Parasites' quirky trick to persuade immune cells to invite them in for dinner

Washington, Aug 21 (ANI): Scientists from Imperial College London have found that parasite leishmania tricks immune system to let it enter the body and cause skin infection.

Leishmaniasis is an infection caused by Leishmania parasites that cause disfiguring and painful skin ulcers, and in severe cases the infection can also spread to the internal organs.

Patients with the infection often suffer from social exclusion because of their disfigurement.

Leishmania parasites are transmitted by sand flies. After the parasites infect a sand fly, they make a sticky gel so that when the fly bites a human, it regurgitates this gel into the body.

The new study conducted over mice showed that the gel persuades immune cells known as macrophages to feed the parasites, rather than killing them.

The gel helps the parasites to establish an infection by enticing macrophages to the bite site. Macrophages usually kill invading pathogens by eating and digesting them.

However, the gel persuades macrophages to engulf the parasites and feed them rather than digest them.

This happens within the first few days following infection, enabling the parasites to establish themselves and infect the skin.

"Leishmaniasis is a very debilitating disease, yet we know comparatively little about the way the parasites are transmitted by sand flies," said Dr Matthew Rogers, lead author of the study from the Division of Investigative Science at Imperial College London.

"This is because when scientists study the disease they usually inject the parasite into tissues without including the gel or the sand fly's saliva. Our new research shows that we must consider the way the parasites enter the body - along with the gel and saliva - if we are to recreate infection and get an accurate picture of what is going on.

"Our new research shows that Leishmania parasites are very cunning - they make their own gel to control the human immune system so they can establish a skin infection.

"There is more work to be done here - our previous work in mice has suggested that injecting a synthetic version of the gel into people might provide them with some protection against infection and we would like to explore this further," he added.

The study is published in PLoS Pathogens. (ANI)