Plasmodium malariae infection boosts Plasmodium falciparum gametocyte production

We analyzed records of malaria therapy patients sequentially or simultaneously inoculated with Plasmodium falciparum and Plasmodium malariae. Gametocyte production was enhanced in P. falciparum by prior or concurrent P. malariae infection but diminished or unaffected in P. malariae by P. falciparum. Conversely, asexual-form production was diminished in P. malariae but unaffected in P. falciparum.     

三日疟与恶性疟混合感染一例报告

患者．男性，36岁，四川省射洪县人。2004年11月中旬到云南，在瑞丽中缅两国边境接壤的秀岛镇做运输木材工作。弄岛三面被缅甸环绕，距瑞丽市28km。患者从边境多次往返于缅甸境内运木材．每次停留约1周。于2005年3月底返乡后有过感冒样前驱症状：表现为周身不适、头晕、乏力、腰酸背痛、食欲不振伴有轻微呕吐，并于4月5日起反复发热，4月9日后表现为不规则发热并日渐加重．体温最高达40．4℃，伴有寒战、呕吐、头痛、咳嗽。     

Transmission of mixed Plasmodium species and Plasmodium falciparum genotypes

We studied malaria transmission by comparing parasite populations in humans and mosquito vectors at the household level. Blood samples were collected from all inhabitants for microscopic detection of gametocytes and polymerase chain reaction analysis. The next morning, blood-fed resting mosquitoes were collected inside the bed nets used by the individuals surveyed the previous afternoon. After 8 days of maintenance, mosquitoes were dissected, and midguts and salivary glands were recovered for polymerase chain reaction analysis. Results showed that parasite distribution was the same in the 2 hosts when compared at each household but was different when whole populations were analyzed. Different associations of Plasmodium species seem to occur in humans (Plasmodium falciparum/Plasmodium malariae) and mosquitoes (P. falciparum/Plasmodium ovale). Regarding P. falciparum infections, a higher proportion of single-genotype infections and less allele diversity are observed in mosquitoes than in humans.     

多重PCR快速检测恶性疟和间日疟的研究

目的 建立一种简便快速、能同时检测恶性疟和间日疟的核酸检测方法。方法 针对两种疟原虫18S rRNA基因设计2对(3条引物),优化引物浓度与退火温度,建立可扩增出两种疟原虫基因片段的多重PCR。并进行最低检测限确定和临床标本检测,以镜检法为金标准分析灵敏度和特异度等指标。结果 该方法可扩增出431 bp(恶性疟原虫)和341 bp(间日疟原虫)基因片段,最低检测限为10²copies/反应,检测临床标本的结果与镜检法无差别(P＞0.05),敏感度为93.55%,特异度为70.83%,阳性预测值为89.23%,阴性预测值为80.95%。结论 所建立的多重PCR方法可快速检测疟疾感染并鉴别分型,灵敏度高,值得推广。     

Immunization of mice with Plasmodium TCTP delays establishment of Plasmodium infection

Translationally controlled tumour protein (TCTP) may play an important role in the establishment or maintenance of parasitemia in a malarial infection. In this study, the potential of TCTP as a malaria vaccine was investigated in two trials. In the initial vaccine trial, Plasmodium falciparum TCTP (PfTCTP) was expressed in Saccharomyces cerevisiae and used to immunize BALB/c mice. Following challenge with Plasmodium yoelii YM, parasitemia was significantly reduced during the early stages of infection. In the second vaccine trial, the TCTP from P. yoelii and P. berghei was expressed in Escherichia coli and used in several mouse malaria models. A significant reduction in parasitemia in the early stages of infection was observed in BALB/c mice challenged with P. yoelii YM. A significantly reduced parasitemia at each day leading up to a delayed and reduced peak parasitemia was also observed in BALB/c mice challenged with the nonlethal Plasmodium chabaudi (P.c.) chabaudi AS. These results suggest that TCTP has an important role for parasite establishment and may be important for pathogenesis.     

标签引物-套式/多重PCR检测恶性疟原虫和间日疟原虫的研究

目的 建立简便、灵敏、低本底、可同时检测恶性疟原虫和间日疟原虫的套式/多重聚合酶链反应（PCR）系统。 方法 应用标签引物扩增技术、Primer Premier 5.0软件、美国生物信息中心(NCBI-BLAST)网络资源和矩阵试验法优化套式/多重PCR，检测疟疾患者滤纸血样并与镜检结果进行比较。 结果 新建立的标签引物套式/多重PCR，检测模拟现场滤纸血样的敏感性为恶性疟原虫1～2个虫/μl血，间日疟原虫5～10个虫/μl血。检测71份现场采集的镜检疟原虫阳性滤纸血样（恶性疟24份和间日疟47份）的结果与镜检结果的符合率分别为87.5%和100%。 结论 通过标签引物扩增技术优化的套式/多重PCR系统，适用于检测现场采集的滤纸血样，其检出低原虫血症的敏感性和鉴定虫种的准确性均优于镜检法，是很有潜力的疟疾诊断技术。     

复式PCR检测间日疟原虫和恶性疟原虫的现场应用

目的探讨复式PCR方法在疟疾诊断中的现场应用价值。方法根据疟原虫18 S rRNA基因序列,合成疟原虫属特异性上游引物和间日疟原虫、恶性疟原虫种特异性下游引物,优化PCR反应体系,建立在同一PCR反应体系中同时检测间日疟原虫、恶性疟原虫基因组特异性DNA片段的疟疾诊断方法,并评价其现场应用价值。结果间日疟原虫和恶性疟原虫基因组DNA经过复式PCR后,分别扩增出1 451 bp和833 bp的特异性条带,而伯氏疟原虫、食蟹猴疟原虫及健康人血样均无扩增带出现,用该反应体系可检出原虫血症为1.1×10-6和5.6×10-7的间日疟原虫和恶性疟原虫感染。与镜检法相比,复式PCR检测119份现场样本,112份与镜检结果相同,阳性率为54%,漏诊率为0.8%,误诊率为0,而镜检法依次分别为53%、1.7%和3.4%。结论复式PCR方法检测疟原虫具有简便、快速、特异、敏感等优点,在疑似病例的鉴别诊断和分子流行病学调查中具有良好的应用价值。     

Plasmodium vivax: recent world expansion and genetic identity to Plasmodium simium

Plasmodium vivax causes the most geographically widespread human malaria, accounting annually for 70-80 million clinical cases throughout the tropical and subtropical regions of the world's continents. We have analyzed the DNA sequences of the Csp (circumsporozoite protein) gene in 24 geographically representative strains of P. vivax and 2 of P. simium, which parasitizes several species of New World monkeys. The Csp sequences are of two types, VK210 and VK247, which differ by three diagnostic amino acid replacements, one in each of the 5' and 3' terminal regions [5' nonrepeat (NR) and 3' NR] of the gene and in an insertion sequence that precedes the 3' NR region. The central region of the gene consists of approximately 38 repetitive "motifs," which are alternatively four and five amino acids long, which also are diagnostically different between the VK210 and VK247 types. There are very few synonymous substitutions within and between the two types of strains, which we hypothesize reflects that the worldwide spread of P. vivax is very recent. The two P. simium Csp sequences belong one to each of the two VK types and are genetically indistinguishable from the corresponding P. vivax strains, suggesting that at least two host transfers have occurred between humans and New World monkeys. We exclude as unlikely the possibility that the two types of sequences could have independently arisen in humans and platyrrhines by natural selection. There are reasons favoring each of the two possible directions of host transfer between humans and monkeys.     

Hypnozoites of Plasmodium simiovale

Hypnozoites of Plasmodium simiovale were detected in liver biopsies from a rhesus monkey (Macaca mulatta) inoculated eight days previously with sporozoites from heavily infected anopheline mosquitoes. The tissue forms, 6 mu in diameter, were found within the cytoplasm of hepatic parenchymal cells by immunofluorescence and restained with Giemsa. This is the first report of latent, pre-erythrocytic stages from an ovale-type relapsing malaria.     

Plasmodium vivax and Plasmodium falciparum gametocyte stages are neglected in vaccine development

Plasmodium gametocytes are responsible for transmission from the vertebrate host to the mosquito. Plasmodium gametocytes undergo a complex cycle from asexual stages, through a poorly understood process characterized by expression of stage-specific proteins and adhesion molecules. Gametocytes are capable of inducing specific humoral IgG, and cellular responses, which include induction of TNFalpha, IFNgamma and gammadelta+ lymphocyte proliferation, in addition to immune responses to other stages of the parasite (sporozoite, exo-erythrocytic stages, erythrocytic stages). Although transmission-blocking vaccines against Plasmodium do not currently include components against the gametocytes (rather they focus on gametes, zygotes or ookinetes, stages which occur in the mosquito), further understanding of the mechanisms underlying gametocytogenesis and immune responses against these stages may provide additional strategies for more effective transmission inhibition.