Data_Sheet_1_Long-Term Impact of Toxoplasma gondii Infection on Human Monocytes.docx

Toxoplasma gondii is a prevalent parasite of mammals and birds including up to 30% of humans world-wide. Primary infection of immunocompetent hosts leads to a robust cell-mediated immune response, which controls but does not clear the infection, thus enabling long-term parasite persistence in brain and muscle tissues. Chronic toxoplasmosis in mice is associated with resistance to heterologous pathogens and this has been related to increased numbers of inflammatory monocytes. Here we have analyzed whether chronic T. gondii infection impacts the subset distribution and the phenotype of peripheral human monocytes in vivo and their responses to parasite infection in vitro. CD14+ monocytes from T. gondii-seropositive blood donors expressed significantly less FcγRIII (CD16) than those from seronegative controls, but they did not show a shift in the distribution of classical, intermediate and non-classical monocyte subpopulations. Percentages of CD62L+ and CD64+ monocytes were however decreased and increased, respectively, in chronically infected individuals as compared to naïve controls. Infection of monocyte-enriched PBMCs from both seropositive and seronegative individuals with T. gondii led to an increase of CD14+CD16− classical monocytes and a decrease of CD14+CD16+ double positive monocytes. Remarkably, after in vitro parasite infection, expression of the chemokine receptor CCR2 was severely impaired in monocytes from both, individuals with chronic toxoplasmosis and seronegative controls. In contrast, only monocytes from chronically infected humans but not those from controls dose-dependently up-regulated HLA-DR, DP, DQ expression following in vitro infection. Furthermore, monocyte-enriched PBMCs from seropositive individuals up-regulated IL-12 mRNA more vigorously after in vitro infection than cells from naïve controls. Collectively, our results establish that infection of humans with T. gondii exerts long-term effects on the phenotype and responsiveness of blood monocytes. This may have important implications for innate immune responses to T. gondii and unrelated pathogens.

Gondii，一种广泛分布于哺乳动物和鸟类中的寄生虫，包括全球范围内高达30%的人类。对免疫健全宿主的原发性感染会引起强烈的细胞介导的免疫反应，该反应能够控制而非清除感染，从而使得寄生虫在脑部和肌肉组织中长期存在。慢性弓形虫病在鼠类中与对异源病原体的抵抗力相关，并已被关联到炎症单核细胞的数量增加。本研究旨在分析慢性Gondii感染是否会影响外周血单核细胞的亚群分布和表型，以及其在体外对寄生虫感染的反应。与血清阴性对照相比，来自Gondii血清阳性献血者的CD14+单核细胞表达显著较低的FcγRIII（CD16），但并未显示出经典、中间型和非经典单核细胞亚群分布的改变。与未接触过Gondii的对照组相比，慢性感染个体的CD62L+和CD64+单核细胞百分比分别降低和增加。感染来自血清阳性和血清阴性个体的单核细胞富集的PBMCs（外周血单个核细胞）后，CD14+CD16−经典单核细胞的数量增加，而CD14+CD16+双阳性单核细胞的数量减少。值得注意的是，在体外寄生虫感染后，慢性弓形虫病患者的单核细胞以及血清阴性对照者的单核细胞中，趋化因子受体CCR2的表达严重受损。相反，仅慢性感染人类而非对照组的单核细胞在体外感染后剂量依赖性地上调了HLA-DR、DP、DQ的表达。此外，来自血清阳性个体的单核细胞富集的PBMCs在体外感染后比未接触过Gondii的对照组细胞更强烈地上调了IL-12 mRNA。综上所述，我们的研究结果确立了Gondii感染对人类血单核细胞表型和反应性的长期影响，这可能对弓形虫和无关病原体引起的先天免疫反应具有重要意义。