Studies of experimental malaria interventions have long relied on a tried-and-true method of causing malaria infections in healthy volunteers by subjecting them to bites from mosquitos infected with Plasmodium falciparum parasites. But results from a preliminary study presented at the American Society of Tropical Medicine and Hygiene in November suggest that injections of purified cryopreserved P falciparum sporozoites may also do the trick.
The phase I study, simultaneously published in the American Journal of Tropical Medicine and Hygiene (Roestenberg M et al. Am J Trop Med Hy. doi: 10.4269/ajtmh.2012.12-0613 [published online November 13, 2012]), involved 18 Dutch volunteers divided in 3 groups that received intradermal injections of 2500, 10 000, or 25 000 sporozoites. The sporozoites were produced by Sanaria, a biotechnology company, which raised infected mosquitos under aseptic conditions, purified the sporozoites from mosquito tissues, and preserved them in vials for injection. A total of 15 of 18 volunteers became infected with malaria, 5 of 6 in each inoculum group, with no observed differences in measures of infection between groups. All infected individuals were treated and recovered. Several reported headaches, likely due to the malaria infection, and 1 individual reported chest pain after malaria treatment. The trial was stopped while the trial's safety monitoring committee assessed the chest pain event, which was determined not to be a serious cardiac event, and the trial was resumed 3 days later, the authors noted.