Could Vaccines Breed Super-Virulent Malaria? | PLOS BiologuePosted: August 6, 2012
Read insists that there’s no telling how malaria parasites will evolve in response to vaccination in the human trials. In the paper, Read and his coauthors call for “extreme caution” in extrapolating their results to humans, noting that generalizing from animal models is notoriously difficult in malaria. “We don’t know what might happen,” says Read. “My point is we need to figure it out.”
And that’s no trivial task. For Read, the first step in evaluating the “evolutionary risk” of vaccines is to collect data on the parasites to look for genetic differences between those found in vaccinated and unvaccinated individuals. If people are still transmitting parasites after vaccination, it would be important to monitor those parasites to figure out why they survived. It could be because of changes in proteins targeted by the vaccine. Or it could be because the parasites reproduce more aggressively, which means they could become more virulent.
One thing that would help vaccine developers figure out how to apply results like these from preclinical models to human malaria is insight into any genetic changes associated with increased virulence. “Understanding the changes at the molecular level would be valuable for us to better understand how to most effectively use data like this,” says Ashley Birkett, director of research and development at PATH Malaria Vaccine Initiative, a partner in the RTS,S phase III clinical trial.