A Class II / CD80 Retinoblastoma Tumor Cell Vaccine

Abstract

Purpose: : Our long-term goal is to induce protective immunity in retinoblastoma (Rb) patients that selectively eliminates tumor cells without damaging the surrounding normal retina. We hypothesize that a CD80 / Class II positive Rb tumor cell vaccine will activate tumor-specific CD4+ T cells that sustain potent anti-tumor immunity. Tumor-specific CD4+ T cells are activated when they recognize tumor antigens presented by Class II with the CD80 costimulatory signal. However, Class II only presents endogenous tumor antigens when the invariant chain is absent. Since Class II and invariant chain genes are normally expressed coordinately, we identified Rb cells that were unable to express either gene and then transfected the cells with Class II and CD80.

Methods: : Rb gene mutations were identified by sequencing in the cell lines studied (Rb107, 116, 125, 143). Class II and invariant chain were detected in unstimulated and IFN-g stimulated Rb cells via Western blot and flow cytometry. Rb cells were transfected (AMAXA) with vectors containing the cDNA for: Class II (DRA*0101and DRB1*0101) and CD80.

Results: : Two of the four Rb cell lines tested (Rb143 and Rb107) were candidates for a CD80 / Class II tumor cell vaccine and did not express either: (i) Class II (DR, DP, or DQ), or (ii) invariant chain. Moreover, stimulation of either Rb143, or Rb107 with IFN-g (up to 1,000 units) failed to trigger expression of either Class II or invariant chain. By contrast, Class II (DR, DP, and DQ) was constitutively expressed on Rb116 and IFN-gamma treated Rb125. Rb143 and Rb107 were transfected successfully with vectors containing the cDNA for: (i) Class II DR1 and/or (ii) CD80.

Conclusions: : We genetically modified Rb cells to express CD80 and Class II in the absence of invariant chain. These results imply that Rb tumor cells can be genetically engineered to express endogenous tumor antigens that activate CD4+ T cells.

Keywords: retinoblastoma • gene transfer/gene therapy • immunomodulation/immunoregulation