Michaela Lucas. Clinical Immunologist/Immunopathologist. Pathwest, QE2 Medical Centre, Princess Margaret Hospital

Transcription

1 Michaela Lucas Clinical Immunologist/Immunopathologist Pathwest, QE2 Medical Centre, Princess Margaret Hospital School of Medicine and Pharmacology, School of Pathology and Laboratory Medicine University of Western Australia; IIID, Murdoch University

2 Allergy in Australia-The Present In Australia: Children < 1 yr: 10% Children < 5 yrs: 4-8% Adults: up to 2% 1.13

3 Anaphylaxis Anaphylaxis is the most severe form of allergic reaction (immediate IgE mediated reaction) Symptoms and signs of anaphylaxis: Difficult/noisy breathing Swelling of tongue Swelling/tightness in throat Difficulty talking and/or hoarse voice Wheeze or persistent cough Persistent dizziness or collapse Pale and floppy (young children) Mild or moderate signs and symptoms may not always precede anaphylaxis

4 Time trends Anaphylaxis in Australian Hospitals Cause of anaphylaxis admission by age group Mullins R et al., JACI 2015

5 Diagnosis - identification of allergic triggers Suspected allergy should always be confirmed Clinical history Tests to identify IgE sensitisation to an allergen Skin Prick Testing (SPT) Serum allergen specific IgE (a blood test formerly known as RAST; IgE/IgG4) Medically supervised food allergen challenge Positive allergy tests do not always result in clinical allergy (sensitisation versus reaction) Skin prick testing

6 Promising new diagnostics Molecular and component-resolved diagnostics tests for serum screening are increasingly available AraH2 (peanut component) sensitivity of 100% and specificity of 70-80% Omega-5-gliadin (wheat) diagnostic relevance for exercise induced anaphylaxis rglym4 for allergy to soy in birch allergic individuals may be helpful for fruit, vegetable, nut, soy and seafood allergies Basophil activation assays (BAT) are promising, but currently mainly a research tool 6

7 Investigation of IgE mediated reactions Basophil activation assays

8 Immediate allergic reactions Result of IgE production by antigen-specific B cells after sensitisation Following re-exposure, the Ag (haptenated) crosslinks IgE bound to mast cells and basophils, leading to the release of preformed mediators Natural history: IgE antibody responses wane over time, however sensitisation may persist for years

9 Introduction-Basophil biology

10 Basophil activation Mediator release Stimulus Granules (e.g. histamine) Lipids (e.g. Leukotriene C4) Cytokines (e.g.il4)

11 Basophil activation Newly or increased cell-surface marker expression Stimulus CD11b ST2 (IL33R) CD13 CD203c CD164 CD63 CD107a/c CD69

12 Novel marker expression

13 Piecemeal and anaphylactic degranulation Basophil Piecemeal Degranulation Histamine release No CD63 upregulation CD203c? upregulation CD63 CD63 Anaphylactic degranulation Histamine release CD63 upregulation

14 Principle of Basophil activation testing Flow based assay Measures activation of basophils upon allergen stimulation Uses two activation markers CD63 and CD203c CD63 is also expressed on platelets, eosinophils and monocytes; assays therefore use additional basophil markers (CD123, CCR3, CRTH2, IgE and CD203c) CD203c exclusively expressed on basophils, including resting at low levels

15 Commercially available assays Uses whole blood (100 microliter) or separated PBMCs Uses the expression of CCR3 to identify basophils and expression of CD63 to identify activation enhanced assay adds third marker CD203c Some oddities: Adds anti-cd63 antibody at the same time as cells are stimulated

16 Basophil activation assay CD63 and CD203c expression differs in response to IL3 priming In commercial kits, IL3 is often used to increase sensitivity but it blunts CD203c response Needs to be processed within 4 hours (then basophil reactivity starts to decline) Anti-FceRI antibodies and fmlp (Formyl-Met-Leu-Phe) are used as positive controls, stimulation buffer alone is the negative control

17 Principle of Basophil activation testing

18 Histaflow Measures Histamine release an enzyme-affinity-gold method based on the high affinity of diamine oxidase (DAO) for its substrate histamine Effectively couples DAO to a fluorochrome which then binds histamine Histamine release can be measured by flow-cytometry in combination with phenotypic analysis D.Ebo et al.,journal of Immunological Methods 375 (2012)

19 Basophil testing - food allergy

20 Common food triggers Whilst 90% of food allergic reactions are caused by the foods below, any food may cause an allergic reaction 1.7

21 Basophil activation distinguishes peanut allergic from tolerant patients BAT correctly diagnosed 89% of patients 96.7% if non-responders to positive control were excluded 2-step strategy (either SPT or Ara h2 sige then BAT if required) correctly diagnosed 95% of patients (Santos AF et al JACI 2014;134:645-52)

22 Peanut allergy severity associated with basophil reactivity Santos AF JACI 2015;135:179-86

23 Basophil activation is specific for egg and peanut allergic patients Egg allergic subjects (Ovalbumin) Peanut allergic subjects Impact of study population egg white sige >0.35kUL: sensitivity 93.5%, specificity 92.5% (Ocmant et al. Clin Exp Allergy 2009, Vol. 39, 8)

24 BAT in food allergy Distinguish degree of cow s milk reactivity- Ford LS et al JACI :180-6 Diagnose subtypes of wheat dependent exercise induced anaphylaxis- Chinuki et al JACI :1404-6

25 Summary-BAT in food allergy Performs well for selected food allergens in experienced hands Low up front cost, existing expertise Limited clinical utility if sige Fits a niche Broadly sensitised patients Population cohorts in place of OFC Serial monitoring in immunotherapy Note: has also been evaluated for venom allergy

26 Basophil testing - drug allergy

27 Classification of drug HR Drug hypersensitivity reactions (DHRs) are heterogeneous! Clinically, DHRs can be classified as: 1. Immediate DHRs (BAT is helpful here) urticaria, angioedema, rhinitis, conjunctivitis, bronchospasm, gastrointestinal symptoms (nausea, vomiting, diarrhea, abdominal pain), anaphylaxis, anaphylactic shock; they typically occur within 1 6 h after the last drug administration.

28 Classification of drug HR 2. Non-immediate DHRs (BAT will be negative) varying clinical picture (often involve the skin) Spectrum of disease with varying pathogenesis (Type II to IV cell reactions) they may occur at any time as from 1 h after from the initial drug administration (this often depends on exposure history)

29 Considerations: Drugs as Immunogens Biologics: foreign macromolecules (e.g. antibodies, recombinant proteins) that act directly as immunogen Drugs (non-biologics) Hapten/protein/drug complex (e.g. beta-lactam antibiotics, quinidine) Pro-hapten-processed drug combines with a host macromolecule (e.g. sulfonamides, phenytoin) Pharmacological interaction with an immune receptor (p-i TCR or p-i HLA; e.g. Abacavir)

30 Drug preparation Requires cytotoxicity assessment and dose dependent testing to determine optimal concentrations Several commercial reagents are available, but expensive

31 Allergy to NSAIDs and Aspirin Results for BAT testing inconclusive May be only useful for severe reactions Poor sensitivity even when CD203c is included into the assay Reactivity is dose-dependent and likely influenced by the fact that Prostaglandin E2, a natural inhibitor of basophils, is inhibited by COX-1 inhibitors HSA conjugated drugs have been used and shown to work in some case reports but not others, e.g. severe diclofenac HSR

32 Allergy to Radiocontrast Media Heterogenous group (IgE and non-ige mediated) Four studies Sensitivity 46.2% to 61.5%; specificity 88.4% to 100% Correlation with skin testing less strong (complementary role in testing?)

33 Allergy to Fluoroquinolone Antibiotics Ciprofloxacin, moxifloxacin, norfloxacin etc. Skin tests are limited due to their skin-irritation properties (88% false + rate in intradermal testing) Seven studies Sensitivity ranges between 0-100% depending on study Role of CD203c versus CD63 Specificity in all studies high (over 88%), therefore excellent negative predictive value for drug provocation testing

34 Allergy to Beta-lactam antibiotics 9 studies Sensitivities ranged from 28.6 to 55% (closer to 50% in larger studies) Specificity over 90% Can be positive even when the skin testing is negative May be adapted to a wider range of beta lactam antibiotics (e.g. cephalosporins)

35 Allergy to Neuromuscular blocking agents Seven clinical trials Sensitivity ranges from 36.1 to 91.7% Heterogenous studies (inclusion criteria, drugs tested) In those with clearly proven NMBA anaphylaxis, sensitivity was 36.1% which increased to 85.7% when tested within 3 years High correlation to skin testing, but more sensitive and specific

36 Allergy to Anti-neoplastic agents and others Multiple case reports Biologic agents Anti-neoplastic agents Other drugs: corticosteroids, anti-histamines, gelofusine, heparin, chlorhexidine, pholcodine etc

37 Conclusions BAT drug allergy Advantages In-vitro testing, safe Functional test that resembles the in-vivo pathway Relatively good sensitivity with high specificity Allows testing of drugs for which no skin testing is available Disadvantages Performance depends on type of allergen, drugs may need to be haptenated

38 Questions?