• A study finds key that could explain why some people are less susceptible to contracting Chagas disease

The name Chagas disease may sound like a big unknown in countries in the north of the planet, but just cross the equator of the globe to see how this infection wreaks real havoc. It is estimated that this disease, caused by the parasite ‘Trypanosoma cruzi’, affects more than six million people a year in South America and has already become one of the main causes of mortality in the region. This disease extends to most of the tropical areas of the world, except one: the Amazon. But Why is this happening? What do the inhabitants of this jungle have that keeps them safe from this parasite?

To try to unravel this riddle, a international team of researchers traveled to the Amazon to try to find out how local populations manage to avoid chagasic infections. The research studied the data from 118 current inhabitants of a twenty populations of the Amazon. “We focused on finding signs of positive natural selection related to tropical diseases in America”, explains Tábita Hünemeier, a researcher at the Institute of Evolutionary Biology (IBE-CSIC) and one of the specialists who led the study.

Chagas causes more than six million infections per year in South America

The results of this analysis, published this Wednesday in the prestigious scientific journal ‘Science Advances’, managed to identify a genetic mutation that could explain why the populations of this tropical forest are especially resistant to chagasic infections. It is, specifically, a variant of the PPP3CA gene. “This mutation could be the cause of the disease is milder or there is less infection in these populations”, comments David Comas, professor of Biology at the Department of Medicine and Life Sciences at Universitat Pompeu Fabra, researcher at IBE and co-author of this study.

Effects of genetic mutation

Having identified the gene suspected of protecting the Amazon populations from Chagas, the researchers began to ask about this mutation in labs. The PPP3CA gene encodes a key protein in the activation of immune cells, in the innate immune response and in the internalization of the ‘T.cruzi’ parasite in human cells. Mutation of this gene, which is expressed both in cardiac tissue and like immune cells, it is especially abundant among Amazonian populations.

This mutation makes it difficult for the parasite to internalize and, therefore, reduces the path of infection.

The scientists used genetically modified stem cells to express this mutation. The analyzes showed that in the tissues where this genetic variant is found, there is less parasite internalization and in this way a shorter course of infection and disease in the body.

The team of researchers who conducted this analysis conclude that this mutation is the direct result of a natural selection process what started 7,500 years ago, after the populations of the Amazon separated from the populations of the Andes and the Pacific coast. In this sense, experts maintain that epidemics would have positively selected individuals with greater resistance to tropical diseases, such as Chagas disease, generating a unique resistance in this population.