BACKGROUND Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. METHODS Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. RESULTS The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand–Cambodia border. Slowly clearing in fections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the “propeller” region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. CONCLUSIONS Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.)

Tobacco plants with reduced amounts and activities of both the chloroplast cytochrome b6/f and ATP synthase complexes have been produced using antisense RNA techniques. Antisense constructs were generated from tobacco cDNA clones coding for the Rieske FeS protein and the δ subunit of the b6/f and ATP synthase complexes respectively. Transformants with altered activities were selected using pulse-modulated fluorescence measurements. The b6/ftransformants showed high levels of steady-state fluorescence and reduced levels of both photochemical and non-photochemical quenching. In striking contrast, the ATP synthase transformants showed low levels of steady-state fluorescence and greatly increased levels of non-photochemical quenching. Transformants with a range of suppression were isolated for both constructs, in some cases with photosynthesis reduced to less than 10% of wild-type values. The most severely affected transformants showed extremely slow growth and in some cases they were unable to grow and produce seed. Progeny from the R1 seed from several cytochrome b6/f transformants have been analysed and show segregation of phenotypes ranging from intermediate to severe in repression. Intermediate and severe phenotype plants showed a reduction in Rieske FeS mRNA of more than 90% while FeS polypeptide was reduced to 60 and 86% of wild type. There was a strong correlation between photosynthesis at air and Rieske FeS polypeptide content in the antisense plants suggesting that the cytochrome b6/f complex was a major determinant of photosynthetic rate under these conditions. Photoinhibition studies of FeS antisense plants showed that there was a reduced activity of the xanthophyll cycle in the most severe plants, consistent with a reduction in the transthylakoid pH gradient and a lowered non-photochemical quenching. Preliminary studies of the ATPδ antisense plants showed that they also had reduced levels of mRNA and ATPδ polypeptide.

Nine of 30 mammary cancer patients developed metastases during 13-94 months after mastectomy. All 9 patients had elevated blood levels of pregnancy-associated alpha-macroglobulin (PAM) 1-21 months before conventional detection of metastases. Seven of the clinically well patients had PAM rises exceeding 90 per cent above the baseline and in 4 of these the PAM later fell to lower levels. PAM appears to have potential as an indicator of the growth of micrometastases.

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