Inhibition of Liver-Stage Development Assay

In vitro infection of hepatocyte monolayer cultures with plasmodial sporozoites has become a valuable tool for the dissection of host-cell parasite interactions (1 -4 ). This methodology has facilitated the study of how antibodies, cytokines, drugs, and immune effector cells can influence the infection of hepatocytes with plasmodial parasites. In vitro cultures have the advantage of allowing an investigator to isolate hepatocytes from nonparenchymal cells, thus avoiding any confounding of the results that might occur due to an interaction of the test conditions with nonparenchymal cells (kupffer cells, endothelial cells, lymphocytes, etc.). Several different types of inhibition of liverstage development assay (ILSDA) procedures can be utilized. They fall into two different categories: blocking entry of the parasite into the hepatocyte or inhibiting development of the liver stage schizont after infection. The first procedure is used to determine if immune sera can prevent the entry of parasites into the hepatocytes, while the other can be used to assess the capacity of sera, immune effector cells or drugs to affect the development of the intracellular liver stage parasite. Because these assays are assessing different aspects of the host-parasite relationship, the practical aspects of these tests are slightly different.