Cell therapy, an innovative way of treatment
Application example for MHC technologies
Cell therapy and immunomodulation, innovative ways of treatment
Immunotherapies that stimulate a patient’s own immune system and cell therapy, which is defined as the administration of cells that are either therapeutic effector cells to treat a disease or cells supporting other therapies, have evolved rapidly over the past decades.
They have proven to be successful in the treatment of many diseases and it is expected to hold enormous promise for future therapeutic strategies. Besides the established haematopoietic stem cell transplantation, many new and innovative cell therapies are evolving and their efficacy is currently assessed in various clinical trials.
Two strategies of immunotherapy
Immunotherapy is a highly active and promising area in the field of cell therapy that is progressing rapidly. The potential of immunotherapy is increasingly recognised in the field of oncology, but also in other disease areas as autoimmune diseases, (chronic) infections, transplantation and allergy this form of therapy is exploited.
Within immunotherapy, two strategies can be distinguished:
1. Active immunisation or vaccination is broadly used to fight viral infections, but is also applied in for example cancer therapy. Recently immunomodulatory therapies are also becoming successful, designed to stimulate one’s immune system to fight cancer cells.
2. Passive immunisation includes adoptive T cell therapy, in which the T cells are harvested from a patient or donor followed by isolation of specific T cells, expansion and/or modification in the lab followed by (re-)infusion into the patient.
In the past decades, substantial evidence has been collected showing that T cells indeed can help to control tumour growth.
Several trials with patients bearing solid tumours have provided evidence for (partial) antitumour immune response by adoptive transfer of tumour-specific T cells. In addition, it has been demonstrated that a specific subset of leukaemia patients experiencing relapse after stem cell transplantation, could be cured from their disease by transfusion of donor-derived T cells (a donor lymphocyte infusion (DLI)).
T cell clones
The advances in T cell isolation, culture technology and the increasing knowledge of T cell responses to viruses have made it possible to produce viral antigen-specific T cell clones. These are intended for clinical application in immunocompromised patients. Indeed, adoptive transfer of virus-specific T cells lead to virus clearance in patients who had received a stem cell transplantation (SCT). More recently, T cell receptors (TCR) and chimeric T cell receptors (CARs) show enormous promise in the oncology field.
New antigens needed
Although promising, adoptive T cell therapy is still challenging. In solid tumours the immune escape of tumour cells remains problematic, while DLI often faces unwanted severe graft-versus-host responses. Likewise, viruses have developed several strategies to evade recognition and/or killing by the T cells, which can make T cells of particular specificities less effective in clearing the viral infection.
Identification of new antigens recognised by T cells is therefore indispensable to improve current immunotherapy regimens.
Process of selecting relevant new antigens
Finding the right peptides presented by MHC molecules is essential for identifying new T cell antigens. A major first step in the identification of disease-specific T cells is to calculate MHC-peptide binding with a computer-based prediction algorithm. Subsequently, MHC-peptide binding of the proposed high affinity binding peptides has to be confirmed by production of the MHC class I tetramer. Finally, biological relevance can be determined by staining of antigen-specific CD8+ T cells. Clearly, this process is often laborious and time consuming which makes it inappropriate for high-throughput screening. Our proprietary technology has solved this.
A close collaboration between Sanquin and the Netherlands Cancer Institute (NCI) resulted in the development of two innovative technologies that in combination provide a state-of-the-art tool for high-throughput T cell epitope discovery.
Simultaneous identification and production
The UV-induced peptide exchange protocol enables parallel identification and production of multiple MHC-peptide complexes, substituting the prediction algorithm and the laborious MHC tetramer production. This technique facilitates performing extensive MHC-peptide binding studies within one day and is therefore a valuable tool for high-throughput screening of potential T cell epitopes derived from multiple pathogen-, tumour-, and autoimmune disease related antigens. Innovative flowcytometry technique Next to UV-induced peptide exchange, combinatorial coding can be performed to quickly monitor peptide-specific T cell recognition of the MHC-peptide complexes. This innovative flowcytometry technique allows the simultaneous detection of 28 antigen specific T cells within a single blood sample. With this method a unique dual-colour code is assigned to each MHC-peptide complex of interest.
The researchers of Sanquin and the NCI were able to develop a high-tech flowcytometry protocol in which they can combine 8 fluorescent markers, together identifying 28 different MHC-peptide specific T cell populations. It is also possible to add phenotypic markers allowing simultaneously characterisation of the antigen-specific T cell populations. This is in particular relevant for obtaining proof of mechanism in a clinical trial when sample availability is limited.
Both techniques helped to reveal high affinity binding peptides for leukaemia cells, melanoma-tumour cells and influenza H5N. Similarly, this principle can be applied for other tumours, various pathogens and autoimmune disorders.
Knowledge obtained with the UV-induced peptide exchange and combinatorial coding is not only important for the development of new therapies, but valuable information is also provided for immunomonitoring of patients and application in diagnostic tools.