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Biomedical subjects

Peter Hotez

Publications and source records attributed to Peter Hotez.

13 recordsLinked to original sources
PubMed2007

Repeatability of paired counts.

The Bland and Altman technique is widely used to assess the variation between replicates of a method of clinical measurement. It yields the repeatability, i.e. the value within which 95 per cent of repeat measurements lie. The valid use of the technique requires that the variance is constant over the data range. This is not usually the case for counts of items such as CD4 cells or parasites, nor is the log transformation applicable to zero counts. We investigate the properties of generalized differences based on Box-Cox transformations. For an example, in a data set of hookworm eggs counted by the Kato-Katz method, the square root transformation is found to stabilize the variance. We show how to back-transform the repeatability on the square root scale to the repeatability of the counts themselves, as an increasing function of the square mean root egg count, i.e. the square of the average of square roots. As well as being more easily interpretable, the back-transformed results highlight the dependence of the repeatability on the sample volume used.

Algorithms↗
PubMed2006

Hookworm vaccines: past, present, and future.

Hookworms are gastrointestinal nematodes that infect almost 1 billion people in developing countries. The main clinical symptom of human hookworm infections is iron-deficiency anaemia, a direct consequence of the intestinal blood loss resulting from the parasite's feeding behaviour. Although treatment is available and currently used for the periodic removal of adult hookworms from patients, this approach has not effectively controlled hookworm in areas of rural poverty. Furthermore, treated individuals remain susceptible to reinfection following exposure to third-stage infective hookworm larvae in the soil as early as 4-12 months after drug treatment. Therefore, a prophylactic vaccine against hookworm infection would provide an attractive additional tool for the public-health control of this disease. The feasibility of developing a vaccine is based on the previous success of an attenuated larval vaccine against canine hookworm. Several laboratory and field studies have explored the development of a human anti-hookworm vaccine, describing potential protective mechanisms and identifying candidate antigens, one of which is now in clinical trials. The current roadmap that investigators have conceived has been influenced by vaccine development for blood-feeding nematodes of livestock and companion animals; however, recombinant vaccines have yet to be developed for nematodes that parasitise animals or human beings. The roadmap also addresses the obstacles facing development of a vaccine for developing countries, where there is no commercial market.

Global Health↗
PubMed2005

Necator americanus: optimization of the golden hamster model for testing anthelmintic drugs.

Laboratory golden hamsters (Mesocricetus auratus) were infected with Necator americanus under several different parasite and host conditions to optimize the model for testing anthelminthic drugs. The results confirmed that male hamsters were more susceptible to infection than females. Host age in the range of 5-15 weeks was not a factor that impacted on adult worm burden, and similar worm burdens were achieved using doses of 150, 250 or 500 N. americanus L3 (NaL3). The largest numbers of adult hookworms were recovered on days 21-28 post-infection, with a significant decrease at days 40-50 post-infection. Therefore adult worm recovery is maximal approximately 11-18 days prior to patency and host blood loss. From these studies a drug evaluation protocol was developed using 150 NaL3 as the infectious dose and then evaluating the anthelminthic effects of the drugs albendazole, tribendimidine, and pyrantel pamoate on days 21-28 post-infection. The model confirms the anthelminthic activity of albendazole, tribendimidine, and pyrantel pamoate and has the potential as a laboratory animal model to detect emerging drug resistance.

Age Factors↗
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↗
PubMed2004

A pore-forming haemolysin from the hookworm, Ancylostoma caninum.

Hookworms feed on blood, but the mechanism by which they lyse ingested erythrocytes is unknown. Here we show that Ancylostoma caninum, the common dog hookworm, expresses a detergent soluble, haemolytic factor. Activity was identified in both adult and larval stages, was heat-stable and unaffected by the addition of protease inhibitors, metal ions, chelators and reducing agents. Trypsin ablated lysis indicating that the haemolysin is a protein. A closely migrating doublet of hookworm proteins with apparent molecular weights of 60-65 kDa bound to the erythrocyte membrane after lysis of cells using both unlabeled and biotinylated detergent-solubilised hookworm extracts. In addition, separation of detergent-soluble parasite extracts using strong cation-exchange chromatography, resulted in purification of 60-65 kDa proteins with trypsin-sensitive haemolytic activity. Erythrocytes lysed with particulate, buffer-insoluble worm extracts were observed using scanning electron microscopy and appeared as red cell ghosts with approximately 100 nm diameter pores formed in the cell membranes. Red blood cell ghosts remained visible indicating that lysis was likely caused by pore formation and followed by osmotic disruption of the cell.

Ancylostoma↗
PubMed2003

[Prokaryotic expression and characterization of an antigenic gene of adult Trichinella spiralis].

OBJECTIVE: To obtain a purified Ts87 gene expression product of adult Trichinella spiralis and identify its immunogenicity. METHODS: Ts87 cDNA was subcloned into PET-28a(+) expression vector. The transformed bacteria bearing PET-28a(+)/Ts87 plasmids were induced by IPTG for production of fusion proteins. The expression product purified with His-binding affinity chromatography and electro-elution assay was analyzed by SDS-PAGE, ELISA and Western blot, and was used to immunize the rabbits. RESULTS: PET-28a(+)/Ts87 transformed bacteria produced the desired fusion protein with a relative molecular weight of 40 kDa. The antisera with high titer were obtained by immunizing rabbit with Ts87 recombinant protein. Ts87 expression protein was detected as positive reaction with infected rabbit sera, infected swine sera and antisera against Ts87 by ELISA. Ts87 protein was also recognized by above-mentioned sera with Western blotting. However, Ts87 protein failed to react with the patient sera infected with Cysticercus cellulosae or Echinococcus granulosus, and rabbit sera infected with Schistosoma japonicum. CONCLUSION: A new Trichinella recombinant protein with specific antigenicity was obtained.

Animals↗
PubMed2002

Augmented bioavailability and cysticidal activity of albendazole reformulated in soybean emulsion in mice infected with Echinococcus granulosus or Echinococcus multilocularis.

The anthelminthic drug, albendazole (Abz), was reformulated in a soybean oil emulsion and evaluated as a therapeutic agent for the treatment of Echinococcus granulosus and Echinococcus multilocularis in mice. Abz emulsified with 30% soybean oil (AbzE-30) resulted in higher circulating plasma concentrations of the major bioactive Abz metabolite, Abz sulfoxide (AbzSOX), after oral administration, compared with an Abz suspension. The soybean oil-emulsified Abz compound was also noted to penetrate into the hydatid cyst wall and produced higher hydatid cyst concentrations of AbzSOX. The emulsion was superior to Abz suspension in reducing the size of hydatid cysts caused by E. granulosus protoscolices collected from naturally infected sheep in Urumchi, Xinjiang Uygar Autonomous Region. In contrast, the reformulated compound's ability to reduce E. multilocularis cyst masses was only marginally superior to Abz suspension. AbzE-30 exhibited increased bioavailability and bioactivity in the treatment of murine Echinococcus hydatid cyst infections. The compound has the potential for improving therapeutic outcomes for human echinococcosis.

Albendazole↗
PubMed2002

Albendazole-soybean oil emulsion for the treatment of human cystic echinococcosis: evaluation of bioavailability and bioequivalence.

A single 12.5 mg/kg dose of albendazole (Abz) in tablet form (AbzT) followed 2 weeks later by an equivalent dose of Abz emulsified in 30% soybean oil (AbzE) was administered orally 2 h after the first morning meal to 7 male adult patients with cystic echinococcosis caused by Echinococcus granulosus. Serum samples were taken 1, 3, 5, 7, 8, 9, 11, 14, 18, 24, 36, and 48 h post medication from each patient to measure the serum concentrations of albendazole sulfoxide (AbzSOX), the principal bioactive metabolite of Abz. AbzSOX concentrations were measured by reverse phase HPLC. The data were subjected to pharmacokinetic analysis to compare the relative bioavailability and bioequivalence of AbzT and AbzE. The results demonstrated that the mean peak concentrations (C(max)) for AbzT and AbzE were 1.06+/-0.38 mg/l and 1.71+/-0.47 mg/l, respectively; the area under the concentration-time curves (AUC) were 13.24+/-4.93 mg x h/l and 21.01+/-7.54 mg x h/l, respectively. The relative bioavailability of AbzE was F(Flu)=1.59. Two one-sided tests procedure and (1-2 alpha) 90% confidence interval methods were used to evaluate the bioequivalence of AbzE and AbzT. The results demonstrated that the bioavailability of AbzE was greater than AbzT.

Administration, Oral↗
PubMedDate not supplied

Necator americanus: maintenance through one hundred generations in golden hamsters (Mesocricetus auratus). II. Morphological development of the adult and its comparison with humans.

Through 100 passages, the human hookworm Necator americanus was adapted to the golden hamster, Mesocricetus auratus, without either the requirement for exogenous steroids or other immunosuppressive agents, nor the requirement to infect hamsters as pups. Adult N. americanus recovered from infected hamsters were morphologically similar to those from infected humans in Sichuan Province, China, although they were smaller and the females produced fewer eggs. The natural history and kinetics of N. americanus infection was different in female and male hamsters. Female hamsters supported low intensity infections that lasted for approximately two months. In contrast, the peak intensity of infection in male hamsters was high, but this situation lasted less than for 4 weeks at which time many of the hookworms were expelled. However, even after the major parasite expulsion, the total number of hookworms consistently remained higher in chronically infected male hamsters compared with female hamsters. The hamster model of N. americanus is potentially useful for studying the development of new anthelminthic drugs and vaccines.

Animals↗