Cytopathic changes and pro-inflammatory cytokines induced by Naegleria fowleri trophozoites in rat microglial cells and protective effects of an anti-Nfa1 antibody.
Naegleria fowleri, a free-living amoeba, causes fatal primary amoebic meningoencephalitis in experimental animals and humans. The nfa1 gene (360 bp) was previously cloned from a cDNA library of pathogenic N. fowleri by immunoscreening, and produced a 13.1-kDa recombinant protein that showed pseudopodia-specific localization by immunocytochemistry. On the basis of an idea that the pseudopodia-specific Nfa1 protein seems to be involved in the pathogenicity of N. fowleri, the cytopathic activity of N. fowleri trophozoites co-cultured with rat microglial cells was observed, and the effects of an anti-Nfa1 antibody in a co-culture system were elucidated. Using light, scanning and transmission electron microscopy, it was seen that N. fowleri trophozoites in contact with microglial cells produced vigorous pseudopodia and a food-cup structure. Microglial cells were destroyed by N. fowleri trophozoites as seen from necrotic cell death in a time-dependent manner. In a(51)Cr release assay, N. fowleri showed 17.8%, 24.9%, 54.6% and 98% cytotoxicity against microglial cells at 3, 6, 12 and 24 h post-incubation, respectively. However, when anti-Nfa1 antibody was added in a coculture system, N. fowleri cytotoxicity was reduced to 15.5%, 20.3%, 46.7% and 66.9%, respectively. Moreover, microglial cells co-cultured with N. fowleri trophozoites secreted the pro-inflammatory cytokines, TNF-alpha, IL-1beta and IL-6. In the presence of anti-Nfa1 antibody, the secretion of TNF-alpha was slightly, but not significantly, decreased.
Oh
Y-H
YH
Department of Microbiology, Institute for Medical Science, Ajou University School of Medicine, Suwon, Korea.
Jeong
S-R
SR
Kim
J-H
JH
Song
K-J
KJ
Kim
K
K
Park
S
S
Sohn
S
S
Shin
H-J
HJ
D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D000953:Antigens, Protozoan / Q000276:immunology* / Q000502:physiology; D016923:Cell Death; D002478:Cells, Cultured; D016207:Cytokines / Q000032:analysis*; D005260:Female; D007375:Interleukin-1 / Q000032:analysis; D015850:Interleukin-6 / Q000032:analysis; D017628:Microglia / Q000166:cytology / Q000276:immunology* / Q000469:parasitology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D016848:Naegleria fowleri / Q000276:immunology* / Q000472:pathogenicity*; D015800:Protozoan Proteins / Q000276:immunology* / Q000502:physiology; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; C460560:Nfa1 protein, Naegleria fowleri; D015800:Protozoan Proteins; D014409:Tumor Necrosis Factor-alpha