During a new study, researchers paved the way for new vaccine strategies against tuberculosis, and provided insights into fighting other infectious diseases around the world by analyzing how individual immune cells react to the bacterium that causes this deadly disease.
The cutting-edge technologies were developed in the lab of Dr. David Russell, the William Kaplan Professor of Infection Biology in the Department of Microbiology and Immunology in the College of Veterinary Medicine, and detailed in new research published in the Journal of Experimental Medicine on July 22.
For years, Russell’s lab has sought to unravel how Mycobacterium tuberculosis (Mtb), the bacteria that cause tuberculosis, infect and persist in their host cells, which are typically immune cells called macrophages.
The lab’s latest innovation combines two analytical tools that each target a different side of the pathogen-host relationship: “reporter” Mtb bacteria that glow different colors depending on how stressed they are in their environment; and single-cell RNA sequencing (scRNA-seq), which yields RNA transcripts of individual host macrophage cells.
“For the first time ever, Dr. Davide Pisu in my lab combined these two approaches to analyze Mtb-infected immune cells from an in vivo infection,” Russell said.
After infecting mice with the fluorescent reporter Mtb bacteria, Russell’s team was able to gather and flow-sort individual Mtb-infected macrophages from the mouse lung.
The researchers then determined which macrophages promoted Mtb growth (sporting happy, red-glowing bacteria) or contained stressed Mtb unlikely to grow (unhappy, green-glowing bacteria).
Next, they took the two sorted, infected macrophage populations and ran them through single-cell RNA sequencing analysis, thereby generating transcriptional profiles of each individual host cell in both populations.
When the scientists compared the macrophage single-cell sequencing data with the reporter bacteria phenotype, they found an almost perfect one-to-one correlation between the fitness status of the bacterium and the transcriptional profile in the host cell.
Macrophages that housed unhappy green bacteria also expressed genes that were known to discourage bacterial growth, while those with happy red bacteria expressed genes known to promote bacterial growth.
Scientific experiments rarely play out so nicely.
“What absolutely stunned us is how well it worked,” Russell said.
“When Davide Pisu showed me the analysis I nearly fell off my chair.”
Normally, phenotypes and transcriptional profiles are two characteristics that seldom come together in a perfect match, and this almost never happens from in vivo data.
This near-perfect matchup revealed new nuances. (ANI)
