Scientists in Sheffield have discovered a specialised white blood cell found in birds that can destroy a fungal infection which kills more than one million people a year.
Cryptococcus neoformans is a fungus that causes fatal infections in people with weakened immune systems – particularly those who have advanced HIV/Aids.
The fungus mostly infects the lungs or the central nervous system, with symptoms including a cough, shortness of breath, chest pain, fever, headaches, nausea, vomiting and sensitivity to light.
It is thought the fungus, carried by birds and found in their droppings, is responsible for more than one million deaths a year. Most people become infected after breathing in the microscopic spores and it is rare for healthy individuals to be affected.
But now a team at the University of Sheffield, who questioned how birds could carry the fungus and not become infected, have shown that a particular white blood cell within the bird’s blood system, called a macrophage, is able to block the growth of the fungus.
The scientists, led by Dr Simon Johnston, found that the fungus can grow slowly within a bird’s digestive tract, but if it tries to invade the bird’s body then the immune system immediately destroys it – explaining why healthy birds can still spread the infection.
Dr Johnston said: “Birds have a higher body temperature than humans, 42C instead of 37C, but this alone is not enough to fully stop the fungus.
“By studying bird cells under the microscope, we have seen that macrophage cells have the ability to completely block the growth of the fungus, which can be fatal in humans.
“Understanding where the disease comes from and how it spreads is critical. If we can learn how some animals are able to resist infection we might be able to gain insights into how we can improve the human immune response to this fungus.”
Published in Nature Scientific Reports, the work was carried out in collaboration with the University of Birmingham and forms part of a larger international effort to understand, tackle and eliminate the fungus.
Dr Johnston said his team are now working with leading scientists from all over the world to try to understand more about the pathogen’s origin and how the human body reacts to and fights it and other infections.
“Many human diseases are spread by birds, but we know surprisingly little about their immune systems. Discovering how they resist otherwise fatal infections offers the hope of improving our ability to intervene in this cycle and prevent a diverse range of human diseases,” he added.
“In addition, infectious diseases of birds themselves are a major threat to agriculture, such as when 170,000 poultry were culled due a suspected bird flu outbreak.
“Learning more about the bird immune system is an important step in developing new ways to combat such infections.”
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