of gpUL37 and pUL37x1 from the endoplasmic reticulum to the Golgi apparatus in permissive U373 cells and in human diploid fibroblasts (HFF). Trafficking of gpUL37 to the cellular plasma membrane was detected in unfixed HFF cells. FLAG-tagged gpUL37 trafficked similarly through the secretory apparatus to the plasma membrane. By using confocal microscopy and immunoblotting of fractionated cells, gpUL37 and pUL37x1 were found to co-localize with mitochondria in human cells. This unconventional dual trafficking pattern through the secretory apparatus and to mitochondria is novel for herpesvirus IE regulatory proteins.

Latex allergy

Latex allergy continues to be an important medical problem. In this review we re-examine the definition of latex allergy, the offending allergens, the factors that enhance sensitization, the threshold levels that sensitize and elicit reactions in sensitized individuals, current diagnostic techniques, avoidance measures, the barrier properties of nonlatex alternatives, and the roles of premedication and immunotherapy. Twenty years after its resurgence, latex allergy is a well-defined condition with established diagnostic criteria and rational treatment and prevention strategies. However, in spite of advances associated with molecular studies of latex allergens and improved understanding of immunotherapy, avoidance remains the only effective treatment.

Human T-cell epitopes of the latex allergen Hev b 5 in health care workers

BACKGROUND

Latex allergy affects health care workers as a high-risk cohort. Hev b 5 is a major latex allergen reacting with serum IgE from 92% of latex-allergic health care workers. Because CD4(+) T-cell recognition is central to the specific immune response to allergens, identification of dominant T-cell epitopes is important for the development of specific immunotherapy for latex allergy.

OBJECTIVE

Our purpose was to map T-cell epitopes of Hev b 5 in health care workers.

METHODS

Six latex-allergic health care workers (grade 3 to 4 enzyme allergosorbent test score) were studied. Peripheral blood latex specific 3-week T-cell lines were generated and screened for proliferative response to overlapping 20-mer peptides of Hev b 5. Supernatants collected at 48 hours were analyzed by ELISA for IL-5 and IFN-gamma.

RESULTS

Dot immunoblotting with use of recombinant Hev b 5/maltose-binding protein indicated serum-specific IgE in 5 of 6 patients. T-cell reactivity to one or more Hev b 5 peptides was identified in these 5 donors, but not in the sixth. Hev b 5 (46-65) induced T-cell proliferation in all 5 donors. Hev b 5 (109-128) stimulated T cells from 3 of these patients. Proliferative responses were accompanied by substantial IL-5 secretion and minimal IFN-gamma, indicating a T(H)2-predominant cytokine profile.

CONCLUSIONS

Five of 6 latex-allergic patients demonstrated T-cell responsiveness to Hev b 5 consistent with a major T-cell reactive latex allergen. Two T-cell immunodominant regions of Hev b 5 were identified, and reactivity to these sites was associated with strong IL-5 but minimal IFN-gamma production.

The determination of equivalent doses of standardized allergen vaccines

BACKGROUND

Standardized allergen vaccines are tested for potency by manufacturers by using assays proposed in their license applications and approved by the Center for Biologics Evaluation and Research, which reviews and verifies the test results before lot release. The current lot-release limits for mite and grass pollen allergen vaccines impose statistical equivalence to the national reference extract; thus the limits are primarily based on assay variability.

OBJECTIVE

We sought to establish a clinical basis for lot-release limits for the relative potency of allergen vaccines and to evaluate alternative specifications.

METHODS

We performed literature selection and review, linear and logistic regression analyses of selected studies, and analysis of lots submitted to the Food and Drug Administration for approval since 1995.

RESULTS

Therapeutic equivalence is achieved over a 10-fold range of allergen concentration. Safety equivalence is more difficult to assign, but on the basis of injection data, a 4-fold increase in allergen concentration is associated with a 5% to 10% increase in adverse reaction rates. The SD in log relative potency for the submitted allergenic products was determined to be 0.090 for grasses and 0.061 for mites, compared with 0.079 for competition ELISA.

CONCLUSIONS

Current lot-release limits are well within literature-based estimates of therapeutic, diagnostic, and safety equivalence ranges for the clinical use of allergen vaccines. In addition, the aggregate consistency of the submitted products is comparable with the precision of the assay that is used to assess the products. These results support expanded release limits for verification of relative potency, provided the submitted lots of material remain at their present level of consistency.

The stability of house dust mite allergens in glycerinated extracts

BACKGROUND

Mite allergen vaccines are important diagnostic and immunotherapeutic reagents. Previous studies on mite allergen stability under different storage conditions have yielded contradictory results.

OBJECTIVE

We sought to compare, over a 12-month period, the stability of mite allergens reconstituted in 50% glycerol and stored at different temperatures and to examine the role of protease inhibitors in enhancing allergen stability.

METHODS

Lyophilized allergen extracts were reconstituted in 50% glycerol, with and without protease inhibitors, and stored at -70 degrees C, -20 degrees C, 4 degrees C, or 37 degrees C for 12 months. At 6 and 12 months, the extracts were compared with freshly dissolved extracts by competition ELISA with pooled allergic sera, 2-site ELISA with mite-specific mAbs, and immunoblot analyses.

RESULTS

The overall potencies of the stored extracts measured by competition ELISA were stable at -20 degrees C and 4 degrees C. As determined by means of the immunoblot and 2-site ELISA, Der f 1 levels decreased at 4 degrees C. Levels of Der f 2, Der p 1, and Der p 2 decreased in at least one of the allergen-specific assays. Storage at 37 degrees C led to overall loss of potency and allergen content, whereas storage at -70 degrees C was associated with a moderate loss of potency that increased with multiple freeze-thaw cycles. Protease inhibitors had no effect on allergen stability.

CONCLUSION

Although overall potency of the extracts, as measured by competition ELISA, was preserved at -20 degrees C and 4 degrees C, allergen-specific assays indicated loss of allergens. These findings suggest that the competition ELISA is insensitive to decreases in the concentrations of individual allergens.

Human IgE-binding epitopes of the latex allergen Hev b 5

BACKGROUND

Hev b 5 is an acidic protein (isoelectric point, 3.5) rich in glutamic acid with 9 repeated amino acid (AA) sequences of XEEX or XEEEX. Although its function in Hevea brasiliensis is unknown, Hev b 5 has been identified as a major latex allergen. Immunoblot inhibition studies suggest Hev b 5 exists as multiple isoforms or contains a common epitope found in several other proteins.

OBJECTIVE

The purpose of this study was to further characterize Hev b 5 and to identify linear IgE-binding epitopes.

METHODS

Octapeptides spanning the entire Hev b 5 protein were synthesized on a derivatized cellulose membrane. The membrane was reacted with sera pooled from health care workers allergic to latex or rabbits immunized with latex proteins. B-cell epitopes were identified by subsequent incubations with the appropriate secondary antibodies and detected by using chemifluorescence.

RESULTS

Sera from patients allergic to latex recognized 6 IgE-binding regions located throughout the molecule. Two epitopes (2 and 4) had the common AA sequence of KTEEP. Epitopes 3 and 5 had a similar AA sequence of EEXXA, where X was P, T, or K. Epitopes 1 and 6 appeared to be unrelated to the other epitopes. Database analysis could not identify other proteins with similar sequences. Neither of the XEEEX sequences bound IgE. Control sera failed to react to any peptides.

CONCLUSIONS

Hev b 5 exists as multiple isoforms, but only small amounts are present in the nonammoniated latex preparations, such as those used for diagnostic tests, and this may help to explain the relatively poor sensitivity of some in vitro tests.

Defects of T-cell effector function and post-thymic maturation in X-linked hyper-IgM syndrome

X-linked hyper-IgM syndrome (XHIM) results from mutations in the gene encoding for CD40 ligand (CD154). Patients with the syndrome suffer from infections with opportunistic pathogens such as Cryptosporidium and Pneumocystis carinii. In this study, we demonstrate that activated T cells from patients with XHIM produce markedly reduced levels of IFN-gamma, fail to induce antigen-presenting cells to synthesize IL-12, and induce greatly reduced levels of TNF-alpha. In addition, we show that the patients' circulating T lymphocytes of both the CD4(+) and CD8(+) subsets contain a markedly reduced antigen-primed population, as determined by CD45RO expression. Finally, we demonstrate that the defects in antigen priming are likely due to the lack of CD154 expression and insufficient costimulation of T cells by CD80/CD86 interactions. Taken together, this study offers a basis for the increased susceptibility of patients with XHIM to certain opportunistic infections.

Murine B-cell and T-cell epitopes of the allergen Hev b 5 from natural rubber latex

Hev b 5, a proline-rich acidic protein with a predominantly random secondary structure, is a major allergen in natural rubber latex and a candidate for specific immunotherapy of latex allergy. As a first step in the identification of candidate peptides for immunotherapy, we have begun to identify the B-cell and T-cell epitopes of Hev b 5 in BALB/c mice. The mice were immunized with a Hev b 5 fusion protein. The B-cell epitopes were determined by the SPOTS method using overlapping octamers or by ELISA inhibition using a series of overlapping 20-mers. The T-cell epitopes were determined by the proliferation and cytokine release of splenocytes cultured in the presence of the 20-mers. Potential antibody binding regions included residues in regions 1-38, 55-74, 109-128 and 132-151. Examination of the binding sequences for common motifs suggested enhanced antibody binding to the KXEE or KEXE sequences, where X is empty, threonine or alanine. Splenocyte stimulation and cytokine release suggest T-cell epitopes with the regions 1-20, 37-56, 73-101 and 109-146. Since they may contain major T-cell epitopes but do not exhibit significant antibody binding, peptide regions 38-48 and 75-101 are candidates for specific immunotherapy to Hev b 5 in the BALB/c mouse model.

Lipopolysaccharide augments IgG and IgE responses of mice to the latex allergen Hev b 5

BACKGROUND

LPS is a common contaminant in the health care environment and in latex examination gloves.

OBJECTIVE

We sought to investigate the role of LPS in enhancing the immune responses of mice to inhaled latex allergen.

METHODS

As our model allergen, we used a fusion protein containing the potent latex allergen Hev b 5. BALB/c mice were lightly anesthetized and given repeated intranasal doses of saline, LPS, and/or Hev b 5. The doses were given in 2 courses separated by a 6-week period, with the first course consisting of 6 doses and the second consisting of 3 doses.

RESULTS

After the first set of immunizations, mice given Hev b 5 alone had no detectable IgG1 or IgE responses to Hev b 5, whereas mice given the antigen along with LPS had significant responses (IgG1, 0.73 U +/- 0.05; IgE, 0.88 U +/- 0.2). No enhancement of specific IgG2a was observed. A stimulatory effect of LPS on all 3 immunoglobulin types was apparent after the second course. Lymphocytes from mice immunized with LPS and Hev b 5 had increased proliferation to Hev b 5 and its fusion partner.

CONCLUSIONS

LPS may be an important immunoadjuvant for the development of allergic reactions to latex protein allergens.

The latex allergen Hev b 5 transcript is widely distributed after subcutaneous injection in BALB/c mice of its DNA vaccine

BACKGROUND

DNA vaccines reduce IgE responses to selected allergens, but severe reactions to the expressed antigen may limit the usefulness of the technique in allergen immunotherapy.

OBJECTIVE

We sought to determine the extent of spread of an injected DNA vaccine in mice.

METHODS

We placed the gene encoding the potent Hevea latex allergen Hev b 5 in a mammalian expression vector and injected this DNA vaccine subcutaneously into BALB/c mice. At several times after injection, the presence of Hev b 5 transcript was determined in multiple tissues by RT-PCR. The identity of the amplification product was confirmed by Southern hybridization and restriction analyses.

RESULTS

Hev b 5 RNA appeared at the injection site and in the lymph nodes, spleen, and lungs within 1 day after injection and persisted for at least 14 days. Hev b 5 RNA was also identified in the blood and tongue 14 days after injection. Antibody and cell-mediated responses to Hev b 5 were also noted in the immunized animals at later time points. As expected, animals injected with the identical plasmid containing the Hev b 5 DNA in the antisense orientation mounted no immune response to Hev b 5.

CONCLUSIONS

The rapid and widespread appearance of the Hev b 5 transcript in the injected mice confirms that DNA is translocated from the injection site, transcribed, and expressed in immune and nonimmune tissues after injection. Controlling the extent and degree of expression in specific target tissues may allow therapeutic DNA vaccination with plasmids that encode potentially toxic allergens.

Identification, cloning, and sequence of a major allergen (Hev b 5) from natural rubber latex (Hevea brasiliensis)

Proteins in commercial latex products, derived from the rubber tree Hevea brasiliensis, cause anaphylaxis in susceptible individuals, especially health care workers and children with spina bifida. To identify latex allergens, we utilized IgE from the serum of a latex-allergic health care worker to screen a cDNA library from Hevea latex. The identified cDNA clone, cDNA Hev b 5, encodes an open reading frame of 163 peptide residues. Hybridization analysis of cDNA Hev b 5 with RNA extracted from Hevea tissue indicates that the full-length transcript is about 1000 bases. The nucleotide and deduced protein sequences have significant homology to sequences from kiwi and potato, which are known to cause allergic reactions in some latex-allergic patients. Fifty-six percent of spina bifida patients and 92% of health care workers with latex allergy have IgE specific to the protein encoded by cDNA Hev b 5. A monoclonal antibody raised from a mouse immunized with Hev b 5 binds to a protein in Hevea latex with an Mr identical to that of the expressed and cleaved recombinant protein. Taken together, these results establish that the antigen Hev b 5 contains a major epitope for IgE-mediated reactions to H. brasiliensis latex products.

Latex hypersensitivity in children

Latex is a natural substance used in the manufacture of thousands of products. Although latex allergy is uncommon in the general population, health care workers and children with spina bifida appear to be at high risk for latex allergy. These patients may experience urticaria, rhinoconjunctivitis, bronchospasm, and anaphylaxis following contact with or inhalation of latex antigens. Several protein allergens in latex have been identified, some of which appear to cross-react clinically and immunochemically with fruit antigens. Good diagnostic tests are available for latex allergy, but strict avoidance is still the only available treatment.

A cluster of anaphylactic reactions in children with spina bifida during general anesthesia: epidemiologic features, risk factors, and latex hypersensitivity

BACKGROUND

Anaphylactic reactions (ARs) in high-risk pediatric patients undergoing general anesthesia, especially those with spina bifida, have been attributed to anesthetics, muscle relaxants, antimicrobials, ethylene oxide, and latex.

METHODS

To identify risk factors for AR during general anesthesia and to investigate the role of latex allergy, we studied epidemiologic and immunologic characteristics of patients with ARs during general anesthesia during a 13-month cluster of such reactions at Children's Hospital of Wisconsin (case patients). Patients with AR were compared with patients with spina bifida undergoing uneventful general anesthesia during the same period (control patients). For each case patient and control patient, we conducted a chart review; a parental interview; skin prick testing with latex, anesthetics, aeroallergens, and banana extract; ELISA and RAST for latex-specific IgE; a total serum IgE; and an ELISA for IgE antibody to ethylene oxide.

RESULTS

Anaphylactic reactions occurred exclusively in patients with spina bifida (n = 10) or patients with a congenital urinary tract anomaly (n = 1). Case-patients were more likely than control patients to have a history of asthma (p = 0.002), rubber contact allergy (p = 0.001), food allergy (p = 0.001), rash caused by adhesive tape (p = 0.05), daily rectal disimpaction (p < 0.001), nine or more prior surgical procedures (p < 0.002), latex-specific IgE (p = 0.027), or elevated total serum IgE levels (p = 0.002). Multivariate analysis identified non-white race, rubber contact allergy, history of food allergy, and nine or more surgical procedures as significant independent risk factors. Logistic model equation identified the predicted probability of AR with a sensitivity, specificity, and positive predictive value of 82%, 97%, and 82%, respectively.

CONCLUSIONS

These findings demonstrate that atopy, especially symptomatic latex allergy, is associated with AR during anesthesia in patients with spina bifida. Until a standardized latex test is available, a medical history of immediate rubber contact allergy, non-white race, food allergy, or nine or more prior surgical procedures can identify patients with spina bifida at highest risk for ARs. A complete history, including rubber contact and food allergy, should be compiled on all patients with spina bifida before surgery.

Immunodetection of latex antigens

BACKGROUND

Protein antigens in latex products can cause type I reactions. In the past antigens have been measured by protein assays, high-performance liquid chromatography, RAST inhibition, and skin tests. We examined the use of a mouse monoclonal antibody (CRI-C) to latex in the detection of latex antigens.

METHODS

CRI-C was raised by standard techniques after immunization of a BALB/c mouse with ammoniated latex. Medical gloves were extracted and assayed with: (1) standard protein assays, (2) RAST inhibition assays with sera from health care workers allergic to latex and patients with spina bifida, (3) an ELISA with a biotinylated form of CRI-C (BiC). Reference proteins included bovine serum albumin for the protein assays and nonammoniated latex and affinity-purified C antigen for the immunoassays.

RESULTS

Among the protein assays, the best correlation was between the Bradford and bicinchoninic acid assays. In absolute numbers the Bradford assay produced the lowest results, and OD280 the highest. The OD280, BCA, and Bradford methods "detected" protein in vinyl gloves. The results of RAST inhibition and BiC ELISA correlated with the protein assays. These immunoassays appeared to be more specific than the protein assays.

CONCLUSIONS

The BiC ELISA is an easy and reproducible in vitro assay of relevant latex antigen. Clinical correlation will be required for validation.

Affinity purification of latex antigens

Latex extracts are complex mixtures of antigenic peptides. We attempted to raise monoclonal antibodies to latex and to use these antibodies to purify latex antigens. A monoclonal antibody, CRI-C, was raised by standard techniques. Peptides of nonammoniated latex (NAL) and ammoniated latex were electrophoretically separated and transferred for immunoblots. CRI-C was covalently attached to an agarose column. NAL was passed over the column, and purified antigen was then eluted. The eluate was analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis and RAST inhibition with sera from health care workers and children with spina bifida. CRI-C recognized a single band in ammoniated latex immunoblots and several distinct bands in NAL. The affinity-purified antigen of CRI-C (C-Ag) had multiple bands of less than 20 kd and was 3.9 times more potent in RAST inhibition than NAL when sera from patients with spina bifida were used. However, when health care workers' sera were used, there was no significant difference in the inhibitory potency of NAL and C-Ag. CRI-C appears to recognize a distinct and important epitope in the IgE immune response to latex of patients with spina bifida.

Latex allergy in children

Natural latex, a product of the tropical rubber tree, Hevea brasiliensis, has been shown to cause allergic reactions in an increasing number of individuals. Severity of reaction has ranged from mild contact dermatitis to anaphylaxis. Individuals with spina bifida, congenital urogenital anomalies, health care workers, and those employed in the rubber industry are at highest risk for immediate hypersensitivity to latex. Health care workers should be aware of this high risk to minimize exposure of patients.

Latex allergy in spina bifida patients: prevalence and surgical implications

We interviewed 93 consecutive children with spina bifida who were scheduled for operation to document (a) the prevalence of latex sensitivity, (b) predictors of anaphylactic reaction, and (c) the risk of type I hypersensitivity reaction perioperatively. Of these patients, 9.7% were clinically allergic. Radioallergosorbent testing (RAST) was 89% sensitive. All patients with known latex allergy were premedicated, and rigorous efforts were made to avoid latex exposure. No intraoperative anaphylactic reactions were noted. One postoperative reaction occurred in a history-positive, RAST-negative patient. We conclude that operation can be performed safely in patients with latex allergy.

Allergic reactions to natural rubber

Immediate hypersensitivity reactions to natural rubber pose a significant risk to patients with spina bifida and urogenital abnormalities, health care workers, and rubber industry workers. Other patients, outside of these high risk groups, have experienced severe allergic reactions to natural rubber as well. Awareness of this life-threatening condition by health care providers is essential if reactions are to be prevented. History alone is inadequate to identify all patients at risk, and reliable testing materials are not yet approved or widely available. Nonrubber medical devices are readily available for most uses; however, the only rubber-free condoms currently on the market do not prevent the transmission of sexually transmitted disease. The identification and detection of rubber antigens, along with mandated labeling for rubber antigen content, will contribute to the care of this growing population of patients. Efforts by the rubber industry to decrease the antigen content of natural rubber products will decrease the risk of reaction among sensitized patients and will, very likely, decrease the rate of sensitization in the future.

Latex antigens

Previous studies have demonstrated that some children with spina bifida have IgE to proteins in natural rubber. In this study we compare different sources of latex antigen and identify possible antigenic peptides by radioimmunoblotting technique. Sera were collected from 26 children with spina bifida, tested by RAST with ammoniated latex extract (AL), and frozen until use. Extracts were prepared from ammoniated and nonammoniated latex, and the proteins were separated by electrophoresis on a 15% sodium dodecyl suflate-polyacrylamide gel and transferred to polyvinylene difluoride (PVDF). Strips of PVDF were then incubated with individual sera and 125I-labeled rabbit antihuman IgE before development by autoradiography; 18/26 sera were AL RAST positive; 0/8 AL RAST-negative patients had any binding to the latex proteins on PVDF. Sera from all patients were tested in a RAST with a nonammoniated latex extract (NAL), and the results were comparable to the AL RAST. Liquid-phase AL and NAL were comparable in their ability to inhibit the binding of patient's IgE to solid-phase AL and NAL. Sera from 14 RAST-positive patients were tested by immunoblotting with separated, reduced, and nonreduced AL and NAL. All 14 sera demonstrated IgE binding to a 14 kd peptide, which was more pronounced in reduced NAL. These results suggest that the 14 kd peptide in NAL is a major antigen in rubber allergy but that AL is an acceptable antigen source for in vitro diagnostic studies.

Rubber-specific IgE in children with spina bifida

We attempted to determine the prevalence and clinical significance of rubber-specific IgE in a prospective case control study of 32 preoperative children with spina bifida, compared with 45 outpatient controls and 35 age-matched preoperative controls without spina bifida. A latex-specific radioallergosorbent test was positive in 11 of the 32 spina bifida patients (34%), compared with 1 (2%) and 4 (11%) of the respective controls (p less than 0.05). Within the spina bifida group 5 of 11 antibody-positive patients had a history of rubber-associated, intraoperative or otherwise idiopathic allergic episodes and 1 of 21 antibody-negative patients gave such a history (p = 0.012). Children with spina bifida have a significantly greater likelihood than controls of having IgE specific for rubber antigens. In addition, the presence of rubber-specific IgE is associated with a higher frequency of rubber-associated, intraoperative or idiopathic allergic reactions.

IgE immunotoxins. Effect of an IgE-ricin A chain conjugate on rat skin histamine content

Immunotoxins--toxins covalently conjugated to specific antibodies--have been studied as possible agents in the treatment of cancer. The avid binding of IgE antibodies to FcR on mast cells and basophils suggested the possible use of an IgE-immunotoxin in the treatment of malignant mastocytosis or as a method to generate mast cell-depleted animals for study. To this end, the effect of a covalent conjugate of rat myeloma IgE and ricin A chain on rat cutaneous mast cells was examined in vivo. IgE-ricin A chain was capable of binding to and sensitizing cutaneous mast cells in vivo as indicated by a bluing response to intracutaneous anti-ricin A chain. IgE-ricin A chain, given either as a single dose or, even more effectively, as two split doses, significantly reduced cutaneous histamine content for 6 to 8 days. Neither a mixture of IgE and ricin A chain that were not conjugated nor the induction of cutaneous mast cell degranulation with anti-IgE affected cutaneous histamine levels. Therefore, IgE-ricin A chain produces a prolonged depletion of cutaneous histamine levels.

IgE immunotoxins. Effect of an IgE-ricin A chain conjugate on rat skin histamine content

Immunotoxins--toxins covalently conjugated to specific antibodies--have been studied as possible agents in the treatment of cancer. The avid binding of IgE antibodies to FcR on mast cells and basophils suggested the possible use of an IgE-immunotoxin in the treatment of malignant mastocytosis or as a method to generate mast cell-depleted animals for study. To this end, the effect of a covalent conjugate of rat myeloma IgE and ricin A chain on rat cutaneous mast cells was examined in vivo. IgE-ricin A chain was capable of binding to and sensitizing cutaneous mast cells in vivo as indicated by a bluing response to intracutaneous anti-ricin A chain. IgE-ricin A chain, given either as a single dose or, even more effectively, as two split doses, significantly reduced cutaneous histamine content for 6 to 8 days. Neither a mixture of IgE and ricin A chain that were not conjugated nor the induction of cutaneous mast cell degranulation with anti-IgE affected cutaneous histamine levels. Therefore, IgE-ricin A chain produces a prolonged depletion of cutaneous histamine levels.

Recurrent anaphylaxis in menstruating women: treatment with a luteinizing hormone-releasing hormone agonist--a preliminary report

Recurrent idiopathic anaphylaxis is an illness consisting of recurring anaphylactic or anaphylactoid attacks of unknown cause. A patient has been described whose attacks appeared to be associated with endogenous progesterone secretion and who was treated successfully with an analog of luteinizing hormone-releasing hormone (LHRH). This report summarizes the treatment of four additional women with recurrent anaphylaxis in a randomized, double-blind trial of an LHRH agonist and placebo. Two out of the four women experienced remission of their symptoms with the LHRH analog. The patients who responded to therapy had experienced systemic anaphylactoid reactions after provocation with an LHRH infusion and the intradermal injection of medroxyprogesterone; the nonresponders had no adverse reactions to either challenge. Ovarian suppression with LHRH agonist may benefit a subset of women with recurrent idiopathic anaphylaxis.

Effects of sex hormones on basophil histamine release in recurrent idiopathic anaphylaxis

A subset of patients with recurrent anaphylaxis experience ovarian hormone-related exacerbations. Symptoms in several of these women may be provoked by gonadotropins or progesterone (P) and improved by ovarian suppression, with long-term remissions noted in several patients after oophorectomy. Since adverse reactions to P might explain this association, the effects of P and estrogen on basophil histamine release from these patients were studied. Eight patients and 10 control subjects were examined. Neither estrogen nor P caused histamine release from the basophils of patients or control subjects. Moreover, anti-IgE-induced histamine release was not influenced by P or estrogen. Attempts to culture basophils for 24 hours revealed that basophil preparations from eight of 10 normal subjects but only three of eight patients retained the capacity to respond to anti-IgE after 24 hours (p = 0.088). Culture with dexamethasone reduced anti-IgE-induced histamine release in all subjects, and the possibility that P might interfere with the effect of dexamethasone was also studied. P failed to affect dexamethasone-induced reduction of basophil histamine release. Therefore, P and estradiol appear to have no effect on basophils from either patients with hormone-related exacerbations of anaphylaxis or from control subjects.

Surveillance of Reye syndrome in the United States, 1977

Between December 1, 1976, and November 30, 1977, 454 cases of Reye syndrome were reported to the Centers for Disease Control by 43 states. Analysis of data about these cases revealed that Reye syndrome primarily affected white children under age 18 years, with a mean age of 7.7 years and bimodal incidence peaks in infancy and at age 6-7 years, was temporally and geographically associated with influenza B for about 75% of cases, but also occurred sporadically and not in association with influenza B activity. Although Reye syndrome was reported infrequently for non-white children aged one year or older, there was a high incidence in minority infants, and the case-fatality ratio in infants of all races was significantly higher than that of the older children. Favorable outcome was associated with prolonged interval between onset of prodromal illness and hospitalization, admission to hospital at a milder stage of illness, and treatment in hospitals with established pediatric training programs.