Regulation of CTL responses to MHC‐restricted class I peptide of the gp70 tumour antigen by splenic parenchymal CD4⁺ T cells in mice failing immunotherapy with DISC–mGM‐CSF

Abstract

Direct intratumour injection of the disabled infectious singlecycle-herpes simplex virus-encoding murine granulocyte/macrophage colony-stimulating factor (DISC-HSV-mGM-CSF) into established colon carcinoma CT26 tumours induced complete tumour rejection in up to 70% of treated animals (regressors), while the remaining mice developed progressive tumours (progressors). This murine Balb/c model was used to dissect the cellular mechanisms involved in tumour regression or progression following immunotherapy. CTLs were generated by coculturing lymphocytes and parenchymal cells from the same spleens of individual regressor or progressor animals in the presence of the relevant AH-1 peptide derived from the gp70 tumour-associated antigens expressed by CT26 tumours. Tumour regression was correlated with potent CTL responses, spleen weight and cytokine (IFN-g) production. Conversely, progressor splenocytes exhibited weak to no CTL activity and poor IFN-g production, concomitant with the presence of a suppressor cell population in the progressor splenic parenchymal cell fraction. Further fractionation of this parenchymal subpopulation demonstrated that cells inhibitory to the activation of AH-1-specific CTLs, restimulated in vitro with peptide, were present in the nonadherent parenchymal fraction. In vitro depletion of progressor parenchymal CD3 + /CD4 + T cells restored the CTL response of the cocultured splenocytes (regressor lymphocytes and progressor parenchymal cells) and decreased the production of IL-10, suggesting that CD3 + CD4+ T lymphocytes present in the parenchymal fraction regulated the CTL response to AH-1. We examined the cellular responses associated with tumour rejection and progression, identifying regulatory pathways associated with failure to respond to immunotherapy. ' 2005 Wiley-Liss, Inc.

Melanoma cells interfere with the interaction of dendritic cells with NK/LAK cells

“…31 In selected experiment, CD31 lymphocytes were depleted by magnetic bead sorting, as described. 32 NK/LAK cells were routinely characterized by flow cytometry after staining with mAbs specific for NKG2A, NK1.1, Ly49A, CD94, CD3, H2-K b , IA b and appropriate PerCP, FITC-and PE-conjugated second step reagents (PharMingen, BD Bioscences, CA). Functional activity against 51 Crlabelled targets (B16F1, Yac-1, RMA lymphoma cells, PHA blasts) was also routinely evaluated, as detailed further.…”

Cancer vaccines: Uses of HLA transgenic mice compared to genetically modified mice

“…At present time, no single mouse model will cover the full spectrum of the human disease and researchers whilst developing new models, need to bear in mind the limitations imposed by the developing tumor and its microenvironment and the differences existing between mouse and human, such as in the Toll-like receptor family (46). Toll-like receptors (TLRs) belong to a family of receptors called pattern recognition receptors (PRRs) which are used by the innate cells to recognize conserved pathogen-associated molecular patterns (PAMPs) expressed by microorganisms.…”

“…To date 10 TLRs have been identified in human and 12 in mice. Their expression and stimulation have however been shown to differ between human and mice (46). Indeed TLR-2 for example which recognizes bacterial lipopeptides is present in mouse T-cells but not in human, and TLR-3 which recognizes double-stranded RNA is expressed by mouse macrophages but not human macrophages (47,48).…”

Serum biomarkers which correlate with failure to respond to immunotherapy and tumor progression in a murine colorectal cancer model

“…Direct injection of DISC‐HSV into an established CT26 colon tumor results in complete regression of the tumor (tumor regressors) in up to 70% of the treated mice with the remaining animals failing to respond (tumor progressor). This model was previously used to study the immunological mechanisms involved in the regression/progression of the tumor after administration of DISC immunotherapy 7. The results identified CD3 + T lymphocyte effector cells from the spleens of the progressor animals to mediate cytotoxic T lymphocyte (CTL) activity, correlating with tumor regression.…”