Establishment of the 1st World Health Organization International Standard for Plasmodium falciparum DNA for nucleic acid amplification technique (NAT)-based assays

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Abstract

Background

In order to harmonize results for the detection and quantification of Plasmodium falciparum DNA by nucleic acid amplification technique (NAT)-based assays, a World Health Organization (WHO) collaborative study was performed, evaluating a series of candidate standard preparations.

Methods

Fourteen laboratories from 10 different countries participated in the collaborative study. Four candidate preparations based upon blood samples parasitaemic for P. falciparum were evaluated in the study. Sample AA was lyophilized, whilst samples BB, CC and DD were liquid/frozen preparations. The candidate standards were tested by each laboratory at a range of dilutions in four independent assays, using both qualitative and quantitative NAT-based assays. The results were collated and analysed statistically.

Results

Twenty sets of data were returned from the participating laboratories and used to determine the mean P. falciparum DNA content for each sample. The mean log ₁₀"equivalents"/ml were 8.51 for sample AA, 8.45 for sample BB, 8.35 for sample CC, and 5.51 for sample DD. The freeze-dried preparation AA, was examined by accelerated thermal degradation studies and found to be highly stable.

Conclusion

On the basis of the collaborative study, the freeze-dried material, AA (NIBSC code No. 04/176) was established as the 1 ^stWHO International Standard for P. falciparum DNA NAT-based assays and has been assigned a potency of 10 ⁹International Units (IU) per ml. Each vial contains 5 × 10 ⁸IU, equivalent to 0.5 ml of material after reconstitution.

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Most cited references 26

Record: found
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Mefloquine resistance in Plasmodium falciparum and increased pfmdr1 gene copy number.

Ric Price, Anne-Catrin Uhlemann, Alan Brockman … (2004)

The borders of Thailand harbour the world's most multidrug resistant Plasmodium falciparum parasites. In 1984 mefloquine was introduced as treatment for uncomplicated falciparum malaria, but substantial resistance developed within 6 years. A combination of artesunate with mefloquine now cures more than 95% of acute infections. For both treatment regimens, the underlying mechanisms of resistance are not known. The relation between polymorphisms in the P falciparum multidrug resistant gene 1 (pfmdr1) and the in-vitro and in-vivo responses to mefloquine were assessed in 618 samples from patients with falciparum malaria studied prospectively over 12 years. pfmdr1 copy number was assessed by a robust real-time PCR assay. Single nucleotide polymorphisms of pfmdr1, P falciparum chloroquine resistance transporter gene (pfcrt) and P falciparum Ca2+ ATPase gene (pfATP6) were assessed by PCR-restriction fragment length polymorphism. Increased copy number of pfmdr1 was the most important determinant of in-vitro and in-vivo resistance to mefloquine, and also to reduced artesunate sensitivity in vitro. In a Cox regression model with control for known confounders, increased pfmdr1 copy number was associated with an attributable hazard ratio (AHR) for treatment failure of 6.3 (95% CI 2.9-13.8, p<0.001) after mefloquine monotherapy and 5.4 (2.0-14.6, p=0.001) after artesunate-mefloquine therapy. Single nucleotide polymorphisms in pfmdr1 were associated with increased mefloquine susceptibility in vitro, but not in vivo. Amplification in pfmdr1 is the main cause of resistance to mefloquine in falciparum malaria. Multidrug resistant P falciparum malaria is common in southeast Asia, but difficult to identify and treat. Genes that encode parasite transport proteins maybe involved in export of drugs and so cause resistance. In this study we show that increase in copy number of pfmdr1, a gene encoding a parasite transport protein, is the best overall predictor of treatment failure with mefloquine. Increase in pfmdr1 copy number predicts failure even after chemotherapy with the highly effective combination of mefloquine and 3 days' artesunate. Monitoring of pfmdr1 copy number will be useful in epidemiological surveys of drug resistance in P falciparum, and potentially for predicting treatment failure in individual patients.

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Record: found
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Article: not found

Detection of four Plasmodium species in blood from humans by 18S rRNA gene subunit-based and species-specific real-time PCR assays.

Mathieu Rougemont, Madeleine Van Saanen, Roland Sahli … (2004)

There have been reports of increasing numbers of cases of malaria among migrants and travelers. Although microscopic examination of blood smears remains the "gold standard" in diagnosis, this method suffers from insufficient sensitivity and requires considerable expertise. To improve diagnosis, a multiplex real-time PCR was developed. One set of generic primers targeting a highly conserved region of the 18S rRNA gene of the genus Plasmodium was designed; the primer set was polymorphic enough internally to design four species-specific probes for P. falciparum, P. vivax, P. malarie, and P. ovale. Real-time PCR with species-specific probes detected one plasmid copy of P. falciparum, P. vivax, P. malariae, and P. ovale specifically. The same sensitivity was achieved for all species with real-time PCR with the 18S screening probe. Ninety-seven blood samples were investigated. For 66 of them (60 patients), microscopy and real-time PCR results were compared and had a crude agreement of 86% for the detection of plasmodia. Discordant results were reevaluated with clinical, molecular, and sequencing data to resolve them. All nine discordances between 18S screening PCR and microscopy were resolved in favor of the molecular method, as were eight of nine discordances at the species level for the species-specific PCR among the 31 samples positive by both methods. The other 31 blood samples were tested to monitor the antimalaria treatment in seven patients. The number of parasites measured by real-time PCR fell rapidly for six out of seven patients in parallel to parasitemia determined microscopically. This suggests a role of quantitative PCR for the monitoring of patients receiving antimalaria therapy.

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Vertical transmission of HIV-1 infection.

M-L Newell (2015)

Vertical transmission is the dominant mode of acquisition of infection for HIV infection in children, and about 1600 infants are newly infected each day worldwide. Without interventions the risk of transmission is between 15% and 35%, and associated with maternal disease progression, prematurity, duration of rupture of membranes, length of labour, and vaginal delivery. Breastfeeding approximately doubles the risk of vertical transmission; the additional risk of transmission through breastfeeding is approximately 15-20%, with about one-third of this accounted for by late postnatal transmission after 3 months of age. Current strategies to reduce the risk of transmission include a short course of anti-retroviral therapy, avoidance of breastfeeding and Caesarean section delivery. However, even if interventions late in pregnancy or around the time of delivery are highly effective in preventing perinatal infection, it is likely that as a public health policy they are of interest only if alternatives to breastfeeding are feasible, affordable, safe and available.

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Author and article information

Journal

Journal ID (nlm-ta): Malar J

Title: Malaria Journal

Publisher: BioMed Central

ISSN (Electronic): 1475-2875

Publication date Collection: 2008

Publication date (Electronic): 24 July 2008

Volume: 7

Page: 139

Affiliations

[1 ]National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK

[2 ]Hospital for Tropical Disease, Mortimer Market, Off Tottenham Court Road, London, WC1E 6AU, UK

Article

Publisher ID: 1475-2875-7-139

DOI: 10.1186/1475-2875-7-139

PMC ID: 2518157

PubMed ID: 18652656

SO-VID: 06778a76-3451-4034-a42d-9a7e3eea3c3b

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.