In vitro Screening of Compounds against Laboratory and Field Isolates of Human Hookworm Reveals Quantitative Differences in Anthelmintic Susceptibility

Abstract

Abstract. A panel of 80 compounds was screened for anthelmintic activity against a laboratory strain of Ancylostoma ceylanicum and field isolates of hookworm obtained from school children in the Kintampo North District of the Brong Ahafo Region of Ghana. Although the laboratory strain of A. ceylanicum was more susceptible to the compounds tested than the field isolates of hookworm, a twofold increase in compound concentration resulted in comparable egg hatch percent inhibition for select compounds. These data provide evidence that the efficacy of anthelmintic compounds may be species-dependent and that field and laboratory strains of hookworm differ in their sensitivities to the anthelmintics tested. These data also suggest that both compound concentration and hookworm species must be considered when screening to identify novel anthelmintic compounds.Human hookworm disease results from infection by two genera of hookworms, Ancylostoma spp. and Necator americanus. Albendazole (ABZ) and mebendazole (MBZ) are the primary drugs used to treat hookworm infection. A recent meta-analysis and review of field-based studies have shown that single-dose treatment cure rates with ABZ and MBZ are low (72% and 15%, respectively).1,2 Compounding these treatment failure rates in humans is the well-documented emergence of drug resistance to ABZ and MBZ among parasitic nematodes of agricultural and veterinary importance. [3][4][5] In light of this information, the development of novel anthelmintic chemotherapeutics is necessary.Currently, the identification and development of novel anthelmintic compounds to cure hookworm infection rely on laboratory-based screening for inhibitors of egg hatching, larval motility and morphology, and/or adult worm survival.6-9 However, novel compounds identified using small animal models of hookworm infection are rarely screened for comparable activity against field isolates of human hookworms. [10][11][12][13][14][15][16] Therefore, the correlation between the anthelmintic activity of compounds against laboratory and field isolates of human hookworms remains largely unknown.Moreover, for those cases in which anthelmintic activity is investigated, the larvicidal, rather than ovicidal, properties of a compound are usually analyzed. [17][18][19][20] Ovicidal activity is more frequently and most readily assayed in resource-limited field settings, where larval and adult hookworm-based assays are impractical tools for assessing anthelmintic activity. [21][22][23]

Peroxiredoxin-1 from the Human Hookworm Ancylostoma ceylanicum Forms a Stable Oxidized Decamer and Is Covalently Inhibited by Conoidin A

“…Conoidin A inhibits TgPrxII with an IC 50 of 23 μM by binding covalently to the peroxidatic cysteine (Liu, et al, 2010). More relevant to the present study, conoidin A treatment of A. ceylanicum eggs purified from the feces of infected hamsters as well as eggs from field isolates of human hookworms resulted in a significant inhibition of egg hatching, revealing the nematicidal activity of conoidin A (Treger, et al, 2013). …”

“…Our observation that AcePrx-1 is predominately expressed in adult hookworms and not in egg or larval stages suggests that inhibition of egg hatching by conoidin A (Treger, et al, 2013) may occur through inhibition of a protein other than AcePrx-1. A second peroxiredoxin has been identified in A. ceylanicum but its expression pattern and biochemical activity have not yet been studied.…”

Effectiveness of Albendazole for Hookworm Varies Widely by Community and Correlates with Nutritional Factors: A Cross-Sectional Study of School-Age Children in Ghana

“…34,35 All study medications were administered under direct observation by GHS Pharmacists based at the Kintampo Health Center on one of two treatment days (June 24 or June 30, 2011), and the anthelminthic activity of the albendazole preparation used in the study was confirmed in the field using an in vitro assay. 43 Stool specimens were collected from treated individuals 10-14 days later and evaluated by fecal microscopy using the Kato-Katz method as described above. This time point was chosen to measure the effect of treatment on fecal egg excretion before reinfection.…”

Phenolic Metabolites of Dalea ornata Affect Both Survival and Motility of the Human Pathogenic Hookworm Ancylostoma ceylanicum

“…The overall structural connectivity was established by HSQC, HMBC, and COSY spectroscopic data (Figures S2–S6, Supporting Information) and by comparison with known compounds. 28,30 ECD data were used to define the absolute configuration at C-2 in compound 1 . The ECD spectrum (Figure S1, Supporting Information) showed sequential positive and negative Cotton effects near 350 and 310 nm for the n → π* and π → π* electronic transitions, respectively.…”

“…26,27 A panel of azole-inspired synthetic compounds, consisting of nitrogen- and oxygen-containing heterocycles (e.g., furoxan analogues), was tested against various A. ceylanicum isolates in a more recent study that revealed differences in susceptibility of laboratory versus field isolates of Ancylostoma spp. 28 …”