Article

Inhibition of Giardia lamblia excystation by antibodies against cyst walls and by wheat germ agglutinin

Division of Infectious Diseases, Department of Medicine, University of California at San Diego Medical Center, 92103-8416, USA.
Infection and Immunity (Impact Factor: 4.16). 06/1996; 64(6):2151-7.
Source: PubMed

ABSTRACT Although excystation is crucial to the initiation of infection by Giardia lamblia, little is known about the regulation of this important process. We have been able to reliably induce excystation in vitro by mimicking cyst passage through the stomach and upper small intestine by the exposure of in vitro-derived cysts to an acidic, reducing environment (stage I) followed by protease treatment at a slightly alkaline pH (stage II). Preexposure of cysts to polyclonal rabbit antiserum against purified cyst walls (PCWs) or to wheat germ agglutinin (WGA) inhibited excystation by > 90%. Adsorption of either ligand with PCWs eliminated inhibition, demonstrating specificity for cyst wall epitopes. Inhibition by WGA was reversed by either chitotriose or sialic acid, while inhibition by polyclonal antibodies against PCWs (anti-PCW) was reversed only by sialic acid, which also inhibited binding of both ligands to intact cysts and to cyst wall antigens in immunoblots. Binding of anti-PCW did not affect acidification of cyst cytoplasm during stage I. Exposure of cysts to anti-PCW and WGA prior to, but not after, stage II was sufficient to inhibit excystation, and inhibition could be partially reversed by increasing the protease concentration during stage II. A 7- to 10-fold higher proportion of WGA- and anti-PCW-treated cysts than control cysts remained intact after stage II. Our results suggest that these ligands, which bind cyst wall epitopes, inhibit excystation, most likely by interfering with proteolysis of cyst wall glycoproteins during stage II.

1 Follower
 · 
151 Views
  • Source
    • "Targeting of carbohydrate residues by the use of lectins showed that WGA produce dose related growth inhibition of Giardia lamblia trophozoites in vitro [22] . Lectins could also inhibit G. lamblia excystation as effectively as monoclonal antibodies directed against cyst wall antigens [23] . The combined therapy of nitazoxanide (NTZ) and WGA was shown earlier, and better therapeutic effect against cryptosporidial infection in an experimental study [24] . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Trichomoniasis is one of the most common parasitic sexually transmitted diseases in the world. Metronidazole was known as the most effective drug for human trichomoniasis., however, drug resistance and toxicity appeared. This study was designed to investigate the in vitro inhibitory activity of wheat germ agglutinin and Nigella sativa aqueous extract on the growth and motility of Trichomonas vaginalis in comparison to metronidazole. The inhibitory effect was dose related. Minimal lethal concentration of wheat germ agglutinin was 250µg 250µg/ml in all incubation periods. Minimal lethal concentration of metronidazole was 50µg 50µg/ml after 24 hours. However, lower doses of metronidazole showed a minimal lethal concentration of 25µg 25µg/ml after 48 h and 12µg 12µg/ml after 72 h of incubation; whereas, lower doses of wheat germ agglutinin failed to completely inhibit the parasite growth. Although N. sativa aqueous extract had the lowest effect on parasite growth, producing a lethal effect only after 48 h, it still has a remarkable effect. All drugs remarkably inhibited the motility of the trophozoites. The results showed a promising effect of using wheat germ agglutinin and N. sativa aqueous extract in treating T. vaginalis infection.
  • Source
    • "Targeting of carbohydrate residues by the use of lectins showed that WGA produce dose related growth inhibition of Giardia lamblia trophozoites in vitro [22] . Lectins could also inhibit G. lamblia excystation as effectively as monoclonal antibodies directed against cyst wall antigens [23] . The combined therapy of nitazoxanide (NTZ) and WGA was shown earlier, and better therapeutic effect against cryptosporidial infection in an experimental study [24] . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Trichomoniasis is one of the most common parasitic sexually transmitted diseases in the world. Metronidazole was known as the most effective drug for human trichomoniasis., however, drug resistance and toxicity appeared. This study was designed to investigate the in vitro inhibitory activity of wheat germ agglutinin and Nigella sativa aqueous extract on the growth and motility of Trichomonas vaginalis in comparison to metronidazole. The inhibitory effect was dose related. Minimal lethal concentration of wheat germ agglutinin was 250µg 250µg/ml in all incubation periods. Minimal lethal concentration of metronidazole was 50µg 50µg/ml after 24 hours. However, lower doses of metronidazole showed a minimal lethal concentration of 25µg 25µg/ml after 48 h and 12µg 12µg/ml after 72 h of incubation; whereas, lower doses of wheat germ agglutinin failed to completely inhibit the parasite growth. Although N. sativa aqueous extract had the lowest effect on parasite growth, producing a lethal effect only after 48 h, it still has a remarkable effect. All drugs remarkably inhibited the motility of the trophozoites. The results showed a promising effect of using wheat germ agglutinin and N. sativa aqueous extract in treating T. vaginalis infection. يعتبر داء الدويبات الشعرية واحد من أكثر الأمراض الطفيلية المنقولة جنسيًا في العالم. ويعتبر عقار المترونديزول بأنه أكثر العقاثير فعالية لعلاج داء الدويبات الشعرية، وقد أظهر الطفيل مقاومة ضده، بالإضافة الى سميته. أجريت هذه الدراسة بهدف التحقيق من التأثير المثبط المخبري لكل من القمح الجرثومي الملزن، والمستخلص المائى لبذور الحبة السوداء على نمو وحركة طفيل الدويبات الشعرية مقارنة بالتأثير المثبط لعقار المترونديزول. ووجد أن التأثير المثبط ذو صلة بالجرعة. كما وجد أن التركيز الأدنى المميت للقمح الجرثومي الملزن كان 250 ميكروجرام/مل في جميع فترات الحضانة. والتركيز الأدنى المميت للميترونديزول هو 50 ميكروجرام/مل بعد 24 ساعة. غير أن جرعات أقل من الميترونديزول أظهرت تركيزاً أدنى مميت عند 25 ميكروجرام/مل بعد 48 ساعة، و12 ميكروجرام/مل بعد 72 ساعة من الحضانة، بينما جرعات أقل من القمح الجرثومي الملزن فشلت في المنع الكامل لنمو الطفيل، ولم تظهر أثراً مميتاً على نمو الطفيل إلا بعد 48 ساعة. كما أن جميع العقاقير ثبطتت وبشكل ملحوظ حركة الطفيل. وأظهر استخدام القمح الجرثومي الملزن، وبذور الحبة السوداء نتائج واعدة في علاج داء الدويبات الشعرية، مما يشير إلى أهمية العلاجات العشبية الطبيعية.
  • Source
    • "Thus, the cells were harvested and cellular pellets were resuspended in Milli-Q water overnight at 4 °C in sterile conditions. After lysis, cysts were stained with trypan blue 0.4% to improve classification (Meng et al., 1996), counted and the percentage of type I and type II was then determined, as will be described in light microscopy section, below. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The protozoon Giardia lamblia infects millions of people worldwide, most of them in underdeveloped countries, where it is frequently a hyperendemic disease. The search for an effective anti-Giardia treatment has been intense, but recurrent infections, virulence factors, and drug resistance imposed obstacles in the achievement of an efficient medication. Most papers about drug effects in Giardia are related to the trophozoite form, although viable cysts, the infective forms, are continuously eliminated in the stools during the treatment. Supported by this knowledge, we analyzed the inhibitory effects of metronidazole (MZ) and furazolidone (FZ) on the differentiation of Giardia into cysts and its viability. The presence of cavities, lamellar bodies and thread-like structures were the most frequent morphological alterations. The results showed also that FZ was more effective by 50% than MZ in inhibiting in vitro cyst differentiation.
    Experimental Parasitology 08/2006; 113(3):135-41. DOI:10.1016/j.exppara.2005.12.009 · 1.86 Impact Factor
Show more

Preview

Download
2 Downloads
Available from