Identifying thresholds for classifying moderate-to-heavy soil-transmitted helminth intensity infections for FECPAKG2, McMaster, Mini-FLOTAC and qPCR

The World Health Organization (WHO) has defined moderate-to-heavy intensity (M&HI) infections with soil-transmitted helminths (Ascaris lumbricoides, Trichuris trichiura and the two hookworms, Ancylostoma duodenale and Necator americanus) based on specific values of eggs per gram of stool, as measured by the Kato-Katz method. There are a variety of novel microscopy and DNA-based methods but it remains unclear whether applying current WHO thresholds on to these methods allows for a reliable classification of M&HI infections. We evaluated both WHO and method-specific thresholds for classifying the M&HI infections for novel microscopic (FECPAKG2, McMaster and Mini-FLOTAC) and DNA-based (qPCR) diagnostic methods. For this, we determined method-specific thresholds that best classified M&HI infections (defined by Kato-Katz and WHO thresholds; reference method) in two multi-country drug efficacy studies. Subsequently, we verified whether applying these method-specific thresholds improved the agreement in classifying M&HI infections compared to the reference method. When we applied the WHO thresholds, the new microscopic methods mainly misclassified M&HI as low intensity, and to a lesser extent low intensity infection as M&HI. For FECPAKG2, applying the method-specific thresholds significantly improved the agreement for Ascaris (moderate → substantial), Trichuris and hookworms (fair → moderate). For Mini-FLOTAC, a significantly improved agreement was observed for hookworms only (fair → moderate). For the other STHs, the agreement was almost perfect and remained unchanged. For McMaster, the method-specific thresholds revealed a fair to a substantial agreement but did not significantly improve the agreement. For qPCR, the method-specific thresholds based on genome equivalents per ml of DNA moderately agreed with the reference method for hookworm and Trichuris infections. For Ascaris, there was a substantial agreement. We defined method-specific thresholds that improved the classification of M&HI infections. Validation studies are required before they can be recommended for general use in assessing M&HI infections in programmatic settings.

The Right Tool for the Job: Detection of Soil-Transmitted Helminths in Areas Co-endemic for Other Helminths

Background

Due to the recent increased use of the McMaster (MM) fecal egg counting method for assessing benzimidazole drug efficacy for treating soil-transmitted helminth (STH) infections, the aim of the current study was to determine the operational value of including the MM method alongside the Kato-Katz (KK) fecal thick smear to increase the diagnostic sensitivity when STHs are co-endemic with trematode helminths (e.g., Schistosoma mansoni).

Methods

A cross-sectional study was conducted in school-aged children aged 4-18 years in the northeastern region of the State of Minas Gerais (Brazil), where Necator americanus, Ascaris lumbricoides, Trichuris trichiura, and S. mansoni are co-endemic. One fecal sample from each participant was collected and transported to the field laboratory for analysis. Coprological diagnosis was performed on each fecal sample by three different methods: Formalin-Ether Sedimentation (FES), KK and the MM technique. The diagnostic sensitivity and negative predictive value (NPV) of each technique was calculated using the combination of all three techniques as the composite standard. In order to determine the agreement between the three techniques Fleiss´ kappa was used. Both the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) were calculated using the two quantification techniques (i.e., the MM and KK).

Results

Fecal samples from 1260 children were analyzed. The KK had higher diagnostic sensitivity than the MM for the detection of both A. lumbricoides (KK 97.3%, MM 69.5%) and hookworm (KK 95.1%, MM 80.8%). The CR of a single dose of mebendazole varied significantly between the KK and MM for both A. lumbricoides (p = 0.016) and hookworm (p = 0.000), with lower rates obtained with the KK. On the other hand, the FECR was very similar between both techniques for both A. lumbricoides and hookworm.

Conclusion

The MM did not add any diagnostic value over the KK in areas where both STHs and trematodes were co-endemic. The lower sensitivity of the MM would have an important impact on the administration of selective school-based treatment in this area since if only the MM were used, 36 (13.9%) children diagnosed with A. lumbricoides would have gone untreated.

Diagnosis of intestinal helminths and Schistosoma mansoni infections is based on the detection of eggs in feces. There are many techniques available for both detection and quantification of infection. For the quantification of helminth infections, the methods traditionally used are the Kato-Katz (KK) fecal think smear in humans, and the McMaster (MM) counting method in animals. Recently, the MM has been used for assessing the efficacy of benzimidazole drugs for treating soil-transmitted helminth (STH) infections in humans. In most parts of the world, however, STHs occur simultaneously with other helminth species, and the MM does not detect other helminth eggs. Therefore, in this study we sought to determine if the use of the MM in an area of Brazil were both STHs and S. mansoni are co-endemic, added any value to the current standard of diagnosis using the KK.

Immunology of experimental and natural human hookworm infection

Human hookworm infection is one amongst the most prevalent of the neglected tropical diseases. An informative experimental animal model, that is, one that parallels a human infection, is not available for the study of human hookworm infection. Much of our current understanding of the human immune response during hookworm infection relies on the studies from experimental infection of hookworm-naïve individuals or the natural infections from individuals residing in hookworm-endemic areas. The experimental human infections tend to be acute, dose-controlled infections, often with a low larval inoculum so that they are well tolerated by human volunteers. Natural hookworm infections usually occur in areas where hookworm transmission is constant and infection is chronic. In cases where there has been drug administration in an endemic area, re-infection often occurs quickly even amongst those who were treated. Hence, although many of the characteristics of experimental and natural hookworm infection differ, both models have elements in common: mainly an intense Th2 response with the production of total and specific IgE as well as elevated levels of eosinophilia, IL-5, IL-10 and TNF. While hookworm infection affects millions of individuals worldwide, much of the human immunology of this infection still needs to be studied and understood.

Assessment of anthelmintic efficacy of mebendazole in school children in six countries where soil-transmitted helminths are endemic

Background

Robust reference values for fecal egg count reduction (FECR) rates of the most widely used anthelmintic drugs in preventive chemotherapy (PC) programs for controlling soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura, and hookworm) are still lacking. However, they are urgently needed to ensure detection of reduced efficacies that are predicted to occur due to growing drug pressure. Here, using a standardized methodology, we assessed the FECR rate of a single oral dose of mebendazole (MEB; 500 mg) against STHs in six trials in school children in different locations around the world. Our results are compared with those previously obtained for similarly conducted trials of a single oral dose of albendazole (ALB; 400 mg).

Methodology

The efficacy of MEB, as assessed by FECR, was determined in six trials involving 5,830 school children in Brazil, Cambodia, Cameroon, Ethiopia, United Republic of Tanzania, and Vietnam. The efficacy of MEB was compared to that of ALB as previously assessed in 8,841 school children in India and all the above-mentioned study sites, using identical methodologies.

Principal Findings

The estimated FECR rate [95% confidence interval] of MEB was highest for A. lumbricoides (97.6% [95.8; 99.5]), followed by hookworm (79.6% [71.0; 88.3]). For T. trichiura, the estimated FECR rate was 63.1% [51.6; 74.6]. Compared to MEB, ALB was significantly more efficacious against hookworm (96.2% [91.1; 100], p<0.001) and only marginally, although significantly, better against A. lumbricoides infections (99.9% [99.0; 100], p = 0.012), but equally efficacious for T. trichiura infections (64.5% [44.4; 84.7], p = 0.906).

Conclusions/Significance

A minimum FECR rate of 95% for A. lumbricoides, 70% for hookworm, and 50% for T. trichiura is expected in MEB-dependent PC programs. Lower FECR results may indicate the development of potential drug resistance.

Soil-transmitted helminths (STHs; roundworms, whipworms, and hookworms) infect millions of children in sub-tropical and tropical countries, resulting in malnutrition, growth stunting, intellectual retardation, and cognitive deficits. To fight against STH, large-scale deworming programs are implemented in which anthelmintic drugs (either albendazole (ALB) or mebendazole (MEB)) are administered. Currently, these large-scale programs are intensifying, highlighting the need to closely monitor the efficacy of anthelmintic drugs to detect changes in drug efficacy that may arise through the evolution of anthelmintic drug resistance in the parasites. We have previously defined the minimum expected efficacy of ALB based on the fecal egg count reduction (FECR) rate, but these reference values are lacking for MEB. Therefore, we therefore evaluated the FECR rate of MEB against STHs in six STH endemic countries. In addition, we compared the results of the FECR rate for MEB with those we obtained previously for ALB. The results confirm that MEB treatment was highly efficacious against roundworms, and to a lesser extend against hookworms, but not against whipworms. Compared to ALB, MEB is less efficacious against hookworm, but equally efficacious against roundworms and whipworms. Based on this study we propose the minimum expected FECR rate for MEB-dependent large-scale deworming programs.

Endemic Burkitt lymphoma is associated with strength and diversity of Plasmodium falciparum malaria stage-specific antigen antibody response

Endemic Burkitt lymphoma (eBL) is linked to Plasmodium falciparum (Pf) infection geographically, but evidence from individual-level studies is limited. We investigated this issue among 354 childhood eBL cases and 384 age-, sex-, and location-matched controls enrolled in Ghana from 1965 to 1994. Immunoglobulin G1 (IgG1) and immunoglobulin G3 (IgG3) antibodies to antigens diagnostic of recent infection Pf histidine-rich protein-II (HRP-II) and 6NANP, Pf-vaccine candidates SE36 and 42-kDa region of the 3D7 Pf merozoite surface protein-1 (MSP-1), and tetanus toxoid were measured by indirect enzyme-linked immunoassay. Odds ratios (ORs) and 95% confidence intervals (CIs) for association with eBL were estimated using unconditional logistic regression. After adjustments, eBL was positively associated with HRP-IIIgG3 seropositivity (adjusted OR: 1.60; 95% CI 1.08-2.36) and inversely associated with SE36IgG1 seropositivity (adjusted OR: 0.37; 95% CI 0.21-0.64) and with tetanus toxoidIgG3 levels equal or higher than the mean (adjusted OR: 0.46; 95% CI 0.32-0.66). Anti-MSP-1IgG3 and anti-6NANPIgG3 were indeterminate. eBL risk was potentially 21 times higher (95% CI 5.8-74) in HRP-IIIgG3-seropositive and SE36IgG1-seronegative responders compared with HRP-IIIgG3-seronegative and SE36IgG1-seropositive responders. Our results suggest that recent malaria may be associated with risk of eBL but long-term infection may be protective.

Inflammatory response to liver fluke Opisthorchis viverrini in mice depends on host master coregulator MTA1, a marker for parasite-induced cholangiocarcinoma in humans

Based on the recently established role for the master coregulator MTA1 and MTA1-containing nuclear remodeling complexes in oncogenesis and inflammation, we explored the links between parasitism by the carcinogenic liver fluke Opisthorchis viverrini and this coregulator using both an Mta1(-/-) mouse model of infection and a tissue microarray of liver fluke-induced human cholangiocarcinomas (CCAs). Intense foci of inflammation and periductal fibrosis in the liver and kidneys of wild-type Mta1(+/+) mice were evident at 23 days postinfection with O. viverrini. In contrast, little inflammatory response was observed in the same organs of infected Mta1(-/-) mice. Livers of infected Mta1(+/+) mice revealed strong up-regulation of fibrosis-associated markers such as cytokeratins 18 and 19 and annexin 2, as determined both by immunostaining and by reverse-transcription polymerase chain reaction compared with infected Mta1(-/-) mice. CD4 expression was up-regulated by infection in the livers of both experimental groups; however, its levels were several-fold higher in the Mta1(+/+) mice than in infected Mta1(-/-) mice. Mta1(-/-) infected mice also exhibited significantly higher systemic and hepatic levels of host cytokines such as interleukin (IL)-12p70, IL-10, and interferon-γ compared with the levels of these cytokines in the Mta1(+/+) mice, suggesting an essential role of MTA1 in the cross-regulation of the Th1 and Th2 responses, presumably due to chromatin remodeling of the target chromatin genes. Immunohistochemical analysis of ≈ 300 liver tissue cores from confirmed cases of O. viverrini-induced CCA showed that MTA1 expression was elevated in >80% of the specimens.

CONCLUSION

These findings suggest that MTA1 status plays an important role in conferring an optimal cytokine response in mice following infection with O. viverrini and is a major player in parasite-induced CCA in humans.

The metastasis-associated protein-1 gene encodes a host permissive factor for schistosomiasis, a leading global cause of inflammation and cancer

Schistosoma haematobium is responsible for two-thirds of the world's 200 million to 400 million cases of human schistosomiasis. It is a group 1 carcinogen and a leading cause of bladder cancer that occurs after years of chronic inflammation, fibrosis, and hyperproliferation in the host liver. The coevolution of blood flukes of the genus Schistosoma and their human hosts is paradigmatic of long-term parasite development, survival, and maintenance in mammals. However, the contribution of host genes, especially those discrete from the immune system, necessary for parasite establishment and development remains poorly understood. This study investigated the role of metastasis-associated protein-1 gene (Mta1) product in the survival of S. haematobium and productive infection in the host. Using a Mta-1 null mouse model, here we provide genetic evidence to suggest that MTA1 expression positively influences survival and/or maturation of schistosomes in the host to patency, as we reproducibly recovered significantly fewer S. haematobium worms and eggs from Mta1-/- mice than wild-type mice. In addition, we found a distinct loss of cytokine interdependence and aberrant Th1 and Th2 cytokine responses in the Mta1-/- mice compared to age-matched wild-type mice. Thus, utilizing this Mta1-null mouse model, we identified a distinct contribution of the mammalian MTA1 in establishing a productive host-parasite interaction and thus revealed a host factor critical for the optimal survival of schistosomes and successful parasitism. Moreover, MTA1 appears to play a significant role in driving inflammatory responses to schistosome egg-induced hepatic granulomata reactions, and thus offers a survival cue for parasitism as well as an obligatory contribution of liver in schistosomiasis.

CONCLUSION

These findings raise the possibility to develop intervention strategies targeting MTA1 to reduce the global burden of schistosomiasis, inflammation, and neoplasia.

Potency testing for the experimental Na-GST-1 hookworm vaccine

Over the next decade, a new generation of vaccines will target the neglected tropical diseases (NTDs). The goal of most NTD vaccines will be to reduce the morbidity and decrease the chronic debilitating nature of these often-forgotten infections &#x2013; outcomes that are hard to measure in the traditional potency testing paradigm. The absence of measurable correlates of protection, a lack of permissive animal models for lethal infection, and a lack of clinical indications that do not include the induction of sterilizing immunity required us to reconsider the traditional bioassay methods for determining vaccine potency. Owing to these limitations, potency assay design for NTD vaccines will increasingly rely on a paradigm where potency testing is one among many tools to ensure that a manufacturing process yields a product of consistent quality. Herein, we discuss the evolution of our thinking regarding the design of a potency assay along these newly defined lines and its application to the release of the experimental Necator americanus-glutathione-S- transferase-1 (Na-GST-1) vaccine to prevent human hookworm infection. We discuss the necessary steps to accomplish the design and implementation of such a new potency assay as a resource for the burgeoning NTD vaccine community. Our experience is that much of the existing information is proprietary and needs to be pulled together in a single source to aid in our overall understanding of potency testing.

Identification of genotypes of Giardia intestinalis of human isolates in Egypt

In Egypt, the genotyping study of Giardia intestinalis in human is limited. To determine the prevalence of G. intestinalis, faecal samples were collected from Egypt. Samples were concentrated using density gradient centrifugation. The samples were subjected to PCR and DNA sequence analysis for TPI gene. Prevalence of Giardia infection was 34.6% of 52 examined. DNA sequence showed that the Assemblage B was the most prevalent (80%) genotype, the 15% of the positive samples belonged to Assemblage E, and the 5% of them belonged to Assemblage A. Certainly, both genotypes A and B are highly common in human worldwide. However, up to now, Assemblage E had not been known to be infectious for humans. Therefore, this is the first time that Assemblage E is reported in human. However, further analyses of a second locus are required to confirm this result. The extent to which Giardia-infected cattle in Egypt might pose a risk of human infection is unknown.

Phenotypic analysis of adults of Fasciola hepatica, Fasciola gigantica and intermediate forms from the endemic region of Gilan, Iran

Fascioliasis is an important human and animal disease caused by Fasciola hepatica and Fasciola gigantica. In Iran, the distribution of these two species overlaps in most areas, including the northern human endemic province of Gilan where both fasciolids are simultaneously found in individual cattle and buffaloes. A phenotypic study of fasciolid adult flukes from naturally infected bovines from Gilan was carried out by means of an exhaustive morphometric analysis using traditional microscopic measurements and an allometric model. The Iranian fasciolids were compared to F. hepatica and F. gigantica standard populations, i.e. from geographical areas where both species do not co-exist (Bolivia and Burkina Faso, respectively). Although morphometric values somewhat overlapped, there were clear differences in allometric growth. The allometric function was adjusted to 25 pairs of variables. Results obtained revealed that Iranian F. hepatica-like specimens are larger than the F. hepatica standard and Iranian F. gigantica-like specimens are longer and narrower than the F. gigantica standard, but with smaller body area. Measurements which permit a specific differentiation in allopatric populations (distance between ventral sucker and posterior end of the body; ratio between body length and body width) overlap in the specimens from Gilan, thus proving the presence of intermediate forms. When compared to the standard populations, the different Iranian fasciolid morphs show greater differences in F. gigantica-like specimens than in F. hepatica-like specimens. This study shows that simple, traditional microscopic measurements may be sufficient for the morphometric characterisation of fasciolids, even in areas where intermediate forms are present.

Crowding effect on adult growth, pre-patent period and egg shedding of Fasciola hepatica

Fascioliasis pathogenesis depends on fluke burden. In human hyperendemic zones, individual infection intensities reach very high levels and the majority of infected subjects should be in the advanced chronic phase. The rat model offers a useful approach for pathological research in the advanced chronic period. The influence of infection intensity per rat on fluke development, pre-patent period and egg shedding (eggs/g faeces/worm) was analysed in 3 groups (I: 1–3 worms/rat; II: 4–6; III: 7–9). Ontogenetic trajectories of fluke body measures followed a logistic model. Results showed that when the burden increases, the maximum values of fluke measures decrease. The crowding effect is manifest when fluke measures approximate their maximums in the advanced chronic stage. The pre-patent period and egg production decrease when the burden increases. This means that measurements of eggs per gramme of faeces tend to underestimate the fluke burden. The present study demonstrates how to quantify the fascioliasis experimental rat model crowding effect on adult growth, pre-patent period and egg production. This quantification may be of great interest in epidemiological studies and in experimental research on the in vivo actions of different anthelminthic drugs and vaccines, pathology, immunology and resistance studies.

Phenotypic comparison of allopatric populations of Fasciola hepatica and Fasciola gigantica from European and African bovines using a computer image analysis system (CIAS)

The quantification of the different sizes and shapes of Fasciola hepatica and Fasciola gigantica from bovines has been achieved for the first time in natural allopatric populations. Linear measurements, areas and ratios of gravid adults and eggs of F. hepatica (from France and Spain) and F. gigantica (from Burkina Faso) were analysed using a computer image analysis system and an allometric model: (y2m - y2)/y2 = c[(y1m - y1)/y1](b), where y1 = body area or body length, y2 = one of the measurements analysed, y1m, y2m = maximum values towards which y1 and y2, respectively, tend and c, b = constants. All the measurements overlap in the two fasciolids, apart from the distance between the ventral sucker and the posterior end of the body, body roundness and body length/body width ratio. The results obtained may be useful in Fasciola species identification in countries where both species coexist.

Human and animal fascioliasis in Mazandaran province, northern Iran

The fascioliasis situation in humans and livestock of Iranian Mazandaran is analysed for the first time. Coprological studies showed 7.3% and 25.4% global prevalences in sheep and cattle, respectively. Studies in slaughterhouses indicate that sheep and cattle may be the main reservoir species, buffaloes may play local roles in the transmission, and goats and horses probably only participate sporadically. Morphometric studies by computer image analysis showed that forms intermediate between Fasciola hepatica and F. gigantica appear in addition to both species. A total of 107 infected humans were diagnosed during the 1999-2002 period, which suggests that fascioliasis may be widespread. The absence of differences in human fascioliasis among gender and age groups differs from other human endemic areas. Both human and animal infections show marked differences between western and eastern Mazandaran. Traditions in herbal condiments for human consumption, methods of animal husbandry and annual rainfall may explain the higher prevalences in western Mazandaran.

Differential sensitivity of Chinese hamster V79 and Chinese hamster ovary (CHO) cells in the in vitro micronucleus screening assay

Both the V79 and CHO cell lines are routinely used in the in vitro MN screening assay for the detection of possible genotoxicants. The CHO cell line is the predominant cell line currently used in the genetic toxicology testing industry. However, some laboratories routinely utilize the V79 cell line since the in vitro MN screening assay was initially developed using V79 cells. Our laboratory has historically used the CHO cell line. Therefore, our laboratory was interested in comparing the two cell lines with regard to possible similarities or differences in MN induction sensitivity after exposure to cyclophosphamide (CPA) and mitomycin C (MMC), the two standard positive control chemicals routinely used in this assay. Three exposure conditions in the presence of CPA and MMC were examined in both cell lines. Replicate cultures of CHO cells in McCoy's 5A and V79 cells in both McCoy's 5A and E-MEM were established and treated with 5 microg CPA/ml (4h exposure with S9), 0.5 microg MMC (4h exposure without S9) and 0.5 microg MMC (24h exposure without S9). A total of 400 cytochalasin B-blocked binucleated cells and 200 consecutive cells were analyzed from each culture for MN and cell cycle kinetics, respectively. Analysis of the data demonstrated that CHO cells were up to approximately five-fold more sensitive to the induction of CPA- and MMC-induced MN than V79 cells. Both cell lines exhibited similar average generation times among identical exposure groups. Therefore, the difference in MN sensitivity cannot be attributed to possible differences in cell cycle kinetics and is possibly related to inherent cellular differences in the processing of and/or repair of CPA- and MMC-induced damage by V79 and CHO cells.