Refining human T-cell immunotherapy of cytomegalovirus disease: a mouse model with 'humanized' antigen presentation as a new preclinical study tool

With the cover headline 'T cells on the attack,' the journal Science celebrated individualized cancer immunotherapy by adoptive transfer of T cells as the 'Breakthrough of the Year' 2013 (J. Couzin-Frankel in Science 342:1432-1433, 2013). It is less well recognized and appreciated that individualized T cell immunotherapy of cytomegalovirus (CMV) infection is approaching clinical application for preventing CMV organ manifestations, interstitial CMV pneumonia in particular. This coincident medical development is particularly interesting as reactivated CMV infection is a major viral complication in the state of transient immunodeficiency after the therapy of hematopoietic malignancies by hematopoietic cell transplantation (HCT). It may thus be attractive to combine T cell immunotherapy of 'minimal residual disease/leukemia (MRD)' and CMV-specific T cell immunotherapy to combat both risks in HCT recipients simultaneously, and ideally with T cells derived from the respective HLA-matched HCT donor. Although clinical trials of human CMV-specific T cell immunotherapy were promising in that the incidence of virus reactivation and disease was found to be reduced with statistical significance, animal models are still instrumental for providing 'proof of concept' by directly documenting the prevention of viral multiple-organ histopathology and organ failure under controlled conditions of the absence versus presence of the therapy, which obviously is not feasible in an individual human patient. Further, animal models can make predictions regarding parameters that determine the efficacy of T cell immunotherapy for improved study design in clinical investigations, and they allow for manipulating host and virus genetics. The latter is of particular value as it opens the possibility for epitope specificity controls that are inherently missing in clinical trials. Here, we review a recently developed new mouse model that is more approximated to human CMV-specific T cell immunotherapy by 'humanizing' antigen presentation using antigenically chimeric CMV and HLA-transgenic mice to allow for an in vivo testing of the antiviral function of human CMV-specific T cells. As an important new message, this model predicts that T cell immunotherapy is most efficient if CD4 T cells are equipped with a transduced TCR directed against an epitope presented by MHC/HLA class-I for local delivery of 'cognate' help to CD8 effector T cells at infected MHC/HLA class-II-negative host tissue cells.

Modulation of Immune response by Ultra-violet light in HLA class-II transgenic mice

Multiple Sclerosis (MS) is a chronic and debilitating disease of the central nervous system linked to both genetic and environmental factors. Among the genetic factors, MHC, especially HLA class-II, is strongly associated with predisposition to MS. Although in vitro studies have helped us understand some aspects of HLA class-II association with the disease, performing in vivo analysis is necessary in order to further understand this correlation. Studying the role of class-II genes in vivo is a difficult task due to the heterogeneity of human population, the complexity of MHC, and the strong linkage disequilibrium among different class-II genes. To overcome this challenge, we generated HLA class-II transgenic mice to study the role of these molecules in MS. Among the environmental factors linked with MS, ultra violet radiation (UVR)/vitamin-D is suggested to have protective effect against the development of the disease. Indeed, genetic studies have shown that presence of susceptible HLA-Class II and decrease in UVR exposure or vitamin D levels together increase risk of MS. Therefore, this study was designed to investigate the direct effect of UVR on immune response using novel humanized HLA-class II transgenic mice. HLA-class II transgenic mice expressing MS susceptible HLA-DR2 allele were treated with different doses of UVR (0.50-3.75 kJ/day) for seven consecutive days. T-cell proliferation, immune cell sub-populations and cytokines levels were analyzed. Our results show that treatment with UVR increased levels of regulatory CD4+FoxP3+ T cells and Gr1+ CD11b+ suppressive macrophages. Thus our study indicates that UVR modulates the immune response towards a tolerogenic phenotype in HLA-transgenic mice immunized with MOG_35-55. Therefore, HLA class-II transgenic mice offer a novel tool to decipher the mechanism by which interaction between environmental and genetic factors play a role in predisposition and/or protection against development of MS.

Identification of NY-BR-1-specific CD4(+) T cell epitopes using HLA-transgenic mice

Breast cancer represents the second most common cancer type worldwide and has remained the leading cause of cancer-related deaths among women. The differentiation antigen NY-BR-1 appears overexpressed in invasive mammary carcinomas compared to healthy breast tissue, thus representing a promising target antigen for T cell based tumor immunotherapy approaches. Since efficient immune attack of tumors depends on the activity of tumor antigen-specific CD4(+) effector T cells, NY-BR-1 was screened for the presence of HLA-restricted CD4(+) T cell epitopes that could be included in immunological treatment approaches. Upon NY-BR-1-specific DNA immunization of HLA-transgenic mice and functional ex vivo analysis, a panel of NY-BR-1-derived library peptides was determined that specifically stimulated IFNγ secretion among splenocytes of immunized mice. Following in silico analyses, four candidate epitopes were determined which were successfully used for peptide immunization to establish NY-BR-1-specific, HLA-DRB1*0301- or HLA-DRB1*0401-restricted CD4(+) T cell lines from splenocytes of peptide immunized HLA-transgenic mice. Notably, all four CD4(+) T cell lines recognized human HLA-DR-matched dendritic cells (DC) pulsed with lysates of NY-BR-1 expressing human tumor cells, demonstrating natural processing of these epitopes also within the human system. Finally, CD4(+) T cells specific for all four CD4(+) T cell epitopes were detectable among PBMC of breast cancer patients, showing that CD4(+) T cell responses against the new epitopes are not deleted nor inactivated by self-tolerance mechanisms. Our results present the first NY-BR-1-specific HLA-DRB1*0301- and HLA-DRB1*0401-restricted T cell epitopes that could be exploited for therapeutic intervention against breast cancer.