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Recognition of the Mtb-infected Cell: What IGRAS Have Allowed Us To Understand About TB David Lewinsohn, MD, PhD Pulmonary & Critical Care Medicine Portland.

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Presentation on theme: "Recognition of the Mtb-infected Cell: What IGRAS Have Allowed Us To Understand About TB David Lewinsohn, MD, PhD Pulmonary & Critical Care Medicine Portland."— Presentation transcript:

1 Recognition of the Mtb-infected Cell: What IGRAS Have Allowed Us To Understand About TB David Lewinsohn, MD, PhD Pulmonary & Critical Care Medicine Portland VA Medical Center Oregon Health & Sciences University The Royal Society SATELLITE MEETING ON Human evolution – plagues, pathogens and selection


3 TB Diagnostics: Opportunities for Impact TB Disease –Case Finding Improved detection of bacterial products –LED / NAAT / Urine Dipstick / Novel Plasma or Urine Markers Rapid identification of drug resistance –Line Probe / Cepheid Improved understanding of immune markers of antigenic load Identification of markers of active infection –Treatment Tools to identify those at risk for treatment failure “Latent” TB Infection – Identify those at risk for progression Improved understanding of bacterial persistence Improved understanding of immune markers of antigenic load

4 Abu-Raddad L J et al. PNAS 2009;106:13980-13985 ©2009 by National Academy of Sciences IncidenceMortality

5 The Testing Strategy Should be Matched to Benefit TST ≥ 10 mm TST ≥ 15 mm TST ≥ 5 mm

6 The TST Immune Phenotype Rieder, Epidemiologic Basis of TB Control, IUTLD (1999)  Risk highest shortly after infection  Late disease might reflect re-exposures  TST poor at identifying those at risk Acute TB Infection Persistent TB Infection

7 Outcome of contact evaluations ARPES, 2001; S+ Reichler, 1996; all Marks, 1998; S+ close Contacts Evaluated55-81% of contacts complete TST LTBI dx’d22-36% found newly infected Start TLTBI63-74% begin treatment Complete Rx51-62% finish treatment Outcome~17-37% of target population actually complete TLTBI Courtesy Andy Vernon, CDC

8 Lesson 1: David vs Goliath TST –Associated with Exposure to Mtb –Conversion associated with risk of disease –Treatment of benefit

9 IGRAs Peter Andersen, SSI Winner 2011 Novo Nordisk Prize Steve Reed, IDRI

10 The Immune Phenotype: Beyond TST

11 Lesson 1: We Can do At Least as Well as the TST “ Professional ” Antigen Presenting Cell CD4 Lymphocyte Protein Peptide 12-18 AA CD4 TCR Class II MHC IFN-  TNF ESAT-6 CFP-10 QuantiferonIFN-γ ELISA CD4 T-SPOTIFN-γ ELISPOT CD4 / CD8

12 IGRAs and The Diagnosis of LTBI Test Accuracy –What is the Sensitivity of the test with regard to TB? –What is the Specificity in those unlikely to have been exposed? –What is the Likelihood of infection in those being tested? Association with Conditions Linked to Treatment Success –Is the test associated with exposure to Mtb? –Is the test associated with progression to TB? Are there other risks / benefits that might affect the decision as to which test to use? –Test logistics –Client and provider perceptions –Cost Is treatment based on the test associated with improved outcomes? –More accurate identification of those at risk? –Do more patients accept or complete treatment based on the test results?

13 Test Accuracy –Sensitivity Active TB* QFT-IT84% (81,86) TSPOT93% (90,95) TST77% (71,82) –Association with Exposure Both QFT and TSPOT are more closely associated with exposure than TST. * Courtesy Madhu Pai, High prevalence countries

14 Test Accuracy –Specificity* QFT-IT99% (98,100) TSPOT85-98% TST –BCG49% (46,73) –No BCG97% (95,99) * Courtesy Madhu Pai, High prevalence countries

15 Progression to TB – Diel R et al. Predictive value of a whole blood IFN-gamma assay for the development of active tuberculosis disease after recent infection with Mycobacterium tuberculosis. Am J Respir Crit Care Med. 2008. 601 household contacts 40.4% (243/601) TST + 11% (66/601( (11%) QFT+ Six contacts progressed to TB disease within the 2-year follow-up. All were QFT positive and had declined preventive treatment, equating to a progression rate of 14.6% (6/41) among those who were QFT positive. –Kik et al. Predictive value for progression to tuberculosis by IGRA and TST in immigrant contacts. Eur Respir J. 2009. 339 TST+ household contacts (5mm); prophylaxis not given 9/288=3.1% (95% CI; 1.3-5.0) for TST ≥10 5/178=2.8% (95% CI; 1.0-4.6) for QFTGIT (54% QFT+; 5/8 cases detected) 6/181=3.3% (95% CI; 1.3-5.3) for T-SPOT.TB (63% TSPOT +; 6/8 cases detected) Review of TB case reporting did not find cases in those who were TST-

16 High Risk Populations Heterogeneous Population Very Limited Data in High Income Settings TSPOT May be Less Affected by Low CD4 Counts Immunosupression is Associated with Impaired Test Performance for Cellular Assays Sensitivity Active TB in HIV* –QFT-IT / TSPOT84% (65,100) –TST43% (25,85) * Courtesy John Metcalfe Association with Progression to TB –Aichelburg et al., Clin Infect Dis. 2009 Apr 1;48(7):954-62. –830 HIV+ subjects –44 QFT+ –8 found to have TB at time of testing –7QFT+ –1 QFT – –3/37 QFT+ developed TB during follow up

17 Low Risk Populations –Not candidates for Rx –Specificity of IGRAs may be superior to TST, particularly in those with a history of BCG vaccination. Khoury et al., JOEM, 2011

18 Lesson 2: There is nothing Latent about LTBI

19 IGRAs Reflect a Dynamic Relationship of the Host, the Microbe, and the Environment The Host –Vulnerability to infection –Infection / disease status The Microbe –Strain –Metabolic activity Environment –Likelihood of exposure / re-exposure –Other mycobacteria –Other infections

20 TST Variability Menzies, AJRCCM 1999 –6mm represents 2SD in repeated TST measurements –TST reversions Following INH therapy among those recently exposed on a submarine –Houk et al., 1968. Arch. Environ. Health 16:46–50 Estimated 8% in exposed children Estimated 8% annually in older adults

21 Do IGRAs Reflect Bacterial Burden? Metcalfe et al., AJRCCM 2009 –660 TB suspects in San Francisco –Increased IFN-γ associated with increased likelihood of TB Kobashi et al., Lung 2010 Hinks et al., Infection and Immunity 2009

22 Are IGRAs a Reflection of the Environment and/or Host? Detjen et al., Clinical Vaccine Immunology 2009 Ringshausen et al, Clinical and Vaccine Immunology 2011

23 Transient Exposure? Friedman et al., Infect Control Hosp Epidemiol 2006 –45 % HCW previously positive by TST were negative on repeat testing –Best correlation with persistent TST positivity Foreign birth BCG TST > 15mm –Best correlation with TST reversion Working in study clinic

24 Transient Exposure? Ewer al al., Am J Respir Crit Care Med Vol 174. pp 831–839, 2006

25 Transient Exposure Natural exposure of guinea pigs to MDR/XDR –75% of the 362 exposed guinea pigs had positive skin test reactions [6 mm]. –12% had histopathologic evidence of active disease. –Reversions (6mm change) in skin test reactivity were seen in 22% of animals, exclusively among those with reactions of 6-13 mm. –2of 86 guinea pigs with reversion had histological evidence of disease vs 47% (31/66) of guinea pigs with large, non-reverting reactions. –Immunosuppression had no effect

26 Can IGRAs Discern Recent from Remote Exposures? Millington et al., JID 2010 –27 subjects with self- healed, untreated TB –>50 years –17 + Ex-vivo ELISPOT (16 IFN-γ ) –6/10 + long term assay Recent vs Remote –Hinks et al., I&I 2009 –Kik et al., IJTLD 2009

27 Cellular Immunology: CD4 Cells “ Professional ” Antigen Presenting Cell CD4 Lymphocyte Protein Peptide 12-18 AA CD4 TCR Class II MHC IFN-  TNF Cytotoxicity Cytokines

28 How Do We Explain the Variability Seen in Longitudinal Testing? Assumptions –ELISA/ELISPOT have inherent variability (10-15%) –There is a learning curve when IGRAs are introduced van Zyl-Smit et al., AJRCCM, 2009 Ringshausen et al., BMC Infect Dis 2010

29 Lesson 3: We Need Better Surrogates of Bacterial Burden


31 Novel T Cell Phenotypes Adapted from Seder et al., Nat Rev Immunol, 2008



34 The Host: Sampling the Intracellular Environment All Cells CD8 Lymphocyte Peptide 9-11AA CD8 TCR Class I MHC IFN-  TNF Cytotoxicity Cytokines Cytoplasmic Protein  2m

35 ESAT-6 / CFP-10 Responses During TB Treatment CD4 ResponseCD8 Response

36 BMI Has a Profound Effect on the CD4 Response CD4 ResponseCD8 Response BMI ≤ 17BMI > 17BMI ≤ 17BMI > 17 * p = 0.02

37 Conclusions IGRAs perform at least as well as TST in those who might benefit from therapy. Quantitatively, IGRAs likely a reflection of persistent and variable Mtb-antigen. Improved surrogates of bacterial / disease burden are likely needed.

38 Acknowledgements Portland VA Medical Center Melanie HarriffErvina Winata Lynne SwarbrickSue Smyk-Pearson Marielle GoldJoel Weekley OHSU Liz Canfield Deborah LewinsohnMelissa Nyendak Megan NullKatelynne Garner-Toren Amanda DuncanMeghan Cansler Veena RajaramanShannon McWeeney Tomi MoriByung Park Todd VogtGuanming Wu Collaborators Henry BoomCWRU Denise JohnsonCWRU Keith ChervenakCWRU Dave ShermanUniversity of Washington Karen DobosColorado State University John BelisleColorado State University Lisa WolfColorado State University Henry BoomCase Western Reserve University Roy MugerwaMakerere University Harriett MyanjaMakerere University Sarah KiguliMakerere University Dennis DobbsTBRU Sarah ZalwangoMakerere University Mary Nsereko TBRU Payam NahidUCSF Alesandro SetteThe La Jolla Institute for Allergy and Immunology John AltmanEmory University Special thanks to: Aeras Sean Bennett Bruce McClain Jerry Sadoff Donata Sizemore John Fulkerson David Hokey Tom Evans NIH Christine Sizemore Alison Deckhut Timothy Gondre-Lewis OHSU Lynne Swarbrick Amanda Duncan Melissa Nyendak Melissa Kumagi Phyllis Carello Lynne Swarbrick Ervina Winata


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