David R. Sherman, PhD The Union

21st Conference North American Region

February 25, 2017

What is persistence?

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.

What is persistence?

Congressman John Lewis

What is persistence?

Congressman John Lewis, civil rights hero.

1.4 million TB deaths

5 billion PPD(-)

1.8 billion PPD(+)

16 million active

TB infections

Tuberculosis globally

Latent TB

TB disease progression

Transmission ACTIVE infection

10 M / Yr

5%

95%

LATENT infection

1.8 B globally

DEATH

1.4 M / Yr

CURE

5%

TB persistence:

The ability of MTB to survive

in vivo despite immunity

or chemotherapy.

TB persistence:

The ability of MTB to survive

in vivo despite immunity

or chemotherapy.

TB latency: infection in the

absence of disease.

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

5 billion PPD(-)

1.8 billion PPD(+)

16 million active

TB infections

Latent TB

Assumptions about TB persistence

• Reactivation is a major driver of the TB pandemic.

Assumptions about TB persistence

• Reactivation is a major driver of the TB pandemic.

• TB bacilli (latent) = TB bacilli (active).

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:

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?

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

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.

Risk of TB disease following infection

Emilia Vynnycky and

Paul E. M. Fine

Depends on:

Age at infection

Current age

Geography (host factors?)

Strain?

Progressive

?

Reactivation

Avg. time to symptoms = 1.4 yrs

“Reactivation is a major driver of the TB pandemic.”

How important is reactivation TB?

“Reactivation is a major driver of the TB pandemic.”

How important is reactivation TB?

“Reactivation is a major driver of the TB pandemic.”

How important is reactivation TB?

“Reactivation is a major driver of the TB pandemic.”

~30,000 S. African gold miners.

Very high TB rate (~2%).

Widespread INH prophylaxis (IPT) for 6+ months.

How important is reactivation TB?

“Reactivation is a major driver of the TB pandemic.”

~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….”

“During latency, the bacteria are dormant.”

What’s the evidence?

“During latency, the bacteria are dormant.”

“During latency, the bacteria are dormant.”

Conditions associated with latency:

Condition MTB response

Hypoxa DosR; Enduring hypoxic response

(EHR)

Low pH Acid response genes

Carbon shift (lipids) KstR; cholesterol uptake and

metabolism

All these conditions promote bacteriostasis in vitro,

and all occur in vivo.

“During latency, the bacteria are dormant.”

Conditions associated with latency:

Condition MTB response

Hypoxia DosR; Enduring hypoxic response

(EHR)

Low pH Acid response genes

Carbon shift (lipids) KstR; cholesterol uptake and

metabolism

All these conditions promote bacteriostasis in vitro,

and all occur in vivo.

However, they also occur during active disease!

“During latency, the bacteria are dormant.”

Are bacteria non-replicating in latency?

• TB never stops replicating in mice (Nat Med. 2009;15:211).

“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).

“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.

“During latency, the bacteria are dormant.”

Now what?

New tools provide new ideas about persistence:

Systems biology: sequencing transcriptomics modeling PET/CT imaging.

PET/CT imaging of TB in primates

Lin et al, Nature Medicine, 20, 75–79 (2014)

Seen in active and latent TB; also in humans.

Probe: 18FDG

Active and latent TB overlap

Lin et al, Nature Medicine, 20, 75–79 (2014)

Primate lesions

Active and latent TB overlap

Lin et al, Nature Medicine, 20, 75–79 (2014)

Primate lesions

Active and latent TB overlap

Lin et al, Nature Medicine, 20, 75–79 (2014)

Primate lesions

The spectrum of TB disease

Persistence and TB chemotherapy

Std Rx: 4 drugs, 6 months, ~95% cure rate. But………

Persistence and TB chemotherapy

Std Rx: 4 drugs, 6 months, ~95% cure rate. But………

Am Rev Respir Dis 130: 23-28., 1984

Relapse

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: 23-28., 1984

Dhar and McKinney, Current Opinion in Microbiology Volume 10, Issue 1, 2007, 30–38

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

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!

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

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

Dhar and McKinney, Current Opinion in Microbiology Volume 10, Issue 1, 2007, 30–38

The problem with averages

Quantifying replication & cell death in response to antibiotic insult

Rifampin Isoniazid Untreated

Analysis at single-cell resolution

Can we deal with MTB heterogeneity?

Prediction: BDQ hyper-sensitivity

Systems biology: genetics gene expression metabolism modeling

Can we deal with MTB heterogeneity?

Prediction: BDQ hyper-sensitivity

Systems biology: genetics gene expression metabolism modeling Select drug synergies…..

Prediction validated!

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.

Thank you!

REMEMBER

Thank you!

The spectrum of tuberculosis

Nat Rev Microbiol. 2009; 7:845

Time (months to years)

Latent TB…..sub-clinical TB……active disease

Phil. Trans. R. Soc. B 369: 20130437.

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!