T-cell responses in osteosarcoma patients vaccinated with an anti-idiotypic antibody, 105AD7, mimicking CD55.

We assessed T-cell responses in young osteosarcoma patients vaccinated with 105AD7, 1-6 months after having received chemotherapy. 105AD7 is a human anti-idiotypic antibody mimicking CD55, a glycoprotein that protects from attack by complement and which is overexpressed on osteosarcoma cells. Seven out of 21 investigated patients made a IFN-gamma T-cell response against the vaccine, 105AD7 as assessed by ELISPOT. Cytokine secretion was analysed using Luminex assays and revealed TNF-alpha and GM-CSF responses not only to the vaccine but also towards the native antigen, CD55, in 5 / 14 (36%) of investigated patients. Importantly, the Luminex assay was found to be more sensitive than the more established T-cell assays (ELISPOT and proliferation assay), since responses towards the native antigen were recorded in this assay. Clinical responses and induction of immune responses to both the anti-idiotype and the native CD55 antigen support the use of CD55 as a target in cancer treatment.