Towards an In Vitro Model of Plasmodium Hypnozoites Suitable for Drug Discovery

Contains fulltext : 96475.pdf (publisher's version ) (Open Access)BACKGROUND: Amongst the Plasmodium species in humans, only P. vivax and P. ovale produce latent hepatic stages called hypnozoites, which are responsible for malaria episodes long after a mosquito bite. Relapses contribute to increased morbidity, and complicate malaria elimination programs. A single drug effective against hypnozoites, primaquine, is available, but its deployment is curtailed by its haemolytic potential in glucose-6-phosphate dehydrogenase deficient persons. Novel compounds are thus urgently needed to replace primaquine. Discovery of compounds active against hypnozoites is restricted to the in vivo P. cynomolgi-rhesus monkey model. Slow growing hepatic parasites reminiscent of hypnozoites had been noted in cultured P. vivax-infected hepatoma cells, but similar forms are also observed in vitro by other species including P. falciparum that do not produce hypnozoites. METHODOLOGY: P. falciparum or P. cynomolgi sporozoites were used to infect human or Macaca fascicularis primary hepatocytes, respectively. The susceptibility of the slow and normally growing hepatic forms obtained in vitro to three antimalarial drugs, one active against hepatic forms including hypnozoites and two only against the growing forms, was measured. RESULTS: The non-dividing slow growing P. cynomolgi hepatic forms, observed in vitro in primary hepatocytes from the natural host Macaca fascicularis, can be distinguished from similar forms seen in P. falciparum-infected human primary hepatocytes by the differential action of selected anti-malarial drugs. Whereas atovaquone and pyrimethamine are active on all the dividing hepatic forms observed, the P. cynomolgi slow growing forms are highly resistant to treatment by these drugs, but remain susceptible to primaquine. CONCLUSION: Resistance of the non-dividing P. cynomolgi forms to atovaquone and pyrimethamine, which do not prevent relapses, strongly suggests that these slow growing forms are hypnozoites. This represents a first step towards the development of a practical medium-throughput in vitro screening assay for novel hypnozoiticidal drugs

Effect of Aging on Healthcare Costs of Inflammatory Bowel Disease: A Glimpse into the Future

Background:Population aging is expected to result in a substantial additional burden on healthcare resources in the near future. We aimed to assess the current and future impact of aging on direct healthcare costs (DHC) attributed to inflammatory bowel disease (IBD).Methods:Patients with IBD from a Dutch multicenter cohort filled out 3-monthly questionnaires for 2 years. Elderly (60 yr) and younger patients (18-60 yr) IBD were analyzed for differences in 3-monthly DHC, productivity losses, and out-of-pocket costs. Prevalence rates were obtained from a health insurance database. Estimates of annual DHC and prevalence rates were applied to the total Dutch adult population in 2011 and then projected to 2040, using predicted changes in population demography, prices, and volume.Results:IBD-attributable DHC were lower in elderly than in younger patients with IBD with respect to 3-monthly DHC (Euro359 versus Euro978, P < 0.01), productivity losses (Euro108 versus Euro456, P < 0.01), and out-of-pocket costs (Euro40 versus Euro57, P < 0.01). Between 2011 and 2040, the percentage of elderly IBD patients in the Netherlands has been projected to rise from 24% to 35%. Between 2011 and 2040, DHC of the total IBD population in the Netherlands are projected to increase from Euro161 to Euro661 million. Population aging accounted for 1% of this increase, next to rising prices (29%), and volume growth (70%).Conclusions:Population aging has a negligible effect on IBD-attributable DHC of the IBD population in the near future, because the average costs incurred by elderly patients with IBD are considerably lower than those incurred by younger patients with IBD

Evolution of Costs of Inflammatory Bowel Disease over Two Years of Follow-Up

Background With the increasing use of anti-TNF therapy in inflammatory bowel disease (IBD), a shift of costs has been observed with medication costs replacing hospitalization and surgery as major cost driver. We aimed to explore the evolution of IBD-related costs over two years of follow-up. Methods and Findings In total 1,307 Crohn's disease (CD) patients and 915 ulcerative colitis (UC) patients were prospectively followed for two years by three-monthly web-based questionnaires. Changes of healthcare costs, productivity costs and out-of-pocket costs over time were assessed using mixed model analysis. Multivariable logistic regression analysis was used to identify costs drivers. In total 737 CD patients and 566 UC were included. Total costs were stable over two years of follow-up, with annual total costs of (sic)7,835 in CD and (sic)3,600 in UC. However, within healthcare costs, the proportion of anti-TNF therapy-related costs increased from 64% to 72% in CD (p<0.01) and from 31% to 39% in UC (p < 0.01). In contrast, the proportion of hospitalization costs decreased from 19% to 13% in CD (p<0.01), and 22% to 15% in UC (p < 0.01). Penetrating disease course predicted an increase of healthcare costs (adjusted odds ratio (adj. OR) 1.95 (95% CI 1.02-3.37) in CD and age <40 years in UC (adj. OR 4.72 (95% CI 1.61-13.86)). Conclusions BD-related costs remained stable over two years. However, the proportion of anti-TNF-related healthcare costs increased, while hospitalization costs decreased. Factors associated with increased costs were penetrating disease course in CD and age <40 in UC

Persistence and activation of malaria hypnozoites in long-term primary hepatocyte cultures

Comment in: Malarial liver parasites awaken in culture. Barnwell JW, Galinski MR. Nat Med. 2014 Mar;20(3):237-9. doi: 10.1038/nm.3498. PMID: 24603792International audienceMalaria relapses, resulting from the activation of quiescent hepatic hypnozoites of Plasmodium vivax and Plasmodium ovale, hinder global efforts to control and eliminate malaria. As primaquine, the only drug capable of eliminating hypnozoites, is unsuitable for mass administration, an alternative drug is needed urgently. Currently, analyses of hypnozoites, including screening of compounds that would eliminate them, can only be made using common macaque models, principally Macaca rhesus and Macaca fascicularis, experimentally infected with the relapsing Plasmodium cynomolgi. Here, we present a protocol for long-term in vitro cultivation of P. cynomolgi-infected M. fascicularis primary hepatocytes during which hypnozoites persist and activate to resume normal development. In a proof-of-concept experiment, we obtained evidence that exposure to an inhibitor of histone modification enzymes implicated in epigenetic control of gene expression induces an accelerated rate of hypnozoite activation. The protocol presented may further enable investigations of hypnozoite biology and the search for compounds that kill hypnozoites or disrupt their quiescence