No idle chatter: Study finds malaria parasites ‘talk’ to each other – It Changes everything

Contact: Liz Williams williams@wehi.edu.au 61-405-279-095 Walter and Eliza Hall Institute

Melbourne scientists have made the surprise discovery that malaria parasites can ‘talk’ to each other – a social behaviour to ensure the parasite’s survival and improve its chances of being transmitted to other humans.

The finding could provide a niche for developing antimalarial drugs and vaccines that prevent or treat the disease by cutting these communication networks.

Professor Alan Cowman, Dr Neta Regev-Rudzki, Dr Danny Wilson and colleagues from the Walter and Eliza Hall Institute in collaboration with Professor Andrew Hill from the University of Melbourne’s Bio21 Institute and Department of Biochemistry and Molecular Biology showed that malaria parasites are able to send out messages to communicate with other malaria parasites in the body. The study was published today in the journal Cell.

Professor Cowman said the researchers were shocked to discover that malaria parasites work in unison to enhance ‘activation’ into sexually mature forms that can be picked up by mosquitoes, which are the carriers of this deadly disease.

“When Neta showed me the data, I was absolutely amazed, I couldn’t believe it,” Professor Cowman said. “We repeated the experiments many times in many different ways before I really started to believe that these parasites were signalling to each other and communicating. But we came to appreciate why the malaria parasite really needs this mechanism – it needs to know how many other parasites are in the human to sense when is the right time to activate into sexual forms that give it the best chance of being transmitted back to the mosquito.”

Malaria kills about 700,000 people a year, mostly children aged under five and pregnant women. Every year, hundreds of millions of people are infected with the malaria parasite, Plasmodium, which is transmitted through mosquito bites. It is estimated that half the world’s population is at risk of contracting malaria, with the disease being concentrated in tropical and subtropical regions including many of Australia’s near neighbours.

Dr Regev-Rudzki said the malaria parasites inside red blood cells communicate by sending packages of DNA to each other during the blood stage of infection. “We showed that the parasites inside infected red blood cells can send little packets of information from one parasite to another, particularly in response to stress,” she said.

The communication network is a social behaviour that has evolved to signal when the parasites should complete their lifecycle and be transmitted back to a mosquito, Dr Regev-Rudzki said. “Once they receive this information, they change their fate – the signals tell the parasites to become sexual forms, which are the forms of the malaria parasite that can live and replicate in the mosquito, ensuring the parasites survives and is transmitted to another human.”

Professor Cowman said he hopes to see the discovery pave the way to new antimalarial drugs or vaccines for preventing malaria. “This discovery has fundamentally changed our view of the malaria parasite and is a big step in understanding how the malaria parasite survives and is transmitted,” he said. “The next step is to identify the molecules involved in this signalling process, and ways that we could block these communication networks to block the transmission of malaria from the human to the mosquito. That would be the ultimate goal.”

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This project was supported by the National Health and Medical Research Council of Australia, Howard Hughes Medical Research Institute and the Victorian Government.

Gene-swapping vaccines spawn lethal poultry virus – experts

Three vaccines used to prevent respiratory disease in chickens have swapped genes, producing two lethal new strains that have killed tens of thousands of fowl across two states in Australia, scientists reported on Friday.

The creation of the deadly new variant was only possible because the vaccines contained live viruses, even though they were weakened forms, said Joanne Devlin, lead author of the paper published in the journal Science.

Devlin and her team discovered how closely related the two new strains were with viruses in the vaccines after analysing their genes.

“What we found was the field viruses … were actually a mixture of the genomes from different vaccine viruses,” said Devlin, a lecturer at the University of Melbourne’s School of Veterinary Science. “They actually combined, mixed together.”

The viruses emerged in 2008, a year after Australia started using a European vaccine along with two very similar Australian vaccines to fight acute respiratory disease in poultry. The illness causes coughing, sneezing and breathing difficulties in birds, normally killing 5 percent of them.

The two new strains, however, were far more harmful, and since they were created have killed up to 17 percent of chicken flocks across Victoria and New South Wales, the two main chicken rearing states in Australia.

“What could have happened was one chicken was vaccinated with one vaccine and later was exposed to the other vaccine somehow, from nearby chickens,” Devlin said.

Agricultural authorities in Australia have been informed of the results of the study, and are considering how to prevent similar cross-overs happening again.

“Use of only one vaccine in a population of birds will prevent different viruses from combining,” Devlin said.

“Authorities are reviewing labels on vaccine to change the way vaccines are used and prevent different vaccines being used in one population.”