Презентация на тему In vitro Diagnosis of Drug Allergy: Current Status and Perspectives

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proteins) act directly as immunogen
Drugs (non-biologics)
Hapten – drug (e.g.

β-lactam antibiotics, quinidine) combines with a host macromolecule
Pro-hapten – processed drug (e.g. sulfonamides, phenytoin) combines with a host macromolecule
Drugs can act directly to stimulate an immune receptor (pharmacologic interaction with immune receptors = p-i concept)

in the setting of an immediate drug reaction
Testing in

the setting of a delayed drug reaction
Testing on the horizon

reaction that occurs rapidly upon exposure to a specific

drug
Standard approach to evaluate is immediate skin testing (penicillin major and minor determinants are validated, other drugs ?)
In vitro methods of evaluation include:
Tryptase to establish mast cell degranulation
Allergen (drug) specific IgE testing
Basophil activation test (BAT)

is elevated in a systemic allergic reaction
Current laboratory test

most widely available measure total tryptase (not mature tryptase)
Released within 30-60 minutes following activation and half life is ~2 hours allows longer “testing window”
Levels above normal range (vary among labs: 10-11.4 ng/mL) are consistent with anaphylaxis (or increased mast cell numbers) but the sensitivity is not high
More sensitive test for anaphylaxis: mature tryptase level or a total tryptase rise over baseline of > 2 ng/mL

skin testing
Does not subject patient to risk and does

not have a potential of inducing sensitization
Limited range of drugs available impacts utility: β-lactams (penicilloyl G & V, ampicilloyl, amoxocilloyl), ACTH, cefator, ceftriazone, chlorhexidene, ethylene oxide, gelatin, insulin, neuromuscular blocking agents, tetanus toxoid)
Tests generally have high specificity with lower sensitivity - negative test does not rule out allergy

whole blood or separated mononuclear cells
Validated for aeroallergens, hymenoptera

venoms, foods, latex, some drugs (generally based on a generated drug-protein complex)
Commercial assay (not FDA approved in USA): uses expression of CCR3 to identify basophils and expression of CD63 to identify activation after incubating cells the with drug complex
“Enhanced assay” adds a third marker, CD203c

Exp 2011



Gating “lymphocytes” Gating basophils

Negative control

Drug-HSA Negative control Positive control

Positive control: 52.5% CD63+, SI - 5501/386 = 14.2

Positive drug BAT: 20.6% CD63+; SI - 1893/386 = 4.9

risks
Functional test that resembles the in vivo pathway
Relatively good

sensitivity with high specificity
Positive BAT depends on type of allergen
Aeroallergens/foods >15% CD63+ basophils
Venoms >10% CD63+ basophils
Drugs (β-lactams, analgesics) >5% CD63+ basophils
Disadvantages
Must have viable, non-activated cells (24 hr “window”)
More limited availability since it requires a flow cytometer and generation of drug-protein (hapten-carrier) complex
Negative test does not rule out drug allergy

with history of immediate radiocontrast media (RCM) reactions: BAT

using five different RCM products (tested months later)
BAT results: 15/26 patients had a positive BAT
1:100 RCM: patients = 13.1% CD63+/SI=8.1 (p=0.01)
controls = 2.7% CD63+/SI=1.5
1:10 RCM: patients = 19.2% CD63+/SI=9.0 (p=0.001)
controls = 3.7% CD63+/SI=2.3
Receiver Operator Curve (ROC) area under the curve was 0.79 = test with moderate accuracy

Pinnobphun P, et al. Ann Allergy Asthma Immunol 2011, 106:387

cellular response (Gell and Coombs Type IV reaction involving

T cells)
These reactions have been subdivided into
Type IVa: mediated by Th1 response
Type IVb: mediated by Th2 response
Type IVc: mediated by cytotoxic cell response
Type IVd: mediated by neutrophilic inflammation
Additional data now suggests that some reactions involve conventional TcR activation (e.g. where there is an HLA link) and others involve direct drug-immune receptor interaction (p-i concept)

clinical findings are the result of an immunologic response

(rather than a pharmacologic or idiosyncratic response)
Identify the causative drug in settings where multiple drugs have been administered
Current testing methods
Lymphocyte transformation test (LTT)
CD69 upregulation flow cytometry test
Cytokine production
Evaluation of cytotoxicity (or its products)

with 5% CO2








Peripheral blood mono-nuclear cells (PBMC)
I- Activation in

vitro

II- Quantify Response

Harvest cells and count radioactivity, results: cpm or stimulation index (SI = drug stimulated cpm/unstimulated cpm)

PBMC

PBMC

Cells

Lymphocyte Transformation Test (LTT)

Add 3H thymidine

T cell

T cell

6 days

lack of drug induced toxicity and to rule out

non-specific activation
Must have viable cells and requires sterile tissue culture
LTT has been successfully applied to drug associated:
Maculopapular exanthem
Pustular exanthem
Stevens Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN)
Drug rash with eosinophilia and systemic symptoms (DRESS)
Positive LTT has generally been defined as a stimulation index (SI = cpm with drug/cpm with medium) > 2
Sensitivity is 60-70% under optimal conditions with a higher specificity
Negative test does not rule out T cell mediated drug response

Hypersensitivity Drug Reactions
27 patients in three groups: 8 maculopapular

eruptions (MP), 6 SJS + 2 TEN, 11 DRESS
Evaluated by LTT at 1 week, 2-4 weeks, 5-8 weeks, 1 year and > 1 year following onset
Patients with MP and SJS/TEN had positive LTT at 1 week post-onset, response declined over time
Patients with DRESS were negative at 1 week and were positive at 5-8 weeks

Kano Y, et al. Allergy 2007, 62:1439

DRESS
Two patients receiving multiple drugs including anticonvulsants and antibiotics

associated with the development of DRESS
Evaluation by LTT utilized all drugs that had been given, each at 7 concentrations (1-200 μg/ml)
Studied 3 months after the clinical presentation
Causative drug was identified as ceftriaxone in one pt and piperacillin-tazobactam in the other pt
LTT assay proved valuable in defining the drug associated with DRESS (avoid in the future)

Jurado-Palomo J, et al. J Investig Allergol Clin Immunol 2010, 20:433

to other testing in delayed drug reactions
Time line of

positivity may differ between the different types of delayed drug reactions
Positive test helps identify the offending drug but a negative test does not rule out drug related hypersensitivity
The test remains a research tool, it is not standardized and it requires tissue culture with results available after six or more days

a T cell activation antigen in response to in

vitro drug exposure
CD69 up-regulation, an early product of T cell activation, measured by flow cytometry at 48 hrs
Ex vivo cytokine production
Cytokine secretion into the supernatant following mononuclear cell culture with drug (e.g. γ-IFN)
Elispot assay measures individual T cell production of a cytokine following in vitro drug stimulation

with 5% CO2






PBMC
I- Activation in vitro
II- Quantify Response


PBMC
PBMC



Evaluate T

cells by flow cytometry

CD69 upregulation expressed as percent CD69 positive T cells

T cell CD69 Upregulation

T cell

CD69

48 hours

phenytoin-allergic patient following 48 hrs of stimulation
medium -

negative control

Lochmatter P, et al. Immunol Allergy Clin N Am 2009, 29:537

Tetanus toxoid - positive control

Phenytoin - positive test

Unrelated drug clonazapam –
negative test

similar to LTT with the advantage of being a

48 hour assay and not requiring radionuclides
Cytokine production assays correspond to LTT but the actual cytokine produced does not appear to correlate well with the clinical phenotype (i.e. IFN-γ is typically produced with all types of delayed drug reactions)

drugs appear to be linked to cytotoxic T cell

activity

sFasL

Porebski G, et al. Clin Exp Allergy 2011, 41:461

Soluble Fas ligand (sFasL) and granulysin have been found in the serum of patients with SJS/TEN

of granulysin is ~100X greater than sFasL in SJS/TEN

making it an attractive target
An immunochromagraphic test for serum granulysin (>10 ng/mL) predicted SJS/TEN 2-4 days prior to mucocutaneous reuptions
This assay could prove useful in predicting when a drug reaction will lead to SJS/TEN

Fujita Y, et al. J Am Acad Dermatol 2011, 65:65

culture (e.g. IFN-γ, IL-2, IL-4, IL-5, IL-8, IL-13, IL-17,

etc) may reveal specifics about the type of immune response
Nature of drug derived epitopes inducing an immune reaction often are not well understood
Mass spectrometry (MS) has evolved as a powerful tool to evaluate proteomics and metabolomics
MS used to characterize the functional antigens derived from piperacillin (in CF patient serum) with the identification of multiple drug derived haptenic structures bound to albumin (Whitaker P, et al. J Immunol 2011, 187:200)

drug reactions
Specific IgE testing: safe test but there are

limited numbers of suitable drug conjugates available for testing
BAT: promising functional test that requires viable cells and a drug conjugate preparation for activation
Delayed drug reactions
Lymphocyte transformation test (LTT)
Most common research method to determine responsible drug
Issues remaining include: standardization, requirement for viable cells, six day sterile tissue culture period and use of radionuclides
CD69 upregulation may be equivalent to LTT – under study
In vitro cytokine production to drug – under study
Product of cytotoxic cells (granulysin) promising to help dx SJS/TEN prior to mucocutaneous symptoms (further study)

point evaluating possible drug allergy
In vitro testing can be

complementary to in vivo testing and is evolving for the evaluation of both immediate and delayed drug allergy
There is currently no single laboratory test that reliably establishes the drug responsible for an immunologically mediated drug reaction