MABC592 Sigma-AldrichAnti-TRP1/TYRP1 Antibody, clone TA99, Azide Free

Passive immunization with monoclonal antibody TA99 targeting melanoma differentiation antigen tyrosinase-related protein-1 (Tyrp1; gp75) and active immunization with plasmid DNA encoding altered Tyrp1 both mediate tumor immunity in the B16 murine melanoma model. We report here that TA99 enhances Tyrp1 DNA vaccination in the treatment of B16 lung metastases, an effect mediated by immunologic mechanisms as Tyrp1 has no known role in regulating tumor growth. TA99 is shown to increase induction of anti-Tyrp1 CD8+T-cell responses to DNA vaccination against Tyrp1 as assessed by IFN-gamma ELISPOT assays. Immunohistochemistry studies reveal that TA99 localizes rapidly and specifically to B16 lung nodules. Augmentation of T-cell responses is dependent on the presence of tumor as well as on activating Fc receptors. Furthermore, TA99 enhances DNA vaccination against a distinct melanoma antigen, gp100(pmel17/silver locus), improving antitumor efficacy, augmenting systemic CD8+ T-cell responses to gp100, and increasing CD8+ T-cell infiltration at the tumor site. Epitope spreading was observed, with CD8+ T-cell responses generated to Tyrp1 peptide in mice receiving gp100 DNA vaccination in the presence of TA99. Finally, we show that TA99 improves therapeutic efficacy of DNA vaccination combined with adoptive T-cell transfer in treatment of established subcutaneous B16 melanoma. In conclusion, TA99 enhances DNA vaccination against both the target antigen Tyrp1 and a distinct melanoma antigen gp100 in an Fc receptor-dependent mechanism, consistent with enhanced cross-presentation of tumor-derived antigen. Monoclonal antibodies should be tested as vaccine adjuvants in the treatment of cancer.

Targeted immunotherapy against tumors or angiogenesis has shown promise as an alternative approach for the treatment of malignant disease. Whether or not combining these two treatment modalities would enhance the antitumor effect was tested in mouse models of malignant melanoma. C57BL/6 mice bearing established subcutaneous B16 tumors were treated with anti-vascular endothelial growth factor receptor (anti-VEGFR) fetal liver kinase-1 (Flk-1) monoclonal antibody (mAb) DC101 and/or anti-TYRP-1/gp75 (tyrosinase-related protein-1) mAb TA99. The growth of subcutaneous B16 tumors was significantly suppressed by the mAb DC101 (63%, p<0.001) and by mAb TA99 (75%, p<0.001) treatment alone. The combined antibody (TA99+DC101) treatment resulted in a significant enhancement (93%, p<0.001) of tumor growth suppression. In a B16 pulmonary metastasis model, combined therapy with mAb DC101 and mAb TA99 resulted in a significant reduction of lung metastases compared to the control (p<0.001) and the single agent treatment groups (p<0.05). A combined modality approach that provides passive immunity to melanoma differentiation antigens as well as inhibiting tumor neovascularization may be valuable for the treatment of malignant melanoma.

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.