Queensland researchers are behind the development of a new clinical trial model for testing drugs and vaccines designed to stop malaria from spreading.
QIMR Berghofer Medical Research Institute scientists have designed a safe clinical trial model to test the effectiveness of efforts to stop the spread of malaria parasites from humans to mosquitoes.
The clinical trial model safely infects healthy volunteers with malaria, then uses a drug that kills the malaria parasites that make people sick. The drug does not affect the form of the parasite transmitted to the mosquito when it bites a person, which allows researchers to test the transmission of malaria from humans to mosquitoes.
QIMR Berghofer’s Infectious Diseases Program Coordinator, Professor James McCarthy, and Dr Katharine Collins developed and tested the model, with their findings recently published in The Journal of Clinical Investigation.
“Strategies to treat malaria infection and to prevent people from being bitten by mosquitoes, such as bed nets, have had a noticeable impact on reducing the global burden of disease,” Dr Collins said.
“However, progress has recently stalled and, if we want to eliminate malaria altogether, in addition to treating people when they are sick, we also need to reduce the spread of malaria parasites from humans to mosquitoes and back again.
“That’s why we have developed a clinical trial model that will allow drug and vaccine developers to specifically test for the transmission of malaria parasites from humans to mosquitoes in small pilot studies.”
Professor McCarthy has already developed a clinical trial model that safely tests the effectiveness of drugs that treat malaria infection, which has accelerated the development of new treatments.
But Dr Collins said until now, there has been no model that allowed for early assessment of the effectiveness of new drugs or vaccines in stopping malaria transmission, drastically slowing down progress in developing such interventions.
She said infected people usually only became capable of transmitting malaria to mosquitoes about a week after their symptoms began to show and they became sick.
Dr Collins said a person would become sick with malaria around a week after they were bitten by an infected mosquito, when the parasites were released into the blood stream from the liver. However, she said the form of the malaria parasite that could be transmitted to mosquitoes – the gametocytes – would only be present in the blood stream about one to two weeks after this.
“If a mosquito bites you when you have this form of the malaria parasite in your blood, it will take up the gametocytes and these will develop in the mosquito for about two weeks. At this point the mosquito can then potentially transfer the parasites on to the next person it bites,” she said.
She said it was vital that clinical trial models were developed to ensure that drugs and vaccines that aim to prevent malaria transmission could be safely, and quickly, tested.
“This is the first time anyone has shown the transmission of malaria from humans to mosquitoes using a safe controlled human malaria infection clinical trial model,” Dr Collins said.
“Once it is put into practice, it will allow us to accelerate the development of new drugs and vaccines targeting the spread of the disease from humans back to mosquitoes.”
Dr Collins, who is now affiliated with Radboud University Medical Centre in the Netherlands, said the study was “a great step forward” in the development of a model that could aid in the fight against malaria.
Malaria is a mosquito-borne virus that is estimated to have killed more than 445,000 people around the world in 2016.
The QIMR Berghofer-led research was backed by funding from the Bill and Melinda Gates Foundation, Medicines for Malaria Venture and the Malaria Vaccine Initiative.
The trials are will take place at QIMR Berghofer’s wholly-owned clinical trials company Q-Pharm Pty Ltd.