School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, Legon, Ghana.
Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana.
Malar J. 2021 Feb 17;20(1):99. doi: 10.1186/s12936-021-03618-0.
Recent studies from different malaria-endemic regions including western Africa have now shown that Plasmodium vivax can infect red blood cells (RBCs) and cause clinical disease in Duffy-negative people, though the Duffy-negative phenotype was thought to confer complete refractoriness against blood invasion with P. vivax. The actual prevalence of P. vivax in local populations in Ghana is unknown and little information is available about the distribution of Duffy genotypes. The aim of this study was to assess the prevalence of P. vivax in both asymptomatic and symptomatic outpatients and the distribution of Duffy genotypes in Ghana.
DNA was extracted from dried blood spots (DBS) collected from 952 subjects (845 malaria patients and 107 asymptomatic persons) from nine locations in Ghana. Plasmodium species identification was carried out by nested polymerase chain reaction (PCR) amplification of the small-subunit (SSU) rRNA genes. For P. vivax detection, a second PCR of the central region of the Pvcsp gene was carried out. Duffy blood group genotyping was performed by allele-specific PCR to detect the presence of the FY allele.
No cases of P. vivax were detected in any of the samples by both PCR methods used. Majority of infections (542, 94.8%) in the malaria patient samples were due to P. falciparum with only 1 infection (0.0017%) due to Plasmodium malariae, and 2 infections (0.0034%) due to Plasmodium ovale. No case of mixed infection was identified. Of the samples tested for the FY allele from all the sites, 90.5% (862/952) had the FY allele. All positive samples were genotyped as FYB-33/FYB-33 (Duffy-negative homozygous) and therefore classified as Fy(a-b-).
No cases of P. vivax were detected by both PCRs and majority of the subjects tested carried the FY allele. The lack of P. vivax infections observed can be attributed to the high frequency of the FY allele that silences erythroid expression of the Duffy. These results provide insights on the host susceptibility for P. vivax infections that had not been investigated in Ghana before.
最近来自包括西非在内的多个疟疾流行地区的研究表明，卵形疟原虫可以感染红细胞（RBC）并导致 Duffy 阴性人群发生临床疾病，尽管 Duffy 阴性表型被认为对卵形疟原虫的红细胞入侵完全具有抵抗力。加纳当地人群中卵形疟原虫的实际流行情况尚不清楚，关于 Duffy 基因型的分布也知之甚少。本研究旨在评估无症状和有症状门诊患者中卵形疟原虫的流行情况以及加纳的 Duffy 基因型分布。
从加纳 9 个地点的 952 名受试者（845 名疟疾患者和 107 名无症状者）采集的干血斑（DBS）中提取 DNA。通过小亚单位（SSU）rRNA 基因的巢式聚合酶链反应（PCR）扩增进行疟原虫种鉴定。为了检测卵形疟原虫，对 Pvcsp 基因的中心区域进行了第二次 PCR。通过等位基因特异性 PCR 检测 FY 等位基因来进行 Duffy 血型基因型检测。
两种 PCR 方法均未在任何样本中检测到卵形疟原虫。在疟疾患者样本中，大多数感染（542 例，94.8%）是由恶性疟原虫引起的，只有 1 例（0.0017%）是由间日疟原虫引起的，2 例（0.0034%）是由卵形疟原虫引起的。未发现混合感染。在对所有地点的 FY 等位基因进行检测的样本中，90.5%（862/952）携带 FY 等位基因。所有阳性样本均被鉴定为 FYB-33/FYB-33（Duffy 阴性纯合子），因此被归类为 Fy(a-b-)。
两种 PCR 均未检测到卵形疟原虫，且大多数检测的受试者携带 FY 等位基因。观察到的卵形疟原虫感染缺失可归因于 FY 等位基因的高频，该基因沉默了红细胞上 Duffy 的表达。这些结果为以前在加纳未进行过的卵形疟原虫感染宿主易感性提供了新的认识。
