An Automated Culture System for Use in Preclinical Testing of Host-Directed Therapies for Tuberculosis

Executive Industry Relevance

This protocol enables rapid, automated quantification of intracellular Mycobacterium tuberculosis growth in macrophages, addressing a key bottleneck in host-directed therapy (HDT) screening. By reducing time-to-results from 21+ days to 5-12 days and minimizing labor-intensive CFU counting, it supports efficient repurposing of FDA-approved drugs as adjunctive TB treatments. The method enhances predictive confidence in preclinical HDT evaluation and accelerates go/no-go decisions in anti-infective discovery pipelines.

Strategic Applications in Biopharma R&D

Early Discovery & Target Validation

• Scientific Value: Enables mechanistic de-risking of host-directed therapies by quantifying intracellular Mtb inhibition under physiologically relevant conditions.
• Operational Value: Provides reproducible, quantitative readouts (time to positivity) that support target validation and pathway modulation assessment.

Screening & Assay Development

• Scientific Value: Delivers standardized, broth-based colorimetric detection compatible with automated microbial monitoring systems for high-throughput feasibility.
• Operational Value: Reduces hands-on time and technical variability compared to agar-based CFU assays, improving assay robustness for drug screening campaigns.

Translational & Preclinical Research

• Scientific Value: Bridges discovery and preclinical evaluation by generating correlative data with gold-standard CFU counts, supporting translational continuity.
• Operational Value: Enables dose-response and combination therapy testing (e.g., AtRA ± PLGA, linezolid + interferon-gamma) within a physiologically relevant macrophage infection model.

Pipeline & Workflow Integration

The method fits within the early discovery to lead identification continuum, enabling rapid assessment of host-directed mechanisms before advancing to in vivo efficacy studies.

• Discovery Biology: Supports hypothesis testing of immune-modulating compounds by measuring their impact on intracellular pathogen survival.
• Screening: Generates quantitative, time-resolved growth inhibition data suitable for prioritizing compounds in repurposing screens.
• Analytics: Delivers time-to-positivity (TTP) metrics that inversely correlate with bacterial load, enabling statistical comparison across treatment conditions.
• Translational Research: Maintains biological relevance through use of human-derived THP-1 macrophages and clinically pertinent HDT candidates.
• Enterprise Reuse: Establishes a standardized, automatable platform applicable to multiple HDT candidates and intracellular pathogen models.

Operational & Enterprise Impact

• Scientific Value: Increases predictive confidence in HDT efficacy by providing mechanistically aligned, quantitative intracellular growth data.
• Operational Value: Enhances throughput and reproducibility through automation, reducing dependency on manual CFU plating and interpretation.
• Strategic Value: Improves capital efficiency by accelerating identification of viable host-directed candidates for preclinical investment.
• Portfolio Impact: Enables risk-adjusted prioritization of HDTs based on reproducible, dose-responsive inhibition of intracellular Mtb growth.

Implementation Considerations

• Requires familiarity with biosafety level 3-equivalent practices for handling mycobacterial cultures and macrophage infection workflows.
• Dependent on access to automated microbial detection systems capable of monitoring broth culture positivity (e.g., MGIT or similar platforms).
• Necessitates standardization of MOI determination and lysis protocols across sites to ensure comparability of TTP readings.
• Involves optimization of drug solubility and stability in broth medium, particularly for lipophilic compounds like all-trans retinoic acid.
• Limited to pathogens detectable via liquid culture broth systems; not applicable to non-culturable or fastidious organisms without system adaptation.

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