Human models injected with malaria parasites via simple jab
Scientists have, for the first time ever, infected human volunteers with malaria via a simple injection of cryopreserved sterile parasites that were harvested from the salivary glands of infected mosquitoes in compliance with regulatory standards.
The parasites had been frozen in a vial for more than two years.
This breakthrough could accelerate malaria vaccine and drug development, said scientists.
The established gold standard for deciding whether or not to proceed with the development of a new malaria drug or vaccine is known as a "human challenge" trial, in which volunteers exposed to the vaccine or experimental drugs are deliberately subjected to bites from infected mosquitoes.
The findings from this study indicate that direct injection of cryopreserved parasites can be used in lieu of mosquito bites.
The findings from this study eventually could lead to a powerful tool for testing promising malaria drugs and vaccines in trials that involve deliberately exposing subjects to a "controlled human malaria infection" (CHMI), said researchers at Radboud University Medical Center in the Netherlands and their colleagues from Sanaria Inc. and Protein Potential LLC at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH).
Also, they said the injectable formulation of malaria parasites might be considered, by itself, as part of a novel approach to providing protection against a disease that each year kills at least 650,000 people, most of them young children in Africa.
"Our study shows it's possible to manufacture and then administer controlled doses of malaria parasites using a needle and syringe to deliver a formulation that can meet regulatory standards for purity and dose consistency," said Meta Roestenberg, MD, of the Radboud University Nijmegen Medical Center and the lead author of the study along with Else M. Bijker, MD.
In a controlled human malaria infection trial, conducted at Radboud University Medical Center from October 2010 to July 2011, researchers injected eighteen healthy Dutch volunteers with cryopreserved Plasmodium falciparum malaria sporozoites (PfSPZ Challenge).
The study showed that 84 percent of participants - five of the six volunteers in each group - were safely and successfully infected with no differences among the groups in the time it took for the infection to develop or the presentation of symptoms. The volunteers who developed infections subsequently received treatment and quickly recovered without incident.
The authors of the study said that the results could provide evidence for developing what are known as "whole parasite" vaccines.
Robert W. Sauerwein, MD, PhD, of Radboud University Medical Center said that the new study showing that infections could be accomplished with a simple shot in the arm could make the whole parasite approach more feasible.
The findings have been published online in the American Journal of Tropical Medicine and Hygiene and will be published in the January 2013 print issue.