Eureka moment for potential parasite vaccine

By | Health & Wellness
A red blood cell containing the malaria parasite, characterised by it's bumpy exterior (blue) compared to the smooth, healthy blood cells (red). A new vaccine could be produced based on the antibodies formed in response to a protein. Credit image@ NIAID,

Malaria, the parasite-driven condition spread via mosquito vectors, is one of the most notorious pathogens, endemic to equatorial regions within sub-Saharan Africa, whilst also equally at home in areas of Asia and the Americas. Being characterised by warm temperatures, high rain fall and plenty of stagnant water, these countries are a breeding ground for mosquitoes, and hence allowing the parasite to thrive.

Nets, insecticides and insect repellents are effective, as are the use of natural mosquito predators, all reducing the rate of transmission. And the condition is treatable using a variety of drugs depending of the severity of the symptoms, however the parasite still persists.

Importantly, a malaria vaccine, one of the most effective ways of dealing with a pathogen, still remains elusive to scientists. However, a eureka moment in this field has been reported by Rhode Island Hospital scientists regarding the potential to develop a vaccine.

The study was published in the scientific journal Science, with specialists in the field of malarial immunology and vaccinology, biostatistics and paediatrics all contributing to the discovery.  

Caused by a genera of protozoan (a type of unicellular organism) known as Plasmodium., there are five known species capable of living within a human host and causing malaria, all with the same intriguing lifecycle.

A mosquito with the malaria parasite with infect a human when feeding on their blood, with the sporozoites (highly motile forms of the Plasmodium) seeking out and living within the liver. Within the organ, the sporozoites mature into a new phase known as merozoites, leaving the liver and begin inhabiting within the red blood cells of its human host.

Some of these structures will develop into sexual forms, creating male and female gametes of the parasite so as to ensure the further development of the species when a new mosquito feeds on the host.

The research began back in 2002, explains Dr. Jonathan Kurtis during the news release of the findings, where colleagues and coauthors Patrick Duffy and Michal Fried working for the National Institutes of Health began taking samples from 785 Tanzanian children.

“Six years ago we began using these samples to identify novel vaccine candidates and now it’s coming full circle” said Kurtis. Some of the research was conducted in mice test subjects, however the actual discovery was found in human samples, he added, meaning “the results will effectively translate to humans”.

Using a differential screening method to examine the entire set of proteins produced by an organism, the team discovered a novel antigen expressed by red blood cells with the parasite Plasmodium falciparum, which they dubbed PfSEA-1. Antigens are structures on the surface of cells that essentially label them, as well as helping with cell signalling and recognition.

They vaccinated the mice with this antigen, and then exposed them to the malaria parasite, and monitored their health. They noticed how those who underwent the vaccination, when compared to the control group, survived longer and showed reduced levels of the parasite in screens.

It was Kurtis’ post-doctoral fellow that discovered the utility of this antigen, showing that the antibodies produced by the host in response to the PfSEA-1 protein effectively cages the parasite within the red blood cell.

“It was truly a moment of discovery,’” said Kurtis.

Following this finding, the researchers examined the samples derived from the Tanzanian children. They saw that in children naturally producing antibodies to this antigen there was zero cases of sever malaria. To validate the results, the team studied samples collected from 1997 in children from Kenya, and once again saw a similar pattern in children with PfSEA-1 antibodies: fifty per cent lower blood parasite levels.

“We still have additional trials ahead of us, first in another animal model, however we aim to begin Phase I trials in humans very soon,” explained Kurtis during the news release. “Our findings support PfSEA-1 as a potential vaccine candidate”.

In the meantime, what do you feel should be implemented to help reduce the spread of malaria?



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