Development of efficient tools for analysis of the host -parasite interaction during the liver stages of malaria infection

Abstract

The morbidity and mortality due to malaria is rising as a result of the emergence and spread of drug resistant parasites and the lack of an effective vaccine. Development of novel intervention strategies is hindered by the lack of efficient tools available to study liver stage parasites in vivo . Development of Plasmodium parasites in the liver is the first and obligatory step in its life cycle in the vertebrate host. Although a clinically silent infection, development of parasites in the liver is an immunologically active stage leading to protective immunity. It is thus imperative that we develop novel tools to study the biology of Plasmodium liver stages.;First, to study sporozoites-hepatocytes molecular interactions, we adapted transfection of mouse hepatocytes by hydrodynamic tail vein injection to deliver naked DNA to hepatocytes in vivo. Transfection by hydrodynamic injection can lead to creation of disease models and non-heritable transgenic research animals within a short time. With further optimization of experimental conditions, transfection by hydrodynamic injection is a promising invaluable tool to study molecular interactions between sporozoites and hepatocytes in vivo.;Second, for thorough screening of factors that affect liver stage parasite growth, we adapted bioluminescent imaging (BLI) of P. yoelii YM expressing firefly luciferase (PyLuc). BLI is a non-invasive and rapid technique that allows for real-time monitoring of infection in the same animal. Using BLI, for the first time, in vivo liver stage parasites were imaged after infecting mice with PyLuc sporozoites and effects of drugs and immunization on this stage were quantified. BLI allows for efficient analysis of effects of chemotherapeutic or vaccine candidates on liver stages.;Successful efforts to combat the devastation of malaria require understanding of how the parasite and host interact during infection. It is not entirely clear how the Plasmodium parasites establish infection, and how the host immune system responds to parasites. We have adapted transfection by hydrodynamic injection and bioluminescent imaging as important tools to study parasite biology in vivo. These important tools will help to better understand parasite biology thus leading to generation of effective intervention strategies to reduce the morbidity and mortality caused by malaria.