Antigenic variation during malaria infection--the contribution from the murine parasite Plasmodium chabaudi.

P. chabaudi AS strain in laboratory mice provides an accessible and useful model for investigating antigenic variation in malaria parasites. Evidence that P. chabaudi AS undergoes antigenic variation is summarized. A live indirect fluorescent test (IFAT) detects a variable antigen on the surface of schizont-infected erythrocytes. Five different variable antigen types (VATS) (detected using the live IFAT) are described from a cloned mosquito transmitted parent population. Even during the rising primary parasitaemia VATS switch at high and variable rates (1.2-1.6%). Work towards cloning genes coding for the variable antigen is briefly summarized. Acquired immunity to blood-stage P. chabaudi AS is initially mediated through Th1 CD4+ T cells and after the primary parasitaemia there is a switch to Th2 CD4+ T cells. Acquired immune effector mechanisms are discussed in the context of antigenic variation by the parasite.