Artemisia annua and artemisinins are ineffective against human Babesia microti and six Candida sp.

BACKGROUND: Artemisia annua L.is a well-established medicinal herb used for millennia to treat parasites and fever-related ailments caused by various microbes. Although effective against many infectious agents, the plant is not a miracle cure and there are infections where it has proved ineffective or limited. It is important to report those failures. METHODS: Here artemisinin, artesunate and dried leaf slurries of A. annua were used daily for 6 days in vivo against Babesia microti in mice 2 days post infection at 100 µg artemisinin/kg body weight. Parasitemia was measure before and 15 days days post treatment. Artemisinin and extracts of A. annua also were tested in vitro against six Candida sp. at artemisinin concentrations up to 180 µM and growth measured after cultures were fed drugs once at different stages of growth and also after repeated dosing. RESULTS: A. annua, artesunate, and artemisinin were ineffective in reducing or eliminating parasitemia in B. microti-infected mice treated at 100 µg artemisinin/kg body weight. Although the growth of exponential cultures of many of the tested Candida sp. was inhibited, the response was not sustained and both artemisinin and Artemisia were essentially ineffective at concentrations of artemisinin at up to 180 µM of artemisinin. CONCLUSIONS: Together these results show that artemisinin, its derivatives, and A. annua are ineffective against B. microti and at least six species of Candida.

Drug Screening for Discovery of Broad-spectrum Agents for Soil-transmitted Nematodes.

Soil-transmitted nematodes (STNs), namely hookworms, whipworms, and ascarids, are extremely common parasites, infecting 1-2 billion of the poorest people worldwide. Two benzimidazoles, albendazole and mebendazole, are currently used in STN mass drug administration, with many instances of low/reduced activity reported. New drugs against STNs are urgently needed. We tested various models for STN drug screening with the aim of identifying the most effective tactics for the discovery of potent, safe and broad-spectrum agents. We screened a 1280-compound library of approved drugs to completion against late larval/adult stages and egg/larval stages of both the human hookworm parasite Ancylostoma ceylanicum and the free-living nematode Caenorhabditis elegans, which is often used as a surrogate for STNs in screens. The quality of positives was further evaluated based on cheminformatics/data mining analyses and activity against evolutionarily distant Trichuris muris whipworm adults. From these data, two pairs of positives, sulconazole/econazole and pararosaniline/cetylpyridinium, predicted to target nematode CYP-450 and HSP-90 respectively, were prioritized for in vivo evaluation against A. ceylanicum infections in hamsters. One of these positives, pararosaniline, showed a significant impact on hookworm fecundity in vivo. Taken together, our results suggest that anthelmintic screening with A. ceylanicum larval stages is superior to C. elegans based on both reduced false negative rate and superior overall quality of actives. Our results also highlight two potentially important targets for the discovery of broad-spectrum human STN drugs.

Identification of small molecule enzyme inhibitors as broad-spectrum anthelmintics.

Targeting chokepoint enzymes in metabolic pathways has led to new drugs for cancers, autoimmune disorders and infectious diseases. This is also a cornerstone approach for discovery and development of anthelmintics against nematode and flatworm parasites. Here, we performed omics-driven knowledge-based identification of chokepoint enzymes as anthelmintic targets. We prioritized 10 of 186 phylogenetically conserved chokepoint enzymes and undertook a target class repurposing approach to test and identify new small molecules with broad spectrum anthelmintic activity. First, we identified and tested 94 commercially available compounds using an in vitro phenotypic assay, and discovered 11 hits that inhibited nematode motility. Based on these findings, we performed chemogenomic screening and tested 32 additional compounds, identifying 6 more active hits. Overall, 6 intestinal (single-species), 5 potential pan-intestinal (whipworm and hookworm) and 6 pan-Phylum Nematoda (intestinal and filarial species) small molecule inhibitors were identified, including multiple azoles, Tadalafil and Torin-1. The active hit compounds targeted three different target classes in humans, which are involved in various pathways, including carbohydrate, amino acid and nucleotide metabolism. Last, using representative inhibitors from each target class, we demonstrated in vivo efficacy characterized by negative effects on parasite fecundity in hamsters infected with hookworms.

Cognitive and Microbiome Impacts of Experimental Ancylostoma ceylanicum Hookworm Infections in Hamsters.

Hookworms are one of the most prevalent and important parasites, infecting ~500 million people worldwide. Hookworm disease is among the leading causes of iron-deficiency anemia in the developing world and is associated with significant growth stunting and malnutrition. In humans, hookworms appear to impair memory and other forms of cognition, although definitive data are hard to come by. Here we study the impact of a human hookworm parasite, Ancylostoma ceylanicum, on cognition in hamsters in a controlled laboratory setting. We developed tests that measure long-term memory in hamsters. We find that hookworm-infected hamsters were fully capable of detecting a novel object. However, hookworm-infected hamsters were impaired in detecting a displaced object. Defects could be discerned at even at low levels of infection, whereas at higher levels of infection, hamsters were statistically unable to distinguish between displaced and non-displaced objects. These spatial memory deficiencies could not be attributed to defects in infected hamster mobility or to lack of interest. We also found that hookworm infection resulted in reproducible reductions in diversity and changes in specific taxanomic groups in the hamster gut microbiome. These data demonstrate that human hookworm infection in a laboratory mammal results in a specific, rapid, acute, and measurable deficit in spatial memory, and we speculate that gut alterations could play some role in these cognitive deficits. Our findings highlight the importance of hookworm elimination and suggest that finer tuned spatial memory studies be carried out in humans.

Dried whole-plant Artemisia annua slows evolution of malaria drug resistance and overcomes resistance to artemisinin.

Pharmaceutical monotherapies against human malaria have proven effective, although ephemeral, owing to the inevitable evolution of resistant parasites. Resistance to two or more drugs delivered in combination will evolve more slowly; hence combination therapies have become the preferred norm in the fight against malaria. At the forefront of these efforts has been the promotion of Artemisinin Combination Therapy, but despite these efforts, resistance to artemisinin has begun to emerge. In 2012, we demonstrated the efficacy of the whole plant (WP)--not a tea, not an infusion--as a malaria therapy and found it to be more effective than a comparable dose of pure artemisinin in a rodent malaria model. Here we show that WP overcomes existing resistance to pure artemisinin in the rodent malaria Plasmodium yoelii. Moreover, in a long-term artificial selection for resistance in Plasmodium chabaudi, we tested resilience of WP against drug resistance in comparison with pure artemisinin (AN). Stable resistance to WP was achieved three times more slowly than stable resistance to AN. WP treatment proved even more resilient than the double dose of AN. The resilience of WP may be attributable to the evolutionary refinement of the plant's secondary metabolic products into a redundant, multicomponent defense system. Efficacy and resilience of WP treatment against rodent malaria provides compelling reasons to further explore the role of nonpharmaceutical forms of AN to treat human malaria.

Pharmacokinetics of artemisinin delivered by oral consumption of Artemisia annua dried leaves in healthy vs. Plasmodium chabaudi-infected mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The Chinese have used Artemisia annua as a tea infusion to treat fever for >2000 years. The active component is artemisinin. Previously we showed that when compared to mice fed an equal amount of pure artemisinin, a single oral dose of dried leaves of Artemisia annua (pACT) delivered to Plasmodium chabaudi-infected mice reduced parasitemia at least fivefold. Dried leaves also delivered >40 times more artemisinin in the blood with no toxicity. The pharmacokinetics (PK) of artemisinin delivered from dried plant material has not been adequately studied. MATERIALS AND METHODS: Healthy and Plasmodium chabaudi-infected mice were oral gavaged with pACT to deliver a 100 mg kg(-1) body weight dose of artemisinin. Concentrations of serum artemisinin and one of its liver metabolites, deoxyartemisinin, were measured over two hours by GCMS. RESULTS: The first order elimination rate constant for artemisinin in pACT-treated healthy mice was estimated to be 0.80 h(-1) with an elimination half-life (T½) of 51.6 min. The first order absorption rate constant was estimated at 1.39 h(-1). Cmax and Tmax were 4.33 mg L(-1) and 60 min, respectively. The area under the curve (AUC) was 299.5 mg min L(-1). In contrast, the AUC for pACT-treated infected mice was significantly greater at 435.6 mg min L(-1). Metabolism of artemisinin to deoxyartemisinin was suppressed in infected mice over the period of observation. Serum levels of artemisinin in the infected mice continued to rise over the 120 min of the study period, and as a result, the T½ was not determined; the Cmax and Tmax were estimated at ≥6.64 mgL(-1) and ≥120 min, respectively. Groups of healthy mice were also fed either artemisinin or artemisinin mixed in mouse chow. When compared at 60 min, artemisinin was undetectable in the serum of mice fed 100 mg AN kg(-1) body weight. When plant material was present either as mouse chow or Artemisia annua pACT, artemisinin levels in the serum rose to 2.44 and 4.32 mg L(-1), respectively, indicating that the presence of the plant matrix, even that of mouse chow, had a positive impact on the appearance of artemisinin in the blood. CONCLUSIONS: These results showed that artemisinin and one of its drug metabolites were processed differently in healthy and infected mice. The results have implications for possible therapeutic use of pACT in treating malaria and other artemisinin-susceptible diseases.

Genetic diversity of ixodid ticks parasitizing eastern mouse and dwarf lemurs in Madagascar, with descriptions of the larva, nymph, and male of Ixodes lemuris (Acari: Ixodidae).

The ixodid ticks parasitizing small-bodied nocturnal mouse and dwarf lemurs (Primates, Cheirogaleidae) in Madagascar are poorly documented. At Tsinjoarivo, a high-altitude eastern rain forest, mouse and dwarf lemurs were parasitized by ixodid ticks. At Ranomafana, a montane southeastern rain forest, dwarf lemurs hosted a species of Ixodes, whereas mouse lemurs were parasitized by Haemaphysalis lemuris. Ixodes specimens represent all active stages, and females are morphologically consistent with previous descriptions of Ixodes lemuris females, the only described stage in the literature. Morphological comparisons and genetic analysis using fragments of COI gene confirm that all Ixodes ticks from Tsinjoarivo and Ranomafana forests belong to the same species, i.e., Ixodes lemuris. Thus, we are able to provide descriptions of the previously unknown larva, nymph, and male. Mouse lemurs at both locations were parasitized only by immature stages of I. lemuris (at Tsinjoarivo) or H. lemuris (at Ranomafana), whereas dwarf lemurs were parasitized by all stages of I. lemuris. We suggest that ecological and biogeographical conditions may affect the pattern of tick infestation at Tsinjoarivo and Ranomafana. Additional studies are necessary to understand the tick-host associations of small-bodied nocturnal lemurs.

Dried whole plant Artemisia annua as an antimalarial therapy.

Drugs are primary weapons for reducing malaria in human populations. However emergence of resistant parasites has repeatedly curtailed the lifespan of each drug that is developed and deployed. Currently the most effective anti-malarial is artemisinin, which is extracted from the leaves of Artemisia annua. Due to poor pharmacokinetic properties and prudent efforts to curtail resistance to monotherapies, artemisinin is prescribed only in combination with other anti-malarials composing an Artemisinin Combination Therapy (ACT). Low yield in the plant, and the added cost of secondary anti-malarials in the ACT, make artemisinin costly for the developing world. As an alternative, we compared the efficacy of oral delivery of the dried leaves of whole plant (WP) A. annua to a comparable dose of pure artemisinin in a rodent malaria model (Plasmodium chabaudi). We found that a single dose of WP (containing 24 mg/kg artemisinin) reduces parasitemia more effectively than a comparable dose of purified drug. This increased efficacy may result from a documented 40-fold increase in the bioavailability of artemisinin in the blood of mice fed the whole plant, in comparison to those administered synthetic drug. Synergistic benefits may derive from the presence of other anti-malarial compounds in A. annua. If shown to be clinically efficacious, well-tolerated, and compatible with the public health imperative of forestalling evolution of drug resistance, inexpensive, locally grown and processed A. annua might prove to be an effective addition to the global effort to reduce malaria morbidity and mortality.