Immunotherapy with antibody-targeted HLA class I complexes: results of in vivo tumour cell killing and therapeutic vaccination.
Savage P., Dyson J., Milrain M., Mathews D., King B., Chan HTC., Barber L., Epenetos A., Ogg G., McMichael A., Glennie MJ., French RR.
BACKGROUND: The delivery of antibody-targeted major histocompatibility complex (MHC) class I complexes containing immunogenic peptides to the surface of tumour cells allows cytotoxic T lymphocytes (CTLs) of non-tumour specificity to recognise and kill the tumour cell. Previous studies have demonstrated the activity of this system in vitro and in a simple pre-clinical model. This system has also been shown to be an effective method of expanding antigen-specific CTLs in vitro when used to target MHC class I complexes to the surface of B cells. METHODS: Mice were immunised with ovalbumin and the survival of EL4Hu20 lymphoma cells targeted with H2-D(b)/Ova complexes and control MHC complexes was compared by FACS analysis. A tumour protection assay was performed where immunised mice were injected B16Hu20 melanoma cells targeted with H2-K(b)/Ova or control complexes. T cell expansion in vivo was examined by administering B cells targeted with MHC class I/peptide complexes and assessing T cell expansion by tetramer analysis. RESULTS: In vivo killing of H2-D(b)/Ova-targeted lymphoma cells in the immunised mice was demonstrated with these cells present at only 12% of the level of the control cells. In contrast, in non-immunised mice the survival of H2-D(b)/Ova-targeted and control cells was comparable. In the tumour protection assay, injection of melanoma cells targeted with H2-K(b)/Ova complexes resulted in the development of only a solitary metastasis in each mouse. This compared to an average of 130 metastases in the control mice injected with B16Hu20 cells targeted with a control MHC peptide complex. In vivo CTL expansion was demonstrated after a single intravenous administration of Daudi B cells coated with H2-D(b)/Uty complexes produced an increase in the proportion of Uty-reactive CTLs from 3.3 to 21.5%. CONCLUSION: This study supports the development of antibody-delivered MHC complexes as a method of producing CTL-mediated lysis of cancer cells in vivo. As a therapeutic vaccine, the system may provide an effective approach for expanding oligoclonal T cell responses in vivo in the treatment of malignancy and infectious diseases.