Scientists discover new stage in malarial infection

December 10, 2000

St. Louis, Dec. 11, 2000 -- Researchers have identified a previously unknown step that enables the malaria parasite to spread in the bloodstream. And they have found a way to block this key event. The findings, reported in the Dec. 12 online edition of Proceedings of the National Academy of Sciences, may lead to promising targets for drug development.

Malaria afflicts 300 to 500 million people worldwide and kills nearly 2 million children each year. The parasites that cause the disease multiply inside red blood cells, bursting from them to invade new cells.

"But little was known about how the parasites break out of cells," said Daniel E. Goldberg, M.D., Ph.D., senior author of the paper and a professor of medicine and of molecular microbiology in the Howard Hughes Medical Institute at Washington University School of Medicine in St. Louis. "Now that we have identified the major stages, we will be able to study the process better."

As if they were instantly replaying a football scrimmage, the researchers slowed the action with inhibitors. They discovered that the parasites emerge from red blood cells in two steps. "First, they exit enclosed in a sac they have made. Then the sac quickly bursts, releasing the parasites," Goldberg said.

Enzymes that break down proteins--proteases--were thought to help the parasite emerge from red blood cells. And inhibitors of these enzymes are effective against other infectious agents, notably the virus that causes AIDS. Therefore, Goldberg's group studied the effect of a protease inhibitor called E64 on the malaria parasite.

E64 did not stop the parasites from escaping out of red blood cells. But it prevented them from rupturing the sac that enclosed them. When E64 was removed, the parasites spilled from the sac to infect other red blood cells. Similar sacs had been seen in infected blood samples, but only fleetingly, and their significance had not been grasped. "By better understanding the role of proteases in the parasite's escape from the host cell, we may be able to develop clinically useful inhibitors that will keep it from getting out to infect new cells," Goldberg said.
Salmon BL, Oksman A, Goldberg DE. Malaria parasite exit from the host erythrocyte: a two step process requiring extraerythrocytic proteolysis. Proceedings of the National Academy of Sciences, online edition, Dec. 12, 2000.

The work was supported by the Burroughs Wellcome Fund

Washington University School of Medicine

Related Parasites Articles from Brightsurf:

When malaria parasites trick liver cells to let themselves in
A new study led by Maria Manuel Mota, group leader at Instituto de Medicina Molecular, now shows that malaria parasites secrete the protein EXP2 that is required for their entry into hepatocytes.

How deadly parasites 'glide' into human cells
A group of scientists led by EMBL Hamburg's Christian Löw provide insights into the molecular structure of proteins involved in the gliding movements through which the parasites causing malaria and toxoplasmosis invade human cells.

How malaria parasites withstand a fever's heat
The parasites that cause 200 million cases of malaria each year can withstand feverish temperatures that make their human hosts miserable.

New studies show how to save parasites and why it's important
An international group of scientists published a paper, Aug. 1, 2020, in a special edition of the journal Biological Conservation that lays out an ambitious global conservation plan for parasites.

More flowers and pollinator diversity could help protect bees from parasites
Having more flowers and maintaining diverse bee communities could help reduce the spread of bee parasites, according to a new study.

How Toxoplasma parasites glide so swiftly (video)
If you're a cat owner, you might have heard of Toxoplasma gondii, a protozoan that sometimes infects humans through contact with contaminated feces in litterboxes.

Parasites and the microbiome
In a study of ethnically diverse people from Cameroon, the presence of a parasite infection was closely linked to the make-up of the gastrointestinal microbiome, according to a research team led by Penn scientists.

Clocking in with malaria parasites
Discovery of a malaria parasite's internal clock could lead to new treatment strategies.

Feeding bluebirds helps fend off parasites
If you feed the birds in your backyard, you may be doing more than just making sure they have a source of food: you may be helping baby birds give parasites the boot.

Scientists discover how malaria parasites import sugar
Researchers at Stockholm University has established how sugar is taken up by the malaria parasite, a discovery with the potential to improve the development of antimalarial drugs.

Read More: Parasites News and Parasites Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to