HTLV-1 bZIP Factor Impairs Anti-viral Immunity by Inducing Co-inhibitory Molecule, T Cell Immunoglobulin and ITIM Domain (TIGIT)

RESEARCH ARTICLE HTLV-1 bZIP Factor Impairs Anti-viral Immunity by Inducing Co-inhibitory Molecule, T Cell Immunoglobulin and ITIM Domain (TIGIT) Keiko Yasuma1, Jun-ichirou Yasunaga1*, Keiko Takemoto2, Kenji Sugata1, Yuichi Mitobe1, Norihiro Takenouchi3, Masanori Nakagawa4, Yutaka Suzuki5, Masao Matsuoka1* 1 Laboratory of Virus Control, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto, Japan, 2 Laboratory of Biological Protection, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto, Japan, 3 Department of Microbiology, Kansai Medical University, Hirakata, Osaka, Japan, 4 North Medical Center, Kyoto Prefectural University of Medicine, Yosano-cho, Kyoto, Japan, 5 Department of Computational Biology and Medical Science, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan OPEN ACCESS Citation: Yasuma K, Yasunaga J-i, Takemoto K, Sugata K, Mitobe Y, Takenouchi N, et al. (2016) HTLV-1 bZIP Factor Impairs Anti-viral Immunity by Inducing Co-inhibitory Molecule, T Cell Immunoglobulin and ITIM Domain (TIGIT). PLoS Pathog 12(1): e1005372. doi:10.1371/journal. ppat.1005372 Editor: Susan R Ross, University of Pennsylvania School of Medicine, UNITED STATES Received: August 7, 2015 Accepted: December 8, 2015 Published: January 6, 2016 Copyright: © 2016 Yasuma et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All raw sequence data were deposited in the DNA Data Bank of Japan (DDBJ) under the accession number DRA003229 and DRA003744. Funding: This study was supported by grants from the Ministry of Education, Science, Sports, and Culture of Japan to MM (22114003) and JiY (26460554), and by JSPS KAKENHI to KY (14J03189), and MEXT KAKENHI (221S0002) for high-throughput sequencing. This study was performed as a research program of the Project for * (JY); (MM) Abstract Human T-cell leukemia virus type 1 (HTLV-1) infects CD4+ T cells and induces proliferation of infected cells in vivo, which leads to the onset of adult T-cell leukemia (ATL) in some infected individuals. The HTLV-1 bZIP factor (HBZ) gene, which is encoded in the minus strand of HTLV-1, plays critical roles in pathogenesis. In this study, RNA-seq and ChIP-seq analyses using HBZ transduced T cells revealed that HBZ upregulates the expression and promoter acetylation levels of a co-inhibitory molecule, T cell immunoglobulin and ITIM domain (TIGIT), in addition to those of regulatory T cells related genes, Foxp3 and Ccr4. TIGIT was expressed on CD4+ T cells from HBZ-transgenic (HBZ-Tg) mice, and on ATL cells and HTLV-1 infected CD4+ T cells of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in vivo. Expression of Blimp1 and IL-10 was upregulated in TIGIT+CD4+ cells of HBZ-Tg mice compared with TIGIT-CD4+ T cells, suggesting the correlation between TIGIT expression and IL-10 production. When CD4+ T cells from HBZ-Tg mice were stimulated with TIGIT’s ligand, CD155, their production of the inhibitory cytokine IL-10 was enhanced. Furthermore, dendritic cells from HBZ-Tg mice produced high levels of IL-10 after stimulation. These data suggest that HBZ alters immune system to suppressive state via TIGIT and IL-10. Importantly, TIGIT suppressed T-cell responses to another HTLV-1 virus protein, Tax, in vitro. Blocking of TIGIT and PD-1 slightly increased anti-Tax T-cell activity in some HAM/TSP patients. These results suggest that HBZ-induced TIGIT on HTLV-1 infected cells impairs T-cell responses to viral antigens. This study shows that HBZ-induced TIGIT plays a pivotal role in attenuating host immune responses and shaping a microenvironment favorable to HTLV-1. PLOS Pathogens | DOI:10.1371/journal.ppat.1005372 January 6, 2016 1 / 22 HTLV-1 bZIP Factor Induces TIGIT Expression Development of Innovative Research on Cancer Therapeutics (P-DIRECT), Ministry of Education, Culture, Sports, Science and Technology of Japan (to JiY). This study was also supported in part by the JSPS Core-to-Core Program A, Advanced Research Networks. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Author Summary HTLV-1 is a T-cell-tropic, latently infectious virus that causes a T-cell malignancy, ATL, and inflammatory diseases. The mechanisms by which HTLV-1 evades the immune response and establishes chronic infection are not yet understood. Recent studies have demonstrated that TIGIT, a co-inhibitory molecule, is expressed on tumor infiltrating T cells and T cells during viral infection, which suppresses the anti-tumor and anti-viral immune responses. Furthermore, blockade of co-inhibitory molecules of TIGIT and programmed cell death-1 (PD-1) disrupts immune checkpoints and enhances anti-tumor activity. We found that TIGIT is upregulated by HBZ, and TIGIT impairs anti-virus immune responses through an immunosuppressive cytokine, IL-10. These findings show that HTLV-1 utilizes a co-inhibitory molecule on infected cells to evade the host immune responses. We also found that blocking of TIGIT and PD-1 on peripheral blood mononuclear cells in HTLV-1 infected patients enhances immune responses to virus. These findings suggest a mechanism by which HTLV-1 shapes a microenvironment favorable to its persistence using induced TIGIT. TIGIT is a potential therapeutic target for ATL and HTLV-1 infected patients. Introduction Oncogenic viruses, including Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpesvirus (KSHV), human papilloma virus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Merkel cell polyomavirus and human T-cell leukemia virus type 1 (HTLV-1), cause approximately 12% of human cancers. In these virus-induced cancers, a limited number of viral proteins play critical roles in oncogenesis—proteins that include HBx for HBV, E6 and E7 for HPV, and Tax and HTLV-1 bZIP factor (HBZ) for HTLV-1 [1]. These viral proteins influence a cell’s epigenetic status and/or modulate a cell’s transcriptional machinery, leading to the transformation of infected cells. HTLV-1 causes adult T-cell leukemia (ATL) in a fraction of infected individuals after a long latent period [2]. HTLV-1 induces clonal proliferation of infected cells in vivo [3]. The HBZ gene, which is encoded in the minus strand, is expressed in all ATL cases and is reported to cause inflammation and T-cell lymphoma, and associate with latency [4–6]. However, the precise mechanism by which this occurs is not fully understood. HTLV-1 causes the proliferation of infected cells in vivo, but the host immune response influences the population dynamics of infected cells. One of the main issues for HTLV-1 pathogenesis is how HTLV-1 infecte (...truncated)