Due to the growing burden of malignancy and chronic infections, manipulating CD8+ T cell responses for clinical use has become an important goal for immunologists. CD8+ T cells have the unique capacity to recognize and kill tumor cells and intracellular pathogens. Thus far, failed or only minimally effective T cell vaccines against chronic pathogen infections and tumors have highlighted basic knowledge gaps for eliciting memory CD8+ T cell protection. Defining the immunological mechanisms that determine protective capacity and longevity in T cells will be critical to both therapeutic and prohylactic vaccine efficacy. My studies focus on strategies to manipulate effector and memory CD8+ T cell responses, including their mechanisms of action. Specifically, I show that dendritic cell (DC) immunization coupled with relatively early (days 1-3) or late (days 4-6) administration of enhanced IL-2 signals drive either effector or memory programs. DC + IL-2c administered 4-6 days post-DC transfer is shown to enhance Ag-specific effector CD8+ T cell responses; this approach is further explored in the context of a cancer immunotherapy, demonstrating effective control of tumor burden in multiple murine models of cancer. Temporal alterations of IL-2 signaling from day 4-6 to day 1-3 post-DC immunization is shown to increase memory potential and memory CD8+ T cell numbers long-term. Additional studies reveal CTLA-4-mediated down-regulation of B7-ligands on DCs after IL-2c treatment, demonstrating that weaker or more transient signaling through the CD28-B7 axis may favor memory CD8+ T cell programs. My work contributes valuable concepts in memory CD8 T cell generation to develop T cell vaccines that are both safe and predictable.

Biological activity of IL-2 and IL-7 in vivo is significantly increased when complexed with some of the respective anti-cytokine mAb. Different immune cell subsets can be preferentially stimulated depending on the anti-IL-2 mAb used to complex IL-2. IL-2/anti-IL-2 mAb S4B6 immunocomplexes (IL-2/S4B6) induce preferential expansion of CD122high cells whereas IL-2/anti-IL-2 mAb JES6-1 immunocomplexes (IL-2/JES6-1) highly selectively stimulate CD25high cells in mice. Similarly, IL-7/anti-IL-7 mAb M25 immunocomplexes (IL-7/M25) possess higher stimulatory activity for both naïve and memory CD8+ T cells in vivo in comparison to free IL-7. CTLA-4 and PD-1 molecules are inhibitory receptors which negatively regulate proliferation, survival and effector functions of T cells. Blocking antibodies against these molecules represent promising immunotherapeutic tool for treatment of malignant diseases. We examined possible synergism of IL-2/S4B6 and αCTLA-4 plus αPD-1 mAbs in tumor-bearing mice. We found that the expansion of recently activated CD8+ T cells driven by IL-2/S4B6 was further augmented by αCTLA-4 plus αPD-1 mAbs. However, these two immunotherapeutic approaches did not show synergistic antitumor activity in any mouse tumor model tested. Next, we showed that IL-7/M25 possessed higher biological activity...

5 Abstract Interleukin-2 possesses strong stimulatory activity for activated T and NK cells and thus it is an attractive molecule for immunotherapy. However, its unfavourable pharmacological properties, extremely short half-life and severe toxicities associated with high-dose IL-2 are the most serious and limiting drawbacks. Moreover, IL-2 has been also implicated in the homeostasis of T regulatory cells where it plays a decisive role as an essential growth factor of these cells. Several different approaches to improve the therapeutic potential of IL-2 have been studied. Recently described IL-2/anti-IL-2 mAb immunocomplexes which show much higher and selective biological activity in contrast with free IL-2 in vivo are probably the most promising of them. In this study, we compared the biological activity of free IL-2 with IL-2/anti-IL-2 mAb immunocomplexes in order to demonstrate their benefits over free IL-2. We also demonstrated that IL-2/anti-IL-2 mAb immunocomplexes possess noticeable antitumor activity in two syngeneic mouse tumor models, namely EL4 T lymphoma and B16F10 melanoma, if administered early in tumor progression. Therefore, we justified potential use of IL-2/anti-IL-2 mAb immunocomplexes in tumor immunotherapy. We covalently conjugated IL-2 to synthetic semitelechelic polymeric carrier based...