| Jong-Hyun Kim | 6 Articles |
Naegleria fowleri, a brain-eating amoeba, thrives in lakes and rivers with aquatic vegetation and causes primary amoebic meningoencephalitis (PAM) in humans. Most recently, it has become such a serious problem that N. fowleri was detected in tap water in Houston, USA. Several pathogenic factors are considered very important to destroy target cells in the brain. In particular, the food-cup where N. fowleri antigen-1 (Nfa1) is located, is strongly expressed in pseudopodia involved in the movement of N. fowleri, and is involved in phagocytosis by attaching to target cells. In this article, we reviewed the role of the Nfa1 protein and its associated pathogenicity. The nfa1 gene was cloned by cDNA library immunoscreening using infection serum and immune serum. Nfa1 protein is mainly distributed in pseudopodia important to movement and vacuoles. Moreover, heat shock protein 70, cathepsin-like proteare and Nf-actin are also associated with pseudopodia in which Nfa1 is localized. Interestingly, the amount of the nfa1 gene changed as N. fowleri trophozoites transformed into cysts. Polyclonal antiserum against Nfa1 showed a protective effect against cytotoxicity of approximately 19.7%. Nfa1-specific IgA antibodies prevent N. fowleri trophozoites from adhering to the nasal mucosa, delaying invasion. The nfa1-vaccinated mice showed significantly higher levels of Nfa1-specific antibody. The duration of anti-Nfa1 IgG in the vaccinated mice lasted 12 weeks, strongly suggesting that nfa1 is a significant pathogenic gene and that Nfa1 is a pathogenic protein. Several factors related to pseudopodia and locomotion have been linked to Nfa1. A clearer function of N. fowleri targeting nfa1 with other genes might enable target-based inhibition of N. fowleri pathogenicity.
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Acanthamoeba keratitis (AK) is a rare ocular disease, but it is a painful and sight-threatening infectious disease. Early diagnosis and adequate treatment are necessary to prevent serious complications. While AK is frequently diagnosis via several PCR assays or Acanthamoeba-specific antibodies, a more specific and effective diagnostic method is required. This study described the production of a polyclonal peptide antibody against the periplasmic binding protein (PBP) of A. castellanii and investigated its diagnostic potential. Western blot analysis showed that the PBP antibody specifically reacted with the cell lysates of A. castellanii. However, the PBP antibody did not interact with human corneal epithelial (HCE) cells and the other 3 major causative agents of keratitis. Immunocytochemistry (ICC) results revealed the specific detection of A. castellanii trophozoites and cysts by PBP antibodies when A. castellanii were co-cultured with HCE cells. PBP antibody specificity was further confirmed by co-culture of A. castellanii trophozoites with F. solani, S. aureus, and P. aeruginosa via ICC. The PBP antibody specifically reacted with the trophozoites and cysts of A. polyphaga, A. hatchetti, A. culbertsoni, A. royreba, and A. healyi, thus demonstrated its genus-specific nature. These results showed that the PBP polyclonal peptide antibody of A. castellanii could specifically detect several species of Acanthamoeba, contributing to the development of an effective antibody-based AK diagnostics.
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A total of 44 adult or juvenile nutrias were necropsied for disease survey. A large nodule was found in the liver of a nutria. The histopathological specimen of the hepatic nodule was microscopically examined, and sectional worms were found in the bile duct. The worms showed a tegument with spines, highly branches of vitelline glands and intestine. Finally, we histopathologically confirmed fascioliasis in a wild nutria. In the present study, a case of fascioliasis in a wild nutria is first confirmed in Korea.
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Pathogenic Naegleria fowleri, Acanthamoeba castellanii, and Acanthamoeba polyphaga, are distributed worldwide. They are causative agents of primary amoebic meningoencephalitis or acanthamoebic keratitis in humans, respectively. Trophozoites encyst in unfavorable environments, such as exhausted food supply and desiccation. Until recently, the method of N. fowleri encystation used solid non-nutrient agar medium supplemented with heat-inactivated Escherichia coli; however, for the amoebic encystment of Acanthamoeba spp., a defined, slightly modified liquid media is used. In this study, in order to generate pure N. fowleri cysts, a liquid encystment medium (buffer 1) modified from Page’s amoeba saline was applied for encystation of N. fowleri. N. fowleri cysts were well induced after 24 hr with the above defined liquid encystment medium (buffer 1). This was confirmed by observation of a high expression of differential mRNA of nfa1 and actin genes in trophozoites. Thus, this liquid medium can replace the earlier non-nutrient agar medium for obtaining pure N. fowleri cysts. In addition, for cyst formation of Acanthamoeba spp., buffer 2 (adjusted to pH 9.0) was the more efficient medium. To summarize, these liquid encystment media may be useful for further studies which require axenic and pure amoebic cysts.
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