Role of subclinical TB: Can we model prevention of TB in the subclinical stages? Paul K. Drain, MD, MPH Depts. of Global Health, Medicine, Epidemiology Tuberculosis Research & Training Center University of Washington, Seattle September 12, 2018
DISCLOSURE The following speaker has reported a relevant financial relationship with a potential commercial interest: - Gilead Sciences - Abbott/Alere - L.E.K. Consulting - Salus Discovery
Pathophysiologic Perspective
Clinical Perspective Drain PK, 2018.
Defining Incipient and Subclinical TB Subclinical TB Disease Disease due to viable Mtb that does not cause clinical TBrelated symptoms but does cause other abnormalities that can be detected using existing radiologic or microbiologic assays. Incipient TB Infection Infection with viable Mtb that is likely to progress to active disease in the absence of further intervention, but has not yet induced clinical symptoms, radiographic abnormalities, or microbiologic evidence consistent with active TB disease. Drain PK. Clinical Micro Reviews, 2018.
Infection to Disease to Outcome
Incipient TB Other Immune Correlates - Higher IGRA-conversion value greater risk of TB progression (in infants) CORTIS Trial Prospective clinical trial to evaluate gene signature Providing 3HP Following for >=2 years Clinical sites in South Africa - Th17-type CD4 + T cell responses may be associated with lower risk of TB progression
Subclinical TB Diagnose may require non-sputum assays Urinary LAM assay Detect subclinical TB in 25% (7/28) of HIV-infected ambulatory patients in South Africa* Studies of 2 nd gen LAM assays starting soon Presence of IL-2 cytokine-secreting CD4 + T cells indicates presence of greater bacillary burden and clinical disease * Bajema K, et al. BMC ID, under review.
WHO Endorsements and Uptake of New TB Diagnostics 1. Line Probe Assay (LPA) Nov 2015 - for TB smear+ (direct) or TB cultured (indirect) isolates May 2016 - includes LPA for second-line drugs (by Hain Lifesciences) Mostly Hain Lifesciences (Germany) and NIPRO Corp. (Japan) 2. GeneXpert MTB/RIF Assay March 2017 - recommended Ultra MTB/RIF as non-inferior to Xpert MTB/RIF By 2018, ~35 million cartridges used in 122 countries since 2011 Widely used at centralized district levels; Evidence for impact? 3. Urine LF-LAM Assay Nov 2015 - only for HIV+ with CD4 <100 and/or seriously ill In 2017, only 2 countries (Uganda, South Africa) had plans or purchase orders Alere (now Abbott) discussing shutting down production (due to low demand) 4. TB-LAMP (loop mediated amplification) May replace sputum smear at microscopy center Only for patients with signs/symptoms consistent with pulmonary TB Very low quality of evidence; Available since 2016, but minimal uptake
Pipeline for New TB Diagnostics Tests for TB Exposure ctb skin testing (includes ESAT-6 and CFP10) QuantiFeron TB-Gold Plus (CD4 & CD8 T cells) Screening and Triage Digital readers of chest X-rays Volatile Organic Compounds (breath test) Immune response-based screening (CRP, ESR, IP-10, IL-6, IFN-gamma, IL-17, etc.) Second-gen. urine LF-LAM assays Tests for Disease Progression PET-CT scan for disease progression Host RNA transcriptional signature Diagnostic Tests for Active TB Upcoming NAATs by Alere/Abbott (Alere q); QuantuMDx (Q-POC); Tosoh Bioscience (TRCReady) Many different in house PCR assays available Next-gen whole genome sequencing with ReSeqTB database Biomarker Discovery Detection of T-cell signaling New lipid biomarkers Serologies of TB Antigens (ex. Ag85B) Enzymatic detection of TB-specific beta-lactamase Metabolomics, Lipidomics, Transcriptomics, etc.
A more fundamental problem TB Symptom Screening (overall) ~ 75% sensitivity ~ 40% specificity Sympt. Screen for HIV+ pre-art ~ 50-70% sensitivity ~ 50% specificity Sympt. Screen for HIV+ on ART ~ 25% sensitivity ~ 90% specificity leads to miss/delays in TB diagnosis and ART initiation FIND, 2017; Getahun 2011; Rangaka 2012
Health System Perspective Existing TB Tests World Health Organization, 2015.
Priority Research/Modeling Questions for Subclinical TB Pathogenesis and Immune Response What triggers/prevents progression from incipient or subclinical to active TB disease? How do different strains of Mtb alter proliferation and progression to active TB? Can the immune system be harnessed to stop Mtb in the incipient or subclinical stage? Epidemiology How does the prevalence of incipient and subclinical TB vary across populations? Are there host genetic factors that may increase the risk of incipient or subclinical TB? Clinical Course and Transmissibility How common is a waxing/waning picture of adults with subclinical and active TB? What are the risk factors for progression of disease through incipient and subclinical TB? How transmissible is TB in the subclinical disease stage? Should contacts of a patient with subclinical be evaluated for TB? Screening and Diagnostic Approach What are the optimal screening and diagnostics tests for subclinical TB? What is the recommended screening frequency for either in high-tb burden regions? Treatment and Prevention Should incipient TB be treated? which regimen? And, for how long? Should subclinical TB be treated with mono-therapy, 4-drug therapy, or new combination?
Mathematical Modeling Approach Population-level impact of 2 nd gen. urine LAM assay in high-burden settings Stratified by CD4 count, HIV status, and smear positivity Urine LAM alone and in combination TB Symptom Gene Xpert TB Symptom Urine LAM Gene Xpert TB Symptom Urine LAM Chest X-Ray Urine LAM Gene Xpert CRP Urine LAM Gene Xpert CRP Urine LAM
Sample Testing Algorithm in the Model
Conclusions - Diagnostic Priorities for Subclinical TB 1. POC objective Screening Test for Level 0 and 1 2. POC non-sputum Diagnostic Test for Incipient/Subclinical TB 3. Biomarker of TB treatment (HIV viral load equivalent) 4. Test for TB Cure 5. Better (more tailored) Diagnostic Algorithms
Conclusion - Learn from Success of HIV 1. Clinical and validations studies for diagnosis and treatment of incipient and/or subclinical TB. 2. Identification and validation of non-sputum based biomarkers for (1) treatment response and (2) cure.
Acknowledgements University of Washington: Connie Celum Jared Baeten Ruanne Barnabas Tom Hawn Ann Duerr King Holmes Joanne Stekler Jonathan Posner Barry Lutz Funding Support: Collaborators in South Africa: Yunus Moosa, UKZN Nigel Garrett, CAPRISA Kogie Naidoo, CAPRISA Slim Abdool-Karim, CAPRISA Doug Wilson, UKZN/Edendale Hospital Collaborators in Thailand: Tim Cressey, Chiang Mai University Virat Klinbuayaem, Sanpatong Hospital Oraphan Siriprakaisil, Sanpatong Hospital Ratchada Cressey, Chiang Mai University Collaborators in U.S.: Mehmet Toner, MGH/Harvard Monica Gandhi, UCSF Jim Gallarda, Gates F. David Boyle, PATH
Tuberculosis Over 10 million new infections worldwide each year Leading infectious disease cause of death globally Diagnostic Success for HIV/AIDS 1. Accurate POC Diagnostic Assay 2. Test of Treatment Response (viral load) 3. Mobilize for Mass Screening Campaigns 4. An Agenda for a Test of Cure Better Diagnostic Tools & Optimized Usage WHO, Stop TB Partnership, 2018.