Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700019, West Bengal, India.
Infect Genet Evol. 2010 Jul;10(5):686-96. doi: 10.1016/j.meegid.2010.03.008. Epub 2010 Mar 20.
Dysregulated innate immune responses due to inappropriate signaling by Toll-like receptors (TLRs) and aberrant production of pro-inflammatory cytokines are implicated in the immunopathology and disease outcome in Plasmodium falciparum malaria. This study investigates the relationship between polymorphic variability of candidate genes including TLR-2, -4, -9, tumor necrosis factor-alpha and lymphotoxin-alpha and blood infection level in Indian mild malaria patients. Genotyping was carried out by PCR-RFLP and sequencing. Association of parasite load with genotypes was examined using model based and model free approaches. Allele and haplotype based risk assessment for disease severity was performed by stratifying the patients into high and low parasitemic groups on the basis of a threshold value derived by employing a two-component mixture model and expectation-maximization algorithm. The mean parasitemia was significantly increased for variant homozygous genotype (C/C) at TNF-alpha promoter -1031 and major homozygous genotypes encoding Asp/Asp and Thr/Thr at codons 299 and 399, respectively, on TLR4 polypeptide. Individuals harboring combined genotype C/C-Asp/Asp-Thr/Thr on TNF-alpha and TLR4 presented the highest parasite load. The frequencies of variant allele C in TNF-1031 (OR=1.91 with 95% CI=1.24-2.94) and TNF-alpha promoter haplotypes C-C-G-G (OR=1.99 with 95% CI=1.21-3.27) and C-C-G-A (OR=2.96 with 95% CI=1.19-7.37) pertaining to loci TNF-1031/-857/-308/-238 were significantly elevated in the high parasitemic group. On the contrary, the frequencies of variant allele encoding Ile at 399 (OR=0.55 with 95% CI=0.32-0.94) and haplotype corresponding to Gly-Ile (299-399) (OR=0.51 with 95% CI=0.28-0.9) in TLR4 were higher in low parasitemic group. In silico analysis indicate differential binding of transcription factors to TNF-alpha promoter haplotypes and alteration in the surface charge distribution of the TLR4 variant proteins. Our results support a genetic role of TLR4 and TNF-alpha in controlling the blood infection level in mild malaria.
由于 Toll 样受体（TLR）的信号传递不当和促炎细胞因子的异常产生，导致固有免疫反应失调，这与恶性疟原虫疟疾的免疫病理学和疾病结局有关。本研究调查了候选基因多态性变异与包括 TLR-2、-4、-9、肿瘤坏死因子-α和淋巴毒素-α在内的印度轻度疟疾患者血液感染水平之间的关系。通过 PCR-RFLP 和测序进行基因分型。使用基于模型和无模型的方法检查寄生虫负荷与基因型的关联。基于基于阈值的方法，将患者分为高和低寄生虫血症组，基于二分量混合模型和期望最大化算法，对疾病严重程度的等位基因和单倍型进行风险评估。在 TLR4 多肽上，TNF-α 启动子-1031 的变体纯合基因型（C/C）和编码 Asp/Asp 和 Thr/Thr 的主要纯合基因型分别显著增加，TLR4 的 -299 和 -399 密码子。携带 TNF-α 和 TLR4 上组合基因型 C/C-Asp/Asp-Thr/Thr 的个体表现出最高的寄生虫负荷。TNF-1031 中变体等位基因 C 的频率（OR=1.91，95%CI=1.24-2.94）和 TNF-α 启动子单倍型 C-C-G-G（OR=1.99，95%CI=1.21-3.27）和 C-C-G-A（OR=2.96，95%CI=1.19-7.37）在高寄生虫血症组中显著升高。相反，在 TLR4 中，编码 Ile 的变体等位基因 399 的频率（OR=0.55，95%CI=0.32-0.94）和相应的 Gly-Ile 单倍型（299-399）（OR=0.51，95%CI=0.28-0.9）在低寄生虫血症组中较高。计算机分析表明，转录因子对 TNF-α 启动子单倍型的结合存在差异，TLR4 变体蛋白的表面电荷分布发生改变。我们的结果支持 TLR4 和 TNF-α 在控制轻度疟疾血液感染水平方面的遗传作用。
