High-affinity TCRs confer antigen sensitivity in HIV gag-specific effector CD8 T cells (VAC7P.991)

Abstract

Abstract Virus infected cells are eliminated by CTLs when TCR recognizes viral Ag on MHC. Previously, we demonstrated that HIV-1-GAG specific high-affinity (ha) TCR enhanced CD8 T cell killing of HIV-1-infected cells. To elucidate why haTCR expressing T cells were better at controlling HIV-1 replication, we asked whether WT or haTCRs expressing primary human T cells had a distinct cytokine profile when stimulated with monomeric pMHC attached to magnetic beads. In this minimalistic T cell activation system, we observed robust IFNγ, TNFα, IL-2 and MIP1β induction in the presence or absence of CD28 stimulation. Interestingly, αCD3 coated beads do not induce cytokine expression. Previously, we and others demonstrated that αCD3 stimulation failed to induce AKT activation, which has a prominent role in cytokine production. Here, TCR signaling alone activates AKT. Next, we addressed whether T cells expressing haTCRs were able to respond to less Ag, and thereby control HIV-1 replication better by destroying HIV-1 infected cells before they could effectively spread the virus. By mixing various ratios of cognate pMHC with non-cognate pMHC on magnetic beads, we show that CD8 T cells, and not CD4 T cells, expressing haTCRs are able to induce Ag specific activation of phospho-ERK1/2 and -AKT with a ~10 fold increased sensitivity when compared with WT TCR expressing T cells. Thus, implicating CD8 as playing an important role in regulating how a T cell perceives differences in TCR affinity.