Abstract:Human cytomegalovirus (HCMV) is popularly prevalent and extremely harmful, which has seriously hindered the researches on its pathogenic mechanism, drugs and vaccines, owing to restriction of species specificity and lacking animal models. In this study, we have explored the death of primary dermal fibroblasts (TSDF) isolated from the Chinese tree shrew (Tupaia belangeri) that infected with HCMV-Towne. The cytopathic effect and cellular death after infection were observed, and cell viability was measured using CCK (cell counting kit). The differences in transcriptional levels of apoptosis-related factor genes bax, bcl-2, and an unfolded protein response (UPR) relevant factor genes chop, atf4, xbp1s were detected using qRT-PCR. Western blot was also used to detect principal viral proteins IE1 and UL44 as well as apoptosis-related factors including Bax, Caspase-9, Caspase-3, and PARP. Additionally, apoptosis was detected by AV-PI double staining. The results showed that the cytopathic effect and cellular death gradually worsen as the infection progressed (Fig.1 a?e), accompanying with significant decrease of cell viability (Fig. 2c, P < 0.001). Moreover infection caused up-regulation of the transcription levels of bax, bcl-2, chop, atf4, xbp1s, and the bax and bcl-2 transcription levels showed a significant antagonistic trend (Fig. 3). Meanwhile, protein expression and progressive activation of Bax, Caspase-9, Caspase-3, and PARP were also up-regulated. Nevertheless viral proteins IE1 and UL44 were up-regulatied to the end of a complete virus replication cycle (Fig. 4). In summary, our study indicates that HCMV can induce apoptosis through cross-species infecting the tree shrew primary dermal fibroblasts, which is closely related to endoplasmic reticulum and mitochondria.