Study reveals that beneficial bacteria protect against malaria

A research team from the Instituto Gulbenkian de Ciência (IGC) led by Miguel Soares has revealed that specific components of bacteria residing in the intestine can trigger a natural defense mechanism that blocks the transmission of malaria.

The key component of the process is a sugar molecule called α-gal (alpha-gal), which is produced by the Plasmodium parasite, the agent responsible for malaria, and also by a strain of Escherichia coli bacteria found in the human intestine. Through experiments carried out on mice, Bahtiyar Yilmaz, a PhD student at the IGC, discovered that the production of α-gal by these bacteria is sufficient to induce the production of natural anti-α-gal antibodies capable of recognizing the same sugar molecule on the surface of Plasmodium.

Immediately after the parasite is inoculated into the skin by the mosquito that transmits malaria, these antibodies bind to α-gal on the surface of the Plasmodium and activate an additional immune system mechanism that kills it before it leaves the skin, preventing it from entering the bloodstream. By doing so, malaria transmission is blocked.

The level of anti-α-gal antibodies, which research has shown to be lower in younger children, may be the differentiating factor in susceptibility to malaria: only a fraction of all adult individuals actually bitten by mosquitoes become infected, which contrasts with the exponentially greater susceptibility of children under 3 to 5 years of age to contracting malaria. An estimated 3.4 billion people are at risk of contracting malaria and WHO data from 2012 indicates that around 460,000 African children died before their fifth birthday.

The research has shown, through experiments carried out on mice, that this protective mechanism can be activated by vaccination against a synthetic α-gal molecule, which is relatively easy to produce and inexpensive. As Miguel Soares explains, "one of the wonders of the protective mechanism we have now discovered is that it can be induced through a standard vaccination protocol, leading to the production of high levels of anti-α-gal antibodies that can bind to and kill the Plasmodium parasite. If we can vaccinate young children against α-gal, many lives can be saved."

Recently published in the journal Cell, the article brings together the results of the study carried out at the IGC in collaboration with the National Institute of Allergy and Infectious Diseases (Maryland; USA), the Institute of Hygiene and Tropical Medicine (Lisbon, Portugal), St Vincent's Hospital and the University of Melbourne (Victoria, Australia), the University of Chicago (Chicago, USA), and the University of Sciences, Techniques and Technologies of Bamako (Bamako, Mali), with funding from the FCT, the Bill and Melinda Gates Foundation (USA) and the European Research Council (ERC).