Abstract: OBJECTIVE To observe the influence of human cytomegalovirus（HCMV） infection on expression of Toll-like receptor 3（TLR3） in peripheral blood mononuclear cells（PBMC） and insulin resistance in the type 2 diabetes mellitus（T2 DM） patients.METHODS A total of 105 T2 DM patients who were treated in Wuhan Puren Hospital were assigned as the T2 DM group and were divided into the mild group, the moderate group and the severe group according to the level of glycated hemoglobin（HbA1 c）, and the patients were divided into the HCMV-DNA-positive group and the HCMV-DNA-negative group according the result of HCMV-DNA test. Meanwhile, 50 healthy people who received physical examination were set as the control group. The HCMV-DNA load, PBMC TLR3, nuclear factor κB（NF-κB）, inflammation-related microRNA-155（miR-155）, fasting plasma glucose（FPG）, fasting insulin（FINS）, homeostasis model assessment of insulin resistance（HOMA-IR） and T lymphocyte subsets（CD₄⁺, CD₈⁺, CD₄⁺/CD₈⁺） were detected for all of the patients.RESULTS The HCMV-DNA load and positive rate of HCMV-DNA were significantly higher in the T2 DM group than in the control group（P＜0.05）. The HCMV-DNA load and positive rate of HCMV-DNA were significantly higher in the severe group than in the mild group and the moderate group（P＜0.05）, and HCMV-DNA load and positive rate of HCMV-DNA were significantly higher in the moderate group than in the mild group（P＜0.05）. The relative expression levels of TLR3 and NF-κB mRNA, miR-155 of the HCMV-DNA-positive group and the HCMV-DNA-negative group were significantly higher than those of the control group（P＜0.05）; the relative expression levels of TLR3 and NF-κB mRNA, miR-155 of HCMV-DNA-positive group were significantly higher than those of the HCMV-DNA-negative group（P＜0.05）. The levels of HbA1 c, FPG, HOMA-IR and CD₈⁺ of the HCMV-DNA-positive group and the HCMV-DNA-negative group were significantly higher than those of the control group（P＜0.05）; the levels of HbA1 c, FPG, HOMA-IR and CD₈⁺ of the HCMV-DNA-positive group were higher than those of the HCMV-DNA-negative group（P＜0.05）. The levels of FINS, CD₄⁺ and CD₄⁺/CD₈⁺ of the HCMV-DNA-positive group and the HCMV-DNA-negative group were significantly lower than those of the control group（P＜0.05）; the levels of FINS, CD₄⁺ and CD₄⁺/CD₈⁺ of the HCMV-DNA-positive group were significantly lower than those of the HCMV-DNA-negative group（P＜0.05）.CONCLUSION The T2 DM patients are high risk of HCMV infection, which may aggravate the inflammatory response by activating the TLR3 signal pathway, lead to the immune response, raise the insulin resistance and exacerbate the illness condition.