Noninvasive real-time monitoring of liver-stage development of bioluminescent Plasmodium parasites.
BACKGROUND
The morbidity and mortality associated with malaria are heightened because of the spread of drug-resistant parasites and the lack of an effective vaccine. Plasmodium liver stages are the targets of new chemotherapeutics and vaccines, but there are limited tools available to study this stage in vivo.


METHODS
To overcome this obstacle, we developed a method with which to study Plasmodium liver stages by means of bioluminescent imaging (BLI) of the rodent malaria parasite Plasmodium yoelii. We created a P. yoelii YM strain (PyLuc) that stably expresses firefly luciferase driven by a constitutive promoter.


RESULTS
Using BLI, we performed imaging of the Plasmodium liver stages of mice infected with PyLuc sporozoites and monitored parasite dissemination during blood-stage infection. Because PyLuc luciferase activity is proportional to the number of parasites, BLI can be used to quantify the effect of drugs on liver-stage development. Moreover, using BLI, we demonstrated that immunization with blood-stage parasites confers partial protective immunity against the development of liver stages.


CONCLUSIONS
BLI is a noninvasive technique that is useful for screening potential drugs and candidate vaccines with which to combat malaria. The prospect of cross-stage protective immunity increases the number of avenues to be explored in the development of an effective vaccine against malaria.
Mwakingwe
Agnes
A
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Ting
Li-Min
LM
Hochman
Sarah
S
Chen
John
J
Sinnis
Photini
P
Kim
Kami
K
D000818:Animals; D030801:Animals, Genetically Modified; D004195:Disease Models, Animal; D005260:Female; D049452:Green Fluorescent Proteins; D008099:Liver / Q000469:parasitology*; D008156:Luciferases; D008288:Malaria / Q000469:parasitology*; D052940:Merozoites; D051379:Mice; D018512:Parasitemia; D010967:Plasmodium yoelii / Q000254:growth & development / Q000302:isolation & purification*
D049452:Green Fluorescent Proteins; D008156:Luciferases