Visualization of malaria parasites in the skin using the luciferase transgenic parasite, <i>Plasmodium berghei</i>

ABSTRACT

Weproduced a transgenic rodent malaria parasite (<i>Plasmodium berghei</i>) that contained the luciferase gene under apromoter region of elongation factor-1α. These transgenic (TG) parasites expressed luciferase inall stages of their life cycle, as previously reported. However, we were the firstto succeed in observing sporozoites as a mass in mouse skin following theirdeposition by the probing of infective mosquitoes. Our transgenic parasites mayhave emitted stronger bioluminescence than previous TG parasites. The estimatednumbers of injected sporozoites by mosquitoes were between 34 and 775 (median 80). Since luciferase activity diminished immediately after the death of theparasites, luciferase activity could be an indicator of the existence of liveparasites. Our results indicated that sporozoites survived at the probed sitefor more than 42 hours. We also detected sporozoites in the liver within 15 minof the intravenous injection. Apart from the liver, bioluminescence was notobserved in the lung, kidney, or spleen. We reconfirmed that the liver was thefirst organ for malaria parasites to enter and increase in number.