Department of Biomolecular Genetics, University of Rochester Medical Center, Rochester, New York, United States of America.
PLoS Pathog. 2012;8(4):e1002635. doi: 10.1371/journal.ppat.1002635. Epub 2012 Apr 5.
Leishmaniasis is a parasitic disease that is widely prevalent in many tropical and sub-tropical regions of the world. Infection with Leishmania has been recognized to induce a striking acceleration of Human Immunodeficiency Virus Type 1 (HIV-1) infection in coinfected individuals through as yet incompletely understood mechanisms. Cells of the monocyte/macrophage lineage are the predominant cell types coinfected by both pathogens. Monocytes and macrophages contain extremely low levels of deoxynucleoside triphosphates (dNTPs) due to their lack of cell cycling and S phase, where dNTP biosynthesis is specifically activated. Lentiviruses, such as HIV-1, are unique among retroviruses in their ability to replicate in these non-dividing cells due, at least in part, to their highly efficient reverse transcriptase (RT). Nonetheless, viral replication progresses more efficiently in the setting of higher intracellular dNTP concentrations related to enhanced enzyme kinetics of the viral RT. In the present study, in vitro infection of CD14+ peripheral blood-derived human monocytes with Leishmania major was found to induce differentiation, marked elevation of cellular p53R2 ribonucleotide reductase subunit and R2 subunit expression. The R2 subunit is restricted to the S phase of the cell cycle. Our dNTP assay demonstrated significant elevation of intracellular monocyte-derived macrophages (MDMs) dNTP concentrations in Leishmania-infected cell populations as compared to control cells. Infection of Leishmania-maturated MDMs with a pseudotyped GFP expressing HIV-1 resulted in increased numbers of GFP+ cells in the Leishmania-maturated MDMs as compared to control cells. Interestingly, a sub-population of Leishmania-maturated MDMs was found to have re-entered the cell cycle, as demonstrated by BrdU labeling. In conclusion, Leishmania infection of primary human monocytes promotes the induction of an S phase environment and elevated dNTP levels with notable elevation of HIV-1 expression in the setting of coinfection.
利什曼病是一种寄生虫病，广泛流行于世界上许多热带和亚热带地区。感染利什曼原虫已被证实通过目前尚未完全了解的机制，显著加速了合并感染个体中人类免疫缺陷病毒 1（HIV-1）的感染。单核细胞/巨噬细胞谱系的细胞是这两种病原体合并感染的主要细胞类型。由于缺乏细胞周期和 S 期，单核细胞和巨噬细胞中的脱氧核苷三磷酸（dNTP）水平极低，而 S 期是 dNTP 生物合成特异性激活的时期。慢病毒，如 HIV-1，在其能够在这些非分裂细胞中复制的能力方面与逆转录病毒不同，至少部分原因是其高效的逆转录酶（RT）。尽管如此，病毒复制在与增强的病毒 RT 酶动力学相关的更高细胞内 dNTP 浓度的情况下进展得更顺利。在本研究中，发现体外感染单核细胞来源的 CD14+外周血人类单核细胞的利什曼原虫可诱导分化，细胞 p53R2 核糖核苷酸还原酶亚基和 R2 亚基表达显著升高。R2 亚基仅限于细胞周期的 S 期。我们的 dNTP 测定表明，与对照细胞相比，利什曼原虫感染细胞群中的单核细胞衍生的巨噬细胞（MDM）的细胞内 dNTP 浓度显著升高。用表达 GFP 的假型 HIV-1 感染利什曼原虫成熟的 MDM 后，与对照细胞相比，GFP+细胞的数量在利什曼原虫成熟的 MDM 中增加。有趣的是，发现利什曼原虫成熟的 MDM 中有一个亚群重新进入细胞周期，这通过 BrdU 标记证明。总之，利什曼原虫感染原代人类单核细胞可促进 S 期环境的诱导，并在合并感染时显著提高 dNTP 水平，从而提高 HIV-1 的表达。
