Antiparasitic activity of cystine protease inhibitor E-64 against Giardia lamblia excystation in vitro and in vivo.

In this work, the therapeutic effect of E-64, a broad spectrum cystine protease inhibitor against Giardia lamblia excystation was studied in vitro and in vivo. Purification of cysts from heavily infected human faecal samples followed by excystation and axenic cultivation of the emerging trophozoites in TYI-S-33 medium were done. In vivo, the response was evaluated experimentally through counting oocysts out-put every other day until the infection eradicated from the stools of infected E-64 treated mice compared to untreated. Also, the histopathological examination of the small intestine was compared between both of the infected groups. In the present study G. lamblia cysts incubated with E 64 in vitro completely failed in excystation in 90% while trophozoites released on 10% (partially excysted on 5% and completely excysted on 5%) compared to 90 % completely excysted on other non incubated (without E-64) of cysts beside, the trophozoites didn't release on 10% (partially excysted on 5% & completely non-excysted on 5%). In vivo, the evaluation of the therapeutic response proved that the decreasing in the oocysts out-put counting every other day until the infection eradicated from the stools of infected treated mice was very marked in comparison to untreated mice. The differences were statistically significant. The histopathological examination of the small intestine of infected non treated group proved that all the different pathological grades were found while in infected E-64 treated group, only grade I was detected. So, E-64 showed a good therapeutic effect which raises its use in the treatment of human giardiasis

Evaluation of the nitric oxide activity against Blastocystis hominis in vitro and in vivo.

The effect of exogenous nitric oxide (NO) on growth, viability and ultra-structural of B. hominis was assessed in vitro by sodium nitrite (NaNO2) in 0.6 mM, 0.8 mM & 1 mM concentrations. The viability of B. hominis was identified using neutral red stain. The role of NO as an endogenous oxidant was assessed by identifying its level in cecum tissue, ileum tissue, blood and stool elutes of mice infected with B. hominis symptomatic human isolates using reactive nitrogen assay compared to control. In vitro study revealed that NaNO2 inhibited the growth and decreased viability of B. hominis with minimal lethal concentra-tion dose 1 mM on the 4th day while, minimal effects were detected with 0.6 and 0.8 mM. Transmission electron microscopy study proved that apoptotic-like features were observed in growing axenic culture of B. hominis upon exposure to NaNO2. These changes were not only found on the vacuolar (central body) form but also they were detected on granular, multi-vacuolar and cyst forms. In vivo study proved that high levels of NO were found in infected mice compared to low changes in control group. The high levels were in cecum tissue particularly. The mean levels of NO among infected mice were 211.8 +/- 20.7 microM in cecum, 90.4 +/- 11.6 microM in ileum, 60.1 +/- 4.7 microM in blood and 63.6 +/- 7.3 microM in stool elutes while, the mean levels of NO in control mice were 70.2 +/- 3.1 in cecum, 67.8 +/- 4.7 microM in ileum, 30.9 +/- 4.2 microM in blood and 28.1 +/- 2.9 microM in stool elutes. The differences were statistically highly significant. NO-donor drugs proved useful in treatment and increase the host resistance to B. hominis.

Effect of exogenous adminstration of antioxidants on Blastocystis hominis in vivo.

The effect of exogenous administration of antioxidant (Anttox) on the course of B. hominis in experimentally infected mice was studied. B. hominis isolates were obtained from 10 gastrointestinal symptomatic adult patients. Three groups of 30 infected mice (3/isolate) were used. GI was untreated infected, GII was treated by antox for 4 weeks after infection diagnosis (treatment strategy), and GIII antox treated by for 4 weeks before infection (prophylactic strategy). Mild pathological changes were detected on 13.4%, 19.9% & 86.8% of mice in Gs I, II & III, respectively. Moderate pathological changes were found in 29.9%, 26.6% & 6.6% of mice in Gs I, II & III, respectively. While, the majority of severe pathological changes were in Gs I & II (56.7% & 53.5%) as compared to GIII (6.6%). Meanwhile, 86.8% of mice in GIII had B. hominis forms > 10/high power field compared to 3.3% in Gs I & II, respectively. Although 19.8% of mice in GII were positive for B. hominis by direct smear, no growth resulted in vitro and all the forms were non-viable by using neutral red stain. All the differences were statistically significant. So, antioxidant exacerbated B. hominis intensity but it decreased the pathological changes.