Tumour associated antigen ctls induced by direct intra-tumour injection of disc-hsv specifically traffic to parental tumour microcirculation in murine model

SA Ali

Department of Life Sciences, Nottingham Trent University Clifton Lane, Nottingham NG11 8NS, UK

Direct intra-tumour injection of a Disabled Infectious Single Cycle HSV-2 Virus encoding the mGM-CSF gene (DISC-mGM-CSF) into murine colon carcinoma CT26 tumours induced significant tumour growth delay and complete tumour regression in up to 70% of animals. Subsequent intra-tumour injection with syngeneic dendritic cells further decreased tumour growth and increased the incidence of complete tumour regression. Direct intra-tumour injection of DISC-mGM-CSF also inhibited distant CT26 tumours implanted on the contra-lateral flank and significantly reduced experimental lung metastasis. Potent tumour specific CTLs (CD8+ T cells dependent as determined by depletion studies) were generated from splenocytes of all mice with regressing, but not progressing tumours following in vitro peptide stimulation (tumour associated antigen "GP-70" derived H2Ld restricted AH-1, SPSYVYHQF peptide); this response was correlated with cytokine profile and spleen weight. CTLs adoptively transferred the immunity against the parental tumours. Specific trafficking of fluorescently labeled CTLs into the micro-environment of CT26 tumours was examined using our established in vivo tumour microcirculation model. The in vivo microscopy technique permits the dynamic visualization of fluorescently labeled effector cells (CTLs) migrating across the endothelium and basement membrane and localization within the CT26 tumours implanted in the cremaster muscle of syngeneic mice. CTL generated against GP-70 antigen (p<0.001) but not against the bacterial galactosidase gene were specifically recruited and arrested into the tumour microcirculation following the systematic injection into tumour-bearer mice. Tumour regression induced by DISC-mGM-CSF virus and DCs immunotherapy provides a unique model for evaluating the immune mechanism(s) involved in tumour rejection, and potential use in human cancer immunotherapy.

KEY WORDS: peptides.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Immunotherapy.