Targeting B-cell malignancies through human B-cell receptor specific CD4+ T cells

The B-cell receptor (BCR) expressed by a clonal B cell tumor is a tumor specific antigen (idiotype). However, the T-cell epitopes within human BCRs which stimulate protective immunity still lack detailed characterization. In this study, we identified 17 BCR peptide-specific CD4⁺ T-cell epitopes derived from BCR heavy and light chain variable region sequences. Detailed analysis revealed these CD4⁺ T-cell epitopes stimulated normal donors' and patients' Th1 CD4⁺ T cells to directly recognize the autologous tumors by secretion of IFNγ, indicating the epitopes are processed and presented by tumor cells. One BCR peptide-specific CD4⁺ T cell line was also cytotoxic and lysed autologous tumor cells through the perforin pathway. Sequence analysis of the epitopes revealed that 10 were shared by multiple primary patients' tumors, and 16 had the capacity to bind to more than one HLA DRB1 allele. T cells stimulated by shared epitopes recognized primary tumors expressing the same sequences on multiple HLA DRB1 alleles. In conclusion, we identified 17 BCR-derived CD4⁺ T-cell epitopes with promiscuous HLA DRB1 binding affinity that are shared by up to 36% of patients, suggesting a strategy to overcome the requirement for individual preparation of therapeutic agents targeting idiotype.

Targeting tumor-associated myeloid cells for cancer immunotherapy

Tumor-associated myeloid cells undermine the therapeutic efficacy of cancer immunotherapy by their inhibitory properties on immune effector cells. Development of therapeutic agents to deplete suppressive myeloid cells in tumor microenvironment requires identification of cell-specific targets. A competitive phage display technique on live cells paves the way to discovery of such a target.

Abstract 2891: Bench-to-bedside development of a novel idiotype vaccine against lymphoma

Available therapies for lymphoplasmacytic lymphoma (LPL) provide no survival advantage if started before symptoms of end organ damage develop. Current recommendations are to follow a program of observation while patients are in the asymptomatic phase of disease. In this clinical study we will use idiotypic determinants of B-cell lymphoma surface immunoglobulins as tumor-specific antigens (idiotype) to develop a patient-specific vaccine against LPL. By activating the host immune system through vaccination to eradicate tumor cells, we postulate that disease control of asymptomatic phase lymphoplasmacytic lymphoma can be maintained. This novel 2nd generation idiotype vaccine was initially developed by genetic fusion of idiotype antigen in single-chain format with a pro-inflammatory chemokine. The central hypothesis is that antitumor immunity can be triggered by targeting antigen delivery to antigen-presenting cells in vivo by chemokine receptor-mediated binding, uptake and processing of idiotype antigens for more efficient presentation to T cells. A large body of preclinical data demonstrated that the immunogenecity of the idiotype antigen was considerably enhanced by such a genetic modification by a mechanism of facilitating antigen presentation. As a consequence, vaccine-induced prophylactic and therapeutic antitumor effects were significantly potentiated. To translate our vaccine therapy from bench to bedside, we established a CLP laboratory for vaccine preparation. Furthermore, we developed reliable technology to differentiate lymphoma idiotype antigens from idiotypic cell-surface immunoglobulins on normal B cells. Using this technology, we successfully cloned the cDNA encoding variable regions of heavy and light chains of LPL idiotype, and generated patient-specific plasmid constructs containing LPL idiotype single chain in fusion with macrophage inflammatory protein 3 alpha (MIP3a). All three engineering rounds of down-stream GMP amplification of clinical-grade plasmid DNA have been accomplished, which eventually paves the way for us to take a lab-grown agent to a first-in-human clinical trial.

Citation Format: Hong Qin, Soungchul Cha, Sheetal S. Rao, Kunhwa Kim, Dongho Gwak, Sung-doo Kim, Sapna R. Parshottam, Sheeba K. Thomas, Larry W. Kwak. Bench-to-bedside development of a novel idiotype vaccine against lymphoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2891. doi:10.1158/1538-7445.AM2014-2891

The effect of combined IL10 siRNA and CpG ODN as pathogen-mimicking microparticles on Th1/Th2 cytokine balance in dendritic cells and protective immunity against B cell lymphoma

Success of an immunotherapy for cancer often depends on the critical balance of T helper 1 (Th1) and T helper 2 (Th2) responses driven by antigen presenting cells, specifically dendritic cells (DCs). Th1-driven cytotoxic T cell (CTL) responses are key to eliminating tumor cells. It is well established that CpG oligonucleotides (ODN), a widely studied Toll-like receptor 9 (TLR9) agonist, used to enhance Th1 response, also induces high levels of the anti-inflammatory, Th2-promoting cytokine IL10, which could dampen the resulting Th1 response. Biomaterials-based immunomodulatory strategies that can reduce IL10 production while maintaining IL12 levels during CpG delivery could further enhance the Th1/Th2 cytokine balance and improve anti-tumor immune response. Here we report that dual-delivery of IL10-silencing siRNA along with CpG ODN to the same DCs using pathogen-mimicking microparticles (PMPs), significantly enhances their Th1/Th2 cytokine ratio through concurrent inhibition of CpG-induced IL10 production. Co-delivery of poly(I:C), a TLR3 agonist had only minor effects on IL10 levels. Further, simultaneous immunotherapy with CpG ODN and IL10 siRNA enhanced immune protection of an idiotype DNA vaccine in a prophylactic murine model of B cell lymphoma whereas co-delivery of poly(I:C) and CpG did not enhance protection. These results suggest that PMPs can be used to precisely modulate TLR ligand-mediated immune-stimulation in DCs, through co-delivery of cytokine-silencing siRNAs and thereby boost antitumor immunity.