Delivery of IL-2 to the T Cell Surface Through Phosphatidylserine Permits Robust Expansion of CD8 T Cells

Abstract

The phospholipid phosphatidylserine (PS) is naturally maintained on the cytoplasmic side of the plasma membrane. Independent of apoptosis, PS is redistributed to the surface of CD8 T cells in response to TCR-mediated activation. Annexin V (AnnV) is a protein known to bind PS with high affinity and has been effectively utilized to anchor antigen to the surface of CD8 T cells. To expand these studies, we aimed to exploit TCR activation driven PS exposure as a target to deliver cytokine, namely interleukin-2 (IL-2), to the surface of CD8 T cells. This was accomplished using a novel chimeric fusion protein of annexin V and interleukin 2 (AnnV-IL2). In vitro analysis revealed that AnnV-IL2 is able to specifically bind PS on the T cell surface following TCR stimulation. Consequently, AnnV-IL2 proved to be significantly more effective at enhancing T cell activation compared to recombinant IL-2. In vivo, AnnV-IL2 promotes robust expansion of antigen-specific cells capable of interferon gamma (IFNγ) production when administered following peptide vaccination. Importantly, upon antigen rechallenge, AnnV-IL2 treatment mice demonstrated a stronger secondary expansion, indicating durability of AnnV-IL2 mediated responses. Our data supports the use of AnnV-IL2 to modulate antigen-specific T cell immunity and demonstrates that the PS-AnnV axis is a feasible mechanism to target diverse cargo to CD8 T cells.

Integrin Targeting Enhances the Antimelanoma Effect of Annexin V in Mice

“…A strategy relying on TP8 to enhance TRAIL resistance properties appears to be feasible, but the study did not clarify whether TP8 targets tumor tissues. Another study showed that the fusion protein ANV-IL2 was more effective in enhancing T-cell activation than recombinant IL-2 because interleukin-2 (IL-2) carrying ANV could deliver IL-2 to the surface of CD8 T cells where transient rearrangement of phospholipids occurred [ 34 ]. This finding suggests that the ANV fusion protein is an effective way to target PS, and, with the help of the high affinity of ANV for PS, ANV could play a role in tumor therapy as well as in the immune response.…”