An oral recombinant vaccine in dogs against Echinococcus granulosus, the causative agent of human hydatid disease: a pilot study.

Dogs are the main source of human cystic echinococcosis. An oral vaccine would be an important contribution to control programs in endemic countries. We conducted two parallel experimental trials in Morocco and Tunisia of a new oral vaccine candidate against Echinococcus granulosus in 28 dogs. The vaccine was prepared using two recombinant proteins from adult worms, a tropomyosin (EgTrp) and a fibrillar protein similar to paramyosin (EgA31), cloned and expressed in a live attenuated strain of Salmonella enterica serovar typhimurium.In each country, five dogs were vaccinated with the associated EgA31 and EgTrp; three dogs received only the vector Salmonella; and six dogs were used as different controls. The vaccinated dogs received two oral doses of the vaccine 21 d apart, and were challenged 20 d later with 75,000 living protoscoleces. The controls were challenged under the same conditions. All dogs were sacrificed 26-29 d postchallenge, before the appearance of eggs, for safety reasons.We studied the histological responses to both the vaccine and control at the level of the duodenum, the natural localization of the cestode. Here we show a significant decrease of parasite burden in vaccinated dogs (70% to 80%) and a slower development rate in all remaining worms. The Salmonella vaccine EgA31-EgTrp demonstrated a high efficacy against E. granulosus promoting its potential role in reducing transmission to humans and animals.

Study on the hydatid cyst membrane: permeation of model molecules and interactions with drug-loaded nanoparticles.

The success of the chemotherapeutic treatment of hydatid disease is based upon the drug ability to operate on the germinal layer and on the protoscolices of the hydatid cyst interior at adequate concentrations for sufficient periods. The goal of this study was to evaluate the ability of the drug diffusion through the cyst membrane from sheep hydatid cysts and the increase of drug concentration in the cyst environment. In the first part of this work, the permeation behaviour through the hydatid cyst membrane was studied with five model molecules, having different molecular descriptors (logP, molecular weight, polar surface area ...) onto static Franz glass diffusion cells. A good correlation has been observed between the permeation coefficient and the partition coefficient, log P (r=0.951). In the second part, albendazole-loaded nanoparticles (about 300 nm) prepared by the emulsion solvent evaporation method have shown a sufficient entrapment efficiency (36.4 +/- 6.4%) to raise the apparent solubility of albendazole. The diffusion of drug from the nanoparticles across the hydatid cyst membrane was also improved compare to albendazole suspension. These results have shown the interest of the albendazole-loaded nanoparticles for the treatment of hydatid cysts in the future.

Echinococcus granulosus and other intestinal helminths in semi-stray dogs in Tunisia: infection and re-infection rates.

OBJECTIVE: Assessing the baseline prevalence and the re-infection rate of E. granulosus and other cestodes in dogs is important for a control program based on regular dog dosing treatment with praziquantel mainly to young rural dogs. METHODS: Three hundred and seventy five rural and semi-stray dogs from Jendouba (207 dogs) and Béjà (168 dogs) Departments in Northern-West of Tunisia, were examined to evaluate both the baseline prevalence of intestinal helminths and re-infection rates with Echinococcus granulosus and other cestodes. Parasites were collected in faeces following arecoline hydrobromide purge at the first examination of the dogs and at 4 intervals of reexamination: 2, 4, 8 and 12 months. After each examination, dogs were treated with praziquantel. RESULTS: The global baseline prevalence with Intestinal helminths in dogs was about 35 %. E. granulosus and other helminths were found in 3.5% (E. granulosus); 9.55% (Taenia hydatigena); 6.36% (Taenia pisiformis); 4.77% (Taenia multiceps); 8.59% (Dipylidium caninum), 5.41% (Mesocestoïdes sp.) and Ankylostoma caninum (13.37%). Dogs were re-infected with E. granulosus, T. hydatigena, T. pisiformis and D. caninum, 2 months after the arecoline hydrobromide purge while T. multiceps and Mesocestoïdes sp. infection reappeared 4 months later. CONCLUSION: A control program against Cystic/Echinococcosis, based on a regular treatment of the dog population with praziquantel every 60 days seems necessary. However in practice a six-monthly treatment during ten years would must to decrease the infection pressure of E. granulosus and cease transmission for human.

[Treatment of hydatid cyst in sheep. Assay of a new scolicide]. / Traitement du kyste hydatique chez la brebis, essai d'un nouveau scolicide.

OBJECTIVE: The main of this study was to show the rapidity of the protoscolicide action of a synthetic compound, dipeptide methyl ester when it is injected under echographic control into hydatid cyst of sheep. MATERIALS AND METHODS: Fourthty sheep with hydatid cysts, repaired at echography and punctionable are treated by dipeptide methyl ester injection at the dose of 110 mM. RESULTS: In vitro tests have allowed to define the efficacy dose of dipeptide methyl ester which is 110 mM. At echography, after injection of the drug, from the first minutes, a detachment of the inner membrane, a diminution of the size of the treated cyst were observed. The cyst content is modified. The sheep autopsy was realized after 4.6.12 and 17 weeks after the injection and showed a size reduction, a treated cyst calcification. CONCLUSION: The dipeptide methyl ester injection into hydatid cyst induces rapidly a morphological alteration, they are calcified. The advantage of this compound is its very rapidity action, this could decrease dissemination risks of hydatid liquid in the organism during operation. Also, this drug permits to reduce the operation time.

Toxoplasma gondii: localization of purine nucleoside phosphorylase activity in vitro and in vivo by electron microscopy.

Purine nucleoside phosphorylase (PNP, EC 2.4.2.1) activity was revealed by enzyme histochemistry in Toxoplasma gondii ME49 strain isolated from murine cerebral cysts and from in vitro cultivation. The activity of the enzyme was revealed by an insoluble electron-opaque precipitate of lead phosphate at the site of the reaction. In bradyzoites and tachyzoites of T. gondii, the enzyme activity could be observed only in the cytoplasm. In bradyzoites, one or two foci of important PNP activity were detected near the nucleus. In tachyzoites, an important PNP activity underlined the plasma membrane. For both bradyzoites and tachyzoites, localization neither in the nucleus nor in cytoplasmic organelles could be detected.

Prevalence of toxoplasma encephalitis in AIDS patients treated with Didanosine hospitalised in a French infectious service.

In a previous work, we have showed in mice infected with an avirulent strain of Toxoplasma gondii and receiving a didanosine treatment, an important decrease of brain cysts. It is why, the purpose of this study was to investigate the effect of didanosine treatment on AIDS patients having developed Toxoplasma encephalitis. 60 patient reports were analyzed: 22 patients (group 1) did not received didanosine in their antiretroviral treatment and 38 (group 2) were treated with didanosine. The results showed that an antiretroviral therapy was prescribed for 93% of patients, 50% of them received only zidovudine and protease inhibitors were prescribed for 37%. The regimens given most frequently were those including zidovudine plus lamivudine or zidovudine plus indinavir. Among the group 1, 18% have had a relapse of Toxoplasma encephalitis. In the group 2, 37% of the patients suffered from one episode of TE while 16% have had two TE after the pause in their didanosine treatment, the maximum occurring between 4 and 24 months after the pause of didanosine. This study showed that didanosine seems to have an effect on cerebral cysts. Also, this work made a synthesis about the different treatment used in AIDS patients and the new molecules yet in development against T. gondii.