Blood-Stage Plasmodium berghei Infection Generates a Potent, Specific CD8+ T-Cell Response Despite Residence Largely in Cells Lacking MHC I Processing Machinery

Murine cerebral malaria is a complex disease caused by Plasmodium berghei ANKA infection. Several cell types, including CD8(+) T cells, are essential effectors of disease. Although the use of transgenic parasites expressing model antigens has revealed the induction of cytotoxic T lymphocytes (CTL) specific for these model antigens, there is no direct evidence for a response to authentic blood-stage parasite antigens, nor any knowledge of its magnitude. Our studies show that there is a dramatic primary parasite-specific CTL response, akin to viral immunity, reaching approximately 30% of splenic CD8(+) T cells, with many producing interferon-gamma and tumor necrosis factor-alpha. These cells express granzyme B and other markers of specific responders, are cytolytic, and respond to a broad array of major histocompatibility complex (MHC) I-restricted epitopes, 5 of which are identified here. Our studies indicate that vigorous CTL responses can be induced to pathogens even when they largely reside in red blood cells, which lack MHC I processing machinery.