Surveillance for Soil-Transmitted Helminths in High-Risk County, Mississippi, USA

Recent reports of hookworm infection in Alabama, USA, has prompted surveillance in Mississippi, given the states' similar environmental conditions. We collected stool specimens from 277 children in Rankin County, Mississippi. Kato-Katz microscopic smear, agar plate culture, and quantitative PCR indicated no soil-transmitted helminths. Nevertheless, further surveillance in other high-risk Mississippi counties is warranted.

Performance of microscopy compared to conventional PCR in identification of soil-transmitted helminth infections among antenatal women in a low-prevalence setting

PURPOSE

Traditional microscopy-based methods may provide inaccurate estimates of Soil transmitted helminth (STH) infections in mild intensity of infection. Therefore, we aimed to determine the prevalence of STH infections using molecular diagnostic methods and compare the diagnostic performance of microscopy with polymerase chain reaction (PCR) in stool samples collected from pregnant women in primary care settings in Puducherry, India.

METHODOLOGY

A singleplex PCR assay was developed to detect three species of STHs, namely Ascaris lumbricoides, Necator americanus, and Ancylostoma duodenale, by targeting the internal transcribed spacer regions (ITS1 and ITS2) of 5.8S rRNA. The PCR generated 420, 662, and 515 base pairs of DNA for the respective organisms. In addition to singleplex PCR, wet and concentration microscopy techniques were used. The results were expressed as percentages with 95% confidence intervals, and the diagnostic performance of microscopy was compared with PCR in terms of sensitivity, specificity, and positive, negative predictive values and kappa statistics.

RESULTS

Among the 650 pregnant women included, 48.8% were aged 25 years or less, 59% were primigravida, and half were from rural areas. The overall prevalence of any STH infection was higher in PCR compared to microscopy (8.9% vs. 7.2%). The prevalence of Ascaris lumbricoides was higher by microscopy (5.4% vs 2.6%), while the prevalence of Necator americanus was higher by PCR (6.3%) than by microscopy (1.8%). No species of Ancylostoma duodenale was detected. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of microscopy for detecting any STH infection was 22.4%, 94.3%, 27.7%, and 92.5%, respectively. The agreement between microscopy and PCR for the identification is as follows: for any STH infection, k ​= ​0.12, Ascaris k ​= ​0.16, and Necator k ​= ​0.20, respectively.

CONCLUSION

The prevalence of any STH infection identified by PCR was higher than microscopy, and the agreement between the two methods was poor.

Development of a hookworm egg hatching assay to determine the ovicidal effects of anthelminthics

BACKGROUND

Few anthelminthics are currently available, manifesting the urgent need for new treatment options. In vitro profiling of current anthelminthics against larval and adult stage helminths displayed varying effects on closely related worm species and between life stages of the same species. Conversely, limited research has been performed on the egg stage of human hookworms, and the effects of investigational compounds on the egg stage are not routinely assessed.

METHODS

We profiled the development and hatching of Heligmosomoides polygyrus, Ancylostoma duodenale and Necator americanus eggs isolated from rodent faeces in liquid media with various nutrient levels, osmolar concentrations, and acidities in dependence on incubation temperature and light exposure. Incubation conditions were optimised to allow the study of drug effect on immature and embryonated eggs. We analysed concentration-effect relationships of commercially available anthelminthics over 72 h.

RESULTS

Rapid embryonation and hatching were observed at room temperature with and without light exposure without nutrient supplementation in a wide range of acidities. Hookworms hatched optimally at room temperature in PBS achieving > 75% hatching over 34 h. Developmental delays were seen when eggs were stored at 4 °C with no effect on viability. Similar delays were also seen with increased osmolar concentrations resulting in decreased viability. Benzimidazole anthelminthics effectively reduced the viability and prevented hatching of hookworm eggs, with albendazole and thiabendazole eliciting particularly potent effects at EC₅₀ values below 1 µM. Macrolide anthelminthics as well as emodepside, oxantel pamoate, and pyrantel pamoate were inactive while monepantel, levamisole, and tribendimidine displayed varied potencies among the hookworm species.

CONCLUSION

The presented egg-hatching assay will complement ongoing anthelminthic drug discovery and allow a full characterisation of drug activity against all life stages. In the development and application of the egg-hatching assay, good accordance was observed between the three hookworm species evaluated. Marketed anthelminthics show differences of drug action compared to larval and adult stages highlighting the importance of profiling drug activity against all life stages.

Establishment of a Simple and Rapid Nucleic Acid Detection Method for Hookworm Identification

Hookworm infection is one of the most common neglected tropical diseases and is mainly found in tropical and subtropical areas. Two species of human hookworm are distributed in China, i.e., Ancylostoma duodenale (AD) and Necator americanus (NA).

BACKGROUND

Traditional microscopic technology such as the Kato-Katz method is not suitable for hookworm diagnosis due to the rapid degeneration of fragile hookworm eggs or for species identification of hookworm infection. The aim of the present study was to establish and evaluate a novel nucleic acid detection method based on recombinase-aided isothermal amplification (RAA) for the detection of hookworm infections and species identification.

METHODS

Based on the specific target gene sequences of hookworms (5.8S rRNA for AD and ITS2 for NA, respectively), we designed and synthesized amplification primers and fluorescence probes referring to the principle of the fluorescence recombinase-aided amplification (RAA) technique.

RESULTS

Each assay provided specific amplification of larval DNA from AD and NA by fluorescence RAA, and the detection limits in plasmids reached 10² copies and 10 copies, respectively. Genomic DNA of two hookworm species was successfully detected at a concentration of 0.1 pg/μL, revealing a high detection sensitivity. No positive amplification occurred for genomic DNA from crossed hookworm species and genomic DNA from Cryptosporidium, Giardia lamblia, Strongyloides stercoralis, Schistosoma japonicum, Ascaris lumbricoides, and Clonorchis sinensis, revealing a satisfactory specificity. Fecal sample detection results demonstrated a similar efficacy to the Kato-Katz method; however, it had a greater sensitivity than the larvae culture method.

CONCLUSION

A simple and rapid nucleic acid method was successfully established based on RAA, which improved the detection efficacy and species identification for human hookworm infections.

Safety and immunogenicity of the Na-APR-1 hookworm vaccine in infection-naïve adults

Background

The Necator americanus hemoglobinase, aspartic protease-1 (Na-APR-1), facilitates the ability of adult hookworms to parasitize the intestine of their human hosts. A recombinant version of APR-1 protected laboratory animals against hookworm infection by inducing neutralizing antibodies that block the protein’s enzymatic activity and thereby impair blood feeding. A catalytically inactive version of the wild-type hemoglobinase (Na-APR-1(M74)) was expressed by infiltrating Nicotiana benthamiana tobacco plants with an Agrobacterium tumefaciens strain engineered to express the vaccine antigen, which was adjuvanted with aluminum hydroxide adjuvant (Alhydrogel).

Methods

An open-label dose-escalation Phase 1 clinical trial was conducted in 40 healthy, hookworm-naïve adult volunteers in the United States. Participants received 30 or 100 µg of recombinant Na-APR-1(M74) with Alhydrogel or with Alhydrogel co-administered with one of two doses (2.5 or 5.0 µg) of an aqueous formulation of Glucopyranosyl Lipid A (GLA-AF). Intramuscular injections of study vaccine were administered on days 0, 56, and 112.

Results

Na-APR-1(M74)/Alhydrogel was well-tolerated; the most frequent adverse events were mild or moderate injection site tenderness and pain, and mild or moderate nausea and headache. No serious adverse events or adverse events of special interest related to vaccination were observed. Significantly higher levels of antigen-specific IgG antibodies were induced in those who received 100 µg Na-APR-1(M74) than those who received 30 µg of antigen. Adding GLA-AF to Na-APR-1(M74)/Alhydrogel resulted in higher levels of IgG against Na-APR-1(M74) in both the 30 and 100 µg Na-APR-1(M74) groups in comparison to the non-GLA formulations at the same antigen dose.

Conclusions

Vaccination of hookworm-naïve adults with recombinant Na-APR-1(M74) was well-tolerated, safe, and induced significant IgG responses against the vaccine antigen Na-APR-1(M74). Given these favorable results, clinical trials of this product were initiated in hookworm-endemic areas of Gabon and Brazil.

High prevalence of soil-transmitted helminth infections in Myanmar schoolchildren

Background

Achieving the elimination of soil-transmitted helminth (STH) infections requires a sufficient understanding of the current epidemiological status of STH endemicity. We aimed to examine the status of STH in Myanmar – a country with the eighth highest STH prevalence in the world, 10 years after instigation of the national deworming programme.

Methods

In August 2016 we screened for STH infections using Kato Katz (KK) microscopy and real-time PCR (qPCR) in schoolchildren from the Bago Region township of Phyu, a STH sentinel site in Myanmar. Ten schools were randomly selected, and one stool sample each from a total of 264 students was examined. Prevalence and intensity of infection were calculated for each STH.

Results

High prevalence of STH was identified in the study area with 78.8% of the schoolchildren infected with at least one STH by qPCR, and 33.3% by KK. The most prevalent STH was Trichuris trichiura, diagnosed by both KK (26.1%) and qPCR (67.1%), followed by Ascaris lumbricoides (15.5% KK; 54.9% qPCR). No hookworm infections were identified by KK; however, the qPCR analysis showed a high prevalence of Ancylostoma sp. infection (29.6%) with few Necator americanus (1.1%) infections.

Conclusions

Despite bi-annual deworming of schoolchildren in the fourth-grade and below, STH prevalence remains stubbornly high. These results informed the expansion of the Myanmar National STH control programme to include all school-aged children by the Ministry of Health and Sports in 2017, however further expansion to the whole community should be considered along with improving sanitation and hygiene measures. This would be augmented by rigorous monitoring and evaluation, including national prevalence surveys.

Computer-aided identification of potential inhibitors against Necator americanus glutathione S-transferase 3

Hookworm infection is caused by the blood-feeding hookworm gastrointestinal nematodes. Its harmful effects include anemia and retarded growth and are common in the tropics. A current control method involves the mass drug administration of synthetic drugs, mainly albendazole and mebendazole. There are however concerns of low efficacy and drug resistance due to their repeated and excessive use. Although, Necator americanus glutathione S-transferase 3 (Na-GST-3) is a notable target, using natural product libraries for computational elucidation of promising leads is underexploited. This study sought to use pharmacoinformatics techniques to identify compounds of natural origins with the potential to be further optimized as promising inhibitors. A compendium of 3182 African natural products together with five known helminth GST inhibitors including Cibacron blue was screened against the active sites of the Na-GST-3 structure (PDB ID: 3W8S). The hit compounds were profiled to ascertain the mechanisms of binding, anthelmintic bioactivity, physicochemical and pharmacokinetic properties. The AutoDock Vina docking protocol was validated by obtaining 0.731 as the area under the curve calculated via the receiver operating characteristics curve. Four compounds comprising ZINC85999636, ZINC35418176, ZINC14825190, and Dammarane Triterpene13 were identified as potential lead compounds with binding energies less than -9.0 kcal/mol. Furthermore, the selected compounds formed key intermolecular interactions with critical residues Tyr95, Gly13 and Ala14. Notably, ZINC85999636, ZINC14825190, and dammarane triterpene13 were predicted as anthelmintics, whilst all the four molecules shared structural similarities with known inhibitors. Molecular modelling showed that the compounds had reasonably good binding free energies. More so, they had high binding affinities when screened against other variants of the Na-GST, namely Na-GST-1 and Na-GST-2. Ligand quality assessment using ligand efficiency dependent lipophilicity, ligand efficiency, ligand efficiency scale and fit quality scale showed the molecules are worthy candidates for further optimization. The inhibitory potentials of the molecules warrant in vitro studies to evaluate their effect on the heme regulation mechanisms.

Molecular modelling and de novo fragment-based design of potential inhibitors of beta-tubulin gene of Necator americanus from natural products

The emergence of drug resistance against the known hookworm drugs namely albendazole and mebendazole and their reduced efficacies necessitate the need for new drugs. Chemically diverse natural products present plausible templates to augment hookworm drug discovery. The present work utilized pharmacoinformatics techniques to predict African natural compounds ZINC95486082, ZINC95486052 and euphohelionon as potential inhibitory molecules of the hookworm Necator americanus β tubulin gene. A library of 3390 compounds was screened against a homology-modelled structure of β tubulin. The docking results obtained from AutoDock Vina was validated with an acceptable area under the curve (AUC) of 0.714 computed from the receiver operating characteristic (ROC) curve. The three selected compounds had favourable binding affinities and were predicted to form no interactions with the resistance-associated mutations Phe167, Glu198 and Phe200. The compounds were predicted as anthelmintics using a Bayesian-based technique and were pharmacologically profiled to be druglike. Further molecular dynamics simulations and MM-PBSA calculations showed the compounds as promising anthelmintic drug leads. Novel critical residues comprising Leu246, Asn247 and Asn256 were also predicted for binding. Euphohelionon was selected as a template for the de novo fragment-based design of five compounds labelled A1, A2, A3, A4 and A5; with four of them having SAscore values below 6, denoting easy synthesis. All the five de novo molecules docked firmly in the binding pocket of the β tubulin with no binding interactions with the three known resistance mutation residues. Binding energies of −8.2, −7.6, −7.3, −7.2 and −6.8 kcal/mol were obtained for A1, A2, A3, A4 and A5, respectively. The identified compounds can serve as treasure troves from which future potent anthelmintics can be designed. The current study strives to assuage the hookworm disease burden, especially making available molecules with the potential to circumvent the chemoresistance.

Identification of Small Molecules of the Infective Stage of Human Hookworm Using LCMS-Based Metabolomics and Lipidomics Protocols

Hookworm infections affect millions of people worldwide and are responsible for impaired mental and physical growth in children, and anemias. There is no vaccine, and increasing anthelmintic drug resistance in nematodes of domestic animals, and reduced drug cure rates in nematode infections of humans is alarming. Despite this looming health problem, there is a significant knowledge gap in terms of nonproteinaceous "excretory/secretory products" (ESPs) and how they orchestrate a parasitic existence. In the current study, we have conducted the first metabolomic and lipidomic analysis of the infective third-stage filariform larvae (L3) of the predominant human hookworm Necator americanus using liquid chromatography-mass spectrometry. Altogether, we have identified a total of 645 small molecules that were mainly produced through amino acid and glycerophospholipid metabolism. Putatively, 495 metabolites were unique to the somatic tissue extract, and 34 metabolites were present only in the ESP component. More than 21 novel mass features with nitrogen and sulfur functional groups were detected in the ESP component for the first time from helminths. While this study could not establish the biological functions of the metabolites identified, literature searches revealed that these metabolites possess various biological properties, including anti-inflammatory activities. These metabolites are likely used by the parasite upon exposure to a host to facilitate skin penetration, passage through different tissues, and immune regulation in the small bowel. Overall, the results presented herein offer significant insight into the metabolome of N. americanus L3 and have the potential to instigate future work to establish biomarkers of infection. This area urgently needs attention, given the lack of sensitive point-of-care diagnostic tools.

Hookworm infection in central China: morphological and molecular diagnosis

BACKGROUND

Necator americanus is one of the major etiological agents of human ancylostomiasis. Historically, the epidemiology of ancylostomiasis in Henan Province of central China and the molecular characteristics of N. americanus have been poorly understood.

METHODS

In this study, we report a case of ancylostomiasis in Zhengzhou city of Henan Province. We also review the epidemiology of ancylostomiasis in Henan Province from 1949 to 2020. In addition, the complete mitochondrial (mt) genome of one clinical isolate is fully characterized using Illumina sequencing. All available mt genomes of hookworms in GenBank were included to reconstruct the phylogeny using both maximum likelihood (ML) and Bayesian inference (BI) methods.

RESULTS

A total of three worms were collected from the patient. These worms were identified as N. americanus based on morphological characteristics as well as confirmed by genotyping with the barcoding gene cox1. Although ancylostomiasis cases have dropped substantially in recent years, hookworm infection is still a public health problem in underdeveloped areas and remote rural areas in Henan Province. The mt genome features of the N. americanus contained 12 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and a major non-coding region. The nad1 gene showed high sequence variability among isolates, which is worth considering for future genetic studies of N. americanus. Phylogenetic analyses support the monophyly of hookworm isolates from different hosts and distinct geographical locations.

CONCLUSIONS

The mt genome of N. americanus presented here will serve as a useful data set for studying population genetics and phylogenetic relationships of hookworms. Positive measures for preventing and controlling ancylostomiasis are required by both health services and individuals in Henan Province.

Establishing a controlled hookworm human infection (CHHI) model for Africa: A report from the stakeholders meeting held in Lambaréné, Gabon, November 10-11, 2019

BACKGROUND

Hookworm is a major contributor to worldwide disease burden with over 230 million people infected. It has been identified as one of the Neglected Tropical Diseases that can be controlled and even eliminated through mass drug administration and other effective interventions. Mathematical models have shown that hookworm can only be eliminated via a vaccine. Controlled Hookworm Human Infection (CHHI) models can facilitate rapid development of vaccines and drugs.

METHODS

As a first step towards the establishment of CHHI in Africa, we held a stakeholders meeting in Lamberene, Gabon from 10 to 11 November 2019.

RESULTS

Discussions revolved around the roles of the different regulatory institutions concerned; the need to strengthen existing regulatory capacity and the role of legislation; creating Gabon-specific ethical guidelines to govern Controlled Human Infection (CHI) studies; development of a study protocol; consideration of cultural and social peculiarities; the need for regular joint review meetings between interested parties throughout the process of protocol implementation; and participant compensation. Moreover, operational considerations concerning the introduction of CHHI in Gabon include the use of the local strain of hookworm for the challenge infections, capacity building for the local production of challenge material, and the establishment of adequate quality assurance procedures.

CONCLUSION

The workshop addressed several of the anticipated hurdles to the successful implementation of CHHI in Gabon. It is our aim that this report will stimulate interest in the implementation of this model in the sub-Saharan African setting.

Canine Parvovirus Infections in Taiwanese Pangolins (Manis pentadactyla pentadactyla)

Canine parvovirus type 2 (CPV-2) is among the most important and highly contagious pathogens that cause enteric or systemic infections in domestic and nondomestic carnivores. However, the spillover of CPV-2 to noncarnivores is rarely mentioned. Taiwanese pangolins (Manis pentadactyla pentadactyla) are threatened due to habitat fragmentation and prevalent animal trafficking. Interactions between Taiwanese pangolins, humans, and domestic animals have become more frequent in recent years. However, information about the susceptibility of pangolins to common infectious agents of domestic animals has been lacking. From October 2017 to June 2019, 4 pangolins that were rescued and treated in wildlife rescue centers in central and northern Taiwan presented with gastrointestinal signs. Gross and histopathological examination revealed the main pathologic changes to be necrotic enteritis with involvement of the crypts in all intestinal segments in 2 pangolins. By immunohistochemistry for CPV-2, there was positive labeling of cryptal epithelium throughout the intestine, and immunolabeling was also present in epidermal cells adjacent to a surgical amputation site, and in mononuclear cells in lymphoid tissue. The other 2 pangolins had mild enteritis without crypt involvement, and no immunolabeling was detected. The nucleic acid sequences of polymerase chain reaction (PCR) amplicons from these 4 pangolins were identical to a Chinese CPV-2c strain from domestic dogs. Quantitative PCR revealed a higher ratio of CPV-2 nucleic acid to internal control gene in the 2 pangolins with severe intestinal lesions and positive immunoreactivity. Herein, we present evidence of CPV-2 infections in pangolins.

Morphological and Molecular Diagnosis of Necator americanus and Ancylostoma ceylanicum Recovered from Villagers in Northern Cambodia

Human hookworm infections caused by adult Ancylostoma spp. and Necator americanus are one of the most important tropical diseases. We performed a survey of intestinal helminths using the Kato-Katz fecal examination technique targeting 1,156 villagers residing in 2 northern provinces (Preah Vihear and Stung Treng) of Cambodia in 2018. The results revealed a high overall egg positive rate of intestinal helminths (61.9%), and the egg positive rate of hookworms was 11.6%. Nine of the hookworm egg positive cases in Preah Vihear Province were treated with 5–10 mg/kg pyrantel pamoate followed by purging with magnesium salts, and a total of 65 adult hookworms were expelled in diarrheic stools. The adult hookworms were analyzed morphologically and molecularly to confirm the species. The morphologies of the buccal cavity and dorsal rays on the costa were observed with a light microscope, and the nucleotide sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) gene were analyzed. The majority of the hookworm adults (90.7%) were N. americanus, whereas the remaining 9.3% were Ancylostoma ceylanicum, a rare hookworm species infecting humans. The results revealed a high prevalence of hookworm infections among people in a northern part of Cambodia, suggesting the necessity of a sustained survey combined with control measures against hookworm infections.

Genotypic profile of benzimidazole resistance associated with SNP F167Y in the beta-tubulin gene of Necator americanus helminths obtained from Brazilian populations

Necator americanus is a worm that parasites the small intestine of humans and is highly prevalent in regions with poor sanitary conditions. The main strategy to control this helminth is by mass benzimidazole administration, however, periodic use of these drugs can select strains of parasites resistant to treatment. Single nucleotide polymorphisms (SNPs) in the beta-tubulin isotype 1 gene located at codons 167, 198 and 200 have been associated with benzimidazole resistance in some nematodes. Previously, our group detected the presence of some of these SNPs in populations of soil-transmitted helminths collected in different locations in Brazil. Here, we evaluated the SNP at codon 167, which has recently been shown to be associated with failure of benzimidazoles to treat N. americanus. Our ARMS-PCR analyses were performed using 524 single N. americanus eggs from 48 patients' feces collected in six Brazilian states; however, we did not detect any mutated samples at codon 167. This study builds on previous work, helping us monitor the presence of resistance-related genotypes in Brazilian helminth populations. The data presented here can assist in the implementation of future control strategies.

Molecular identification of Ancylostoma ceylanicum in the Philippines

Hookworms are some of the most widespread of the soil-transmitted helminths (STH) with an estimated 438.9 million people infected. Until relatively recently Ancylostoma ceylanicum was regarded as a rare cause of hookworm infection in humans, with little public health relevance. However, recent advances in molecular diagnostics have revealed a much higher prevalence of this zoonotic hookworm than previously thought, particularly in Asia. This study examined the prevalence of STH and A. ceylanicum in the municipalities of Palapag and Laoang in the Philippines utilizing real-time polymerase chain reaction (PCR) on stool samples previously collected as part of a cross-sectional survey of schistosomiasis japonica. Prevalence of hookworm in humans was high with 52.8% (n = 228/432) individuals positive for any hookworm, 34.5% (n = 149/432) infected with Necator americanus, and 29.6% (n = 128/432) with Ancylostoma spp; of these, 34 were PCR-positive for A. ceylanicum. Considering dogs, 12 (n = 33) were PCR-positive for A. ceylanicum. This is the first study to utilize molecular diagnostics to identify A. ceylanicum in the Philippines with both humans and dogs infected. Control and elimination of this zoonotic hookworm will require a multifaceted approach including chemotherapy of humans, identification of animal reservoirs, improvements in health infrastructure, and health education to help prevent infection.

Dogs and pigs are transport hosts of Necator americanus: Molecular evidence for a zoonotic mechanism of human hookworm transmission in Ghana

Hookworm infection (Necator americanus and Ancylostoma spp) causes significant morbidity in resource-limited countries. Dog and pig ownership is associated with human infection, although the mechanism through which animals increase risk remains unknown. We first confirmed this association in Kintampo North, Ghana, using a retrospective analysis and serology, followed by a prospective molecular study of animal faeces. As a proxy of exposure to dog faeces, we analysed immunoreactivity of human serum to the zoonotic nematode Toxocara canis. Anti-Toxocara antibodies were present in 62% of samples (n = 89), and reactivity was associated with dog ownership. A subsequent prospective study revealed that 43% of dog and 56% of pig faecal samples contained hookworm eggs by microscopy. PCR analysis confirmed the presence of N. americanus DNA in 47% of samples from dogs and 56% pig samples. Nematode larvae were successfully cultured from samples collected from 36 dogs and seven pigs. These results demonstrate that dogs and pigs have a likely role in the transmission of N. americanus in endemic communities.

The molecular speciation of soil-transmitted helminth eggs collected from school children across six endemic countries

BACKGROUND

The diagnosis of soil-transmitted helminths (STHs; Ascaris, Trichuris and hookworms) is traditionally based on the demonstration of eggs in stool using microscopic techniques. While molecular techniques are more appropriate to speciate STH species they are seldom applied. In this study we speciated STH eggs from stool using molecular techniques to gain insights into the distribution of both human and animal STH species in the human host.

METHODS

We speciated 207 STH egg isolates from stool collected during the baseline survey of six drug efficacy trials conducted in Brazil, Cambodia, Cameroon, Ethiopia, Tanzania and Vietnam applying a PCR - restriction fragment length polymorphisms based approach.

RESULTS

DNA of Ascaris was detected in 71 (34.3%) samples, of which all were identified as the human roundworm Ascaris lumbricoides. In 87 (42.0%) samples, DNA of Trichuris spp. was found and further speciation demonstrated the presence of the human Trichuris trichiura (100%) and the canine Trichuris vulpis (n=7; 8.0%; in Cameroon only). Hookworms were identified in 104 (50.2%) samples, with Necator americanus (n=73; 70.2%) being the predominant species followed by Ancylostoma duodenale (n=40; 38.5%).

CONCLUSIONS

Our study indicates that STH infections in humans are predominantly caused by human STH species. They also suggest that zoonotic transmission occurs on a local scale.

What does soil-transmitted helminth elimination look like? Results from a targeted molecular detection survey in Japan

BACKGROUND

Japan is one of the few countries believed to have eliminated soil-transmitted helminths (STHs). In 1949, the national prevalence of Ascaris lumbricoides was 62.9%, which decreased to 0.6% in 1973 due to improvements in infrastructure, socioeconomic status, and the implementation of national STH control measures. The Parasitosis Prevention Law ended in 1994 and population-level screening ceased in Japan; therefore, current transmission status of STH in Japan is not well characterized. Sporadic cases of STH infections continue to be reported, raising the possibility of a larger-scale recrudescence of STH infections. Given that traditional microscopic detection methods are not sensitive to low-intensity STH infections, we conducted targeted prevalence surveys using sensitive PCR-based assays to evaluate the current STH-transmission status and to describe epidemiological characteristics of areas of Japan believed to have achieved historical elimination of STHs.

METHODS

Stool samples were collected from 682 preschool- and school-aged children from six localities of Japan with previously high prevalence of STH. Caregivers of participants completed a questionnaire to ascertain access to water, sanitation and hygiene (WASH), and potential exposures to environmental contamination. For fecal testing, multi-parallel real-time PCR assays were used to detect infections of Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale and Trichuris trichiura.

RESULTS

Among the 682 children, no positive samples were identified, and participants reported high standards of WASH.

CONCLUSIONS

To our knowledge, this is the first STH-surveillance study in Japan to use sensitive molecular techniques for STH detection. The results suggest that recrudescence of STH infections has not occurred, and that declines in prevalence have been sustained in the sampled areas. These findings suggest that reductions in prevalence below the elimination thresholds, suggestive of transmission interruption, are possible. Additionally, this study provides circumstantial evidence that multi-parallel real-time PCR methods are applicable for evaluating elimination status in areas where STH prevalence is extremely low.

Safety and tolerability of experimental hookworm infection in humans with metabolic disease: study protocol for a phase 1b randomised controlled clinical trial

BACKGROUND

Abdominal obesity and presence of the metabolic syndrome (MetS) significantly increase the risk of developing diseases such as Type 2 diabetes mellitus (T2DM) with escalating emergence of MetS and T2DM constituting a significant public health crisis worldwide. Lower prevalence of inflammatory and metabolic diseases such as T2DM in countries with higher incidences of helminth infections suggested a potential role for these parasites in the prevention and management of certain diseases. Recent studies confirmed the potential protective nature of helminth infection against MetS and T2DM via immunomodulation or, potentially, alteration of the intestinal microbiota. This Phase 1b safety and tolerability trial aims to assess the effect of inoculation with helminths on physical and metabolic parameters, immune responses, and the microbiome in otherwise healthy women and men.

METHODS

Participants eligible for inclusion are adults aged 18-50 with central obesity and a minimum of one additional feature of MetS recruited from the local community with a recruitment target of 54. In a randomised, double-blind, placebo-controlled design, three groups will receive either 20 or 40 stage three larvae of the human hookworm Necator americanus or a placebo. Eligible participants will provide blood and faecal samples at their baseline and 6-monthly assessment visits for a total of 24 months with an optional extension to 36 months. During each scheduled visit, participants will also undergo a full physical examination and complete diet (PREDIMED), physical activity, and patient health (PHQ-9) questionnaires. Outcome measurements include tolerability and safety of infection with Necator americanus, changes in metabolic and immunological parameters, and changes in the composition of the faecal microbiome.

DISCUSSION

Rising cost of healthcare associated with obesity-induced metabolic diseases urgently calls for new approaches in disease prevention. Findings from this trial will provide valuable information regarding the potential mechanisms by which hookworms, potentially via alterations in the microbiota, may positively influence metabolic health.

TRIAL REGISTRATION

The protocol was registered on ANZCTR.org.au on 05 June 2017 with identifier ACTRN12617000818336. Alternatively, a Google search using the above trial registration number will yield a direct link to the trial protocol within the ANZCTR website.

Development and application of anthelminthic drugs in China

China was once a country plagued by parasitic diseases. At the beginning of the founding of the People's Republic of China, nearly 80% of the population suffered from parasitic diseases because of poverty and poor sanitary conditions. After nearly 70 years of development, China has made remarkable achievements in the prevention and control of parasitic diseases, and the prevalence of parasitic diseases has been greatly reduced. In addition to organizational leadership from the government and various preventive measures, drug treatment and drug research & development are important and irreplaceable links in prevention and control work. Since the 1950s, China has begun to introduce, produce and imitate antiparasitic drugs from abroad, such as santonin, benzimidazole, and praziquantel. Chinese scientists have also contributed to the optimization of production techniques, improvements in drug formulation, the application in the clinic and the mechanisms of actions of generic drugs. At the same time, China has independently developed tribendimidine (TrBD, a broad spectrum anthelminthic), and its anthelminthic spectrum has been comprehensively studied. It is active against almost 20 parasites, is especially superior to benzimidazoles against Necator americanus, and surpasses the effectiveness of praziquantel against Clonorchis sinensis. In the treatment of tapeworm disease, the traditional Chinese medicines pumpkin seeds and betel nuts have good curative effects for taeniasis. Chinese scientists have explored the action modes and clinical administration methods of pumpkin seeds and betel nuts, which is still the main clinical regimen for the disease. This paper reviews the history and progress of the study of anthelmintics in intestinal helminth infections since the founding of the People's Republic of China and aiming to support clinicians and drug researchers in China and other countries.

Cytokine profiles of Necator americanus and Plasmodium falciparum co-infected patients in rural Ghana

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Co-infection of hookworm with P. falciparum modulates blood parasitemia levels.

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Cytokine levels were higher in the parasite infected individuals.

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Serum eotaxin level correlate negatively with hookworm intensity.

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Deworming drug treatment alters cytokine profiles in hookworm infected subjects.

Background

Necator americanus (hookworm) and Plasmodium falciparum co-infections are common in endemic communities in rural Ghana. Human immune responses to P. falciparum and hookworm are complex, and the dynamics of cytokine levels and effector mediators are poorly understood. This study aimed to determine the effect of hookworm and P. falciparum co-infection on parasite intensities and cytokine profiles in individuals before and after deworming drug treatment.

Methods

In this cross-sectional study conducted in the Kintampo North Municipality of Ghana blood and stool samples were analyzed from 984 participants (aged 4–88 years). Stool samples were collected at baseline from all participants and examined for the presence of hookworm using the Kato-Katz method. Blood and stool samples were analysed again two weeks after albendazole treatment of hookworm infected individuals. Malaria parasitaemia was estimated by light microscopy and P. falciparum-specific 18S rRNA gene PCR method used for species identification. Serum levels of circulating cytokines interleukins -5, -10 (IL-5, IL-10), tumor necrosis factor [TNF]-α, and eotaxin [CCL11] were determined using ELISA based methods.

Results

Malaria parasitaemia was significantly reduced in hookworm and P. falciparum co-infected individuals (p = 0.0018) while hookworm intensity was similar between groups. IL-10 level was significantly higher in the co-infected individuals (39.9 ± 12.2 pg/ml) compared to the single infected or the uninfected group (10.7 ± 7.6 mg/ml). IL-5 level was higher in the hookworm only infected individual. TNF-α levels were higher in all infected groups compared to the uninfected controls. CCL11 levels were significantly higher in subjects infected with hookworm only or co-infected with hookworm and P. falciparum. There was a significantly negative correlation (r_s = −0.39, p = 0.021) between hookworm eggs per gram of stool and CCL11 levels in the group mono-infected with hookworm which was not affected by treatment. Treatment with albendazole led to a significant reduction of TNF-α (p = 0.041), IL-5 (p = 0.01) and IL-10 (p = 0.001) levels.

Conclusion

This study shows that in the absence of other helminths, co-infection of hookworm with P. falciparum may modulate blood parasitemia levels and cytokine responses. Data also show that deworming drug treatment alters these cytokine profiles in hookworm infected subjects. Future studies to elucidate the potential mechanisms underlying these observations should include an assessment of parasite specific cellular responses.

Evaluation of various culture techniques for identification of hookworm species from stool samples of children

Background & objectives

Different coproculture techniques have been developed for culturing the hookworm (HW) larvae for morphological identification in the resource-limited settings. The objective of this study was to compare the performances of Harada-Mori culture (HMC), agar plate culture (APC) and modified APC (MAPC) of HW positive stool specimens for identification of HW species in East Sikkim.

Methods

This prospective study was done in East Sikkim from May 2015 to May 2016. Stool and blood samples were collected from paediatric patients with gastrointestinal symptoms. The HW positive stool specimens by microscopy were subjected to HMC, APC and MAPC techniques to harvest HW larvae. Stoll's dilution egg count for determining egg intensity and blood parameters were performed in all the 12 HW-positive patients.

Results

Twelve of the 180 samples were found positive for HW by microscopy and predominance of Necator americanus (75%) over Ancylostoma duodenale (25%) was observed. Blood parameters results showed high pack cell volume (PCV) values in 78.6 per cent, anaemia in 75 per cent and high eosinophil count in most patients. Stoll's dilution egg count showed moderate infection in 66.6 per cent, light and heavy infections in 16.7 per cent each.

Interpretation & conclusions

Our results showed that APC yielded 100 per cent results and was easier to perform in the laboratory compared to MAPC and HMC techniques.

Identification of genetic variations in Necator americanus through resequencing by whole genome amplification

Objective

To describe a new strategy for the whole genome resequencing of small parasite samples.

Methods

Whole genome resequencing was based on a multiple displacement amplification (MDA) method. Sequencing reads were aligned with the reference genome, and a Bayesian model was used to calculate genotype probabilities. De novo genome assembly was conducted, and single nucleotide polymorphisms (SNPs) were detected. Gene ontology (GO) analysis was used to determine connections between SNPs and genes.

Results

In total, 64.12% of the parasite genome sequence was mapped to Necator americanus. fa, and 125,553 SNPs were detected. GO analysis revealed that most SNPs in coding regions were probably associated with common drug targets.

Conclusion

These results reveal the feasibility of a new strategy to detect genetic variations of small parasites. This study also provides a proof-of-principle for the molecular classification and epidemiological analysis of other parasites.

Helminth Therapy - From the Parasite Perspective

Studies in animal models and humans suggest that intentional exposure to helminths or helminth-derived products may hold promise for treating chronic inflammatory-associated diseases (CIADs). Although the mechanisms underlying 'helminth therapy' are being evaluated, little attention has been paid to the actual organisms in use. Here we examine the notion that, because of the complexity of biological symbiosis, intact helminths rather than helminth-derived products are likely to prove more useful for clinical purposes. Further, weighing potential cost/benefit ratios of various helminths along with other factors, such as feasibility of production, we argue that the four helminths currently in use for CIAD treatments in humans were selected more by happenstance than by design, and that other candidates not yet tested may prove superior.

Novel Nondietary Therapies for Celiac Disease

Celiac Disease (CeD) is defined as a chronic small intestinal immune-mediated enteropathy that is precipitated by exposure to dietary gluten in genetically predisposed individuals. CeD is one of the most common autoimmune disorders affecting around 1% of the population worldwide. Currently, the only acceptable treatment for CeD is strict, lifelong adherence to a gluten-free diet (GFD) which can often present a challenging task. A GFD alone is not sufficient to control symptoms and prevent mucosal damage that can result from unintentional gluten exposure. Moreover, long-term complications can occur in many patients. Consequently, there is an unmet need for non-dietary therapies for the management of CeD. Such therapies could serve as an adjunct to the GFD but eventually may replace it. This review will focus on and discuss non-dietary therapies currently in clinical development for the management of CeD. METHODOLOGY: We searched clinicaltrials.gov and PubMed to extract articles about celiac disease. We used keywords including, but not limited to, "celiac disease," "non-dietary," "therapeutics," "pathophysiology," "Endopeptidases," "tight junction modulators," "vaccine," and "Nexvax2". We focused mainly on articles that conducted pathophysiologic and therapeutic research in human trials.

Ancylostoma ceylanicum Hookworm in Myanmar Refugees, Thailand, 2012-2015

This hookworm, uncommonly found in humans, has a higher cure rate than that for Necator americanus hookworm.

During 2012–2015, US-bound refugees living in Myanmar–Thailand border camps (n = 1,839) were surveyed for hookworm infection and treatment response by using quantitative PCR. Samples were collected at 3 time points: after each of 2 treatments with albendazole and after resettlement in the United States. Baseline prevalence of Necator americanus hookworm was 25.4%, Ancylostoma duodenale 0%, and Ancylostoma ceylanicum (a zoonosis) 5.4%. Compared with N. americanus prevalence, A. ceylanicum hookworm prevalence peaked in younger age groups, and blood eosinophil concentrations during A. ceylanicum infection were higher than those for N. americanus infection. Female sex was associated with a lower risk for either hookworm infection. Cure rates after 1 dose of albendazole were greater for A. ceylanicum (93.3%) than N. americanus (65.9%) hookworm (p<0.001). Lower N. americanus hookworm cure rates were unrelated to β-tubulin single-nucleotide polymorphisms at codons 200 or 167. A. ceylanicum hookworm infection might be more common in humans than previously recognized.

Drug Combinations Against Soil-Transmitted Helminth Infections

The soil-transmitted helminths (STHs), Ascaris lumbricoides, hookworm and Trichuris trichiura are common in areas with warm and moist climates with little access to adequate water, sanitation, and hygiene affecting the poorest populations. The current control strategy of the World Health Organization is preventive chemotherapy (PC), i.e., the administration of the two benzimidazoles (albendazole and mebendazole) using single, oral doses to at risk populations without prior diagnosis. The recent success of PC is threatened by anthelmintic drug resistance and the low efficacy of the drugs against hookworm (mebendazole) and T. trichiura (albendazole and mebendazole). Only a handful of alternative drugs with anthelmintic properties are available, however, none of the drugs show high efficacy against all three STHs. The combination of two drugs with different activity profiles presents an attractive alternative, which could prevent the development of drug resistance and increase the efficacy compared to monotherapy. In this review, we summarize the efficacy of current and alternative anthelmintics, coadministrations and triple drug therapies assessed by means of network meta-analysis including only randomized controlled trials. Our results highlight that coadministrations have improved efficacy over monotherapy and the necessity of adapting current STH control strategies for the successful continuation of PC programs.

Haematophagic Caenorhabditis elegans

Caenorhabditis elegans is a free-living nematode that resides in soil and typically feeds on bacteria. We postulate that haematophagic C. elegans could provide a model to evaluate vaccine responses to intestinal proteins from hematophagous nematode parasites, such as Necator americanus. Human erythrocytes, fluorescently labelled with tetramethylrhodamine succinimidyl ester, demonstrated a stable bright emission and facilitated visualization of feeding events with fluorescent microscopy. C. elegans were observed feeding on erythrocytes and were shown to rupture red blood cells upon capture to release and ingest their contents. In addition, C. elegans survived equally on a diet of erythrocytes. There was no statistically significant difference in survival when compared with a diet of Escherichia coli OP50. The enzymes responsible for the digestion and detoxification of haem and haemoglobin, which are key components of the hookworm vaccine, were found in the C. elegans intestine. These findings support our postulate that free-living nematodes could provide a model for the assessment of neutralizing antibodies to current and future hematophagous parasite vaccine candidates.

in Manufahi District, Timor-Leste

Background

Soil-transmitted helminths (STHs) including Ascaris lumbricoides, Necator americanus, Ancylostoma spp. and Trichuris trichiura are cause of significant global morbidity. To mitigate their disease burden, at-risk groups in endemic regions receive periodic mass drug administration using anthelmintics, most commonly albendazole and mebendazole. Assessing the efficacy of anthelmintic drugs is important for confirming that these regimens are working effectively and that drug resistance has not emerged. In this study we aimed to characterise the therapeutic efficacy of albendazole against Ascaris spp. and N. americanus in Timor-Leste, using a quantitative polymerase chain reaction (qPCR) method for parasite detection and quantification.

Results

A total of 314 participants from 8 communities in Timor-Leste provided stool samples before and 10–14 days after the administration of a single 400 mg dose of albendazole. Helminth infection status and infection intensity (measured in Ct-values and relative fluorescence units) were determined using qPCR. Efficacy was determined by examining the cure rates and infection intensity reduction rates. Albendazole was found to be highly efficacious against Ascaris spp., with a cure rate of 91.4% (95% CI: 85.9–95.2%) and infection intensity reduction rate of 95.6% (95% CI: 88.3–100%). The drug was less efficacious against N. americanus with a cure rate of 58.3% (95% CI: 51.4–64.9%) and infection intensity reduction rate of 88.9% (95% CI: 84.0–97.0%).

Conclusions

The observed cure rates and infection intensity reduction rates obtained for Ascaris spp. and to a lower extent N. americanus, demonstrate the continued efficacy of albendazole against these species and its utility as a mass chemotherapy agent in Timor-Leste. Furthermore, this study demonstrates the usefulness of qPCR as a method to measure the efficacy of anthelminthic drugs. Additional research is necessary to translate Ct-values into eggs per gram in a systematic way.

Trial registration

Australian and New Zealand Clinical Trials Registry 12614000680662 (registered 27 June 2014).

[Differentiating the morphology of infective larvae between two human hookworms]

The morphological differentiation of the infective larvae between human Ancylostoma duodenale and Necator americanus is of great significance for the epidemiological survey of hookworm diseases and human parasitology teaching. Understanding of features of the oral spear and transverse lines on the tunica vaginalis is able to accurately differentiate the infective larvae between these two human hookworms.

Controlled Human Hookworm Infection: Accelerating Human Hookworm Vaccine Development

Background

Controlled human hookworm infection (CHHI) is a central component of a proposed hookworm vaccination-challenge model (HVCM) to test the efficacy of candidate vaccines. Critical to CHHI is the manufacture of Necator americanus infective larvae (NaL3) according to current Good Manufacturing Practice (cGMP) and the determination of an inoculum of NaL3 that is safe and reliably induces patent infection.

Methods

cGMP-grade NaL3 were produced for a phase 1 trial in 20 healthy, hookworm-naïve adults in the United States, who received either 25 or 50 NaL3. Participants were monitored for 12–18 weeks postinfection for safety, tolerability, and patency of N. americanus infection.

Results

Both NaL3 doses were well tolerated. Early manifestations of infection included pruritus, pain, and papulovesicular rash at the application site. Gastrointestinal symptoms and eosinophilia appeared after week 4 postinfection. The 50 NaL3 inoculum induced patent N. americanus infection in 90% of this dose group.

Conclusions

The inoculum of 50 NaL3 was well tolerated and consistently induced patent N. americanus infection suitable for future HVCM trials.

Clinical Trials Registration

NCT01940757.

Human dendritic cell sequestration onto the Necator americanus larval sheath during ex-sheathing: a possible mechanism for immune privilege

Despite the profound health implications of Necator americanus infection in humans, many aspects of its interaction with the host immune system are poorly understood. Here we investigated the early events at the interface of N. americanus larvae (L3) and human dendritic cells (DCs). Our data show that co-culturing DCs and the larvae trigger ex-sheathing of hookworms rapidly where a majority of DCs are sequestered onto the larval sheath allowing the ex-sheathed larvae to migrate away unchallenged. Intriguingly, DCs show negligible interaction with the ex-sheathed larvae, alluding to differences between the surface chemistry of the larva and its sheath. Furthermore, blocking of two key C-type lectin receptors on DC surface (i.e. DC-SIGN and mannose receptor) resulted in inhibition of ex-sheathing process and DC sequestration, highlighting the importance of C-type lectins on DCs in the induction of the ex-sheathing. Analyses of DC phenotype and cytokine profile after co-culture with the N. americanus larvae showed an immature phenotype as evidenced by the low expression of the maturation markers and cytokines. These data provide new insights into early events at the interface of human DCs and N. americanus larvae and could explain how L3 evade immune recognition upon initial interaction with DCs.

Hookworm Infection Caused Acute Intestinal Bleeding Diagnosed by Capsule: A Case Report and Literature Review

Hookworm infections are rare causes of acute gastrointestinal bleeding. We report a middle aged man with primary nephrotic syndrome and pulmonary embolism. During the treatment with steroids and anticoagulants, the patient presented acute massive hemorrhage of the gastrointestinal tract. The results of gastroscopy showed red worms in the duodenum. Colonoscopy and CT angiogram of abdomen were unremarkable. Capsule endoscopy revealed fresh blood and multiple hookworms in the jejunum and ileum. Hookworms caused the acute intestinal bleeding. The patient responded well to albendazole. Hematochezia was markedly ameliorated after eliminating the parasites. Hence, hookworm infection should be considered in the differential diagnosis of a patient with obscure gastrointestinal bleeding. Capsule endoscopy may offer a better means of diagnosis for intestinal hookworm infections.

Hookworm Infection: A Neglected Cause of Overt Obscure Gastrointestinal Bleeding

Hookworm infections are widely prevalent in tropical and subtropical areas, especially in low income regions. In the body, hookworms parasitize the proximal small intestine, leading to chronic intestinal hemorrhage and iron deficiency anemia. Occasionally, hookworms can cause overt gastrointestinal bleeding, but this is often ignored in heavily burdened individuals from endemic infectious areas. A total of 424 patients with overt obscure gastrointestinal bleeding were diagnosed by numerous blood tests or stool examinations as well as esophagogastroduodenoscopy, colonoscopy, capsule endoscopy or double-balloon enteroscopy. All of the patients lived in hookworm endemic areas and were not screened for hookworm infection using sensitive tests before the final diagnosis. The patients recovered after albendazole treatment, blood transfusion, and iron replacement, and none of the patients experienced recurrent bleeding in the follow-up. All the 31 patients were diagnosed with hookworm infections without other concomitant bleeding lesions, a rate of 7.3% (31/424). Seventeen out of 227 patients were diagnosed with hookworm infections in the capsule endoscopy (CE), and 14 out of 197 patients were diagnosed with hookworm infections in the double balloon enteroscopy (DBE). Hookworm infections can cause overt gastrointestinal bleeding and should be screened in patients with overt obscure gastrointestinal bleeding (OGIB) in endemic infectious areas with sensitive methods. Specifically, the examination of stool specimens is clinically warranted for most patients, and the proper examination for stool eggs relies on staff’s communication.

The role of ILC2 in hookworm infection

Hookworm is a major public health concern, yet still relatively little is known about the immunological responses involved in human infection. Animal studies are mainly confined to using the natural rodent helminth Nippostrongylus brasiliensis as this has been proposed as the most accurate model of hookworm infection in the mouse, with both its life cycle and the immune responses it invokes having been extremely well characterized. In this review, we examine the roles that type 2 innate lymphoid cells (ILC2s) play in immunity and host tolerance to hookworm infection, particularly N. brasiliensis. This includes their role in the initiation and regulation of immune responses, as well as in the resolution and limitation of tissue damage required after an infection with a large organism, such as a helminth.

Investigations into the association between soil-transmitted helminth infections, haemoglobin and child development indices in Manufahi District, Timor-Leste

BACKGROUND

Timor-Leste has a high prevalence of soil-transmitted helminth (STH) infections. High proportions of the population have been reported as being anaemic, and extremely high proportions of children as stunted or wasted. There have been no published analyses of the contributions of STH to these morbidity outcomes in Timor-Leste.

METHODS

Using baseline cross-sectional data from 24 communities (18 communities enrolled in a cluster randomised controlled trial, and identically-collected data from six additional communities), analyses of the association between STH infections and community haemoglobin and child development indices were undertaken. Stool samples were assessed for STH using qPCR and participant haemoglobin, heights and weights were measured. Questionnaires were administered to collect demographic and socioeconomic data. Intensity of infection was categorised using correlational analysis between qPCR quantification cycle values and eggs per gram of faeces equivalents, with algorithms generated from seeding experiments. Mixed-effects logistic and multinomial regression were used to assess the association between STH infection intensity classes and anaemia, and child stunting, wasting and underweight.

RESULTS

Very high stunting (60%), underweight (60%), and wasting (20%) in children, but low anaemia prevalence (15%), were found in the study communities. STH were not significantly associated with morbidity outcomes. Male children and those in the poorest socioeconomic quintile were significantly more likely to be moderately and severely stunted. Male children were significantly more likely than female children to be severely underweight. Increasing age was also a risk factor for being underweight. Few risk factors emerged for wasting in these analyses.

CONCLUSIONS

According to World Health Organization international reference standards, levels of child morbidity in this population constitute a public health emergency, although the international reference standards need to be critically evaluated for their applicability in Timor-Leste. Strategies to improve child development and morbidity outcomes, for example via nutrition and iron supplementation programmes, are recommended for these communities. Despite the apparent lack of an association from STH in driving anaemia, stunting, wasting and underweight, high endemicity suggests a need for STH control strategies.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry ACTRN12614000680662 ; retrospectively registered.

Prevalence and Molecular Aspects of Human Hookworms in Guilan Province, Northern Iran

BACKGROUND

Hookworm infection is one of the important Neglected Tropical Diseases (NTD) in the world. It was previously more prevalent in the northern and southern parts of Iran with a prevalence rate higher than 40% in some endemic regions; nevertheless, the infection rate has decreased to less than 1%. This study aimed to determine prevalence and molecular aspects of hookworm infections in rural inhabitants of Fouman County, Guilan Province, northern Iran.

METHODS

This cross-sectional study was performed in 31 villages of Fouman district in Guilan Province, northern Iran during 2015-2016. Stool samples were collected from 1500 rural inhabitants and examined by formalin ethyl-acetate concentration as well as agar plate culture techniques. After treatment with albendazole, adult hookworms were isolated. Following DNA extraction, PCR amplification of ITS2-rDNA region was performed and the product was sequenced, followed by genetic variation analysis.

RESULTS

Of 1500 samples, one case was morphologically diagnosed as N. americanus. In addition, molecular characterization verified the presence of N. americanus, showing more than 95% similarity with sequences of N. americanus present in GenBank. The patient showed no clinical symptoms and a mild hypereosinophilia was the only laboratory finding observed.

CONCLUSION

A reduced prevalence of human hookworms was demonstrated within Guilan Province located in north of Iran. The N. americanus originated from Guilan had a high homology with the isolates found in Japan, Laos, Malaysia, and Australia.

Water, sanitation and hygiene related risk factors for soil-transmitted helminth and Giardia duodenalis infections in rural communities in Timor-Leste

There is little evidence on prevalence or risk factors for soil transmitted helminth infections in Timor-Leste. This study describes the epidemiology, water, sanitation and hygiene, and socioeconomic risk factors of STH and intestinal protozoa amongst communities in Manufahi District, Timor-Leste. As part of a cluster randomised controlled trial, a baseline cross-sectional survey was conducted across 18 villages, with data from six additional villages. Stool samples were assessed for soil transmitted helminth and protozoal infections using quantitative PCR (qPCR) and questionnaires administered to collect water, sanitation and hygiene and socioeconomic data. Risk factors for infection were assessed using multivariable mixed-effects logistic regression, stratified by age group (preschool, school-aged and adult). Overall, soil transmitted helminth prevalence was 69% (95% Confidence Interval 67-71%), with Necator americanus being most common (60%; 95% Confidence Interval 58-62%) followed by Ascaris spp. (24%; 95% Confidence Interval 23-26%). Ascaris-N. americanus co-infection was common (17%; 95% Confidence Interval 15%-18%). Giardia duodenalis was the main protozoan identified (13%; 95% Confidence Interval 11-14%). Baseline water, sanitation and hygiene infrastructure and behaviours were poor. Although risk factors varied by age of participants and parasite species, risk factors for N. americanus infection included, generally, age in years, male sex, and socioeconomic quintile. Risk factors for Ascaris included age in years for children, and piped water to the yard for adults. In this first known assessment of community-based prevalence and associated risk factors in Timor-Leste, soil transmitted helminth infections were highly prevalent, indicating a need for soil transmitted helminth control. Few associations with water, sanitation and hygiene were evident, despite water, sanitation and hygiene being generally poor. In our water, sanitation and hygiene we will investigate implications of improving WASH on soil transmitted helminth infection in impoverished communities.

Isolation, characterization, and anthelminthic activities of a novel dichapetalin and other constituents of Dichapetalum filicaule

CONTEXT

Dichapetalum filicaule Breteler (Dichapetalaceae) is a rare species occurring only in Côte d'Ivoire and Ghana. Although research on several species of the genus has produced interesting bioactive compounds, particularly the Dichapetalins, a novel class of triterpenoids with antineoplastic properties, there is virtually no information on the ethnobotanical uses and chemical constituents of D. filicaule.

OBJECTIVE

The phytochemical and anthelminthic activities of the constituents of D. filicaule were investigated.

MATERIALS AND METHODS

Chemical constituents of the petroleum ether, chloroform-acetone, and methanol root extracts of D. filicaule were isolated by column chromatography and characterized by their physico-chemical properties, 1-D and 2-D NMR spectroscopy and mass spectrometry. In vitro anthelminthic activity of the extracts and compounds against the human hookworm, Necator americanus, Stiles 1902 (Nematoda: Ancylostomatidae) was determined within a concentration range of 2500-250 μg/ml using the Egg Hatch Inhibition (EHI) Assay. The hookworm species were identified using a published polymerase chain reaction (PCR) method.

RESULTS

A new dichapetalin, dichapetalin X (1), together with the known dichapetalin A (2), pomolic acid (3), glycerol monostearate (4), D:A-friedooleanan-3β-ol (5), and D:A-friedooleanan-3-one (6) were isolated. Compounds 1, 2, and 4 exhibited EHI with IC50 values of 523.2, 162.4, and 306.0 μg/ml, respectively, against the hookworm. The positive control albendazole gave an IC50 value of 93.27 μg/ml.

DISCUSSION AND CONCLUSION

This is the first report of the phytochemical investigation of D. filicaule. The study has yielded a new dichapetalin and also demonstrated the potential anthelminthic properties of the constituents.

Restoration of hookworm egg development after prolonged storage in stool suspension

Hookworm infection is still prevalent in southern Thailand despite control measures. Hookworm eggs submerged for an extended period under water from rainfall or in latrines may not survive, but they may recover their ability to develop into infective larvae when exposed to atmospheric air. This study examined the survival of the hookworm eggs in stool suspension and the restoration of development capability after prolonged storage. In stool mass, eggs developed normally and yielded infective filariform larvae (FL) in 7 days. On the contrary, in 1:10 stool suspension, hookworm eggs were found to remain at the 4-8 cell stage; degenerated eggs were observed after 15 days of storage, and the number of degenerated eggs reached 80 % on day 30. Aeration of the suspension, or transferring to a Petri dish or agar plate, restored the capacity of eggs stored for up to 15 days to develop into FL; thereafter, the capacity declined sharply. Retardation of egg development under water or in stool suspension may be due to a lack of atmospheric air. Use of "night soil" from latrines as fertilizer may be one factor in maintaining hookworm transmission, as worm eggs can undergo normal development upon exposure to atmospheric air.

Diversity in the structures and ligand-binding sites of nematode fatty acid and retinol-binding proteins revealed by Na-FAR-1 from Necator americanus

Fatty acid and retinol-binding proteins (FARs) comprise a family of unusual α-helix rich lipid-binding proteins found exclusively in nematodes. They are secreted into host tissues by parasites of plants, animals and humans. The structure of a FAR protein from the free-living nematode Caenorhabditis elegans is available, but this protein [C. elegans FAR-7 (Ce-FAR-7)] is from a subfamily of FARs that does not appear to be important at the host/parasite interface. We have therefore examined [Necator americanus FAR-1 (Na-FAR-1)] from the blood-feeding intestinal parasite of humans, N. americanus. The 3D structure of Na-FAR-1 in its ligand-free and ligand-bound forms, determined by NMR (nuclear magnetic resonance) spectroscopy and X-ray crystallography respectively, reveals an α-helical fold similar to Ce-FAR-7, but Na-FAR-1 possesses a larger and more complex internal ligand-binding cavity and an additional C-terminal α-helix. Titration of apo-Na-FAR-1 with oleic acid, analysed by NMR chemical shift perturbation, reveals that at least four distinct protein-ligand complexes can be formed. Na-FAR-1 and possibly other FARs may have a wider repertoire for hydrophobic ligand binding, as confirmed in the present study by our finding that a range of neutral and polar lipids co-purify with the bacterially expressed recombinant protein. Finally, we show by immunohistochemistry that Na-FAR-1 is present in adult worms with a tissue distribution indicative of possible roles in nutrient acquisition by the parasite and in reproduction in the male.

Optimization and revision of the production process of the Necator americanus glutathione S-transferase 1 (Na-GST-1), the lead hookworm vaccine recombinant protein candidate

Infection by the human hookworm Necator americanus is a leading cause of anemia and disability in the developing countries of Africa, Asia, and the Americas. In order to prevent childhood hookworm disease in resource poor settings, a recombinant vaccine is under development by the Sabin Vaccine Institute and Texas Children’s Hospital Center for Vaccine Development, a Product Development Partnership (PDP). Previously, we reported on the expression and purification of a highly promising hookworm vaccine candidate, Na-GST-1, an N. americanus glutathione s-transferase expressed in Pichia pastoris (yeast), which led to production of 1.5 g of 95% pure recombinant protein at a 20L scale.^{1, 2, 3} This yield and purity of Na-GST-1 was sufficient for early pilot manufacturing and initial phase 1 clinical testing. However, based on the number of doses which would be required to allow mass vaccination and a potential goal to deliver a vaccine as inexpensively as possible, a higher yield of expression of the recombinant antigen at the lowest possible cost is highly desirable. Here we report on modifications to the fermentation (upstream process) of the antigen expressed in P. pastoris, and to the purification (downstream process) of the recombinant protein that allowed for a 2–3-fold improvement in the final yield of Na-GST-1 purified protein. The major improvements included upstream process changes such as the addition of a sorbitol pulse and co-feed during methanol induction as well as an extension of the induction stage to approximately 96 hours; downstream process changes included modifying the UFDF to flat sheet with a 10 kDa Molecular Weight cut-off (MWCO), adjusting the capacity of an ion-exchange chromatography step utilizing a gradient elution as opposed to the original step elution, and altering the hydrophobic interaction chromatography conditions. The full process, as well as the purity and stability profiles of the target Na-GST-1, and its formulation on Alhydrogel^®, is described.

Celiac disease 2015 update: new therapies

Celiac disease (CD) is a chronic, small intestinal, immune-mediated enteropathy triggered by exposure to dietary gluten in genetically susceptible individuals. Currently, lifelong adherence to a gluten-free diet (GFD) is the only available treatment. However, GFD alone is not sufficient to relieve symptoms, control small intestinal inflammation and prevent long-term complications in many patients. The GFD has its challenges including issues related to adherence, lifestyle restrictions and cost. As a result, there is growing interest in and a need for non-dietary therapies to manage this condition. In recent years, different targets in the immune-mediated cascade of CD have been identified in clinical and pre-clinical trials for potential therapies. This review will discuss the latest non-dietary therapies in CD, including endopeptidases, modulators of enterocyte tight junctions and agents involved in gluten tolerization and immunomodulation. We will also discuss the potential implications of approved therapeutics on CD clinical practice.

New tools for NTD vaccines: A case study of quality control assays for product development of the human hookworm vaccine Na-APR-1M74

Na-APR-1(M74) is an aspartic protease that is rendered enzymatically inactive by site-directed mutagenesis and is a candidate antigen component in the Human Hookworm Vaccine. The mutant protease exerts vaccine efficacy by inducing antibodies that neutralize the enzymatic activity of wild type enzyme (Na-APR-1wt) in the gut of the hookworm, thereby depriving the worm of its ability to digest its blood meal. Previously, canines immunized with Na-APR-1(M74) and challenged with Ancylostoma caninum were partially protected against hookworm challenge infection, especially from the loss in hemoglobin observed in control canines and canine immunoglobulin (Ig) G raised against Na-APR-1 was shown to inhibit the enzymatic activity of Na-APR-1 wt in vitro, thereby providing proof of concept of Na-APR-1(M74) as a vaccine antigen. The mutated version, Na-APR-1(M74), was then expressed at the cGMP level using a Nicotiana benthamiana expression system (Fraunhofer, CMB, Delaware, MD), formulated with Alhydrogel®, and used to immunize mice in a dose-ranging study to explore the enzyme-neutralizing capacity of the resulting anti- Na-APR-1(M74) IgG. As little as 0.99 μg of recombinant Na-APR-1(M74) could induce anti Na-APR-1(M74) IgG in mice that were capable of inhibiting Na-APR-1w t-mediated digestion of a peptide substrate by 89%. In the absence of enzymatic activity of Na-APR-1(M74) as a surrogate marker of protein functionality, we developed an assay based on the binding of a quenched fluorescence-labeled inhibitor of aspartic proteases, BODIPY-FL pepstatin A (BDP). Binding of BDP in the active site of Na-APR-1 wt was demonstrated by inhibition of enzymatic activity, and competitive binding with unlabelled pepstatin A. BDP also bound to Na-APR-1(M74) which was assessed by fluorescence polarization, but with an ∼ 50-fold reduction in the dissociation constant. Taken together, these assays comprise a "toolbox" that could be useful for the analyses of Na-APR-1(M74) as it proceeds through the clinical development as part of the Human Hookworm Vaccine pipeline.

Structure of glutathione S-transferase 1 from the major human hookworm parasite Necator americanus (Na-GST-1) in complex with glutathione

Glutathione S-transferase 1 from Necator americanus (Na-GST-1) is a vaccine candidate for hookworm infection that has a high affinity for heme and metal porphyrins. As part of attempts to clarify the mechanism of heme detoxification by hookworm GSTs, co-crystallization and soaking studies of Na-GST-1 with the heme-like molecules protoporphyrin IX disodium salt, hematin and zinc protoporphyrin were undertaken. While these studies did not yield the structure of the complex of Na-GST-1 with any of these molecules, co-crystallization experiments resulted in the first structures of the complex of Na-GST-1 with the substrate glutathione. The structures of the complex of Na-GST-1 with glutathione were solved from pathological crystalline aggregates comprising more than one crystal form. These first structures of the complex of Na-GST-1 with the substrate glutathione were solved by molecular replacement from data collected with a sealed-tube home source using the previously reported apo structure as the search model.

Probing of a human proteome microarray with a recombinant pathogen protein reveals a novel mechanism by which hookworms suppress B-cell receptor signaling

Na-ASP-2 is an efficacious hookworm vaccine antigen. However, despite elucidation of its crystal structure and studies addressing its immunobiology, the function of Na-ASP-2 has remained elusive. We probed a 9000-protein human proteome microarray with Na-ASP-2 and showed binding to CD79A, a component of the B-cell antigen receptor complex. Na-ASP-2 bound to human B lymphocytes ex vivo and downregulated the transcription of approximately 1000 B-cell messenger RNAs (mRNAs), while only approximately 100 mRNAs were upregulated, compared with control-treated cells. The expression of a range of molecules was affected by Na-ASP-2, including factors involved in leukocyte transendothelial migration pathways and the B-cell signaling receptor pathway. Of note was the downregulated transcription of lyn and pi3k, molecules that are known to interact with CD79A and control B-cell receptor signaling processes. Together, these results highlight a previously unknown interaction between a hookworm-secreted protein and B cells, which has implications for helminth-driven immunomodulation and vaccine development. Further, the novel use of human protein microarrays to identify host-pathogen interactions, coupled with ex vivo binding studies and subsequent analyses of global gene expression in human host cells, demonstrates a new pipeline by which to explore the molecular basis of infectious diseases.

Molecular detection of Ancylostoma duodenale, Ancylostoma ceylanicum, and Necator americanus in humans in northeastern and southern Thailand

The 2 principal species of hookworms infecting humans are Necator americanus and Ancylostoma duodenale. Case studies on zoonotic hookworm infections with Ancylostoma ceylanicum and/or Ancylostoma caninum are known mainly from Asian countries. Of these 2 zoonotic species, only A. ceylanicum can develop to adulthood in humans. In the present study, we report a molecular-based survey of human hookworm infections present in southern and northeastern Thailand. Thirty larval hookworm samples were obtained from fecal agar plate cultures of 10 patients in northeastren Thailand and 20 in southern Thailand. Partial ITS1, 5.8S, and ITS2 regions of the ribosomal DNA genes were amplified using PCR. The amplicons were sequenced, aligned, and compared with other hookworm sequences in GenBank database. The results showed that, in Thailand, N. americanus is more prevalent than Ancylostoma spp. and is found in both study areas. Sporadic cases of A. ceylanicum and A. duodenale infection were seen in northeastern Thailand.

Structure of monomeric Na-GST-3, a glutathione S-transferase from the major human hookworm parasite Necator americanus

Necator americanus is the major cause of human hookworm infection, which is a global cause of anemia in the developing world. Ongoing efforts to control hookworm infection include the identification of candidate vaccine antigens as well as potential therapeutic targets from the infective L3 larval stages and adult stages of the parasite. One promising family of proteins are the adult-stage-secreted cytosolic glutathione S-transferases (GSTs). Nematode GSTs facilitate the inactivation and degradation of a variety of electrophilic substrates (drugs) via the nucleophilic addition of reduced glutathione. Parasite GSTs also play significant roles in multi-drug resistance and the modulation of host immune defense mechanisms. Here, the structure of Na-GST-3, one of three GSTs secreted by adult-stage N. americanus, is reported. Unlike most GST structures, the Na-GST-3 crystal contains a monomer in the asymmetric unit. However, the monomer forms a prototypical GST dimer across the crystallographic twofold. A glutathione from the fermentation process is bound to the monomer. The overall binding cavity of Na-GST-3 is reminiscent of that of other N. americanus GSTs and is larger and capable of binding a wider array of ligands than GSTs from organisms that have other major detoxifying mechanisms. Furthermore, despite having low sequence identity to the host GST, Na-GST-3 has a greater tertiary-structure similarity to human sigma-class GST than was observed for the other N. americanus GSTs.

A case of severe anemia by Necator americanus infection in Korea

This report describes clinical and parasitological findings of an 82-yr-old female patient who lived in a local rural village and suffered from severe chronic anemia for several years. She was transferred to the National Police Hospital in Seoul for management of severe dyspnea and dizziness. At admission, she showed symptoms or signs of severe anemia. Gastroduodenoscopy observed hyperemic mucosa of the duodenum and discovered numerous moving roundworms on the mucosa. Endoscopy isolated seven of them, which were identified as Necator americanus by characteristic morphology of cutting plates in the buccal cavity. The patient was treated with albendazole and supportive measures for anemia, and her physical condition much improved. This case suggests the possibility that hookworm N. americanus is still transmitted in a remote local mountainous area in Korea.