# An imaging approach to understanding the impact of heterogeneity in microenvironments and lesion properties during Mycobacterium tuberculosis infection

> **NIH NIH R21** · TUFTS UNIVERSITY BOSTON · 2020 · $204,950

## Abstract

PROJECT SUMMARY/ABSTRACT
 Mycobacterium tuberculosis (Mtb) infects one-third of the human population and causes ~1.7 million
deaths a year, broadly impacting population and economic development. Current therapy requires a prolonged
time-course of 6-9 months, making patient compliance difficult, and exacerbating the problem of drug-resistant
strains. A critical factor in the prolonged therapy required is thought to be heterogeneity in microenvironments
and bacterial and lesion properties during infection, but little is known about what drives this heterogeneity, and
how it affects colonization and disease progression. Our long-term hypothesis is that the heterogeneous
lesions, microenvironments and bacterial responses are regulated and not just stochastic, providing points for
therapeutic intervention. The inability to understand this process thus constitutes a critical block that must be
overcome for continued progress in the field. Bulk assays do not provide a means to study this phenomenon,
and the technical difficulties associated with studying heterogeneity during whole animal infection has been a
significant barrier to progress. This project seeks to overcome these hurdles by first developing an imaging
strategy to enable analysis of Mtb-host interactions at the single bacterium level, in the context of intact 3-
dimensional host tissue architecture. To accomplish this, tissue optical clearing methods and innovative
fluorescent reporter Mtb strains that allow direct readout of a bacterium’s replication status and aspects of its
local environment will be used, together with a murine infection model that exhibits the full range of granuloma
types observed during human infection. This integrated imaging strategy will then be utilized to (i) establish a
framework delineating key lesion and host cell properties conducive for Mtb growth, and (ii) elucidate the
impact of non-uniform microenvironments on Mtb replication and lesion properties in vivo, and test how
modulation of Mtb response to environmental signals impacts infection heterogeneity and outcome. The latter
aim will focus on the response of Mtb to chloride and potassium, two novel and important cues for Mtb during
infection that represent possible Achilles’ heels that can be targeted to shift the balance of infection.
Mechanistic understanding of heterogeneity in microenvironments and lesion properties is critical for defining
the molecular and cellular basis of how Mtb interfaces with its host, vital for the development of better
therapies. Further, the development of a framework for understanding Mtb-host interactions represents a rich
source for hypothesis generation for the long-term goal of understanding the host and bacterial determinants
that influence heterogeneity, and how these elements control Mtb colonization, disease progression, and
treatment. The concept of heterogeneous environments and its impact on host-pathogen interactions is
increasingly being appreciated, with studi...

## Key facts

- **NIH application ID:** 9820240
- **Project number:** 5R21AI137759-02
- **Recipient organization:** TUFTS UNIVERSITY BOSTON
- **Principal Investigator:** Shumin Tan
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $204,950
- **Award type:** 5
- **Project period:** 2018-11-08 → 2021-10-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9820240

## Citation

> US National Institutes of Health, RePORTER application 9820240, An imaging approach to understanding the impact of heterogeneity in microenvironments and lesion properties during Mycobacterium tuberculosis infection (5R21AI137759-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9820240. Licensed CC0.

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