海地人群红细胞无反应性 Duffy 抗原基因型频率较高且无间日疟原虫感染。
High frequency of the erythroid silent Duffy antigen genotype and lack of Plasmodium vivax infections in Haiti.
机构信息
Department of Environmental and Global Health, University of Florida, PO Box 100188, Gainesville, FL 32610, USA.
出版信息
Malar J. 2013 Jan 24;12:30. doi: 10.1186/1475-2875-12-30.
BACKGROUND
Malaria is a significant public health concern in Haiti where approximately 30,000 cases are reported annually with CDC estimates as high as 200,000. Malaria infections in Haiti are caused almost exclusively by Plasmodium falciparum, while a small number of Plasmodium malariae and an even smaller number of putative Plasmodium vivax infections have been reported. The lack of confirmed P. vivax infections in Haiti could be due to the genetic background of native Haitians. Having descended from West African populations, many Haitians could be Duffy negative due to a single nucleotide polymorphism from thymine to cytosine in the GATA box of the promoter region of the Duffy antigen receptor for chemokines (DARC) gene. This mutation, encoded by the FYES allele, eliminates the expression of the Duffy antigen on erythrocytes, which reduces invasion by P. vivax. This study investigated the frequency of the FYES allele and P. vivax infections in malaria patients with the goal of uncovering factors for the lack of P. vivax infections reported in Haiti.
METHODS
DNA was extracted from dried blood spots collected from malaria patients at four clinic locations in Haiti. The samples were analysed by polymerase chain reaction (PCR) for the presence of the P. vivax small subunit ribosomal RNA gene. PCR, sequencing, and restriction enzyme digestion were used to detect the presence of the FYES allele. Matched samples were examined for both presence of P. vivax and the FYES allele.
RESULTS
No cases of P. vivax were detected in any of the samples (0/136). Of all samples tested for the FYES allele, 99.4% had the FYES allele (163/164). Of the matched samples, 99% had the FYES allele (98/99).
CONCLUSIONS
In this preliminary study, no cases of P. vivax were confirmed by PCR and 99% of the malaria patients tested carried the FYES allele. The high frequency of the FYES allele that silences erythroid expression of the Duffy antigen offers a biologically plausible explanation for the lack of P. vivax infections observed. These results provide insights on the host susceptibility for P. vivax infections that has never before been investigated in Haiti.
背景
疟疾是海地的一个重大公共卫生问题，每年报告约 3 万例病例，而美国疾病控制与预防中心的估计则高达 20 万例。海地的疟疾感染几乎完全由恶性疟原虫引起，而少数间日疟原虫和更少的疑似卵形疟原虫感染也有报道。海地没有确诊的间日疟原虫感染可能是由于海地本地人的遗传背景所致。许多海地人源自西非人口，由于趋化因子的 Duffy 抗原受体（DARC）基因启动子区域 GATA 盒中的胸腺嘧啶到胞嘧啶的单核苷酸多态性，他们可能是 Duffy 阴性。该突变由 FYES 等位基因编码，消除了红细胞上 Duffy 抗原的表达，从而减少了间日疟原虫的入侵。本研究调查了疟疾患者中 FYES 等位基因和间日疟原虫感染的频率，旨在揭示海地报告的间日疟原虫感染缺乏的因素。
方法
从海地四个诊所的疟疾患者采集的干血斑中提取 DNA。通过聚合酶链反应（PCR）分析样本中是否存在间日疟原虫小亚基核糖体 RNA 基因。PCR、测序和限制性内切酶消化用于检测 FYES 等位基因的存在。对匹配样本同时进行间日疟原虫和 FYES 等位基因的检测。
结果
在任何样本中均未检测到间日疟原虫（0/136）。在所有测试 FYES 等位基因的样本中，99.4%（163/164）携带 FYES 等位基因。在匹配的样本中，99%（98/99）携带 FYES 等位基因。
结论
在这项初步研究中，PCR 未确认有间日疟原虫病例，99%的疟疾患者携带 FYES 等位基因。FYES 等位基因沉默红细胞上 Duffy 抗原的表达频率很高，这为观察到的间日疟原虫感染缺乏提供了一个生物学上合理的解释。这些结果为以前从未在海地进行过调查的间日疟原虫感染宿主易感性提供了新的见解。
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