Prevalence and fitness of drug resistant minority variant mutations in Plasmodium

疟原虫耐药少数变异突变的流行率和适应性

• 批准号: 7471734
• 负责人: Steven Richard Meshnick
• 金额: $ 21.9万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-02-01 至 2010-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7471734
• 关键词: Africa South of the Sahara; Area; Biological Assay; Biological Markers; Chloroquine; Chloroquine resistance; Congo; Cost Measures; Costs and Benefits; Democratic Republic of the Congo; Detection; Disease; Drug resistance; Early Diagnosis; Enrollment; Falciparum Malaria; Folic Acid Antagonists; Frequencies; Genetic; Growth; High Prevalence; Human; Individual; Madagascar; Malaria; Malawi; Measures; Medical Surveillance; Methods; Minority; Mutation; Parasite resistance; Parasites; Patients; Pharmaceutical Preparations; Pilot Projects; Plasmodium; Policies; Polymerase Chain Reaction; Population; Prevalence; Public Health; Pyrimethamine-Sulfadoxine; Relative (related person); Resistance; Sampling; Standards of Weights and Measures; Surveillance Methods; Testing; Time; Variant; Zambia; cost; fitness; mutant; pressure; programs; tool; transmission process

DESCRIPTION (provided by applicant): Drug-resistant P. falciparum malaria is a major public health problem. Molecular markers for most types of drug resistance have been identified and could serve as surveillance tools. However, individuals in high-transmission areas, like sub-Saharan Africa, usually carry many genetically diverse P. falciparum subpopulations ("variants"). Standard PCR methods are incapable of detecting drug-resistance mutations in variants representing <20% of the parasites in an individual host ("minority variants"). Thus, standard assays underestimate the prevalence of patients infected with resistant parasites because they miss patients with resistant minority variants. We have developed Heteroduplex Tracking Assays (HTAs) which can detect drug-resistant minority variants and accurately measure the relative abundance of variant populations. In a Malawi pilot study, we demonstrated a high prevalence of minority variant pfcrt76 mutations (a marker for chloroquine resistance) which were missed by standard PCR. We have now developed HTA's for minority variants at 3 other important loci (dhfr59, dhfr164, dhps540, for antifolate resistance). We will use these assays to (1) determine whether the prevalence of drug-resistant P. falciparum is higher when measured by HTA than by standard PCR; and (2) measure in-host fitness gains and losses of resistant minority variants in drug- treated and untreated individuals. Prevalence of pfcrt76, dhfr59, dhfr164 and/or dhps540 will be measured by HTA and standard PCR cross-sectionally in samples from Malawi, Zambia, Madagascar, and the DR Congo. Pfcrt76 and dhfr164 fitness will be measured in paired enrollment and recrudescent samples from sulfadoxine-pyrimethamine (SP)- treated patients in Malawi and chloroquine-treated patients in Madagascar. The results of this study have important public health implications. The detection of drug-resistant minority variants - with proven fitness - could enable earlier detection of emerging drug- resistance and greater lead-time to plan changes in drug policy. PUBLIC HEALTH RELEVANCE Better surveillance methods for drug-resistant malaria could be of great benefit to malaria control programs. We are trying to develop a method to measure drug-resistant parasites even when they are the minority of parasites in a single host. This could permit the earlier detection of emerging drug resistance.

描述（由申请人提供）：耐药性恶性疟原虫疟疾是一个主要的公共卫生问题。大多数类型的耐药性的分子标记已经被鉴定出来，并且可以作为监测工具。然而，高传播地区（如撒哈拉以南非洲）的个体通常携带许多遗传多样性的恶性疟原虫亚群（“变种”）。标准 PCR 方法无法检测代表个体宿主中 <20% 寄生虫的变体（“少数变体”）的耐药突变。因此，标准检测低估了感染耐药寄生虫的患者的患病率，因为它们错过了携带少数耐药变异的患者。我们开发了异源双链体追踪测定 (HTA)，它可以检测耐药少数变异并准确测量变异群体的相对丰度。在马拉维的一项试点研究中，我们证明了少数变异 pfcrt76 突变（氯喹耐药性标记）的流行率很高，而标准 PCR 却漏掉了这些突变。我们现在已经开发了针对其他 3 个重要基因座（dhfr59、dhfr164、dhps540，用于抗叶酸剂耐药性）的少数变异的 HTA。我们将使用这些检测方法来 (1) 确定通过 HTA 测量的耐药性恶性疟原虫的患病率是否高于通过标准 PCR 测量的情况； (2) 测量经过药物治疗和未经治疗的个体中耐药少数变异的宿主适应性的增加和损失。将通过 HTA 和标准 PCR 横断面测量来自马拉维、赞比亚、马达加斯加和刚果民主共和国的样本中 pfcrt76、dhfr59、dhfr164 和/或 dhps540 的患病率。将在马拉维接受磺胺多辛-乙胺嘧啶 (SP) 治疗的患者和马达加斯加接受氯喹治疗的患者的配对入组和复发样本中测量 Pfcrt76 和 dhfr164 适合度。这项研究的结果具有重要的公共卫生意义。检测出耐药性少数变异（经证实适用性）可以更早地检测新出现的耐药性，并为规划药物政策的变化提供更长的准备时间。公共卫生相关性 更好的耐药性疟疾监测方法可能对疟疾控制规划大有裨益。我们正在尝试开发一种方法来测量耐药寄生虫，即使它们是单一宿主中的少数寄生虫。这可以允许及早检测新出现的耐药性。