[Effects of acute and chronic murine cytomegalovirus infections on the ratio of regulatory T cells and expression of Th1/Th2 transcription factors T-bet/GATA-3].
OBJECTIVE
To explore the effects of acute and chronic murine cytomegalovirus (MCMV) infections on the regulatory T cells (Treg) ratio and protein expression of the Th1/Th2 transcription factors T-bet/GATA-3.


METHODS
120 BALB/c mice were randomly divided into 2 equal groups: MCMV-infected group undergoing infra-peritoneal injection of homogenate of salivary gland containing MCMV, and mock infection group undergoing infra-peritoneal injection of normal homogenate of salivary gland 1, 3, 7, 14, 28, 45, 60, 75, 90, and 120 days after infection 6 mice from each group were killed to examine the viral load of the heart, lung, liver, and kidney by plaque assay to access the status of MCMV infection. Suspension of splenocytes was prepared. The proportion of CD4+CD25+Foxp3+Treg in the splenocytes was measured by flow cytometry. Western blotting was used to detect the protein expression of T-bet/GATA-3.


RESULTS
The cutoff point between acute and chronic points was the 28th day. The CD4+CD25+Foxp3+Treg proportion in splenocytes significantly decreased during the acute infection stage and to the lowest level of (1.46+/-0.27)% at day 28, significantly lower than that of the mock infection group [(2.78+/-0.29)%, P<0.05]; then obviously increased in the chronic infection stage, increased to (4.51+/-0.24)% at day 60, significantly higher than that of the mock infection group [(2.69+/-0.12)%, P<0.05], and continued to increase still. The protein level (K value) of T-bet of the MCMV infection group peaked to the level of (0.618+/-0.053) on day 3, obviously higher than that of the mock infected group [(0.205+/-0.026)], then decreased to the level similar to that of the mock infection group on day 28, and was obviously lower than that of the mock infection group on day 75. Whereas the protein level of GATA-3 of the MCMV group increased to (0.836+/-0.061) on day 3, markedly higher than that of the mock infection group (0.398+/-0.022), peaked on day 7, then gradually decreased, and remained at the levels similar to those of the mock infection group from day 75 to day 120.


CONCLUSIONS
In the acute infection stage, MCMV up-regulates the T-bet and GATA-3 protein expression. But during the chronic infection stage, MCMV induces a marked proliferation and activation of Treg cells which further inhibit the Th1 and Th2 reactions, especially Th1 response. Treg proliferation may be an important mechanism of chronic and persistent CMV infection in the host.
Li
Ya-nan
YN
Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Zhou
Yu-feng
YF
Shu
Sai-nan
SN
Zhu
Dan-dan
DD
Yang
Zhu-feng
ZF
Fang
Feng
F
D000208:Acute Disease; D000818:Animals; D002454:Cell Differentiation; D002908:Chronic Disease; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D050990:GATA3 Transcription Factor / Q000378:metabolism*; D006566:Herpesviridae Infections / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D018146:Muromegalovirus / Q000472:pathogenicity; D013154:Spleen / Q000166:cytology; D020825:T-Box Domain Proteins / Q000378:metabolism*; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000378:metabolism*; D018417:Th1 Cells / Q000378:metabolism; D018418:Th2 Cells / Q000378:metabolism; D000098815:T-bet Transcription Factor
D050990:GATA3 Transcription Factor; C494748:Gata3 protein, mouse; D020825:T-Box Domain Proteins; D000098815:T-bet Transcription Factor