Maximizing dendritic cell migration after vaccination therapy

M. SRINIVAS; F. BONETTO; E. AARNTZEN; C. PUNKT; O. BOERMAN; P. VERDIJK; A. HEERSCHAP; C. G. FIGDOR; I. J. M. DE VRIES

Aguas de Lindoia, Sao Paulo, Brasil

Encuentro; XXXV Brazilian Meeting on Condensed Matter Physics; 2012

Introduction In Immunotherapy, autologous antigen-presenting cells, principally dendritic cells (DCs), from a cancer patient are used to stimulate their immune system against the disease. Although about 20 clinical trials involving intradermally delivered DCs have been carried out, no more than 4% of the cells have reproducibility reached the target lymph nodes. Optimization of this migration has proved di±cult, mainly because there was no suitable in vitro assay suited to the large cell numbers typically used in such trials (millions of cells). We have recently developed such an assay, based on scale migration of DCs in a collagen sca®old using 19F imaging to measure cell migration. Here we validate the assay results with clinical DC migration data. In particular, we ¯nd that bolus injections of over 1 million cells result in extensive cell death and therefore reduced migration. Methods Human DCs were generated from peripheral blood mononuclear cells, and labeled with 111In for scintigraphy in melanoma patients where indicated. For 19F-labeling, non-emulsion based per°uorocarbon nanoparticles were added. For migration assays, a known number of cells was embedded in the sca®old with a superimposed chemokine gradient. Alternatively, cells were injected directly in tissue samples. Samples were placed verti- cally and only upward migration was considered, thus excluding nonspeci¯c movement. All experiments were performed on a 7T horizontal bore, temperature-regulated MR-system with a 1H/19F volume coil. Results and Discussion Migration occurred only with lower cell numbers, and always only in the migration layer. The in vitro migration data show a strong correlation between the total cell number and their migration rate. We found that decreasing the number of cells in the cell layer resulted in a higher percentage of migration. Moreover, we found no di®erence in migration rates whether we used tissue samples or the gel sca®old. When 111In-labeled DCs were injected intradermally in melanoma patients and subsequently imaged using scintigraphy, we found that between 1-4total cells reached the draining lymph nodes. Furthermore, the number of migratory cells increased as the total number of cells dropped from 5 to 0.1 million. This is in line with our assay results. However, the discrepancy at the lowest cell number is due to the low sensitivity of clinical scintigraphy. This low sensitivity of clinical imaging techniques is one key reason why an in vitro assay is necessary to optimize cell migration. Our assay allows us to use the large cell numbers used in the clinic, together with opaque samples, including tissue. The technique is also inherently quantitative and the assay can readily be modi¯ed to study the e®ect of di®erent chemokines or other factors.