Can we eliminate important bacterial pathogens with protein- based vaccines? Engineered antigens derived from bacterial transferrin receptors

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1 Can we eliminate important bacterial pathogens with protein- based vaccines? Engineered antigens derived from bacterial transferrin receptors Dr. Tony Schryvers (University of Calgary) Vaccine Innovation Conference May 26, 2015

2 Host- Restricted Upper Respiratory Tract Pathogens Common Features highly host- adapted & host specific URT only reservoir transmission by respiratory route are naturally transformable horizontal gene transfer contributes to genetic and antigenic variation challenge to develop a broadly protective vaccines Gram- Negative Species Neisseria meningitidis Haemophilus influenzae Moraxella catarrhalis Gram- Positive Species Streptococcus pneumoniae - Responsible for 20-25% of deaths < 5 yrs - Cause of most common bacterial infection

3 Bacterial Respiratory Tract Pathogens S. pneumoniae N. meningitidis M. catarrhalis H. influenzae Non-Invasive Sinusitis Invasive Responsible for a spectrum of invasive and non- invasive infections Colonization precedes infection nontypeable Ear Infection Meningitis type b Pneumonia Bacteria causing invasive infection possess polysaccharide capsule Pneumonia Sepsis type b nontypeable type b

4 Conjugate Capsular Vaccines Reduce Infection by Targeted Serotypes Type b H. influenzae (UK) vaccine S. pneumoniae PCV7 7 serotypes (Calgary) Vaccine serotypes

5 Conjugate Capsular Vaccines Designed to prevent invasive infection Studies demonstrate that systemic vaccination results in: elimination of targeted serotypes from mucosal carriage disease reduction in non-vaccinated populations 60 Invasive Disease Adults > 65 Carriage % Children vaccine types 45 20% 15% 10% 5% 0% Spring '03 Spring '04 Spring '05 12 months 18 months 4.5 years All Serotypes PCV7 Serotypes

6 Conjugate Capsular Vaccines Highly specific immunity reduction in carriage by vaccine serotypes coupled with increase in non-vaccine serotypes Calgary CASPER 20% % Children vaccine types 20% % Children non- vaccine types 15% 15% 10% 10% 5% 5% 0% Spring '03 Fall '03 Spring '04 Fall '04 Spring '05 Fall '05 0% Spring '03 Spring '04 Spring '05 12 months 18 months 4.5 years 12 months 18 months 4.5 years

7 Conjugate Capsular Vaccines Highly specific immunity - reduction in disease by vaccine serotypes coupled with increase in nonvaccine serotypes vaccine 300 Unknown Non-Vaccine Preve Other Vaccine Prev 19A PCV7 225 Canada IMPACT

8 Conjugate Capsular Vaccines PROS Effective reduction in disease by strains expressing targeted polysaccharide capsules Reduction in colonization led to decreased transmission and reduction in disease in non- immunized (herd effect) CONS Not effective against other capsular types may result in disease by other types (capsule switching) Not effective for non- immunogenic capsular types (group B meningococci) Development of broadly cross- protective vaccines may need to target protein antigens

9 Iron Homeostasis: Role of Transferrin (Tf) Tf shuttles iron within body to cells requiring iron (Fe) Tf is normally only partially saturated Tf keeps the level of free Fe below that needed for growth of pathogens Tf is a critical source of iron during invasive infection There is limited information regarding iron homeostasis on mucosal surfaces Tf known to be critical iron source on the mucosl surface for some bacteria (Neisseria gonorrhoeae, Actinobacillus pleuropneumoniae)

10 Bacterial Transferrin Receptors Human Neisseria meningitidis meningitis, sepsis Neisseria gonorrhoeae Haemophilus influenzae Haemophilus influenzae (NT) Moraxella catarrhalis gonorrhea meningitis, sepsis otitis media, COPD, pneumonia otitis media, COPD, pneumonia Cattle Sheep Goat Mannheimia haemolytica BRD (shipping fever) Pasteurella multocida Histophilus somni Moraxella bovis Pasteurella trehalosi BRD BRD, invasive disease pinkeye sepsis / RD Pig Actinobaccilus pleuropneumoniae pneumonia Haemophilus parasuis Glasser s disease (invasive disease & pneumonia) Actinobacillus suis sepsis, hemorrhagic/embolic lesions of lung

11 Receptor- mediated iron acquisition from transferrin (Tf) Surface lipoprotein,tbpb (transferrin binding protein B) captures Fe loaded Tf Tf TbpB transfers Fe- Tf to TbpA, an integral outer membrane protein TbpA removes Fe from Tf and transports Fe across the outer membrane TbpA TbpB FbpA (ferric binding protein A) shuttles iron to inner membrane complex FbpBC inner membrane complex transports Fe into the cell FbpA TonB FbpB/C Fe ExbB ExbD

12 TbpB Vaccines A Brief History 1990: patent on Tf/Lf receptors filed Meningococcal Vaccines: 1990 Pasteur Merieux (currently Sanofi Aventis) licensed Tbps native TbpB shown to be immunogenic and protective in mice/rabbits, 3 TbpB variants provide broad coverage 1998 human Phase I clinical trial (w/o adjuvant) - disappointing results 2001 license abandoned Animal Vaccines: recombinant proteins tested directly in pigs and cattle Key Relevant Research Findings: human gonococcal and pig experiments demonstrate Tbps critical for survival and disease : noncompete clause, insufficient funding 2008: AHFMR Team Grant & sabbatical, structure- based vaccine design

13 TbpB Vaccines - Rationale for Structure-based Antigen Hypotheses: Engineering Approach host Tf binds to TbpB during systemic immunization & interferes with development of optimal protective response explains poor performance in Phase I trial & only moderate success for animal vaccines solution: design non- Tf binding antigens TbpBs bind to same region of Tf requiring conserved binding interface, antigenic variation involves immunodominant decoy B- cell epitopes solution: engineer antigens with enhanced ability to induce cross- protective immune response remove decoy epitopes and preserve conserved binding interface

14 TbpB Structure (porcine pathogen - A. pleuropneumoniae) barrel Trevor Moraes N- lobe handle anchor peptide N- lobe barrel C- lobe handle barrel barrel C- lobe

15 Site- Directed Mutants Single mutations designed to reduce/eliminate Tf binding. Panel A: Targeted residues Panels B G: Superposed mutant and wild- type structures Mutations had no effect on overall structure

16 Site- Directed Mutants Single mutation results in dramatic loss in Tf binding Affinity binding constants for wild-type and mutant TbpBs Protein Mutation Loop Kd Method ApH49 TbpB WT 55 nm ITC ApH49 TbpB F171A L8 NDB ITC ApH49 TbpB WT 44 nm SPR ApH49 TbpB F171A L8 TBD SPR ApH87 TbpB WT 60 nm SPR ApH87 TbpB Y95A L3 585 nm SPR ApH87 TbpB Y121A L5 203 nm SPR ApH87 TbpB Y174A L8 8.9 um SPR ApH87 TbpB R179E L8 6.1 um SPR AsH57 TbpB WT 120 nm SPR AsH57 TbpB F63A L1 326 nm SPR AsH57 TbpB F152A L5 495 nm SPR Hp5TbpB WT 21 nm BLI Hp5TbpB Y93A L3 TBD BLI Hp5TbpB Y117A L5 TBD BLI Hp5 TbpB Y167A L8 40uM BLI (e4535) Hp5 TbpB W176A L8 TBD BLI Hp5 TbpB Y167A, L8 NDB BLI (e4597) W176A TBD To Be Determined NDB No Detectable Binding ITC isothermal titration calorimetry SPR surface plasmon resonances BLI biolayer interferometry

17 Transferrin Receptor- based Vaccine Survival: Clinical Symptoms: % Survival Mutant TbpB Native TbpB Porcillis Glasser Control Days of Survival Mild or no symptoms or pathology Moderate to severe symptoms and pathology Hours after challenge Control Native TbpB Mutant TbpB Porcillis Glasser Engineered mutant TbpB is a superior antigen

18 Colonization of Humanized Transgenic Mice Scott Gray- Owen A uninfected infected B wildtype CEACAM1 huceacam1 N. meningitidis DAPI

19 Men C Conjugate Vaccine Prevents Colonization TbpB and TbpB C- lobe Prevents Colonization

20 Prevention of Colonization is not a Common Feature of Protein Antigens Invasive disease challenge with H44/76 FHbp match 3 day colonization challenge with H44/76 FHbp match Factor H binding protein protects against sepsis but not colonization Percent survival Adjuvant Bexsero CFU per animal detection limit Time (h) Bexsero Adjuvant PorA protects against sepsis but not colonization. Percent survival Invasive disease challenge with SK016 PorA match Adjuvant Bexsero CFU per animal detection limit 3 day colonization challenge with SK016 PorA match Time (h) Bexsero Adjuvant Invasive disease challenge with S3446 NHBA match 3 day colonization challenge withs3446 NHBA match NHBA partially protects against sepsis but not colonization Percent survival Adjuvant Bexsero CFU per animal detection limit Time (h) Bexsero Adjuvant NadA protects against sepsis and colonization Percent survival Invasive disease challege with BuFa 02/03 NadA match Adjuvant Bexsero CFU per animal 3 day colonization challenge with BuFa 02/03 AP group W, NadA match detection limit Time (h) Bexsero Adjuvant

21 Engineered TbpB Vaccines Advantages: Tf receptors are essential for survival on the mucosal surface (N. gonorrhoeae, A. pleuropneumoniae) Engineered TbpB antigens are superior in inducing a protective immune response in the native host (H. parasuis challenge experiments) TbpB (and TbpB C- lobe) are capable of preventing colonization in a humanized mouse model (unlike antigens from commercial vaccines) Surrogate host- pathogen systems can provide proof of concept Question: Could a TbpB- based vaccine be used eradicate receptor- containing bacteria?

22 Porcine Pathogen TbpBs Sequence Diversity of TbpBs from Porcine Pathogens TbpB diversity transcends species barriers single vaccine for the three porcine pathogens. Phylogenetic groups defined by structural features and interaction with Tf Cross- reactivity analysis predicts small number of engineered antigens required for broad cross- protection.

23 Immunization Experiments in Pigs N- lobe induces more Group/strain specific antibody response. - Group 3 - Group 3 - Group 2 - Group 1 C- lobe induces broadly cross- reactive immune response. Predicts that three representative mutant TbpBs would be capable of inducing a broadly cross- reactive and cross- protective response. From Strain H49

24 Meningococcal Vaccine - Sequence/Structural Diversity Comprehensive evaluation of sequence diversity intact TbpB & C-lobe. Intact TbpB Diversity Two TbpB isotypes (Group 1 vs Group 2-4). Two antigens selected for immunization experiments (circled in red) Representative variants selected for analysis of cross-reactivity (arrows). C- lobe Diversity Paul Adamiak

25 Sequence Diversity Evaluation of Cross- reactivity Immunization with TbpBs or C- lobes provides reactivity against diverse representative TbpBs. Antigen: Jamie Fegan Tbp Strain

26 TbpB-based Meningococcal Vaccine Can we eliminate important pathogens? TbpB present in some commensal Neisseria sp. and in N. gonorrhoeae - potential reservoir for vaccine escape overall diversity of Neisseria TbpBs modestly greater than meningococcal TbpBs (i.e. limited number of engineered TbpBs/C- lobes required) commensal Neisseria with and without TbpB are similar, unlikely to be dependent upon TbpB for iron (eliminating TbpB won t eliminate commensal Neisseria) require systematic approach for evaluating ability to induce complete cross- protection - integrated vaccine evaluation pipeline

27 Integrated Vaccine Evaluation Pipeline Structural studies Global collection of disease isolates Bioinformatics analysis of antigen diversity URT microbiome Cloning & Expression (SG) Engineered antigen Library of antigenic variants serum immunize + - ELISA Assay generate strain library Bacterial killing (SBA) strain library Challenge humanized mice

28 Commercialization US Provisional Patent Applications Dec, 2013 June, 2014 October, 2014 PCT Patent Application Dec 2014 Exploring Partnerships/Licensing Agreements

29 Meningococcal Transferrin and Lactoferrin Receptors in Colonization, Infection and Disease Prevention ALMA Alberta Livestock and Meat Agency Ltd. Development of a Broad- Spectrum Porcine Vaccine for Bacterial Respiratory Infections Genome Alberta ALMA Disease Reduction in Cattle by Elimination of Colonization by Pathogens University of Passo Fundo (Brazil) Rafael Frandoloso University of Leon (Spain) Cesar Gutierrez- Martin Elias Ferri- Rodriguez Sonia Martinez- Martinez