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How the trigger of African sleeping sickness is hidden in the body
The human and animal immune system is designed to remove defective germs from the organism. Of course, this is not in the interest of the invaders who want to spread unhindered. The parasite Trypanosoma - trigger of African sleeping sickness - has developed a particularly sophisticated system to protect itself from being eradicated by the immune system. It has a camouflage function that constantly changes its surface. So it cannot be recognized by the immune system.
Researchers at the Ludwig Maximilians University in Munich have succeeded in sequencing the entire genome of the parasite Trypanosoma. In doing so, they explained how the parasite manages to evade the immune system in the long term. A sophisticated camouflage strategy makes it virtually invisible to the immune system. In this way, the germ reaches a permanent infection in its host. The study results were recently published in the renowned journal "Nature".
Changing surface structure
As the researchers report, trypanosomes are able to constantly change their surface structure. To do this, you can activate or deactivate certain proteins. In this way you can generate 2000 different surface variants. Based on the surface structure, the immune system judges whether an organism should be controlled or not. The system needs a certain amount of time to make this assessment. Due to the constant change, the immune system cannot recognize the parasite as foreign and it is therefore not combated.
What diseases can the parasite cause?
Trypanosomes can infect the blood of various vertebrates. In most cases, it is transmitted by insects such as the tsetse fly. The causative agent can cause the Nagana epidemic in cattle and the often fatal African sleeping sickness in humans. Symptoms include fever, chills, swelling of the lymph nodes, headache, body aches, edema and itchy rashes. If the parasite attacks the brain, which can take weeks to years, sleep disorders, restlessness, irritability and personality disorders occur. In the further course, epilepsy, speech and coordination disorders as well as chronic fatigue are added. Ultimately, those affected fall into a coma that usually ends in death.
The amazing ability to change shape
"We are particularly interested in how this genetic variability is regulated," study director Professor Nicolai Siegel explains in a press release on the study results. The researchers have decoded the entire genome of the parasite Trypanosoma brucei and arranged it in three dimensions. The team was able to identify the proteins that are responsible for the camouflage function. These protein variants are located in the cell nucleus at the same locations where the genes encoding the surface proteins are located. The removal of certain proteins from this complex changed the entire three-dimensional structure of the parasite's DNA.
New strategies to combat
"A better understanding of these defense mechanisms is also important for research into other diseases," the researchers write. In the constant struggle between the host's immune system and the intruder, numerous other germs have developed similarly effective strategies. The scientists cite malaria pathogens, Candida intestinal fungi and many types of bacteria as examples. (vb)