# Mechanisms of Innate Immune Evasion by Mycobacterium Tuberculosis

> **NIH NIH R01** · WASHINGTON UNIVERSITY · 2022 · $660,713

## Abstract

SUMMARY
The goal of this project is to understand how two virulence factors from Mycobacterium tuberculosis (Mtb), CpsA
and phthiocerol dimycocerosate (PDIM), impair immunity by undermining both classical and non-classical
autophagy. Mtb is the causative agent of tuberculosis (TB), the leading cause of death worldwide from a bacterial
infection. The main cellular niche for Mtb is macrophages and neutrophils, the very immune cells that are meant
to clear infection. How Mtb survives the innate immune response to establish infection is not well understood. In
the previous project period, we discovered that an exported protein, CpsA, is critically important for Mtb virulence.
We showed that CpsA inhibits phagosomal recruitment of the NADPH oxidase. The NADPH oxidase makes
reactive oxygen species (ROS), an important mediator of the innate immune response. In addition to its direct
antimicrobial activity, ROS is required for a lysosomal trafficking pathway called LC3-associated phagocytosis
(LAP), a non-classical form of autophagy. Thus, by inhibiting ROS, CpsA also inhibits LAP. We showed both in
macrophages and mice that CpsA protects Mtb from the NADPH oxidase and LAP. Interestingly, CpsA physically
interacts NDP52 and TAX1BP1, autophagy adaptors that function in a form of classical autophagy (xenophagy),
suggesting that CpsA may also impair xenophagy. Moreover, we found that the Mtb virulence lipid, PDIM, also
inhibits the NADPH oxidase. Previous studies proposed an array of roles for PDIM and showed that it protects
Mtb from a poorly defined innate killing mechanism. Our data suggest that an unappreciated virulence property
of PDIM is blocking the NADPH oxidase and LAP. Thus, we hypothesize that CpsA inhibits xenophagy and
works in concert with PDIM to inhibit the NADPH oxidase and LAP. Further, we propose that the infectious dose
of Mtb depends upon its ability to evade these innate defenses in myeloid cells that are recruited to the lungs
during initial infection. Here, we will define how CpsA inhibits the NADPH oxidase and investigate whether it also
impairs xenophagy by blocking NDP52 and TAX1BP1 function. We will determine whether PDIM also impairs
recruitment of the NADPH oxidase to mycobacterial phagosomes and evaluate the contribution that PDIM plays
towards subverting the NADPH oxidase and LAP in vivo. To determine whether CpsA promotes the
establishment of infection, we will use an ultra-low dose infection model in mice. Using conditional knockout
(cKO) mice, we will determine in which cells CpsA functions to inhibit the NADPH oxidase and LAP during acute
and chronic infection. Our findings will provide mechanistic insight into how two key virulence factors in Mtb
collaborate to undermine immunity. Our studies will reveal a cell type-specific virulence strategy of the bacilli,
delineate the cell types that participate in LAP in vivo, and define host-pathogen interactions that govern the
establishment of infection. Our studies will provid...

## Key facts

- **NIH application ID:** 10390674
- **Project number:** 2R01AI130454-06
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** JENNIFER A PHILIPS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $660,713
- **Award type:** 2
- **Project period:** 2017-01-01 → 2026-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10390674

## Citation

> US National Institutes of Health, RePORTER application 10390674, Mechanisms of Innate Immune Evasion by Mycobacterium Tuberculosis (2R01AI130454-06). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10390674. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*