# The lipid language of tuberculosis: Mycobacterium tuberculosis surface molecules in host interaction and drug resistance

## TL;DR

This paper explores how Mycobacterium tuberculosis uses lipids to interact with the host, evade the immune system, and resist drugs, offering insights into new treatment strategies.

## Contribution

The paper provides a comprehensive review of the diverse roles of Mtb lipids in host interaction and drug resistance, highlighting recent advances and challenges.

## Key findings

- Mtb lipids modulate host immune pathways and facilitate intracellular survival by altering phagosome maturation and autophagy.
- Lipids like PDIM and TDM promote granuloma formation and pathological features critical for TB transmission.
- The lipid envelope acts as a barrier to antibiotics, with resistance linked to altered lipid composition in drug-resistant strains.

## Abstract

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a uniquely successful pathogen due in large part to its complex lipid-rich cell envelope. Comprising nearly 40% of its dry weight, Mtb lipids—such as mycolic acids, phthiocerol dimycocerosates (PDIM), trehalose dimycolate (TDM), and sulfolipids (SLs)—play crucial roles in infection, immune evasion, intracellular persistence, granuloma formation, transmission, and drug resistance. These lipids modulate host-pathogen interactions by altering host membrane biophysics, hijacking phagosome maturation, and interfering with host immune pathways, including autophagy and inflammatory signaling. Upon inhalation, Mtb surface lipids inhibit pulmonary surfactant function and mask pathogen-associated molecular patterns, facilitating uptake by permissive macrophage subsets. Intracellularly, lipoglycans like mannose-capped lipoarabinomannan block phagolysosome fusion, while PDIM and TDM promote phagosomal escape and subversion of vesicular trafficking. Lipid-mediated modulation of autophagy pathways further enhances bacterial survival within host cells. In addition to shaping host immune responses, Mtb lipids orchestrate granuloma development and promote pathological features such as foam cell formation and caseation, which are central to transmission. Specifically, phenolic glycolipids and SLs stimulate neuronal pathways, triggering cough, thereby facilitating aerosol spread. Finally, the lipid-rich envelope acts as a formidable barrier to antibiotics, with resistance partly driven by the altered lipid composition and architecture in multidrug-resistant strains. Targeting lipid biosynthesis and transport pathways offers promising avenues for novel anti-TB therapies. This review highlights the multifaceted roles of Mtb lipids at the host-pathogen interface, recent technical advances enabling these insights, and emerging challenges in translating lipid biology into improved TB control.