Search

Helper T lymphocytes (HTLs) play a central role in cancer immunity because they can not only help the induction and proliferation of cytotoxic T lymphocytes (CTLs) but also their differentiation into cytotoxic CD4+ T cells and directly kill the target cells.This study describes the identification of three novel mouse Th epitope peptides, WT135-52, WT186-102 and WT1294-312, derived from WT1 protein, which is the most potent tumor-associated antigen. Compared to immunization with WT1 CTL peptide alone, immunization with the addition of these WT1-specific Th peptides strongly induced WT1-specific CTLs, continued to maintain them, and efficiently rejected the challenge of WT1-expressing tumor cells. Importantly, the majority of WT1-specific CTLs induced by the co-immunization with WT1 CTL and the WT1-specific Th peptides were CD44+CD62L− effector memory CD8+ T cells, which played a central role in tumor rejection. Establishment of mouse models suitable for the analysis of the detailed mechanism of these functions of HTLs is very important. These results clearly showed that WT1-specific HTLs perform an essential function in WT1-specific tumor immunity. Therefore, the WT1-specific Th peptides identified here should make a major contribution to elucidation of the mutual roles of WT1-specific CTLs and HTLs in cancer immunity in in vivo mouse models. [ABSTRACT FROM AUTHOR]

Murine megakaryocytes (MKs) are defined by CD41/CD61 expression and acetylcholinesterase (AChE) activity; however, their stages of differentiation in bone marrow (BM) have not been fully elucidated. In murine lineage-negative (Lin-)/CD45+ BM cells, we found CD41+ MKs without AChE activity (AChE-) except for CD41++ MKs with AChE activity (AChE-), in which CD61 expression was similar to their CD41 level. Lin-/CD41+/CD45+/AChE- MKs could differentiate into AChE+, with an accompanying increase in CD41/CD61 during in vitro culture. Both proplatelet formation (PPF) and platelet (PLT) production for Lin-/CD41+/CD45+/AChE- MKs were observed later than for Lin-/CD41++/CD45+/AChE+ MKs, whereas MK progenitors were scarcely detected in both subpopulations. GeneChip and semiquantitative polymerase chain reaction analyses revealed that the Lin-/CD41+/CD45+/AChE- MKs are assigned at the stage between the progenitor and PPF preparation phases in respect to the many MK/PLT specific gene expressions, including β1-tubulin. In normal mice, the number of Lin-/CD41+/CD45+/AChE- MKs was 100 times higher than that of AChE+ MKs in BM. When MK destruction and consequent thrombocytopenia were caused by an antitumor agent, mitomycin-C, Lin-/CD41+/CD45+/AChE- MKs led to an increase in AChE+ MKs and subsequent PLT recovery with interleukin-11 administration. It was concluded that MKs in murine BM at least in part consist of immature Lin-/CD41+/CD45+/AChE- MKs and more differentiated Lin-/CD41+/CD45++/AChE- MKs. Immature Lin-/CD41+/CD45+/AChE- MKs are a major MK population compared with AChE+ MKs in BM and play an important role in rapid PLT recovery in vivo. [ABSTRACT FROM AUTHOR]

Reports have shown that activation of tumor-specific CD4+ helper T (Th) cells is crucial for effective anti-tumor immunity and identification of Th-cell epitopes is critical for peptide vaccine-based cancer immunotherapy. Although computer algorithms are available to predict peptides with high binding affinity to a specific HLA class II molecule, the ability of those peptides to induce Th-cell responses must be evaluated. We have established HLA-DR4 (HLA-DRA*01:01/HLA-DRB1*04:05) transgenic mice (Tgm), since this HLA-DR allele is most frequent (13.6%) in Japanese population, to evaluate HLA-DR4-restricted Th-cell responses to tumor-associated antigen (TAA)-derived peptides predicted to bind to HLA-DR4. To avoid weak binding between mouse CD4 and HLA-DR4, Tgm were designed to express chimeric HLA-DR4/I-Ed, where I-Ed α1 and β1 domains were replaced with those from HLA-DR4. Th cells isolated from Tgm immunized with adjuvant and HLA-DR4-binding cytomegalovirus-derived peptide proliferated when stimulated with peptide-pulsed HLA-DR4-transduced mouse L cells, indicating chimeric HLA-DR4/I-Ed has equivalent antigen presenting capacity to HLA-DR4. Immunization with CDCA155-78 peptide, a computer algorithm-predicted HLA-DR4-binding peptide derived from TAA CDCA1, successfully induced Th-cell responses in Tgm, while immunization of HLA-DR4-binding Wilms' tumor 1 antigen-derived peptide with identical amino acid sequence to mouse ortholog failed. This was overcome by using peptide-pulsed syngeneic bone marrow-derived dendritic cells (BM-DC) followed by immunization with peptide/CFA booster. BM-DC-based immunization of KIF20A494-517 peptide from another TAA KIF20A, with an almost identical HLA-binding core amino acid sequence to mouse ortholog, successfully induced Th-cell responses in Tgm. Notably, both CDCA155-78 and KIF20A494-517 peptides induced human Th-cell responses in PBMCs from HLA-DR4-positive donors. Finally, an HLA-DR4 binding DEPDC1191-213 peptide from a new TAA DEPDC1 overexpressed in bladder cancer induced strong Th-cell responses both in Tgm and in PBMCs from an HLA-DR4-positive donor. Thus, the HLA-DR4 Tgm combined with computer algorithm was useful for preliminary screening of candidate peptides for vaccination. [ABSTRACT FROM AUTHOR]

Background/aim: Wilms' tumor gene 1 (WT1) product is a pan-tumor-associated antigen. We previously identified WT1 protein-derived promiscuous helper peptide, WT1332. Therefore, isolation and characterization of the WT1332-specific T-cell receptors (TCRs) are useful to develop broadly applicable TCR gene-based adoptive immunotherapy., Materials and Methods: A novel HLA-DRB1*04:05-restricted WT1332-specific TCR gene was cloned and transduced into human CD4+ T-cells by using a lentiviral vector., Results: The WT1332-specific TCR-transduced CD4+ T-cells showed strong proliferation and Th1-cytokine production in an HLA-DRB1*04:05-restricted, WT1332-specific manner. Furthermore, the WT1332-specific TCR-transduced CD4+ T-cells could lyse HLA-DRB1*04:05-positive, WT1-expressing leukemia cells in vitro., Conclusion: The novel TCR gene cloned here should be a promising tool to develop adoptive immunotherapy of WT1332-specific TCR-transduced CD4+ T-cells for the treatment of WT1-expressing cancer, such as leukemia., (Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)