Chlamydia wears a cape but it may not be invisible forever


Chlamydia is the most commonly reported infectious disease in Australia, with nearly 97,000 diagnoses in Australia each year. Although often asymptomatic, it can lead to serious health problems such as infertility, ectopic pregnancy and chronic pain.

Part of the reason chlamydia is so prevalent, it is because the bacteria that causes it, Chlamydia trachomatis, is very adept at evading the body’s immune system, allowing an infection to last for months. A new study from Duke University in the US has focused on exactly how it does this, which has discovered a protein that could prevent cells in the body from marking the bacteria for destruction once it has invaded. the cell.

Like a wolf in sheep’s clothing, pathogenic bacteria “hide” in a piece of the target cell’s membrane which can then float inside the cell, undetected.

Mice have their own type of chlamydia. Credit: Dr. TJ Martin/Getty Images

Chlamydia is able to do this so well that even when primed for the bacteria using an immune stimulant, human cell cultures are still unable to see it. “We said, there’s the pathogen,” says Jörn Coers, associate professor of molecular genetics and microbiology and co-author of the study. “Our defense system should see it. Why can’t he see it?

The researchers studied the interaction between human cell cultures and mouse chlamydia. Unlike human chlamydia, human cells were able to easily identify and destroy mouse chlamydia. “Humans don’t get mouse chlamydia because it evolved with mice and human chlamydia evolved with humans,” Coers said. “So there’s this really fine adaptation that the pathogen has gone through.”

“This common ancestor can go back as far as when humans and rodents separated from each other. That’s a long time for bacteria to really refine their interactions with their host species.

Read more: The first chlamydia vaccine could be a shot in the nose

Chlamydia cells with genetic mutations on the right panel
A wild type Chlamydia (green) surrounded by the GarD protein (red) which prevents it from being detected inside human cells. Right: Chlamydia with GarD removed (green) are enveloped by the antimicrobial proteins ubiquitin (yellow) and RNF213 (magenta). Credit: Stephen C. Walsh/Duke University

When examining the differences, the researchers noticed a particular protein in the human form called GarD (resistance determinant gamma) that seemed to be able to block the ability of another protein called RNF213 or “mysterin” to notice and marking the chlamydia for destruction.

“RNF213 is essentially the eyes of the immune system,” Coers said. Thus, by blinding mysterin, the human form of chlamydia is able to sneak past unnoticed.

When the researchers mutated the gene responsible for GarD, the bacterium became much more vulnerable to extermination by the human cell.

Although this is an important step forward in understanding how chlamydia and other similar pathogens can evade the body’s immune system, it remains unclear how mysterin is able to detect pathogens. pathogens, nor how GarD manages to blind him.

These questions will need to be answered before the power of this finding can be harnessed for targeted therapies.

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