Hematopoietic Stem Cell Infected with HTLV-1 Functions As a Viral Reservoir In Vivo

• Published in: Blood 2016-12, Vol.128 (22), p.1343-1343
• Main Authors: Yasunaga, Jun-ichirou, Furuta, Rie, Miura, Michi, Sugata, Kenji, Saito, Akatsuki, Hirofumi, Akari, Ueno, Takaharu, Takenouchi, Norihiro, Fujisawa, Jun-ichi, Shimizu, Masakazu, Matsuda, Fumihiko, Melamed, Anat, Bangham, Charles R.M., Matsuoka, Masao
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V128.22.1343.1343

▪ Human T-cell leukemia virus type 1 (HTLV-1) is a causative agent of a malignant disease of peripheral CD4+ T cells called adult T-cell leukemia-lymphoma (ATL) and several inflammatory diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Although major target of HTLV-1 is CD4+ T cells, other hematopoietic cells such as CD8+ T cells and monocytes are also infected with HTLV-1. Since the receptors of HTLV-1 are glucose transporter 1 and neuropilin 1, which are found on various cell surfaces, it is possible that HTLV-1 infects various hematopoietic cells and hematopoietic stem cells (HSCs). However, the previous studies could not detect HTLV-1 in HSCs. To assess the distribution of infected cells and expression of viral genes in various tissues, a nonhuman primate model, Japanese macaques (JMs) infected with simian T-cell leukemia virus type 1 (STLV-1) was utilized in this study. STLV-1 is a close relative of HTLV-1, and the dynamics of viral replication and proliferation of infected cells are very similar to each other. Indeed, STLV-1 caused malignant lymphomas in STLV-1 infected monkeys. Therefore, STLV-1 infected JMs are good models of HTLV-1 carriers. Using this model, we first analyzed transcription level of two viral genes, tax and STLV-1 bZIP factor, in multiple tissues, and found that tax was highly expressed in bone marrow compared to other tissues. Since Tax is a potent activator of viral transcription, this result suggested that viral replication occurred in bone marrow. To evaluate which cells express Tax in bone marrow, we performed flow cytometric analysis of bone marrow mononuclear cells from STLV-1 infected monkeys, and found that not only CD4+ T cells but also non T cells (CD3 negative cells) expressed Tax. To determine whether hematopoietic stem cells are infected with HTLV-1, we next performed highthroughput sequencing of HTLV-1 integration sites in multiple cell lineages using a next generation sequencer. Since HTLV-1 is randomly integrated into genome of infected cells, and each infected cell can proliferate clonally, we can interpret that cells sharing same integration sites are derived from the same precursor cell. Blood samples from patients with HAM/TSP were separated into five cell types: CD4+ T cells, CD8+ T cells, B cells, monocytes, and neutrophils. Integration sites of HTLV-1 provirus were analyzed by next generation sequencing using different chips for each cell type in order to avoid cross cont