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HTLV-1 bZIP factor induces T-cell lymphoma and systemic inflammation in vivo.

ABSTRACT: Human T-cell leukemia virus type 1 (HTLV-1) is the causal agent of a neoplastic disease of CD4+ T cells, adult T-cell leukemia (ATL), and inflammatory diseases including HTLV-1 associated myelopathy/tropical spastic paraparesis, dermatitis, and inflammatory lung diseases. ATL cells, which constitutively express CD25, resemble CD25+CD4+ regulatory T cells (T(reg)). Approximately 60% of ATL cases indeed harbor leukemic cells that express FoxP3, a key transcription factor for T(reg) cells. HTLV-1 encodes an antisense transcript, HTLV-1 bZIP factor (HBZ), which is expressed in all ATL cases. In this study, we show that transgenic expression of HBZ in CD4+ T cells induced T-cell lymphomas and systemic inflammation in mice, resembling diseases observed in HTLV-1 infected individuals. In HBZ-transgenic mice, CD4+Foxp3+ T(reg) cells and effector/memory CD4+ T cells increased in vivo. As a mechanism of increased T(reg) cells, HBZ expression directly induced Foxp3 gene transcription in T cells. The increased CD4+Foxp3+ T(reg) cells in HBZ transgenic mice were functionally impaired while their proliferation was enhanced. HBZ could physically interact with Foxp3 and NFAT, thereby impairing the suppressive function of T(reg) cells. Thus, the expression of HBZ in CD4+ T cells is a key mechanism of HTLV-1-induced neoplastic and inflammatory diseases.

SUBMITTER: Satou Y

PROVIDER: S-EPMC3037353 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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HTLV-1 bZIP factor induces T-cell lymphoma and systemic inflammation in vivo.

Satou Yorifumi Y Yasunaga Jun-Ichirou J Zhao Tiejun T Yoshida Mika M Miyazato Paola P Takai Ken K Shimizu Kei K Ohshima Koichi K Green Patrick L PL Ohkura Naganari N Yamaguchi Tomoyuki T Ono Masahiro M Sakaguchi Shimon S Matsuoka Masao M

PLoS pathogens 20110210 2

Human T-cell leukemia virus type 1 (HTLV-1) is the causal agent of a neoplastic disease of CD4+ T cells, adult T-cell leukemia (ATL), and inflammatory diseases including HTLV-1 associated myelopathy/tropical spastic paraparesis, dermatitis, and inflammatory lung diseases. ATL cells, which constitutively express CD25, resemble CD25+CD4+ regulatory T cells (T(reg)). Approximately 60% of ATL cases indeed harbor leukemic cells that express FoxP3, a key transcription factor for T(reg) cells. HTLV-1 e ...[more]

PMID: 21347344

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Project description:Human T-cell leukemia virus type 1 (HTLV-1) causes multiple pathological effects, ranging from a form of leukemia to a spectrum of inflammation-mediated diseases. These diseases arise from one or several infected CD4+ T cells among thousands acquiring proliferation and survival advantages and ultimately becoming pathogenic. Given the low incidence of HTLV-1-associated diseases among carriers, such cellular evolutionary processes appear to occur rarely. Therefore, infectious spread of HTLV-1 within the T-cell population may be one underlying factor influencing disease development. Free HTLV-1 virions are poorly infectious, so infection of T cells relies on direct contact between infected and target cells. Following contact, virions pass to target cells through a virological synapse or cellular conduits or are transferred to target cells within an extracellular matrix. Lymphocyte functioning antigen 1 (LFA-1) on the surface of the target cell engaging with its ligand, ICAM-1, on the surface of the infected cell (effector cell) initiates and stabilizes cell-cell contact for infection. We found that stable expression of an HTLV-1 accessory protein, HTLV-1 bZIP factor (HBZ), in Jurkat T cells increases homotypic aggregation. This phenotype was attributed to elevated ICAM-1 expression in the presence of HBZ. Using a single-cycle replication-dependent luciferase assay, we found that HBZ expression in Jurkat cells (used as effector cells) increases HTLV-1 infection. Despite this effect, HBZ could not replace the critical infection-related functions of the HTLV-1 regulatory protein Tax. However, in HTLV-1-infected T cells, knockdown of HBZ expression did lead to a decrease in infection efficiency. These overall results suggest that HBZ contributes to HTLV-1 infectivity.IMPORTANCE Human T-cell leukemia virus type 1 (HTLV-1) causes a variety of diseases, ranging from a fatal form of leukemia to immune-mediated inflammatory diseases. These diseases occur rarely, arising from one or a small subset of virally infected cells infrequently evolving into a pathogenic state. Thus, the process of HTLV-1 cell-to-cell transmission within the host helps influence the probability of disease development. HTLV-1 primarily infects T cells and initially spreads within this cell population when virally infected T cells dock to uninfected target T cells and then transfer HTLV-1 virus particles to the target cells. Here we found that the viral protein HTLV-1 bZIP factor (HBZ) promotes infectivity. HBZ accomplishes this task by increasing the surface abundance of a cellular adhesion protein known as intercellular adhesion molecule 1 (ICAM-1), which helps initiate and stabilize contact (docking) between infected and target T cells. These results define a novel and unexpected function of HBZ, diverging from its defined functions in cellular survival and proliferation.

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HTLV-1 bZIP factor induces T-cell lymphoma and systemic inflammation in vivo.

Publications

HTLV-1 bZIP factor induces T-cell lymphoma and systemic inflammation in vivo.

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