Researchers discover how malaria parasite disperses from red blood cellsSeptember 20, 2005
Researchers at the National Institute of Child Health and Human Development have determined the sequence in which the malaria parasite disperses from the red blood cells it infects. The National Institute of Child Health and Human Development is one of the Institutes comprising the National Institutes of Health.
The study appears in the September 20 Current Biology.
"This discovery provides the groundwork for possible new approaches to treating malaria, " said Duane Alexander, M.D., Director of the NICHD. "The malaria parasite is growing resistant to the drugs used to treat it, and new knowledge is essential for developing strategies to protect against the disease."
The study supplants earlier theories on how the malaria parasite spreads from the red blood cells it infects.
According to the World Health Organization, malaria kills more than 1 million people a year. (The WHO fact sheet, "What is Malaria?" is available on the organization's Web site at http://mosquito.who.int/cmc_upload/0/000/015/372/RBMInfosheet_1.htm )
Malaria is caused by four species of the parasite Plasmodium, the most common and deadly of which is Plasmodium falciparum. P. falciparum spends part of its life cycle in the salivary glands of mosquitoes and is transmitted to human beings through the bite of infected mosquitoes. The parasite infects red blood cells. Called a merozoite at the stage of its life when it infects red blood cells, the parasite multiplies inside the cell, until the cell ruptures and releases them. The newly released merozoites infect still other cells, and the process begins again.
To conduct the study, the researchers stained red blood cells infected with P. falciparum with two kinds of dye, explained the study's senior author, Joshua Zimmerberg, M.D., Ph.D., Chief of NICHD's Laboratory of Cellular and Molecular Biophysics. One dye stained the blood cells green, the other stained the parasites red.
In the first stage of the merozoites' release, which the researchers dubbed the "irregular schizont" stage, the red blood cell resembles a lop-sided fried egg, with the parasites visible as a sphere near the center of the cell. (A diagram of the entire sequence appears at http://www.nichd.nih.gov/new/releases/malaria_graphic.cfm ) The cell's lop-sided appearance probably results from destruction of the cytoskeleton, the molecular scaffolding that helps the cell to maintain its rounded shape.
In the next stage, called the "flower" stage, the red blood cell assumes a roughly spherical shape, covered with rounded structures that resemble the petals of a flower. Shortly thereafter, the blood cell's membrane appears to break apart. At roughly the same time, cellular compartments, called vacuoles, which encase the newly formed merozoites, also break apart. The entire process has an explosive appearance, dispersing the merozoites some distance from the cell.
During the release, Dr. Zimmerberg explained, the cell membrane appears to collapse inward upon itself and fragment into pieces.
One previous theory held that the red blood cells and the merozoite-containing vacuoles inside them swelled and then burst like a balloon containing too much air.
"The swelling was an artifact of too much light from the microscope," Dr. Zimmerberg said. "The cell membrane was light sensitive. When we turned the light down, we didn't see the swelling." Rather, he said, upon release of the merozoites, the cell membrane appeared to contract in upon itself.
Another theory held that the merozoite-containing vacuoles would fuse with the cell membrane, and then release their contents.
"But we didn't see any fusion," Dr. Zimmerberg said.
The third theory held that the cell membrane ruptured, expelling merozoite-containing vacuoles. Again, however, the researchers observed that this theory also offered an inaccurate picture, as the vacuoles ruptured at roughly the same time as the cell membrane.
Each step in the release process is a potential avenue for new therapies to treat the disease, Dr. Zimmerberg said. By first understanding how the parasite brings about these steps, it may be possible to find ways to prevent them from occurring.
NIH/National Institute of Child Health and Human D
Related Malaria Parasite Current Events and Malaria Parasite News Articles
Cyclin' out of gear: Malaria parasites grinding to a halt
Scientists from The University of Nottingham have uncovered the role of cyclin -- the protein molecule that drives the growth of malaria within mosquitoes.
Relapsing infections could challenge malaria eradication
Eliminating malaria in the Asia-Pacific could prove more challenging than previously thought, with new research showing that most childhood malaria infections in endemic areas are the result of relapsed, not new, infections.
New studies show nobel prize-winning drug that knocks out parasitic worms could have second act fighting malaria
A workhorse of a drug that a few weeks ago earned its developers a Nobel prize for its success in treating multiple tropical diseases is showing early promise as a novel and desperately needed tool for interrupting malaria transmission, according to new findings presented today at the American Society of Tropical Medicine and Hygiene (ASTMH) Annual Meeting.
New approach toward a broad spectrum malaria vaccine
In a recent breakthrough to combat malaria, a collaboration of Indian and American scientists have identified a malarial parasite protein that can be used to develop antibodies when displayed on novel nanoparticles.
Public Release: 13-Oct-2015 Malaria vaccine provides hope for a general cure for cancer
The hunt for a vaccine against malaria in pregnant women has provided an unexpected side benefit for Danish researchers, namely what appears to be an effective weapon against cancer. The scientists behind the vaccine aim for tests on humans within four years.
Genes linked with malaria's virulence shared by apes, humans
The malaria parasite molecules associated with severe disease and death--those that allow the parasite to escape recognition by the immune system--have been shown to share key gene segments with chimp and gorilla malaria parasites, which are separated by several millions of years, according to a new study led by Harvard T.H. Chan School of Public Health.
Scientists discover new system for human genome editing
A team including the scientist who first harnessed the revolutionary CRISPR-Cas9 system for mammalian genome editing has now identified a different CRISPR system with the potential for even simpler and more precise genome engineering.
Crime-scene compound may be newest tool in fight against malaria
The compound that detectives spray at crime scenes to find trace amounts of blood may be used one day to kill the malaria parasite.
3-D image of malaria 'conductor' aids search for antimalarial drugs
The first three-dimensional image capturing a critical malaria 'conductor' protein could lead to the development of a new class of antimalarial drugs.
Study identifies new way to kill the malaria parasite
Scientists have discovered new ways in which the malaria parasite survives in the blood stream of its victims, a discovery that could pave the way to new treatments for the disease.
More Malaria Parasite Current Events and Malaria Parasite News Articles