IN VIVO FORMATION OF ANTIGEN-SPECIFIC IMMUNOLOGICAL SYNAPSES BETWEEN ANTI-TUMOR T CELLS AND TARGET GLIOMA CELLS: A DETAILED QUANTITATIVE AND QUALITATIVE CHARACTERIZATION OF THE KINETICS, DISTRIBUTION, AND MICROANATOMY OF THE ANTI-TUMOR IMMUNE RESPONSE

YANG; SANDERSON; PUNTEL; BARRET; KROEGER; CASTRO; LOWENSTEIN

Las Vegas, Nevada, USA

Congreso; Society for Neuro-Oncology; 2008

In vivo formation of antigen-specific immunological synapses between anti-tumor T cells and target glioma cells: a detailed quantitative and qualitative characterization of the kinetics, distribution, and microanatomy of the anti-tumor immune response.Jieping Yang, Nicholas Sanderson, Mariana Puntel, Robert Barrett, Kurt M. Kroeger, Maria G. Castro and Pedro R. Lowenstein.Board of Governors’ Gene Therapeutics Research Institute, Cedars-Sinai Medical Center and Department of Medicine and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90048. Correspondence: lowensteinp@cshs.orgWe have shown that Ad-Flt3L and Ad-TK treatment of brain gliomas induces an antigen specific T cell-dependent anti-tumor immune response in several syngeneic rodent glioma models. Although we also demonstrated that antiviral CD8+ T cells establish “classical” immunological synapses in vivo with Ad-infected brain astrocytes, the existence of immunogical synapses between T cells and brain glioma cells remains unknown.To study anti-tumor antigen-specific immune responses we established a syngeneic mouse glioma model using GL26 glioma cells expressing ovalbumin (OVA) as a surrogate tumor antigen. Anti-tumor specific immune responses were characterized by flow cytometry, ELISPOT assays, immunohistochemistry, and the use of specific SIINFEKL H2-Kb tetramers to determine both the distribution and morphology of antigen-specific immunological synapses. To characterize immunological synapses we quantified the immunocytochemical distribution of CD3-epsilon and LFA-1, or SIINFEKL H2-Kb tetramers and LFA-1 and OVA-positive cells. Antigen-specific immunological synapses were also characterized in Rag1-/- mice implanted with GL26-cOVA tumors treated with Flt3L/TK, and adoptively transferred with splenocytes from OT-I mice.Using flow cytometry we determined that the vast majority of tumor antigen-specific T cells were localized to the brain tumors. Restimulation with tumor antigen indicated that 18% of brain-infiltrating T cells expressed IFN-gamma. Intriguingly, we were unable to detect quanti- or qualitative differences between immunological synapses from brains of saline or Flt3L/TK treated mice. Importantly, tetramer-positive immunological synapses differed in structure from typical “classical” immunological synapses, and were mainly found in immunized animals.Our data suggest that “classical” immunological synapses may not represent the immunologically active synapses mediating brain tumor regression. Nevertheless, it is likely that the immunologically active synapses are those identified by tetramer immunolabeling. Continued evaluation of complex cellular and molecular basis of T cell-tumor cell interactions is needed to further improve the design and clinical efficacy of novel glioma immunotherapy approaches.