Induction of autoantibodies against tyrosinase-related proteins following DNA vaccination: unexpected reactivity to a protein paralogue.

DNA vaccination against tissue-restricted antigens is a strategy for cancer therapy. Immune tolerance and ignorance of self antigens has been a hurdle for this approach. We have shown that immunization with xenogeneic DNA orthologues elicits tumor immunity. One model that we have developed entails immunization of mice against tyrosinase-related protein-2 (Tyrp2) using cDNA encoding homologous human Tyrp2. A subset of mice immunized with human Tyrp2 developed antibody responses to Tyrp1. Unexpectedly, this was not simply due to cross-reactivity, as mice with anti-Tyrp1 antibodies were not usually the same animals with anti-Tyrp2 antibodies. Although autoimmune vitiligo was frequently observed in mice that had been immunized with Tyrp2, its occurrence was not correlated with the development of antibodies to Tyrp1. This implies that the appearance of anti-Tyrp1 antibodies was not simply a consequence of the destruction of melanocytes by T-cells recognizing Tyrp2. This represents an example of intermolecular determinant recognition, but is not simply due to epitope spreading since antibodies against the antigen targeted by DNA vaccination are not typically detected.