Researchers report in the journal Cell on insights they have made into the molecular process by which bacteria such as the highly contagious Shigella suppresses the immune system, preventing it from recognising impending infection.
Interferons are the first line of the immune system’s defence against infection. These warn neighbouring cells and prepare them to fight off an incoming infection. Many viruses – including SARS-CoV2 – have evolved proteins which inhibit normal interferon functions in order to increase infectivity.
Whether bacteria such as Shigella, which causes dysentery, are also able to interfere with the immune system and its capacity to fight the infection was previously unknown. Shigella is highly contagious, requiring only a small inoculum (10 to 200 organisms) to cause an infection.
The study found that Shigella inject a protein called “OspCs” into cells, which blocks the host’s interferon response, allowing the bacteria to successfully infect the host.
Interestingly, OspCs blocked interferon signalling by preventing cells from adapting to changing concentrations of calcium – a molecular signal that usually alerts a cell to infection and damage.
This newly identified strategy tricks the immune system, preventing the body from mounting an effective immune response to infection by decoding host calcium signals.
“This study was another perfect example of how studying pathogens can not only lead to a better understanding of infectious processes, but can also reveal the complexity of host responses to infection,” said Dr Charlotte Odendall.
These findings may be the first steps towards new bacterial treatments in the future, the researchers said.
Source: Kings College London
