Session: Poster Session: Malaria and Babesia
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: Sequestration of infected red blood cells (iRBCs) in malaria infection in humans causes significant pathology, including organ damage, coma and death. We standardized a less invasive method of studying sequestration and host-parasite interactions by obtaining bioluminescent in vivo imaging of malaria infection in mice. Methods: We used Plasmodium yoelii, a rodent malaria model that sequesters in microvasculature similar to P. falciparum in humans. P.yoelii YM, a lethal strain, was transfected with a plasmid containing a GFP-luciferase fusion protein driven by a constitutive promoter. Groups of 5 Swiss Webster mice were injected with 1 x 104 iRBC of GFP-Luciferase transgenic P. yoelii (PyLuc) or 1 x 104 iRBC of P. yoelii YM wild type (PyWT) via tail vein. On days 3, 5 and 7 blood smears were made for parasitemia count. Mice were injected by tail vein with the luciferase substrate D-luciferin (120 mg/kg). Bioluminescence was detected by an intensified-charge-coupled device photon-counting video camera (IVIS 100, Xenogen) over 60 seconds. Living Image software (Xenogen) was used to quantify bioluminescent data. PyLuc-infected mice not injected with D-luciferin and PyWT-infected mice were used as negative controls. Results: PyLuc luminesced and luciferase activity of blood was proportional to parasitemia. PyLuc had similar virulence as PyWT in mice. Bioluminescence was detected on day 3 of infection (parasitemia as low as 0.12%) with sequestration noted in the lungs. Mice at this stage show no outward signs of infection. By day 7, mice had parasitemias greater than 80%. Sequestration at this late stage of infection was observed in lungs, liver and spleen. Mice at this stage of infection huddle together, are less active and pass blood in their urine. Conclusions: Bioluminescent detection of light produced by the reaction of Luciferase with D-Luciferin from PyLuc can be used to monitor parasite infection in mice. Real time in vivo imaging of iRBCs provides insights into the dynamics of sequestration and its role in disease pathophysiology.