Medical Research Council - London Institute of Medical Sciences

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Secrets of Secretion

Greater understanding of TB by investigating how infection of zebrafish by one strain is controlled

25 September 2018

Secrets of Secretion

Responsible for causing tuberculosis, a disease affecting millions of people worldwide, Mycobacterium tuberculosis can infect macrophages, immune cells which normally engulf and destroy pathogens. Critical to the bacterium’s success is a sophisticated secretion system, enabling it to transport useful compounds into host cells. Multiple proteins make up this system but their specific roles are difficult to disentangle, so researchers are investigating them in a closely-related pathogen, Mycobacterium marinum, causing tuberculosis in fish. They found especially intriguing results for one protein, named EspH. While bacteria lacking EspH were less effective at infecting macrophages in the lab, they were very virulent when infecting zebrafish larvae, forming aggregates inside and around zebrafish blood vessels, a phenomenon known as cording (pictured, with bacteria in red, blood vessels in green and macrophages in blue).This suggests that host factors interact with the bacterium’s own proteins, adding another layer of complexity to the processes behind tuberculosis infections.

Written by Emmanuelle Briolat

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