Raballah Evans, Kempaiah Prakasha, Karim Zachary, Orinda George O, Otieno Michael F, Perkins Douglas J, Ong'echa John Michael
University of New Mexico Laboratories of Parasitic and Viral Diseases, Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
Department of Medical Laboratory Sciences, Masinde Muliro University of Science and Technology, Kakamega, Kenya.
PLoS One. 2017 Apr 20;12(4):e0175864. doi: 10.1371/journal.pone.0175864. eCollection 2017.
In Plasmodium falciparum holoendemic transmission regions of western Kenya, life-threatening pediatric malaria manifests primarily as severe malarial anemia (SMA, Hb≤6.0 g/dL with any density parasitemia). To determine the role that CD4+ T-cell-driven inflammatory responses have in the pathogenesis of SMA, peripheral CD4+ T-cell populations and their intracellular production of pro-inflammatory cytokines (IFN-γ and IL-17) were characterized in children aged 12-36 months of age stratified into two groups: non-severe malarial anemia (non-SMA, Hb≥6.0 g/dL, n = 50) and SMA (n = 39). In addition, circulating IFN-γ and IL-17 were measured as part of a Cytokine 25-plex Antibody Bead Kit, Human (BioSource™ International). Children with SMA had higher overall proportions of circulating lymphocytes (P = 0.003) and elevated proportions of lymphocytes expressing IFN-γ (P = 0.014) and comparable IL-17 (P = 0.101). In addition, SMA was characterized by decreased memory-like T-cells (CD4+CD45RA-) expressing IL-17 (P = 0.009) and lower mean fluorescence intensity in memory-like CD4+ T-cells for both IFN-γ (P = 0.063) and IL-17 (P = 0.006). Circulating concentrations of IFN-γ were higher in children with SMA (P = 0.009), while IL-17 levels were comparable between the groups (P = 0.164). Furthermore, circulating levels of IFN-γ were negatively correlated with IL-17 levels in both groups of children (SMA: r = -0.610, P = 0.007; and non-SMA: r = -0.516, P = 0.001), while production of both cytokines by lymphocytes were positively correlated (SMA: r = 0.349, P = 0.037; and non-SMA: r = 0.475, P = 0.001). In addition, this correlation was only maintained by the memory-like CD4+ T cells (r = 0.365, P = 0.002) but not the naïve-like CD4+ T cells. However, circulating levels of IFN-γ were only associated with naïve-like CD4+ T cells producing IFN-γ (r = 0.547, P = 0.028), while circulating levels of IL-17 were not associated with any of the cell populations. Taken together, these results suggest that enhanced severity of malarial anemia is associated with higher overall levels of circulating lymphocytes, enhanced intracellular production of IFN-γ by peripheral lymphocytes and high circulating IFN-γ levels. In addition, the observed inverse relationship between the circulating levels of IFN-γ and IL-17 together with the reduction in the levels of memory-like CD4+ T cells expressing IL-17 in children with SMA may suggest possible relocation of these cells in the deeper tissues for their pathological effect.
在肯尼亚西部恶性疟原虫高度流行传播地区，危及生命的儿童疟疾主要表现为严重疟疾贫血（SMA，血红蛋白≤6.0 g/dL且有任何密度的疟原虫血症）。为确定CD4 + T细胞驱动的炎症反应在SMA发病机制中的作用，对12至36个月大的儿童外周血CD4 + T细胞群体及其促炎细胞因子（IFN-γ和IL-17）的细胞内产生情况进行了表征，这些儿童分为两组：非严重疟疾贫血（非SMA，血红蛋白≥6.0 g/dL，n = 50）和SMA（n = 39）。此外，作为人细胞因子25种抗体微珠试剂盒（BioSource™ International）的一部分，检测了循环中的IFN-γ和IL-17。SMA患儿循环淋巴细胞的总体比例较高（P = 0.003），表达IFN-γ的淋巴细胞比例升高（P = 0.014），而IL-17比例相当（P = 0.101）。此外，SMA的特征是表达IL-17的记忆样T细胞（CD4 + CD45RA-）减少（P = 0.009），且记忆样CD4 + T细胞中IFN-γ（P = 0.063）和IL-17（P = 0.006）的平均荧光强度较低。SMA患儿循环中的IFN-γ浓度较高（P = 0.009），而两组间IL-17水平相当（P = 0.164）。此外，两组儿童中循环IFN-γ水平与IL-17水平均呈负相关（SMA组：r = -0.610，P = 0.007；非SMA组：r = -0.516，P = 0.001），而淋巴细胞产生的两种细胞因子呈正相关（SMA组：r = 0.349，P = 0.037；非SMA组：r = 0.475，P = 0.001）。此外，这种相关性仅在记忆样CD4 + T细胞中维持（r = 0.365，P = 0.002），而在初始样CD4 + T细胞中则不然。然而，循环IFN-γ水平仅与产生IFN-γ的初始样CD4 + T细胞相关（r = 0.547，P = 0.028），而循环IL-17水平与任何细胞群体均无关联。综上所述，这些结果表明，疟疾贫血严重程度的增加与循环淋巴细胞的总体水平升高、外周淋巴细胞IFN-γ细胞内产生增加以及循环IFN-γ水平升高有关。此外，SMA患儿循环IFN-γ和IL-17水平之间观察到的负相关关系以及表达IL-17的记忆样CD4 + T细胞水平的降低，可能表明这些细胞可能迁移至更深层组织发挥其病理作用。
