Work

Genetic Modification of Antigen-Specific Cytotoxic T Lymphocytes (CTLS) Restores Their Ability to Respond to Interleukin-7 (IL-7)

Year: 2009

Type: article

Abstract: Adoptive transfer of tumor-specific cytotoxic T lymphocytes (CTLs) can induces tumor regression in patients with several types of lymphomas. Clinical responses appear to require the in vivo expansion and persistence of the infused CTLs so that IL-2 has frequently been used to support CTL therapies. Although effective, IL-2 is associated with significant toxicity and the expansion of regulatory T cells (Treg). Thus alternative cytokines able to sustain the expansion of CTLs but avoiding the toxic and negative effects of IL-2 are highly demanded. IL-7 plays a crucial role in T-cell homeostasis, appears well tolerated, and does not influence Treg numbers or function. Unfortunately, IL-7 may fail to expand tumor-specific CTLs in vivo because these cells lack IL-7Ra expression. To determine whether forced expression of transgenic IL-7Ra improves CTL survival and expansion we used Epstein-Barr-Virus specific-CTLs (EBV-CTLs) which we transduced with a retroviral vector encoding IL-7Ra. After transduction, IL-7Ra was detectable on 58–76% of EBV-CTLs. The transgenic IL-7Ra molecule was functional since addition of IL-7 induced STAT5 phosphorylation only in EBV-CTLs/IL-7Ra+. These EBV-CTLs/IL-7Ra+ and control CTLs expanded equally in response to IL-2, but only EBV-CTL/IL-7Ra+ significantly proliferated in the presence of IL-7 (5 ng/mL) [from 1 × 106 to 1.03 × 108 cells/ml (range, 0.38–2.9 × 108)] over five weeks of culture. As anticipated, the EBV-CTL/IL-7Ra+ subset of cells were selected on exposure to IL-7 and so formed an increasing proportion of the total T cell population. Importantly, IL-7 expanded EBV-CTLs/IL7Ra+ retained their ability to respond to other common-g-chain cytokines such as IL-2 and IL-15, and did not modify their antigen specificity measured by tetramer staining and by IFNg release. These CTLs also remained polyclonal, retaining both their effector-memory profile and MHC-restricted killing of autologous LCLs. Antigen or cytokine withdrawal abrogated CTL expansion. These in vitro characteristics were replicated in a xenograft mouse model, in which EBV-CTLs/IL7Ra+ expanded in response to IL-2 or IL-7 and maintained their antitumor effects. In conclusion, we have developed a novel approach to safely expand adoptively transferred CTLs using IL-7. This approach can be beneficial for CTL therapies in patients with lymphomas and other malignancies.

Source: Transplantation and Cellular Therapy

DOI: 10.1016/j.bbmt.2008.12.070