Retrieving parasite specific liver stage gene products in Plasmodium yoelii infected livers using differential display.

Differential display (DD) has been routinely used to identify genes whose expression pattern is altered by changes in the cellular environment and/or at different stages of development. Most reports utilizing DD contain conventional DD primers that have high guanine and cytosine content and would not be expected to be optimal for Plasmodium which has approximately 30-40% G+C. In an attempt to accommodate the high adenine and thymidine rich genome of Plasmodium yoelii, we utilized PCR primers containing 40, 50 and 60% G+C and modified the existing DD technique. Thus 40% G+C appeared to be the most suitable to amplify Plasmodium genome. Gene specific primers were generated from the sequences of selected DD bands amplified using the 40% G+C primers and were used to verify that the DD clones were of parasite origin by PCR and sequence alignment. Additional data on five of the selected DD clones, designated P2T1L5, P2T1L6, P2T6L11, P2T7L12 and P2T7L13, suggested that all are expressed during the P. yoelii liver stage infection. Interestingly, P2T1L5 is also expressed during the sporozoite stage of the life cycle and both P2T1L6 and P2T6L11 are present as blood stage antigens. The results of this study suggest that DD incorporating primers with low G+C content allows the identification of P. yoelii messages from infected mouse livers.