Pinto Daniel O, DeMarino Catherine, Pleet Michelle L, Cowen Maria, Branscome Heather, Al Sharif Sarah, Jones Jennifer, Dutartre Helene, Lepene Benjamin, Liotta Lance A, Mahieux Renaud, Kashanchi Fatah
Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA, United States.
Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States.
Front Microbiol. 2019 Sep 18;10:2147. doi: 10.3389/fmicb.2019.02147. eCollection 2019.
Human T-cell leukemia virus-1 (HTLV-1) is a neglected and incurable retrovirus estimated to infect 5 to 10 million worldwide. Specific indigenous Australian populations report infection rates of more than 40%, suggesting a potential evolution of the virus with global implications. HTLV-1 causes adult T-cell leukemia/lymphoma (ATLL), and a neurological disease named HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). Even though HTLV-1 transmission primarily occurs from cell-to-cell, there is still a gap of knowledge regarding the mechanisms of viral spread and disease progression. We have recently shown that Extracellular Vesicles (EVs) ubiquitously produced by cells may be used by HTLV-1 to transport viral proteins and RNA, and elicit adverse effects on recipient uninfected cells. The viral proteins Tax and HBZ are involved in disease progression and impairment of autophagy in infected cells. Here, we show that activation of HTLV-1 via ionizing radiation (IR) causes a significant increase of intracellular Tax, but not EV-associated Tax. Also, lower density EVs from HTLV-1-infected cells, separated by an Iodixanol density gradient, are positive for gp61+++/Tax+++/HBZ+ proteins (HTLV-1 EVs). We found that HTLV-1 EVs are not infectious when tested in multiple cell lines. However, these EVs promote cell-to-cell contact of uninfected cells, a phenotype which was enhanced with IR, potentially promoting viral spread. We treated humanized NOG mice with HTLV-1 EVs prior to infection and observed an increase in viral RNA synthesis in mice compared to control (EVs from uninfected cells). Proviral DNA levels were also quantified in blood, lung, spleen, liver, and brain post-treatment with HTLV-1 EVs, and we observed a consistent increase in viral DNA levels across all tissues, especially the brain. Finally, we show direct implications of EVs in viral spread and disease progression and suggest a two-step model of infection including the release of EVs from donor cells and recruitment of recipient cells as well as an increase in recipient cell-to-cell contact promoting viral spread.
人类T细胞白血病病毒1型（HTLV-1）是一种被忽视且无法治愈的逆转录病毒，据估计全球有500万至1000万人感染该病毒。澳大利亚特定原住民群体报告的感染率超过40%，这表明该病毒可能发生了具有全球影响的演变。HTLV-1可导致成人T细胞白血病/淋巴瘤（ATLL）以及一种名为HTLV-1相关脊髓病/热带痉挛性截瘫（HAM/TSP）的神经系统疾病。尽管HTLV-1主要通过细胞间传播，但在病毒传播机制和疾病进展方面仍存在知识空白。我们最近发现，细胞普遍产生的细胞外囊泡（EVs）可能被HTLV-1用于运输病毒蛋白和RNA，并对未感染的受体细胞产生不利影响。病毒蛋白Tax和HBZ参与疾病进展以及感染细胞中自噬的损伤。在此，我们表明通过电离辐射（IR）激活HTLV-1会导致细胞内Tax显著增加，但与EV相关的Tax不会增加。此外，通过碘克沙醇密度梯度分离的来自HTLV-1感染细胞的低密度EVs对gp61+++/Tax+++/HBZ+蛋白呈阳性（HTLV-1 EVs）。我们发现，在多种细胞系中进行测试时，HTLV-1 EVs没有传染性。然而，这些EVs促进了未感染细胞之间的细胞间接触，这种表型在IR作用下增强，可能促进病毒传播。我们在感染前用HTLV-1 EVs处理人源化NOG小鼠，与对照组（来自未感染细胞的EVs）相比，观察到小鼠体内病毒RNA合成增加。在用HTLV-1 EVs处理后，还对血液、肺、脾、肝和脑中的前病毒DNA水平进行了定量，我们观察到所有组织中的病毒DNA水平均持续增加，尤其是在脑中。最后，我们展示了EVs在病毒传播和疾病进展中的直接影响，并提出了一个两步感染模型，包括从供体细胞释放EVs、招募受体细胞以及增加受体细胞间接触以促进病毒传播。
