Detecting T-cell reactivity to whole cell vaccines

Abstract

BCR-ABL + K562 cells hold clinical promise as a component of cancer vaccines, either as bystander cells genetically modified to express immunostimulatory molecules, or as a source of leukemia antigens. To develop a method for detecting T-cell reactivity against K562 cell-derived antigens in patients, we exploited the dendritic cell (DC)-mediated cross-presentation of proteins generated from apoptotic cells. We used UVB irradiation to consistently induce apoptosis of K562 cells, which were then fed to autologous DCs. These DCs were used to both stimulate and detect antigen-specific CD8 + T-cell reactivity. As proof-of-concept, we used cross-presented apoptotic influenza matrix protein-expressing K562 cells to elicit reactivity from matrix protein-reactive T cells. Likewise, we used this assay to detect increased anti-CML antigen T-cell reactivity in CML patients that attained long-lasting clinical remissions following immunotherapy (donor lymphocyte infusion), as well as in 2 of 3 CML patients vaccinated with lethally irradiated K562 cells that were modified to secrete high levels of granulocyte macrophage colony-stimulating factor (GM-CSF). This methodology can be readily adapted to examine the effects of other whole tumor cell-based vaccines, a scenario in which the precise tumor antigens that stimulate immune responses are unknown.

Pilot trial of K562/GM-CSF whole-cell vaccination in MDS patients

“…GM-CSF attract dendritic cells (DCs) to the site of vaccination, and increases costimulatory signals for antigen presentation. [29,38] Secretion of cytokines by activated DCs may have enhanced innate immune responses by cell populations such as macrophages that would not be captured in our assays but may have ultimately contributed to the clinical activity of the vaccine.…”

Genetically engineered fixed K562 cells: potent “off-the-shelf” antigen-presenting cells for generating virus-specific T cells

“…K562 expresses a variety of tumor and leukemia associated antigens (34, 35) including WT1(36), PRAME (37), and proteinase 3 (35), which are overexpressed in myeloid leukemia cell _enref_6_enref_2 s. Compared with NIH 3T3 cell, which are also used for aAPC cells, a potential advantage of the K562 aAPC is the possibility that it can naturally present a variety of myeloid leukemia specific antigens through the inserted MHC molecules, making it an attractive candidate for inducing leukemia-specific APC. Indeed, irradiated K562 cells have been used for vaccination in CML patients (38, 39). Our aAPC could also be modified to express other leukemia associated antigens by gene transduction.…”

Immunotherapy for Breast Cancer: Current and Future Strategies

“…Once tumor cells are killed and phagocytized, their entire library of antigens, including antigens that have not yet been identified, can be presented to naïve T cells. The benefit of developing multiple tumor antigen targets simultaneously is that it decreases the likelihood of tumor evasion by down-regulating expression of one specific antigen [34]. Anti-tumor effects of whole-cell vaccines in animal models have been further improved with concurrent chemotherapy [33], highlighting the benefits of vaccination in combination therapies.…”