Sequence variation of PfEMP1-DBLα in association with rosette formation in Plasmodium falciparum isolates causing severe and uncomplicated malaria

<p>Abstract</p> <p>Background</p> <p>Rosetting and cytoadherence of <it>Plasmodium falciparum-</it>infected red blood cells have been associated with severity of malaria. ICAM-1 and CD36 are the main host cell receptors, while PfEMP1-DBLα is a major parasite ligand, which can contribute to rosette formation. This study is aimed at demonstrating whether the highly polymorphic PfEMP1-DBLα sequences occurring among Thai isolates causing severe and uncomplicated malaria are associated with their ability to form rosettes and reflected the clinical outcome of the patients.</p> <p>Methods</p> <p>Two hundred and ninety five PfEMP1-DBLα sequences from Thai clinical isolates causing severe and uncomplicated malaria were evaluated by sequencing and direct comparison using the specific text string analysis functions in Microsoft Excel and Perl. The relationships between the PfEMP1-DBLα sequences were also analysed by network analysis. The binding abilities of parasitized red blood cells (PRBCs) to CD36, wild type ICAM-1, ICAM-1^Kilifiand ICAM-1^S22/Aunder static condition were included.</p> <p>Results</p> <p>Two hundred and eighty one non-identical amino acid sequences were identified (< 95% sequence identity). When the distributions of semi-conserved features (PoLV1–4 and sequence group) within the rosetting domain PfEMP1-DBLα were observed, close similarity was found between isolates from the two disease groups. The sequence group 1 representing uncomplicated malaria was significantly different from the sequence group 3 representing the majority of severe malaria (<it>p </it>= 0.027). By using a simple non-phylogenetic approach to visualize the sharing of polymorphic blocks (position specific polymorphic block, PSPB) and cys/PoLV among DBLα sequences, the sequence group 1 was split from the other five sequence groups. The isolates belonging to sequence group 5 gave the highest mean rosetting rate (21.31%). However, within sequence group 2 and group 6, the isolates causing severe malaria had significantly higher rosetting rate than those causing uncomplicated malaria (<it>p </it>= 0.014, <it>p </it>= 0.007, respectively).</p> <p>Conclusion</p> <p>This is the first report of PfEMP1-DBLα analysis in clinical Thai isolates using semi-conserved features (cys/PoLV and PSPBs). The cys/PoLV group 5 gave the highest rosetting rate. PfEMP1-DBLα domains in Thai isolates are highly diverse, however, clinical isolates from severe and uncomplicated malaria shared common sequences.</p

Evaluation of the anti-malarial activity and cytotoxicity of 2,4-diamino-pyrimidine-based kinase inhibitors

A series of 2,4 diamino-pyrimidines have been identified from an analysis of open access high throughput anti-malarial screening data reported by GlaxoSmithKline at the 3D7 and resistant Dd2 strains. SAR expansion has been performed using structural knowledge of the most plausible parasite target. Seventeen new analogs have been synthesized and tested against the resistant K1 strain of Plasmodium falciparum (Pf). The cytotoxicity of the compounds was assessed in Vero and A549 cells and their selectivity towards human kinases including JAK2 and EGFR were undertaken. We identified compound 5n and 5m as sub-micromolar inhibitors, with equivalent anti-malarial activity to Chloroquine (CQ). Compounds 5d and 5k, mM inhibitors of Pf, displayed improved cytotoxicity with weak inhibition of the human kinases

Acquisition of naturally acquired antibody response to Plasmodium falciparum erythrocyte membrane protein 1-DBLα and differential regulation of IgG subclasses in severe and uncomplicated malaria

Objectives: To explore whether individuals infected with Plasmodium falciparum (P. falciparum) develop antibodies directed against PfEMP1-DBLα, and to assess their IgG subclass distribution in severe and uncomplicated malaria. Methods: The anti-PfDBLα IgG and their IgG subclass distributions in plasma of severe (SM) and uncomplicated malaria (UCM) were assessed by enzyme-linked immunoabsorbent assay. The antibody profiles to P. falciparum blood stage antigens were evaluated. CD36 binding ability was determined by static receptor-binding assays. Rosette formation was performed by staining with acridine orange. Results: Significantly higher number of UCM (86.48%) than SM (57.78%) plasma contained total acquisition of specific IgG to P. falciparum antigens (P = 0.000). Similar manners were seen in response to P. falciparum DBLα with significant difference (UCM, 59.46% vs SM, 40.00%; P = 0.014). Anti-PfDBLα-IgG1 and -IgG3 were the predominant subclasses. Similar percentage of UCM (31.82%) and SM (33.33%) plasma contained only IgG1, while 13.64% of UCM and 27.78% of SM plasma contained only IgG3. Anti-PfDBLα-IgG1 coexpressed with more than one subclass was noted (UCM, 27.27%; SM, 16.67%). Obviously, IgG1 coexpressed with IgG3 (9.09%) was observed in only UCM plasma. IgG1 was coexpressed with IgG2 in UCM (9.09%) and SM (11.11%) plasma, while IgG1 was coexpressed with IgG4 only in UCM plasma (4.55%). IgG subclasses to P. falciparum antigens were distributed in a similar manner. Only the levels of IgG1, but not IgG3 were significantly higher in UCM than in SM. Conclusions: These data suggest that individuals infected with P. falciparum can develop the anti-PfEMP1 antibodies with the major contribution of specific IgG subclasses. The balance and the levels of anti-PfDBLα IgG subclasses play a crucial role in antibody mediated protection against severe malaria. Keywords: Plasmodium falciparum, PfEMP1-DBLα, Antibody, Severe malaria, Uncomplicated malari

Exploring Potential Antimalarial Candidate from Medicinal Plants of Kheaw Hom Remedy

The Kheaw Hom remedy is a traditional Thai medicine widely used to treat fevers. Some plant ingredients in this remedy have been investigated for their antimicrobial, antiviral, anti-inflammatory, and antioxidant activities. However, there have been no reports on the antimalarial activities of the medicinal plants in this remedy. Therefore, this study focuses on identifying potential antimalarial drug candidates from the medicinal plant ingredients of the Kheaw Hom remedy. Eighteen plants from the Kheaw Hom remedy were extracted using distilled water and ethanol. All extracts were investigated for their in vitro antimalarial activity and cytotoxicity. An extract that exhibited good in vitro antimalarial activity and low toxicity was selected for further investigation by using Peter&rsquo;s 4-day suppressive test and an acute oral toxicity evaluation in mice. Based on the in vitro antimalarial activity and cytotoxicity studies, the ethanolic extract of Globba malaccensis rhizomes showed promising antimalarial activity against the Plasmodium falciparum K1 strain (IC50 = 1.50 &micro;g/mL) with less toxicity to Vero cells (CC50 of &gt;80 &micro;g/mL). This extract exhibited a significant dose-dependent reduction in parasitemia in P. berghei-infected mice. The maximum suppressive effect of this extract (60.53%) was observed at the highest dose administered (600 mg/kg). In a single-dose acute toxicity test, the animals treated at 2000 mg/kg died within 48 h after extract administration. In conclusion, our study indicates that the ethanolic extract of G. malaccensis rhizomes exhibited in vitro and in vivo antimalarial activities, which could serve as a promising starting point for antimalarial drug

ผลของสารสกัดหยาบด้วยเอทานอลจากสมุนไพร 7 ชนิดต่อการไล่มด

วารสารวิชาการและวิจัย มทร.พระนคร, ปีที่ 16, ฉบับที่ 2 (ก.ค.-ธ.ค. 2565), หน้า 187-197This research aims to study the ant repellent effects of the crude ethanolic extracts from 7 herbs; Piper nigrum Linn., Alpinia galanga (L.) Willd, Ocimum basilicum L., Cymbopogon citratus Stapf, Citrus aurantiifolia (Christm.) Swingle, Citrus hystrix DC, and Stemona collinsae Craib. Whatman filter paper was dipped with each concentration of the crude ethanolic extracts (0.625 1.25 2.5 and 5 % w/v) and placing the bait on a treated filter paper. The experiments were conducted in the natural. The numbers of weaver ants were recorded at 0 - 30 minutes. From the results, the crude ethanolic extracts at 5% w/v of A. galanga was the most effective for repellent the ant, (repellent rate; %R = 94.72 ± 2.39) followed with C. citratus (%R = 89.45 ± 3.85), S. collinsae (%R = 82.92 ± 4.47), and P.nigrum (%R = 81.20 ± 5.92). The repellent rates of those crude ethanolic extracts were significantly difference from distilled water which use for the negative control (P < 0.05). The crude ethanolic extract of A. galanga at concentration 5% w/v was prepared as spray, cream, chalk and powder. At 30 minutes of the observation, the ethanolic extracts of A. galanga spray was the best ant repellent effect (%R = 100). The result from questionnaires reveals that a spray preparation was the more satisfaction for the using ant repellent products.Rajamangala University of Technology Phra Nakho