抗氯喹恶性疟的测定和治疗

抗氯喹恶性疟的测定和治疗张家埙恶性疟原虫对氯喹产生抗药性，改变了全球的抗疟形势，大规模的抗疟计划受到挫折。后来发现恶性疟原虫对多种抗疟药也产生抗性，甚至同一株恶性疟原虫对几种抗疟药物产生抗性，即多重抗性。我国抗氯喹恶性疟地理分布的调查结果表明，云南、...     

恶性疟原虫抗药性分子标记检测方法研究进展

疟疾是非洲和东南亚地区流行的重要热带病,严重威胁着当地居民的身体健康。随着恶性疟原虫对抗疟药物抗性的产生与蔓延,全球消除疟疾目标的实现面临着新的挑战。目前恶性疟原虫抗药性监测方法主要包括体内药效试验法、体外药敏检测法和抗性分子标记检测法,其中抗性分子标记检测法被广泛应用。本文就恶性疟原虫抗药性分子标记检测方法研究进展作一综述。     

恶性疟原虫药物抗性相关分子标记研究进展

药物治疗是疟疾防治的重要手段,但是却面临着抗疟药抗性的威胁。近年来,随着分子生物学的发展,越来越多的分子标记用于疟原虫抗药性监测。本文就恶性疟原虫常见抗药性相关分子标记的研究进展作一综述。     

恶性疟原虫对青蒿素类药物抗药性的最新研究进展

恶性疟是一种致死性很高的全球性寄生虫病。由于长期抗疟药的使用,目前恶性疟原虫对主要抗疟药物普遍产生抗药性,青蒿素类药物是在氯喹、奎宁抗药性产生后的主要替代治疗药,也是至今唯一没有出现普遍抗药性的抗疟药。但是,近年不少研究和临床观察发现青蒿素类药物的敏感性正逐渐下降,提示恶性疟原虫对青蒿素及其衍生物的抗药性正在形成。本文就近期青蒿素药抗药性的现状及其机制的研究进展情况进行了综述。     

疟原虫的抗药性与抗疟药的合理应用

疟原虫的抗药性是指在患者对药物能忍受的情况下,给患者推荐剂量或高于推荐剂量的抗疟药,并证明药物已被吸收,血药浓度已达到可治愈的水平,疟原虫仍具存活或繁殖的能力[1]。在人体4种疟原虫中,恶性疟原虫和间日疟原虫对抗疟药均易产生抗性,三日疟原虫和卵形疟原虫尚无抗性报道。其中恶性疟原虫的抗性尤为重要,不仅表现为抗性率及抗性程度高、地理分布广,而且还可导致高死亡率。1恶性疟原虫的抗药性目前恶性疟原虫几乎对现有的各种抗疟药都产生了抗性。早在20世纪初已发现对奎宁产生抗性,20世纪40年代后期对氯胍和环氯胍产生抗性,50年代中期…     

恶性疟原虫对青蒿素产生抗性的研究进展

青蒿素及其衍生物是我国发明的强效抗疟药,WHO已推荐以青蒿素为基础的联合用药(ACTs)为治疗恶性疟的一线药物。青蒿素及其衍生物的应用已使全球疟疾流行得到了有效控制,疟疾发病率和死亡率逐年下降。但近年来,在东南亚多个地区陆续报道恶性疟原虫(Plasmodium falciparum)对青蒿素类药物产生抗性,并有进一步扩散的趋势,这已严重威胁到全球疟疾防治和消除疟疾计划的实施。本文综述近年来恶性疟原虫对青蒿素产生抗性研究领域的相关研究进展,包括青蒿素抗药性的检测方法、抗性相关的分子标记、抗性虫株的起源及传播流行等。     

用甲氟喹-强力霉素和青蒿酯钠-强力霉素治疗急性无并发症恶性疟的随机试验

在泰国,由于恶性疟原虫对青蒿素衍生物之外所有抗疟药的抗性增加,使急性无并发症恶性疟的治疗变得更困难。甲氟喹已用于治疗具有多种药物抗性的疟疾,但单独使用时已出现抗药性。一种新的抗疟药——氯氟菲醇具有较好的耐受性,但治愈率较低。青     

我国恶性疟抗药性监测与抗疟药的合理应用

研制成功涂药板和便于现场使用的培养基后,1980-2003年,采用体内四周法和体外微量法开展了我国抗氯喹恶性疟的抗性程度及地理分布;停用或减少使用氯喹防治恶性疟后,恶性疟原虫对氯喹抗性的消长及我国恶性疟原虫对常用抗疟药敏感性等调查。结果显示,有恶性疟流行的八省(区)均有抗氯喹恶性疟存在,其中海南和云南两省抗性程度高,分布地区广。停用或减少使用氯喹后,恶性疟原虫对氯喹抗性逐渐降低。海南和云南两省恶性疟原虫对氯喹、氨酚喹和哌喹有高度抗性,对咯萘啶和青蒿素类药物敏感,但敏感性在逐渐降低。根据调查结果,制定了抗疟药使用原则和用药方案,停止或减少使用已有抗性的抗疟药,推荐应用青蒿素类药物和咯萘啶及其复方。使抗疟药能合理规范使用,促进了疟疾防治,疟疾发病逐年降低,恶性疟流行区逐渐缩小。     

恶性疟原虫药物敏感性体外测定方法研究进展

随着抗疟药的广泛使用,在世界各疟疾流行区的恶性疟原虫对氯喹普遍产生了抗药性。监测恶性疟原虫对各种抗疟药的敏感性显得十分必要。本文对近年来恶性疟原虫药物敏感性体外测定方法及研究进展做一综述。     

恶性疟原虫多药抗性蛋白pfMRPl研究新进展

近几年在疟疾的治疗中,抗疟药抗药性的产生成为疟疾控制的最大难题,随着分子生物学技术的发展,从分子水平上研究恶性疟原虫的抗药性的产生取得了重大突破性进展,恶性疟原虫多药抗性蛋白声fMRPl（TheP．falciparumMultidrugResist—anteProtein1）被认为是和多种药物抗性产生有关的ABC转运蛋白,与抗疟药抗性的产生有密切关系。     

Molecular markers for drug resistance in malaria: use in treatment, diagnosis and epidemiology

PURPOSE OF REVIEW: Malaria and the increasing role of drug resistance as an obstacle to its control are global problems. The identification and implications of molecular markers for antimalarial drug resistance - the subject of this review - are key issues in elucidating and eventually controlling resistance. RECENT FINDINGS: Recent achievements include the successful expression of the Plasmodium falciparum chloroquine resistance transporter gene, pfcrt, in yeast, the identification of polymorphisms on the gamma-glutamylcysteine synthetase gene, ggcs, as potential determinants of chloroquine and mefloquine resistance, and the usefulness of a combined Plasmodium falciparum dihydrofolate reductase gene, pfdhfr, 59ARG and Plasmodium falciparum dihydropteroate synthase gene, pfdhps, 540GLU marker in reliably representing resistance to antifolates. Moreover, treatment with sulfadoxine-pyrimethamine in the presence of pfdhfr 108ASP alone delayed parasite clearance and increased gametocytogony without an overt loss of the overall therapeutic efficacy of the drug. SUMMARY: The use of pfdhfr and pfdhps markers in determining antifolate resistance of Plasmodium falciparum has been consolidated. Similar progress has been made with pfcrt markers for chloroquine resistance, auguring well the operational deployment of molecular techniques. Regarding the molecular basis of resistance to arylaminoalcohols, related drugs, and artemisinin and its derivatives, answers remain elusive, but there are promising new leads.     

Epidemiology of drug-resistant malaria in Republic of Congo: using molecular evidence for monitoring antimalarial drug resistance combined with assessment of antimalarial drug use

In Congo, urgent efforts are needed to help with the revision of the national antimalarial drug policy. Despite its high resistance level, chloroquine (CQ) is still extensively used as the first-line treatment for uncomplicated Plasmodium falciparum malaria. The study was conducted in children under 5 years with uncomplicated malaria in Pointe-Noire and Brazzaville, the two largest cities that contain approximately 60% of the population of Congo. We investigated by polymerized chain reaction and sequencing methods the frequency distribution of molecular markers for antimalarial drug resistance, including mutations in P. falciparum chloroquine resistance transporter (pfcrt) gene associated with CQ resistance and mutations in dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes conferring resistance to sulphadoxine/pyrimethamine (SP) among pre-treatment P. falciparum isolates, as well as assessing antimalarial drug use in the community. pfcrt (K76T) mutation was present in most isolates (96.4%, n = 138) and high frequency (69.2%, n = 133) of triple-mutant dhfr-S108N, N51I, C59R was observed. The quintuple mutant (dhfr-S108N, N51I, C59R and dhps-A437G or S436A, K540E) considered as molecular marker for SP treatment failure was not found because dhps-K540E mutation was absent in isolates tested; this is a clear evidence for the excellent efficacy of SP that we previously described in the same population. The complete absence of the dhps-K540E mutation is a deterrent component for using this molecular marker as an early warning tool for SP resistance testing in that population. Poor compliance issues related to the antimalarial drug use including inappropriate manufacturing practices reported in this study require intensive attention and should be taken into account when implementing drug policy change. If Congo changes its treatment policy from CQ to SP monotherapy, this will not last long. The strategy of combining SP with other affordable and effective antimalarial drugs such as the artemisinin derivatives to improve efficacy and to delay the development of parasite resistance is essential.     

A better resolution for integrating methods for monitoring Plasmodium falciparum resistance to antimalarial drugs

Effective chemotherapy is the mainstay of malaria control. However, resistance of falciparum malaria to antimalarial drugs compromised the efforts to eliminate the disease and led to the resurgence of malaria epidemics. Three main approaches are used to monitor antimalarial drug efficacy and drug resistance; namely, in vivo trials, in vitro/ex vivo assays and molecular markers of drug resistance. Each approach has its implications of use as well as its advantages and drawbacks. Therefore, there is a need to use an integrated approach that would give the utmost effect to detect resistance as early as its emergence and to track it once spread. Such integration becomes increasingly needed in the era of artemisinin-based combination therapy as a forward action to deter resistance. The existence of regional and global networks for the standardization of methodology, provision of high quality reagents for the assessment of antimalarial drug resistance and dissemination of open-access data would help in approaching an integrated resistance surveillance system on a global scale.     

Avian mortality surveillance for West Nile virus in Colorado

A total of 248 Plasmodium falciparum isolates were sampled in travelers with malaria who came to Marseille, France from Comoros to investigate in vitro activities of antimalarial drugs and molecular markers of drug resistance. Of the 248 isolates, 126 were maintained in culture. Of these, 53% were resistant to chloroquine, and 3% had reduced susceptibility to quinine, mefloquine, and atovaquone; 1% had reduced susceptibility to halofantrine and dihydroartemisinin; 7% had reduced susceptibility to monodesethylamodiaquine; 37% had reduced susceptibility to cycloguanil; and none had reduced susceptibility to lumefantrine. Resistance-associated point mutations were screened in 207 isolates. No mutations in the cytochrome b gene were found. Of the 207 isolates, 119 (58%) had a mutation in the P. falciparum dihydrofolate reductase (Pfdhfr) gene at codon 108, 6 (5%) had mutations in both Pfdhfr codon 108 and the P. falciparum dihydropteroate synthase codon 437, and 115 (56%) had the chloroquine resistance-associated K76T mutation in the P. falciparum chloroquine resistance transporter gene. This study represents a unique opportunity to improve surveillance of P. falciparum drug resistance in Comoros with consequences for treatment and chemoprophylaxis guidelines.     

Efficacy of mefloquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated Plasmodium falciparum infection in Machinga District, Malawi, 1998.

In response to the spread of chloroquine-resistant Plasmodium falciparum, Mala?i changed its first-line antimalarial drug in 1993 from chloroquine to sulfadoxine-pyrimethamine (SP). Surveillance data has suggested that resistance to SP may be increasing. We compared the efficacy of SP with a potential successor, mefloquine (MQ). By use of a modified World Health Organization in vivo protocol, children infected with P. falciparum were randomized to receive SP (sulfadoxine 25 mg/kg) or MQ (15 mg/kg). We observed combined RII and RIII parasitologic failures of 20.0 and 22.0% in the SP and MQ arms, respectively. Among those in the MQ arm, the relative hazard of failing with a Day 2 drug level < 500 ng/mL was 10.6 times higher than those with levels > or = 500 ng/mL. Given the decreased efficacy of the first-line antimalarial drug and the high failure rates of MQ at this lower dosage, Mala?i should consider assessing the efficacy and feasibility of alternative drugs to treat uncomplicated falciparum malaria.     

Artemisinin resistance or tolerance in human malaria patients

Malaria is a major cause of morbidity and mortality in the developing world. This situation is mainly due to emergence of resistance to most antimalarial drugs currently available. Artemisinin-based combination treatments are now first-line drugs for Plasmodium falciparum (P. falciparum) malaria. Artemisinin (qinghaosu) and its derivatives are the most rapid acting and efficacious antimalarial drugs. This review highlights most recent investigations into the emergence of artemisinin resistance in falciparum malaria patients on the Thai-Cambodian border, a historical epicenter for multidrug resistance spread spanning over 50 years. The study presents the first evidence that highlights the parasites reduced susceptibility to artemisinin treatment by prolonged parasite-clearance times, raising considerable concern on resistance development. Although the exact mechanism of action remains unresolved, development of resistance was proposed based from both in vitro experiments and human patients. Lines of evidence suggested that the parasites in the patients are in dormant forms, presumably tolerate to the drug pressure. The World Health Organization has launched for prevention and/or containment of the artemisinin-resistant malaria parasites. Taken together, the emergence of artemisinin resistance to the most potent antidote for falciparum malaria, poses a serious threat to global malaria control and prompts renewed efforts for urgent development of new antimalarial weapons.     

Plasmodium falciparum: correlation of in vivo resistance to chloroquine and antifolates with genetic polymorphisms in isolates from the south of Lao PDR

Levels of drug resistance of Plasmodium falciparum strains against antimalarials have increased in Laos. In several studies, chloroquine (CQ) resistance has been associated with point mutations in the Pfcrt and pfmdr genes, and sulphadoxine/pyrimethamine (S/P) resistance with point mutations in the genes of dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). We combined a study of these molecular markers with an in vivo antimalarial drug sensitivity study in Attapeu province in the south of Lao PDR. We treated 100 patients with either CQ, S/P or a combination of both. In the CQ group, Pfcrt mutations showed a very high sensitivity (100%) but a low specificity (12.5%) to predict resistance. The combination of mutations in the Pfcrt and pfmdr genes was highly specific and had a positive predictive value of 100%. Mutations in the DHPS gene showed a high correlation with the development of resistance. The prevalence of mutations in the DHFR gene, especially codon 108 Asn, was predictive with high sensitivity (100%) but low specificity. Isolates derived from patients treated with a combination of both drugs showed a high correlation between the mutation in codon 437 of DHPS gene and in vivo-resistance (odds ratio 16.00, CI). The study provides evidence for the existence of antimalarial drug resistance in the south of Lao PDR, and offers a molecular method to predict resistance.     

标准使用碳酸氢盐缓冲液进行恶性疟原虫培养和耐药性实验的研究

目的变化使用碳酸氢盐缓冲液以探讨药物对恶性疟原虫的不同效果. 方法用[3H]次黄嘌呤摄取法检测抗疟药物效果. 结果不同二氧化碳浓度引起的pH变化对氯喹抑制恶性疟原虫的效果差异显著,而乙胺嘧啶抑制恶性疟原虫的效果,受二氧化碳浓度的影响不大. 结论进行恶性疟原虫培养和耐药性实验时应根据二氧化碳的使用浓度而选择适当的碳酸氢钠浓度.     

Antimalarial drug sensitivity profile of western Kenya Plasmodium falciparum field isolates determined by a SYBR Green I in vitro assay and molecular analysis

In vitro drug sensitivity and molecular analyses of Plasmodium falciparum track drug resistance. DNA-binding fluorescent dyes like SYBR Green I may allow field laboratories, proximal to P. falciparum collection sites, to conduct drug assays. In 2007-2008, we assayed 121 P. falciparum field isolates from western Kenya for 50% inhibitory concentrations (IC(50)) against 6 antimalarial drugs using a SYBR Green I in vitro assay: 91 immediate ex vivo (IEV) and 30 culture-adapted, along with P. falciparum reference clones D6 (chloroquine [CQ] sensitive) and W2 (CQ resistant). We also assessed P. falciparum mdr1 (Pfmdr1) copy number and single nucleotide polymorphisms (SNPs) at four codons. The IC(50)s for IEV and culture-adapted P. falciparum isolates were similar, and approximated historical IC(50)s. For Pfmdr1, mean copy number was 1, with SNPs common at codons 86 and 184. The SYBR Green I assay adapted well to our field-based laboratory, for both IEV and culture-adapted P. falciparum, warranting continued use.