The researchers who studied the malaria For decades, hoping to find a cure, they had long thought they had identified a blood type that seemed to defend against the disease. But a new study concludes that even some people with the protective blood group have been infected. The question now is: how?
The results of research were published on Cell Host & Microbe.
Malaria: finding a cure is more complicated than it might seem
“This could mean that the specific genetic mutation related to this blood type does not completely stop malaria, or that the virus may have found another way to enter blood cells,” said Peter Zimmerman, professor of pathology at Case Western Reserve University. School of Medicine and senior author of the study. “It’s a big deal because it could change the way we try to get rid of this type of disease parasite.”
“This parasite, called Plasmodium vivax, or P. vivax, was common in northeast Ohio,” said Christopher King, study co-investigator and professor of pathology. “And it was broadcast in the United States, Florida and Texas, this summer for the first time in 20 years.
“We know,” King said, “that the United States is at risk of malaria reintroduction due to climate change and increased immigration and travel from disease-endemic areas.”
Collaborators of the study include French researchers (Célia Dechavanne and Benoit Gamain, of the National Institute of Blood Transfusion, INSERM/Diderot University of Paris); and Madagascar (Arsène Ratsimbasoa, of the University of Fianarantsoa).
“Researchers have been trying to make a dent in the understanding of resistance and susceptibility to P. vivax infection in African populations for more than 100 years,” Zimmerman said. “More than 2.5 billion people live in Africa and Southeast Asia, where the parasite is found. Hundreds of thousands of people die every year. Overall it is one of the three main infectious diseases worldwide together with tuberculosis and HIV/AIDS.”
The team is studying a specific blood group (Fy-negative) in the blood of most people in Africa and of African descent, called “the Duffy silent blood group”. Duffy-negative people have a mutation in the DNA code (GATA-1) that causes the protein not to be expressed on the surface of red blood cells.
The researchers conducted experiments using laboratory-grown blood cells and cells taken from bone marrow to study the Duffy silent blood group.
“Surprisingly, we found that even when people lack the GATA-1 DNA code, the Duffy protein sometimes appears on their red blood cells,” Zimmerman said. “Our findings suggest that the bone marrow and other places where blood cells are made are important for the malaria parasite to find red blood cells with the Duffy protein to grow and cause disease.”
In other experiments in the laboratory, they examined the blood of people with Duffy silent blood type. They noted that P. vivax malaria infection was often detected using a special test rather than the usual microscopic test.
This means that people with Duffy-silent blood type can still have the infection, but it is not always easy to see in regular blood tests. In other words, they found that P. vivax can invade the red blood cells of people with the Duffy-silent trait. Additionally, if they have the infection in the bone marrow, they produce the transmissible form of the parasite. Mosquitoes can acquire it and cause infections in other people.
“This finding raises questions about how malaria parasites cause infection and disease, especially because some people with the infection don’t show many signs in their blood,” Zimmerman said. “We need to look at the blood more closely to better understand how widespread and severe this type of malaria is in people with the Duffy-silent trait.”
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