The success with cell-free protein expression suggest that this system could be also applied to cellular screening, to identify antigenic targets of T cell responses from genomic sequence data. However, this has not yet been adequately explored despite that T cells play a central role in orchestrating acquired immunity against infectious diseases [41, 42] . Both CD8 + and CD4 + T cells can mediate their effector function directly via cytotoxicity or indirectly via cytokines. CD4 + T cells can also provide help for CD8 + T cells or can recruit and activate B cells for antibody secretion. To date, the only reports have been restricted to measurement of proliferative T cell responses in PBMCs of smallpox vaccines or of cattle immunized with a purified Anaplasma marginale outer membrane preparation to a small number of IVTT produced vaccinia virus proteins or outer membrane proteins, respectively [18, 19, 43] . Neither of those studies comprehensively assessed and optimized the application of IVTT products for large-scale or proteome-wide cellular screening. Accordingly, herein, we report proof of concept for the potential of this approach a strategy for proteome-wide identification of antigens targeted by cell mediated immunity in both viral and parasite models, using IVTT products with specimens from human and mice.