Cambier, C. J. | Search bioRxiv

bioRxiv2020

Towards Mycobacterium tuberculosis detection at the point-of-care: a brighter solvatochromic probe permits the detection of mycobacteria within minutes

There is an urgent need for point-of-care tuberculosis (TB) diagnostic methods that are fast, inexpensive, and operationally simple. Here, we report on a bright solvatochromic dye trehalose conjugate that specifically detects Mycobacterium tuberculosis (Mtb) in minutes. 3-hydroxychromone (3HC) dyes, known to yield high fluorescence quantum yields, exhibit shifts in fluorescence intensity in response to changes in environmental polarity. We synthesized two analogs of 3HC-trehalose conjugates (3HC-2-Tre and 3HC-3-Tre) and determined that 3HC-3-Tre has exceptionally favorable properties for Mtb detection. 3HC-3-Tre-labeled mycobacterial cells displayed a 10-fold increase in fluorescence intensity compared to our previously reports on the dye 4,4-N,N-dimethylaminonapthalimide (DMN-Tre). Excitingly, we detected fluorescent Mtb cells within 10 minutes of probe treatment. Thus, 3HC-3-Tre permits rapid visualization of mycobacteria that ultimately could empower improved Mtb detection at the point-of-care in low-resource settings.

microbiology↗

bioRxiv2017

Phenolic glycolipid facilitates mycobacterial escape from a microbicidal population of tissue-resident macrophages

Mycobacterium tuberculosis enters the host in aerosol droplets deposited in lung alveoli where the bacteria first encounter lung-resident alveolar macrophages. We studied the earliest mycobacterium-macrophage interactions in the optically transparent zebrafish. We find that the first-responding resident macrophages can phagocytose and eradicate infecting mycobacteria. So, to establish a successful infection, mycobacteria must escape out of the initial resident macrophage into growth-permissive monocytes. We define a critical role for the membrane phenolic glycolipid (PGL) in engineering this transition to a permissive niche. PGL activates the STING cytosolic sensing pathway, thereby inducing the chemokine CCL2 that recruits permissive peripheral monocytes. The bacteria then transfer from resident macrophage to recruited monocyte via transient fusion of the two immune cells. We show that interrupting this bacterial strategy so as to prolong the mycobacterial sojourn in resident macrophages promotes clearing of infection. Because PGL-dependent CCL2 induction is conserved in human alveolar macrophages, our findings suggest the potential of immunological or pharmacological PGL-blocking interventions to prevent tuberculosis.

immunology↗