Evolution offers clues for malaria drugs
by Kelly Stone
It infects more than 500 million people worldwide each year – and kills between one and three million mostly under the age of five.
Malaria and reducing its deadly toll are at the heart of UniSA researcher Dr Ellen Nisbet’s work.
An evolutionary biologist and lecturer in life sciences with the School of Pharmacy and Medical Sciences, Dr Nisbet is studying the evolution of the malaria parasite with the ultimate aim of developing better anti-malarial drugs.
"Many of the key anti-malaria drugs are now ineffective due to the spread of resistance," she said.
"I’m interested in the evolution of the malaria parasite. If we understand how it evolved, we might have a better hope at designing new more effective drugs."
Dr Nisbet said that about 15 years ago, researchers discovered that the ancestor of the malaria parasite was able to carry out photosynthesis – using sunlight as energy, just as plants and algae do – but that this ability has since been lost.
"I’ve been wondering how the parasite changed from a free-living cell, to one that hides inside mosquitoes and human red blood cells, and causes disease. What did this ancestor look like? How and why did it forget how to do photosynthesis?
"Then, last year, Dee Carter in Sydney and Bob Moore, who’s now at Flinders, discovered the missing link – algae that’s very closely related to the malaria parasite. And it was living in Sydney Harbour.
"These algae, known as Chromera, don’t cause disease, but instead live inside corals. Now we’ve got a great opportunity to study Chromera, and see how the malaria parasite has evolved. Hopefully, the traces of this once free-living algal past will give us new opportunities to design anti-malarial drugs."
Dr Nisbet’s team grows the malaria parasite and Chromera in the lab. The malaria parasites are grown in dishes containing donated human red blood cells (thanks to the Red Cross – and all blood donors), while Chromera grows in flasks of sea water.
"We’re looking at the DNA and proteins from each organism to see how they have changed, or evolved. We’re interested to see whether there is anything else that Chromera can do that the malaria parasite can’t." Dr Nisbet said.
"I’m also working with Dr Sally Plush, a chemist; and honours student, LeeKee Lau – they are designing new chemicals that we think might work against the malaria parasite. Soon we’ll get to try them out on the malaria parasites in the lab. Our hope is that they’ll work to kill the parasites."