Human DNA Shows Traces of 40 Million-Year Battle For Survival Between Primate and Pathogen

Dec 17, 2014

By University of Utah

Examination of DNA from 21 primate species – from squirrel monkeys to humans – exposes an evolutionary war against infectious bacteria over iron that circulates in the bloodstream. Supported by experimental evidence, these findings, published in Science on Dec. 12, demonstrate the vital importance of an underappreciated defense mechanism, nutritional immunity. 

“We’ve known about nutritional immunity for 40 years,” says Matthew Barber, Ph.D., first author and postdoctoral fellow in human genetics at the University of Utah. “What this study shows us is that over the last 40 million years of primate evolution, this battle for iron between bacteria and primates has been a determining factor in our survival as a species.” The study models an approach for uncovering reservoirs of genetic resistance to bacterial infections, knowledge that could be used to confront antibiotic resistance and emerging diseases.

Following infection, the familiar sneezing, runny nose, and inflammation are all part of the immune system’s attempts to rid the body of hostile invaders. Lesser known is a separate defense against invasive microbes, called nutritional immunity, that quietly takes place under our skin. This defense mechanism starves infectious bacteria by hiding circulating iron, an essential nutrient it needs for survival. The protein that transports iron in the blood, transferrin, tucks the trace metal safely out of reach. 

Clever as it sounds, the ploy is not enough to keep invaders at bay. Several bacterial pathogens – including those that cause meningitis, gonorrhea, and sepsis – have developed a weapon, transferrin binding protein (TbpA), that latches onto transferrin and steal its iron. Though scientists have known of the offensive strategy, they failed to realize how pivotal the battle over iron has been in the conflict between host and pathogen.


 

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3 comments on “Human DNA Shows Traces of 40 Million-Year Battle For Survival Between Primate and Pathogen

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    Docjitters says:

    Per David N.D., it’s an interesting hypothesis but the article makes no suggestion along these lines. And whilst the transferrins are negatively regulated during inflammation, other related proteins like lactoferrin (particularly significant in breast milk) and ferritin have increased concentration and/or activity in inflammatory conditions. These also mop up free iron to deny bacterial growth. Iron is also toxic to cells in unbound form, human and bacterial. In any case, supplemental iron is usually inorganic which makes its absorption relatively poor to start with, unless you take a bucket-load – in which case the direct toxic effect of the iron is what one should worry about.



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