Peanut Allergy Immunotherapy The Development of a Modified Protein Vaccine

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Goals and Objectives • • • • • Establish importance of peanut allergy Review historical approaches Outline NIAID immunotherapy priorities Revisit important discoveries Discuss plans for basic science immunotherapy research Peanut allergy is a common, serious & growing problem • Affects an estimated 0.6% of US adults • Prevalence in children has doubled between 1997-2002 • Only 20% develop “tolerance” & can relapse • > 50% patients will react to an accidental exposure every 2-5y • Accounts for > 80% of the 100-200 annual fatalities from food-related anaphylaxis • Greatly affects patient & family QOL Initial Interventions Subcutaneous immunotherapy with peanut extract attempted in 1992 & ‘97 • One placebo patient died after receiving peanut extract in a pharmacy error • Systemic reactions were very frequent, often severe & in many cases required decrease in dose • Efficacious in those who could tolerate maintenance dosing “Treatment” failures JACI 2001; 107: 191-93 Exciting Developments • • • • • Anti-IgE ISS/CpG adjuvants Traditional Chinese medicine Recombinant protein immunotherapy Oral peanut desensitization www.ars.usda.gov/sp2UserFiles/Program/108/Sawyer42706.USDA.slides.final.pdf www.ars.usda.gov/sp2UserFiles/Program/108/Sawyer42706.USDA.slides.final.pdf www.ars.usda.gov/sp2UserFiles/Program/108/Sawyer42706.USDA.slides.final.pdf www.ars.usda.gov/sp2UserFiles/Program/108/Sawyer42706.USDA.slides.final.pdf Ideal Properties of Peanut Immunotherapy 1. 2. 3. 4. 5. Safe Effective in treating established allergy Easy to administer Cost-effective Long duration of action Food Allergen Characteristics • Proteins or glycoproteins < 70 kD • Soluble in aqueous solutions • Generally resistant to denaturation by acid, proteases, & heat • Abundant in food source • Epitopes can be linear or conformational JACI 2004; 113(5)809-19 Ara h 1 Arachis hypogaea Peanut allergens are seed storage proteins Ara h 1 Identified & cloned by Burks et. al. in 1991 • > 600 AA / 63.5kD protein • 3 Ara h 1 monomers bound by hydrophobic regions to form stable homo-trimer • 23 IgE binding epitopes Eight peanut allergens identified in all • Ara h 1, 2, & 3 identified, sequenced & cloned • > 95% pts sensitive to Ara h 1 & 2; 45% to 3 • Epitope binding diversity does exist in humans JACI 1991: 88(2)1729. Ara h 1 J Biol Chem 1998:273(22) 13753-59 J Biol Chem 1998:273(22) 13753-59 Ara can be mutated to prevent IgE interactions • Overlapping peptide segments generated • Probed with human sera to identify immunodominant epitopes Arch Biochem Biophys 1997 (342)2: 244-53 Single AA substitutions in Ara prevent IgE interactions Arch Biochem Biophys 1997, 342(2): 244-52 JACI 2000 (106) 150-8 To Review So Far: • A major group of seed storage proteins are allergenic, binding IgE with high affinity & causing severe anaphylaxis • Major immunodominant epitopes are shared by the majority of patients • cDNA point mutations change a single AA residue & abrogates human IgE binding • A mouse model approximates the allergic sensitization and reaction seen in humans • Listeria expresses several PAMPs which activate APCs and NK cells – Lipotechoic acid : TLR2 – Flagellin : TLR5 – CpG : TLR9 • • • MyD88 -/- susceptible to Listeria HKLM in mice augments IL-10, IL-12, IL-18, & IFN-γ production and decreases IgE synthesis This group showed that using Listeria as an adjuvant during immunization converted the TH2 response to a TH1 response J Immunol 1998 (161) 4146-52 • Use of an HKLM adjuvant with ovalbumin in a mouse model of asthma: – reversed already established airway hyperreactivity & inflammation/eosinophilia – reduced ova-specific IgE and increased ova-specific IgG2a – reduced IL-4 levels and increased IFN-γ. • anti IL-12 mAb neutralized the effect J Immunol 2000 (164): 223-30 Allergy 2005 (60) 243-50 In sensitized C3H/HeJ mice, LMP-123: • reduced anaphylaxis symptom scores, plasma histamine, and airway obstruction • ⇓ peanut-specific IgE & ⇑ IgG2a • Downregulated TH2 cytokines & upregulated IFN-γ but did not change IL-10 J Immunol 2003 (170) 3289-95 In a BALB/c OVA asthma model: • Antigen-specific T regs were induced by DCs primed with HKLM • CD25- TR expressed Foxp3, IL-10 & T-bet • Suppressed TH2 responses & AHR Nat Immunol 2004: 5(11) 1149-56 Could E.coli act as an adjuvant similar to Listeria? • Recombinant peanut protein produced in an E.coli system • E.coli expresses PAMPs, is a commensal, and may act as an adjuvant like Listeria • EMP-123 suppressed anaphylaxis in mice when given IN, SC or PR but not IG • Significant skin inflammation was noted at SC injection sites JACI 2003 (112) 159-67 EMP-123 study design JACI 2003 (112) 159-67 All doses of EMP-123 suppress anaphylaxis 2 weeks after treatment JACI 2003 (112) 159-67 A dose-dependent effect becomes evident at 6 weeks after treatment JACI 2003 (112) 159-67 The 90 mcg dose continues to show efficacy 10 weeks after last dose JACI 2003 (112) 159-67 All 3 doses suppress peanut-specific IgE, and high dose increases IgG2a JACI 2003 (112) 159-67 Cytokine profile shifts from TH2 to TH1 and TGF-β is upregulated JACI 2003 (112) 159-67 Conclusions • High-dose rectal immunotherapy with heatkilled E.coli expressing a modified recombinant major peanut protein construct: – Is safe in animals – Reverses established peanut allergy & protects sensitized mice from anaphylaxis for at least 10 weeks – Is associated with reduction in peanut-specific IgE, plasma histamine, and TH2 cytokine levels, and upregulation of IFN-γ and TGF-β JACI 2003 (112): 159-67 Research Questions • How does the vaccine work? – Epithelium / GALT in antigen uptake & processing – Role of DCs & their TLRs in TH1 v TH2 responses – Antigen specificity (“tolerance”) vs. global suppression (regulatory T cells) • Which vaccine components are necessary & sufficient for effective immunization? • Is another route of administration possible? • Will it work in humans? ? ? Adapted from Chehade JACI 2005; 115(1):3-12 Immunol Rev 2005 (206) 204-18 Summary • Peanut allergy is a common, severe, lifelong problem • Avoidance is an ineffective “treatment” • COFAR will address novel food allergy immunotherapeutic strategies • Recombinant mutated peanut protein in heatkilled E.coli vector is safe & effective in mice and may prove useful in humans QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.