Therapy-induced antitumor vaccination in neuroblastomas by the combined targeting of IL-2 and TNF alpha

L19-IL2 and L19TNF are fusion proteins composed of L19(scFv), specific for the angiogenesis-associated ED-B containing fibronectin isoform and IL-2 or TNF. Because of the tumor targeting properties of L19, IL-2 and TNF concentrate at therapeutic doses at the tumor vascular level. To evaluate the therapeutic effects of L19-IL2 and L19mTNF in neuroblastoma (NB)-bearing mice, A/J mice bearing Neuro2A or NIE115 NB were systemically treated with L19-IL2 and L19mTNF, alone or in combination protocols. Seventy percent of Neuro2A- and 30% of NIE115-bearing mice were cured by the combined treatment with L19-IL2 and L19mTNF, and further rejected a homologous tumor challenge, indicating specific antitumor immune memory. The immunological bases of tumor cure and rejection were studied. A highly efficient priming of CD4+ T helper cells and CD8+ CTL effectors was generated, paralleled by massive infiltration in the tumor tissue of CD4+ and CD8+ T cells at day 16 after tumor cell implantation, when, after therapy, tumor volume was drastically reduced and tumor necrosis reached about 80%. The curative treatment resulted in a long-lasting antitumor immune memory, accompanied by a mixed Th1/Th2 type of response. Concluding, L19-IL2 and L19mTNF efficiently cooperate in determining a high percentage of NB cure that, in our experimental models, is strongly associated to the generation of adaptive immunity involving CD4+ and CD8+ T cells

Optimal MHC-II-restricted tumor antigen presentation to CD4+ T helper cells: the key issue for development of anti-tumor vaccines

Present immunoprevention and immunotherapeutic approaches against cancer suffer from the limitation of being not “sterilizing” procedures, as very poor protection against the tumor is obtained. Thus newly conceived anti-tumor vaccination strategies are urgently needed. In this review we will focus on ways to provide optimal MHC class II-restricted tumor antigen presentation to CD4+ T helper cells as a crucial parameter to get optimal and protective adaptive immune response against tumor. Through the description of successful preventive or therapeutic experimental approaches to vaccinate the host against the tumor we will show that optimal activation of MHC class II-restricted tumor specific CD4+ T helper cells can be achieved in various ways. Interestingly, the success in tumor eradication and/or growth arrest generated by classical therapies such as radiotherapy and chemotherapy in some instances can be re-interpreted on the basis of an adaptive immune response induced by providing suitable access of tumor-associated antigens to MHC class II molecules. Therefore, focussing on strategies to generate better and suitable MHC class II–restricted activation of tumor specific CD4+ T helper cells may have an important impact on fighting and defeating cancer

Multiple Histone Methyl and Acetyltransferase Complex Components Bind the HLA-DRA Gene

Major histocompatibility complex class II (MHC-II) genes are fundamental components that contribute to adaptive immune responses. While characterization of the chromatin features at the core promoter region of these genes has been studied, the scope of histone modifications and the modifying factors responsible for activation of these genes are less well defined. Using the MHC-II gene HLA-DRA as a model, the extent and distribution of major histone modifications associated with active expression were defined in interferon-γ induced epithelial cells, B cells, and B-cell mutants for MHC-II expression. With active transcription, nucleosome density around the proximal regulatory region was diminished and histone acetylation and methylation modifications were distributed throughout the gene in distinct patterns that were dependent on the modification examined. Irrespective of the location, the majority of these modifications were dependent on the binding of either the X-box binding factor RFX or the class II transactivator (CIITA) to the proximal regulatory region. Importantly, once established, the modifications were stable through multiple cell divisions after the activating stimulus was removed, suggesting that activation of this system resulted in an epigenetic state. A dual crosslinking chromatin immunoprecipitation method was used to detect histone modifying protein components that interacted across the gene. Components of the MLL methyltransferase and GCN5 acetyltransferase complexes were identified. Some MLL complex components were found to be CIITA independent, including MLL1, ASH2L and RbBP5. Likewise, GCN5 containing acetyltransferase complex components belonging to the ATAC and STAGA complexes were also identified. These results suggest that multiple complexes are either used or are assembled as the gene is activated for expression. Together the results define and illustrate a complex network of histone modifying proteins and multisubunit complexes participating in MHC-II transcription

The dual function of the MHC class II against human oncogenic retroviruses

The AIR-1 gene product CIITA is the master regulator of MHC class II gene expression. This makes CIITA a crucial element for triggering antigen presentation to CD4+ T cells and thus the cascade of events leading to an efficient adaptive immune response. Recently we discovered that CIITA is also endowed with the capacity to directly inhibit both HIV-1 and HTLV retroviruses in infected cells by blocking the function of the viral transactivators Tat and Tax. Thus CIITA exerts a dual role against human retroviruses. The first, classical role is the upregulation of MHC class II expression and thus the capacity to present viral antigens to CD4+ T cells. The other, evolutionary new and fundamental role is to inhibit directly viral replication and spreading. We will discuss the molecular mechanisms by which CIITA counteracts specifically viral transactivators. These distinct properties of CIITA will shed new light on the molecular mechanisms of adaptive coevolution of hosts and pathogens and may be exploited to envisage novel therapeutic strategies aimed at counteracting retroviral infections and thus their oncogenic potential

IL-2-mediated T cell proliferation in humans is blocked by a monoclonal antibody directed against monomorphic determinants of HLA-DR antigens.

We have studied the effect on the interleukin (IL-) 2-dependent human T cell growth of two distinct monoclonal antibodies (Mab), D1-12 and 4F2, with specificity for common determinant of human Ia antigens and for a differentiation antigen expressed on all activated T cells, respectively. Strong inhibition of cell growth was found in cultures supplemented with the anti-Ia D1-12 Mab but not in cultures supplemented with 4F2 Mab. These results were obtained when either total mixed leukocyte culture (MLC) T cells or an MLC-derived T cell clone were used as indicator cell systems for IL-2 activity. The inhibition of cell growth appears to be mediated by a direct interaction of D1-12 Mab with the cells and not by a direct inactivation of the growth factor, as addition of the antibody to murine MLC T cells, which do not express the determinant defined by D1-12 Mab, resulted in no inhibition of their proliferation induced by the same source of human IL-2

Allogeneic mixed lymphocyte reactions in humans: pretreatment of either the stimulator or the responder cell population with monoclonal anti-Ia antibodies leads to an inhibition of cell proliferation.

We analyzed the effect of 2 hybridoma monoclonal antibodies (Mab), D1-12 and D4-22, with specificity for common determinants of human Ia molecules, on the mixed lymphocyte culture (MLC) response. The results show that addition of either of the 2 Mab as late as day 3 after the onset of the culture completely inhibits the proliferative response generated in MLC. Because the antigenic determinants recognized by the 2 Mab that were used in this study have been shown to belong to distinct Ia molecules, it appears the inhibitory effect observed in MLC containing such Mabs cannot be explained simply by the masking of Ia molecules on the stimulator cell population. In agreement with previous studies by other investigators, treatment of a leukocyte population with the cytolytic D1-12 Mab plus complement strongly reduced its ability to stimulate in MLC. More importantly such a treatment also decreased the ability of a leukocyte population to respond in MLC. In the latter case, the inhibitory effect appears to be directed against T cells since highly purified E-rosetting cells treated with D1-12 plus complement were unable to respond in MLC. The possible implications of these results are discussed