Li Ya-nan, Zhou Yu-feng, Shu Sai-nan, Zhu Dan-dan, Yang Zhu-feng, Fang Feng
Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Zhonghua Yi Xue Za Zhi. 2008 Nov 18;88(42):2999-3002.
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.
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.
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.
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.
探讨急性和慢性小鼠巨细胞病毒（MCMV）感染对调节性T细胞（Treg）比例以及Th1/Th2转录因子T-bet/GATA-3蛋白表达的影响。
将120只BALB/c小鼠随机分为两组，每组60只：MCMV感染组经腹腔注射含MCMV的唾液腺匀浆， mock感染组经腹腔注射正常唾液腺匀浆。在感染后1、3、7、14、28、45、60、75、90和120天，每组处死6只小鼠，通过空斑试验检测心脏、肺、肝和肾的病毒载量，以了解MCMV感染状况。制备脾细胞悬液，采用流式细胞术检测脾细胞中CD4+CD25+Foxp3+Treg的比例，采用蛋白质印迹法检测T-bet/GATA-3的蛋白表达。
急性和慢性感染的分界点为第28天。在急性感染阶段，脾细胞中CD4+CD25+Foxp3+Treg比例显著降低，在第28天降至最低水平（1.46±0.27）%，显著低于mock感染组[（2.78±0.29）%，P<0.05]；随后在慢性感染阶段明显升高，在第60天升至（4.51±0.24）%，显著高于mock感染组[（2.69±0.12）%，P<0.05]，并持续升高。MCMV感染组T-bet蛋白水平（K值）在第3天达到峰值（0.618±0.053），明显高于mock感染组[（0.205±0.026）]，然后在第28天降至与mock感染组相似的水平，在第75天明显低于mock感染组。而MCMV组GATA-3蛋白水平在第3天升至（0.836±0.061），明显高于mock感染组（0.398±0.022），在第7天达到峰值，然后逐渐下降，从第75天到第120天维持在与mock感染组相似的水平。
在急性感染阶段，MCMV上调T-bet和GATA-3蛋白表达。但在慢性感染阶段，MCMV诱导Treg细胞显著增殖和活化，进而抑制Th1和Th2反应，尤其是Th1反应。Treg增殖可能是宿主慢性持续性CMV感染的重要机制。
