In particular, we have used in vitro live-cell imaging to demonstrate that cytotoxic CD8 + T cells from mice immunized with PyGAP can directly kill LS parasite-infected hepatocytes. In INCB28060 addition, antigen-specific CD8 + T cells have also been shown to correlate to protection induced by subunit vaccines. Immune responses elicited by vaccination with whole parasites are biased towards CSP; however, several studies have shown that protection against malaria parasites can be achieved in the absence of CSP. Despite these observations, few PE antigens other than CSP have been evaluated as vaccine candidates, including LSA1, CelTOS and TRAP. The identification of novel PE antigens is hindered by the difficult culturing of infected primary hepatocytes. A recent attempt to expand the repertoire of PE antigens characterized antigenspecific IFN-c production by splenic lymphocytes in CSP-tolerant mice immunized with irr spz. The authors concluded that although immunization with several non-CSP antigens generated large numbers of specific CD8 + T cells, only CSP was able to protect mice against challenge with wt spz. Ideal anti-infection malaria vaccines should target the silent preerythrocytic stages, blocking sporozoite invasion and/or subsequent development in the hepatocyte, hence preventing malaria infection and disease. In fact, the most effective malaria vaccines tested to date are all based on attenuated parasites. The use of immunization strategies that result in late LS or early BS arrest results in the development of immunity against a broad spectrum of antigens expressed by LS-infected hepatocytes and as consequence, in enhanced protection against sporozoite challenge. Human and mouse studies have shown that immunization with whole parasites elicits both humoral and T-cell responses, and that the bulk of this response is directed towards the immunodominant sporozoite surface protein CSP. Thus, subsequent boosts with whole parasites will repeatedly enhance the response to CSP, leading to significant reductions of hepatocyte invasion by spz and LS parasite load in the liver. As an unintended consequence, however, this immunization strategy prevents the development of robust T cell responses against non-CSP antigens expressed by LS parasites, perhaps explaining why extremely high doses of irr-spz are required in order to reach the peak of anti-CSP immunity that allows efficient inhibition of hepatocyte invasion by spz after challenge with wt P. falciparum spz. Although CSP-specific CD8 + T cell responses were induced by P. yoelii GAP in this study, CSP has been proven to be dispensable in C57BL/6 mice following vaccination with P. berghei sporozoites attenuated through irradiation, and was only marginally involved in protection of BALB/c mice immunized with P. berghei under chloroquine coverage. These results highlight the importance of identifying pre-erythrocytic antigens other than CSP that contribute to the protection elicited by attenuated whole parasite vaccines, which will be important in designing effective immunization strategies that result in a broad immune.