What is persistence? David R. Sherman, PhD The Union 21 st Conference North American Region February 25, 2017

Transcription

1 What is persistence? David R. Sherman, PhD The Union 21 st Conference North American Region February 25, 2017

2 What is persistence? firm or obstinate continuance in a course of action in spite of difficulty or opposition. the continued or prolonged existence of something.

3 What is persistence? Congressman John Lewis

4 What is persistence? Congressman John Lewis, civil rights hero.

5 Tuberculosis globally 16 million active TB infections 1.4 million TB deaths 1.8 billion PPD(+) Latent TB 5 billion PPD(-)

6 TB disease progression 5% Transmission ACTIVE infection 10 M / Yr DEATH 1.4 M / Yr 95% 5% LATENT infection 1.8 B globally CURE

7 TB persistence: The ability of MTB to survive in vivo despite immunity or chemotherapy.

8 TB persistence: The ability of MTB to survive in vivo despite immunity or chemotherapy. TB latency: infection in the absence of disease.

9 TB persistence: The ability of MTB to survive in vivo despite immunity or chemotherapy. TB latency: infection in the absence of disease. 1.4 million TB deaths 1.8 billion PPD(+) 16 million active TB infections Latent TB 5 billion PPD(-)

10 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic.

11 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic. TB bacilli (latent) = TB bacilli (active).

12 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic. TB bacilli (latent) = TB bacilli (active). During latency, the bacteria are dormant:

13 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic. TB bacilli (latent) = TB bacilli (active). During latency, the bacteria are dormant: Metabolically inactive?

14 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic. TB bacilli (latent) = TB bacilli (active). During latency, the bacteria are dormant: Metabolically inactive? Non-replicating

15 Assumptions about TB persistence Reactivation is a major driver of the TB pandemic. TB bacilli (latent) = TB bacilli (active). During latency, the bacteria are dormant: Metabolically inactive? Non-replicating Conditions: hypoxia, starvation, acid ph.

16 Reactivation is a major driver of the TB pandemic. Risk of TB disease following infection Progressive? Reactivation Depends on: Age at infection Current age Geography (host factors?) Strain? Avg. time to symptoms = 1.4 yrs Emilia Vynnycky and Paul E. M. Fine

17 Reactivation is a major driver of the TB pandemic. How important is reactivation TB?

18 Reactivation is a major driver of the TB pandemic. How important is reactivation TB?

19 Reactivation is a major driver of the TB pandemic. How important is reactivation TB? ~30,000 S. African gold miners. Very high TB rate (~2%). Widespread INH prophylaxis (IPT) for 6+ months.

20 Reactivation is a major driver of the TB pandemic. How important is reactivation TB? ~30,000 S. African gold miners. Very high TB rate (~2%). Widespread INH prophylaxis (IPT) for 6+ months. Conclusions Mass screening and treatment for latent tuberculosis had no significant effect on tuberculosis control.

21 During latency, the bacteria are dormant.

22 During latency, the bacteria are dormant. What s the evidence?

23 During latency, the bacteria are dormant. Conditions associated with latency: Condition Hypoxa Low ph Carbon shift (lipids) MTB response DosR; Enduring hypoxic response (EHR) Acid response genes KstR; cholesterol uptake and metabolism All these conditions promote bacteriostasis in vitro, and all occur in vivo.

24 During latency, the bacteria are dormant. Conditions associated with latency: Condition Hypoxia Low ph Carbon shift (lipids) MTB response DosR; Enduring hypoxic response (EHR) Acid response genes KstR; cholesterol uptake and metabolism All these conditions promote bacteriostasis in vitro, and all occur in vivo. However, they also occur during active disease!

25 During latency, the bacteria are dormant. Are bacteria non-replicating in latency? TB never stops replicating in mice (Nat Med. 2009;15:211).

26 During latency, the bacteria are dormant. Are bacteria non-replicating in latency? TB never stops replicating in mice (Nat Med. 2009;15:211). In primates, TB acquires as many mutations in latency as in active disease (Nat Genet. 2011;43:482).

27 During latency, the bacteria are dormant. Are bacteria non-replicating in latency? TB never stops replicating in mice (Nat Med. 2009;15:211). In primates, TB acquires as many mutations in latency as in active disease (Nat Genet. 2011;43:482). INH prophylaxis in humans.

28 During latency, the bacteria are dormant. Now what?

29 New tools provide new ideas about persistence: Systems biology: sequencing transcriptomics modeling PET/CT imaging.

30 PET/CT imaging of TB in primates Probe: 18 FDG Seen in active and latent TB; also in humans. Lin et al, Nature Medicine, 20, (2014)

31 Active and latent TB overlap Primate lesions Lin et al, Nature Medicine, 20, (2014)

32 Active and latent TB overlap Primate lesions Lin et al, Nature Medicine, 20, (2014)

33 Active and latent TB overlap Primate lesions Lin et al, Nature Medicine, 20, (2014)

34 The spectrum of TB disease

35 Persistence and TB chemotherapy Std Rx: 4 drugs, 6 months, ~95% cure rate. But

36 Persistence and TB chemotherapy Std Rx: 4 drugs, 6 months, ~95% cure rate. But Relapse Am Rev Respir Dis 130: , 1984

37 Persistence and TB chemotherapy Std Rx: 4 drugs, 6 months, ~95% cure rate. But 70% were cured in 2 months! Am Rev Respir Dis 130: , 1984

38 Bi-phasic kill kinetics in vivo. INH treatment of TB-infected mice Dhar and McKinney, Current Opinion in Microbiology Volume 10, Issue 1, 2007, 30 38

39 Bi-phasic kill kinetics in vivo. INH treatment of TB-infected mice Drug tolerance: the ability to survive in the face of otherwise inhibitory or lethal drug concentrations. Bacilli remain drug-sensitive! Dhar and McKinney, Current Opinion in Microbiology Volume 10, Issue 1, 2007, 30 38

40 Condition-specific MTB drug tolerance Slow/no-growth: environment (hypoxia, acid, starvation, immunity) toxin/anti-toxin modules biofilms Growing cells: efflux pumps differential enzyme activation detoxification

41 Condition-specific MTB drug tolerance Slow/no-growth: environment (hypoxia, acid, starvation, immunity) toxin/anti-toxin modules biofilms Growing cells: efflux pumps differential enzyme activation detoxification Heterogeneity.stochastic.bet-hedging

42 The problem with averages Dhar and McKinney, Current Opinion in Microbiology Volume 10, Issue 1, 2007, 30 38

43 Quantifying replication & cell death in Analysis at single-cell resolution response to antibiotic insult Untreated Rifampin Isoniazid

44 Can we deal with MTB heterogeneity? Systems biology: genetics gene expression metabolism modeling Prediction: BDQ hyper-sensitivity

45 Can we deal with MTB heterogeneity? Systems biology: genetics gene expression metabolism modeling Prediction: BDQ hyper-sensitivity Prediction validated! Select drug synergies..

46 Conclusions Little evidence supports older ideas of TB dormancy. Recent evidence suggests a TB disease spectrum. Heterogeneity underlies TB persistence New hope for tackling TB! ID those most at risk of active disease. latency treatments should also shorten therapy. drug synergies.

47 Thank you!

48 REMEMBER Thank you!

49 The spectrum of tuberculosis Nat Rev Microbiol. 2009; 7:845

50 Latent TB..sub-clinical TB active disease Time (months to years) Phil. Trans. R. Soc. B 369:

51 Implications of the TB spectrum model Not everyone is equally at risk for active disease. Sub-clinical disease should leave a different molecular signature. TB bacilli (latent) is similar to TB bacilli (active). Similar treatments may work!