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PubMed2004

Cellular responses and cytokine production in post-treatment hookworm patients from an endemic area in Brazil.

Human hookworm infections are distributed widely in tropical areas and have a significant impact on host morbidity and human health. In the present study, we investigated the cellular responsiveness and cytokine production in peripheral blood mononuclear cells (PBMC) from Necator americanus-infected schoolchildren who had recently received chemotherapy, and compared them with non-infected endemic controls. Hookworm patients and treated, egg-negative individuals showed a lower cellular reactivity against phytohaemagglutinin (PHA) and hookworm antigen when compared with egg-negative endemic controls. The baseline production of proinflammatory tumour necrosis factor-alpha (TNF-alpha) in PBMC from infected patients and treated, egg-negative individuals was elevated. On the other hand, PHA- or hookworm antigen-induced interleukin (IL)-12 and interferon (IFN)-gamma secretion was higher in endemic controls than in hookworm patients, who either continued egg-positive or were egg-negative after treatment. Also, PBMC from endemic controls secreted more IL-5 and IL-13 than the other patient groups. Opposite to that, the spontaneous as well as the antigen-driven IL-10 secretion was lower in endemic controls when compared with the other groups. In summary, patently hookworm-infected as well as egg-negative treated patients disclosed an elevated spontaneous cellular secretion of proinflammatory TNF-alpha, a prominent secretion of regulatory Th2-type IL-10 and an impaired production of IL-12, IFN-gamma, IL-5 and IL-13.

Albendazole↗
PubMed2005

Immune responses following experimental human hookworm infection.

To characterize the immune response following primary human hookworm infection, an adult volunteer was infected with 50 L3 larvae of Necator americanus, reinfected 27 months later and followed for a further 6 months. Clinical signs, blood picture, ex-vivo peripheral blood cytokine production (IFN-gamma, IL-5, IL-13, IL-10 to mitogen and hookworm antigen), acute phase proteins (APP) (C-reactive protein, CRP and alpha1-antitrypsin, alpha1-AT) and antibody levels were determined. Dermatitis, oedema, mild nausea and abdominal discomfort followed the primary infection. Eosinophil counts peaked early during both infections but remained elevated ( approximately 18%) throughout. Transient production of IL-5, IL-13 and APP also followed infection but there were negligible levels of IFN-gamma or IL-10. The onset of nausea, oedema and the initial rise in CRP, alpha1-AT, eosinophilia and IL-5 coincided (days 13-27) with the late larval migration and early establishment of the preadult worms in the intestine. Apart from the eosinophilia these responses declined to baseline levels within 4 months and were less pronounced on re-infection.

Animals↗
PubMed1992

Distinction of human hookworm larvae based on lectin-binding characteristics.

A comparative study of lectin binding to ensheathed (EnL3) and exsheathed (ExL3) L3 larvae of Necator americanus, Ancylostoma duodenale and Ancylostoma ceylanicum revealed a number of differences between these hookworm species. These differences could provide a novel approach to distinguish infective L3 larvae in field conditions. For example, binding of Ulex europaeus agglutinin (UEA) and Ricinus communis agglutinin (RCA120) to N. americanus EnL3 distinguished them from those of A. duodenale and A. ceylanicum. Furthermore, UEA and RCA120 negative EnL3 could be separated into the two Ancylostoma sps. tested, as Dolichos biflorus agglutinin and Soybean agglutinin bound to EnL3 of A. ceylanicum but not to those of A. duodenale.

Ancylostoma↗
PubMed1995

Immunoepidemiology of human necatoriasis: correlations between antibody responses and parasite burdens.

In this paper we describe the relationship between antibodies to Necator americanus stage-specific antigens and parasite burden in an endemically-infected population in Papua New Guinea. Using an age-structured analysis, we show that the correlation coefficient between levels of IgG against adult worm excretory-secretory (ES) antigen and parasite burden declined significantly with host age from positive in younger hosts to significantly negative in older hosts. A trend towards similar patterns was present for anti-larval IgG both pretreatment and after reinfection, and for anti-ES IgM and anti-ES IgE pretreatment. These patterns are consistent with a role for these isotypes in a protective immune response, although parasite-induced immunosuppression may provide an alternate explanation. This is another demonstration of possibly protective responses to N. americanus infection.

Adolescent↗
PubMed2005

The assessment of hookworm calreticulin as a potential vaccine for necatoriasis.

A vaccine against the human hookworm Necator americanus is urgently required to reduce hookworm-induced morbidity in endemic areas. In the present study, recombinant hookworm calreticulin, a nominated vaccine candidate, has been tested in mice. Mice given calreticulin had 43-49% fewer worms in their lungs, compared to non-vaccinated controls, following challenge infection with infective hookworm larvae. These levels of protection were achieved in the absence of adjuvant following intraperitoneal administration of three doses of 15 microg antigen. Antigen was also encapsulated in PLG microparticles. Encapsulated calreticulin elicited higher levels of anti-calreticulin IgG1 than free antigen but failed to induce protective immunity. The protection induced by free calreticulin was associated with low levels of serum IgE and moderate lung eosinophilia whilst administration of calreticulin-loaded microparticles was associated with high levels of serum IgE and higher lung eosinophil activity, suggesting that the classical Th2 phenotype may not always be associated with protective immunity, albeit in experimental necatoriasis.

Animals↗
PubMed1997

Hookworm control as a strategy to prevent iron deficiency.

The hookworms Necator americanus and Ancylostoma duodenale infect approximately 1 billion people worldwide. The prevalence of hookworm infection increases with age in children, typically reaching a plateau in late adolescence, whereas the intensity of infection may continue to increase throughout adulthood. Hookworms cause intestinal blood loss in amounts proportional to the number of adult worms in the gut. The relationship between hookworm infection intensity and hemoglobin concentration is evident in epidemiologic studies, but may be apparent only above a threshold worm burden that is related to the iron stores of the population. Current hookworm control efforts are focused on reducing infection load and transmission potential through periodic anthelminthic chemotherapy. Several controlled trials have demonstrated a positive impact of anthelminthic treatment on hemoglobin levels, with best results obtained in settings where iron intakes were also increased. Evidence suggests that anthelminthic programs will have modest impacts on iron deficiency anemia in the short term, with greater impacts on more severe anemia. Hookworms are an important cause of anemia in women, who are often overlooked by current helminth control programs. Current WHO recommendations for use of anthelminthics in schoolchildren and women are reviewed. There is a need to clarify whether hookworms are an important etiology of iron deficiency anemia in preschool children.

Adolescent↗
PubMed2006

Recombinant Escherichia coli strain produces a ZZ domain displaying biopolyester granules suitable for immunoglobulin G purification.

The immunoglobulin G (IgG) binding ZZ domain of protein A from Staphylococcus aureus was fused to the N terminus of the polyhydroxyalkanoate (PHA) synthase from Cupriavidus necator. The fusion protein was confirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and mediated formation of ZZ domain-displaying PHA granules in recombinant Escherichia coli. The IgG binding capacity of isolated granules was assessed using enzyme-linked immunosorbent assay and could be enhanced by the overproduction of the ZZ-PHA synthase. ZZ-PHA granules enabled efficient purification of IgG from human serum.

Acyltransferases↗
PubMed1990

Parasite detection efficiencies of five stool concentration systems.

Fresh fecal material that was free of ova and parasites was pooled with 10% Formalin in a 1:4 ratio to prepare a standard specimen. Portions of 100 ml of this specimen were individually seeded with Cryptosporidium oocysts, Entamoeba coli, Entamoeba histolytica, and Giardia lamblia cysts; ova of Necator americanus; and Strongyloides larvae. Appropriate volumes of each parasite suspension were used to evaluate the Fecal Concentrator Kit (Remel, Lenexa, Kans.), Fecal Parasite Concentrator (Evergreen Scientific, Los Angeles, Calif.), Para-Pak Macro-Con (Meridian Diagnostics, Inc., Cincinnati, Ohio), and Trend FeKal CON-Trate (Trend Scientific, Inc., St. Paul, Minn.). A standardized gauze filtration method was used as the reference procedure. Tests were performed in triplicate with each individual parasite-concentrator combination, with three slides examined from each sediment. All of the systems effectively concentrated parasites compared with direct examination of unconcentrated fecal material. The Fecal Concentrator Kit provided the best overall performance. Clarity of sediment, lack of debris, and uniformity of background material were found to be important considerations for microscopic detection of parasites in concentrated specimens.

Animals↗
PubMed2003

Basophils express a type 2 cytokine profile on exposure to proteases from helminths and house dust mites.

The proteolytic activities frequently associated with sources of allergens and parasite secretions have been suggested as important immunomodulators. We have investigated whether the protease activity of the house dust mite allergen Der p1 and the secreted proteases of the hookworm Necator americanus are able to directly induce type 2 cytokine production by basophils. Der p1 and the secretions of N. americanus induced interleukin (IL)-4, IL-5, and IL-13 but not interferon-gamma mRNA in KU812 basophils. Enzyme-linked immunosorbent assay confirmed that IL-4 and IL-13 were secreted. A nonproteolytic antigen failed to induce cytokine expression, and preincubation of Der p1 or N. americanus secretions with protease inhibitors inhibited cytokine expression. Data were confirmed using basophils purified from human peripheral blood. We speculate that this innate mechanism may contribute to the development of a cytokine milieu that could promote immunoglobulin E synthesis, eosinophil recruitment, and the development of type 2 T cells.

Animals↗
PubMed2004

The innate allergenicity of helminth parasites.

Helminth parasites are well known to induce an immune response in their hosts characterised by elevated IgE, peripheral blood or local tissue eosinophilia, and in some cases, intestinal mastocytosis. This immunological response has a strong T-helper 2 (Th2) cytokine bias and is reminiscent of the immunological constellation found in allergic diseases. However, the molecular forces driving the Th2 response to helminth parasites are still not understood. By using the human hookworm parasite Necator americanus as an example, the authors of the current article propose that in the course of its life cycle, this parasite becomes innately allergenic through the secretion of a molecular array designed to promote tissue migration and homing, feeding and survival against immunological attack. This complex array comprises proteases, lectins and other classes of molecules. Subsequent immunological and physiological events seemingly protect the host from both the allergic sequelae of exposure to environmental allergens and, moreover, from the parasite itself.

Allergens↗
PubMed2001

Species-specific identification of human hookworms by PCR of the mitochondrial cytochrome oxidase I gene.

Significant differences in the life histories of the human hookworms Ancylostoma duodenale and Necator americanus necessitate their differentiation for epidemiological studies and the design of control programs. Current methods of identification require time-consuming, labor-intensive techniques. A polymerase chain reaction (PCR)-based method that enables rapid species identification is described. The mitochondrial cytochrome oxidase I genes of both species were sequenced, and species-specific primer sets were designed. The primers were used in PCR to amplify 585-bp fragments of the cytochrome oxidase gene from individual hookworm eggs, larvae, and adults. The technique was also able to identify mixed infections containing equal amounts of eggs from each species. The technique is rapid, technically simple, and sensitive and will permit the accurate identification of human hookworms in epidemiological field studies.

Ancylostoma↗
PubMed2000

Eotaxin is specifically cleaved by hookworm metalloproteases preventing its action in vitro and in vivo.

Eotaxin is a potent eosinophil chemoattractant that acts selectively through CCR3, which is expressed on eosinophils, basophils, mast cells, and Th2-type T cells. This arm of the immune system is believed to have evolved to control helminthic parasites. We hypothesized that helminths may employ mechanisms to inhibit eosinophil recruitment, to prolong worm survival in the host. We observed that the excretory/secretory products of the hookworm Necator americanus inhibited eosinophil recruitment in vivo in response to eotaxin, but not leukotriene B(4), a phenomenon that could be prevented by the addition of protease inhibitors. Using Western blotting, N. americanus supernatant was shown to cause rapid proteolysis of eotaxin, but not IL-8 or eotaxin-2. N. americanus homogenate was fractionated by gel filtration chromatography, and a FACS-based bioassay measured the ability of each fraction to inhibit the activity of a variety of chemokines. This resulted in two peaks of eotaxin-degrading activity, corresponding to approximately 15 and 50 kDa molecular mass. This activity was specific for eotaxin, as responses to other agonists tested were unaffected. Proteolysis of eotaxin was prevented by EDTA and phenanthroline, indicating that metalloprotease activity was involved. Production of enzymes inactivating eotaxin may be a strategy employed by helminths to prevent recruitment and activation of eosinophils at the site of infection. As such this represents a novel mechanism of regulation of chemokine function in vivo. The existence of CCR3 ligands other than eotaxin (e.g., eotaxin-2) may reflect the evolution of host counter measures to parasite defense systems.

Animals↗
PubMed2005

Immunogenicity of the hookworm Na-ASP-2 vaccine candidate: characterization of humoral and cellular responses after vaccination in the Sprague Dawley rat.

The recombinant larval protein Na-ASP-2 from the human helminth parasite Necator americanus is a lead candidate for a human hookworm vaccine. We have characterized the humoral and cellular immune responses elicited by the Na-ASP-2 formulated with the aluminum-based adjuvant Alhydrogel in the Sprague Dawley rat. We demonstrated that Na-ASP-2 vaccine induced a strong antibody response at all doses tested, as evidenced by high specific IgG1, IgG2a and IgM titers. High IgG antibody titers were maintained up to three months post vaccination and were boosted by an additional vaccine dose. Specific cell proliferation and a Th2 cytokine profile were also observed in peripheral blood of all rats immunized with the formulated vaccine. Host IL-6 levels were also significantly elevated. These data provide evidence that the immune response of the Na-ASP-2 vaccine is robust and durable and therefore suitable for the further clinical development of the Na-ASP-2 vaccine.

Adjuvants, Immunologic↗
PubMed1975

Evaluation of the skin test for hookworm as an epidemiological tool.

The usefulness of a skin test with larval Necator americanus antigen for assessment of hookworm prevalence was evaluated in an endemic area of Costa Rica. In comparison with standard coprologic techniques employed to survey the population, the skin test detected 83% of infections, showing a fairly satisfactory sensitivity. The overall specificity of the test was 50%, i.e., random. No correlation was found between skin reactivity and hookworm burden. The sensitivity of the test increased moderately with age, but its specificity decreased significantly at the same time. False positive reactions were more numerous among persons formerly infected with hookworm who had been negative for as long as 5 years. There was an indication of cross reactivity with intestinal nematodes other than hookworm. The test was used to detect hookworm infected persons in the community for selective treatment, in comparison with mass treatment of all the people in another village. The selective administration of an anthelminthic drug to only skin test positive persons did not achieve the same drop in community hookworm prevalence as did the indiscriminate treatment of the whole population.

Adolescent↗
PubMed1978

Population biology of hookworms in children in rural West Bengal. II. Acquisition and loss of hookworms.

From changes in hookworm egg counts in feces of children in Gangetic West Bengal we estimate that, on the average, each child lost about 11.1 female hookworms during the 1969 post-monsoon dry period and gained about 10.3 females during the subsequent premonsoon and monsoon seasons, resulting in a net loss of worms over the 22-month study period. However, the mean fecal egg count for each 1-year age group of children from 3-11 years suggests an average net gain of 2.7 female worms/year. From seasonal changes in the relative abundance of larvae recovered from fecal cultures, it is estimated that at least 82% of the yearly gain in Ancylostoma duodenale females is a result of the maturation of hypobiotic (latent) larvae acquired during the previous wet season. A duodenale was present about equally with Necator americanus but it was significantly more common among males than among females, and more common among Muslims than among Hindus. Using damp gauze pads, we sampled the soil surface around freshly-passed feces for infective hookworm larvae and estimated that 252 larvae were contacted by each child durint the transmission season. Efficiency of penetration and maturation of each hookworm species was calculated from estimated larval densities on the soil surface, from seasonal changes in fecal egg counts, and from variations in the number of larvae recovered from fecal cultures by season and age of the host; it is estimated that N. americanus is 17.5% efficient and A. duodenale 5.3%. Children negative for hookworm became positive at all times of the year and at a significantly higher rate in 1970 than in 1969; incidence averaged 4.2% per 2-month period and mean initial fecal egg count suggested infection with about 2.0 female worms. The average life span for N. americanus is calculated to be 3-4 years and that of A. duodenale about 1 year under the conditions of reinfection found in the study area.

Ancylostoma↗
PubMed1992

Influence of intestinal parasitism on lactose absorption in well-nourished African children.

Hydrogen breath tests were performed in Gabon (Central Africa) after a loading dose of lactose in 67 well-nourished African children (50 with intestinal parasites and 17 unparasitized) and in 18 unparasitized young adults. All had normal nutritional status, and none had diarrhea or digestive symptoms. Parasites that were found included Ascaris lumbricoides in 76% of the parasitized children, Trichuris trichiura in 58%, Giardia in 24%, Entamoeba histolytica in 20%, Schistosoma intercalatum in 16%, and Necator Americanus in 14%. A similar proportion of parasitized (64%) or unparasitized (62.8%) subjects were lactose malabsorbers. Giardia infection was associated with a higher, but not significantly different, proportion of lactose intolerance (10 of 12, 83.3%). The presence of infection with A. lumbricoides or T. trichiura did not increase the percentage of lactose malabsorption. These data indicate that a decrease of lactase activity in well-nourished African children is not related to the presence or the importance of Ascaris or other intestinal parasites if the nutritional status is normal.

Animals↗
PubMed1997

Failure of mebendazole in treatment of human hookworm infections in the southern region of Mali.

Preliminary studies indicated that single-dose (500 mg) mebendazole gave disappointing results in the treatment of hookworm infections (Necator americanus) in Mali. A placebo-controlled, randomized trial conducted with the participation of 103 infected subjects (background hookworm prevalence > 50%) confirmed that mebendazole (Vermox) did not reduce parasite burdens significantly, as assessed through fecal egg counts. In contrast, a group of subjects treated with pyrantel (Combantrin) experienced a significant reduction in fecal worm egg counts (overall, both sexes combined showed a 75% reduction). Male subjects carried significantly more intense infections compared with females, but there was no gender difference in response to treatment. A standard egg hatch assay showed that N. americanus from our subjects in Mali was more resistant to benzimidazoles compared with a laboratory-maintained strain that had not been exposed to anthelmintics in more than 100 generations (50% effective dose = 0.12 and 0.07 microg/ml of thiabendazole, respectively), suggesting that, among other possibilities, the development of resistance to the benzimidazoles by N. americanus may have contributed to the drug failure. Whatever the underlying explanation, our results indicate that single-dose treatment with mebendazole is an ineffective treatment for hookworm infections and despite its relatively cheap cost and wide availability, mebendazole should not be considered a drug of choice in the mass treatment of hookworm infections in this region of Mali.

Adolescent↗
PubMed1998

Epidemiology of human intestinal nematode infections in Wujiang and Pizhou counties, Jiangsu Province, China.

Intestinal nematode infections are considered highly endemic in the Chinese province of Jiangsu. In May 1997, the prevalence of intestinal nematodes infections was determined among all of the inhabitants aged 5 to 65 of the southern Jiangsu village of Yaojiakon (Wujiang County) and the northern Jiangsu village of Jianmiao (Pizhou County). It was determined that the prevalence of ascariasis, trichuriasis and hook worm infection was greatly reduced compared to when it was last measured in 1990. The reduction was noted to be particularly impressive in Yaojiakon village where the prevalence of ascariasis and trichiuriasis fell to 2% and 1.5% respectively. Much of this reduction was attributed to improvements in economic development which have occurred in southern Jiangsu Province at a rapid pace. In contrast, the reduction in nematode infections among villagers living in northern Jiangsu was more modest. The most striking reduction in both villages was in school-aged children who since 1988 have received yearly treatments with anthelminthic drugs. The intensity of nematode infections was investigated for hookworm where 70% of hookworm-infected Yaojiakon villagers were found to harbor light infections (< 400 eggs per gram) compared to 83% of hookworm-infected Jianmiao villagers. Necator americanus was the predominant hookworm in Yaojiakon village (South), whereas Ancylostoma duodenale predominated in Jianmiao village (North). The majority (76%) of hookworm-infected patients developed IgG antibodies against N. americanus antigen, although 20% of uninfected patients living in the village also had circulating antibodies. Intestinal nematode infections continue to be a significant public health problem in Jiangsu Province although their prevalence has decreased since 1990.

Adolescent↗