Noxious parasite forms hybrids and deceives the immune system

The small parasite Trypanosoma cruzi has a nasty ability to cause serious illness. Researchers at the Karolinska Institutet have now mapped its ability to deceive the immune system by forming new variants that are mixtures of different strains.

Infection with Trypanosoma cruzi is spread via a type of blood-sucking predatory beetle and can induce Chaga’s disease, which can cause severe symptoms in the gastrointestinal tract and the heart. The disease affects millions of people in Central and South America, causing thousands of deaths a year.

Researchers at the Karolinska Institutet, among others, have now examined the parasite’s remarkable ability to form hybrids, which are often better at avoiding the immune system and causing disease.

The study, published in the journal Elife, is based on parasite strains that spontaneously form hybrids in a laboratory environment. The researchers isolated DNA from both the parental parasites and several offspring and mapped the genome via large-scale DNA sequencing.

The study revealed that the hybrids contain all the DNA from both parents initially, but the amount of DNA gradually decreases and eventually ends up at the right level. It was also revealed that there is a significant exchange of genetic material, so-called genetic recombination.

According to Björn Andersson, Professor of Genome Analysis at the Department of Cell and Molecular Biology at the Karolinska Institutet, who led the study, the exchange of genetic material can generate new gene variants that make the parasite more harmful.

“More knowledge about how this process works can contribute to new methods for diagnosing, preventing and treating Chaga’s disease,” he said in a press release.

The project is now continuing with a more detailed mapping of the parasite’s ability to vary its genes, and work is also underway to improve the diagnosis of Chaga’s disease in Bolivia.

The study was conducted in collaboration with the Universidade Federal de Santa Catarina in Brazil and the London School of Hygiene and Tropical Medicine in the UK. The research was mainly funded by the Swedish Research Council in Sweden and Capes in Brazil.

Read the study: “Experimental microevolution of Trypanosoma cruzi reveals hybridization and clonal mechanisms driving rapid diversification of genome sequence and structure.”

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