• Parasites, Hosts and Diseases
• /
• 제56권1호
• /
• pp.1-9
• /
• 2018

Giardia lamblia, an anaerobic, amitochondriate protozoan parasite causes parasitic infection giardiasis in children and young adults. It produces pyruvate, a major metabolic product for its fermentative metabolism. The current study was undertaken to explore the effects of pyruvate as a physiological antioxidant during oxidative stress in Giardia by cysteine-ascorbate deprivation and further investigation upon the hypothesis that oxidative stress due to metabolism was the reason behind the cytotoxicity. We have estimated intracellular reactive oxygen species generation due to cysteine-ascorbate deprivation in Giardia. In the present study, we have examined the effects of extracellular addition of pyruvate, during oxidative stress generated from cysteine-ascorbate deprivation in culture media on DNA damage in Giardia. The intracellular pyruvate concentrations at several time points were measured in the trophozoites during stress. Trophozoites viability under cysteine-ascorbate deprived (CAD) medium in presence and absence of extracellular pyruvate has also been measured. The exogenous addition of a physiologically relevant concentration of pyruvate to trophozoites suspension was shown to attenuate the rate of ROS generation. We have demonstrated that Giardia protects itself from destructive consequences of ROS by maintaining the intracellular pyruvate concentration. Pyruvate recovers Giardia trophozoites from oxidative stress by decreasing the number of DNA breaks that might favor DNA repair.

• Parasites, Hosts and Diseases
• /
• 제49권4호
• /
• pp.349-356
• /
• 2011

The existence of symbiotic relationships between Acanthamoeba and a variety of bacteria is well-documented. However, the ability of Acanthamoeba interacting with host bacterial pathogens has gained particular attention. Here, to understand the interactions of Escherichia coli K1 and E. coli K5 strains with Acanthamoeba castellanii trophozoites and cysts, association assay, invasion assay, survival assay, and the measurement of bacterial numbers from cysts were performed, and nonpathogenic E. coli K12 was also applied. The association ratio of E. coli K1 with A. castellanii was 4.3 cfu per amoeba for 1 hr but E. coli K5 with A. castellanii was 1 cfu per amoeba for 1 hr. By invasion and survival assays, E. coli K5 was recovered less than E. coli K1 but still alive inside A. castellanii. E. coli K1 and K5 survived and multiplied intracellularly in A. castellanii. The survival assay was performed under a favourable condition for 22 hr and 43 hr with the encystment of A. castellanii. Under the favourable condition for the transformation of trophozoites into cysts, E. coli K5 multiplied significantly. Moreover, the pathogenic potential of E. coli K1 from A. castellanii cysts exhibited no changes as compared with E. coli K1 from A. castellanii trophozoites. E. coli K5 was multiplied in A. castellanii trophozoites and survived in A. castellanii cysts. Therefore, this study suggests that E. coli K5 can use A. castellanii as a reservoir host or a vector for the bacterial transmission.

• Parasites, Hosts and Diseases
• /
• 제42권1호
• /
• pp.35-40
• /
• 2004

The nfa 1 gene was cloned from a cDNA library of pathogenic Naegleria fowleri by immunoscreening; it consisted of 360 bp and produced a 13.1 kDa recombinant protein (rNfa1) that showed the pseudopodia-specific localization by immunocytochemistry in the previous study. Based on the idea that the pseudopodia-specific Nfa1 protein mentioned above seems to be involved in the pathogenicity of N. fowleri, we observed the effect of an anti-Nfa1 antibody on the proliferation of N. fowleri trophozoites and the cytotoxicity of N. fowleri trophozoites on the target cells. The proliferation of N. fowleri trophozoites was inhibited after being treated with an anti-Nfa1 polycional antibody in a dose-dependent manner for 48 hrs. By a light microscope, CHO cells co-cultured with N. fowleri trophozoites (group I) for 48 hrs showed severe morphological destruction. On the contrary, CHO cells co-cultured with N. fowleri trophozoites and anti-Nfa1 polyclonal antibody (1:100 dilution) (group II) showed less destruction. In the LDH release assay results, group I showed 50.6% cytotoxicity, and group II showed 39.3%. Consequently, addition of an anti-Nfa1 polyclonal antibody produced a decreasing effect of in vitro cytotoxicity of N. fowleri in a dose-dependent manner.

• Parasites, Hosts and Diseases
• /
• 제46권4호
• /
• pp.217-221
• /
• 2008

Free-living Naegleria fowleri leads to a fatal infection known as primary amebic meningoencephalitis in humans. Previously, the target cell death could be induced by phagocytic activity of N. fowleri as a contact-dependent mechanism. However, in this study we investigated the target cell death under a non-contact system using a tissue-culture insert. The human microglial cells, U87MG cells, co-cultured with N. fowleri trophozoites for 30 min in a non-contact system showed morphological changes such as the cell membrane destruction and a reduction in the number. By fluorescence-activated cell sorter (FACS) analysis, U87MG cells co-cultured with N. fowleri trophozoites in a non-contact system showed a significant increase of apoptotic cells (16%) in comparison with that of the control or N. fowleri lysate. When U87MG cells were co-cultured with N. fowleri trophozoites in a non-contact system for 30 min, 2 hr, and 4 hr, the cytotoxicity of amebae against target cells was 40.5, 44.2, and 45.6%, respectively. By contrast, the cytotoxicity of non-pathogenic N. gruberi trophozoites was 10.2, 12.4, and 13.2%, respectively. These results suggest that the molecules released from N. fowleri in a contact-independent manner as well as phagocytosis in a contact-dependent manner may induce the host cell death.

• Parasites, Hosts and Diseases
• /
• 제23권2호
• /
• pp.293-299
• /
• 1985

병원성 자유생활 아메바인 Naegleria fowleri를 CGVS 배지에서 무균적으로 배양하여 그 영향형을 복강내로 주입하여 인위적으로 면역시킨 마우스에 본 원충율 비강내로 감염시켰을때 방어면역이 생성되는지를 관찰하였다. 감염 8일후부터 마우스가 사망하기 시작하였고 이 마우스의 뇌에서 전형적인 원발성 아메바성 뇌수막염이 발생했음을 관찰할 수 있었다. N. fowleri 감염으로 인한 마우스의 사망율은 대조군에서 보다 네가지 항원으로 면역시킨 실험군에서 모두 현저히 낮았으며, 감염에서 사망할 때까지의 생존기간도 면역시킨 실험군에서 대조군보다 연장되었으나, N. fowleri 세포막항원으로 면역시킨 실험군에서는 대조군과 비교할때 차이가 없었다. 또한 N. gruberi 영양형으로 면역시킨 실험군에서도 생존기간이 연장되었다. 이상의 성적을 요약하면 N. fowleri를 마우스 복강내로 주입시켜 면역시킬 때 방어면역이 생성됨을 알 수 있었다.

• Parasites, Hosts and Diseases
• /
• 제55권2호
• /
• pp.115-120
• /
• 2017

Encystation mediating cyst specific cysteine proteinase (CSCP) of Acanthamoeba castellanii is expressed remarkably during encystation. However, the molecular mechanism involved in the regulation of CSCP gene expression remains unclear. In this study, we focused on epigenetic regulation of gene expression during encystation of Acanthamoeba. To evaluate methylation as a potential mechanism involved in the regulation of CSCP expression, we first investigated the correlation between promoter methylation status of CSCP gene and its expression. A 2,878 bp of promoter sequence of CSCP gene was amplified by PCR. Three CpG islands (island 1-3) were detected in this sequence using bioinformatics tools. Methylation of CpG island in trophozoites and cysts was measured by bisulfite sequence PCR. CSCP promoter methylation of CpG island 1 (1,633 bp) was found in 8.2% of trophozoites and 7.3% of cysts. Methylation of CpG island 2 (625 bp) was observed in 4.2% of trophozoites and 5.8% of cysts. Methylation of CpG island 3 (367 bp) in trophozoites and cysts was both 3.6%. These results suggest that DNA methylation system is present in CSCP gene expression of Acanthamoeba. In addition, the expression of encystation mediating CSCP is correlated with promoter CpG island 1 hypomethylation.

• Parasites, Hosts and Diseases
• /
• 제49권4호
• /
• pp.341-347
• /
• 2011

Acanthamoeba infection is difficult to treat because of the resistance property of Acanthamoeba cyst against the host immune system, diverse antibiotics, and therapeutic agents. To identify encystation mediating factors of Acanthamoeba, we compared the transcription profile between cysts and trophozoites using microarray analysis. The DNA chip was composed of 12,544 genes based on expressed sequence tag (EST) from an Acanthamoeba ESTs database (DB) constructed in our laboratory, genetic information of Acanthamoeba from TBest DB, and all of Acanthamoeba related genes registered in the NCBI. Microarray analysis indicated that 701 genes showed higher expression than 2 folds in cysts than in trophozoites, and 859 genes were less expressed in cysts than in trophozoites. The results of real-time PCR analysis of randomly selected 9 genes of which expression was increased during cyst formation were coincided well with the microarray results. Eukaryotic orthologous groups (KOG) analysis showed an increment in T article (signal transduction mechanisms) and O article (posttranslational modification, protein turnover, and chaperones) whereas significant decrement of C article (energy production and conversion) during cyst formation. Especially, cystein proteinases showed high expression changes (282 folds) with significant increases in real-time PCR, suggesting a pivotal role of this proteinase in the cyst formation of Acanthamoeba. The present study provides important clues for the identification and characterization of encystation mediating factors of Acanthamoeba.

• Parasites, Hosts and Diseases
• /
• 제57권3호
• /
• pp.217-223
• /
• 2019

Acanthamoeba castellanii has ubiquitous distribution and causes primary acanthamoebic keratitis (AK). AK is a common disease in contact lens wearers and results in permanent visual impairment or blindness. In this study, we observed the cytopathic effect, in vitro cytotoxicity, and secretion pattern of cytokines in human corneal epithelial cells (HCECs) induced by A. castellanii trophozoites and/or cysts. Morphological observation revealed that panked dendritic HCECs co-cultured with amoeba cysts had changed into round shape and gradually died. Such changes were more severe in co-culture with cyst than those of co-cultivation with trophozoites. In vitro cytotoxicity assay revealed the highest cytotoxicity to HCECs in the co-culture system with amoeba cysts. A. castellanii induced the expression of $IL-1{\alpha}$, IL-6, IL-8, and CXCL1 in HCECs. Secreted levels of $IL-1{\alpha}$, IL-6, and IL-8 in HCECs co-cultured with both trophozoites and cysts were increased at an early incubation time (3 and 6 hr). These results suggested that cytopathic changes and pro-inflammatory cytokines release of HCECs in response to A. castellanii, especially amoebic cysts, are an important mechanism for AK development.

• Parasites, Hosts and Diseases
• /
• 제31권3호
• /
• pp.249-258
• /
• 1993

원발성 아메바성 수막뇌염을 야기하는 Naegleria fowleri를 사망율에 따라 $1{\;}{\times}{\;}10^4$개 아메바 영양형 접종군과. $1{\;}{\times}{\;}10^5$개 아메바 영양형 접종군으로 나누어 비장세포를 비특이 mitogen인 Phytohemagglutinin(PHA)과 특이항원인 N. fowleri Iysates로 자극하여 T 세포의 interleukin-2 생성정도를 측정하고 T 림프구의 아형 및 아세포화정도를 측정한 결과 N.fowleri 아메바 영양형 $1{\;}{\times}{\;}10^5$개 접종군에서의 마우스 사망율은 72.2%였으며 $1{\;}{\times}{\;}10^4$개 접종군에서의 마우스 사망율은 14.3%였다. 또한 IL릭 생성정도를 접종후 7, 14, 24일째 측정한 결과. 접종 후 14일째에는 두 실험군 모두에서 대조군과 비교하여 IL닉의 생성이 유의하게 감소하였으며 접종 후 24일째에는 두 실험군 모두에서 접종 후 14일째 보다는 증가하였으나 대조군과 비교하여 유의하게 억제되었다 비장세포내 T 림프구 아형의 변동은 전체 비장 림프구에 대한 $Thy-1.2^{+}{\;}T.{\;}L3T4^{+}{\;}T,{\;}Ly^{2+}{\;}T$ 세포는 N.fowleri아메바 영양형 $1{\;}{\times}{\;}10^5$개 접종군에서 접종 후 7일째 대조군과 비교하여 유의하게 증가하였고 접종 후 14일째와 24일째에는 대조군과 비교하여 유의한 차이가 없었다. 아메바 영양형 $1{\;}{\times}{\;}10^4$개를 접종시킨 실험군은 경과 일수에 관계없이 대조군과 비교하여 유의한 차이가 없었다. 비장세포내 T 세포의 DNA의 분획을 관찰한 결과 두 실험군 모두에서 접종 후 7일째에 S phase 분획이 가장 높이 증가하였으며 접종 후 14일과 24일째에도 대조군에 비하여는 유의하게 증가하여 있었다. 이상의 결과를 종합하여 볼 때, N.fowleri를 사망율을 기준으로 접종량을 달리하여 아메바 영양형 $1{\;}{\times}{\;}10^4$개 접종군과 $1{\;}{\times}{\;}10^5$개 접종군으로 나누어 접종하였을 때, 접종 후 7일을 전후하여 IL-2를 매개로 활성화되는 세포매개성 면역이 N.fowleri감염의 방어기작으로 작용하는 것으로 생각되며 아메바 접종 후 14일째에는 치명적인 수막뇌염으로 진행되어 비장세포의 IL-2의 생성능력이 매우 억제된 것으로 생각된다. 또한 IL-2 생성능력과 T 세포의 아세포화의 증가 및 T세포 아령의 수의 변동과는 잘 일치되지 않는 것으로 나타났다.

• Parasites, Hosts and Diseases
• /
• 제54권4호
• /
• pp.461-469
• /
• 2016

Giardia lamblia is a protozoan that causes diarrheal diseases in humans. Cytoskeletal structures of Giardia trophozoites must be finely reorganized during cell division. To identify Giardia proteins which interact with microtubules (MTs), Giardia lysates were incubated with in vitro-polymerized MTs and then precipitated by ultracentifugation. A hypothetical protein (GL50803_8405) was identified in the precipitated fraction with polymerized MTs and was named GlMBP1 (G. lamblia microtubule-binding protein 1). Interaction of GlMBP1 with MTs was confirmed by MT binding assays using recombinant GlMBP1 (rGlMBP1). In vivo expression of GlMBP1 was shown by a real-time PCR and western blot analysis using anti-rGlMBP1 antibodies. Transgenic G. lamblia trophozoites were constructed by integrating a chimeric gene encoding hemagglutinin (HA)-tagged GlMBP1 into a Giardia chromosome. Immunofluorescence assays of this transgenic G. lamblia, using anti-HA antibodies, revealed that GlMBP1 mainly localized at the basal bodies, axonemes, and median bodies of G. lamblia trophozoites. This result indicates that GlMBP1 is a component of the G. lamblia cytoskeleton.