Comparative studies of macrophage-biased responses in mice to infection with Toxoplasma gondii ToxoDB #9 strains of different virulence isolated from China.
BACKGROUND
Different from three clonal lineages of Toxoplasma gondii in North America and Europe, the genotype China 1 is predominantly prevalent in China. However, there are different virulent isolates within China 1, such as virulent TgCtwh3 and avirulent TgCtwh6, and little is known about differences in macrophage activation between them. The objective of this study focused on cytokine production, phenotype and markers of activated macrophages, and correlated signaling pathway induced by the two isolates.


METHODS
Adherent peritoneal macrophages (termed Wh3-Mφ and Wh6-Mφ, respectively) harvested from infected mice were cultured for detection of Nitric Oxide and arginase activity, and activated markers on Wh3-Mφ/Wh6-Mφ were determined by flow cytometry. In in vitro experiments, the levels of IL-12p40 and TNF-α were measured using ELISA kits, and mRNA expressions of IL-12p40, TNF-α, iNOS, Arg-1 and Ym1 were assayed by real-time PCR. To confirm the activation state of NF-kB p65 in infected cells stained by IF, protein levels of iNOS, Arg-1, Ym1, nuclear NF-κB p65, and phosphorylation of STAT6/STAT3/IκBα were evaluated by Western Blotting. A one-way ANOVA test was used to compare differences among multiple groups.


RESULTS
The result revealed that contrary to the virulent TgCtwh3, the less virulent TgCtwh6 isolate induced a significant increase in IL-12p40 and TNF-α. Although both isolates down-regulated CD80, CD86 and MHCII molecule expression on macrophages, TgCtwh3 promoted up-regulation of PD-L2 and CD206. Wh6-Mφ generated a high level of NO whereas Wh3-Mφ up-regulated Ym1 and arginase expression at transcriptional and protein levels. In terms of signaling pathway, TgCtwh3 induced phospho-STAT6, conversely, TgCtWh6 led to NF-κB p65 activation.


CONCLUSIONS
The virulent TgCtwh3 isolate induced macrophages to polarize toward alternatively activated cells with STAT6 phosphorylation, whereas the less virulent TgCtwh6 elicited the development of classically activated macrophages with nuclear translocation of NF-κB p65. This discrepancy suggests that it is necessary to thoroughly analyze the genotype of TgCtwh3 and TgCtwh6, and to further study other effector molecules that contribute to the macrophage polarization in T. gondii.
Ai-Mei
AM
Zhang
Qian
Q
Shen
Min
M
Li
Xiu-Cai
XC
Xu
He
H
Chen
Yi-Hong
YH
Cai
Qing-Li
QL
Luo
De-Yong
DY
Chu
Li
L
Yu
Jian
J
Du
Zhao-Rong
ZR
Lun
Yong
Y
Wang
Anhui Provincial Laboratories of Pathogen Biology and Zoonoses, Department of Microbiology and Parasitology, Anhui Medical University, Hefei, Anhui, China. qsha2@yahoo.com.
Quan
Q
Sha
Ji-Long
JL
Shen
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002681:China; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D016130:Immunophenotyping; D008262:Macrophage Activation; D017737:Macrophages, Peritoneal / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification / Q000472:pathogenicity*; D014124:Toxoplasmosis, Animal / Q000276:immunology*; D014774:Virulence
D016207:Cytokines