IL-2 functionalized hydroxyethylstarch nanocapsules for targeting of human T cells with different IL-2 receptor affinities in vitro and in vivo

Cell type specific delivery of drugs by use of nanocapsules (NC) is a promising approach for induction of efficient anti-tumor immunotherapies. Here, we report the generation of IL-2 functionalized NC (HES-IL-2) to target CD25+ (IL-2 receptor α chain) T cells. In flow cytometry experiments HES-IL-2 exhibited an enhanced uptake by human CD25+ T cells compared to control capsules. The observed uptake was CD25 specific as CD25high T cells displayed a significantly enhanced NC incorporation compared to CD25− T cells with negligible internalization. In addition blocking of the IL-2 receptor dependent binding by an anti CD25 mAb significantly reduced the HES-IL-2 uptake by human CD25+ T cells. Furthermore, comparing and competitive studies of naïve CD25−, activated CD25+ and regulatory CD25high human T cells revealed a low incorporation of HES-IL-2 in naïve and a moderate and high uptake, respectively in activated or regulatory T cells. Additionally, in order to preferentially address different T cell populations by means of various IL-2 receptor affinities, we generated HES-IL-2 with distinct reduced amounts of IL-2 on their surface. Intriguingly, in contrast to naïve CD25− and activated CD25+ T cells, in which the NC uptake was clearly IL-2 dose-dependent we did not observe any differences when HES-IL-2 with a twofold and tenfold decreased amount of IL-2 were used for studies with regulatory CD25high T cell, indicating a high IL-2 sensitivity of regulatory T cells for a specific targeting. In addition, in vivo studies in human T cell reconstituted RAG2−/−γc−/− mice exhibited a significantly enhanced uptake of HES-D-IL-2 by CD25+ T cells. In summary, we generated IL-2 functionalized NC for targeting of human CD4+CD25+ T cells in vitro and in vivo.