Novel antigen holds promise for malaria vaccine

MosquitoIn 2012, malaria was responsible for around 627,000 deaths worldwide, of which 460,000 occurred among African children under the age of 5 years. Now, researchers have identified a substance that they say could be a potential vaccine candidate for malaria.

Malaria is a life-threatening disease caused by Plasmodium parasites transmitted to humans from the bites of infected Anopheles mosquitoes. The most harmful parasite is Plasmodium falciparum.

Initial symptoms of the disease include headache, fever, chills and vomiting. If untreated, it can lead to severe anemia, respiratory difficulties, cerebral malaria and death.

Malaria is most common among people – particularly children – living in sub-Saharan Africa. However, many individuals who live in high-infection areas often develop protective immune system responses that restrict malaria parasite levels in the blood, meaning severe symptoms of the disease are prevented.

PfSEA-1 ‘stops malaria parasite from leaving a red blood cell and entering another’

The research team – including investigators from National Institute of Allergy and Infectious Diseases (NIAID), Rhode Island Hospital and Harvard Medical School in Massachusetts- investigated plasma samples of 785 children aged 2 years from Tanzania in East Africa who were either susceptible or resistant to malaria infection.

Researchers say the antigen PfSEA-1 could be a potential malaria vaccine candidate.

After a series of gene-screening and laboratory tests, the researchers identified an antigen called Plasmodium falciparum schizont egress antigen-1 (PfSEA-1).

Further tests on the antigen revealed that it stops a malaria parasite from leaving one red blood cell to occupy another. This is a notable finding, according to study co-author Dr. Jonathan Kurtis, director of the Center for International Health Research at Rhode Island Hospital. He explains:

“Many researchers are trying to find ways to develop a malaria vaccine by preventing the parasite from entering the red blood cell, and here we found a way to block it from leaving the cell once it has entered. If it’s trapped in the red blood cell, it can’t go anywhere – it can’t do any further damage.”

The research team then vaccinated five groups of malaria-exposed mice with the PfSEA-1 antigen. They found that the mice demonstrated lower malaria parasite levels and a longer lifespan, compared with mice that were unvaccinated.

The anybody levels in plasma samples from 453 of the Tanzanian children were then measured. The researchers found that during periods when the children had detectable antibodies to PfSEA-1 during a high-infection season, no severe malaria occurred.

To investigate further, the team measured the antibody levels in plasma samples of 138 males ages 12-35 who lived in an area of Kenya with high malaria infection. They found that those with detectable antibodies to PfSEA-1 had 50% lower malaria parasite levels during a high-infection season, compared with those who did not have these detectable antibodies.

Dr. Kurtis explains the team’s findings further in the video below:

Researchers hope to test PfSEA-1 in human trials ‘very soon’

According to the investigators, these findings suggest that PfSEA-1 could be a potential vaccine candidate that could work by itself or in combination with other vaccines to tackle malaria at different stages of infection.

They note that although further animal trials are needed, they hope to start phase 1 trials in humans very soon.

Dr. Kurtis says:

“Our findings support PfSEA-1 as a potential vaccine candidate, and we are confident that by partnering with our colleagues at the National Institutes of Health and other researchers focused on vaccines to prevent the parasites from entering red blood cells, we can approach the parasite from all angles, which could help us develop a truly effective vaccine to prevent this infectious disease that kills millions of children every year.”

Earlier this year, Medical News Today reported on a study from researchers at Indiana University School of Medicine, who identified a protein that could lead to treatments for malaria and toxoplasmosis.


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