$50 dye could change the way we design malaria vaccines

James O'Connor sitting at a computer

James O'Connor

Back in October 2018, James O’Connor read a paper for Journal Club.

That might sound like just another mundane part of doing a PhD but hidden in the supplementary figures was an image showing a technique using a $50 dye that hadn’t been tried at the ANU John Curtin School of Medical Research (JCSMR). 

James thought “why don’t we give this a go?”

And so, he did.

James’ give-it-a-go attitude, paired with the $50 dye, is bad news for the malaria parasite.

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Despite many efforts there are no potent and long-lasting vaccines to malaria and, in 2018, an estimated 228 million cases occurred worldwide.

The malaria parasite has a complex lifecycle, so it is challenging to create an effective vaccine.

When fighting pathogens, such as malaria, it is key that the immune system is able to produce antibodies to mark a pathogen for destruction.

But it is difficult for the body to produce antibodies to pathogens it has never encountered before, and also fight the infection at the same time. This is why vaccines are so important.

“Vaccines give the body a practice run at a pathogen before it is expected to perform in front of the real thing,” explains James O’Connor, PhD candidate in the Cockburn Group at JCSMR.

James’ research has been done in collaboration with the National Institutes of Health (USA) and shows the antibodies that are more effective at stopping the malaria parasite, which are able to do so at multiple points in its lifecycle.

“The current malaria vaccine uses a truncated parasite protein to generate immunity, and we suggest that this shortened version does not help the immune system generate the most effective antibodies."

The lifecycle of malaria starts when a person is bitten by an infected mosquito, and then the parasite travels to the liver to proliferate.

Medical imaging

The green parasite traversing liver cells, which become filled with dye once the parasite bursts through the cell wall.

“We want to be able to design a vaccine to first try to stop the parasite when it is in the skin.”

“But, if even one of the parasites manages to evade the antibodies in the skin, we want to be able to use the same protection in the liver to stop its progress.”

Once the parasite is finished multiplying in the liver, the next stage of the lifecycle is to infect red blood cells.

“We don’t want the parasite to reach the blood stage of the life cycle.

"It is during the blood stage of the parasite lifecycle that causes the symptoms of malaria in humans and most often, children. These symptoms include severe anaemia and end-organ damage.”

James knows that the search for a malaria vaccine is a key interplay between medical research and medicine and is grateful he has the opportunity to pursue both with support from JCSMR and the ANU Medical School.

“This research involved looking at the nine most protective antibodies humans produce against malaria to find out how, and why, they elicit protection.”

In his research, James used the dye described in this paper (that he read for Journal Club) to track the progress of the malaria parasite and antibodies through the circulation and into the liver cells.

He watched the dye moving through the vessels using a two-photon microscope located in the JCSMR Imaging and Cytometry Facility (ICF). The two-photon microscope allows imaging of living tissues up to about one millimeter in thickness, which is about the size of a sharpened pencil head.

“We found something we didn’t expect.”

James describes how he watched as the malaria parasite punched holes in liver cells which caused the dye to rush into the cell.

But then, by injecting these nine different human antibodies prior to infection, he watched as the two most potent ones stopped the parasite’s progress through the liver cells.

“Using this technique, we observed how these antibodies not only bind to the parasite, but how they influence their movement and ability to leave the vessels, and invade liver cells.

“The full-length proteins of the parasite that cause the body to generate these potent antibodies are not currently included in the malaria vaccine and therefore these high affinity antibodies can’t be generated.

“The antibodies make the parasite shed its outer protein, prevent its invasion of liver cells, and cause them to curl up, die or even burst right in front of us”.

Medical imaging

When the potent antibodies bind to the parasite. The parasite is green, the antibody is blue. As the antibody binds, the protein skin sheds away and the parasite dies (green fades).

“We have shown the antibodies that are not generated by the current vaccine, are substantially more effective at getting rid of the parasite.

“Using the whole protein (or even the whole parasite) in a vaccine, not the truncated version, would allow for the body to generate these highly potent and dual binding antibodies during the dress rehearsal.

“These antibodies would be able to bind to the surface proteins of the parasite in the skin and in the liver, preventing the parasite moving on to the blood stage of disease.

“What I love about this project is this is an amazing technique and I have been able to watch how we could stop the parasite in real time.”

James said the technique used in this paper had such positive results that people from all over the world are now contacting JCSMR to perform this kind of analysis for their own immunology research. 

“It is a tricky technique to get right, but when it works… it's really stunning science.”

This research has been published in Immunity.

James O’Connor is a PhD candidate at Australia’s national medical research institute, JCSMR, and is also currently doing his MChD at the ANU Medical School. Explore the range of postgraduate degrees in health and medicine available at ANU here.

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