Poor performance of malaria rapid diagnostic tests for the detection of Plasmodium malariae among returned international travellers in China.

BACKGROUND: Malaria is a worldwide infectious disease. For countries that have achieved malaria elimination, the prevention of re-establishment due to infections in returned travellers has become important. The accurate and timely diagnosis of malaria is the key in preventing re-establishment, and malaria rapid diagnostic tests (RDTs) are frequently used due to their convenience. However, the RDT performance in Plasmodium malariae (P. malariae) infection diagnosis remains unknown. METHODS: This study analysed epidemiological features and diagnosis patterns of imported P. malariae cases from 2013 to 2020 in Jiangsu Province and evaluated the sensitivity of four parasite enzyme lactate dehydrogenase (pLDH)-targeting RDTs (Wondfo, SD BIONLINE, CareStart and BioPerfectus) and one aldolase-targeting RDT(BinaxNOW) for P. malariae detection. Furthermore, influential factors were investigated, including parasitaemia load, pLDH concentration and target gene polymorphisms. RESULTS: The median duration from symptom onset to diagnosis among patients with P. malariae infection was 3 days, which was longer than that with Plasmodium falciparum (P. falciparum) infection. The RDTs had a low detection rate (39/69, 56.5%) among P. malariae cases. All tested RDT brands had poor performance in P. malariae detection. All the brands except the worst-performing SD BIOLINE, achieved 75% sensitivity only when the parasite density was higher than 5000 parasites/µL. Both pLDH and aldolase showed relatively conserved and low gene polymorphism rates. CONCLUSIONS: The diagnosis of imported P. malariae cases was delayed. The RDTs had poor performance in P. malariae diagnosis and may threaten the prevention of malaria re-establishment from returned travellers. The improved RDTs or nucleic acid tests for P. malariae cases are urgently needed for the detection of imported cases in the future.

Confirmation of the absence of local transmission and geographic assignment of imported falciparum malaria cases to China using microsatellite panel.

BACKGROUND: Current methods to classify local and imported malaria infections depend primarily on patient travel history, which can have limited accuracy. Genotyping has been investigated as a complementary approach to track the spread of malaria and identify the origin of imported infections. METHODS: An extended panel of 26 microsatellites (16 new microsatellites) for Plasmodium falciparum was evaluated in 602 imported infections from 26 sub-Saharan African countries to the Jiangsu Province of People's Republic of China. The potential of the 26 microsatellite markers to assign imported parasites to their geographic origin was assessed using a Bayesian method with Markov Chain Monte Carlo (MCMC) as implemented in the program Smoothed and Continuous Assignments (SCAT) with a modification to incorporate haploid genotype data. RESULTS: The newly designed microsatellites were polymorphic and are not in linkage disequilibrium with the existing microsatellites, supporting previous findings of high rate of recombination in sub-Saharan Africa. Consistent with epidemiology inferred from patients' travel history, no evidence for local transmission was found; nearly all genetically related infections were identified in people who travelled to the same country near the same time. The smoothing assignment method assigned imported cases to their likely geographic origin with an accuracy (Angola: 59%; Nigeria: 51%; Equatorial Guinea: 40%) higher than would be achieved at random, reaching statistical significance for Angola and Equatorial Guinea. CONCLUSIONS: Genotyping using an extended microsatellite panel is valuable for malaria case classification and programme evaluation in an elimination setting. A Bayesian method for assigning geographic origin of mammals based on genetic data was adapted for malaria and showed potential for identification of the origin of imported infections.

Classification of induced malaria case in an elimination setting: investigation of transfusion-transmitted malaria cases.

BACKGROUND: Since the National Malaria Elimination Action Plan was launched in China in 2010, local malaria transmission has decreased rapidly. Zero indigenous cases were reported since 2017. However, after 2010, the proportion of imported cases in China increased from 45.7% in 2010 to 99.9% in 2016, and almost all provinces of China have reported imported cases in recent years. Prevention of the reintroduction of malaria into China is crucial for the maintenance of its malaria-free status. Hence, it is of utmost importance to correctly identify the source of malaria infections within the country. CASE INTRODUCTION AND RESPONSE: In 2016 and 2017, three laboratory-confirmed cases of malaria caused by Plasmodium falciparum were identified in patients with no previous travel history to endemic areas were reported in Jiangsu Province, China, where malaria due to P. falciparum was eliminated about 30 years ago. These were diagnosed after 41, 31 and 39 days of seeking treatment, respectively, and all of them had received blood transfusions. Further investigations indicated that two of the cases had received blood from foreign students (from Indonesia and Ghana), and the other had received blood from an individual who had worked in Equatorial Guinea. All three blood donors were traced, and found to be carrying asymptomatic P. falciparum infections by microscopic examination and PCR. Furthermore, five polymorphic microsatellite markers (C1M4, C4M62, C13M13, C14M17, and C13M63) were typed and used to link parasites from the donors with those of the transfusion-receiving patients. CONCLUSIONS: Three transfusion-transmitted malaria cases were identified in China, all of which were due to the transfusion of blood donated by individuals who had contracted malaria outside the country. These cases can provide a reference for those faced with similar challenges in malaria case identification and classification in other regions. In addition, a stricter screening policy including the use of appropriate detection methods for malaria parasites should be developed and adopted for blood donation in regions undergoing malaria elimination.

ApoL1 Overexpression Drives Variant-Independent Cytotoxicity.

Coding variants in the APOL1 gene are associated with kidney diseases in African ancestral populations; yet, the underlying biologic mechanisms remain uncertain. Variant-dependent autophagic and cytotoxic cell death have been proposed as pathogenic pathways mediating kidney injury. To examine this possibility, we conditionally expressed APOL1-G0 (reference), -G1, and -G2 (variants) using a tetracycline-regulated system in HEK293 cells. Autophagy was monitored biochemically and cell death was measured using multiple assays. We measured intracellular Na+ and K+ content with atomic absorption spectroscopy and APOL1-dependent currents with whole-cell patch clamping. Neither reference nor variant APOL1s induced autophagy. At high expression levels, APOL1-G0, -G1, and -G2 inserted into the plasma membrane and formed pH-sensitive cation channels, causing collapse of cellular Na+ and K+ gradients, phosphorylation of p38 mitogen-activated protein kinase, and cell death, without variant-dependent differences. APOL1-G0 and -G2 exhibited similar channel properties in whole-cell patch clamp experiments. At low expression levels, neither reference nor variant APOL1s localized on the plasma membrane, Na+ and K+ gradients were maintained, and cells remained viable. Our results indicate that APOL1-mediated pore formation is critical for the trypanolytic activity of APOL1 and drives APOL1-mediated cytotoxicity in overexpression systems. The absence of cytotoxicity at physiologic expression levels suggests variant-dependent intracellular K+ loss and cytotoxicity does not drive kidney disease progression.

The challenge of maintaining microscopist capacity at basic levels for malaria elimination in Jiangsu Province, China.

BACKGROUND: Local malaria transmission has decreased rapidly since the National Malaria Elimination Action Plan was launched in China in 2010. However, imported malaria cases from Africa and Southeast Asia still occur in China due to overseas laborers. Diagnosis by microscopy is the gold standard for malaria and is used in most hospitals in China. However, the current capacity of microscopists to manage malaria cases in hospitals and public health facilities to meet the surveillance needs to eliminate and prevent the reintroduction of malaria is unknown. METHODS: Malaria diagnoses were assessed by comparing the percentage of first visit and confirmed malaria diagnoses at Centers for Disease Control and Prevention (CDCs) and hospitals. The basic personnel information for public health departments and hospitals at different levels was investigated. The skills of microscopists for blood smear preparation and slide interpretation were also examined at the county and township levels. RESULTS: Inaccurate rate with 13.49% and 7.32%, respectively, in 2013 and 2014, from 341 and 355 reported cases from sub-provincial levels in Jiangsu province. Most of the 523 malaria cases reported in Nantong Prefecture from 2000 to 2014 involved patients who first visited county CDCs seeking treatment, however, none of these cases received confirmed diagnosis of malaria in townships or villages.The staff at county CDCs and hospitals with a higher education background performed better at making and interpreting blood smears than staff from townships. CONCLUSIONS: The network for malaria elimination in an entire province has been well established. However, an insufficient capacity for malaria diagnosis was observed, especially the preparing and reading the blood smears at the township and village levels, which is a challenge to achieving and maintaining malaria elimination.

The increasing importance of Plasmodium ovale and Plasmodium malariae in a malaria elimination setting: an observational study of imported cases in Jiangsu Province, China, 2011-2014.

BACKGROUND: Following initiation of China's National Malaria Elimination Action Plan in 2010, indigenous malaria infections in Jiangsu Province decreased significantly. Meanwhile imported Plasmodium infections have increased substantially, particularly Plasmodium ovale and Plasmodium malariae. Given the risk for malaria resurgence, there is an urgent need to understand the increase in imported P. ovale and P. malariae infections as China works to achieve national malaria elimination. METHODS: An observational study of imported malaria cases in Jiangsu Province, China was carried out for the period of 2011-2014. RESULTS: A total of 1268 malaria cases were reported in Jiangsu Province from 2011 to 2014. Although imported Plasmodium falciparum cases (n = 1058) accounted for 83.4 % of all reported cases in Jiangsu, P. ovale cases (14, 19, 30, and 46) and their proportion (3.7, 9.6, 8.8, and 13.0 %) of all malaria cases increased over the 4 years. Similarly, P. malariae cases (seven, two, nine, and 10) and proportion (1.9, 1.0, 2.6, and 2.8 %) of all malaria cases increased slightly during this time. A total of 98 cases of Plasmodium ovale curtisi (47/98, 48 %) and Plasmodium ovale wallikeri (51/98, 52 %) were identified as well. Latency periods were significant among these Plasmodium infections (p = 0.00). Also, this study found that the latency periods of P. ovale sp., P. malariae and Plasmodium vivax were significantly longer than P. falciparum. However, for both P. ovale curtisi and P. ovale wallikeri infections, the latency period analysis was not significant (p = 0.81). Misdiagnosis of both P. ovale and P. malariae was greater than 71.5 and 71.4 %, respectively. The P. ovale cases were misdiagnosed as P. falciparum (35 cases, 32.1 %), P. vivax (43 cases, 39.4 %) by lower levels of CDCs or hospitals. And, the P. malariae cases were misdiagnosed as P. falciparum (ten cases, 35.7 %), P. vivax (nine cases, 32.1 %) and P. ovale sp. (one case, 3.6 %). Geographic distribution of imported P. ovale sp. and P. malariae cases in Jiangsu Province mainly originated from sub-Saharan Africa such as Equatorial Guinea, Nigeria, and Angola. CONCLUSIONS: Although the vast majority of imported malaria cases were due to P. falciparum, the increase in other rare Plasmodium species originating from sub-Saharan Africa and Southeast Asia should be closely monitored at all levels of health providers focusing on diagnosis and treatment of malaria. In addition to a receptive vector environment, long latency periods and misdiagnosis of P. malariae and P. ovale sp. increase the risk of re-introduction of malaria in China.

Disparate selection of mutations in the dihydrofolate reductase gene (dhfr) of Plasmodium ovale curtisi and P. o. wallikeri in Africa.

Plasmodium ovale curtisi and P. ovale wallikeri are both endemic in sub-Saharan Africa, the Middle East and Southeast Asia. Molecular surveillance data for drug resistance in P. ovale spp. is limited at present. We analysed polymorphisms in the podhfr, pocrt and pocytb genes of P. ovale spp. in 147 samples collected from travelers returning to China from Africa. Two podhfr mutations, S58R and S113N/T were detected in P. ovale curtisi with high/moderate frequencies of 52.17% and 17.39%, respectively. Evidence of positive selection (dN/dS = 2.41) was found for podhfr in P. ovale curtisi and decreased diversity (He) of microsatellite markers flanking the mutant alleles suggests that selective sweeps have occurred for both. Mutations E34G (1.50%) and L43V (1.50%) in pocrt of P. ovale curtisi, and E34G (3.70%), I102M (1.80%) and V111F (1.80%) of P. ovale wallikeri were found at low frequencies. Mutations R66K (6.20%), R75K (11.63%) and R95K (3.88%) of pocytb were found in both P. ovale curtisi and P. ovale wallikeri. These results suggest that the podhfr gene of P. ovale curtisi may be subject to drug selection in Africa, warranting further attention. We observed significant differences in the prevalence and distribution of podhfr mutations between the two P. ovale species, suggestive of fundamental biological differences between them.

Up-regulation of VEGF by MC3T3-E1 cells treated with curculigoside.

Empirical evidence has shown that curculigoside, the main active compound of the traditionally used Chinese herb, Curculigo orchioides (Amaryllidaceae, rhizome), affects bone formation and fracture healing. However, the mechanistic details of these processes remain unclear. Therefore, the effects of curculigoside on immortalized, pre-osteoblastic mouse MC3T3-E1 cells was investigated. Following treatment with curculigoside, MC3T3-E1 cells exhibited an increased rate of proliferation. Higher levels of vascular endothelial growth factor (VEGF), Fms-like tyrosine kinase-1 (Flt-1) and bone morphogenetic protein-2 (BMP-2) were also detected in cell supernatants and cell lysates by ELISA and western blot analysis, respectively. Furthermore, the stimulatory effect of curculigoside was observed at relatively low doses (i.e. 10-100 µg/mL). In combination, these responses to treatment with curculigoside elucidate mechanistic details underlying the therapeutic effects of Curculigo orchioides on bone, and identifies these molecules as potential targets for the treatment of common metabolic bone diseases.

Intravenous Dexmedetomidine Administration Prior Anesthesia Induction With Propofol at 4°C Attenuates Propofol Injection Pain: A Double-Blind, Randomized, Placebo-Controlled Trial.

Background: Propofol injection pain, despite various interventions, still occurs during the anesthesia induction and causes intense discomfort and anxiety in patients. This study aimed to explore the effect of intravenous dexmedetomidine on propofol injection pain prior to anesthesia induction with propofol at 4°C. Methods: A total of 251 patients (American Society of Anesthesiologists I-II) who underwent oral and maxillofacial surgery were randomly assigned to a combination group (n = 63), lidocaine group (n = 62), dexmedetomidine group (n = 63), and placebo-control group (n = 63); they received 0.5 ug/kg dexmedetomidine prior to anesthesia induction with propofol at 4°C, 40 mg lidocaine, 0.5 ug/kg dexmedetomidine prior to anesthesia induction, and normal saline, respectively. Incidence of pain, pain intensity, and reaction to the pain stimulus were evaluated by using verbal categorial scoring (VCS), a numerical rating scale (NRS), and the Surgical Pleth Index (SPI), respectively. In addition, hemodynamic parameters such as heart rate (HR) and mean arterial pressure (MAP) were also measured. The VCS and NRS were evaluated at 5 s after propofol injection. In addition, SPI, HR, and MAP were evaluated at three time points (before anesthesia induction and 5 and 30 s after propofol injection). Results: The incidence of pain in the combination group (51%) was significantly lower than that in the lidocaine group (71%), dexmedetomidine group (67%), or placebo-control group (94%) (p < 0.001). VCS and NRS scores in the combination group were also lower compared with the other three groups (p < 0.001), with no statistically significant differences between the lidocaine group and dexmedetomidine group (p > 0.05). The SPI of the combination group decreased significantly in comparison with the other three groups at 5 s after propofol injection (F = 96.23, p < 0.001) and 30 s after propofol injection (F = 4.46, p = 0.005). Further comparisons between HR and MAP revealed no significant differences across the groups (p > 0.05). Conclusion: Because of the sedative nature of dexmedetomidine and analgesic effect of low temperature, this study showed that intravenous dexmedetomidine prior to anesthesia induction with propofol at 4°C is highly effective in attenuating the incidence and severity of pain during injection compared with lidocaine (40 mg), dexmedetomidine 0.5 ug/kg) and placebo. This approach was not associated with any anesthesia complications. Clinical Trial Registration: ClinicalTrials.gov, identifier: ChiCTR-2000034663.

Cell-specific metabolism and pathogenesis of transmembrane prion protein.

The C-transmembrane form of prion protein ((Ctm)PrP) has been implicated in prion disease pathogenesis, but the factors underlying its biogenesis and cyotoxic potential remain unclear. Here we show that (Ctm)PrP interferes with cytokinesis in cell lines where it is transported to the plasma membrane. These cells fail to separate following cell division, assume a variety of shapes and sizes, and contain multiple nuclei, some of which are pyknotic. Furthermore, the synthesis and transport of (Ctm)PrP to the plasma membrane are modulated through a complex interaction between cis- and trans-acting factors and the endoplasmic reticulum translocation machinery. Thus, insertion of eight amino acids before or within the N region of the N signal peptide (N-SP) of PrP results in the exclusive synthesis of (Ctm)PrP regardless of the charge conferred to the N region. Subsequent processing and transport of (Ctm)PrP are modulated by specific amino acids in the N region of the N-SP and by the cell line of expression. Although the trigger for (Ctm)PrP upregulation in naturally occurring prion disorders remains elusive, these data highlight the underlying mechanisms of (Ctm)PrP biogenesis and neurotoxicity and reinforce the idea that (Ctm)PrP may serve as the proximate cause of neuronal death in certain prion disorders.

Pathogenic mutations in the glycosylphosphatidylinositol signal peptide of PrP modulate its topology in neuroblastoma cells.

Point mutations M232R (PrP(232R)), M232T (PrP(232T)), and P238S (PrP(238S)) in the glycosylphosphatidylinositol signal peptide (GPI-SP) of the prion protein (PrP(C)) segregate with familial Creutzfeldt-Jakob disease (CJD). However, the mechanism by which these mutations induce cytotoxicity is unclear since the GPI-SP is replaced by a GPI anchor within 5 min of PrP synthesis and translocation into the endoplasmic reticulum (ER). To examine if mutations in this region interfere with translocation of nascent PrP into the ER or anchor addition, the metabolism of PrP(232R) and PrP(232T) was investigated in transfected human neuroblastoma cells. In this report, we demonstrate that PrP mutations M232R and M232T do not interfere with GPI anchor addition. Instead, these mutations increase the stability and transport of GPI-SP mediated post-translationally translocated PrP to the plasma membrane, where it is linked to the lipid bilayer in a potentially neurotoxic C-transmembrane ((Ctm)PrP) orientation. Furthermore, we demonstrate that the GPI-SP of PrP functions as an efficient co-translational and inefficient post-translational ER translocation signal when tagged to an unrelated protein, underscoring the functional versatility of this peptide. These data uncover an alternate pathway of ER translocation for nascent PrP, and provide information on the possible mechanism(s) of neurotoxicity by mutations in the GPI-SP.

Assessment of false negative rates of lactate dehydrogenase-based malaria rapid diagnostic tests for Plasmodium ovale detection.

Currently, malaria rapid diagnostic tests (RDTs) are widely used for malaria diagnosis, but test performance and the factors that lead to failure of Plasmodium ovale detection are not well understood. In this study, three pLDH-based RDTs were evaluated using cases in China that originated in Africa. The sensitivity of Wondfo Pf/Pan, CareStart pLDH PAN and SD BIOLINE Pf/Pan in P. ovale detection was 70, 55 and 18%, respectively. CareStart was worse at detecting P. o. curtisi (36.5%) than at detecting P. o. wallikeri (75.0%), and SD could not detect P. o. curtisi. The overall detection ratio of all three RDTs decreased with parasite density and pLDH concentration. Wondfo, CareStart and SD detected only 75.0, 78.1 and 46.9% of the P. ovale cases, respectively, even when the parasitemia were higher than 5000 parasites/µL. Subspecies of P. ovale should be considered while to improve RDT quality for P. ovale diagnosis to achieve the goal of malaria elimination.

Mutant prion protein D202N associated with familial prion disease is retained in the endoplasmic reticulum and forms 'curly' intracellular aggregates.

Transmissible Spongiform Encephalopathies are fatal neurodegenerative disorders of humans and animals that are familial, sporadic, and infectious in nature. Familial disorders of humans include Gerstmann-Straussler-Scheinker disease (GSS), familial Creutzfeldt-Jakob disease (CJD), and fatal familial insomnia, and result from point mutations in the prion protein gene. Although neurotoxicity in familial cases is believed to result from a spontaneous change in conformation of mutant prion protein (PrP) to the pathogenic PrP-scrapie (PrPSc) form, emerging evidence indicates otherwise. We have investigated the processing and metabolism of mutant PrP D202N (PrP202N) in cell models to elucidate possible mechanisms of cytotoxicity. In this report, we demonstrate that PrP202N expressed in human neuroblastoma cells fails to achieve a mature conformation following synthesis and accumulates in the endoplasmic reticulum as 'curly' aggregates. In addition, PrP202N cells show increased sensitivity to free radicals, indicating that neuronal susceptibility to oxidative damage may account for the neurotoxicity observed in cases of GSS resulting from PrP D202N mutation.

[Study on the haplotypes of pfcrt polymorphism from Hainan Province].

OBJECTIVE: To develop a method for comparing the haplotypes of pfcrt polymorphism of Hainan Province with those from other areas of the world. METHODS: Nested PCR was used to amplify the polymorphic region including codon 72 to 76 and 97 of pfcrt gene. The PCR products were digested by ApoI restriction endonuclease to determine the allelic types. According to the allelic types, 6 products from each of mutant type and wild type were sequenced to analyze the haplotypes of pfcrt polymorphism. RESULTS: Bands in size of 195 bp appeared in all 19 samples. After ApoI digestion, 11 samples contained one ApoI site when codon 76 of the pfcrt gene codes for lysine (K76), which were visualized by the presence of 98 bp and 97 bp restriction fragments. The DNA sequencing revealed that 6 samples of chloroquine resistant P. falciparum carried pfcrt alleles encoding an amino acid haplotype of CVIET (residues 72-76), and the haplotype of CVMNK was found in other 6 samples with wild type pfcrt gene. CONCLUSION: Haplotypes of pfcrt polymorphism from Hainan were the same as those from southeast Asia and Africa.

Return of chloroquine sensitivity to Africa? Surveillance of African Plasmodium falciparum chloroquine resistance through malaria imported to China.

BACKGROUND: Chloroquine (CQ) was the cornerstone of anti-malarial treatment in Africa for almost 50 years, but has been widely withdrawn due to the emergence and spread of resistance. Recent reports have suggested that CQ-susceptibility may return following the cessation of CQ usage. Here, we monitor CQ sensitivity and determine the prevalence of genetic polymorphisms in the CQ resistance transporter gene (pfcrt) of Plasmodium falciparum isolates recently imported from Africa to China. METHODS: Blood samples were collected from falciparum malaria patients returning to China from various countries in Africa. Isolates were tested for their sensitivity to CQ using the SYBR Green I test ex vivo, and for a subset of samples, in vitro following culture adaptation. Mutations at positions 72-76 and codon 220 of the pfcrt gene were analyzed by sequencing and confirmed by PCR-RFLP. Correlations between drug sensitivity and pfcrt polymorphisms were investigated. RESULTS: Of 32 culture adapted isolates assayed, 17 (53.1%), 6 (18.8%) and 9 (28.1%) were classified as sensitive, moderately resistant, and highly resistant, respectively. In vitro CQ susceptibility was related to point mutations in the pfcrt gene, the results indicating a strong association between pfcrt genotype and drug sensitivity. A total of 292 isolates were typed at the pfcrt locus, and the prevalence of the wild type (CQ sensitive) haplotype CVMNK in isolates from East, South, North, West and Central Africa were 91.4%, 80.0%, 73.3%, 53.3% and 51.7%, respectively. The only mutant haplotype observed was CVIET, and this was almost always linked to an additional mutation at A220S. CONCLUSIONS: Our results suggest that a reduction in drug pressure following withdrawal of CQ as a first-line drug may lead to a resurgence in CQ sensitive parasites. The prevalence of wild-type pfcrt CQ sensitive parasites from East, South and North Africa was higher than from the West and Central areas, but this varied greatly between countries. Further surveillance is required to assess whether the prevalence of CQ resistant parasites will continue to decrease in the absence of widespread CQ usage.

Production of Plasmodium vivax enolase in Escherichia coli and its protective properties.

Plasmodium vivax predominates in South-East Asia and the American continent, causes significant morbidity and inflicts a huge socioeconomic burden. Sequencing completion of the Plasmodium vivax genome and transcriptome provides the chance to identify antigens. Enolase is the eighth enzyme in the glycolytic pathway, which, apart from its glycolytic function, also possess antigenic properties and is present on the cell wall of many invasive organisms, such as Candida albicans. In order to assess whether enolase of Plasmodium vivax is also antigenic, in this study, we first reported the expression and purification of recombinant Plasmodium vivax enolase (r-Pven) in Escherichia coli, using prokaryotic expression vector. The r-Pven was expressed in soluble form in E. coli, and the expression was verified by SDS-PAGE and western blotting analysis. The r-Pven was purified to 90% purity by nickel-nitrilotriacetic acid (Ni2+-NTA) resin chromatography. For reactivity with r-Pven, compared with the average values of the reactivity of control serum samples, the average values of the reactivity of 99 individual serums from vivax malaria patients appeared higher, and there was significant difference between them (p=0.0117<0.05). Mice anti-r-Pven antibodies inhibited the growth of in vitro cultures of P. falciparum. Mice immunized with r-Pven showed protection against a challenge with the mouse malarial parasite Plasmodium berghei. The antibodies raised against r-Pven were specific for Plasmodium and did not react to the host tissues. These observations established Plasmodium vivax enolase to be a potential protective antigen.

Protease-resistant human prion protein and ferritin are cotransported across Caco-2 epithelial cells: implications for species barrier in prion uptake from the intestine.

Foodborne transmission of bovine spongiform encephalopathy (BSE) to humans as variant Creutzfeldt-Jakob disease (CJD) has affected over 100 individuals, and probably millions of others have been exposed to BSE-contaminated food substances. Despite these obvious public health concerns, surprisingly little is known about the mechanism by which PrP-scrapie (PrP(Sc)), the most reliable surrogate marker of infection in BSE-contaminated food, crosses the human intestinal epithelial cell barrier. Here we show that digestive enzyme (DE) treatment of sporadic CJD brain homogenate generates a C-terminal fragment similar to the proteinase K-resistant PrP(Sc) core of 27-30 kDa implicated in prion disease transmission and pathogenesis. Notably, DE treatment results in a PrP(Sc)-protein complex that is avidly transcytosed in vesicular structures across an in vitro model of the human intestinal epithelial cell barrier, regardless of the amount of endogenous PrP(C) expression. Unexpectedly, PrP(Sc) is cotransported with ferritin, a prominent component of the DE-treated PrP(Sc)-protein complex. The transport of PrP(Sc)-ferritin is sensitive to low temperature, brefeldin-A, and nocodazole treatment and is inhibited by excess free ferritin, implicating a receptor- or transporter-mediated pathway. Because ferritin shares considerable homology across species, these data suggest that PrP(Sc)-associated proteins, in particular ferritin, may facilitate PrP(Sc) uptake in the intestine from distant species, leading to a carrier state in humans.

[Epidemiological analysis of malaria prevalence in Jiangsu Province in 2014].

OBJECTIVE: To understand the malaria epidemic situation and characteristics in Jiangsu Province in 2014, so as to provide the evidence for formulating and adjusting appropriate strategies and measures for malaria elimination in this province. METHODS: The reported malaria cases from the Internet Reporting System and the epidemiological data of malaria in Jiangsu Province were collected and analyzed. RESULTS: A total of 355 malaria cases were reported in Jiangsu Province in 2014, which was increased by 4.11% comparing to that in 2013 (341 cases), and the malaria incidence was 0.046/10 000. All the 355 cases were imported from other countries, among which, 4 cases (1.13%) were from Southeast Asia; the other 351 cases (98.87%) were from 21 African countries. Though the cases were distributed in all the 13 prefecture-level cities in Jiangsu Province, the number of cases in 5 of them namely Huai' an, Nantong, Lianyungang, Yangzhou and Taizhou accounted for 63.38% (225/ 355). A total of 292 falciparum malaria cases, 4 tertian malaria cases, 10 quartan malaria cases, 46 ovale malaria cases and 3 mixed infection cases were confirmed after re-checked by Jiangsu Provincial Reference Lab of Malaria. The follow-up observation of the cases showed that among the 355 cases, 6 falciparum malaria cases recrudesced, and 4 ovale malaria cases and 1 tertian malaria case recurred. CONCLUSIONS: There have been no local malaria cases reported from Jiangsu Province in the last three years, indicating the object of malaria elimination has been achieved initiatively. However, there are still many imported malaria cases from other countries, with a diverse species of plasmodium. Therefore, the surveillance of the imported malaria, the training for diagnosis and treatment of malaria as well as the health education to the key population should be strengthened.

Prion peptide 106-126 as a model for prion replication and neurotoxicity.

Prion diseases or transmissible spongiform encephalopathies are neurodegenerative disorders that are genetic, sporadic, or infectious. The pathogenetic event common to all prion disorders is a change in conformation of the cellular prion protein (PrPC) to the scrapie isoform (PrPSc), which, unlike PrPC, aggregates easily and is partially resistant to protease digestion. Although PrPSc is believed to be essential for the pathogenesis and transmission of prion disorders, the mechanism by which PrPSc deposits cause neurodegeneration is unclear. It has been proposed that in some cases of prion disorders, a transmembrane form of PrP, termed CtmPrP may be the mediator of neurodegenerative changes rather than PrPSc per se. In order to understand the underlying cellular processes by which PrPSc mediates neurodegeneration, we have investigated the mechanism of neurotoxicity by a beta-sheet rich peptide of PrP in a cell model. We show that exposure of human neuronal cell lines NT-2 and M17 to the prion peptide 106-126 (PrP106-126) catalyzes the aggregation of endogenous cellular prion protein (PrPC) to an amyloidogenic form that shares several characteristics with PrPSc. Intracellular accumulation of these PrPSc-like forms upregulates the synthesis of CtmPrP, which is proteolytically cleaved in the endoplasmic reticulum and the truncated C-terminal fragment is transported to the cell surface. In addition, we have isolated mutant NT-2 and neuroblastoma cells that are resistant to toxicity by PrP106-126 to facilitate further characterization of the biochemical pathways of PrP106-126 neurotoxicity. The PrP106-126-resistant phenotype of these cells could result from aberrant binding or internalization of the peptide, or due to an abnormality in the downstream pathway(s) of neuronal toxicity. Thus, our data suggest that PrPSc aggregation occurs by a process of 'nucleation' on a pre-existing 'seed' of PrP. Furthermore, the PrP106-126-resistant cells reported here will provide a unique opportunity for identifying the cellular and biochemical pathways that mediate neurotoxicity by PrPSc.